A method and system for determining fluid cross-sectional flow velocity distribution

Abstract

The application discloses a kind of fluid section flow velocity distribution determination method and system, it is related to pipeline fluid monitoring technical field, the method comprises: obtaining the liquid level information corresponding to the target section of fluid, fluid temperature;Continuous ultrasonic signal is sent to target section, and the weight flow rate of target section is determined based on returned continuous echo signal;Determine the flow measurement mode corresponding to the layer flow rate of the multiple flow rate layers of target section based on liquid level information;Determine the layer flow rate corresponding to the multiple flow rate layers of target section based on flow measurement mode;Based on the layer flow rate corresponding to the multiple flow rate layers, the initial flow velocity distribution of target section is constructed;The initial flow velocity distribution is corrected based on weight flow rate, and the flow velocity distribution of target section is obtained.Therefore, it has the advantages that the flow velocity spatial distribution of fluid section can be accurately determined, the measurement demand under different liquid level conditions is adapted, and the problems of inaccurate measurement, incompleteness and poor adaptability in traditional technology are solved.

Description

Technical Field

[0001] This application relates to the field of pipeline fluid monitoring technology, and in particular to a method and system for determining the velocity distribution of a fluid cross section. Background Technology

[0002] Pipeline fluid velocity monitoring is a core foundation for flow accounting, pipeline operation and maintenance, and pollution source tracing. Current technologies have significant limitations: First, poor flow field adaptability. Traditional single-point velocity meters can only measure the velocity at a fixed point in the pipeline, failing to reflect the spatial distribution characteristics of non-uniform flow fields (such as velocity differences between the pipeline center and edge, and velocity stratification in shallow flow conditions), leading to large errors in average velocity estimation (typically ≥15%). Second, limited measurement accuracy. Single ultrasonic Doppler technology is easily affected by the concentration of suspended particles and turbulent flow patterns within the pipeline, resulting in insufficient resolution at low velocities (≤0.1 m / s). Manual parameter adjustment is required when switching between full and partial pipe conditions. Third, weak data correlation. Existing equipment lacks a global calibration mechanism, resulting in large dispersion of stratified measurement data and an inability to form complete and reliable cross-sectional flow field data. Fourth, significant flow field interference. Inadequate structural design of the monitoring probe and support rod can easily generate eddies after fluid intervention, causing actual measurements to deviate from the true flow pattern.

[0003] Some studies have attempted to use multi-probe array measurements, but these methods suffer from large equipment size, high deployment costs, and severe signal interference between probes. Other technologies use a single continuous wave mode to measure average flow velocity, but fail to capture flow field details, making it difficult to meet the requirements for precise monitoring of non-uniform flow fields. Therefore, there is an urgent need to develop a pipeline flow velocity monitoring system that combines "layered detail capture" with "global accuracy calibration" capabilities to solve the core problems of traditional technologies: inaccuracy, incompleteness, and poor adaptability. Summary of the Invention

[0004] In view of this, embodiments of this application provide a method and system for determining the velocity distribution of a fluid cross section.

[0005] According to a first aspect of this application, embodiments of this application provide a method for determining the velocity distribution of a fluid cross-section, including: Acquire the liquid level and fluid temperature corresponding to the target cross-section of the fluid; Continuous ultrasonic signals are sent to the target section, and the weighted flow velocity of the target section is determined based on the returned continuous echo signals. The flow measurement method corresponding to the pulse ultrasonic signal is determined based on the liquid level information. The flow measurement methods include staggered periodic wave emission flow measurement method and continuous periodic wave emission combined with phase correlation flow measurement method. If the flow measurement method is the staggered periodic wave measurement method, the staggered period is determined based on the liquid level information, fluid temperature and weighted flow velocity. Based on the staggered period, a pulsed ultrasonic signal is sent to the target section, and the laminar flow velocity corresponding to multiple flow velocity layers of the target section is determined based on the returned first pulse echo signal and fluid temperature. If the flow measurement method is a combination of continuous periodic wave emission and phase correlation, the first pulse interval time within the continuous period and the second pulse interval time between continuous periods are determined based on the liquid level information, fluid temperature and weighted flow velocity; pulse ultrasonic signals are sent to the target section based on the first pulse interval time within the continuous period and the second pulse interval time between continuous periods, and the laminar flow velocity corresponding to multiple flow velocity layers of the target section is determined based on the returned second pulse echo signal and fluid temperature; Based on the laminar velocities corresponding to multiple velocity layers, the initial velocity distribution of the target section is constructed; The initial velocity distribution is corrected based on the weighted velocity to obtain the velocity distribution of the target section.

[0006] Optionally, the weighted flow velocity of the target section is determined based on the returned continuous echo signal, including: The continuous echo signal is converted into a frequency domain signal, and the frequency shift value corresponding to the peak frequency point in the frequency domain signal is extracted. The frequency shift value is accumulated based on the peak frequency point to obtain the cumulative amplitude corresponding to each peak frequency point; Based on the cumulative amplitude, the maximum local velocity point is determined. The maximum local velocity point includes the maximum cumulative amplitude and the corresponding target peak frequency point. The direction of water flow corresponding to the point of maximum local velocity is determined based on the frequency shift value corresponding to the target peak frequency point. Based on the target peak frequency point, cumulative amplitude, and maximum cumulative amplitude, determine the velocity start point and velocity end point corresponding to the maximum local velocity point; Determine the centroid of the velocity corresponding to the point of maximum local velocity based on the starting and ending points of the velocity. The weighted velocity of the target section is determined based on the cumulative amplitude corresponding to the direction of water flow and the centroid of the velocity.

[0007] Optionally, the flow measurement method corresponding to the pulsed ultrasonic signal is determined based on the liquid level information, including: If the liquid level information indicates that the liquid level is less than or equal to the target liquid level, the flow measurement method corresponding to the pulse ultrasonic signal is determined to be the staggered periodic wave measurement method. If the liquid level information indicates that the liquid level is greater than the target liquid level, the flow measurement method corresponding to the pulse ultrasonic signal is determined to be a flow measurement method combining continuous periodic wave emission and phase correlation.

[0008] Optionally, the staggered period is determined based on liquid level information, fluid temperature, and weighted flow rate, including: The propagation speed of pulsed ultrasonic signals in a fluid is determined based on fluid temperature; The interval time of the third pulse is determined based on the liquid level information and the propagation speed; The fourth pulse interval time is determined based on the third pulse interval time, weighted flow velocity, and propagation speed. The interleaved period is obtained based on the third pulse interval and the fourth pulse interval.

[0009] Optionally, the laminar flow velocity corresponding to multiple velocity layers of the target section is determined based on the returned first pulse echo signal and the fluid temperature, including: Based on the first pulse echo signal corresponding to the pulsed ultrasonic signal emitted at the third pulse interval, the first phase angle corresponding to the multiple velocity layers of the target section is determined, and the first fluid velocity corresponding to the multiple velocity layers of the target section is determined based on the first phase angle. Based on the first pulse echo signal corresponding to the pulsed ultrasonic signal emitted at the fourth pulse interval, the second phase angle corresponding to the multiple velocity layers of the target section is determined, and the second fluid velocity corresponding to the multiple velocity layers of the target section is determined based on the second phase angle. For each velocity layer of the target cross section, the laminar velocity of the velocity layer is determined based on the corresponding first fluid velocity, the corresponding second fluid velocity, and the fluid temperature.

[0010] Optionally, the first pulse interval time within a continuous cycle and the second pulse interval time between continuous cycles are determined based on liquid level information, fluid temperature, and weighted flow rate, including: The propagation speed of pulsed ultrasonic signals in a fluid is determined based on fluid temperature; Based on the weighted flow velocity and propagation speed, the interval time of the first pulse in a continuous period is determined. Based on the first pulse interval time, liquid level information, and propagation speed, the second pulse interval time between consecutive cycles is determined.

[0011] Optionally, the laminar flow velocity corresponding to multiple velocity layers of the target section is determined based on the returned second pulse echo signal and fluid temperature, including: Based on the second pulse echo signal corresponding to the pulse ultrasonic signal emitted at the first pulse interval, the third phase angle corresponding to the multiple velocity layers of the target section is determined, and the third fluid velocity corresponding to the multiple velocity layers of the target section is determined based on the third phase angle. Based on the second pulse echo signal corresponding to the pulse ultrasonic signal emitted at the second pulse interval, the fourth phase angle corresponding to the multiple velocity layers of the target section is determined, and the fourth fluid velocity corresponding to the multiple velocity layers of the target section is determined based on the fourth phase angle. For each velocity layer of the target cross section, the laminar velocity of the velocity layer is determined based on the corresponding third fluid velocity, the corresponding fourth fluid velocity, and the fluid temperature.

[0012] Optionally, based on the layer velocities corresponding to multiple velocity layers, an initial velocity distribution for the target cross section is constructed, including: Interpolating the flow velocities corresponding to multiple velocity layers yields the initial velocity distribution of the target cross section. The initial velocity distribution satisfies the following conditions: the velocity of each velocity layer is the corresponding flow velocity, the velocity between adjacent velocity layers is a cubic polynomial, and the second derivative of the initial velocity distribution is continuous.

[0013] Optionally, the initial velocity distribution is corrected based on the weighted velocity to obtain the velocity distribution of the target section, including: The weight of each velocity layer is determined based on the proportion of the cross-sectional area corresponding to each velocity layer. Calculate the weighted average of the initial velocity distribution based on the weights and the initial velocity distribution; The boundary conditions and coefficients of the initial velocity distribution are corrected based on the weighted average value and weighted velocity of the initial velocity distribution to obtain the velocity distribution of the target section; the weighted average value and weighted velocity of the velocity distribution satisfy the consistency condition.

[0014] According to a second aspect of this application, embodiments of this application provide a system for determining the velocity distribution of a fluid cross-section, comprising: A hydrostatic sensor is used to measure the liquid level information corresponding to a target cross-section of a fluid. An ultrasonic Doppler sensor is used to send continuous ultrasonic signals to a target section and receive the returned continuous echo signals; to send pulsed ultrasonic signals to the target section based on an alternating period and receive the returned first pulse echo signal; and to send pulsed ultrasonic signals to the target section based on the first pulse interval time within a continuous period and the second pulse interval time between continuous periods and receive the returned second pulse echo signal. Temperature sensor, used to measure the fluid temperature at a target cross-section; The processor acquires the liquid level and fluid temperature of the target cross-section of the fluid; sends continuous ultrasonic signals to the target cross-section and determines the weighted flow velocity of the target cross-section based on the returned continuous echo signals; determines the flow measurement method corresponding to the pulsed ultrasonic signal based on the liquid level information, including staggered periodic wave emission flow measurement method and a flow measurement method combining continuous periodic wave emission and phase correlation; if the flow measurement method is staggered periodic wave emission flow measurement method, it determines the staggered period based on the liquid level information, fluid temperature, and weighted flow velocity, sends pulsed ultrasonic signals to the target cross-section based on the staggered period, and determines multiple velocity layer pairs of the target cross-section based on the returned first pulse echo signal and fluid temperature. The laminar velocity is determined accordingly. If the flow measurement method is a combination of continuous periodic wave emission and phase correlation, the first pulse interval time within the continuous period and the second pulse interval time between continuous periods are determined based on the liquid level information, fluid temperature, and weighted flow velocity. Based on the first pulse interval time within the continuous period and the second pulse interval time between continuous periods, pulsed ultrasonic signals are sent to the target section, and the laminar velocity corresponding to multiple velocity layers of the target section is determined based on the returned second pulse echo signal and fluid temperature. Based on the laminar velocity corresponding to multiple velocity layers, the initial velocity distribution of the target section is constructed. The initial velocity distribution is corrected based on the weighted flow velocity to obtain the velocity distribution of the target section.

[0015] The fluid cross-sectional velocity distribution determination method and system provided in this application determines the weighted velocity of the target cross-section by sending continuous ultrasonic signals to the target cross-section and determining the weighted velocity based on the returned continuous echo signals. The weighted velocity serves as an initial velocity range constraint for the pulsed ultrasonic signal, avoiding a large-scale search for transmission parameters during pulsed ultrasonic signal transmission and improving the measurement efficiency of the laminar velocity corresponding to the velocity layer. Furthermore, this embodiment introduces fluid temperature for temperature compensation when calculating the laminar velocity of the velocity layer, enabling more accurate calculation of the laminar velocity. Further, this embodiment dynamically determines the flow measurement mode corresponding to the pulsed ultrasonic signal based on liquid level information, including an interleaved periodic wave emission flow measurement mode and a flow measurement mode combining continuous periodic wave emission and phase correlation. This dynamic adaptation mechanism avoids the problem of manual parameter adjustment required when switching between full-pipe and non-full-pipe operating conditions in traditional technologies, improving the system's automation level and applicability. Furthermore, this embodiment acquires the layer velocities corresponding to multiple velocity layers through pulsed ultrasonic signals, constructs an initial velocity distribution based on these layer velocities, and then corrects the initial velocity distribution using weighted velocities. The strategy of combining "layered detail capture" with "global accuracy calibration" ensures that the final velocity distribution has both fine spatial resolution and overall accuracy, significantly improving the comprehensiveness and accuracy of flow field monitoring.

[0016] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a method for determining the velocity distribution of a fluid cross section according to an embodiment of this application. Figure 2 This is a schematic diagram illustrating the use of staggered cycles for pulsed ultrasonic signal transmission in an embodiment of this application. Figure 3 This is a schematic diagram of pulse ultrasonic signal transmission and second pulse echo signal reception in an embodiment of this application; Figure 4 This is a schematic diagram illustrating the transmission of pulsed ultrasonic signals using a first pulse interval time and a second pulse interval time in an embodiment of this application. Figure 5 This is a schematic diagram of the initial flow velocity distribution in an embodiment of this application; Figure 6 This is a schematic diagram of the velocity distribution cloud map of the target section in an embodiment of this application; Figure 7 This is a schematic diagram of the flow velocity weight percentage statistics in the embodiments of this application; Figure 8 This is a schematic diagram of the hardware structure of a fluid cross-sectional velocity distribution determination system according to an embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] This application proposes a method for determining the velocity distribution of a fluid cross-section, such as... Figure 1 As shown, it includes: S101, acquire the liquid level information and fluid temperature corresponding to the target cross-section of the fluid.

[0020] S102, send continuous ultrasonic signals to the target section, and determine the weighted flow velocity of the target section based on the returned continuous echo signals.

[0021] S103, determine the flow measurement method corresponding to the pulse ultrasonic signal based on the liquid level information. The flow measurement methods include staggered periodic wave emission flow measurement method and continuous periodic wave emission combined with phase correlation flow measurement method.

[0022] S104, if the flow measurement method is the staggered periodic wave measurement method, the staggered period is determined based on the liquid level information, fluid temperature and weighted flow velocity, the pulse ultrasonic signal is sent to the target section based on the staggered period, and the laminar flow velocity corresponding to multiple flow velocity layers of the target section is determined based on the returned first pulse echo signal and fluid temperature.

[0023] S105, if the flow measurement method is a combination of continuous periodic wave emission and phase correlation, the first pulse interval time within the continuous period and the second pulse interval time between the continuous periods are determined based on the liquid level information, fluid temperature and weighted flow velocity; pulse ultrasonic signals are sent to the target section based on the first pulse interval time within the continuous period and the second pulse interval time between the continuous periods, and the laminar flow velocity corresponding to multiple flow velocity layers of the target section is determined based on the returned second pulse echo signal and fluid temperature.

[0024] S106, based on the layer velocities corresponding to multiple velocity layers, construct the initial velocity distribution of the target section.

[0025] S107, the initial velocity distribution is corrected based on the weighted velocity to obtain the velocity distribution of the target section. For ease of understanding, the following explains some key terms in this embodiment: Fluid cross-section: refers to the section of a fluid passage perpendicular to the flow direction. This section is the area used for velocity measurement and distribution analysis.

[0026] Liquid level information: refers to the height or depth data of the fluid at the target cross-section. This information is used to determine the fluid filling state, such as shallow flow, incomplete or full pipe conditions, and to adjust the measurement parameters accordingly.

[0027] Fluid temperature: refers to the actual temperature of the fluid. Fluid temperature affects the propagation speed of ultrasound waves in the fluid, therefore temperature compensation is required in flow velocity calculations.

[0028] Continuous ultrasonic signal: refers to a continuously emitted ultrasonic signal. This signal is used to obtain overall or weighted average flow velocity information of a fluid target cross-section through the Doppler effect.

[0029] Continuous echo signal: refers to the signal returned by a continuous ultrasonic signal after encountering a scattering body in a fluid. By analyzing the frequency shift of this echo signal, the weighted velocity of the fluid can be determined.

[0030] Weighted velocity: refers to the weighted average value of the overall velocity characteristics of the fluid target cross section, obtained by continuous ultrasonic signal measurement. This value can be used as a global calibration benchmark for stratified velocity data.

[0031] Pulsed ultrasonic signal: refers to an intermittently emitted ultrasonic signal consisting of a series of short pulses. This signal is used to locate and measure fluid flow velocity layers at different depths by controlling the pulse transmission and reception time.

[0032] Flow measurement method: refers to the specific technical method used to determine fluid velocity. This embodiment includes an interleaved periodic wave measurement method and a flow measurement method combining continuous periodic wave generation and phase correlation, to adapt to different fluid conditions.

[0033] Interleaved periodic wave emission flow measurement mode: This refers to a pulse ultrasonic signal transmission mode in which the pulse transmission period alternates. This mode is mainly used to solve the velocity ambiguity problem caused by Doppler frequency shift in shallow flow conditions.

[0034] Flow measurement method combining continuous periodic wave emission and phase correlation: This refers to another pulse ultrasonic signal transmission mode that combines continuous periodic pulse emission with phase correlation technology between pulses. This method is suitable for situations with deep liquid levels or high flow velocities to achieve high-precision stratified measurement.

[0035] Interleaved period: refers to the time interval between two or more different pulses used to transmit pulsed ultrasonic signals in the interleaved period wave measurement method.

[0036] First pulse echo signal: refers to the signal returned by the pulsed ultrasonic signal after encountering a scattering body in the fluid when using the staggered periodic wave emission flow measurement method.

[0037] Velocity layer: refers to multiple regions with different velocity characteristics that divide the cross-section of a fluid target along the depth direction.

[0038] Laminar velocity: refers to the average velocity within each velocity layer. By measuring the laminar velocity of multiple velocity layers, the velocity distribution of a fluid cross-section can be constructed.

[0039] First pulse interval time: refers to the interval time between adjacent pulses within a continuous period in a flow measurement method that combines continuous periodic wave generation with phase correlation.

[0040] Second pulse interval time: refers to the interval time between pulses in different continuous cycles in a flow measurement method that combines continuous periodic wave generation with phase correlation.

[0041] Second pulse echo signal: refers to the signal returned by the pulsed ultrasonic signal after encountering a scattering body in the fluid when using a flow measurement method that combines continuous periodic wave emission with phase correlation.

[0042] Initial velocity distribution: refers to the continuous velocity distribution curve of the fluid target section initially constructed by interpolation and other methods based on the layer velocities corresponding to multiple velocity layers.

[0043] Velocity distribution: refers to the accurate velocity distribution of the target fluid cross section after weighted velocity correction.

[0044] This embodiment provides a method for determining the velocity distribution of a fluid cross section. This method achieves accurate acquisition of the velocity distribution of a fluid cross section through multi-mode ultrasonic measurement and data fusion correction.

[0045] First, regarding step S101, this step can be achieved by placing a sensor probe in the fluid, where a hydrostatic sensor inside the probe measures the fluid level, and a temperature sensor measures the fluid temperature. For example, the hydrostatic sensor can output real-time fluid depth data, and the temperature sensor can provide real-time fluid temperature values. Alternatively, the fluid level and temperature can also be manually observed and input into the system. The fluid can specifically be municipal sewage, industrial wastewater, or recycled water.

[0046] Secondly, regarding step S102, in this step, an ultrasonic sensor, such as an ultrasonic Doppler sensor, can continuously emit continuous ultrasonic signals into the fluid in continuous wave mode (CW mode). When these signals encounter scattering bodies such as suspended particles in the fluid, they generate echo signals with frequency shifts. The received continuous echo signals can be analyzed by simple frequency analysis, such as directly extracting the dominant frequency shift, to obtain a weighted flow velocity v_weight representing the overall flow velocity of the target cross-section.

[0047] Furthermore, regarding step S103, in this step, the system can select a suitable pulse ultrasonic flow measurement method based on the acquired liquid level information, such as through a preset liquid level threshold. For example, when the liquid level is below a certain preset threshold, the system can be configured to use an interleaved periodic wave emission flow measurement method; when the liquid level is above the threshold, the system can be configured to use a flow measurement method combining continuous periodic wave emission and phase correlation.

[0048] The interleaved periodic emission current measurement method is a narrowband coherent current measurement method. In the narrowband coherent current measurement method, the initial phase relationship between adjacent transmitted pulses is determined and known, i.e., "inter-pulse coherence". In the interleaved periodic emission current measurement method, the inter-symbol coherence time can be alternately varied, such as the first time of inter-symbol coherence. Second time of inter-code coherence Alternately.

[0049] The flow measurement method combining continuous periodic emission and phase correlation is a combination of narrowband coherent flow measurement and broadband flow measurement. Since the broadband flow measurement method uses multiple repeated phase-coded signals while accommodating both large signal duration and bandwidth, the continuous periodic emission and phase correlation method employs a combination of inter-code correlation and intra-code coherence. Intra-code coherence confirms the velocity distribution range through multiple consecutive coherent pulse transmissions, while inter-code correlation determines velocity accuracy through phase correlation of the Barker-coded signal. The combination of these two methods achieves high-precision, layered measurement.

[0050] As an optional implementation method, the flow measurement method can also be manually selected by the operator based on experience.

[0051] Specifically, regarding step S104, when the system determines to use the staggered periodic wave emission method for flow measurement, it can determine one or more staggered pulse emission periods based on the current liquid level information, fluid temperature, and previously determined weighted flow velocities, using a preset calculation model or lookup table. Subsequently, the ultrasonic sensor, such as an ultrasonic Doppler sensor, emits pulsed ultrasonic signals to the fluid according to these determined staggered periods in pulse wave mode (PW mode). The received first pulse echo signal is processed and compensated for by the fluid temperature to calculate the laminar flow velocity of multiple velocity layers at different depths of the fluid target cross-section. For example, as... Figure 2 As shown, a fixed set of interleaved periods (T1, T2) can be used for pulse transmission and echo reception, and then the laminar flow velocity can be obtained by simple Doppler frequency shift calculation.

[0052] Specifically, regarding step S105, when the system determines to use a flow measurement method combining continuous periodic wave emission and phase correlation, it can determine the first pulse interval time within the continuous period and the second pulse interval time between continuous periods based on the current liquid level information, fluid temperature, and weighted flow velocity. Subsequently, the ultrasonic sensor, such as an ultrasonic Doppler sensor, in pulse wave mode (PW mode), emits pulsed ultrasonic signals to the fluid according to these determined interval times, such as... Figure 3 The coded pulse 1, coded pulse 2, ... shown are received, and the returned second pulse echo signal is received, as shown. Figure 3 As shown, unit 1, unit 2, and unit 3 represent velocity layers, and Td represents the second pulse interval time between consecutive cycles. The received second pulse echo signal is processed and compensated for by fluid temperature to calculate the laminar flow velocity of multiple velocity layers at different depths of the fluid target cross-section. In specific implementations, for example, as... Figure 4 As shown, a fixed set of first pulse interval time (T3) and second pulse interval time (T4) can be used for pulse transmission and echo reception, and then the laminar flow velocity can be obtained by simple Doppler frequency shift calculation.

[0053] In step S106, the layer velocity data points corresponding to the multiple discrete velocity layers obtained above are processed to form a continuous velocity distribution curve, thus obtaining an initial velocity distribution. For example, linear interpolation can be used to connect the velocities between adjacent velocity layers to obtain a preliminary, continuous velocity distribution. For example, in a scenario with a weighted velocity of approximately 0.3 m / s, when the encoding length is 21, there are 38 velocity layers, and each velocity layer is 0.006 m, the initial velocity distribution is as follows: Figure 5 As shown.

[0054] Finally, regarding step S107, the weighted velocity obtained previously through continuous ultrasonic signals is used as a global reference to adjust the initially constructed initial velocity distribution. For example, the average value of the initial velocity distribution can be calculated, and then the entire initial velocity distribution can be scaled using a simple scaling factor to make its average value consistent with the weighted velocity, thereby obtaining the final velocity distribution.

[0055] In some implementations, based on the final velocity distribution, fluid parameters such as maximum velocity, average velocity, velocity gradient, and flow rate can be further determined, and a velocity distribution cloud map of the target cross-section can also be determined, such as... Figure 6 As shown. Then, wireless communication can be used to upload the velocity distribution of the target cross section, the velocity distribution cloud map of the target cross section, and fluid parameters such as weighted velocity, maximum velocity, average velocity, velocity gradient, and flow rate to the monitoring platform.

[0056] The following example will provide a more detailed explanation of the above technical solution: 1. Implementation Scenario: Taking a DN800 reinforced concrete pipeline of a municipal sewage network as the implementation object, the pipeline is 1200m long and receives domestic sewage and a small amount of industrial wastewater along the way. There are switching between non-full pipe (liquid level 0.4-0.6m) and shallow flow (liquid level drops to 0.2m after rain). It is necessary to realize accurate monitoring of cross-sectional flow velocity and flow calculation to provide a basis for predicting the influent load of sewage treatment plants.

[0057] 2. Equipment and tool preparation: Core equipment: 2 pipe flow velocity cross-section scanning monitoring devices (integrating hydrostatic level sensor, ultrasonic Doppler sensor and temperature sensor), equipped with 10000mAh battery; 1 local monitoring platform (including data receiving and visualization software); 2 wall-mounted mounting brackets.

[0058] Calibration tools: standard flow rate calibration device (accuracy ±0.1%), simulated wastewater with chemical oxygen demand = 500 mg / L (containing 500 mg / L suspended solids), and liquid level measuring ruler (accuracy ±1 mm).

[0059] 3. Implementation steps: 1) Preliminary preparation and calibration: ① In the laboratory, the pipeline flow velocity cross-section scanning monitoring equipment is calibrated using a standard flow velocity calibration device. The ultrasonic emission frequency is set to 4MHz, the ultrasonic frequency is set to 5 minutes, and the measurement cycle is set to 5 minutes. ② The equipment is placed in simulated sewage to verify the measurement accuracy under low flow velocity (0.05m / s) and high flow velocity (2m / s) conditions, ensuring that the error is ≤±3%.

[0060] 2) Equipment deployment: ① Install wall-mounted brackets at 200m and 800m of the pipeline, with the brackets 10cm above the bottom of the pipeline to ensure that the probes are fully immersed in the water; ② Fix the two devices to the brackets and adjust the probe angle so that the ultrasonic propagation direction makes an angle θ=45° with the water flow; ③ Complete the communication connection between the devices and the local monitoring platform through the communication module and configure the transmission parameters.

[0061] 3) System Operation and Data Acquisition: ① After system startup, the first liquid level h=0.52m (non-full pipe condition) was collected by device #1 (200m), water temperature T=23℃, and the weighted flow velocity v_weight=0.82m / s was output in CW mode; ② The flow velocity of 32 velocity layers was obtained by measuring at a pulse frequency of 10kHz in PW mode. The maximum flow velocity was 1.2m at the center of the pipe (depth 0.26m) and the minimum flow velocity was 0.35m / s at the pipe wall (depth 0.05m); ③ Data was collected synchronously by device #2 (800m), h=0.48m, v_weight=0.78m / s.

[0062] 4) Flow field reconstruction and verification: ① The platform reconstructed the discrete layer velocity of device #1 into a continuous velocity curve through cubic spline interpolation. After v_weight calibration, the output average velocity was 0.81 m / s, and the flow rate Q = 0.81 × (π × 0.4² - π × (0.4 - 0.5²)²) = 0.81 × 0.5 = 0.405 m³ / s; ② Verification was performed using a pipe outlet flow meter (accuracy ±1%), and the actual flow rate was 0.402 m³ / s, with a relative error of 0.75%; ③ After rain, device #1 monitored h = 0.22 m (shallow flow condition). The system automatically switched to the staggered periodic wave measurement mode, and v_weight = 0.35 m / s, with an average velocity of 0.34 m / s, and an error of 1.2% compared with the manually measured value.

[0063] 5) Abnormal warning and handling: ① On the 30th day of operation, the platform detected an abnormal flow velocity gradient in equipment #2 (the flow velocity dropped by 40% at a depth of 0.3m). Based on the liquid level data, it was determined that there was local siltation in the pipeline. ② The maintenance personnel went to the site and found siltation (mud layer thickness of 15cm) 5m downstream of equipment #2. After the silt was cleared, the equipment data returned to normal and the flow velocity gradient was uniform.

[0064] 4. Implementation Results The system operated continuously for 60 days, with both devices working stably and a data transmission success rate of 99.9%. The average flow velocity measurement error was ≤1.5% and the flow calculation error was ≤1% under all operating conditions, which is a significant improvement in accuracy compared to traditional single-point flow meters (12% error). Two pipe siltation points were successfully located, and the pipe flow capacity was increased by 20% after dredging. The device battery had 72% remaining power and is expected to work continuously for more than 9 months. The average annual maintenance cost per device is 6,000 yuan lower than that of traditional equipment.

[0065] As can be seen from the above examples, the method provided in this embodiment can effectively solve the problems in the prior art, such as obvious limitations in flow field adaptability, limited measurement accuracy, weak data correlation, and the inability of a single mode to capture flow field details.

[0066] The fluid cross-sectional velocity distribution determination method provided in this embodiment sends continuous ultrasonic signals to the target cross-section and determines the weighted velocity of the target cross-section based on the returned continuous echo signals. The weighted velocity serves as an initial velocity range constraint for the pulsed ultrasonic signal, avoiding a large-scale search for transmission parameters during pulsed ultrasonic signal transmission and improving the measurement efficiency of the laminar velocity corresponding to the velocity layer. Furthermore, this embodiment introduces fluid temperature for temperature compensation when calculating the laminar velocity of the velocity layer, which can more accurately calculate the laminar velocity of the velocity layer. Furthermore, this embodiment dynamically determines the flow measurement mode corresponding to the pulsed ultrasonic signal based on liquid level information, including an interleaved periodic wave emission flow measurement mode and a flow measurement mode combining continuous periodic wave emission and phase correlation. The dynamic adaptation mechanism avoids the problem of manual parameter adjustment required when switching between full-pipe and non-full-pipe operating conditions in traditional technologies, improving the automation level and applicability of the system. Furthermore, this embodiment acquires the layer velocities corresponding to multiple velocity layers through pulsed ultrasonic signals, constructs an initial velocity distribution based on these layer velocities, and then corrects the initial velocity distribution using weighted velocities. The strategy of combining "layered detail capture" with "global accuracy calibration" ensures that the final velocity distribution has both fine spatial resolution and overall accuracy, significantly improving the comprehensiveness and accuracy of flow field monitoring.

[0067] In an optional embodiment, this application further proposes a method for determining the weighted flow velocity of a target section based on the returned continuous echo signal, comprising: converting the continuous echo signal into a frequency domain signal and extracting the frequency shift value corresponding to the peak frequency point in the frequency domain signal; performing cumulative calculation on the frequency shift value based on the peak frequency point to obtain the cumulative amplitude corresponding to each peak frequency point; determining the maximum local velocity point based on the cumulative amplitude, the maximum local velocity point including the maximum cumulative amplitude and the corresponding target peak frequency point; determining the water flow direction corresponding to the maximum local velocity point based on the frequency shift value corresponding to the target peak frequency point; determining the flow velocity start point and flow velocity end point corresponding to the maximum local velocity point based on the target peak frequency point, the cumulative amplitude, and the maximum cumulative amplitude; determining the flow velocity centroid point corresponding to the maximum local velocity point based on the flow velocity start point and flow velocity end point; and determining the weighted flow velocity of the target section based on the water flow direction and the cumulative amplitude corresponding to the flow velocity centroid point.

[0068] Specifically, the received high-frequency continuous echo signal is first mixed with the local oscillator signal to convert it into an intermediate frequency signal of 10-100kHz. Then, an 8th-order low-pass filter is used to remove high-frequency noise, and noise spectrum estimation techniques are used to eliminate random interference. Next, a Fast Fourier Transform (FFT) is employed to convert the time-domain signal to a frequency-domain signal, and the Doppler frequency shift value corresponding to the peak frequency point is extracted. Finally, a flow velocity weight percentage statistical algorithm is used, combined with the ultrasonic propagation characteristics to correct the Doppler formula, to obtain the cross-sectional weighted flow velocity v_weight.

[0069] The specific implementation steps of the flow velocity weight percentage statistical algorithm include: Step 1: Calculate the cumulative amplitude: Accumulate the Doppler frequency shift values ​​corresponding to the peak frequency points to filter out noise interference. The formula is as follows: FBlock(n) = Σ[Abs(Dfft(k))] (where k ranges from 0 to n, n is the spectrum number corresponding to the peak frequency point, ranging from 0 to 4095; FBlock is the cumulative amplitude, Abs(Dfft) is the absolute value of the Doppler frequency shift corresponding to the peak frequency point, and Gate is the noise threshold for the peak frequency point. When Abs(Dfft(k)) ≤ Gate, the data point is removed).

[0070] Step 2: Find the point of maximum local velocity: Traverse the cumulative amplitude, locate the maximum cumulative amplitude and its corresponding number, using the following formula: MaxFBAmp=Max[FBlock(n)](n∈0-4095); MaxFBpos = argMax[FBlock(n)], where MaxFBAmp is the maximum cumulative amplitude and MaxFBpos is the number corresponding to the maximum cumulative amplitude, i.e., the target peak frequency point.

[0071] Step 3: Determine the direction of the point of maximum local velocity: The direction of water flow at the point of maximum local velocity is determined using a sign function, the formula of which is: MaxFBsgn = Sgn(Dfft(MaxFBpos)), where Sgn is a symbolic function that returns 1 when Dfft(MaxFBpos) > 0, -1 when Dfft(MaxFBpos) < 0, and 0 when Dfft(MaxFBpos) = 0.

[0072] Step 4: Find the starting point FBbpos of the maximum local velocity: With MaxFBpos as the center, traverse the FBlock data to the left. Stop when FBlock(n)≤MaxFBAmp×10%, and n is the starting point FBbpos. If the condition is not met when traversing to n=0, then FBbpos=0.

[0073] Step 5: Find the endpoint FBepos of the maximum local velocity: Using MaxFBpos as the center, traverse the FBlock data to the right. Stop when FBlock(n) ≤ MaxFBAmp × 10%, and n is the endpoint FBepos. If the condition is not met when traversing to n = 4095, then FBepos = 4095.

[0074] Step 6: Calculate the centroid of the maximum local velocity, AvgPos: The centroid reflects the core location of the velocity distribution, and the formula is: AvgPos=[Σ(n×FBlock(n))] / [ΣFBlock(n)], where n ranges from FBbpos to FBepos.

[0075] Step 7: Calculate the average flow velocity AvgFlow, also known as the weighted flow velocity: Combining sensor parameters and centroid data, the formula is derived using the Doppler effect. The formula is as follows: AvgFlow=MaxFBsgn×(AvgPos×Fs×Uspeed) / (2×Snum×f×cos(Ang)).

[0076] Parameter values: signal sampling rate Fs=40kHz, sound speed in water Uspeed=1500m / s, number of FFT points Snum=4096, ultrasonic wave emission frequency f=1MHz, angle between the sensor emission direction and the water flow direction Ang=30°.

[0077] In some implementations, a flow velocity weight percentage chart can be further generated, and the calculation process includes: Step 8: Determine the maximum velocity point PmaxPos in the weighted graph: Apply a rounding constraint to the centroid point AvgPos to ensure that the landing point falls on the spectrum number corresponding to the standard velocity point. The formula is: PmaxPos = Ceil125(AvgPos), where Ceil125 is a function that rounds to positive infinity, and the rounded value is constrained to the range of spectral data point numbers corresponding to flow velocities of 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 m / s.

[0078] Step 9: Calculate the step size PPos for the velocity points in the weighted map. Step: Determine the interval between adjacent velocity points based on PmaxPos, using the following formula: PPosStep = PmaxPos / 5. When PmaxPos ≤ 100, take a fixed value of 20 to ensure the step size is reasonable.

[0079] Step 10: Calculate the coordinates of the velocity points in the weighted graph, PFlow: Convert the spectrum number to the actual velocity value and use it as the x-axis of the weighted graph. The formula is: PFlow=(PPosStep×Fs×Uspeed) / (2×Snum×f×cos(Ang)).

[0080] Step 11: Calculate the velocity point coefficient PFlowValue in the weighted graph: This coefficient reflects the weight percentage of each velocity point and is used as the vertical axis of the weighted graph. The formula is: PFlowValuen=[ΣAbs(Dfft(k))] / MaxFBAmp×100%, k ranges from (n-1)×PPosStep to n×PPosStep, and n is the weight point number, ranging from 1 to 5.

[0081] Step 12: Plot a velocity weight percentage chart: Using PFlow as the x-axis (unit: m / s) and PFlowValue as the y-axis (unit: %), generate an intuitive velocity weight distribution curve that clearly presents the cross-sectional velocity distribution characteristics, such as... Figure 7 As shown.

[0082] Through the above steps, the algorithm can output accurate average flow velocity AvgFlow (i.e., the weighted flow velocity v_weight in CW mode) and flow velocity weight distribution map, providing reliable global benchmark data for subsequent PW mode parameter adjustment and flow field reconstruction.

[0083] The proposed solution first converts the received continuous echo signal from the time domain to the frequency domain, thereby revealing the Doppler frequency shift information caused by fluid motion. Next, the frequency shift values ​​corresponding to the peak frequency points in the frequency domain signal are accumulated to enhance the effective signal and suppress noise, obtaining the accumulated amplitude corresponding to each peak frequency point. Based on this, the maximum local velocity point with the largest accumulated amplitude and its corresponding target peak frequency point are identified, which helps to focus on the main motion characteristics of the fluid. Subsequently, the direction of water flow is determined based on the sign of the frequency shift value corresponding to the target peak frequency point. To more accurately characterize this local velocity, the effective range of the maximum local velocity point in the frequency domain, i.e., the velocity start point and velocity end point, is further determined based on the target peak frequency point, the accumulated amplitude, and the maximum accumulated amplitude. Within this effective range, the velocity centroid is calculated through weighted averaging. This centroid comprehensively considers the energy distribution of the local area, thus providing a more robust velocity estimate than a single peak point. Finally, the weighted velocity of the target cross-section is calculated by combining the determined water flow direction and the accumulated amplitude corresponding to the velocity centroid. This series of processing steps makes the weighted velocity extracted from complex continuous echo signals more accurate and robust, providing a reliable foundation for subsequent construction and correction of velocity distribution.

[0084] In an optional embodiment, this application further proposes to determine the flow measurement method corresponding to the pulsed ultrasonic signal based on liquid level information. If the liquid level information indicates that the liquid level is less than or equal to the target liquid level, the flow measurement method corresponding to the pulsed ultrasonic signal is determined to be an interleaved periodic wave emission flow measurement method; if the liquid level information indicates that the liquid level is greater than the target liquid level, the flow measurement method corresponding to the pulsed ultrasonic signal is determined to be a flow measurement method combining continuous periodic wave emission and phase correlation.

[0085] As one specific implementation method, the target liquid level can be 0.3m.

[0086] Through the above technical solution, this application can intelligently select the most suitable pulse ultrasonic flow measurement method for the current environment based on the actual liquid level information of the fluid. This effectively solves the problems of limited applicability and decreased measurement accuracy that may exist with a single flow measurement method under different liquid level conditions. In an optional embodiment, this application further proposes determining the interleaving period based on the liquid level information, the fluid temperature, and the weighted flow velocity, including: determining the propagation speed of the pulsed ultrasonic signal in the fluid based on the fluid temperature; determining a third pulse interval time based on the liquid level information and the propagation speed; determining a fourth pulse interval time based on the third pulse interval time, the weighted flow velocity, and the propagation speed; and obtaining the interleaving period based on the third pulse interval time and the fourth pulse interval time.

[0087] In this embodiment, in the interleaved periodic emission current measurement method, the inter-symbol coherence time is alternately transformed, that is, the first time of inter-symbol coherence is... Second time of inter-code coherence Alternately, such as Figure 2 As shown. The first time interval of inter-symbol coherence is the third pulse interval time, and the second time interval of inter-symbol coherence is the fourth pulse interval time.

[0088] Inter-code coherence first time The current liquid level h (e.g., water depth h) is collected by a hydrostatic sensor and the calculation formula is as follows: , The propagation speed of a pulsed ultrasonic signal in a fluid. The angle between the direction of ultrasonic propagation and the water flow.

[0089] The propagation speed of a pulsed ultrasonic signal in a fluid is a fundamental parameter for ultrasonic measurements, and its value is significantly affected by fluid temperature. Accurately determining the propagation speed is essential for all subsequent time- or distance-based calculations. This can be achieved by establishing a pre-defined functional relationship between fluid temperature and ultrasonic wave propagation speed. To obtain the propagation speed of pulsed ultrasonic signals in fluids. .

[0090] Inter-code coherence second time It needs to be combined with the weighted flow rate v_weight, which is composed of v_weight and Joint computation, inter-symbol coherence second time The calculation formula is as follows: , in The calculation formula is as follows: , The frequency of the pulsed ultrasonic signal.

[0091] The solution proposed in this application achieves adaptive determination of the staggered period through a series of logical steps. This method of dynamically adjusting the staggered period enables the transmission of pulsed ultrasonic signals to better match the real-time changing parameters of the fluid, such as liquid level, temperature, and flow rate, laying the foundation for subsequent accurate measurement of the laminar flow velocity corresponding to multiple flow velocity layers.

[0092] In an optional embodiment, this application further proposes determining the laminar flow velocity corresponding to multiple velocity layers of a target cross section based on the returned first pulse echo signal and fluid temperature, including: determining the first phase angle corresponding to each of the multiple velocity layers of the target cross section based on the first pulse echo signal corresponding to the pulsed ultrasonic signal emitted at a third pulse interval, and determining the first fluid velocity corresponding to each of the multiple velocity layers of the target cross section based on the first phase angle; determining the second phase angle corresponding to each of the multiple velocity layers of the target cross section based on the first pulse echo signal corresponding to the pulsed ultrasonic signal emitted at a fourth pulse interval, and determining the second fluid velocity corresponding to each of the multiple velocity layers of the target cross section based on the second phase angle; and determining the laminar flow velocity of each velocity layer of the target cross section based on the corresponding first fluid velocity, the corresponding second fluid velocity, and the fluid temperature.

[0093] In this embodiment, the processing of the first pulse echo signal may include: performing orthogonal scaling and down-conversion processing on the first pulse echo signal to convert it into an intermediate frequency signal, then performing complex correlation operation and frequency estimation on the intermediate frequency signal to determine the phase angle, then deriving the velocity formula, and calculating the laminar flow velocity in combination with temperature compensation parameters.

[0094] The process of performing complex correlation and frequency estimation on the intermediate frequency signal, and then calculating the laminar flow velocity by combining the temperature compensation parameters, is as follows: Assume the transmitted signal is a cosine wave S(t) with a transmission frequency of... The initial phase angle of the emitted wave is The signal amplitude is The transmitted signal can then be represented as: , General situation: =0, so the transmitted signal can be simplified to: , Due to the Doppler frequency shift effect, the pulse echo signal This will cause frequency offset, and the frequency will become The phase angle becomes The signal amplitude becomes 1, then the pulse echo signal It can be expressed as follows: , in: , It is a frequency offset signal, which is related to the fluid velocity.

[0095] The above pulse echo signal The intermediate frequency signal is obtained by performing IQ quadrature modulation and low-pass filtering, and named the IQ signal: , , Then, the above IQ signals are synthesized into a complex signal Sr(t): , right Perform complex correlation operation, and calculate as follows: , In the formula: yes The conjugate complex number. And the data after complex autocorrelation is only related to the Doppler frequency shift of the signal. If related, then the phase after autocorrelation for: , Finally, the speed formula is derived: , in: This represents the speed at which ultrasonic signals propagate in water.

[0096] The most significant influencing factor is temperature. The relationship between temperature and the speed of sound is as follows: , because This can cause blurring; the corrected formula is as follows: , fluid velocity The calculation formula is revised as follows: .

[0097] Through the above calculation process, the formula for calculating the first fluid velocity based on the first pulse echo signal corresponding to the pulsed ultrasonic signal emitted at the third pulse interval time T1 for each velocity layer of the target section is as follows: , in This is the first phase angle.

[0098] The formula for calculating the second fluid velocity based on the first pulse echo signal corresponding to the pulsed ultrasonic signal emitted based on the fourth pulse interval T2 is as follows: , in, This is the second phase angle.

[0099] The two fluid velocity formulas above can be solved by combining them. and Then calculate the first fluid velocity and the second fluid velocity v, which is also the laminar flow velocity.

[0100] Through the above technical solution, this application effectively addresses the potential issues of insufficient accuracy and reliability in measuring laminar velocity using a single pulse signal when employing an interleaved periodic wavelet flow measurement method. By acquiring two independent fluid velocities of the velocity layer at different pulse intervals and combining this with fluid temperature for comprehensive processing, the accuracy and stability of laminar velocity measurement can be significantly improved. This multi-measurement and data fusion method effectively suppresses random noise and systematic errors, making the final determined laminar velocity closer to the actual fluid motion state, thus laying the foundation for constructing a more accurate velocity distribution.

[0101] In an optional embodiment, this application further proposes a method for determining a first pulse interval time within a continuous period and a second pulse interval time between continuous periods based on liquid level information, fluid temperature, and weighted flow velocity, comprising: determining the propagation speed of the pulsed ultrasonic signal in the fluid based on fluid temperature; determining the first pulse interval time within a continuous period based on weighted flow velocity and propagation speed; and determining the second pulse interval time between continuous periods based on the first pulse interval time, liquid level information, and propagation speed.

[0102] In this embodiment, the flow measurement method combining continuous periodic emission and phase correlation employs a combination of inter-code correlation and intra-code coherence. Intra-code coherence confirms the velocity distribution range through multiple consecutive coherent pulse transmissions, while inter-code correlation determines velocity accuracy through phase correlation of the Barker-coded signal. The combination of these two methods achieves high-precision layered measurement. The first pulse interval of the intra-code coherence is... The interval between the second and third pulses of the encoded pulse is ,like Figure 4 As shown.

[0103] It needs to be calculated in conjunction with the weighted flow rate v_weight, and the calculation formula is as follows: , The current liquid level h and collected by the hydrostatic sensor The calculation formula is: , fluid temperature With the speed of ultrasonic wave propagation The functional relationship between them is: , in, The frequency of the pulse ultrasound signal. The angle between the direction of ultrasonic propagation and the water flow.

[0104] The proposed solution first accurately measures the fluid temperature and determines the propagation speed of the pulsed ultrasonic signal within the fluid, providing a precise physical basis for subsequent pulse interval calculations. Second, when determining the first pulse interval within a continuous cycle, the solution utilizes a weighted flow velocity and the determined propagation speed. The weighted flow velocity reflects the overall motion trend of the fluid; combined with the propagation speed, the approximate time required for the ultrasonic wave to propagate and return within the fluid can be estimated, thus setting a first pulse interval that ensures both signal non-aliasing and effective sampling. Finally, when determining the second pulse interval between consecutive cycles, the solution further considers liquid level information, the first pulse interval, and the propagation speed. The liquid level information determines the maximum distance the ultrasonic wave needs to propagate; combined with the propagation speed, the maximum time required for the ultrasonic wave to travel from emission to reception of the farthest echo can be calculated. Based on this, and combined with the first pulse interval, a sufficiently long second pulse interval can be set to ensure complete attenuation of all echo signals from the previous consecutive cycle, avoiding signal interference between different consecutive cycles, while simultaneously ensuring the continuity and efficiency of the measurement process. Through this progressive and interconnected calculation method, this scheme ensures that the transmission interval of pulsed ultrasonic signals can be adaptively adjusted in complex fluid environments, thereby effectively avoiding signal aliasing, improving the quality of echo signals, and laying the foundation for accurately determining the laminar flow velocities corresponding to multiple flow velocity layers.

[0105] In an optional embodiment, this application further proposes a step of determining the laminar flow velocity corresponding to multiple velocity layers of a target section based on the returned second pulse echo signal and fluid temperature, including: determining the third phase angle corresponding to each of the multiple velocity layers of the target section based on the second pulse echo signal corresponding to the pulsed ultrasonic signal emitted at the first pulse interval, and determining the third fluid velocity corresponding to each of the multiple velocity layers of the target section based on the third phase angle; determining the fourth phase angle corresponding to each of the multiple velocity layers of the target section based on the second pulse echo signal corresponding to the pulsed ultrasonic signal emitted at the second pulse interval, and determining the fourth fluid velocity corresponding to each of the multiple velocity layers of the target section based on the fourth phase angle; and determining the laminar flow velocity of each velocity layer of the target section based on the corresponding third fluid velocity, the corresponding fourth fluid velocity, and the fluid temperature.

[0106] In this embodiment, the processing procedure for the second pulse echo signal is the same as that for the first pulse echo signal in the above embodiment, and will not be repeated here. By processing the second pulse echo signal, the third phase angle can be determined. and the fourth phase angle .

[0107] Due to the interval time of the first coherent pulse within the code Very short. There will be no blurring. Therefore, the intra-code coherence velocity, which is also the third fluid velocity, is... The calculation is as follows: , Encoded pulse second pulse interval time If the length is too long, blurring will occur, so the intersymbol correlation velocity, also known as the fourth fluid velocity, is crucial. The calculation is as follows: , Among them, fluid temperature With the speed of ultrasonic wave propagation The functional relationship between them is: , For each velocity layer of the target section, the corresponding and Solving for parameters using simultaneous equations Then we can calculate a more accurate result. Thus, the laminar velocity of the velocity layer is obtained.

[0108] This application's method combines continuous periodic wave emission with phase correlation in flow measurement. It utilizes two different pulse intervals (a first pulse interval and a second pulse interval) to transmit pulsed ultrasonic signals, and extracts phase angles (a third phase angle and a fourth phase angle) from the returned second pulse echo signals to calculate preliminary fluid velocities (a third fluid velocity and a fourth fluid velocity). Subsequently, for each velocity layer, these two preliminary fluid velocities are combined with fluid temperature to determine the final laminar velocity. This dual measurement strategy, combined with temperature compensation, effectively utilizes multi-source information for mutual verification and correction, thereby improving the accuracy and reliability of laminar velocity measurement. The introduction of fluid temperature ensures the accuracy of sound velocity calculation and further enhances the precision of velocity conversion. In this way, the proposed method can more accurately obtain the laminar velocity of the fluid cross-section, laying a solid foundation for subsequent construction and correction of the velocity distribution.

[0109] In an optional embodiment, this application further proposes a step of constructing an initial velocity distribution of the target section based on the layer velocities corresponding to multiple velocity layers, including: interpolating the layer velocities corresponding to multiple velocity layers to obtain an initial velocity distribution of the target section, wherein the initial velocity distribution satisfies the following conditions: the velocity of each velocity layer is the corresponding layer velocity, the velocity between adjacent velocity layers is a cubic polynomial, and the second derivative of the initial velocity distribution is continuous.

[0110] In practical implementation, the obtained discrete layer velocities can be processed into continuous flow using a cubic spline interpolation algorithm. The specific algorithm includes: Let the depth of the discrete velocity layer be x1, x2, ..., x...n The corresponding layer velocities are v1, v2, ..., v n Construct an interpolation function S(x) that satisfies: ① S(x) i )=v i (i=1,2,...,n); ②S(x) in the interval [x i ,x i+1 The expression within the expression is a cubic polynomial; ③ The second derivative is continuous. Then, the discrete points are smoothly connected using this algorithm to obtain a continuous velocity distribution curve v(x) along the depth, thus initially constructing the initial velocity distribution of the target cross-section.

[0111] This application's scheme aims to construct a continuous and physically reasonable initial velocity distribution from discrete measurement data by interpolating the laminar velocities corresponding to multiple velocity layers. Specifically, after obtaining the laminar velocities corresponding to multiple velocity layers of the target fluid cross-section, this scheme does not simply connect these discrete points, but employs a refined interpolation strategy. First, through interpolation operations, these discrete laminar velocity data are transformed into a continuous function that can describe the velocity changes across the entire cross-section. In constructing this continuous function, this scheme strictly adheres to two key conditions: first, ensuring that the obtained initial velocity distribution at each velocity layer precisely corresponds to the actual measured laminar velocity, thus guaranteeing the accuracy of the interpolation results; second, limiting the velocity changes between adjacent velocity layers to be described by a cubic polynomial, which gives the velocity curve good fitting ability and flexibility locally. Furthermore, this scheme also requires the second derivative of the constructed initial velocity distribution to be continuous, meaning that the curvature of the velocity curve transitions smoothly across the entire cross-section without abrupt changes. This combination of second-derivative continuity and cubic polynomial effectively avoids unnatural sharp transitions or oscillations in the velocity distribution between different layers, thus ensuring that the constructed initial velocity distribution not only passes through all measurement points but also exhibits high smoothness and rationality both mathematically and physically. In this way, this scheme can transform discrete layer velocity data into a continuous, smooth, and accurate initial velocity distribution that reflects the characteristics of fluid motion, providing high-quality foundational data for subsequent velocity distribution correction.

[0112] In an optional embodiment, this application further proposes a step of correcting the initial velocity distribution based on the weighted velocity to obtain the velocity distribution of the target cross-section, comprising: determining the weight of each velocity layer based on the cross-sectional area ratio corresponding to each velocity layer; calculating the weighted average value of the initial velocity distribution based on the weights and the initial velocity distribution; correcting the boundary conditions and coefficients of the initial velocity distribution based on the weighted average value of the initial velocity distribution and the weighted velocity to obtain the velocity distribution of the target cross-section; wherein the weighted average value corresponding to the velocity distribution satisfies the consistency condition with the weighted velocity.

[0113] In this embodiment, "determining the weight of each velocity layer based on the proportion of its cross-sectional area" means that, in order to accurately reflect the contribution of each velocity layer to the total flow rate of the entire fluid cross-section, it is necessary to assign a corresponding weight based on the proportion of the cross-sectional area it occupies. This can be achieved by pre-measuring or modeling the geometry of the fluid cross-section and combining it with the depth or location information of the velocity layers to calculate the area of ​​the cross-sectional region represented by each velocity layer, thereby determining its proportion of the total cross-sectional area. For example, numerical integration or discretization methods can be used to divide the entire cross-section into multiple small units, and the number of units covered by each velocity layer can be counted to estimate its area proportion.

[0114] "Calculating the weighted average of the initial velocity distribution based on the weights and the initial velocity distribution" means, after determining the weights of each velocity layer, multiplying the layer velocity of each velocity layer by its corresponding weight, and summing all products to obtain a weighted average that comprehensively reflects the overall characteristics of the initial velocity distribution. This weighted average is more representative of the overall velocity level of the cross-section than a simple arithmetic mean because it considers the different contributions of different regions to the total flow. It can also be calculated by weighted integral of the initial velocity distribution function, where the weight function reflects the proportion of the cross-sectional area.

[0115] In practice, when correcting the boundary conditions and coefficients of the initial velocity distribution based on the weighted average value v_avg and the weighted velocity v_weight, the correction can be based on the condition "if |v_avg - v_weight| > 2%, then the boundary conditions and coefficients of the cubic spline interpolation function are adjusted to make the corrected weighted average value of the velocity distribution consistent with v_weight". Simultaneously, the continuity of the velocity curve during the correction process should be ensured to avoid abrupt changes that do not conform to the flow field laws. Boundary conditions may include velocity values ​​at cross-sectional edges (such as walls), while coefficient correction can adjust the overall size or shape parameters of the velocity distribution.

[0116] The proposed solution first determines the weight of each velocity layer based on its corresponding cross-sectional area proportion, quantifying the actual contribution of each velocity layer to the overall cross-sectional flow rate. This weighting process makes the subsequent average value calculation more physically meaningful, accurately reflecting the overall velocity characteristics of the fluid cross-section. Second, based on these weights and the initial velocity distribution, a weighted average of the initial velocity distribution is calculated, providing a crucial reference benchmark for subsequent correction. This weighted average represents the overall velocity implied by the initial distribution. Subsequently, the proposed solution compares this weighted average of the initial velocity distribution with a weighted velocity independently determined using continuous ultrasonic signals. Given that the weighted velocity typically has higher overall reliability, the proposed solution corrects the boundary conditions and coefficients of the initial velocity distribution based on the difference between the two. This correction is not a simple overall scaling, but rather adjusts key parameters describing the shape and range of the velocity distribution, ensuring that the corrected velocity distribution retains its internal details while its overall weighted average accurately matches the weighted velocity. Ultimately, by ensuring that the weighted average value corresponding to the velocity distribution meets the same condition as the weighted velocity, this solution effectively solves the problem of inconsistency between the initial velocity distribution and the overall flow pattern, and significantly improves the accuracy and reliability of the velocity distribution.

[0117] This application also proposes a system for determining the velocity distribution across a fluid cross-section, such as... Figure 8 As shown, it includes: The static pressure sensor 100 is used to measure the liquid level information corresponding to the target cross-section of the fluid.

[0118] The ultrasonic Doppler sensor 200 is used to send continuous ultrasonic signals to a target section and receive the returned continuous echo signals; to send pulsed ultrasonic signals to the target section based on an interleaved period and receive the returned first pulse echo signal; and to send pulsed ultrasonic signals to the target section based on the first pulse interval time within a continuous period and the second pulse interval time between continuous periods and receive the returned second pulse echo signal.

[0119] Temperature sensor 300 is used to measure the fluid temperature at a target cross-section.

[0120] The processor 400 is used to acquire liquid level information and fluid temperature corresponding to a target cross-section of the fluid; send continuous ultrasonic signals to the target cross-section and determine the weighted flow velocity of the target cross-section based on the returned continuous echo signals; determine the flow measurement mode corresponding to the pulsed ultrasonic signal based on the liquid level information, including staggered periodic wave emission flow measurement mode and a flow measurement mode combining continuous periodic wave emission and phase correlation; if the flow measurement mode is staggered periodic wave emission flow measurement mode, determine the staggered period based on the liquid level information, fluid temperature and weighted flow velocity, send pulsed ultrasonic signals to the target cross-section based on the staggered period, and determine multiple flow velocities of the target cross-section based on the returned first pulse echo signal and fluid temperature. The laminar velocity corresponding to each layer; if the flow measurement method is a combination of continuous periodic wave emission and phase correlation, the first pulse interval time within the continuous period and the second pulse interval time between continuous periods are determined based on the liquid level information, fluid temperature, and weighted flow velocity; pulsed ultrasonic signals are sent to the target section based on the first pulse interval time within the continuous period and the second pulse interval time between continuous periods, and the laminar velocity corresponding to multiple velocity layers of the target section is determined based on the returned second pulse echo signal and fluid temperature; based on the laminar velocity corresponding to multiple velocity layers, the initial velocity distribution of the target section is constructed; the initial velocity distribution is corrected based on the weighted flow velocity to obtain the velocity distribution of the target section.

[0121] As a specific implementation, the static pressure sensor 100, the ultrasonic Doppler sensor 200, and the temperature sensor 300 can be integrated into a "static pressure-ultrasonic flow velocity-temperature" three-in-one sensor, adopting an extremely streamlined design. Specific parameters and structure are as follows: (1) Structural optimization design The probe body adopts a streamlined structure optimized by three-dimensional fluid simulation. The head is a hemispherical shape with a radius of 15mm, the middle is a spindle shape with an aspect ratio of 4:1, and the tail end connects to the support rod with a smooth transition design. The support rod has a diameter of ≤10mm and is coated with a low-friction coefficient coating (friction coefficient ≤0.05). Through this design, the intensity of flow field disturbance generated after the probe enters the fluid is reduced by more than 80%, and the flow state interference error is controlled within ±2%.

[0122] (2) Multi-sensor integration Static pressure sensor: Employs a diffused silicon pressure chip, measuring range 0-10mH2O, accuracy ±0.1%FS, response time ≤1ms, and outputs real-time liquid level data for dynamic adjustment of PW / CW mode parameters; Ultrasonic Doppler sensor: The core is a 4MHz high-frequency ultrasonic transducer, which supports PW and CW dual-mode switching. The transmission power can be dynamically adjusted through real-time gain control (range 5-20dBm). The angle θ between the ultrasonic propagation direction and the water flow direction is fixed at 45° to ensure the consistency of flow velocity measurement. Temperature sensor: PT1000 platinum resistance thermometer, measuring range -20℃ to 80℃, accuracy ±0.1℃, used to compensate for the effect of temperature on the speed of ultrasonic propagation (the speed of ultrasonic propagation in water changes with temperature by approximately 0.2% / ℃).

[0123] (3) Anti-interference and adaptation design Multi-layer acoustic impedance matching technology is employed, with a matching layer (acoustic impedance 3-5×10⁻⁵) placed between the ultrasonic transducer and the protective shell. 6 kg / (m²·s)), increasing ultrasonic transmittance to over 90%; through orthogonal signal correlation technology and noise spectrum estimation algorithm, suppressing random noise generated by bubbles and impurities in the pipeline, improving the signal-to-noise ratio by 30dB; supporting frequency conversion technology (0.5-2MHz adjustable), using low-frequency signals to enhance penetration under low flow rate conditions, and using high-frequency signals to improve resolution under high flow rate conditions.

[0124] In some implementations, the processor 400 may include a CPLD (Complex Programmable Logic Device) and a microcontroller. In PW mode, the CPLD can generate a Barker-coded signal to control the ultrasonic transducer to emit pulsed ultrasonic waves; the CPLD simultaneously completes pulse echo signal sampling, quadrature modulation, and down-conversion processing, and transmits the intermediate frequency signal to the microcontroller; the microcontroller performs complex correlation operations and frequency estimation on the intermediate frequency signal, and calculates the laminar flow velocity in combination with fluid temperature compensation parameters.

[0125] As a specific implementation method, the system operates according to the following process in practical applications: First, the static pressure sensor 100 and temperature sensor 300 acquire the pipe liquid level and fluid temperature in real time; second, the ultrasonic Doppler sensor 200 activates the continuous wave mode to quickly acquire the cross-sectional weighted velocity v_weight; then, the processor 400 automatically selects the flow measurement mode based on the liquid level information, calculates the corresponding parameters, and activates the pulse wave mode measurement; next, the laminar velocity of each velocity layer is calculated based on the returned pulse echo signal; finally, the complete cross-sectional velocity distribution is obtained through interpolation reconstruction and weight correction. For example, in shallow flow conditions with a liquid level of 0.25m, the system adopts an alternating periodic wave emission flow measurement method, calculates T1=0.5ms and T2=0.52ms, and obtains laminar velocity data for 25 velocity layers by alternately emitting pulse waves and processing the echo signals. After cubic spline interpolation and weight correction, a velocity distribution curve conforming to the "fast at the center, slow at the edge" rule is output, with the measurement error controlled within ±3%.

[0126] This application, through its core architecture of "PW mode hierarchical velocity measurement + CW mode weight calibration + flow field algorithm reconstruction," combined with high-sensitivity sensor design and streamlined structure optimization, effectively solves the problems of poor flow field adaptability, limited measurement accuracy, weak data correlation, and significant flow field interference in traditional pipeline flow velocity monitoring technologies. It achieves accurate measurement of cross-sectional flow velocity under all operating conditions, including shallow flow, non-full pipe, and full pipe, providing complete and reliable data support for pipeline flow calculation and flow field analysis.

[0127] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this application can be achieved, and this is not limited herein.

[0128] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0129] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for determining the velocity distribution of a fluid cross-section, characterized in that, include: Acquire the liquid level and fluid temperature corresponding to the target cross-section of the fluid; A continuous ultrasonic signal is sent to the target section, and the weighted flow velocity of the target section is determined based on the returned continuous echo signal; Based on the liquid level information, the flow measurement method corresponding to the pulse ultrasonic signal is determined. The flow measurement method includes an interleaved periodic wave emission flow measurement method and a flow measurement method combining continuous periodic wave emission and phase correlation. If the flow measurement method is an interleaved periodic wave measurement method, the interleaved period is determined based on the liquid level information, the fluid temperature and the weighted flow velocity, a pulsed ultrasonic signal is sent to the target section based on the interleaved period, and the laminar flow velocity corresponding to multiple flow velocity layers of the target section is determined based on the returned first pulse echo signal and the fluid temperature. If the flow measurement method is a flow measurement method combining continuous periodic wave generation and phase correlation, the first pulse interval time within the continuous period and the second pulse interval time between continuous periods are determined based on the liquid level information, the fluid temperature and the weighted flow velocity. Based on the first pulse interval time within a continuous cycle and the second pulse interval time between continuous cycles, pulse ultrasonic signals are sent to the target section, and the laminar flow velocities corresponding to multiple flow velocity layers of the target section are determined based on the returned second pulse echo signal and the fluid temperature. Based on the layer velocities corresponding to the multiple velocity layers, an initial velocity distribution of the target section is constructed; The initial velocity distribution is corrected based on the weighted velocity to obtain the velocity distribution of the target cross section.

2. The method for determining the velocity distribution of a fluid cross-section according to claim 1, characterized in that, Determining the weighted flow velocity of the target section based on the returned continuous echo signal includes: The continuous echo signal is converted into a frequency domain signal, and the frequency shift value corresponding to the peak frequency point in the frequency domain signal is extracted. The frequency shift value is accumulated based on the peak frequency point to obtain the cumulative amplitude corresponding to each peak frequency point; Based on the cumulative amplitude, the maximum local velocity point is determined, and the maximum local velocity point includes the maximum cumulative amplitude and the corresponding target peak frequency point; The direction of water flow corresponding to the maximum local velocity point is determined based on the frequency shift value corresponding to the target peak frequency point. Based on the target peak frequency point, the cumulative amplitude, and the maximum cumulative amplitude, determine the flow velocity start point and flow velocity end point corresponding to the maximum local flow velocity point; Determine the centroid of the flow velocity corresponding to the point of maximum local velocity based on the flow velocity start point and flow velocity end point. The weighted velocity of the target section is determined based on the water flow direction and the cumulative amplitude corresponding to the centroid of the flow velocity.

3. The method for determining the velocity distribution of a fluid cross-section according to claim 1, characterized in that, Determining the flow measurement method corresponding to the pulsed ultrasonic signal based on the liquid level information includes: If the liquid level information indicates that the liquid level is less than or equal to the target liquid level, the flow measurement method corresponding to the pulse ultrasonic signal is determined to be the staggered periodic wave measurement method. If the liquid level information indicates that the liquid level is greater than the target liquid level, the flow measurement method corresponding to the pulse ultrasonic signal is determined to be a flow measurement method combining continuous periodic wave emission and phase correlation.

4. The method for determining the velocity distribution of a fluid cross-section according to claim 1, characterized in that, Determining the staggered period based on the liquid level information, the fluid temperature, and the weighted flow rate includes: The propagation speed of the pulsed ultrasonic signal in the fluid is determined based on the fluid temperature; Based on the liquid level information and the propagation speed, the third pulse interval time is determined; The fourth pulse interval time is determined based on the third pulse interval time, the weighted flow velocity, and the propagation velocity; The interleaving period is obtained based on the third pulse interval time and the fourth pulse interval time.

5. The method for determining the velocity distribution of a fluid cross-section according to claim 4, characterized in that, Determining the laminar flow velocity corresponding to multiple velocity layers of the target section based on the returned first pulse echo signal and the fluid temperature includes: Based on the first pulse echo signal corresponding to the pulsed ultrasonic signal emitted at the third pulse interval, the first phase angle corresponding to the multiple velocity layers of the target section is determined, and the first fluid velocity corresponding to the multiple velocity layers of the target section is determined based on the first phase angle. Based on the first pulse echo signal corresponding to the pulsed ultrasonic signal emitted at the fourth pulse interval, the second phase angle corresponding to the multiple velocity layers of the target section is determined, and the second fluid velocity corresponding to the multiple velocity layers of the target section is determined based on the second phase angle. For each velocity layer of the target cross section, the laminar flow velocity of the velocity layer is determined based on the corresponding first fluid velocity, the corresponding second fluid velocity, and the fluid temperature.

6. The method for determining the velocity distribution of a fluid cross-section according to claim 1, characterized in that, Determining the first pulse interval time within a continuous cycle and the second pulse interval time between continuous cycles based on the liquid level information, the fluid temperature, and the weighted flow rate includes: The propagation speed of the pulsed ultrasonic signal in the fluid is determined based on the fluid temperature; Based on the weighted flow velocity and the propagation speed, the first pulse interval time within the continuous period is determined; Based on the first pulse interval time, the liquid level information, and the propagation speed, the second pulse interval time between consecutive cycles is determined.

7. The method for determining the velocity distribution of a fluid cross-section according to claim 1, characterized in that, Determining the laminar flow velocity corresponding to multiple velocity layers of the target section based on the returned second pulse echo signal and the fluid temperature includes: Based on the second pulse echo signal corresponding to the pulsed ultrasonic signal emitted at the first pulse interval, the third phase angle corresponding to the multiple velocity layers of the target section is determined, and the third fluid velocity corresponding to the multiple velocity layers of the target section is determined based on the third phase angle. Based on the second pulse echo signal corresponding to the pulse ultrasonic signal emitted during the second pulse interval, the fourth phase angle corresponding to the multiple velocity layers of the target section is determined, and the fourth fluid velocity corresponding to the multiple velocity layers of the target section is determined based on the fourth phase angle. For each velocity layer of the target cross section, the laminar flow velocity of the velocity layer is determined based on the corresponding third fluid velocity, the corresponding fourth fluid velocity, and the fluid temperature.

8. The method for determining the velocity distribution of a fluid cross-section according to claim 1, characterized in that, Based on the layer velocities corresponding to the multiple velocity layers, an initial velocity distribution for the target cross section is constructed, including: Interpolating the layer velocities corresponding to multiple velocity layers yields the initial velocity distribution of the target cross section. The initial velocity distribution satisfies the following conditions: the velocity of each velocity layer is the corresponding layer velocity, the velocity between adjacent velocity layers is a cubic polynomial, and the second derivative of the initial velocity distribution is continuous.

9. The method for determining the velocity distribution of a fluid cross-section according to claim 1, characterized in that, The initial velocity distribution is corrected based on the weighted velocity to obtain the velocity distribution of the target cross section, including: The weight of each velocity layer is determined based on the proportion of the cross-sectional area corresponding to each velocity layer. Calculate the weighted average of the initial velocity distribution based on the weights and the initial velocity distribution; The boundary conditions and coefficients of the initial velocity distribution are corrected based on the weighted average value of the initial velocity distribution and the weighted velocity to obtain the velocity distribution of the target cross section; the weighted average value of the velocity distribution and the weighted velocity satisfy the same condition.

10. A system for determining the velocity distribution of a fluid cross-section, characterized in that, include: A hydrostatic sensor is used to measure the liquid level information corresponding to a target cross-section of a fluid. An ultrasonic Doppler sensor is used to send continuous ultrasonic signals to the target cross-section and receive the returned continuous echo signals; and to send pulsed ultrasonic signals to the target cross-section based on an interleaved period and receive the returned first pulse echo signal. Based on the first pulse interval time within a continuous cycle and the second pulse interval time between continuous cycles, pulse ultrasonic signals are sent to the target section, and the returned second pulse echo signals are received. Temperature sensor, used to measure the fluid temperature at a target cross-section; The processor is configured to acquire liquid level information and fluid temperature corresponding to a target cross-section of a fluid; send continuous ultrasonic signals to the target cross-section and determine the weighted flow velocity of the target cross-section based on the returned continuous echo signals; determine the flow measurement mode corresponding to the pulsed ultrasonic signals based on the liquid level information, wherein the flow measurement mode includes an interleaved periodic wave emission flow measurement mode and a flow measurement mode combining continuous periodic wave emission and phase correlation; if the flow measurement mode is an interleaved periodic wave emission flow measurement mode, determine the interleaved period based on the liquid level information, the fluid temperature, and the weighted flow velocity, send pulsed ultrasonic signals to the target cross-section based on the interleaved period, and determine the laminar flow velocity corresponding to multiple flow velocity layers of the target cross-section based on the returned first pulse echo signal and the fluid temperature; if the flow measurement mode is a flow measurement mode combining continuous periodic wave emission and phase correlation, determine the first pulse interval time within the continuous period and the second pulse interval time between continuous periods based on the liquid level information, the fluid temperature, and the weighted flow velocity. Based on the first pulse interval time within a continuous cycle and the second pulse interval time between continuous cycles, pulsed ultrasonic signals are sent to the target cross-section, and the laminar flow velocities corresponding to multiple velocity layers of the target cross-section are determined based on the returned second pulse echo signal and the fluid temperature; based on the laminar flow velocities corresponding to the multiple velocity layers, an initial velocity distribution of the target cross-section is constructed; the initial velocity distribution is corrected based on the weighted velocity to obtain the velocity distribution of the target cross-section.

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