Method and model for measuring turbulence intensity of sediment-carrying water flow in sediment environment

Abstract

The invention discloses a method and a model for measuring turbulence intensity of sediment-carrying water flow in a sediment environment. The model comprises a water flow control system and a measurement system, and the method comprises the following steps: determining model input conditions including the value ranges of the sand content and the sediment median particle size; debugging and operating the model, regulating and controlling a water flow control system, and measuring section water depth and flow velocity data of the model; judging model experiment conditions according to a uniform flow-turbulent flow-slow flow mode; collecting test data, and measuring the water flow pulsation pressure intensity at each measuring point; and processing the collected test data, and outputting a quantitative index of the turbulence intensity of the sediment carrying water flow. According to the method, the pulsating pressure intensity is used for replacing the pulsating flow velocity to serve as a quantitative index of the turbulent fluctuation intensity of the sediment-carrying water flow, the measurement precision is guaranteed, meanwhile, the calculation efficiency is improved, the technical bottleneck of high-sediment-content and ultra-fine-particle sediment is broken through, and the method has great significance for developing the sediment-carrying water flow. And particularly, a certain technical support is provided for physical model test research on the turbulent fluctuation characteristic of the high-sediment-content water flow.

Description

Technical Field

[0001] The 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 sand-laden water flow in a silt environment. Background Art

[0002] In addition to theoretical derivation, direct observation of water flow turbulence structure and measurement of its characteristic parameters in laboratory environment by designing or modifying relevant instruments and equipment has long been the focus of turbulence research. As one of the important parameters of water flow turbulence characteristics, water flow turbulence intensity is usually quantified by the root mean square of pulsating flow velocity. The application of traditional water flow turbulence characteristic measurement methods and equipment in high sand content and ultra-fine sediment environments still faces the following problems and challenges. For particle image velocimetry, although the local flow field changes caused by contact measurement are avoided, on the one hand, high sand content greatly increases the density of tracer particles in the fluid, and the image can only be divided into small areas called windows, and the average velocity in the window is used as the local flow velocity at the center of the area. Then, based on a series of related algorithms, the window position where the cross-correlation function of a window in the first frame image reaches a peak is found in the second frame image, and the displacement and direction of the peak position relative to the center 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 calculation efficiency and accuracy of the processing; on the other hand, the acoustic Doppler velocimeter is easily damaged in a high sand content environment, and at the same time, it will 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 turbulence intensity of sediment-laden water flow in high sand content and extremely fine sediment environment, a method and model for measuring turbulence intensity of sediment-laden water flow in sediment environment was 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 under a silt environment are proposed. The pulsating pressure of the sand-laden water flow is used as a quantitative indicator of turbulence intensity. While ensuring the measurement efficiency and accuracy, the measurement automation is realized to avoid the interference of human operation on the measurement results. The technical bottleneck of the sand content and the sediment particle size range in the process of measuring the turbulence intensity of the sand-laden water flow is broken through. The method can provide technical support for the basic research on sediment movement mechanics in terms of physical model experiments.

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

[0006] A method for measuring 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, adjusting 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 according to the uniform flow-turbulent flow-slow flow mode;

[0010] Step S4: collecting test data and measuring the water flow pulsation 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, median particle size of sediment 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 tests are determined by respectively giving the sediment content and the step length of the median particle size of the sediment, which can be expressed by the following formula:

[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 length of the median particle size of sediment;

[0017] In step S12, according to the median particle size of sediment in the model input conditions, prototype sand is screened with a sieve to pre-prepare 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 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 into a turbid water stirring tank, and turbid water that meets the experimental requirements is prepared by stirring.

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

[0019] 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, according to 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 the gradient J along the flow path of the sediment-carrying flow during the model trial operation:

[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 gravitational acceleration, 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 gravitational acceleration. i represents the water level reading of the ith 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, the Reynolds number and the gradient along the way, it is determined 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, the sand-carrying water flow is determined to be a uniform flow; when the Reynolds number is greater than 10000, the sand-carrying water flow is determined to be a turbulent flow; when the Froude number is less than 1, the sand-carrying water flow is determined to be a slow flow;

[0028] Step S33: If the uniform flow-turbulent flow-slow flow mode condition is met in step S32, then step S4 is performed; if not, then step S2 is returned to re-adjust the model flow and tailgate opening 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] Step S41: After the sand-carrying water flow in the model is stable and meets the uniform flow-turbulent flow-slow flow mode conditions, the instantaneous value of the water flow pulsation pressure at the initial measuring point is recorded in real time by the measurement system and the instantaneous value change curve is drawn. The sampling time of a single measuring point is 60 seconds, and the recording is repeated 3 times within the sampling time;

[0031] Step S42, using a sediment content measuring device to record the change of the sediment content of the sediment-carrying water flow in real time, if the sediment content remains basically unchanged during the measurement process, then proceed to step S43, if the sediment content decreases significantly during the measurement process, then make corresponding adjustments by adding sand to the muddy water stirring tank;

[0032] In step S43, after the water flow pulsation pressure data is collected at the measuring point, it moves to the next measuring point and returns to step S41; if the data of all measuring points have been collected, step S51 is performed.

[0033] As a further solution of the present invention, in step S43, the movement of the measuring point follows the sequence 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 direction at equal intervals Δz until it is the maximum in the z-axis direction;

[0035] Step b, keep the x-axis coordinate unchanged, move the water flow pulsation pressure sensor along the y-axis at an equal interval 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 an equal interval to the measuring point (x0, y0+2Δy, z0), 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 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 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.

[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-carrying water flow, which describes the change of the turbulence intensity of the sediment-carrying water flow in each direction 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 The difference between the two 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 change of turbulence intensity of the sand-carrying water flow along the vertical, horizontal and vertical lines of the open channel flume is counted and outputted:

[0042] On the vertical line 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 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 direction at that point;

[0043] In the horizontal direction of the open channel flume, 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 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 a sediment-laden water flow in a sediment environment, the model comprising:

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

[0047] The muddy water mixing tank is located on one side of the open channel water tank. A water stabilizing grille is provided in the front area of ​​the open channel water tank. The area enclosed between the water stabilizing grille and the front side wall of the open channel water tank is the fore pool. The fore pool 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 tail of the open channel water tank. The tail gate is connected to the central control room to control the opening and closing angles. The two ends of the muddy water backflow pipe are respectively connected to the tail of the open channel water tank and the muddy water mixing tank.

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

[0049] The sediment content measuring device is installed in the turbid water mixing tank and in the front and rear parts of the open channel flume. The movable measuring bridge is installed above the open channel flume and moves horizontally along the direction of the open channel flume. The lower end of the movable measuring bridge is fixedly installed with a water flow pulsation pressure sensor. Several water level gauges are evenly spaced on the inner wall of the flume of the open channel flume, and a temperature sensor is fixedly installed 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 the water level meter are connected to the signal receiver by wireless communication, and the signal receiver is connected to the data acquisition unit by wire.

[0051] As a further scheme of the present invention, the mobile 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 moving platform, the vertical threaded connecting rod is threadedly connected to a side body of the moving platform, the rotating screw is inserted into the upper end of the vertical threaded connecting rod, and the water flow pulsation pressure sensor is fixedly installed at the lower end; bearing bases are arranged at both ends of the horizontal threaded connecting rod, 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 arranged on both sides of the horizontal threaded connecting rod, the limit rods pass through the body of the moving platform, and the two ends thereof are fixed on the bridge frame, and a roller is arranged at the lower part of the mobile measuring bridge, the roller is rotatably installed at the lower part of the bridge frame, and is rollingly arranged on a water tank track, and the water tank track is installed on the upper end surface of the open channel water tank.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows: 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 sand-laden water flow, breaking through the limitations of low sand content and coarse sand particles in the process of water flow turbulence measurement under traditional laboratory conditions. The present invention adopts an automated measurement method of monitoring parameter data by a measurement system, which ensures the 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 sand-laden water flow, especially the turbulence characteristics of high sand content water flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a flow chart of the method for measuring the turbulence intensity of the sand-carrying water flow in a silt environment proposed by the present invention;

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

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

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

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

[0058] The numbers in the figure are: 1. turbid water mixing tank; 2. sand content measuring device; 3. central control room; 4. turbid water inlet pipe; 5. front pool; 6. water stabilizing grid; 7. tail gate; 8. turbid water outlet pipe; 9. open channel flume; 10. mobile measuring bridge; 11. temperature sensor; 12. flume track; 13. roller; 131. bridge frame; 132. bearing base; 14. horizontal threaded connecting rod; 141. limit rod; 15. vertical threaded connecting rod; 151. moving platform; 16. turning handle; 17. rotating screw; 18. water level meter; 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 described clearly and completely 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. The velocity and pressure pulsations near the bed surface and the exchange of upper and lower water masses caused by water turbulence are generally considered to be one of the factors affecting the initiation and diffusion of suspended sediment. In turn, the presence of sediment can change the turbulent structure of the water flow. However, there is still controversy over the turbulence-increasing-restricting effect of sediment content and sediment particle size in sediment-laden water flows, and the law of change of water turbulence intensity with sediment content and sediment particle size still needs further exploration. Therefore, the study of turbulent characteristics of sediment-laden water flows has always been the research focus in sediment movement mechanics and the basis for solving basic problems in sediment movement mechanics. At the same time, it has important theoretical guiding significance for river channel management of sandy rivers and ecological environmental protection.

[0061] With the development of computer and high-speed photography technology, the main means for quantitative research on water turbulence characteristic parameters can be divided into two categories: contact and non-contact measurement. There are two categories: particle image velocimetry (PIV or PTV) and acoustic Doppler velocimetry (ADV). The former refers to a series of particle image velocimetry technologies represented by PIV or PTV. By spreading markers in the fluid, image processing and analysis techniques are used to obtain the displacement of the markers within a certain time interval, that is, the instantaneous velocity of each point in the flow field; while the latter laser velocimeter is often used in conjunction with the data processing system of an electronic computer. When the sand content is not high, the time-averaged flow velocity, the mean square value of the pulsating flow velocity, and the pulsating flow velocity itself can be obtained at the same time; however, the above technical solutions greatly reduce the accuracy and efficiency of measuring the turbulence intensity of sand-laden water flow in an environment with high sand content and extremely fine sediment.

[0062] For the measurement of turbulence intensity of sand-carrying water flow in a high sand content and very fine sand environment, a simpler operation method is proposed in this embodiment. This method measures the turbulence intensity of sand-carrying water flow in a sand environment, uses the pulsating pressure of the sand-carrying water flow as a turbulence intensity quantitative index, and describes the change of the turbulence intensity of the sand-carrying water flow. Specifically, the method for measuring the turbulence intensity of sand-carrying water flow in a sand environment is described in detail. Figure 1 , the method mainly comprises 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, adjusting 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 according to the uniform flow-turbulent flow-slow flow mode;

[0066] Step S4: collecting test data and measuring the water flow pulsation 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 particle size D of the sediment. 50 The value range of is as follows:

[0069] Step S11, median particle size of sediment 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 natural river sediment, which is mainly suspended sediment, is between 0.062 mm and 0.5 mm; on the other hand, high-sediment-content water flows must have a sediment content greater than 200 kg / m3, while the maximum sediment content recorded in the main and tributary rivers of the Yellow River 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 tests are determined by giving the change step of the sediment content and sediment median particle size, 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 particle size of the sediment in the model input conditions, prototype sand is screened with a sieve to prefabricate the experimental sand, and a particle size analyzer is used to analyze and draw a particle size gradation curve of the experimental sand, which describes the trend of the proportion of the number of sediment particles larger than a certain particle size to the total number of sediment particles with the particle size. The median particle size of the sediment required by the experimental sand for the model input conditions is obtained through the particle size gradation curve to ensure that the median particle size of the sediment meets the requirements of the model input conditions. 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 the muddy water that meets the sand content input conditions of the group corresponding to the experimental requirements is stirred and prepared.

[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, water temperature t and other data of the open channel flume 9 during the trial operation of the model.

[0078] In step S3, the model experimental conditions are determined according to the uniform flow-turbulent flow-slow flow mode, and 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 the gradient J along the flow path of the sediment-carrying flow during the model trial operation:

[0080]

[0081] Re=vR / η

[0082]

[0083] Where v is the flow velocity of the open channel flume section (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, i.e. hB / (2h+B); g is the gravitational acceleration, h is the water depth of the open channel flume section, η is the viscosity coefficient of the clear water flow, h i represents the water level reading of the ith water level gauge, n g Indicates the total number of water level gauges, Δl g Indicates the distance between adjacent water level gauges.

[0084] Step S32 determines whether the current water flow satisfies the uniform flow-turbulent flow-slow flow mode based on the calculation results of the Froude number Fr, the Reynolds number Re and the along-the-way gradient J. When the along-the-way 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 step S32 meets the uniform flow-turbulent flow-slow flow mode conditions, proceed to step S4 (step S41); if not, return to step S2 (step S21), and re-adjust the model flow Q and the tailgate 7 opening a0 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] Step S41: After the sand-carrying 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 pulsating 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 measuring system and a curve of the instantaneous value change is drawn (e.g. Figure 5The curve of the instantaneous pressure of the sediment-carrying water flow at a certain moment at the measuring point is shown in Figure 1. The sampling time of a single measuring point is 60 seconds, and the data is recorded three times within the sampling time.

[0088] In step S42, the change of the sediment content of the sand-laden water flow is recorded in real time using the sediment content measuring device 2. 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 sand to the muddy water stirring tank 1.

[0089] In step S43, after the water flow pulsation pressure data is collected at the measuring point, it moves to the next measuring point and returns to step S41; if the data of all measuring points have been collected, step S51 is performed.

[0090] The movement of the measuring point follows the sequence 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 direction at equal intervals Δz until it is at its maximum in the z-axis direction;

[0092] Step b, keep the x-axis coordinate unchanged, move the water flow pulsation pressure sensor 21 along the y-axis at an equal interval of 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 an equal interval to the measuring point (x0, y0+2Δy, z0), 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-carrying water flow, which describes the change of the turbulence intensity of the sediment-carrying 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 result 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 The difference between the two 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 sand-carrying water flow measured in step S41, a length of [Tstar , T end ] The data contained in the time period (such as Figure 5 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 time of the measurement sampling. Since each measuring point in step S41 repeatedly records the measurement results of the instantaneous pressure of the sand-carrying water flow three times, the turbulence intensity result of the sand-carrying water flow at each measuring point is the average of these three measurement results. In this way, the turbulence intensity of the sand-carrying water flow at all measuring points is calculated one by one.

[0098] In step S52, based on the calculation result of step S51, the change of turbulence intensity of the sand-carrying water flow along the vertical, horizontal and vertical lines of the open channel flume 9 is 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 direction 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 this 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 a sand-carrying water flow in a silt environment, this embodiment further proposes a model for measuring the turbulence intensity of a sand-carrying 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 tank 5, a water stabilizing grid 6, a tail gate 7, a muddy water outlet pipe 8 and an open channel 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 meter 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] The sediment content measuring device 2 for measuring the sediment content in the water body is arranged in the muddy water mixing tank 1. In addition, the sediment content measuring device 2 is also arranged in the tank body of the front and tail of the open channel water tank 9. The mobile measuring bridge 10 is arranged above the open channel water tank 9 and can move horizontally along the direction where the open channel water tank 9 is located. The mobile measuring bridge 10 is provided with a vertical threaded connecting rod 15 whose shell can be lifted up and down. A water flow pulsation pressure sensor 21 for measuring the turbulence intensity of the sand-carrying 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 the pressure transmitter 22, and the connection is made by wired connection, which effectively avoids the disadvantage of water body interfering with wireless signal transmission. The pressure transmitter 22 is arranged above the water surface, and the pressure transmitter 22 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, in order to facilitate the control of experimental conditions, a number of water level gauges 18 are arranged at equal intervals on the inner wall of the open channel water tank 9, and a tail gate 7 for controlling the runoff is arranged at the tail of the open channel water tank 9, and the tail gate 7 is connected to the central control room 3 arranged beside the open channel water tank 9. The water level gauge 18 is connected to the signal receiver 19 through wireless communication, and the signal receiver 19 is connected to the data acquisition unit 20 by wire. The data acquisition unit 20 receives the measurement data of the water level gauge 18 and transmits it to the central control room 3. The central control room 3 adjusts the opening and closing angle of the tail gate 7 and the water inlet flow of the muddy water inlet pipe 4 according to the measurement data of the water level gauge 18 and the requirements of the experimental measurement.

[0108] In order to collect more comprehensive experimental data, a temperature sensor 11 for measuring the 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 a 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 grid 6 is arranged in the front area of ​​the open channel water tank 9. The water stabilizing grid 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 grid 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, the present embodiment is provided with a mobile measuring bridge 10 which 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 a side body 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. 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 body of the movable platform 151, and both ends thereof are fixed on the bridge frame 131.

[0111] A roller 13 is provided at the lower part of the movable measuring bridge 10 . The roller 13 is rotatably mounted at the lower part of the bridge frame 131 and is rollingly arranged on a water tank track 12 . The water tank track 12 is installed 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 sand-laden water flow, silt solids and impurity-free water are placed in the turbid water stirring tank 1, and after being mixed and stirred evenly, turbid water with high sand content and very fine silt particles is formed. The turbid water in the turbid water stirring tank 1 is measured by the sand content measuring device 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 turbid water inlet pipe 4 is opened to inject into the open channel flume 9, and after buffering treatment by the fore pool 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 rotating handle 16, so that the moving platform 151 moves horizontally along the horizontal threaded connecting rod 14 ( Figure 2 Then, by rotating the rotating 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. The turbulence intensity of the sand-carrying water flow in the high sand content and ultra-fine sediment water environment at various positions in the open channel flume 9 is measured by the water flow pulsation pressure sensor 21.

[0113] The present invention uses pulsating pressure instead of pulsating flow velocity as a quantitative indicator of the turbulence intensity of sediment-carrying water flow. While ensuring the measurement accuracy, it not only improves the calculation efficiency, but also breaks through the technical bottleneck of high sand content and extremely fine sediment particles. At the same time, the automation characteristics in the model also avoid the influence of the subjectivity of the human measurement process in the experiment, and provides certain technical support for the physical model test research on the turbulence characteristics of sediment-carrying water flow, especially high sand content water flow.

[0114] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for measuring the turbulence intensity of a 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, adjusting 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 according to the uniform flow-turbulent flow-slow flow mode; Step S4: collecting test data and measuring the water flow pulsation pressure at each measuring point; In step S5, the collected test data are processed to output a quantitative index of the turbulence intensity of the sediment-laden water flow.

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 particle size D of the sediment. 50 The value range of is as follows: Step S11, median particle size of sediment 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 tests are determined by respectively giving the sediment content and the step length of the median particle size of the sediment, which can be expressed by the following formula: 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 length 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 of 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 (1) to stir and prepare turbid 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: Step S21, based on the model input conditions, the model flow rate and the opening of the tailgate (7) 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 according to the uniform flow-turbulent flow-slow flow mode, and 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 the gradient J along the flow path of the sediment-carrying flow during the model trial operation: 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 gravitational acceleration, 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 gravitational acceleration. i represents the water level reading of the ith 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, determining 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 sand-carrying water flow is determined to be a uniform flow; when the Reynolds number is greater than 10000, the sand-carrying water flow is determined to be a turbulent flow; when the Froude number is less than 1, the sand-carrying water flow is determined to be a slow flow; Step S33: If the uniform flow-turbulent flow-slow flow mode condition is met in step S32, then step S4 is performed; if not, then step S2 is returned to re-adjust the model flow and the tailgate (7) opening 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: Step S41: After the sand-carrying water flow in the model is stable and meets the uniform flow-turbulent flow-slow flow mode conditions, the instantaneous value of the water flow pulsation pressure at the initial measuring point is recorded in real time by the measurement system and the instantaneous value change curve is drawn. The sampling time of a single measuring point is 60 seconds, and the recording is repeated 3 times within the sampling time; Step S42, using the sediment content measuring device (2) to record the change of the sediment content of the sediment-carrying water flow in real time, if the sediment content remains basically unchanged during the measurement process, then proceed to step S43, if the sediment content significantly decreases during the measurement process, then make corresponding adjustments by adding sediment to the muddy water stirring tank (1); In step S43, after the water flow pulsation pressure data is collected at the measuring point, it moves to the next measuring point and returns to step S41; if the data of all measuring points have been collected, step S51 is performed.

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 sequence 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 the pressure in the z-axis direction is the maximum; Step b, keeping the x-axis coordinate unchanged, moving the water flow pulsation pressure sensor (21) along the y-axis at an equal interval 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 an equal interval 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 an equal interval of Δx to the measuring point (x0+Δx, y0, z0), repeating steps a and b in sequence, then moving the water flow pulsation pressure sensor (21) along the x-axis at an equal interval of Δx to the measuring point (x0+2Δx, y0, z0), repeating steps a and b in sequence until the x-axis direction is maximum.

7. The method for measuring turbulence intensity of sediment-laden water flow in a sediment environment according to claim 1, characterized in that: In step S5, the collected test data are processed to output a quantitative index of the turbulence intensity of the sediment-carrying water flow, describing the change of the turbulence intensity of the sediment-carrying 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 result 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 The difference between the two 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 the measurement sampling; In step S52, based on the calculation result of step S51, the change of the turbulence intensity of the sand-carrying water flow along the vertical, horizontal and vertical directions of the open channel flume (9) is 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 at the point along the z-axis direction; In the horizontal 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 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 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 the point in the open channel flume (9) along the x-axis direction.

8. A model for measuring the turbulence intensity of sediment-carrying water flow in a sediment environment according to any one of claims 1 to 7, characterized in that: The model includes: A water flow control system comprises a muddy water mixing tank (1), a central control room (3), a muddy water inlet pipe (4), a front tank (5), a water stabilization grid (6), a tailgate (7), a muddy water outlet pipe (8) and an open channel tank (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 a 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 rear 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 an opening and closing angle. The two ends of the muddy water backflow pipe (8) are respectively connected to the rear of the open channel water tank (9) and the muddy water stirring tank (1). The measuring system comprises 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 stirring tank (1) and in the tank body at the front and rear of the open channel tank (9); the movable measuring bridge (10) is arranged above the open channel tank (9) and moves horizontally in the direction of the open channel 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 tank (9); and a temperature sensor (11) is fixedly arranged on the inner wall tank body in the middle.

9. The model according to claim 8, 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.

10. The model according to claim 8, characterized in that The mobile 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 threadedly connected to a moving platform (151); a side platform of the moving platform (151) is threadedly connected to the vertical threaded connecting rod (15); 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 arranged at both ends of the horizontal threaded connecting rod (14); 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 limit rods (141) are symmetrically arranged on both sides of the horizontal threaded connecting rod (14), and the limit rods (141) pass through the body of the movable platform (151), and the two ends thereof are fixed on the bridge frame (131), and a roller (13) is arranged at the lower part of the movable measuring bridge (10), and the roller (13) is rotatably mounted at the lower part of the bridge frame (131), and is rollingly arranged on a 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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