A method and model for measuring turbulence intensity of sediment-laden water flow in a sediment environment

Abstract

The present invention discloses a method for measuring the turbulence intensity of sediment-laden water flow in a sediment environment and its model. The model includes a water flow control system and a measurement system. The method includes determining the model input conditions, including the range of values ​​of sediment content and median sediment particle size; debugging and running the model, regulating the water flow control system, and measuring the water depth and flow velocity data of the model section; determining the model experimental conditions based on the uniform flow-turbulent flow-slow flow mode; collecting test data, measuring the pulsating pressure of the water flow at each measuring point; processing the collected test data, and outputting a quantitative index of the turbulence intensity of the sediment-laden water flow. The present invention replaces the pulsating flow velocity with the pulsating pressure as a quantitative index of the turbulence intensity of the sediment-laden water flow, while ensuring the measurement accuracy, not only improving the calculation efficiency, but also breaking through the technical bottleneck of high sediment content and extremely fine sediment particles, and providing certain technical support for conducting physical model test research on the turbulence characteristics of sediment-laden water flow, especially high sediment content water flow.

Description

Technical Field

[0001] The present invention relates to the technical field of water flow turbulence intensity measurement, and in particular to a method and a model for measuring the turbulence intensity of a sediment-laden water flow in a sediment environment. Background Art

[0002] Beyond theoretical derivations, direct observation of water turbulence structures and measurement of their characteristic parameters in laboratory settings through the design or modification of relevant instruments and equipment has long been a focus of turbulence research. As a key parameter of water turbulence characteristics, turbulence intensity is typically quantified using the root mean square (RMS) of the pulsating flow velocity. However, applying traditional methods and equipment to measure water turbulence characteristics in environments with high sediment concentrations and very fine sediment particles still faces the following challenges. For particle image velocimetry, although it avoids the local flow field changes caused by contact measurement, on the one hand, high sand content greatly increases the density of tracer particles in the fluid. It can only be achieved by dividing the image into small areas called windows, using the average velocity in the window as the local flow velocity at the center of the area, and then based on a series of correlation algorithms, finding the window position in the second frame image where the cross-correlation function with a certain window in the first frame image reaches a peak value. The displacement and direction of the peak position relative to the center point of the window in the first frame image are used as a substitute for the average displacement and direction of the particles in the window. This processing method greatly reduces the computational efficiency and accuracy of the processing; on the other hand, the acoustic Doppler velocimeter is easily damaged in a high sand content environment, and will also cause disturbances to the local flow field of the sand-laden water flow, affecting the test measurement results.

[0003] Therefore, in order to study the measurement method and model of the turbulence intensity of sediment-laden water flow in high sand content and extremely fine sediment environment, a method and model for measuring the turbulence intensity of sediment-laden water flow in sediment environment were designed. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem of measuring the turbulence intensity of water flow under laboratory conditions of high sand content and extremely fine sand particles. A method and model for measuring the turbulence intensity of sand-laden water flow in a sediment environment are proposed. The pulsating pressure of the sand-laden water flow is used as a quantitative indicator of turbulence intensity. While ensuring measurement efficiency and accuracy, the measurement is automated to avoid interference with the measurement results caused by human operation. It also breaks through the technical bottleneck of sand content and sediment particle size range in the process of measuring the turbulence intensity of sand-laden water flow, and can provide technical support for basic research on sediment movement mechanics in physical model experiments.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for measuring the turbulence intensity of a sediment-laden water flow in a sediment environment comprises the following steps:

[0007] Step S1: Determination of model input conditions, including the range of sediment content and median sediment particle size;

[0008] Step S2: Model debugging and operation, regulating the water flow control system, and measuring the water depth and flow velocity data of the model section;

[0009] Step S3: determining the model experimental conditions based on the uniform flow-turbulent flow-slow flow pattern;

[0010] Step S4: collecting test data and measuring the water flow pulsating pressure at each measuring point;

[0011] In step S5, the collected test data are processed to output a quantitative index of the turbulence intensity of the sediment-laden water flow.

[0012] As a further solution of the present invention, in step S1, the determination of the model input conditions includes the sediment content S and the median particle size D of the sediment. 50 The value range of is as follows:

[0013] Step S11, sediment median particle size D 50 The value range of: 0<D 50 ≤0.5mm, the value range of sand content S: 0<S≤500kg / m 3 , the sediment content S and the median particle size D of the sediment in a single group of model tests 50 For constant conditions, the model input conditions in each group of experiments are determined by giving the sediment content and the step size of the median sediment particle size change, which can be expressed as follows:

[0014] S+(i-1)×ΔS

[0015] D 50 +(i-1)×ΔD 50

[0016] Among them, S represents the sediment content, i represents the i-th test group of the model, ΔS represents the change step of the sediment content, and D 50 Indicates the median particle size of sediment, ΔD 50 Indicates the change step size of the median particle size of sediment;

[0017] In step S12, according to the median particle size of the sediment in the model input conditions, prototype sand is screened using a sieve to prefabricate experimental sand, a particle size analyzer is used to analyze and draw a particle size gradation curve of the experimental sand, and the median particle size of the sediment in the experimental sand required by the model input conditions is obtained through the particle size gradation curve. According to the sand content in the model input conditions, the above-mentioned test sand and clean water are added to the turbid water stirring tank, and stirred to prepare turbid water that meets the experimental requirements.

[0018] As a further solution of the present invention, in step S2, debugging the water flow control system of the model includes the following steps:

[0019] In step S21, based on the model input conditions, the model flow rate and tailgate opening are adjusted through the water flow control system, and the entire model is tested;

[0020] In step S22, after the sediment-laden water flow entering the model becomes stable, the measurement system is used to measure the cross-sectional water depth and flow velocity data of the open channel flume during the trial operation of the model.

[0021] As a further solution of the present invention, in step S3, based on the uniform flow-turbulent flow-slow flow mode determination model experimental conditions, the determination of the uniform flow-turbulent flow-slow flow mode includes the following steps:

[0022] In step S31, based on the water depth and velocity data of the model section in step S2, the following formulas are used to calculate the Froude number Fr, Reynolds number Re, and along-the-line gradient J of the sediment-laden flow during the model trial run:

[0023]

[0024] Re=vR / η

[0025]

[0026] Where v is the flow velocity of the open channel flume section, R is the hydraulic radius of the river, which is the ratio of the cross-sectional area of ​​the open channel flume to the wetted perimeter of the flume; g is the acceleration of gravity, h is the water depth of the open channel flume section, η is the viscosity coefficient of the clear water flow, and h is the water viscosity coefficient of the clear water flow. i represents the water level reading of the i-th water level gauge, n g Indicates the total number of water level gauges, Δl g Indicates the distance between adjacent water level gauges;

[0027] Step S32: Based on the calculation results of the Froude number, Reynolds number, and the gradient along the flow path, determine whether the current water flow satisfies the uniform flow-turbulent flow-slow flow mode. When the gradient along the flow path remains unchanged and is equal to the slope of the open channel flume, the sediment-laden flow is determined to be uniform flow; when the Reynolds number is greater than 10,000, the sediment-laden flow is determined to be turbulent flow; when the Froude number is less than 1, the sediment-laden flow is determined to be slow flow.

[0028] In step S33, if the uniform flow-turbulent flow-slow flow mode condition is met in step S32, step S4 is performed; if not, step S2 is returned to, and the model flow rate and tailgate opening are adjusted again through the water flow control system.

[0029] As a further solution of the present invention, in step S4, the collection of test data includes the following steps:

[0030] In step S41, after the sediment-laden water flow in the model stabilizes and meets the uniform flow-turbulent flow-slow flow mode conditions, the instantaneous value of the water flow pulsating pressure at the initial measuring point is recorded in real time by the measurement system and a curve of the instantaneous value change is drawn. The sampling time for a single measuring point is 60 seconds, and the recording is repeated three times within the sampling time;

[0031] In step S42, a sediment content measuring device is used to record the change in the sediment content of the sediment-laden water flow in real time. If the sediment content remains substantially unchanged during the measurement process, step S43 is performed. If the sediment content decreases significantly during the measurement process, corresponding adjustments are made by adding sediment to the muddy water mixing tank.

[0032] In step S43, after the collection of the water flow pulsation pressure data at the measuring point is completed, the process moves to the next measuring point and returns to step S41. If the data of all measuring points have been collected, the process proceeds to step S51.

[0033] As a further solution of the present invention, in step S43, the movement of the measuring point follows the order of the z-axis, y-axis and x-axis of the open channel flume, and the operation steps are as follows:

[0034] Step a, keeping the x-axis and y-axis coordinates unchanged, move the water flow pulsation pressure sensor along the z-axis at equal intervals Δz until it reaches its maximum value along the z-axis;

[0035] Step b: Keeping the x-axis coordinate unchanged, move the water flow pulsation pressure sensor along the y-axis at equal intervals of Δy to the measuring point (x0, y0 + Δy, z0), repeat step a, then move the water flow pulsation pressure sensor along the y-axis at equal intervals to the measuring point (x0, y0 + 2Δy, z0), and repeat step a until the y-axis direction is maximum;

[0036] Step c, keep the y-axis and z-axis coordinates unchanged, move the water flow pulsation pressure sensor at equal intervals Δx along the x-axis to the measuring point (x0+Δx, y0, z0), repeat steps a and b, then move the water flow pulsation pressure sensor at equal intervals along the x-axis to the measuring point (x0+2Δx, y0, z0), repeat steps a and b, until the x-axis direction is maximum.

[0037] As a further solution of the present invention, in step S5, the collected test data is processed to output a quantitative index of the turbulence intensity of the sediment-laden water flow, which describes the change in the turbulence intensity of the sediment-laden water flow in all directions of the open channel flume, including the following steps:

[0038] In step S51, the water flow pulsation pressure value at each measuring point is calculated according to the actual measurement results of the water flow pulsation pressure sensor. The water flow pulsation pressure is defined as the instantaneous pressure P of the water flow. i The mean pressure at the same time The difference between the two values ​​is calculated by calculating the root mean square of the water flow pulsation pressure value over a period of time as a quantitative index of the turbulence intensity of the sediment-carrying water flow σP :

[0039]

[0040] Where, P i For [T star , T end ] is the instantaneous pressure of the sediment-carrying water flow at the i-th moment in the time period, M is the number of measured instantaneous pressure data in the time period, T star and T end Indicates the start and end time of measurement sampling;

[0041] In step S52, based on the calculation results of step S51, the turbulence intensity changes of the sediment-laden water flow along the vertical, horizontal and vertical directions of the open channel flume are counted and output:

[0042] On the vertical line of the open channel flume, the mean value of the turbulence intensity of the sediment-carrying water flow at all measuring points with the same x-axis and y-axis coordinates is taken to describe the change of the turbulence intensity of the sediment-carrying water flow at that point along the z-axis direction;

[0043] In the horizontal direction of the open channel flume, the mean value of the turbulence intensity of the sediment-carrying water flow at all measuring points with the same x-axis and z-axis coordinates is taken to describe the change of the turbulence intensity of the sediment-carrying water flow at that point in the open channel flume along the y-axis direction;

[0044] In the longitudinal direction of the open channel flume, the average value of the turbulence intensity of the sediment-carrying water flow of all measuring points with the same z-axis and y-axis coordinates is taken to describe the change of the turbulence intensity of the sediment-carrying water flow at that point in the open channel flume along the x-axis direction.

[0045] A model for measuring the turbulence intensity of sediment-laden water flow in a sediment environment, the model comprising:

[0046] The water flow control system includes muddy water mixing tank, central control room, muddy water inlet pipe, fore pool, water stabilization grid, tail gate, muddy water outlet pipe and open channel flume; among them,

[0047] The muddy water mixing tank is located on one side of the open channel flume. A water stabilizing grille is provided in the front area of ​​the open channel flume. The area enclosed between the water stabilizing grille and the front side wall of the open channel flume is the forebay. The forebay is connected to one end of the muddy water inlet pipe, and the other end of the muddy water inlet pipe is connected to the muddy water mixing tank. A tail gate is provided at the rear of the open channel flume, and the tail gate is connected to the central control room to establish a control connection for the opening and closing angle. The two ends of the muddy water discharge pipe are respectively connected to the rear of the open channel flume and the muddy water mixing tank.

[0048] The measurement system includes a sediment content meter, a mobile measuring bridge, a temperature sensor, a water level gauge, and a water flow pulsation pressure sensor; among which,

[0049] The sediment content meter is installed in the muddy water mixing tank and in the front and tail of the open channel flume. The mobile measuring bridge is set above the open channel flume and moves horizontally in the direction of the open channel flume. The lower end of the mobile measuring bridge is fixedly installed with a water flow pulsation pressure sensor. Several water level gauges are arranged at equal intervals on the inner wall of the open channel flume, and a temperature sensor is fixed on the inner wall of the flume in the middle.

[0050] As a further solution of the present invention, the water flow pulsation pressure sensor is connected to the pressure transmitter by wire, the pressure transmitter is connected to the signal test and analysis unit by wireless transmission, the temperature sensor and water level meter are connected to the signal receiver by wireless communication, and the signal receiver establishes a wired connection with the data acquisition unit.

[0051] As a further solution of the present invention, the movable measuring bridge includes a horizontal threaded connecting rod, a vertical threaded connecting rod, a rotating handle and a rotating screw, the horizontal threaded connecting rod is threadedly connected to a movable platform, the vertical threaded connecting rod is threadedly connected to a side platform of the movable platform, the upper end of the vertical threaded connecting rod is inserted with the rotating screw, and the lower end is fixedly installed with the water flow pulsation pressure sensor; bearing bases are provided at both ends of the horizontal threaded connecting rod, and the bearing base is installed on the bridge frame, one end of the horizontal threaded connecting rod passes through the bearing base and is fixedly connected to the rotating handle, limit rods are symmetrically provided on both sides of the horizontal threaded connecting rod, the limit rod passes through the platform body of the movable platform, and its two ends are fixed on the bridge frame, and a roller is provided at the lower part of the movable measuring bridge, the roller is rotatably installed at the lower part of the bridge frame, and is rollingly set on the water trough track, and the water trough track is installed on the upper end surface of the open channel water trough.

[0052] Compared with the prior art, the beneficial effects of the present invention are: the present invention solves the problem of measuring the turbulence intensity of water flow under laboratory conditions of high sand content and extremely fine sand particles. Compared with traditional water flow turbulence characteristic parameter measurement equipment or methods, the present invention replaces the pulsating flow velocity with the pulsating pressure as a quantitative indicator of the turbulence intensity of the sand-laden water flow, breaking through the limitations of low sand content and coarse sand particles in the water flow turbulence measurement process under traditional laboratory conditions. The automated measurement method of using the measurement system to monitor parameter data ensures measurement efficiency and accuracy while avoiding the influence of human interference on the measurement results, taking into account the measurement accuracy and efficiency of the model, and has strong practicality for the physical model test research of the turbulence characteristics of sand-laden water flow, especially high sand content water flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a flow chart of the method for measuring the turbulence intensity of sediment-laden water flow in a sediment environment proposed by the present invention;

[0054] Figure 2A schematic diagram of the relationship between the model settings of the method for measuring the turbulence intensity of sediment-laden water flow in a sediment environment proposed by the present invention;

[0055] Figure 3 A schematic cross-sectional view of an open channel flume model for the method for measuring turbulence intensity of sediment-laden water flow in a sediment environment proposed by the present invention;

[0056] Figure 4 This is a schematic diagram of the structure of a mobile measuring bridge of a model of the method for measuring the turbulence intensity of sediment-laden water flow in a sediment environment proposed by the present invention;

[0057] Figure 5 This is a schematic diagram of the measurement results of the instantaneous pressure of the sediment-laden water flow in the sediment environment according to the method for measuring the turbulence intensity of the sediment-laden water flow proposed in the present invention.

[0058] The numbers in the figure are: 1. Muddy water mixing tank; 2. Sediment content measuring device; 3. Central control room; 4. Muddy water inlet pipe; 5. Forebay; 6. Water stabilizing screen; 7. Tail gate; 8. Muddy water outlet pipe; 9. Open channel flume; 10. Mobile measuring bridge; 11. Temperature sensor; 12. Flume track; 13. Roller; 131. Bridge; 132. Bearing base; 14. Horizontal threaded connecting rod; 141. Limit rod; 15. Vertical threaded connecting rod; 151. Moving platform; 16. Rotating handle; 17. Rotating screw; 18. Water level gauge; 19. Signal receiver; 20. Data acquisition unit; 21. Water flow pulsation pressure sensor; 22. Pressure transmitter; 23. Signal test and analysis unit. DETAILED DESCRIPTION

[0059] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0060] Sediment movement in natural rivers is closely related to water turbulence. Fluctuations in velocity and pressure near the bed surface, as well as the exchange of upper and lower water masses caused by water turbulence, are generally considered to be factors influencing the initiation and diffusion of suspended sediment. Conversely, the presence of sediment can alter the turbulent structure of the flow. However, the turbulence-enhancing and -restricting effects of sediment concentration and particle size on sediment-laden flows remain controversial, and further research is needed to understand how turbulence intensity varies with sediment concentration and particle size. Therefore, studying the turbulent characteristics of sediment-laden flows has long been a research focus in sediment mechanics, providing the foundation for solving fundamental problems in sediment mechanics. It also holds important theoretical guidance for the management of sediment-laden river channels and ecological and environmental protection.

[0061] With the development of computer and high-speed photography technology, the main methods currently used to quantify the parameters of water turbulence characteristics can be divided into two categories: contact and non-contact measurement. The two main categories are particle image velocimetry (PIV or PTV) and acoustic Doppler velocimetry (ADV). The former refers to a series of particle image velocimetry techniques, including PIV and PTV. By dispersing markers in the fluid and applying image processing and analysis techniques, the displacement of the markers within a certain time interval is determined, i.e., the instantaneous velocity at each point in the flow field. The latter, laser velocimeters, are often used in conjunction with computer data processing systems. In conditions with low sediment concentrations, they can simultaneously determine the time-averaged velocity, the mean square value of the pulsating velocity, and the pulsating velocity itself. However, these technical solutions significantly reduce the accuracy and efficiency of measuring the turbulence intensity of sediment-laden water flows in environments with high sediment concentrations and very fine sediment particles.

[0062] For the measurement of turbulence intensity of sediment-laden water flow in high-sand and very fine-grained sediment environments, a simpler operation method is proposed in this embodiment. This method measures the turbulence intensity of sediment-laden water flow in a sediment environment, uses the pulsating pressure of the sediment-laden water flow as a quantitative indicator of turbulence intensity, and describes the changes in the turbulence intensity of the sediment-laden water flow. Specifically, the method for measuring the turbulence intensity of sediment-laden water flow in a sediment environment is described in detail. Figure 1 , the method mainly includes the following steps:

[0063] Step S1: Determination of model input conditions, including the range of sediment content and median sediment particle size;

[0064] Step S2: Model debugging and operation, regulating the water flow control system, and measuring the water depth and flow velocity data of the model section;

[0065] Step S3: determining the model experimental conditions based on the uniform flow-turbulent flow-slow flow pattern;

[0066] Step S4: collecting test data and measuring the water flow pulsating pressure at each measuring point;

[0067] In step S5, the collected test data are processed to output a quantitative index of the turbulence intensity of the sediment-laden water flow.

[0068] In step S1, the model input conditions are determined, including the sediment content S and the median sediment particle size D 50 The value range of is as follows:

[0069] Step S11, sediment median particle size D 50 The value range of: 0<D 50 ≤0.5mm, the value range of sand content S: 0<S≤500kg / m 3The range of values ​​is determined based on the following considerations: on the one hand, the median particle size of suspended sediment in natural rivers is between 0.062 mm and 0.5 mm; on the other hand, high-sediment-laden water flows must have a sediment content greater than 200 kg / m3, while the maximum sediment content in the history of the Yellow River's main and tributary rivers does not exceed 1000 kg / m3.

[0070] Sediment content S and sediment median particle size D in a single group of model tests 50 The conditions are constant. Therefore, after determining the range of the above-mentioned sediment content and sediment median particle size conditions, the model input conditions in each group of experiments are determined by giving the change step of sediment content and sediment median particle size respectively, which can be expressed by the following formula:

[0071] S+(i-1)×ΔS

[0072] D 50 +(i-1)×ΔD 50

[0073] Among them, S represents the sediment content, i represents the i-th test group of the model, ΔS represents the change step of the sediment content, and D 50 Indicates the median particle size of sediment, ΔD 50 Indicates the change step size of the median particle size of sediment.

[0074] In step S12, according to the median sediment particle size in the model input conditions, prototype sand is screened using a sieve to preform experimental sand. A particle size analyzer is used to analyze and plot a particle size gradation curve for the experimental sand. This curve describes the trend of the ratio of the number of sediment particles larger than a certain particle size to the total number of sediment particles as a function of particle size. The particle size gradation curve is used to obtain the median sediment particle size of the experimental sand required by the model input conditions to ensure that its median sediment particle size meets the requirements of the model input conditions. According to the sediment content in the model input conditions, the above-mentioned test sand and clean water are added to the muddy water mixing tank 1 and stirred to prepare muddy water that meets the sediment content input conditions corresponding to the experimental requirements.

[0075] In step S2, the debugging of the water flow control system of the model includes the following steps:

[0076] In step S21, based on the model input conditions, the model flow rate Q and the tailgate 7 opening a0 are adjusted through the water flow control system, and the entire model is tested. Under the same flow rate, the larger the tailgate 7 opening a0 is, the lower the model water level is.

[0077] In step S22, after the sediment-laden water flow entering the model becomes stable, the measurement system is used to measure the cross-sectional water depth h, flow velocity v, and water temperature t of the open channel flume 9 during the trial operation of the model.

[0078] In step S3, the model experimental conditions are determined based on the uniform flow-turbulent flow-slow flow mode. The determination of the uniform flow-turbulent flow-slow flow mode includes the following steps:

[0079] In step S31, based on the water depth and velocity data of the model section in step S2, the following formulas are used to calculate the Froude number Fr, Reynolds number Re, and along-the-line gradient J of the sediment-laden flow during the model trial run:

[0080]

[0081] Re=vR / η

[0082]

[0083] Where v is the flow velocity of the open channel flume (v = Q / hB, B is the width of the open channel flume), R is the hydraulic radius of the river, which is the ratio of the cross-sectional area of ​​the open channel flume to the wetted perimeter of the flume, that is, hB / (2h+B); g is the acceleration of gravity, h is the water depth of the open channel flume, and η is the viscosity coefficient of the clear water flow. h i represents the water level reading of the i-th water level gauge, n g Indicates the total number of water level gauges, Δl g Indicates the distance between adjacent water level gauges.

[0084] In step S32, based on the calculation results of the Froude number Fr, the Reynolds number Re and the along-the-channel gradient J, it is determined whether the current water flow satisfies the uniform flow-turbulent flow-slow flow mode. When the along-the-channel gradient J remains unchanged and is equal to the slope of the open channel flume 9, the sand-carrying water flow is determined to be a uniform flow; when the Reynolds number Re is greater than 10,000, the sand-carrying water flow is determined to be a turbulent flow; when the Froude number Fr is less than 1, the sand-carrying water flow is determined to be a slow flow.

[0085] Step S33: If the conditions of the uniform flow-turbulent flow-slow flow mode are met in step S32, then step S4 (step S41) is performed; if not, then step S2 (step S21) is returned to, and the model flow Q and the tailgate 7 opening a0 are re-adjusted through the water flow control system until the model operation state reaches the uniform flow-turbulent flow-slow flow mode.

[0086] In step S4, the collection of test data includes the following steps:

[0087] In step S41, after the sediment-laden water flow in the model is stable and satisfies the uniform flow-turbulent flow-slow flow mode conditions, the instantaneous value of the water flow pulsation pressure at the initial measuring point X0 = (x0, y0, z0) (where x0, y0, z0 are the coordinate values ​​of the length, width and depth along the open channel flume 9, respectively) is recorded in real time by the measurement system and a curve of the instantaneous value change is drawn (e.g. Figure 5The curve is shown in Figure 1, which shows the instantaneous pressure of the sediment-laden water flow at a certain moment in time at the measuring point. The sampling time for a single measuring point is 60 seconds, and the data are recorded three times within the sampling time.

[0088] In step S42, the sediment content measuring device 2 is used to record the changes in the sediment content of the sediment-laden water flow in real time. If the sediment content remains basically unchanged during the measurement process, step S43 is performed. If the sediment content decreases significantly during the measurement process, corresponding adjustments are made by adding sediment to the muddy water stirring tank 1.

[0089] In step S43, after the collection of the water flow pulsation pressure data at the measuring point is completed, the process moves to the next measuring point and returns to step S41. If the data of all measuring points have been collected, the process proceeds to step S51.

[0090] The movement of the measuring point follows the order of the z-axis, y-axis, and x-axis of the open channel flume. The operation steps are as follows:

[0091] Step a: Keeping the x-axis and y-axis coordinates unchanged, move the water flow pulsation pressure sensor 21 along the z-axis at equal intervals Δz until the z-axis reaches its maximum value;

[0092] Step b: Keeping the x-axis coordinate unchanged, move the water flow pulsation pressure sensor 21 along the y-axis at equal intervals Δy to the measuring point (x0, y0+Δy, z0), repeat step a, then move the water flow pulsation pressure sensor 21 along the y-axis at equal intervals to the measuring point (x0, y0+2Δy, z0), and repeat step a until the y-axis direction is maximum;

[0093] Step c, keep the y-axis and z-axis coordinates unchanged, move the water flow pulsation pressure sensor 21 along the x-axis at equal intervals Δx to the measuring point (x0+Δx, y0, z0), repeat steps a and b, then move the water flow pulsation pressure sensor 21 along the x-axis at equal intervals to the measuring point (x0+2Δx, y0, z0), repeat steps a and b, until the x-axis direction is maximum.

[0094] In step S5, the collected test data is processed to output a quantitative index of the turbulence intensity of the sediment-laden water flow, describing the change in the turbulence intensity of the sediment-laden water flow in each direction of the open channel flume 9, including the following steps:

[0095] In step S51, the water flow pulsation pressure value at each measuring point is calculated according to the actual measurement results of the water flow pulsation pressure sensor 21. The water flow pulsation pressure is defined as the instantaneous pressure P of the water flow. i The mean pressure at the same time The difference between the two values ​​is calculated by calculating the root mean square of the water flow pulsation pressure value over a period of time as a quantitative index of the turbulence intensity of the sediment-carrying water flow σ P According to the instantaneous pressure data of the sediment-carrying water flow measured in step S41, a length of [Tstar , T end ]The data contained in the time period (such as Figure 5 As shown in the figure), the turbulence intensity σ of the sediment-carrying water flow at each measuring point is calculated according to the following formula P :

[0096]

[0097] Where, P i For [T star , T end ] is the instantaneous pressure of the sediment-carrying water flow at the i-th moment (i=1,2,...,M) in the time period, M is the number of measured instantaneous pressure data in the time period, M=(T end -T star )×f, f is the output frequency of the water flow pulsation pressure sensor; T star and T end Indicates the start and end times of the measurement sampling. Since the instantaneous pressure of the sediment-carrying flow was measured three times at each measuring point in step S41, the turbulence intensity of the sediment-carrying flow at each measuring point is the average of these three measurements. In this way, the turbulence intensity of the sediment-carrying flow is calculated for all measuring points.

[0098] In step S52, based on the calculation results of step S51, the turbulence intensity changes of the sediment-laden water flow along the vertical, horizontal and vertical directions of the open channel flume 9 are counted and outputted:

[0099] On the vertical line of the open channel flume 9, the mean value of the turbulence intensity of the sediment-carrying water flow of all measuring points with the same x-axis and y-axis coordinates (e.g., x=x0, y=y0) is taken to describe the change of the turbulence intensity of the sediment-carrying water flow along the z-axis at the point (x0, y0);

[0100] In the horizontal direction of the open channel flume 9, the average value of the turbulence intensity of the sediment-carrying water flow at all measuring points with the same x-axis and z-axis coordinates is taken to describe the change of the turbulence intensity of the sediment-carrying water flow at that point in the open channel flume 9 along the y-axis direction;

[0101] In the longitudinal direction of the open channel flume 9, the average value of the turbulence intensity of the sediment-carrying water flow of all measuring points with the same z-axis and y-axis coordinates is taken to describe the change of the turbulence intensity of the sediment-carrying water flow at that point in the open channel flume 9 along the x-axis direction.

[0102] Based on the above-mentioned method for measuring the turbulence intensity of sediment-laden water flow in a sediment environment, this embodiment further proposes a turbulence intensity measurement model for sediment-laden water flow, which includes a water flow control system and a measurement system.

[0103] The water flow control system includes a muddy water mixing tank 1, a central control room 3, a muddy water inlet pipe 4, a front pool 5, a water stabilization grid 6, a tail gate 7, a muddy water outlet pipe 8 and an open channel water tank 9.

[0104] The measuring system includes a sediment content measuring device 2 , a movable measuring bridge 10 , a temperature sensor 11 , a water level gauge 18 , and a water flow pulsation pressure sensor 21 .

[0105] For the layout relationship of each device in this model, please refer to Figure 2 and Figure 3 The muddy water stirring tank 1 is located on one side of the open channel water tank 9. The front area of ​​the open channel water tank 9 is connected to the muddy water stirring tank 1 through the muddy water inlet pipe 4, and the tail area of ​​the open channel water tank 9 is connected to the muddy water stirring tank 1 through the muddy water outlet pipe 8, so that a water flow loop is formed between the open channel water tank 9 and the muddy water stirring tank 1. After the measurement is completed, the experimental sand-containing water in the open channel water tank 9 can also be returned to the muddy water stirring tank 1, saving resources.

[0106] A sediment content meter 2 for measuring the sediment content in the water body is set in the muddy water mixing tank 1. In addition, sediment content meters 2 are also set in the front and rear tank bodies of the open channel flume 9. A mobile measuring bridge 10 is set above the open channel flume 9 and can move horizontally in the direction of the open channel flume 9. The mobile measuring bridge 10 is provided with a vertical threaded connecting rod 15 for lifting and lowering. A water flow pulsation pressure sensor 21 for measuring the turbulence intensity of the sediment-laden water flow is fixedly installed at the lower end of the vertical threaded connecting rod 15. In order to improve the transmission capacity of signal data, the water flow pulsation pressure sensor 21 is connected to a pressure transmitter 22, and the connection is made by wired connection, which effectively avoids the disadvantage of water body interference with wireless signal transmission. The pressure transmitter 22 is set above the water surface and is connected to the signal test and analysis unit 23 by wireless transmission. After receiving the data signal collected by the water flow pulsation pressure sensor 21, the signal test and analysis unit 23 performs analysis and processing.

[0107] In addition, to facilitate control of experimental conditions, several water level gauges 18 were installed at equal intervals on the inner wall of the open channel flume 9. A tailgate 7 for controlling runoff was installed at the tail end of the open channel flume 9. This tailgate 7 was connected to a central control room 3 located next to the open channel flume 9. The water level gauges 18 were wirelessly connected to a signal receiver 19, which in turn was wired to a data acquisition unit 20. The data acquisition unit 20 received the measurement data from the water level gauges 18 and transmitted it to the central control room 3. Based on the measurement data from the water level gauges 18 and the requirements of the experimental measurements, the central control room 3 adjusted the opening and closing angle of the tailgate 7 and the inflow rate of the muddy water inlet pipe 4.

[0108] In order to collect more comprehensive experimental data, a temperature sensor 11 for measuring water temperature is fixedly installed on the inner wall of the middle part of the open channel water tank 9. The temperature sensor 11 can establish a wired connection with the data acquisition unit 20 through the signal receiver 19 and transmit the collected water temperature data to the central control room 3.

[0109] In order to facilitate the control of the water state in the open channel water tank 9, a water stabilizing grille 6 is provided in the front area of ​​the open channel water tank 9. The water stabilizing grille 6 divides the front area of ​​the open channel water tank 9 into a front pool 5. The front pool 5 is connected to one end of the muddy water inlet pipe 4. The high-pressure water injected into the open channel water tank 9 by the muddy water inlet pipe 4 becomes stable and controllable after being processed by the front pool 5 and the water stabilizing grille 6.

[0110] It is worth mentioning that in order to flexibly adjust the position of the water flow pulsation pressure sensor 21 in the water body, this embodiment provides a mobile measuring bridge 10 that can conveniently adjust the position of the water flow pulsation pressure sensor 21. Figure 4 As shown, the movable measuring bridge 10 includes a horizontal threaded connecting rod 14, a vertical threaded connecting rod 15, a rotating handle 16 and a rotating screw 17. The horizontal threaded connecting rod 14 is threadedly connected to a movable platform 151. The vertical threaded connecting rod 15 is threadedly connected to one side of the movable platform 151, and a rotating screw 17 is inserted into the upper end of the vertical threaded connecting rod 15; bearing bases 132 are provided at both ends of the horizontal threaded connecting rod 14, and the bearing base 132 is installed on the bridge frame 131. One end of the horizontal threaded connecting rod 14 passes through the bearing base 132 and is fixedly connected to the rotating handle 16. Limit rods 141 are symmetrically provided on both sides of the horizontal threaded connecting rod 14. The limit rods 141 pass through the platform of the movable platform 151, and both ends thereof are fixed on the bridge frame 131.

[0111] The lower part of the movable measuring bridge 10 is provided with a roller 13 , which is rotatably mounted on the lower part of the bridge frame 131 and rollingly arranged on the water tank track 12 , which is mounted on the upper end surface of the open channel water tank 9 .

[0112] According to the measurement research requirements of the turbulence intensity of the sediment-laden water flow, sediment solids and impurity-free water are put into the muddy water mixing tank 1. After being mixed and stirred evenly, muddy water with high sand content and very fine sediment particles is formed. The muddy water in the muddy water mixing tank 1 is measured by the sediment content meter 2 to determine whether it meets the experimental research requirements. If not, the proportion of water or sandy solids is adjusted according to the measurement results. If it meets the experimental research requirements, the muddy water inlet pipe 4 is opened to inject into the open channel flume 9, and after being buffered by the forebay 5 and the water stabilizing grid 6, it enters the test section of the open channel flume 9. The horizontal position of the open channel flume 9 where the water flow pulsation pressure sensor 21 is located is adjusted by pushing the mobile measuring bridge 10 ( Figure 1 and Figure 2 When the position to be measured is reached, the horizontal threaded connecting rod 14 is rotated by rotating the handle 16, so that the movable platform 151 moves horizontally along the horizontal threaded connecting rod 14 ( Figure 2 Then, by rotating the screw 17, the vertical threaded connecting rod 15 is moved in the vertical direction ( Figure 3The water flow pulsation pressure sensor 21 is moved up and down in the z-axis direction to complete the position adjustment of the water flow pulsation pressure sensor 21. The experimental environmental factors are measured by the temperature sensor 11 and the water level meter 18, and the turbulence intensity of the sediment-laden water flow in the high sand content and very fine sediment water environment at various positions in the open channel water tank 9 is measured by the water flow pulsation pressure sensor 21.

[0113] This invention uses pulsating pressure instead of pulsating velocity as a quantitative indicator of the turbulence intensity of sediment-laden flows. While maintaining measurement accuracy, it not only improves computational efficiency but also overcomes the technical bottleneck of measuring high-sediment and extremely fine sediment. Furthermore, the automated nature of the model avoids the subjectivity of manual measurement during experiments, providing technical support for conducting physical model experiments on the turbulence characteristics of sediment-laden flows, especially those with high sediment concentrations.

[0114] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for measuring the turbulence intensity of sediment-laden water flow in a sediment environment, characterized in that: The following steps are involved: Step S1: Determination of model input conditions, including the range of sediment content and median sediment particle size; Step S2: Model debugging and operation, regulating the water flow control system, and measuring the water depth and flow velocity data of the model section; Step S3: determining the model experimental conditions based on the uniform flow-turbulent flow-slow flow pattern; Step S4: collecting test data and measuring the water flow pulsating pressure at each measuring point; Step S5 processes the collected test data and outputs a quantitative index of the turbulence intensity of the sediment-laden water flow, describing the change of the turbulence intensity of the sediment-laden water flow in each direction of the open channel flume (9), including the following steps: In step S51, the water flow pulsation pressure value at each measuring point is calculated according to the actual measurement results of the water flow pulsation pressure sensor (21). The water flow pulsation pressure is defined as the instantaneous pressure P of the water flow. i The mean pressure at the same time The difference between the two values ​​is calculated by calculating the root mean square of the water flow pulsation pressure value over a period of time as a quantitative index of the turbulence intensity of the sediment-carrying water flow σ P : Where, P i For [T star , T end ] is the instantaneous pressure of the sediment-carrying water flow at the i-th moment in the time period, M is the number of measured instantaneous pressure data in the time period, T star and T end Indicates the start and end time of measurement sampling; In step S52, based on the calculation results of step S51, the turbulence intensity changes of the sediment-laden water flow along the vertical, horizontal and vertical directions of the open channel flume (9) are counted and outputted: On the vertical line of the open channel flume (9), the average value of the turbulence intensity of the sediment-carrying water flow of all measuring points with the same x-axis and y-axis coordinates is taken to describe the change of the turbulence intensity of the sediment-carrying water flow along the z-axis at the point; In the horizontal direction of the open channel flume (9), the average value of the turbulence intensity of the sediment-carrying water flow at all measuring points with the same x-axis and z-axis coordinates is taken to describe the change of the turbulence intensity of the sediment-carrying water flow at the point in the open channel flume (9) along the y-axis direction; In the longitudinal direction of the open channel flume (9), the mean value of the turbulence intensity of the sediment-carrying water flow of all measuring points with the same z-axis and y-axis coordinates is taken to describe the change of the turbulence intensity of the sediment-carrying water flow at the point in the open channel flume (9) along the x-axis direction.

2. The method for measuring turbulence intensity of sediment-laden water flow in a sediment environment according to claim 1, characterized in that: In step S1, the model input conditions are determined, including the sediment content S and the median sediment particle size D 50 The value range of is as follows: Step S11, sediment median particle size D 50 The value range of: 0<D 50 ≤0.5mm, the value range of sand content S: 0<S≤500kg / m 3 , the sediment content S and the median particle size D of the sediment in a single group of model tests 50 For constant conditions, the model input conditions in each group of experiments are determined by giving the sediment content and the step size of the median sediment particle size change, which can be expressed as follows: S+(i-1)×ΔS D 50 +(i-1)×ΔD 50 Among them, S represents the sediment content, i represents the i-th test group of the model, ΔS represents the change step of the sediment content, and D 50 Indicates the median particle size of sediment, ΔD 50 Indicates the change step size of the median particle size of sediment; In step S12, according to the median particle size of the sediment in the model input conditions, prototype sand is screened using a sieve to prepare experimental sand, and a particle size analyzer is used to analyze and draw a particle size gradation curve of the experimental sand. The median particle size of the sediment in the experimental sand required by the model input conditions is obtained through the particle size gradation curve. According to the sand content in the model input conditions, the above-mentioned test sand and clean water are added to the muddy water stirring tank (1) and stirred to prepare muddy water that meets the experimental requirements.

3. The method for measuring turbulence intensity of sediment-laden water flow in a sediment environment according to claim 1, characterized in that: In step S2, the debugging of the water flow control system of the model includes the following steps: In step S21, based on the model input conditions, the model flow rate and the tailgate (7) opening are adjusted through the water flow control system, and the entire model is tested; In step S22, after the sediment-laden water flow entering the model becomes stable, the measurement system is used to measure the cross-sectional water depth and flow velocity data of the open channel flume (9) during the trial operation of the model.

4. The method for measuring turbulence intensity of sediment-laden water flow in a sediment environment according to claim 1, characterized in that: In step S3, the model experimental conditions are determined based on the uniform flow-turbulent flow-slow flow mode. The determination of the uniform flow-turbulent flow-slow flow mode includes the following steps: In step S31, based on the water depth and velocity data of the model section in step S2, the following formulas are used to calculate the Froude number Fr, Reynolds number Re, and along-the-line gradient J of the sediment-laden flow during the model trial run: Re=vR / η Where v is the flow velocity of the open channel flume section, R is the hydraulic radius of the river, which is the ratio of the cross-sectional area of ​​the open channel flume to the wetted perimeter of the flume; g is the acceleration of gravity, h is the water depth of the open channel flume section, η is the viscosity coefficient of the clear water flow, and h is the water viscosity coefficient of the clear water flow. i represents the water level reading of the i-th water level gauge, n g Indicates the total number of water level gauges, Δl g Indicates the distance between adjacent water level gauges; Step S32, based on the calculation results of the Froude number, the Reynolds number and the gradient along the way, determines whether the current water flow satisfies the uniform flow-turbulent flow-slow flow mode. When the gradient along the way remains unchanged and is equal to the slope of the open channel flume (9), the sediment-laden water flow is determined to be uniform flow; when the Reynolds number is greater than 10,000, the sediment-laden water flow is determined to be turbulent flow; when the Froude number is less than 1, the sediment-laden water flow is determined to be slow flow. In step S33, if the uniform flow-turbulent flow-slow flow mode condition is met in step S32, step S4 is performed; if not, step S2 is returned to, and the model flow rate and the tailgate (7) opening are adjusted again through the water flow control system.

5. The method for measuring turbulence intensity of sediment-laden water flow in a sediment environment according to claim 1, characterized in that: In step S4, the collection of test data includes the following steps: In step S41, after the sediment-laden water flow in the model stabilizes and meets the uniform flow-turbulent flow-slow flow mode conditions, the instantaneous value of the water flow pulsating pressure at the initial measuring point is recorded in real time by the measurement system and a curve of the instantaneous value change is drawn. The sampling time for a single measuring point is 60 seconds, and the recording is repeated three times within the sampling time; In step S42, the sediment content measuring device (2) is used to record the change of the sediment content of the sediment-laden water flow in real time. If the sediment content remains substantially unchanged during the measurement process, step S43 is performed. If the sediment content decreases significantly during the measurement process, corresponding adjustments are made by adding sediment to the muddy water stirring tank (1). In step S43, after the collection of the water flow pulsation pressure data at the measuring point is completed, the process moves to the next measuring point and returns to step S41. If the data of all measuring points have been collected, the process proceeds to step S51.

6. The method for measuring turbulence intensity of sediment-laden water flow in a sediment environment according to claim 5, characterized in that: In step S43, the movement of the measuring point follows the order of the z-axis, y-axis and x-axis of the open channel flume (9), and the operation steps are as follows: Step a, keeping the x-axis and y-axis coordinates unchanged, moving the water flow pulsation pressure sensor (21) along the z-axis direction at equal intervals Δz until it reaches its maximum value in the z-axis direction; Step b, keeping the x-axis coordinate unchanged, moving the water flow pulsation pressure sensor (21) along the y-axis at equal intervals Δy to the measuring point (x0, y0+Δy, z0), repeating step a, then moving the water flow pulsation pressure sensor (21) along the y-axis at equal intervals to the measuring point (x0, y0+2Δy, z0), repeating step a until the y-axis direction is maximum; Step c, keeping the y-axis and z-axis coordinates unchanged, moving the water flow pulsation pressure sensor (21) along the x-axis at equal intervals Δx to the measuring point (x0+Δx, y0, z0), repeating steps a and b in succession, then moving the water flow pulsation pressure sensor (21) along the x-axis at equal intervals to the measuring point (x0+2Δx, y0, z0), repeating steps a and b in succession until the x-axis direction is maximum.

7. A model for measuring the turbulence intensity of sediment-laden water flow in a sediment environment according to any one of claims 1 to 6, characterized in that: The model includes: The water flow control system comprises a muddy water mixing tank (1), a central control room (3), a muddy water inlet pipe (4), a front pool (5), a water stabilization grid (6), a tailgate (7), a muddy water outlet pipe (8) and an open channel flume (9); wherein, The muddy water stirring tank (1) is located on one side of the open channel water tank (9). A water stabilizing grille (6) is provided in the front area of ​​the open channel water tank (9). The area enclosed between the water stabilizing grille (6) and the front end side wall of the open channel water tank (9) is a fore tank (5). The fore tank (5) is connected to one end of the muddy water inlet pipe (4). The other end of the muddy water inlet pipe (4) is connected to the muddy water stirring tank (1). A tail gate (7) is provided at the tail of the open channel water tank (9). The tail gate (7) is connected to the central control room (3) to establish a control connection for the opening and closing angle. The two ends of the muddy water backflow pipe (8) are respectively connected to the tail of the open channel water tank (9) and the muddy water stirring tank (1). The measuring system includes a sediment content measuring device (2), a movable measuring bridge (10), a temperature sensor (11), a water level meter (18), and a water flow pulsation pressure sensor (21); wherein, The sediment content measuring device (2) is arranged in the muddy water mixing tank (1) and in the front and rear tank bodies of the open channel water tank (9); a movable measuring bridge (10) is arranged above the open channel water tank (9) and moves horizontally in the direction of the open channel water tank (9); a water flow pulsation pressure sensor (21) is fixedly installed at the lower end of the movable measuring bridge (10); a plurality of water level gauges (18) are arranged at equal intervals on the inner wall of the tank body of the open channel water tank (9); and a temperature sensor (11) is fixedly arranged on the inner wall tank body in the middle.

8. The model according to claim 7, characterized in that The water flow pulsation pressure sensor (21) is connected to the pressure transmitter (22) by wire, the pressure transmitter (22) is connected to the signal test and analysis unit (23) by wireless transmission, the temperature sensor (11) and the water level meter (18) are connected to the signal receiver (19) by wireless communication, and the signal receiver (19) is connected to the data acquisition unit (20) by wire.

9. The model according to claim 7, characterized in that The movable measuring bridge (10) comprises a horizontal threaded connecting rod (14), a vertical threaded connecting rod (15), a rotating handle (16) and a rotating screw (17); the horizontal threaded connecting rod (14) is connected to a movable platform (151) by a thread; the vertical threaded connecting rod (15) is threadedly connected to a side platform of the movable platform (151); the rotating screw (17) is inserted into the upper end of the vertical threaded connecting rod (15), and the water flow pulsation pressure sensor (21) is fixedly installed at the lower end; bearing bases (132) are provided at both ends of the horizontal threaded connecting rod (14), and the bearing bases (132) are installed on the bridge frame (131). 1), one end of a horizontal threaded connecting rod (14) passes through the bearing base (132) and is fixedly connected to the rotating handle (16), and limiting rods (141) are symmetrically arranged on both sides of the horizontal threaded connecting rod (14), and the limiting rods (141) pass through the platform body of the movable platform (151), and the two ends thereof are fixed on the bridge (131), and a roller (13) is arranged at the lower part of the movable measuring bridge (10), and the roller (13) is rotatably mounted on the lower part of the bridge (131) and rollingly arranged on the water tank track (12), and the water tank track (12) is mounted on the upper end surface of the open channel water tank (9).

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