Transition on-line measurement method based on three-layer structure theory of wall surface pulsating pressure spectrum

Abstract

The application discloses a transition online measurement method based on a wall surface pulsating pressure spectrum three-layer structure theory, relates to the boundary layer transition measurement technical field, and the method is based on the turbulent wall surface pulsating pressure spectrum as a benchmark, is divided into a stationary section, a transition section and a decay section from low frequency to dimensionless cutoff frequency in turn, and the wall surface pulsating pressure spectrum three-layer structure theory is proposed; according to the three-layer structure theory, laminar, transition, turbulent wall surface pulsating pressure spectrum is cut off and divided respectively, and the long-time-averaged spectrum slope threshold value is obtained; the spectrum slope of the online measurement data is compared with the spectrum slope threshold value to determine the transition zone, the spectrum slope threshold value is dynamically updated through real-time online measurement of the wall surface pulsating pressure, and stable boundary layer transition zone measurement results are obtained. The method can realize online measurement of the boundary layer transition zone of a navigation body, has good real-time performance and accuracy, and can also respond quickly when the navigation working condition changes and causes the transition position to change.

Description

Technical Field

[0001] This application relates to the field of boundary layer transition measurement technology, and in particular to an online transition measurement method based on the three-layer structure theory of wall pulsating pressure spectrum. Background Technology

[0002] Boundary layer transition flows can cause a surge in wall friction drag, a local increase in wall pulsating pressure, and a sharp increase in wall temperature. Therefore, accurately determining the transition location has always been an important direction in boundary layer flow research.

[0003] Currently, stability theory analysis methods, experimental testing methods, and numerical simulation methods have been developed to determine the boundary layer transition location. However, existing methods have the following shortcomings when applied to determining the boundary layer transition location at the bow of a vehicle: (1) The boundary layer transition at the bow of a vehicle is affected by a pair of contradictory factors: bow stagnation disturbance (promoting transition) and strong down-pressure gradient (inhibiting transition), resulting in a complex transition mechanism. Traditional experimental or numerical judgment methods based on characteristic signals such as the increase in wall friction drag coefficient are difficult to apply effectively in this region. (2) The flow boundary layer around many vehicles has a high Reynolds number (up to 10). 9 The flow characteristics of the vehicle are on the order of magnitude of the ocean and the low Mach number (on the order of 1%), which poses high precision and resource requirements for both numerical calculation and experimental research. Conventional methods are difficult to achieve high-fidelity simulation and measurement. (3) The navigation attitude and navigation environment of the vehicle are complex and variable. Taking the underwater environment as an example, there are influencing factors such as ocean background turbulence, density or temperature stratification, and wall roughness. In the air, it may also be affected by atmospheric turbulence, thermal stratification, etc. Changes in the navigation environment or navigation attitude will affect the transition process and change the transition position to varying degrees. Existing stability theory analysis methods are difficult to fully and in real time consider the above time-varying environmental factors and cannot accurately predict the transient transition position under real working conditions. Summary of the Invention

[0004] To address the aforementioned problems and technical requirements, this application proposes an online transition measurement method based on the three-layer structure theory of wall pulsating pressure spectrum. The technical solution of this application is as follows: An online transition measurement method based on the three-layer structure theory of wall pulsating pressure spectrum, comprising: Based on the turbulent wall pulsating pressure spectrum, determine the frequency range from low frequency to dimensionless cutoff frequency. The spectrum is divided into three segments: a steady segment, a transition segment, and a decay segment, to propose a three-layer structure theory of the wall pulsating pressure spectrum. During the navigation of the vehicle in a fluid medium under the current navigation conditions, the airflow is transmitted through the airflow arranged on the surface of the vehicle. Multiple pulsating pressure sensors synchronously acquire the pulsating pressure on the wall surface; where integer parameters... , Individual pulsating pressure sensor Arranged sequentially along the direction of fluid medium flow; The time-domain signal of the wall pulsating pressure synchronously acquired by each pulsating pressure sensor from the start time to the current measurement time is converted into the pulsating pressure spectrum level generated by the boundary layer flow as a function of the Strouhal number. The varying dimensionless wall pulsating pressure spectrum is analyzed according to a three-layer structure, from low frequency to the dimensionless cutoff frequency. It is divided into the first spectrum band, the second spectrum band, and the third spectrum band in sequence; Based on the relationship between the spectral slope and the spectral slope threshold of the three spectral segments in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor, the boundary layer flow state at the measurement point of each pulsating pressure sensor is determined. The boundary layer flow state includes laminar flow, transition flow, and turbulent flow. The transition zone is determined based on the location of each measuring point at the transition point. When the determined transition zone is inconsistent with the transition zone determined at the previous measurement time, the spectral slope threshold is dynamically updated based on the spectral slope of the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor, and the measurement proceeds to the next measurement time. This process continues until the determined transition zone is consistent with the transition zone determined at the previous measurement time, at which point the boundary layer transition zone measurement result of the vehicle under the current navigation conditions is obtained.

[0005] A further technical solution is that the spectral slope threshold includes at least the spectral slope interval of the third spectral band in the laminar flow state. and the spectral slope range of the third spectral band in turbulent flow and Determining the boundary layer flow state at the location of each pulsating pressure sensor measurement point includes: When flowing along the fluid medium towards the downstream pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The location of the measuring point is in laminar flow, directly determining the pulsating pressure sensor. All upstream pulsating pressure sensor locations are also in laminar flow. When the pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The measurement point is located in turbulent flow, and when the pulsating pressure sensor... Any upstream pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The measuring point is located in a laminar flow environment, when the pulsating pressure sensor... Any upstream pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The measuring point is located in turbulent flow; otherwise, it is determined to be a pulsating pressure sensor. The location of the measuring point is at a transition point; among which, integer parameters ; When the pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum and At that time, determine the pulsating pressure sensor The location of the measuring point is at a transition point, and the pulsating pressure sensor... Any upstream pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor If the measuring point is in laminar flow, then the pulsating pressure sensor should be identified. The location of the measuring point is at a turning point.

[0006] A further technical solution is that the spectral slope threshold also includes a spectral slope threshold for the second spectral segment of the transition state. The transition zone is determined based on the location of each measuring point at the transition point, including: When any pulsating pressure sensor is determined The measuring point is located at a transition point, and the pressure sensor is pulsating. The spectral slope of the second spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The location of the measuring point is in the late transition phase; otherwise, determine the pulsating pressure sensor. The location of the measuring point is in the early transition phase; among which, integer parameters ; The early transition area is determined based on the location of each measuring point in the early transition phase, and the late transition area is determined based on the location of each measuring point in the late transition phase.

[0007] A further technical solution is that the spectral slope threshold also includes the spectral slope interval of the first spectral segment in laminar flow. and the spectral slope interval of the first spectral segment of the turbulent state The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum also includes: When any pulsating pressure sensor is determined The measuring point is located in a laminar flow environment, but pulsating pressure was detected by the sensor. The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum At that time, proceed directly to the next measurement moment; where integer parameters ; When any pulsating pressure sensor is determined The measuring point was located in turbulent water, but pulsating pressure was detected by the sensor. The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum At that time, proceed directly to the next measurement moment; where integer parameters .

[0008] A further technical solution involves dynamically updating the spectral slope threshold based on the spectral slope of the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor, including: The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in laminar flow at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the first spectral segment of the laminar flow state. ; Calculate the spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in turbulence at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the first spectral segment of the turbulent state. ; Determine the spectral slope of the second spectral segment of the dimensionless wall pulsating pressure spectrum for each pulsating pressure sensor in the early transition phase. maximum value And the second spectral segment of the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in the later stage of transition. Minimum value of spectral slope The average value is used to obtain the updated transition state second spectral band spectral slope threshold. ; Calculate the spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in laminar flow at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the third spectral band of the laminar flow state. ; Calculate the spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in turbulence at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the third spectral band of the turbulent state. .

[0009] A further technical solution is that the online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum also includes: Initialize the first spectral band slope interval of the laminar flow state The value range is [-25, -10]; Initialize the spectral slope range of the first spectral segment of the turbulent state. The value range of is [-5, 5]; Initialize the spectral slope threshold of the second spectral segment of the transition state within the range of [-20, -10]. The possible values ​​of ; Initialize the spectral slope range of the third spectral segment in laminar flow. The value range is [-20, -10]; Initialize the spectral slope range of the third spectral segment of the turbulent state. The value range is [-70, -60].

[0010] A further technical solution involves dividing the dimensionless wall pulsating pressure spectrum of the pulsating pressure sensor into a first frequency band, a second frequency band, and a third frequency band, including: The Strouhal number in the dimensionless wall pulsating pressure spectrum measured by the pulsating pressure sensor. lie in The spectral range within the range is divided into the first spectral range, which is used to characterize the contribution of low-frequency large-scale structures in the boundary layer to the wall pulsating pressure. The Strouhal number in the dimensionless wall pulsating pressure spectrum measured by the pulsating pressure sensor. lie in The spectral range within the range is divided into the second spectral range, which is used to characterize the contribution of the intermediate-scale structure of the boundary layer to the wall pulsating pressure. The Strouhal number in the dimensionless wall pulsating pressure spectrum measured by the pulsating pressure sensor. lie in The spectral range within the range is divided into the third spectral range, which is used to characterize the contribution of high-frequency small-scale structures in the boundary layer to the wall pulsating pressure. in, and All are coefficients and .

[0011] A further technical solution involves converting the time-domain signal of the wall pulsating pressure collected by each pulsating pressure sensor into a pulsating pressure spectrum generated by the boundary layer flow, which varies with the Strouhal number. The varying dimensionless wall pulsating pressure spectrum includes: Perform a Fast Fourier Transform and spectrum calculation on the time-domain signal of the pulsating pressure on the wall acquired by each pulsating pressure sensor at the current measurement moment to obtain the pulsating pressure spectrum level as a function of frequency acquired by the wall pulsating pressure sensor. The changing original wall pulsating pressure spectrum; extracting from the original wall pulsating pressure spectrum The part is converted to obtain the pulsating pressure spectrum level generated by the boundary layer flow as a function of the Strouhal number. The varying dimensionless wall pulsating pressure spectrum, and the Strouhal number of the dimensionless wall pulsating pressure spectrum. , Represents the dimensionless cutoff frequency and , It is the cutoff frequency. It is the diameter of the parallel midbody section of the hull, and the unit of measurement is meters. It is the migration velocity of the turbulent boundary layer flow structure, and its value is... And the unit of measurement is meters per second. It is the speed of the ship under the current navigation conditions; Alternatively, a Fast Fourier Transform and spectrum calculation can be performed on the time-domain signal of the wall pulsating pressure acquired by each pulsating pressure sensor at the current measurement moment to obtain the pulsating pressure spectrum level as a function of frequency acquired by the pulsating pressure sensor. The original wall pulsating pressure spectrum changes, and the pulsating pressure spectral level is transformed as a function of the Strouhal number. The changing original dimensionless wall pulsating pressure spectrum; the Strouhal number extracted from the original dimensionless wall pulsating pressure spectrum. The dimensionless wall pulsating pressure spectrum and dimensionless cutoff frequency were obtained from the partial results. The value of is a constant. and .

[0012] Its further technical solution is to determine the cutoff frequency. The methods include: Calculate the integral time scale And obtain the cutoff frequency ;in, It is a pulsating pressure sensor that flows along the fluid medium to the downstream end. Time-domain signal of wall pulsating pressure collected The autocorrelation function, It is an autocorrelation function The moment when it is 0 for the first time; Alternatively, the integral time scale and cutoff frequency can be calculated at multiple speeds to obtain the cutoff frequency. With speed Fitting function ,in, , It is a constant, and its value is... , Substitute the speed of the vehicle under the current navigation conditions into the cutoff frequency. With speed The cutoff frequency at the current speed is obtained from the fitting function. .

[0013] A further technical solution is that the online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum also includes: The eN method based on linear stability theory is used to predict the transition zone of a vehicle traveling in a fluid medium, and the reference transition zone of the vehicle within the design operating parameter range is obtained. Based on the reference transition zone, arrangements are made on the surface of the vehicle body. A pulsating pressure sensor that has completed dynamic calibration. The arrangement area of ​​each pulsating pressure sensor shall at least cover the reference transition area, and the amplitude sensitivity deviation of each pulsating pressure sensor arranged on the surface of the vessel shall not exceed 2% and the phase shift shall not exceed 1° at at least 5 specified octave frequency points, and the response frequency of the pulsating pressure sensor shall not be lower than 20kHz.

[0014] The beneficial technical effects of this application are: This application discloses an online transition measurement method based on the three-layer structure theory of wall pulsating pressure spectrum. This method utilizes multiple pulsating pressure sensors arranged on the wall of the ship to synchronously acquire the time-domain signal of wall pulsating pressure. The dimensionless wall pulsating pressure spectrum generated by boundary layer flow was obtained by fast Fourier transform. Based on the turbulent wall pulsating pressure spectrum, the cutoff frequency of the dimensionless pulsating pressure spectrum was determined. From low frequency to the cutoff frequency, it was divided into a steady segment (first spectrum segment), a transition segment (second spectrum segment), and a decay segment (third spectrum segment), proposing a three-layer structure theory of wall pulsating pressure spectrum. According to this three-layer structure theory, the wall pulsating pressure spectrum of laminar, transition, and turbulent flow was cut off and divided respectively. The long-term average dimensionless wall pulsating pressure spectrum slope threshold was calculated for each, which was used as the initial value for online transition measurement. The spectrum slope of the online measurement data was compared with the spectrum slope threshold. Based on the laminar, transition, and turbulent slope thresholds, the transition zone was determined. By measuring the wall pulsating pressure in real time, the spectrum slope threshold was dynamically updated until a stable boundary layer transition zone measurement result was obtained. This method enables online measurement of the boundary layer transition zone of a vehicle, exhibiting good real-time performance and accuracy. It can also respond quickly when the transition position changes due to changes in the environment or attitude of the vehicle. It provides a technical means for real-time observation of the flow regime of the boundary layer around the vehicle and is also a key criterion for evaluating the effect of boundary layer control delay transition. It fills the technical gap in the field of online real-time measurement of complex shape transition in marine and other multi-parameter environments.

[0015] Because dimensionless wall pulsating pressure spectrum offers the advantages of accurate quantitative measurement of wall pulsating pressure spectrum under different flow regimes without the need for on-site calibration, this method is applicable not only to online measurement of vehicle transition in anaerobic environments such as water, but also to online measurement of vehicle transition in air. Furthermore, the bow structure of the vehicle can be of various shapes, making it widely applicable. This online transition measurement method uses a single type of pulsating pressure sensor, resulting in a simple hardware structure that facilitates practical applications. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating an application scenario of the online transition measurement method in one embodiment of this application.

[0017] Figure 2 This is a flowchart of an online transition measurement method according to one embodiment of this application.

[0018] Figure 3 This is an example of a downstream pulsating pressure sensor calculated at different speeds. The autocorrelation function of the time-domain signal of the wall pulsating pressure, and the downstream pulsating pressure sensor calculated at a certain speed. An enlarged view of the autocorrelation function of the time-domain signal of the wall pulsating pressure.

[0019] Figure 4 yes Figure 3 The most downstream pulsating pressure sensor in the example Original wall pulsating pressure spectrum and corresponding cutoff frequency at different speeds .

[0020] Figure 5 A cutoff frequency in an instance With speed Distribution map and cutoff frequency at different speeds error Distribution map.

[0021] Figure 6 It is another example of the dimensionless cutoff frequency. With speed Distribution diagram and dimensionless cutoff frequency at different speeds error Distribution map.

[0022] Figure 7 It is a typical curve shape of the dimensionless wall pulsating pressure spectrum when the measuring point of the pulsating pressure sensor is in laminar flow, early transition, late transition, or turbulent flow.

[0023] Figure 8It is a graph showing the spectral slope of the dimensionless wall pulsating pressure spectrum when the measuring point of the pulsating pressure sensor is in laminar flow, early transition, late transition, and turbulent flow.

[0024] Figure 9 This is a schematic diagram of the layout of pulsating pressure sensors on the surface of a vehicle in an example, as well as a schematic diagram of the early and late transition regions obtained at a measurement time.

[0025] Figure 10 yes Figure 9 The dimensionless wall pulsating pressure spectrum of the 13 pulsating pressure sensors obtained at this measurement moment in the example.

[0026] Figure 11 In one example, the spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum of a pulsating pressure sensor located at measurement points in laminar, early transition, late transition, and turbulent flow conditions changes with time. The fluctuation curve.

[0027] Figure 12 yes Figure 11 In the example, the spectral slope of the second spectral segment in the dimensionless wall pulsating pressure spectrum of the pulsating pressure sensor at the measuring point locations in the early and late stages of transition varies with time. The fluctuation curve.

[0028] Figure 13 yes Figure 11 In the example, the slope of the first spectral segment in the dimensionless wall-fluid pressure spectrum of the pulsating pressure sensor located at the measurement point in laminar or turbulent flow changes with time. The fluctuation curve.

[0029] Figure 14 yes Figure 9 In the example, the distribution of wall pulsating pressure time domain signals and the steady-state time required to reach steady state at different measuring points of the pulsating pressure sensor when the vehicle is traveling at a speed of 4.5 m / s is shown.

[0030] Figure 15 yes Figure 9 In the example, the root mean square coefficients at different measuring points of the pulsating pressure sensor and the distribution of the steady-state time required to reach steady state are shown.

[0031] Figure 16 yes Figure 9 The example shows a transition zone map obtained by summarizing the boundary layer transition zone measurement results of the vehicle at different speeds. Detailed Implementation

[0032] The specific embodiments of this application will be further described below with reference to the accompanying drawings.

[0033] This application discloses an online transition measurement method based on the three-layer structure theory of wall pulsating pressure spectrum. This method is used to measure the boundary layer transition region of a vehicle traveling in a fluid medium online. This method is not only applicable to the online transition measurement of a vehicle traveling in anaerobic environments such as water, but also applicable to the online transition measurement of a vehicle traveling in air.

[0034] The application scenarios of this online transition measurement method are as follows: Figure 1 As shown, the surface of the hull is decorated with A pulsating pressure sensor, this The pulsating pressure sensors are arranged sequentially along the flow direction of the fluid medium. This application will arrange them sequentially along the flow direction of the fluid medium. The pulsating pressure sensors are sequentially denoted as... In real-world scenarios, the fluid medium typically flows along the length of the vehicle, therefore... The pulsating pressure sensors are typically arranged sequentially along the length of the ship. The parameters are integers, and the number of pulsating pressure sensors is determined to ensure effective online measurement during transition. .like Figure 1 Thirteen pulsating pressure sensors are arranged on the surface of the hull in sequence as follows: For example.

[0035] Electrical connections of the processing module in the aircraft Each pulsed pressure sensor is used as a processing module to execute the online transition measurement method of this application based on the data collected by each pulsed pressure sensor. The electrical connection structure between the pulsating pressure sensor and the processing module is designed according to the actual structure of the aircraft. Figure 1 Taking an underwater vehicle as an example, the processing module 2 is located inside the pressure-resistant shell 4 of the main body 3 of the vehicle. Each pulsating pressure sensor is mounted flat on the wall of the sensor arrangement area 1 of the vehicle. Each pulsating pressure sensor enters the pressure-resistant shell 4 via a sensor signal line 5 through a watertight connector 6 on the pressure-resistant shell 4, and is connected to the processing module 2 via a high-speed data acquisition card 7 inside the main body 3. The processing module 2 can control and collect data. The data from the pulsating pressure sensor is used to perform the online transition measurement method of this application, and the data is stored in a large-capacity hard disk; the processing module 2 is also led out to the outside of the pressure housing 4 via the watertight connector 8 on the pressure housing 4 and connected to the signal transmitter 9 of the sensor arrangement area 1. The processing module 2 is connected to the remote management center via the signal transmitter 9, so that the relevant data of the online transition measurement can be sent to the remote management center.

[0036] In one embodiment, in order to ensure The data acquisition effect of the individual pulsating pressure sensor, in order to Before each pulsating pressure sensor is installed on the surface of the vessel, the following two preprocessing operations are performed: 1. Determine the placement of the pulsating pressure sensor on the surface of the vessel. In one embodiment, the transition region of the vehicle navigating in the fluid medium is first predicted using the eN method based on linear stability theory, obtaining a reference transition region for the vehicle within the design operating parameter range. The eN method is a semi-empirical method for predicting boundary layer transition in low background turbulence based on linear stability theory. The reference transition region predicted by this method can preliminarily determine the transition region of the vehicle within the design operating parameter range. When applying the eN method, the boundary layer disturbance amplitude amplification factor N is set to 6-9. The specific details of the eN method are not elaborated in this embodiment.

[0037] Then, based on the determined reference transition zone, arrangements are made on the surface of the vehicle body. A pulsating pressure sensor, this The pulsating pressure sensors are arranged sequentially along the flow direction of the fluid medium and at least cover the reference transition zone of the vehicle within the design operating parameters range. The spacing between individual pulsating pressure sensors can be determined according to actual needs. The higher the density of pulsating pressure sensors, the higher the measurement resolution, but the greater the amount of data processing required.

[0038] In practice, pulsating pressure sensors are sequentially deployed from the leading edge of the bow of the vessel backwards, covering the area downstream of the reference transition zone. The determined reference transition zone often differs depending on the vessel's design parameters. Furthermore, under actual ocean navigation conditions, factors such as angle of attack or drift angle, acceleration or deceleration, gas-liquid two-phase flow, density or temperature stratification, ocean currents, and subsurface currents all influence the transition location. Therefore, in certain scenarios, The deployment area of ​​a single pulsating pressure sensor is relatively small, for example... Figure 1 The image shown only covers the bow region of the aircraft carrier, but in other scenarios, this... The deployment range of a single pulsating pressure sensor may be quite wide, potentially extending all the way to the parallel midbody section of the vessel.

[0039] 2. Perform dynamic calibration on the pulsating pressure sensor used. Pre-use Each pulsating pressure sensor was dynamically calibrated, and then the calibrated sensors were installed on the surface of the vessel. During the dynamic calibration of each sensor, a square wave or sine wave at a specific octave frequency was used as the input signal to test the amplitude sensitivity and phase shift at that octave frequency. The amplitude sensitivity deviation and phase shift of each sensor at each octave frequency were guaranteed to be no greater than 2%, and the response frequency of each sensor to be no less than 20kHz. At least five octave frequency points were used for dynamic calibration.

[0040] Based on the above application scenarios, the online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum in this application includes the following steps. Please refer to [reference needed]. Figure 2 The flowchart shown: Step 1: During the navigation of the vehicle in the fluid medium under the current navigation conditions, the components arranged on the wall of the vehicle... Each pulsating pressure sensor, according to sampling frequency The synchronous signal is used to acquire the wall pulsating pressure at the measurement point location. The unit of measurement for the wall pulsating pressure is Pa.

[0041] Step 2: The time-domain signal of the wall pulsating pressure synchronously acquired by each pulsating pressure sensor from the start time to the current measurement time is converted into the pulsating pressure spectrum level of the boundary layer flow as a function of the Strouhal number using a fast Fourier transform. The changing dimensionless wall pulsating pressure spectrum.

[0042] The vertical axis of the dimensionless wall pulsating pressure spectrum represents the pulsating pressure spectral level (SPL), with values ​​in dB. The horizontal axis represents the Strouhal number. The Strauhar number It is a dimensionless frequency and the Strouhal number ,in, It represents frequency and the unit is Hz. It is the diameter of the parallel midbody section of the hull, and the unit of measurement is meters. It is the migration velocity of the turbulent boundary layer flow structure and And the unit of measurement is meters per second. It is the speed of the vehicle under the current navigation conditions.

[0043] When converting the time-domain signal of the pulsating wall pressure collected by each pulsating pressure sensor into a dimensionless wall pulsating pressure spectrum, one approach is to first perform a Fast Fourier Transform and spectrum calculation on the time-domain signal of the wall pulsating pressure collected by the pulsating pressure sensor to obtain the pulsating pressure spectrum level as a function of frequency. The changing original wall pulsating pressure spectrum. Then, a truncated portion of the original wall pulsating pressure spectrum is extracted. The part is converted to obtain the pulsating pressure spectrum level generated by the boundary layer flow as a function of the Strouhal number. The varying dimensionless wall pulsating pressure spectrum, and the resulting Strouhal number of the dimensionless wall pulsating pressure spectrum. , Represents the dimensionless cutoff frequency and is equal to the cutoff frequency. The relationship is .

[0044] In the above conversion process, the cutoff frequency needs to be used. The original wall pulsating pressure spectrum was truncated, and The Fourier transform coefficients of the frequency band are set to 0, and then an inverse Fourier transform is performed to obtain the result after removing... The time-domain signal of wall pulsating pressure generated by boundary layer flow with high-frequency interference is obtained from the test of a pulsating pressure sensor. Furthermore, based on the Strouhal number... With frequency The relationship between the truncated wall pulsating pressure spectrum and the dimensionless wall pulsating pressure spectrum is used to convert the truncated wall pulsating pressure spectrum.

[0045] The above conversion process can also output the time-domain signal and spectrum of the wall pulsating pressure generated by the boundary layer flow obtained by the pulsating pressure sensor. Both the time-domain signal and the spectrum of the wall pulsating pressure can be used to help intuitively understand the flow excitation.

[0046] The above conversion process requires the use of a cutoff frequency. To remove high-frequency interference, cut off the frequency. Depending on the speed of the vehicle, this embodiment provides the following methods for determining the cutoff frequency. Method: (1) Method 1, using a pulsating pressure sensor located downstream along the flow of the fluid medium. Time-domain signal of wall pulsating pressure collected Perform autocorrelation calculations to determine the cutoff frequency. ,include: Calculate the pulsating pressure sensor located downstream of the fluid medium. Data collected from the start time to the current measurement time Time-domain signal of wall pulsating pressure autocorrelation function , Indicates time, Indicates calculation Time average, and The numerical units are all seconds.

[0047] Then determine the autocorrelation function. The moment when the first value is 0 (i.e., no correlation). During this period, the autocorrelation function Integrating to obtain the integration time scale :

[0048] Then, based on the integration time scale The cutoff frequency was calculated. .

[0049] When the vehicle travels at different speeds, the pulsating pressure sensor The calculated autocorrelation functions are different, which corresponds to a specific integration time scale. They are also different, and the cutoff frequency calculated from this is... They are also different. In one example, the pulsating pressure sensor calculated at different speeds... Time-domain signal of wall pulsating pressure autocorrelation function like Figure 3 As shown, Figure 3 The pulsating pressure sensor calculated at a single speed is also shown. Time-domain signal of wall pulsating pressure autocorrelation function A magnified view of a section. The cutoff frequencies at different speeds are obtained from this. like Figure 4 As shown, by Figure 4 It can be intuitively seen that, although the cutoff frequency at different speeds... Different, but cutoff frequency It is basically at the inflection point of the original wall pulsating pressure spectrum.

[0050] (2) Method 2, using pre-fitted cutoff frequency With speed Fitting function determines cutoff frequency .

[0051] As mentioned above, cutoff frequency The cutoff frequency varies with the speed of the vehicle and is determined through analysis. If the speed of the vehicle changes linearly, the integral time scale and cutoff frequency are calculated in advance at multiple speeds according to method 1 above, and then the cutoff frequency is obtained by fitting. With speed The fitting function is used to characterize the cutoff frequency at different speeds. Then, the speed of the vehicle under the current navigation conditions is calculated. Substitute the prefitted cutoff frequency With speed From the fitting function, the cutoff frequency under the current navigation conditions can be obtained. .

[0052] In one embodiment, the obtained cutoff frequency With speed The fitting function is ,like Figure 5 As shown, Represents the speed, and the coefficients obtained from the fitting are... , In one example, when the downstream pulsating pressure sensor is located at different dimensionless measuring points, the cutoff frequency calculated according to Method 1 is... With speed Distribution map as follows Figure 5 As shown, Figure 5 The corresponding speed calculated using the fitting function is also shown. Cutoff frequency Compared to the cutoff frequency calculated by method 1 error The error is visible. Stay Within.

[0053] The cutoff frequency is calculated using either method 1 or method 2 described above. Then, the dimensionless wall pulsating pressure spectrum can be obtained by following the above process. Method 2 has slightly lower accuracy and applicability under complex working conditions compared to Method 1, and the obtained cutoff frequency... While method 2 is less accurate than method 1, it eliminates the need to calculate the cutoff frequency using the autocorrelation function each time, allowing for a quick determination of the cutoff frequency at any speed. And the measured error exist Therefore, within the allowable error range, method 2 can be used to quickly calculate the cutoff frequency. .

[0054] As mentioned above, the dimensionless cutoff frequency With cutoff frequency There is an inherent relationship, and the dimensionless cutoff frequency varies when the vehicle is at different speeds. Since the fundamental structure remains unchanged, when converting the time-domain signal of the wall pulsating pressure collected by each pulsating pressure sensor into a dimensionless wall pulsating pressure spectrum, the following method 3 can also be used to obtain the dimensionless wall pulsating pressure spectrum: (3) Method 3: Perform fast Fourier transform and spectrum calculation on the time-domain signal of the wall pulsating pressure collected by each pulsating pressure sensor at the current measurement time to obtain the pulsating pressure spectrum level collected by the pulsating pressure sensor as a function of frequency. After analyzing the changing original wall pulsating pressure spectrum, further analysis was performed based on frequency. With Strauhall The relationship is transformed to obtain the pulsating pressure spectral level as a function of the Strauhal number. The changing original dimensionless wall pulsating pressure spectrum. Then, the predetermined dimensionless cutoff frequency is directly used. Extracting the Strouhal number from the original dimensionless wall pulsating pressure spectrum The dimensionless wall pulsating pressure spectrum and dimensionless cutoff frequency were obtained from the partial results. The value of is a constant. And typical value range .

[0055] In method 3, when the downstream pulsating pressure sensor is located at different dimensionless measuring point positions, the dimensionless cutoff frequency calculated according to method 1 is used. With speed Distribution map as follows Figure 6 As shown, Figure 6 The constant is also shown. Compared to the dimensionless cutoff frequency calculated by method 1 error The error is visible. Stay Within. Method 3 predetermined dimensionless cutoff frequency. While its accuracy and applicability under complex operating conditions are slightly worse than Method 1, Method 3 does not require determining the cutoff frequency through autocorrelation function calculation, nor does it require pre-fitting the cutoff frequency. With speed The fitting function has high transformation efficiency and the measured error is within... Within an acceptable range, this method 3 can also be used to quickly convert and obtain the dimensionless wall pulsating pressure spectrum within the allowable error range.

[0056] And due to the dimensionless cutoff frequency With cutoff frequency There is a transformation relationship, therefore a predetermined dimensionless cutoff frequency is used. The cutoff frequency can be determined by conversion. Using cutoff frequency Following the same operational procedures as Methods 1 and 2, the time-domain signal and spectrum of the wall pulsating pressure generated by the boundary layer flow, obtained from the pulsating pressure sensor, can also be output. Furthermore, the cutoff frequency can be determined intuitively. To visually verify whether the cutoff frequency is at the inflection point of the original wall pulsating pressure spectrum. and the corresponding dimensionless cutoff frequency The rationality of it.

[0057] In addition, to ensure the data acquisition quality of the pulsating pressure sensor, the sampling frequency of the pulsating pressure sensor... Much greater than the cutoff frequency In one embodiment, take .

[0058] Step 3: According to the predetermined three-layer structure of the wall pulsating pressure spectrum, the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor is divided from low frequency to the dimensionless cutoff frequency. It is divided into the first spectrum segment, the second spectrum segment, and the third spectrum segment in sequence.

[0059] When the measuring point of the pulsating pressure sensor is located in different flow states, the curve shape of the converted dimensionless wall pulsating pressure spectrum will differ. For example... Figure 7 The diagram shows typical curve shapes of the dimensionless wall pulsating pressure spectrum at the measuring point location of the pulsating pressure sensor, under laminar, transition (divided into early transition and late transition) and turbulent conditions. Figure 8 This is the corresponding spectral slope curve. Based on the typical characteristics of the dimensionless wall pulsating pressure spectrum as a function of flow regime, this application proposes a three-layer structure theory for the wall pulsating pressure spectrum: using the turbulent wall pulsating pressure spectrum as a benchmark, the frequency from low frequency to the dimensionless cutoff frequency is determined. The spectrum is divided into three segments: a steady segment, a transition segment, and a decay segment. The Strouhal number for this three-layer structure... The upper and lower limits are determined based on the typical curve shape of the dimensionless wall pulsating pressure spectrum in turbulent conditions. Combined with... Figure 7 and Figure 8 The typical curve shape of the dimensionless wall pulsating pressure spectrum under moderate turbulence (hereinafter referred to as the turbulent wall pulsating pressure spectrum), wherein: The stationary segment of the spectrum of fluctuating pressure at the turbulent wall is denoted as the first spectral segment: (e.g.) Figure 7 and Figure 8 As shown, the typical spectrum of fluctuating pressure at the turbulent wall ranges from low frequency to dimensionless frequency. It begins at a plateau, i.e., the spectral slope. Accurate measurement of extremely low frequency spectra requires long-term test data. When the measurement time is short, the obtained spectrum is unstable and unreliable. The specified frequency bands will not be adopted. Therefore, the Strauhal number will be used. lie in The spectral range within the range is defined as the steady segment of the turbulent wall pulsating pressure spectrum. This application simplifies it by describing it as the first spectral segment, which is used to characterize the contribution of low-frequency large-scale structures in the boundary layer to the wall pulsating pressure.

[0060] The transition segment of the turbulent wall pressure spectrum is denoted as the second spectrum segment: (e.g.) Figure 7 and Figure 8 As shown, the turbulent wall pulsating pressure spectrum is in The frequency band transitions from a stationary state to a monotonically decaying state, and is therefore defined as the turbulent wall pulsating pressure spectrum transition segment. This application simplifies it as the second spectrum segment, which is used to characterize the contribution of the intermediate-scale structure of the boundary layer to the wall pulsating pressure.

[0061] The attenuation segment of the turbulent wall pressure spectrum is denoted as the third spectral segment: (e.g.) Figure 7 and Figure 8 As shown, the spectrum of turbulent wall pulsating pressure is from... The spectrum begins to decay rapidly, i.e., the slope of the spectrum. Therefore, Defined as the attenuation segment of the turbulent wall pulsating pressure spectrum, this application simplifies it by describing it as the third spectral segment, which characterizes the contribution of high-frequency small-scale structures in the boundary layer to the wall pulsating pressure. Approaching the dimensionless cutoff frequency At that time, the spectral slope of the turbulent wall pulsating pressure spectrum rose slightly. This indicates that the overall contribution of flow structures with time scales smaller than the integral time scale of the turbulent boundary layer to the wall pulsating pressure is insufficient to accurately capture the contribution of these smaller-scale flow structures to the wall pulsating pressure due to the limitations of the spatial resolution of the sensitive unit of the wall pulsating pressure sensor. Instead, it is reflected in the form of energy superposition on the spectrum curve, resulting in a slight increase in the spectral slope (frequency resolution of 3.33 Hz).

[0062] and All are coefficients and In one instance, take , .

[0063] After dividing the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor into the first, second, and third spectral segments according to the spectral division method indicated by the three-layer structure of the wall pulsating pressure spectrum, the spectral slope of the first spectral segment is further calculated. Spectral slope of the second spectral band Spectral slope of the third spectral band The spectral slopes mentioned above are the overall slopes for the corresponding spectral segments. To achieve a fast solution, the frequency resolution corresponding to these spectral slopes is the frequency band of each layer, i.e., the overall slope of each layer, compared to... Figure 8 The slope at the mid-frequency resolution of 3.33Hz is significantly different. Therefore, the slopes of frequencies without specified frequency resolutions are all overall slopes, and the same applies below.

[0064] Step 4: Based on the relationship between the spectral slope and the spectral slope threshold of the three spectral segments in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor, determine the boundary layer flow state at the measurement point of each pulsating pressure sensor. The boundary layer flow state at the measurement point of each pulsating pressure sensor can be any one of laminar, transitional, or turbulent flow.

[0065] based on Figure 7 It is known that the typical curve shapes of the dimensionless wall pulsating pressure spectrum under various flow regimes differ in the three spectral segments. Based on these differences in typical curve shapes, the range of values ​​for the spectral slope in each spectral segment under various flow regimes can be initialized. In this embodiment, the early and late transition phases are uniformly classified as the transition state. Therefore, the range of values ​​for the spectral slope in the three spectral segments under laminar, transition, and turbulent flow regimes includes: The first spectral band slope range includes the first spectral band slope range for laminar flow. The first spectral segment of the transition state has a spectral slope interval. Spectral slope interval of the first spectral segment in turbulent state . The initial value range is [-25, -10]. The initial value range is [-10, 0]. The initial value ranges from [-5, 5].

[0066] The second spectral band slope range includes the second spectral band slope range for laminar flow. The second spectral band of the transition state has a spectral slope interval. Spectral slope interval of the second spectral band in turbulent state . The initial value range is [-20, -10]. The initial value range is [-25, -5], while The initial value range is [-15, -10]. Furthermore, the initial value range of the second spectral segment slope interval in the early transition phase of the transition state is [-25, -20], and the initial value range of the second spectral segment slope interval in the late transition phase of the transition state is [-10, -5]. Therefore, based on the difference in the value range of the second spectral segment slope interval in the early and late transition phases of the transition state, the transition state second spectral segment slope threshold is initialized within the range of [-20, -10]. The initial value can be set, for example, to -15.

[0067] The third spectral band slope range includes the third spectral band slope range for laminar flow. The spectral slope interval of the third spectral segment of the transition state The spectral slope range of the third spectral band in turbulent flow. . The initial value range is [-20, -10]. The initial value range is [-55, -35]. The initial value range is [-70, -60].

[0068] The above analysis shows that the dimensionless wall pulsating pressure spectrum of different flow regimes exhibits good differentiation in the spectral slope of the third spectral band. Therefore, the spectral slope threshold used in this step should at least include the spectral slope range of the third spectral band for laminar flow. and the spectral slope range of the third spectral band in turbulent flow , .

[0069] In one embodiment, determining the boundary layer flow state at the location of each pulsating pressure sensor measurement point includes the following steps: First, the pulsating pressure sensor, located downstream of the fluid medium, will be... The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum The spectral slope range of the third spectral band in laminar flow and the spectral slope range of the third spectral band in turbulent flow Comparison: (1) When the pulsating pressure sensor The spectral slope of the third spectral segment of the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The measurement point is located in a laminar flow environment. In this case, the pulsating pressure sensor can be directly identified. All upstream pulsating pressure sensors are located at laminar flow points, eliminating the need to compare the spectral slope of other pulsating pressure sensors with the spectral slope threshold.

[0070] (2) When the pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum and At that time, determine the pulsating pressure sensor The location of the measuring point is at a turning point.

[0071] In this case, the pulsating pressure sensor Any pulsating pressure sensor upstream It may be in laminar flow or in transition, therefore further pulsed pressure sensors are needed. The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum The spectral slope range of the third spectral band in laminar flow Comparison: When At that time, determine the pulsating pressure sensor If the measuring point is in laminar flow, then the pulsating pressure sensor should be identified. The location of the measuring point is at a transition point. Among them, integer parameters... .

[0072] (3) When the pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The location of the measuring point is in turbulent flow.

[0073] In this case, the pulsating pressure sensor Any pulsating pressure sensor upstream It may be in laminar, transitional, or turbulent flow, therefore further consideration should be given to the pulsating pressure sensor. The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum and and Comparison: When At that time, determine the pulsating pressure sensor In laminar flow; when At that time, determine the pulsating pressure sensor The location of the measuring point is in turbulent flow; when and At that time, determine the pulsating pressure sensor The transition occurs at the location of the measuring point. Among these, integer parameters... In practical applications, it is often necessary not only to determine the transition zone but also to distinguish between the early and late transition regions in order to identify the area with the strongest transition effect, i.e., the most downstream region of the early transition. Therefore, for integer parameters... That is, for pulsating pressure sensors Any pulse pressure sensor In determining the pulsating pressure sensor When the location of the measuring point is at a transition point, the pulsating pressure sensor will be further distinguished. Whether the location of the measuring point is in the early or late stage of the transition depends on... Figure 7It can be seen that the typical curve shapes in the early and late transition stages show a significant difference in spectral slope in the second spectral band. Therefore, the spectral slope threshold used in this step also includes the spectral slope threshold of the second spectral band in the transition state. Using the spectral slope threshold of the second spectral segment of the transition state We can further distinguish between the early and late stages of transition, including: When the pulsating pressure sensor is determined The measuring point is located at a transition point, and the pressure sensor is pulsating. The spectral slope of the second spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The location of the measuring point is in the late transition phase; otherwise, determine the pulsating pressure sensor. The location of the measuring point is in the early stage of transition.

[0074] In addition Figure 7 It can be seen that the typical curve shapes under laminar and turbulent flow conditions show significant differences in the spectral slope of the first spectral segment. Therefore, the spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum can be used to verify the above results. Thus, the spectral slope threshold used in this step also includes the spectral slope range of the first spectral segment in laminar flow. and the spectral slope interval of the first spectral segment of the turbulent state The verification process includes: When any pulsating pressure sensor is determined The measuring point is located in a laminar flow environment, but pulsating pressure was detected by the sensor. The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum When, it indicates a pulsating pressure sensor If the measurement point is located in laminar flow, the reliability of the detection results is not high. The instability of the results is often due to insufficient data. In this case, there is no need for further operation, and you can directly proceed to the next measurement moment.

[0075] When any pulsating pressure sensor is determined The measuring point was located in turbulent water, but pulsating pressure was detected by the sensor. The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum Similarly, proceed directly to the next measurement moment.

[0076] The spectral slope thresholds used in this step are dynamically updated at each measurement time, and the spectral slope thresholds at the first measurement time can be initialized.

[0077] Step 5: Determine the transition zone based on the location of each measuring point at the transition point.

[0078] Step 4 above can be used to determine the flow regime at the location of each pulsating pressure sensor. According to the flow regime change law, the locations of each measuring point in laminar flow, early transition, late transition, and turbulent flow are arranged sequentially along the flow direction of the fluid medium.

[0079] The area covered by each measuring point at the transition point is extended upstream and downstream along the fluid medium flow direction by a predetermined range to form the transition zone. The upstream and downstream extension range does not exceed the midpoint of adjacent measuring points. Then, it is checked whether the transition zone determined in this step is consistent with the transition zone determined at the previous measurement moment. In practice, the consistency of the two regions can be compared by calculating the intersection-exchange ratio of the two regions, which will not be elaborated in this application.

[0080] In another embodiment, as described in step 4, the spectral slope of the second spectral segment of the transition state can be used to further distinguish between the early transition and the late transition. Therefore, determining the transition region includes determining the early transition region based on the positions of the measurement points in the early transition and determining the late transition region based on the positions of the measurement points in the late transition. Specifically: the area covered by the measurement points in the early transition is extended upstream and downstream along the fluid medium flow direction by a predetermined range to define the early transition region; the area covered by the measurement points in the late transition is extended upstream and downstream along the fluid medium flow direction by a predetermined range to define the late transition region. Furthermore, it is checked whether the early transition phase determined in this step is consistent with the early transition phase determined at the previous measurement time, and whether the late transition phase determined in this step is consistent with the late transition phase determined at the previous measurement time. Only when both the early and late transition phases are consistent with the results at the previous measurement time is it determined that the transition region determined in this step is consistent with the transition region determined at the previous measurement time; otherwise, it indicates that they are inconsistent.

[0081] For example, in one instance, the locations of the 13 pulsating pressure sensors deployed on the surface of the vessel are as follows: Figure 9 As shown, comparison Figure 9 and Figure 1 It can be seen that... Figure 9 In this example, the pulsating pressure sensors are deployed over a wide area, extending to the parallel midbody section of the vessel. In this example, the dimensionless wall pulsating pressure spectra of the 13 pulsating pressure sensors obtained at the current measurement moment are as follows: Figure 10 As shown, the pulsating pressure sensor is determined according to the above method. and The measuring point is located in a laminar flow environment, and the pressure sensor is pulsating. The measuring point is located in the early transition phase, and the pulsating pressure sensor... The measuring point is located in the late transition phase, and the pulsating pressure sensor... The measuring point is located in a turbulent environment, and the location of maximum fluctuating pressure (i.e., the region with the strongest transition effect) is shown by the red dashed line. The early transition region determined by this is as follows: Figure 9 The yellow area in the middle shows the late transition region as follows: Figure 9 As shown in the blue area.

[0082] Step 6: When the determined transition zone is inconsistent with the transition zone determined at the previous measurement time, the spectral slope threshold is dynamically updated according to the spectral slope of the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor and the next measurement time is entered.

[0083] The updated spectral slope threshold in this step includes at least the thresholds used in step 4. , , , , The update methods include: The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in laminar flow at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the first spectral segment of the laminar flow state. .

[0084] The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in turbulent flow at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the first spectral segment of the turbulent state. .

[0085] Determine the spectral slope of the second spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in the early transition phase. maximum value And determine the spectral slope of the second spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in the later stage of transition. minimum value The average of the two values ​​is calculated as the updated transition state second spectral band spectral slope threshold. .

[0086] The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in laminar flow at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the third spectral band of the laminar flow state. .

[0087] The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in turbulent flow at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the third spectral band of the turbulent state. .

[0088] Step 7: When the determined transition zone is consistent with the transition zone determined at the previous measurement moment, the transition zone is considered stable, and the boundary layer transition zone measurement result of the vehicle under the current navigation conditions is finally determined.

[0089] The time interval between two consecutive measurements in this application is on the order of seconds, and the specific value can be customized. For example, the typical value in practical applications is 1 second.

[0090] For example, in one instance, the interval between two adjacent measurement moments is 1 second. The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum of a laminar flow pulsating pressure sensor, measured according to the method provided in this application, is... As time goes by The fluctuation curve, the spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum of the pulsating pressure sensor in the early transition period. As time goes by The fluctuation curve, the spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum of the pulsating pressure sensor in the later stage of transition. As time goes by The oscillation curve, located in the dimensionless wall pulsating pressure spectrum of the turbulent pulsating pressure sensor, shows the spectral slope of the third spectral segment. As time goes by The fluctuation curve, such as Figure 11 As shown. The spectral slope of the second spectral segment in the dimensionless wall pulsating pressure spectrum of a pulsating pressure sensor in the early transition period. As time goes by The fluctuation curve, the spectral slope of the second spectral segment in the dimensionless wall pulsating pressure spectrum of the pulsating pressure sensor in the later stage of transition. As time goes by The fluctuation curve, such as Figure 12 As shown. The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum of a laminar flow pulsating pressure sensor. As time goes by The fluctuation curve, located in the dimensionless wall pulsating pressure spectrum of the turbulent pulsating pressure sensor, shows the spectral slope of the first spectral segment. As time goes by The fluctuation curve, such as Figure 13 As shown.

[0091] Depend on Figures 11-13It can be seen that, because the transition cannot be predicted in advance, and the amount of data in the time-domain signal of the wall pulsating pressure is limited at the initial measurement moment, the spectral slope of each spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor often has errors, and the transition region determined by this is often unstable. However, with the next measurement moment, an additional second of data is added, and thus, as the measurement progresses, the various spectral slope thresholds and transition regions tend to stabilize. And as... Figures 11-13 The results demonstrated show that stable boundary layer transition zone measurements can be obtained within 3-5 seconds, typically within 3 seconds. This measurement speed is exceptionally fast in the field of transition zone measurement. In one embodiment, the stabilization times of the transition zone wall pulsating pressure at a speed of 4.5 m / s (error limit: ±2.3 Pa) and root mean square coefficient (error limit: ±5%) are 28.51 seconds and 8.48 seconds, respectively. The time-domain signals and root mean square coefficients of the wall pulsating pressure at the 13 pulsating pressure sensors are shown below. Figure 14 , Figure 15 As shown. Figure 14 and Figure 15 Location of the dimensionless measuring points of the 13 pulsating pressure sensors The curves are located at 0.00, 0.02, 0.05, 0.07, 0.09, 0.12, 0.14, 0.16, 0.18, 0.21, 0.26, 0.30, and 0.34, respectively. It is the distance between the measuring point of the pulsating pressure sensor and the leading edge of the bow of the aircraft carrier. It is the length of the hull.

[0092] The transition zone can be measured online in real time using the above method, allowing for timely monitoring of its changes. Summarizing the boundary layer transition zone measurements at different speeds within the design speed range yields a transition zone map. This map plots the ship's speed on the ordinate and the location of each pulsating pressure sensor on the abscissa, recording the boundary layer flow regime at each sensor location at different speeds. This transition zone map indicates the changes in boundary layer flow regime at each sensor location at different speeds, facilitating prediction of navigation conditions and providing guidance for predicting and guiding changes in transition position based on environmental changes. For example, based on... Figure 9 The deployment of the pulsating pressure sensors, taking different speeds under different navigation conditions as an example, yields the following transition zone map in one instance: Figure 16 As shown, the x-axis of this transition zone map is taken as... , It is the distance between the measuring point of the pulsating pressure sensor and the leading edge of the bow of the aircraft carrier. It is the length of the hull.

[0093] The above descriptions are merely preferred embodiments of this application, and this application is not limited to the above embodiments. It is understood that other improvements and variations that can be directly derived or conceived by those skilled in the art without departing from the spirit and concept of this application should be considered to be included within the protection scope of this application.

Claims

1. A method for online measurement of transition based on the three-layer structure theory of wall pulsating pressure spectrum, characterized in that, The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum includes: Based on the turbulent wall pulsating pressure spectrum, determine the frequency range from low frequency to dimensionless cutoff frequency. The spectrum is divided into three segments: a steady segment, a transition segment, and a decay segment, to propose a three-layer structure theory of the wall pulsating pressure spectrum. During the navigation of the vehicle in a fluid medium under the current navigation conditions, the airflow is transmitted through the airflow arranged on the surface of the vehicle. Multiple pulsating pressure sensors synchronously acquire the pulsating pressure on the wall surface; where integer parameters... , Individual pulsating pressure sensor Arranged sequentially along the direction of fluid medium flow; The time-domain signal of the wall pulsating pressure synchronously acquired by each pulsating pressure sensor from the start time to the current measurement time is converted into the pulsating pressure spectrum level generated by the boundary layer flow as a function of the Strouhal number. The varying dimensionless wall pulsating pressure spectrum, according to the three-layer structure of the wall pulsating pressure spectrum, is divided from low frequency to the dimensionless cutoff frequency. It is divided into the first spectrum band, the second spectrum band, and the third spectrum band in sequence; Based on the relationship between the spectral slope and the spectral slope threshold of the three spectral segments in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor, the boundary layer flow state at the measurement point of each pulsating pressure sensor is determined. The boundary layer flow state includes laminar flow, transition flow, and turbulent flow. The transition zone is determined based on the location of each measuring point at the transition point. When the determined transition zone is inconsistent with the transition zone determined at the previous measurement time, the spectral slope threshold is dynamically updated based on the spectral slope of the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor, and the measurement proceeds to the next measurement time. This process continues until the determined transition zone is consistent with the transition zone determined at the previous measurement time, at which point the boundary layer transition zone measurement result of the vehicle under the current navigation conditions is obtained.

2. The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum according to claim 1, characterized in that, The spectral slope threshold must include at least the spectral slope range of the third spectral band in laminar flow. and the spectral slope range of the third spectral band in turbulent flow and ; Determining the boundary layer flow state at the location of each pulsating pressure sensor measurement point includes: When flowing along the fluid medium towards the downstream pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The location of the measuring point is in laminar flow, directly determining the pulsating pressure sensor. All upstream pulsating pressure sensor locations are also in laminar flow. When the pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The measurement point is located in turbulent flow, and when the pulsating pressure sensor... Any upstream pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The measuring point is located in a laminar flow environment, when the pulsating pressure sensor... Any upstream pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The measuring point is located in turbulent flow; otherwise, it is determined to be a pulsating pressure sensor. The location of the measuring point is at a transition point; among which, integer parameters ; When the pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum and At that time, determine the pulsating pressure sensor The location of the measuring point is at a transition point, and the pulsating pressure sensor... Any upstream pulsating pressure sensor The spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor If the measuring point is in laminar flow, then the pulsating pressure sensor should be identified. The location of the measuring point is at a turning point.

3. The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum according to claim 2, characterized in that, The spectral slope threshold also includes the spectral slope threshold for the second spectral segment of the transition state. The transition zone is determined based on the location of each measuring point at the transition point, including: When any pulsating pressure sensor is determined The measuring point is located at a transition point, and the pulsating pressure sensor... The spectral slope of the second spectral segment in the dimensionless wall pulsating pressure spectrum At that time, determine the pulsating pressure sensor The measurement point is located in the late transition phase; otherwise, determine the pulsating pressure sensor. The location of the measuring point is in the early transition phase; among which, integer parameters ; The early transition area is determined based on the location of each measuring point in the early transition phase, and the late transition area is determined based on the location of each measuring point in the late transition phase.

4. The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum according to claim 2, characterized in that, The spectral slope threshold also includes the spectral slope interval of the first spectral segment in laminar flow. and the spectral slope interval of the first spectral segment of the turbulent state The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum also includes: When any pulsating pressure sensor is determined The measuring point is located in a laminar flow environment, but pulsating pressure was detected by the sensor. The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum At that time, proceed directly to the next measurement moment; where integer parameters ; When any pulsating pressure sensor is determined The measuring point was located in turbulent water, but pulsating pressure was detected by the sensor. The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum At that time, proceed directly to the next measurement moment; where integer parameters .

5. The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum according to any one of claims 2-4, characterized in that, The spectral slope threshold is dynamically updated based on the spectral slope of the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor, including: The spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in laminar flow at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the first spectral segment of the laminar flow state. ; Calculate the spectral slope of the first spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in turbulence at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the first spectral segment of the turbulent state. ; Determine the spectral slope of the second spectral segment of the dimensionless wall pulsating pressure spectrum for each pulsating pressure sensor in the early transition phase. maximum value And the second spectral segment of the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in the later stage of transition. Minimum value of spectral slope The average value is used to obtain the updated transition state second spectral band spectral slope threshold. ; Calculate the spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in laminar flow at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the third spectral band of the laminar flow state. ; Calculate the spectral slope of the third spectral segment in the dimensionless wall pulsating pressure spectrum of each pulsating pressure sensor in turbulence at the current measurement moment. The range of values ​​formed is used as the updated spectral slope interval for the third spectral band of the turbulent state. .

6. The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum according to any one of claims 2-4, characterized in that, The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum also includes: Initialize the first spectral band slope interval of the laminar flow state The value range is [-25, -10]; Initialize the spectral slope range of the first spectral segment of the turbulent state. The value range of is [-5, 5]; Initialize the spectral slope threshold of the second spectral segment of the transition state within the range of [-20, -10]. The value of ; Initialize the spectral slope range of the third spectral segment in laminar flow. The value range is [-20, -10]; Initialize the spectral slope range of the third spectral segment of the turbulent state. The value range is [-70, -60].

7. The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum according to claim 1, characterized in that, The dimensionless wall pulsating pressure spectrum of the pulsating pressure sensor is divided into three segments: the first segment, the second segment, and the third segment. The Strouhal number in the dimensionless wall pulsating pressure spectrum measured by the pulsating pressure sensor. lie in The spectral range within the range is divided into the first spectral range, which is used to characterize the contribution of low-frequency large-scale structures in the boundary layer to the wall pulsating pressure. The Strouhal number in the dimensionless wall pulsating pressure spectrum measured by the pulsating pressure sensor. lie in The spectral range within the range is divided into the second spectral range, which is used to characterize the contribution of the intermediate-scale structure of the boundary layer to the wall pulsating pressure. The Strouhal number in the dimensionless wall pulsating pressure spectrum measured by the pulsating pressure sensor. lie in The spectral range within the range is divided into the third spectral range, which is used to characterize the contribution of high-frequency small-scale structures in the boundary layer to the wall pulsating pressure. in, and All are coefficients and ; Represents the dimensionless cutoff frequency and , It is the cutoff frequency. It is the diameter of the parallel midbody section of the hull, and the unit of measurement is meters. It is the migration velocity of the turbulent boundary layer flow structure, and its value is... And the unit of measurement is meters per second. It is the speed of the ship under the current navigation conditions.

8. The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum according to claim 1, characterized in that, The time-domain signal of the wall pulsating pressure collected by each pulsating pressure sensor is converted into the pulsating pressure spectrum level generated by the boundary layer flow as a function of the Strouhal number. The varying dimensionless wall pulsating pressure spectrum includes: Perform a Fast Fourier Transform and spectrum calculation on the time-domain signal of the pulsating pressure on the wall acquired by each pulsating pressure sensor at the current measurement moment to obtain the pulsating pressure spectrum level as a function of frequency acquired by the wall pulsating pressure sensor. The changing original wall pulsating pressure spectrum; extracting from the original wall pulsating pressure spectrum The part is converted to obtain the pulsating pressure spectrum level generated by the boundary layer flow as a function of the Strouhal number. The varying dimensionless wall pulsating pressure spectrum, and the Strouhal number of the dimensionless wall pulsating pressure spectrum. , Represents the dimensionless cutoff frequency and , It is the cutoff frequency. It is the diameter of the parallel midbody section of the hull, and the unit of measurement is meters. It is the migration velocity of the turbulent boundary layer flow structure, and its value is... And the unit of measurement is meters per second. It is the speed of the ship under the current navigation conditions; Alternatively, a Fast Fourier Transform and spectrum calculation can be performed on the time-domain signal of the wall pulsating pressure acquired by each pulsating pressure sensor at the current measurement moment to obtain the pulsating pressure spectrum level as a function of frequency acquired by the pulsating pressure sensor. The original wall pulsating pressure spectrum changes, and the pulsating pressure spectral level is transformed as a function of the Strouhal number. The changing original dimensionless wall pulsating pressure spectrum; the Strouhal number extracted from the original dimensionless wall pulsating pressure spectrum. The dimensionless wall pulsating pressure spectrum and dimensionless cutoff frequency were obtained from the partial results. The value of is a constant. and .

9. The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum according to claim 8, characterized in that, Determine the cutoff frequency The methods include: Calculate the integral time scale And obtain the cutoff frequency ;in, It is a pulsating pressure sensor that flows along the fluid medium to the downstream end. Time-domain signal of wall pulsating pressure collected The autocorrelation function, It is an autocorrelation function The moment when it is 0 for the first time; Alternatively, the integral time scale and cutoff frequency can be calculated at multiple speeds to obtain the cutoff frequency. With speed Fitting function ,in, , It is a constant, and its value is... , Substitute the speed of the vehicle under the current navigation conditions into the cutoff frequency. With speed The cutoff frequency at the current speed is obtained from the fitting function. .

10. The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum according to claim 1, characterized in that, The online measurement method for transition based on the three-layer structure theory of wall pulsating pressure spectrum also includes: The eN method based on linear stability theory is used to predict the transition zone of a vehicle traveling in a fluid medium, and the reference transition zone of the vehicle within the design operating parameter range is obtained. Based on the aforementioned reference transition zone, arrangements are made on the surface of the vessel. A pulsating pressure sensor that has completed dynamic calibration. The arrangement area of ​​each pulsating pressure sensor at least covers the reference transition area, and the amplitude sensitivity deviation of each pulsating pressure sensor arranged on the surface of the vessel is no greater than 2% and the phase shift is no greater than 1° at no less than 5 specified octave frequency points, and the response frequency of the pulsating pressure sensor is no less than 20kHz.

Images