An indoor flume sediment start-up velocity measurement system and method

Abstract

The application discloses an indoor water tank sediment starting speed measurement system and method, and aims at solving the technical problem of sensor disturbance to a flow field and influence on data accuracy in the prior art measurement method.The technical scheme core is that the non-contact measurement characteristics of the PIV technology are applied to the whole process from flow field construction to data acquisition.The device is mainly composed of an imaging unit, a laser illumination unit, a movable sliding frame, a water flow adjusting unit and a buffer plate.Optical measurement is performed through the imaging unit and the laser illumination unit, and physical sensors do not need to be arranged in the flow field, so that the interference of the measuring instrument on the water flow structure and the sediment starting process is fundamentally avoided.The integrated movable sliding frame integrates the sediment laying, particle throwing and measurement functions, and is convenient for quickly positioning a test area;in combination with the buffer plate and the water inlet and drainage adjusting unit, a gradually changing flow field from weak to strong can be accurately and stably simulated.

Description

Technical Field

[0001] This invention relates to the field of sediment flow velocity measurement technology, specifically to an indoor water tank sediment initiation velocity measurement system and method. Background Technology

[0002] In hydraulic engineering research, the study of sediment initiation characteristics is crucial, and the accurate determination of critical flow velocities is of great significance for river regulation, reservoir siltation prediction, and flood control and disaster reduction. Currently, indoor flume experiments are one of the main methods for studying sediment initiation, and the accuracy and applicability of flow velocity measurements have a key impact on the reliability of the experimental results.

[0003] Traditionally, contact-type flow velocity measuring instruments (such as acoustic Doppler current meters, ADV) are commonly used in indoor flume experiments for flow velocity measurement. These instruments require the measuring probe to be placed directly in the water flow. When measuring the velocity of sediment initiation, the presence of the probe interferes with the original flow field structure. When the probe is placed in the flume, it obstructs the normal flow of water, alters the streamline distribution, and thus affects the force exerted on the sediment by the water flow. For sediment initiation, a condition extremely sensitive to water flow conditions, even minor changes in the flow field can distort the sediment initiation state, making the measured initiation velocity inaccurate to reflect the natural state. Furthermore, after prolonged use, the probe of contact-type instruments is susceptible to erosion and wear from sediment particles in the water flow, leading to decreased measurement accuracy and requiring frequent calibration and maintenance. Summary of the Invention

[0004] The purpose of this invention is to provide an indoor water tank sediment initiation speed measurement system and method to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for measuring the starting speed of sediment in an indoor water tank, characterized in that it includes:

[0006] Step 1: Sediment pretreatment: Select the sediment to be tested, obtain the sediment within the target particle size range through sieving, clean it, and then optimize it according to the characteristics of the sediment. Dry it for later use.

[0007] Step 2, Experimental Preparation: Spread the treated silt evenly at the bottom of the water tank and level the surface; inject clean water into the water tank, control the initial flow rate to slowly submerge the silt, and soak for the preset time; install and debug the imaging unit and laser illumination unit to ensure that the light plane covers the silt initiation observation area; release tracer particles and complete image calibration through the data processing unit;

[0008] Step 3, Flow velocity measurement: Adjust the flow rate to the preset value. After the water flow stabilizes, adjust the water level elevation through the water level control device. Observe the sediment initiation status on the bed surface. When a small amount of sediment is initiated, sediment is initiated in a local area, or sediment is initiated in most areas, the imaging unit and laser illumination unit are activated simultaneously to continuously acquire flow field images and record the water level data of the corresponding status.

[0009] Step 4: Data Processing: Import the acquired images into the data processing unit. After preprocessing such as noise reduction and distortion correction, calculate the displacement of the tracer particles using a cross-correlation algorithm. Combine this with the time interval to obtain the flow field velocity distribution. Analyze the velocity characteristics under different starting conditions to determine the critical starting velocity.

[0010] Preferably, in step two, the soaking time for the mud and sand is three hours.

[0011] An indoor water tank sediment initiation velocity measurement system, used to implement the indoor water tank sediment initiation velocity measurement method as described in the claims, characterized in that it includes:

[0012] The main body of the water tank, used to simulate a water flow environment, is made of transparent material. The bottom of the tank can be lined with test sand of different particle sizes. At both ends, there is an adjustable flow rate water pump and a drainage adjustment unit to control the water level in the tank. The water flow parameters can be adjusted according to the test requirements to ensure a stable flow field. One side of the tank is connected to the output end of the water pump through a water inlet, and the input end of the water pump is connected to a water storage tank. The water storage tank is connected to the other side of the tank through a water pipe, so that the tank, water pump, and water storage tank form a circulation.

[0013] The imaging unit includes a high-speed camera, which is mounted above the main body of the water tank and can clearly capture the motion trajectory of tracer particles in the flow field.

[0014] The laser illumination unit includes a high-energy pulsed laser, which can emit a uniform sheet light beam to illuminate the target flow field plane inside the water tank. The sheet light plane is perpendicular to the shooting direction of the high-speed camera to ensure clear imaging of the tracer particles.

[0015] The tracer particle delivery device includes a tracer particle chamber for uniformly delivering tracer particles into the water flow. The particle density is close to that of the test water body, which can accurately reflect the water flow motion state at different flow velocities.

[0016] The sediment delivery device includes a sediment bin for uniformly delivering experimental sediment into the main body of the water tank;

[0017] An adjustable bracket is provided with a first track wheel, which is connected to a first slide rail at the upper end of the water tank body. An imaging unit, a laser illumination unit, a tracer particle chamber, and a sediment chamber are placed on the adjustable bracket. The adjustable bracket can adjust the spatial position of the imaging unit and the laser illumination unit relative to the water tank body to adapt to different measurement ranges. The adjustable bracket can also adjust the placement position of the tracer particle chamber and the sediment chamber for releasing tracer particles and sediment.

[0018] The data processing unit is a digital computer connected to a high-speed camera. It has built-in PIV-specific analysis software, which can perform functions such as image calibration, particle displacement calculation, flow velocity vector generation, and flow field visualization, and is adapted to the flow field data processing needs of sediments of different particle sizes.

[0019] Preferably, it also includes a sediment pretreatment unit for cleaning, screening and other treatments of the test sand.

[0020] Preferably, the adjustable bracket includes a sliding frame slidably mounted on the main body of the water tank, and a mounting frame fixed on the sliding frame and having an equipment mounting part, a first mounting part, and a second mounting part thereon; a sediment bin for discharging sediment is fixed on the first mounting part, a tracer particle bin for discharging tracer particles is fixed on the second mounting part, a laser illumination unit for irradiating tracer particles is fixed on the equipment mounting part, and an imaging unit for capturing the motion trajectory of tracer particles is ball-connected on the equipment mounting part;

[0021] The high-speed camera in the imaging unit is ball-jointed with the equipment mounting part of the sliding frame, and the lens of the high-speed camera is opposite to the main body of the water tank;

[0022] The high-energy pulsed laser in the laser lighting unit is fixedly mounted on the extension frame. One end of the extension frame is fixedly connected to the side of the equipment mounting part. The high-energy pulsed laser is located on the side of the water tank body, and its laser emission port is opposite to the side of the water tank body.

[0023] Preferably, the main body of the water tank is also equipped with a buffer unit:

[0024] The buffer unit includes: a flow-damping plate slidably mounted on a first slide rail, the flow-damping plate having an arc-shaped cross-section; two sliding plates fixedly mounted on the upper end of the flow-damping plate, which are slidably mounted on the first slide rail of the water tank body; the sliding plates having screw holes; the upper end of the water tank body having screw holes corresponding to the screw holes of the flow-damping plate; three baffles fixedly mounted at equal intervals along the extension direction of the flow-damping plate on its surface, the baffles having an arc-shaped cross-section, one side of which is fixedly connected to the surface of the flow-damping plate; the lower end of each baffle is on the same horizontal line as the upper end of the baffle below it; and three water outlets on the surface of the flow-damping plate, the installation positions of which correspond to the installation positions of the baffles, with the water outlets located on one side of the baffles, and the lowest water outlet located at the bottom of the flow-damping plate.

[0025] Preferably, the main body of the water tank is also provided with a drainage adjustment unit: including a through-hole plate fixed on the drainage side of the main body of the water tank, a number of through holes for drainage are opened on the through-hole plate, a number of rotating rods are rotatably installed inside the through-hole plate, and a number of baffles for opening and closing the corresponding through holes are fixed on the rotating rods. One end of each rotating rod is fixed to a driven gear, and adjacent driven gears are driven by a transmission gear to realize the synchronous rotation of the baffles, thereby adjusting the drainage volume.

[0026] Preferably, a sediment bin is fixedly installed on the first mounting part, and a strip-shaped notch is provided on the surface of the first mounting part. The sand outlet of the sediment bin is connected to the strip-shaped notch. The strip-shaped notch is used to release sediment in the sediment bin. A chute is provided on the first mounting part, and a first baffle is slidably installed in the chute. When the first baffle is in the initial position, it blocks the strip-shaped notch.

[0027] Preferably, a tracer particle chamber is fixedly installed on the second mounting part, and a strip-shaped through hole is provided on the second mounting part. The strip-shaped through hole is fixedly connected and communicates with the release port of the tracer particle chamber. A delivery rod is rotatably installed inside the strip-shaped through hole. The surface of the delivery rod is provided with several unevenly distributed grooves. One end of the delivery rod extends out of the second mounting part and is fixedly connected to the first pulley. One end of the transmission belt is sleeved on the first pulley, and the other end of the transmission belt is sleeved on the second pulley. The second pulley is coaxially fixedly installed with the first track wheel.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] This device leverages the non-contact nature of PIV technology throughout the entire process, from flow field construction to data acquisition. Imaging via an imaging unit and laser illumination unit eliminates the need for any physical sensors within the flow field, completely avoiding any disturbance to the water flow structure and sediment initiation process by the measuring instruments. This ensures that the acquired flow field data, especially the transient velocity field near the critical initiation state, accurately reflects the motion patterns of sediment particles of different sizes under natural conditions, significantly improving the accuracy and reliability of the data.

[0030] This device constructs an integrated testing system with versatility and flexibility. The movable sliding frame integrates functions such as sediment laying, particle delivery, imaging unit, and laser illumination unit, facilitating rapid positioning and switching of the test area. The flow damper reduces the impact of the water flow on the sediment. Through the coordinated operation of the inlet and outlet regulating units, the outlet regulating unit can flexibly adjust the water flow rate, thereby quickly matching the inlet flow rate and effectively maintaining the stability of the flow field inside the tank. Attached Figure Description

[0031] Figure 1 This is a flowchart of an indoor water tank sediment start-up speed measurement method according to the present invention;

[0032] Figure 2 This is a schematic diagram of the main structure of an indoor water tank sediment starting speed measurement system according to the present invention;

[0033] Figure 3 This is a schematic diagram of the mud outlet position of an indoor water tank mud and sand starting speed measuring system according to the present invention.

[0034] Figure 4 This is a schematic diagram of the workflow of the data processing unit of the indoor water tank sediment starting velocity measurement system of the present invention. Figure 1 ;

[0035] Figure 5 This is a schematic diagram of the workflow of the data processing unit of the indoor water tank sediment starting velocity measurement system of the present invention. Figure 2 ;

[0036] Figure 6 This is a schematic diagram of the structure of the sliding frame, mounting frame, equipment mounting part, first mounting part, second mounting part, sediment bin, and tracer particle bin of the indoor water tank sediment starting speed measuring system of the present invention.

[0037] Figure 7 This is a schematic diagram of the strip-shaped notch structure of an indoor water tank sediment starting speed measuring system according to the present invention;

[0038] Figure 8 for Figure 2 Enlarged view of point A;

[0039] Figure 9 This is a schematic diagram of the through-hole plate and baffle of an indoor water tank sediment starting speed measuring system according to the present invention.

[0040] In the diagram: 1. Water tank body; 101. Water inlet; 102. Water pump; 103. Water storage tank; 201. Flow buffer plate; 202. Slide plate; 203. First slide rail; 204. Water baffle; 205. Water storage section; 206. Water outlet; 301. Sliding frame; 302. First track wheel; 303. Mounting frame; 304. Equipment mounting section; 305. First mounting section; 306. Second mounting section; 307. High-speed camera; 308. High-energy pulse laser; 309. Extension frame. 310. Mounting plate; 401. Sediment bin; 402. Strip notch; 403. First baffle; 501. Tracer particle bin; 502. Strip through hole; 503. Dispensing rod; 504. First pulley; 505. Drive belt; 506. Second pulley; 507. Groove; 601. Through-hole plate; 602. Through hole; 603. Rotating rod; 604. Baffle; 605. Water outlet tank; 606. Driven gear; 607. Drive gear; 609. Rocker arm; 701. Mud outlet. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Please see Figure 2-9 To achieve non-contact measurement of sediment initiation, an indoor water tank sediment initiation velocity measurement system is proposed, including a water tank body 1. The water tank body 1 is a hollow cuboid made of transparent tempered glass, through which the flow of sediment inside the water tank body 1 can be observed. The water tank body 1 is 25m long, 1m wide, and 0.65m high, with a flat bottom surface for laying the sediment to be measured. A water inlet 101 is fixedly installed on one side of the water tank body 1. The water inlet 101 is fixedly connected to and communicates with the output end of a water pump 102. The water inlet 101 of the water pump 102 is connected to a water storage tank 103. The water pump 102 is an existing model water pump. The water pump 102 enables water in the water storage tank 103 to be injected into the water tank body 1 through the water inlet 101.

[0043] An electromagnetic flow meter is fixedly connected to the output end of the water pump 102. The electromagnetic flow meter is an existing technology component. By setting this technology component, the water output of the water pump 102 can be statistically analyzed. The water pump 102 adopts an existing variable frequency water pump with adjustable water output. The variable frequency water pump can control the amount and speed of water injected into the water tank body 1.

[0044] The upper sides of the main body 1 of the water tank are fixedly equipped with first slide rails 203 (shown in the figure). Figure 8 In the middle), an adjustable bracket is slidably mounted on the first slide rail 203. The adjustable bracket includes a slide frame 301, on which four first track wheels 302 (shown in the middle) are rotatably mounted. Figure 7 In the middle section, the concave surface of the first track wheel 302 is embedded in the first slide rail 203, and the first track wheel 302 can roll along the first slide rail 203. When the sliding frame 301 moves along the first slide rail 203, the first track wheel 302 rolls along the first slide rail 203. The sliding frame 301 is provided with screw holes, and the water tank body 1 is provided with corresponding screw holes. When the sliding frame 301 moves to the observation position of the high-speed camera 307 mentioned below, the position of the sliding frame 301 can be fixed by screwing bolts into the screw holes of the sliding frame 301 and the water tank body 1.

[0045] A mounting bracket 303 is fixedly installed above the sliding bracket 301. The upper surface of the sliding bracket 301 is fixedly connected to the lower end of the mounting bracket 303. The mounting bracket 303 includes an equipment mounting part 304. The equipment mounting part 304 is flat and parallel to the bottom surface of the water tank. On each side of the equipment mounting part 304, there is a mounting plate 310 perpendicular to the equipment mounting part 304. A first mounting part 305 is fixedly connected to one mounting plate 310, and a second mounting part 306 is fixedly connected to the other mounting plate 310. Both the first mounting part 305 and the second mounting part 306 are flat and parallel to the equipment mounting part 304. The height of the first mounting part 305 and the second mounting part 306 is lower than that of the equipment mounting part 304.

[0046] To facilitate the loading of sediment into the main body 1 of the water tank, a sediment chamber 401 is fixedly installed on the first mounting part 305. The sediment chamber 401 is used to store the treated sediment required for the experiment. A strip-shaped notch 402 is provided on the first mounting part 305, and a sand outlet (not shown in the attached drawing) is provided on the sediment chamber 401. The sand outlet communicates with the strip-shaped notch 402, and the sand outlet and the strip-shaped notch 402 are used to release the sediment in the sediment chamber 401. A chute (not shown in the attached drawing) is provided on the first mounting part 305, and a first baffle 4 is slidably installed in the chute. 03. When the first baffle 403 is in the initial position, it can block and close the strip-shaped notch 402. When the first baffle 403 is pulled away from the strip-shaped notch 402, the first baffle 403 no longer closes the strip-shaped notch 402. At this time, the mud and sand in the mud and sand chamber 401 flows down through the sand outlet and the strip-shaped notch 402 and can be put into the water tank body 1. The thickness of the mud and sand in the water tank body 1 needs to be 5cm. After the mud and sand are put into the water tank body 1, the mud and sand bed surface is leveled manually with a scraper to facilitate the subsequent laying and testing of tracer particles.

[0047] To facilitate the delivery of tracer particles into the water tank body 1, a tracer particle chamber 501 is fixedly installed on the second mounting part 306. The tracer particle chamber 501 stores tracer particles. In this embodiment, the tracer particles are 15μm hollow glass microspheres (density 1.03g / cm³). 3 The particle concentration in the water tank is controlled at 15-20 particles / mm. 2 Hollow glass microspheres are commonly used tracer particles. They exhibit good tracking ability in flow fields with different flow velocities. The density of the tracer particles is close to that of the test water, which can accurately reflect the water flow state under different flow velocities.

[0048] The second mounting part 306 is provided with a strip-shaped through hole 502. A release port (not shown in the attached drawing) is opened below the tracer particle chamber 501. The strip-shaped through hole 502 is fixedly connected and communicates with the release port of the tracer particle chamber 501. A delivery rod 503 is rotatably installed inside the strip-shaped through hole 502. The surface of the delivery rod 503 is provided with several unevenly distributed grooves 507. When the delivery rod 503 is stationary, its upper section is located inside the tracer particle chamber 501 and its lower section is located outside the tracer particle chamber 501. At this time, the tracer particles inside the tracer particle chamber 501 can fall into the grooves 507 located inside the chamber. When 03 rotates, the groove 507 carrying the tracer particles rotates out of the chamber. When the groove 507 rotates to the outside of the tracer particle chamber 501, the tracer particles it carries fall into the water tank body 1 under the action of gravity, realizing the release of tracer particles. One end of the release rod 503 extends out of the second mounting part 306 and is fixedly connected to the first pulley 504. The first pulley 504 and the release rod 503 are coaxially arranged. One end of the transmission belt 505 is sleeved on the first pulley 504, and the other end of the transmission belt 505 is sleeved on the second pulley 506. The second pulley 506 and the first track wheel 302 are coaxially fixedly arranged.

[0049] When the sliding frame 301 moves along the first slide rail 203, the first track wheel 302 rotates on the first slide rail 203. The rotation of the first track wheel 302 drives the second pulley 506, which is fixedly connected to it on the same axis, to rotate synchronously. The rotation of the second pulley 506 drives the first pulley 504 to rotate through the transmission belt 505. The rotation of the first pulley 504 drives the release rod 503, which is fixedly connected to it on the same axis, to rotate. When the tracer particles in the tracer particle chamber 501 fall into the groove 507 on the release rod 503, the groove 507 rotates with the rotation of the release rod 503, thus realizing the release of tracer particles into the water tank body 1.

[0050] During subsequent water injection, the incoming water flow often directly impacts the mud and sand bed surface, which can easily cause the mud and sand layer to be disturbed or damaged before the test begins, affecting the observation of the start-up process. To mitigate the impact of water pumped by pump 102 into the water tank body 1 on sediment and tracer particles, a flow-damping plate 201 is installed on the inlet 101 side of the water tank body 1. The flow-damping plate 201 is arc-shaped, and two sliding plates 202 are fixedly installed on the upper end of the flow-damping plate 201. The two sliding plates 202 are respectively slidably installed on two first slide rails 203 of the water tank body 1. There are two first slide rails 203, which are respectively fixed on both sides of the upper end of the water tank body 1. When the sliding plates 202 are slidably installed on the first slide rails 203, the flow-damping plate 201 can slide relative to the water tank body 1. When pump 102 injects different volumes of water into the water tank body 1, the water spray distance and landing point are different. Therefore, it is necessary to manually slide the sliding plates 202 along the first slide rails 203. The sliding plates 202 drive the flow-damping plate 201 to move synchronously, thereby adjusting the position of the flow-damping plate 201 to adapt to the landing point of the injected water.

[0051] The slide plate 202 is provided with screw holes, and the upper end of the water tank body 1 is provided with screw holes corresponding to the screw holes of the slide plate 202. By screwing bolts into the screw holes on the slide plate 202 and the water tank body 1, the position of the slide plate 202 can be locked, thereby limiting the position of the flow buffer 201. The lower end of the flow buffer 201 is located above the inner bottom surface of the water tank body 1.

[0052] Three baffles 204 are fixedly and equidistantly arranged on the surface of the flow buffer 201 along the extension direction of the flow buffer 201. The baffles 204 are used to deal with the impact of the water flow and reduce the force of the water flow. The baffles 204 are also arc-shaped, and one side of each baffle is fixedly connected to the surface of the flow buffer 201. The lower end of each baffle 204 is on the same horizontal plane as the upper end of the baffle 204 below it. The three baffles 204 completely cover the arc-shaped surface of the flow buffer 201. The above arrangement can ensure that when the water flow is injected into the water tank body 1, it first contacts and impacts the baffles 204. The surface of the flow buffer 201 is provided with three outlets 206. The installation position of the outlets 206 corresponds to the installation position of the baffles 204. The outlets 206 are located on one side of the baffles 204, and the bottom outlet 206 is located at the bottom of the flow buffer 201.

[0053] When the water pump 102 injects water into the main body of the water tank 1 through the inlet 101, the water flow first impacts the flow-damping plate 201 and the baffle plate 204 installed on it. Under the obstruction and guidance of the baffle plate 204, the kinetic energy of the water flow is effectively dissipated, and then it falls into the water storage section 205 formed between the flow-damping plate 201 and the side wall of the main body of the water tank 1 under the action of gravity. As the water injection continues, the water level in the water storage section 205 gradually rises. When the water level reaches the height of the bottom outlet 206, the water begins to flow smoothly into the main body of the water tank 1 through the outlet 206. As the water level rises further, the middle and upper outlets 206 begin to discharge water in sequence, eventually achieving synchronous overflow of the three outlets 206. This multi-stage outlet structure can adapt to the smooth release of water in the water storage section 205 under different water injection intensities. After this buffering process, the kinetic energy of the water flowing out of the outlet 206 has been significantly reduced. Compared with the initial jet from the inlet 101, the impact force on the mud and sand bed at the bottom of the water tank is greatly weakened, thus effectively protecting the integrity of the initial bed surface of the experiment.

[0054] To capture the tracer particles, an imaging unit is installed on the equipment mounting section 304. The imaging unit includes a high-speed camera 307 for capturing the movement trajectory of the tracer particles. The high-speed camera 307 is ball-jointed with the equipment mounting section 304 of the mounting bracket 303. The angle of the high-speed camera 307 can be adjusted through the ball joint between the high-speed camera 307 and the equipment mounting section 304. After the angle is adjusted, the position of the high-speed camera 307 is fixed by fixing bolts. The lens of the high-speed camera 307 is opposite to the main body of the water tank 1. The high-speed camera 307 is vertically located 1.5m above the water tank. The high-speed camera 307 adopts existing technology equipment with an imaging unit resolution of 2560×2016 pixels, a maximum frame rate of 2000fps, and an adjustable lens focal length. The shooting range of the high-speed camera 307 covers a 1m wide cross section of the water tank.

[0055] To illuminate the tracer particles, an extension frame 309 is fixedly connected to one side of the equipment mounting section 304. One end of the extension frame 309 is fixedly connected to the equipment mounting section 304. The extension frame 309 is used to install the laser illumination unit. The extension frame 309 is located on the side of the water tank body 1, so the laser illumination unit is also located on the side of the water tank body 1.

[0056] The laser illumination unit includes a high-energy pulsed laser 308, which is fixedly mounted on an extension frame 309. The high-energy pulsed laser 308 is located on the side of the main body 1 of the water tank, with its laser emission port facing the side of the main body 1. The high-energy pulsed laser 308 is a readily available 15W continuous laser capable of emitting 532nm green light. It is equipped with a sheet light lens to form a 0.5mm thick sheet light, illuminating an area of ​​600×500mm. 2It can cover different sediment initiation observation areas. The high-energy pulsed laser 308 illuminates the tracer particles, ensuring clear imaging of the tracer particles and facilitating the high-speed camera 307 mentioned above to capture the tracer particles.

[0057] The indoor water tank sediment initiation velocity measurement system also includes a data processing unit, which is a digital computer. This data processing unit is communicatively connected to a high-speed camera 307 and is used to receive tracer particle trajectory images captured by the high-speed camera 307. The data processing unit has built-in existing PIV dedicated analysis software, which can perform image calibration, tracer particle displacement calculation, velocity vector generation, and flow field visualization functions to meet the flow field data analysis needs of sediments of different particle sizes during the initiation process.

[0058] For image calibration, the data processing unit uses a standard-sized calibration plate to convert image pixel coordinates into actual physical dimensions, with a calibration error of no more than 0.5%. The data processing unit calculates the particle displacement in the image frame using the cross-correlation algorithm of the PIV analysis software, thereby obtaining the velocity vector of each measurement point in the flow field, which is suitable for velocity analysis under various particle size sediment initiation conditions.

[0059] The data processing unit adopts an industrial-grade computer platform, equipped with 16GB of memory and a dedicated graphics card, and is equipped with DynamicStudio PIV analysis software, which supports image calibration, cross-correlation analysis and flow velocity vector generation functions. The calibration error is controlled within 0.5%, which can effectively process the flow field data of sediments of different particle sizes during the initiation process.

[0060] After completing the laying of sediment and tracer particles, a flow field test area is selected, which is the working area of ​​the laser illumination unit and the imaging unit. The sliding frame 301 is manually pushed to the top of the flow field test area, and a 10cm×10cm calibration plate is placed in the flow field area. The shooting angle is adjusted by the ball-mounted high-speed camera 307. Then, the calibration image is captured by the high-speed camera 307 and imported into the data processing system to complete the calibration.

[0061] Traditional water tanks lack the ability to regulate flow field, especially in terms of regulating the outflow rate. This makes it difficult to control the outflow rate to match the inflow rate, resulting in an inability to establish a dynamic balance between inflow and outflow, thus affecting the stability of the flow field within the tank. To regulate the outflow of water from the main body 1 of the water tank and ensure a stable dynamic balance between it and the inflow rate, the other side of the main body 1 opposite the inlet 101 is fixedly connected to the outlet tank 605. A through-hole plate 601 is detachably installed on this side using bolts.

[0062] The perforated plate 601 has three rows of through holes 602 arranged vertically at equal intervals on its surface, with four through holes 602 in each row, totaling twelve through holes 602, forming four longitudinal channels, each containing three through holes 602. Corresponding to the four rows of through holes 602, four rotating rods 603 are rotatably mounted on the inner side of the perforated plate 601, each rotating rod 603 being positioned along the longitudinal centerline of a row of through holes. Each rotating rod 603 is fixedly mounted with three disc-shaped baffles 604, the positions of which correspond one-to-one with the three through holes 602 in its row, and the rotating rods 603 and baffles 604 are concentrically fixed. In the initial state, each baffle 604 completely blocks the corresponding through hole 602, preventing water flow.

[0063] After the upper end of the rotating rod 603 extends out of the through-hole plate 601, it is fixed to four driven gears 606 respectively. Each driven gear 606 meshes with a transmission gear 607 rotatably mounted on the through-hole plate 601. Adjacent driven gears 606 are linked through a transmission gear 607, thus forming a gear transmission system that enables the four rotating rods 603 to rotate synchronously and in the same direction.

[0064] A rocker arm 609 is provided on the outer side of the through-hole plate 601, which is coaxially fixed with the driven gear 606 located on the side. By rotating the rocker arm 609, the driven gear 606 can be driven to rotate, which in turn drives the other driven gears 606 to rotate synchronously through the transmission gear 607, ultimately causing all rotating rods 603 and their baffles 604 to rotate uniformly. When the baffle 604 rotates a certain angle from its initial fully blocked position, the through holes 602 in the corresponding row gradually open, allowing water to flow into the water tank 605 through the through holes 602. The maximum rotation angle of the baffle 604 is 90 degrees. At this position, the baffle 604 is parallel to the water flow direction, the flow area is the largest, and the drainage volume reaches its peak. As the rotation angle of the baffle 604 decreases, its blocking area on the through holes 602 increases, and the drainage volume decreases accordingly. When the water inlet 101 has a large flow rate, the rotation angle of the baffle 604 is increased to increase the water outflow. When the water inlet 101 has a small flow rate, the rotation angle of the baffle 604 is decreased to decrease the water outflow.

[0065] This structure, through the corresponding arrangement of four rotating rods 603 and four rows of through holes 602, combined with a linkage gear system, achieves unified control of all drainage channels. The total outflow can be flexibly adjusted by simply operating the rocker arm 609, thus quickly matching the inflow rate and effectively maintaining the stability of the flow field inside the tank, providing reliable hydraulic conditions for sediment initiation experiments.

[0066] A mud outlet 701 is provided on one side of the main body of the water tank 1. The mud outlet 701 is located below the through plate 601. By opening the mud outlet 701, the mud and sand in the main body of the water tank 1 can be discharged.

[0067] Please see Figure 1This invention proposes a method for measuring the initiation velocity of sediment in an indoor water tank. The aforementioned indoor water tank sediment initiation velocity measurement system is used to implement this method.

[0068] Step 1: To improve the experimental accuracy of tracer particles, sediment pretreatment is required: Select natural or artificial sediment to be tested, and sieve it according to the corresponding standard sieve specifications to obtain sediment within the target particle size range; clean it with an ultrasonic cleaner for 10 minutes to remove surface impurities; optimize the treatment according to the characteristics of the sediment. For example, if the sediment contains a lot of reflective components (such as quartz), add water-based dye to the cleaned sediment and stir for 30 minutes, then dry it and add it to the sediment bin 401.

[0069] Step 2, Experimental Preparation: First, lay a 5cm thick layer of mud and sand inside the main body 1 of the water tank. Specifically, pull the first baffle 403 away from the strip-shaped notch 402, so that it no longer closes the notch 402. The mud and sand in the mud and sand chamber 401 flows through the sand outlet and the strip-shaped notch 402 and is then released into the main body 1 of the water tank. At this time, manually push the sliding frame 301 to move it back and forth along the extension direction of the first slide rail 203 for one stroke. The sliding frame 301 drives the first mounting part 305 and the mud and sand chamber 401 fixed thereon to move synchronously, thereby achieving uniform distribution of mud and sand along the length of the water tank. After the mud and sand are laid, push the first baffle 403 in the opposite direction to close the strip-shaped notch 402 again, preventing the mud and sand from falling further. Finally, use a scraper to level the mud and sand bed surface for subsequent laying and testing of tracer particles.

[0070] Fill the tank body 1 with clean water, and control the water output of the water pump 102 to control the initial flow rate so that the water slowly submerges the mud and sand and soaks for three hours.

[0071] After the sediment has been soaked, a layer of tracer particles is evenly spread on top of the sediment. In operation, the sliding frame 301 is pushed to reciprocate along the first slide rail 203 for one stroke. At this time, the first track wheel 302 on the sliding frame 301 rotates, driving the coaxially fixed second pulley 506 to rotate, which in turn drives the first pulley 504 to rotate via the transmission belt 505. The first pulley 504 drives the delivery rod 503 to rotate. The groove 507 on the delivery rod 503 receives the tracer particles during rotation and delivers them into the water tank body 1. Simultaneously, the second mounting part 306 moves with the sliding frame 301, achieving a uniform spread of the tracer particles on the sediment.

[0072] Push the sliding frame 301 to position the high-speed camera 307 above the test area and the high-energy pulsed laser 308 to the side of the test area;

[0073] After the tracer particles are laid, a 10cm×10cm calibration plate is placed in the flow field area, and a high-speed camera 307 is used to capture calibration images, which are then imported into the data processing system to complete the image calibration.

[0074] Step 3, Flow Velocity Measurement: After image calibration, restart the water pump 102 and manually rotate the rocker arm 609 to set the angle between the baffle 604 and the through hole 602. The rocker arm 609 drives the driven gear 606 to rotate, and through the meshing transmission gear 607, the four driven gears 606 rotate synchronously in the same direction. When the baffle 604 rotates a certain angle from its initial fully blocked position, the corresponding through holes 602 gradually open, allowing water to flow into the outlet tank 605. By flexibly adjusting the total outflow, it can quickly match the inflow rate, effectively maintaining the stability of the flow field inside the tank, adjusting the water level elevation in the main body of the tank 1, and providing reliable hydraulic conditions for the sediment initiation experiment.

[0075] At the start of the experiment, a high-energy pulsed laser 308 was activated to illuminate the flow field plane, causing the tracer particles to produce refracted light spots. Data was then collected following these steps (existing):

[0076] When a small amount of sediment begins to move on the sediment bed surface of the main body of the water tank 1, that is, when sporadic sediment rolling (weak movement) occurs, the high-speed camera 307 is activated to continuously capture 10 seconds of flow field images at a frame rate of 1000fps, and the water level data is recorded simultaneously.

[0077] Gradually increase the flow rate. When local sediment initiation occurs, that is, when sediment initiation occurs in 10%–50% of the bed surface (medium-term initiation), repeat the above shooting and recording.

[0078] Continue to increase the flow rate. When sediment is stirred up in most areas, that is, when sediment is stirred up in more than 50% of the bed surface (general stirring), take pictures and record the water level again.

[0079] Step 4: Data Processing: Import the images captured by the imaging unit into the PIV post-processing software in the data processing unit, and perform Gaussian filtering for noise reduction and lens distortion correction in sequence; set a 32×32 pixel analysis window, and calculate the particle displacement (Δt=1ms) based on the cross-correlation algorithm; calculate the flow velocity (Δx is the particle displacement) according to the formula V=Δx / Δt, and generate a visualized flow field vector diagram; statistically analyze the cross-sectional average flow velocity under different starting conditions to determine the critical starting flow velocity of this group of sediments. Repeat the above steps with sediments of different particle sizes to complete multiple sets of experiments.

[0080] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the starting speed of sediment in an indoor water tank, characterized in that, include: Step 1: Sediment pretreatment: Select the sediment to be tested, obtain the sediment within the target particle size range through sieving, clean it, optimize it according to the characteristics of the sediment, and dry it for later use. Step 2, Experimental Preparation: Spread the treated silt evenly at the bottom of the water tank and level the surface; inject clean water into the water tank, control the initial flow rate to slowly submerge the silt, and soak for the preset time; install and debug the imaging unit and laser illumination unit to ensure that the light plane covers the silt initiation observation area; release tracer particles and complete image calibration through the data processing unit; Step 3, Flow velocity measurement: Adjust the flow rate to the preset value. After the water flow stabilizes, adjust the water level elevation through the water level control device. Observe the sediment movement status on the bed surface. When a small amount of sediment starts to move on the bed surface of the water tank, that is, when a weak movement of sporadic sediment rolls occurs, start the imaging unit and laser illumination unit. The imaging unit continuously captures 10-second flow field images at a frame rate of 1000fps, and records the water level data simultaneously. Gradually increase the flow rate. When local sediment initiation occurs, that is, when sediment initiation occurs in 10%–50% of the bed surface, repeat the above shooting and recording. Continue to increase the flow rate. When sediment is stirred up in most areas, that is, when sediment is stirred up in more than 50% of the bed surface, take pictures and record the water level again. Step 4: Data Processing: Import the images captured by the imaging unit into the PIV post-processing software in the data processing unit, and perform Gaussian filtering noise reduction and lens distortion correction in sequence; set a 32×32 pixel analysis window, calculate particle displacement based on the cross-correlation algorithm; calculate the flow velocity according to the formula V=Δx / Δt, and generate a visualized flow field vector diagram; statistically analyze the cross-sectional average flow velocity under different starting conditions, determine the critical starting flow velocity of the sediment group, and repeat the above steps with different sediment particle sizes to complete multiple sets of experiments.

2. The method for measuring the starting speed of sediment in an indoor water tank according to claim 1, characterized in that: In step two, the soaking time for the mud and sand is set at three hours.

3. An indoor water tank sediment initiation velocity measurement system, used to implement the indoor water tank sediment initiation velocity measurement method of claim 1, characterized in that... include: The main body (1) of the water tank used to simulate the water flow environment is made of transparent material. Different particle sizes of test sand can be laid at the bottom. The two ends are respectively equipped with water pumps (102) with adjustable flow rate and drainage adjustment units for controlling the water level in the main body (1). The water flow parameters can be adjusted according to the test requirements to ensure the stability of the flow field. One side of the main body (1) is connected to the output end of the water pump (102) through the water inlet (101) set on it. The input end of the water pump (102) is connected to the water storage tank (103). The water storage tank (103) is connected to the other side of the main body (1) through the water pipe, so that the main body (1), water pump (102), and water storage tank (103) form a circulation. The imaging unit includes a high-speed camera (307), which is mounted above the main body of the water tank (1) and can clearly capture the motion trajectory of the tracer particles in the flow field. The laser illumination unit includes a high-energy pulsed laser (308), which can emit a uniform sheet light beam to illuminate the target flow field plane inside the water tank body (1). The sheet light plane is perpendicular to the shooting direction of the high-speed camera (307) to ensure clear imaging of the tracer particles. The tracer particle delivery device includes a tracer particle chamber (501) for uniformly delivering tracer particles into the water flow. The tracer particles can accurately reflect the water flow motion state at different flow velocities. The sediment delivery device includes a sediment bin (401) for uniformly delivering test sediment into the main body of the water tank (1); An adjustable bracket is provided with a first track wheel (302), which contacts the first slide rail (203) at the upper end of the water tank body (1). An imaging unit, a laser illumination unit, a tracer particle chamber (501), and a sediment chamber (401) are placed on the adjustable bracket. The adjustable bracket can adjust the spatial position of the imaging unit and the laser illumination unit relative to the water tank body (1) to adapt to different measurement ranges. The adjustable bracket can adjust the placement position of tracer particles and sediment in the tracer particle chamber (501) and the sediment chamber (401). The data processing unit is a digital computer connected to a high-speed camera (307). It has built-in PIV-specific analysis software, which can perform image calibration, particle displacement calculation, flow velocity vector generation and flow field visualization functions, and is adapted to the flow field data processing needs of sediments of different particle sizes when they start.

4. The indoor water tank sediment starting speed measurement system according to claim 3, characterized in that: It also includes a sediment pretreatment unit for cleaning, screening and other treatments of the sand used in the experiment.

5. The indoor water tank sediment starting speed measurement system according to claim 3, characterized in that: The adjustable bracket includes a sliding frame (301) slidably mounted on the main body (1) of the water tank, and a mounting frame (303) fixed on the sliding frame (301) and provided with an equipment mounting part (304), a first mounting part (305) and a second mounting part (306); a sediment bin (401) for discharging sediment is fixed on the first mounting part (305), a tracer particle bin (501) for discharging tracer particles is fixed on the second mounting part (306), a laser illumination unit for irradiating tracer particles is fixed on the equipment mounting part (304), and an imaging unit for capturing the trajectory of tracer particles is ball-connected on the equipment mounting part (304); The high-speed camera (307) in the imaging unit is ball-connected to the equipment mounting part (304) of the sliding frame (301), and the lens of the high-speed camera (307) is opposite to the main body of the water tank (1); The high-energy pulsed laser (308) in the laser lighting unit is fixedly mounted on the extension frame (309). One end of the extension frame (309) is fixedly connected to the side of the equipment installation part (304). The high-energy pulsed laser (308) is located on the side of the water tank body (1), and its laser emission port is opposite to the side of the water tank body (1).

6. The indoor water tank sediment starting speed measurement system according to claim 3, characterized in that: The main body of the water tank (1) is also equipped with a buffer unit: The buffer unit includes: a flow-damping plate (201) slidably mounted on a first slide rail (203), the flow-damping plate (201) having an arc-shaped cross-section, two sliding plates (202) fixedly mounted on the upper end of the flow-damping plate (201) and slidably mounted on the first slide rail (203) of the water tank body (1), the sliding plates (202) having screw holes, the upper end of the water tank body (1) having screw holes corresponding to the screw holes of the flow-damping plate (201), and three baffle plates (204) fixedly mounted at equal intervals on the surface of the flow-damping plate (201) according to the extension direction of the flow-damping plate (201). The cross-section of the baffle plate (204) is arc-shaped, and one side of it is fixedly connected to the surface of the flow buffer plate (201). The lower end of each baffle plate (204) is on the same horizontal line as the upper end of the baffle plate (204) below it. The surface of the flow buffer plate (201) is provided with three outlets (206). The installation position of the outlets (206) corresponds to the installation position of the baffle plate (204). The outlets (206) are located on one side of the baffle plate (204), and the lowermost outlet (206) is located at the bottom of the flow buffer plate (201).

7. The indoor water tank sediment starting speed measurement system according to claim 3, characterized in that: The main body of the water tank (1) is also provided with a drainage adjustment unit: including a through-hole plate (601) fixed on the drainage side of the main body of the water tank (1), a number of through holes (602) for drainage are opened on the through-hole plate (601), a number of rotating rods (603) are rotatably installed in the through-hole plate (601), a number of baffles (604) for opening and closing the corresponding through holes (602) are fixed on the rotating rods (603), one end of each rotating rod (603) is fixed to the driven gear (606), and the adjacent driven gears (606) are driven by the transmission gear (607) to realize the synchronous rotation of the baffles (604) to adjust the drainage volume.

8. The indoor water tank sediment starting speed measurement system according to claim 5, characterized in that: A sediment bin (401) is fixedly installed on the first mounting part (305). A strip-shaped notch (402) is provided on the surface of the first mounting part (305). The sand outlet of the sediment bin (401) is connected to the strip-shaped notch (402). The strip-shaped notch (402) is used to release the sediment in the sediment bin (401). A sliding groove is provided on the first mounting part (305). A first baffle (403) is slidably installed in the sliding groove. When the first baffle (403) is in the initial position, it blocks the strip-shaped notch (402).

9. The indoor water tank sediment starting speed measurement system according to claim 5, characterized in that: The second mounting part (306) is fixedly provided with a tracer particle chamber (501). The second mounting part (306) is provided with a strip-shaped through hole (502). The strip-shaped through hole (502) is fixedly connected and communicates with the release port of the tracer particle chamber (501). A delivery rod (503) is rotatably provided in the strip-shaped through hole (502). The surface of the delivery rod (503) is provided with several unevenly distributed grooves (507). One end of the delivery rod (503) extends out of the second mounting part (306) and is fixedly connected to the first pulley (504). One end of the transmission belt (505) is sleeved on the first pulley (504). The other end of the transmission belt (505) is sleeved on the second pulley (506). The second pulley (506) is coaxially fixedly provided with the first track wheel (302).

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