Wind tunnel wind erosion particle starting wind speed test device, test system and test method

Abstract

The present invention discloses a wind tunnel wind erosion particle starting wind speed test device, test system and test method. The wind erosion particle starting wind speed test device comprises a sand table (1), on which a plurality of test units separated from each other are arranged, each test unit comprises a sand-laying section, a contraction section, a shooting channel (8) and a sand collecting trough (2) arranged in sequence along the wind direction, the sand-laying section is used to lay sand for the experiment, the widths of the sand-laying section, the contraction section and the shooting channel (8) decrease in sequence, the shooting channel (8) is provided with a shooting area (5) corresponding to a micro high-speed camera (4), the sand collecting trough (2) has a V-shaped groove bottom, and the V-shaped groove bottom is distributed with a sand identification area (3). Compared with the single method for measuring the starting wind speed in the past, the present invention is more standardized, objective and accurate, and basically solves the defects encountered in various current measuring methods, and provides a scientific and practical new device and method for accurately defining the starting wind speed of sand particles in a wind tunnel.

Description

Technical Field

[0001] The invention belongs to the technical field of measuring the starting wind speed of particles in a wind-sand flow, and in particular relates to a wind-eroded particle starting wind speed testing device, a testing system and a testing method for a wind tunnel. Background Art

[0002] In the study of wind and sand physics, the generation mechanism of wind and sand, that is, the starting mechanism of sand particles under the action of wind field, is a basic and important research topic. The process of surface sand particles breaking away from the surface and starting to move under the action of wind field is called the start of sand particles, which marks the beginning of surface wind erosion. Wind erosion is one of the main driving forces of land degradation in arid and semi-arid desert areas, and the starting wind speed is a key factor affecting wind erosion. Therefore, the starting wind speed of sand particles has always been highly concerned by researchers, and it has a fundamental significance for the study of wind and sand movement.

[0003] For the starting wind speed of sand particles, Bagnold

[1954] proposed two concepts: fluid starting value and impact starting value. The so-called fluid starting wind speed refers to the critical wind speed when there is no sand in the incoming flow and the sand particles on the bed surface start to move completely due to the direct effect of the wind field on the sand particles on the sand bed surface. If there are sand particles in the incoming flow, these sand particles will hit the sand bed surface, causing the sand particles on the bed surface to creep or jump. In this case, the movement of the sand particles on the bed surface is mainly caused by the impact of the original sand particles in the airflow. The critical wind speed at this time is called the impact starting wind speed.

[0004] Accurately measuring the starting wind speed of sand particles is of great significance for the study of sand physics. However, due to the kinematic characteristics of sand particles at the moment of starting, such as instantaneous, high speed, and trace, the starting wind speed value is an experimental constant that is difficult to accurately measure. Currently, the methods used by various institutions are different, and there is no unified standard, device or instrument to measure this value.

[0005] In the wind tunnel simulation experiment of the starting wind speed, the acquisition frequency of the wind speed sensor is generally 1HZ-100HZ. As long as the exact time corresponding to the sand particle starting moment is known, the corresponding starting wind speed value can be found in the time series wind speed data or the starting friction wind speed value can be calculated. Therefore, in the specific experimental operation link, the determination of the starting wind speed value of the wind erosion particles is completely based on the determination of the exact time corresponding to the starting moment.

[0006] Currently, there are five main methods for measuring starting wind speed: naked eye identification method, tape method, sheet light source observation method, wind erosion sensor, and fork-type photoelectric sensor, but each of these methods has its own defects.

[0007] The drawback of the human eye recognition method is that each person's naked eye recognition ability is limited and there are great individual differences. For the same starting process, different people may get very different starting wind speed results. Even if the same person observes, the subjective judgment standard of naked eye recognition will be different in each group of experiments, resulting in inaccurate and inconsistent results.

[0008] The disadvantage of the tape method is that when the sand particles start to move, the number of particles is very small and the speed is fast, so it is difficult for them to stick to the tape; the tape is usually pasted horizontally on the floor of the wind tunnel, and the width along the axis of the wind tunnel test section is only a few centimeters. After the high-speed moving sand particles come into contact with the tape, it is very likely that they will not be stuck, or will directly pass over the tape. Therefore, the reliability is poor in accurately measuring the starting moment of sand particles in the wind and sand flow;

[0009] The defect of the sheet light source method is that although the laser sheet light source has high brightness, it is only 1-2mm thick. When it is deployed, the fan-shaped sheet light source is projected on the central axis of the experimental section. When sand enters the light sheet, a bright imaging effect will be produced, which is used to measure the starting moment of the wind and sand particles. However, the light sheet is only 1-2mm thick. If the sand particles that have started do not pass through this thin layer of space, the occurrence of the start cannot be monitored. Therefore, it is often only when obvious saltation or wind and sand flow occurs that the fast-flying sand particles can be captured in the light sheet. Therefore, the starting wind speed measured by the sheet light source method is often greater than the actual starting wind speed value of the sand particles.

[0010] Wind erosion sensors are widely used in field and wind tunnel experiments to measure the number of impact particles and the impact kinetic energy of each particle (dyne-cm) during the wind erosion process. They have the advantages of high-frequency continuous acquisition. However, their piezoelectric sensors do not respond to the impact of particles with smaller particle size or kinetic energy, and are more suitable for high-intensity sand transport in wind and sand flows with larger particle size and kinetic energy. In the experiment to measure the starting wind speed of particles, when the particles start to start, the number of particles in the airflow (usually in the single digit) and the impact kinetic energy of the particles themselves are very small, and generally cannot stimulate the wind erosion sensor to respond. Therefore, this sensor is not suitable for defining the instant of wind and sand starting.

[0011] The working principle of the fork-type photoelectric sensor is that when moving sand blocks the direct laser light, the trigger light will light up. However, in actual use, it is found that only when a large amount of wind-eroded sand flies by can the thin laser light be blocked, and the trigger light will light up at this time. Therefore, it is not suitable for situations where only a very small amount of sand passes through at the starting moment.

[0012] In addition, in the wind tunnel simulation experiment of the starting wind speed, it is often necessary to measure the starting wind speed values ​​of several different sediments or the same sediments but with different particle sizes. Traditionally, only one particle can be tested after the starting test is completed before the next one. For the impact starting test, since the amount of sand falling in the sand supply device cannot be completely uniform, the supply of impact particles cannot be completely consistent in each group of experiments, resulting in a large deviation in the final result of the impact starting wind speed;

[0013] The above analysis shows that the various methods currently used to measure the starting wind speed have certain defects and cannot objectively and accurately measure the starting wind speed value of wind-eroded sand. Summary of the invention

[0014] The main purpose of the present invention is to provide a wind tunnel wind erosion particle starting wind speed test device, test system and test method to overcome the shortcomings of the prior art.

[0015] To achieve the aforementioned object of the invention, the technical solution adopted by the embodiment of the present invention includes:

[0016] An embodiment of the present invention provides a wind erosion particle starting wind speed test device for a wind tunnel, comprising a sand table, on which a plurality of test units separated from each other are arranged, each test unit comprising a sand-laying section, a contraction section, a shooting channel and a sand collecting trough arranged in sequence along the wind direction, the sand-laying section is used to lay experimental sand, the widths of the sand-laying section, the contraction section and the shooting channel decrease in sequence, a shooting area corresponding to a miniature high-speed camera is provided in the shooting channel, the sand collecting trough has a V-shaped groove bottom, and a sand identification area is distributed on the V-shaped groove bottom.

[0017] Furthermore, the sand tray is provided with a plurality of vertical partitions and / or sand scraping boards; the plurality of vertical partitions are spaced apart from each other, thereby separating a plurality of test units on the sand tray; the sand scraping boards are used to level the surface of the experimental sand laid in a plurality of sand-laying sections.

[0018] Furthermore, the wind tunnel wind erosion particle starting wind speed test device also includes an upwind extension section, and the upwind extension section and the sand table are arranged in sequence along the wind direction.

[0019] Furthermore, the wind tunnel wind erosion particle starting wind speed testing device also includes a lifting platform connected to the sand table.

[0020] Furthermore, when in operation, the wind erosion particle starting wind speed test device is arranged in the wind tunnel test section, and the sand surface of the experimental sand in each sand-laying section is on the same horizontal plane as the surface of the bottom plate of the test section, the surface of the upwind extension section, and the bottom surface of each vertical partition, and the front edge of the wind erosion particle starting wind speed test device is seamlessly connected to the bottom plate of the wind tunnel.

[0021] Furthermore, a magnifying glass is connected to the lower part of the sand collecting tank, and the magnifying glass is arranged corresponding to the sand identification area.

[0022] Furthermore, the wind tunnel wind erosion particle starting wind speed testing device also includes a camera bracket for arranging a miniature high-speed camera above a corresponding shooting area.

[0023] The embodiment of the present invention further provides a wind tunnel wind erosion particle starting wind speed test system, comprising a wind tunnel and the wind tunnel wind erosion particle starting wind speed test device described above which cooperates with the wind tunnel.

[0024] Furthermore, the wind tunnel wind erosion particle starting wind speed test system also includes a gradient pitot tube, which is connected to a data logger and a computer; the gradient pitot tube is arranged on the central axis of the experimental section 1-3m away from the upper wind direction edge of the sand table, and is used to measure the wind speed at multiple heights.

[0025] The embodiment of the present invention further provides a method for testing the starting wind speed of wind erosion particles in a wind tunnel, comprising:

[0026] (1) Providing the wind erosion particle starting wind speed test system;

[0027] (2) A notch is cut in the middle of the bottom plate of the wind tunnel test section, and the wind erosion particle starting wind speed test device is placed in the notch position, and the surface of the upwind extension section is flush with the surface of the bottom plate of the test section;

[0028] (3) laying different types or particle sizes of experimental sand on each sand-laying section, and leveling the sand surface of each sand-laying section with a sand scraper, while ensuring that each sand surface is at the same level as the bottom plate of the experimental section, and then cleaning the sand around the sand tray and at the bottom of the sand collection tank, and placing micro high-speed cameras above each shooting area to aim at the corresponding shooting area for aerial photography;

[0029] (4) A gradient pitot tube is set at the central axis of the experimental section 1-3 m away from the windward edge of the sand table to measure the wind speed at different heights, and the gradient pitot tube is connected to the data acquisition instrument and computer outside the experimental section;

[0030] (5) Experiment: First, start the fan and turn on the micro high-speed camera. The observer holds a strong flashlight next to the sand collection tank and observes the bottom of the tank through a magnifying glass. If experimental sand is found at the bottom of the tank, the exact time and the corresponding test unit number are recorded immediately. During the process of slowly increasing wind speed, the micro high-speed camera also continuously records high-definition images of the shooting area. Continue to increase the wind speed until the start of each test unit is monitored and recorded at the bottom of the sand collection tank, and then turn off the fan.

[0031] (6) Method for determining the starting wind speed and starting friction wind speed: Based on the video playback, determine the exact time when sand particles pass through each shooting area. If the time is earlier than the time recorded by the observer, the time determined by the video shall prevail. If the time recorded by the observer is earlier, the time determined by the observer shall prevail. Then, based on the earlier time data, find the starting wind speed value corresponding to each test unit from the time series wind speed data of the gradient pitot tube at the entrance of the wind tunnel test section, or use the gradient wind speed data of the gradient pitot tube to calculate the starting friction wind speed value by the least squares method.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The wind tunnel wind erosion particle starting wind speed test device, test system and test method of the present invention have the advantages that, at the beginning of starting, the speed of the sand particles is relatively low and they are basically in a ground-closed motion state. Almost all the starting sand particles fall into the V-shaped sand collecting groove and are concentrated in the linear area of ​​the V-shaped groove bottom identification area. The highly transparent ultra-white glass and the 10x rectangular magnifying glass allow the observer to easily find the sand particles at the bottom of the groove. When a few sand particles are found at the bottom of the groove, the exact time at that moment is recorded as the starting time. According to the starting time, the corresponding starting wind speed value is found in the wind speed data of the time series, or the starting friction wind speed value is calculated according to the wind speed gradient data. Compared with the starting process of the sand particles on the bed surface directly observed by the human eye, this method has the advantages of easy identification and high accuracy. Therefore, the experimental results are more objective, which basically solves the defects encountered in various current measurement methods and provides a scientific and practical new device and method for accurately defining the starting wind speed of sand particles in the wind tunnel.

[0034] (2) The wind tunnel wind erosion particle starting wind speed test device of the present invention has a closing design of the vertical partition of the sand table, which allows a small amount of sand to be concentrated through the narrow shooting channel, thereby increasing the number of moving sand particles per unit area in the shooting area, making it easier to identify the moving sand particles in the image playback, increasing the probability of identifying the sand particles in the image at the moment of passing, improving the accuracy of the starting time definition, and then improving the accuracy of the starting wind speed value.

[0035] (3) The wind tunnel wind erosion particle starting wind speed test device of the present invention has test units separated by vertical partitions of the sand table corresponding to independent high-speed cameras and V-shaped collection troughs in the downwind direction. This design makes the test units, movement paths and observation and identification systems of different types of sand particles completely independent and non-interfering with each other, thereby realizing synchronous and accurate observation of the starting wind speeds of various particles.

[0036] (4) The wind tunnel wind erosion particle starting wind speed test device, test system and test method of the present invention can simultaneously carry out wind erosion starting wind speed experiments on multiple groups of sediments. Since the experiments are carried out simultaneously and synchronously on the same sand table, the boundary conditions including the slight fluctuation of the wind speed on the sand bed surface are almost the same. In particular, for the determination of the impact starting wind speed under the condition of sand supply from the upwind direction, it can be ensured that the concentration and energy of the impact sand particles acting on the bed surface are basically the same, so the result is more accurate. Since the experiments are carried out simultaneously on multiple groups of sediments, it is only necessary to lay out the bed surface once to complete the determination of the starting wind speeds of multiple particles, thus avoiding repeated layout of the bed surface, shortening the experimental time, and improving the time efficiency of such experiments. In addition, when the starting time values ​​obtained by the image and the V-shaped observation slot are inconsistent, the smaller value is taken as the final result, thereby realizing the synchronous application of the two observation methods, playing a double insurance effect of mutual complementation and verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a schematic structural diagram of a wind speed test device for wind erosion particles used in a wind tunnel in one embodiment of the present application.

[0039] Figure 2 yes Figure 1 Schematic diagram of the specific structure of the middle sand scraper.

[0040] Figure 3 Schematic diagram of a wind tunnel wind erosion particle starting wind speed test system in one embodiment of the present application.

[0041] Explanation of reference numerals: 1. Sand table; 2. V-shaped starting sand collecting trough; 3. V-shaped trough bottom identification area; 4. Miniature high-speed camera; 5. Shooting area; 6. Vertical partition of sand table; 7. Upwind extension section; 8. Shooting channel; 9. Camera bracket; 10. Sand scraper; 11. Magnifying glass; 12. Gradient Pitot tube; 13. Data acquisition instrument; 14. Computer; 15. Central axis of experimental section; 16. Lifting platform. DETAILED DESCRIPTION

[0042] The present invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are only exemplary of the present invention, which can be embodied in various forms. Therefore, the specific functional details disclosed herein should not be interpreted as limiting, but only as the basis of the claims and as a representative basis for teaching those skilled in the art to adopt the present invention in different ways in virtually any appropriate detailed embodiment.

[0043] In view of the fact that various methods currently used for measuring the starting wind speed all have certain defects and cannot objectively and accurately measure the starting wind speed value of wind-eroded sand particles, the inventors have proposed the technical solution of the present invention after long-term research and a large number of experiments, providing a scientific and practical experimental device and method for accurately measuring the starting wind speed of sediment particles in a wind tunnel. The technical solution of the present invention will be explained in more detail as follows.

[0044] One aspect of an embodiment of the present invention provides a wind erosion particle starting wind speed test device for a wind tunnel, comprising a sand table, on which a plurality of test units separated from each other are arranged, each test unit comprising a sand-laying section, a contraction section, a shooting channel and a sand collecting trough arranged in sequence along the wind direction, the sand-laying section is used to lay experimental sand, the widths of the sand-laying section, the contraction section and the shooting channel decrease in sequence, a shooting area corresponding to a miniature high-speed camera is provided in the shooting channel, the sand collecting trough has a V-shaped groove bottom, and a sand identification area is distributed on the V-shaped groove bottom.

[0045] In some preferred embodiments, the sand tray is provided with a plurality of vertical partitions and / or sand scraping boards; the plurality of vertical partitions are spaced apart from each other, thereby separating a plurality of test units on the sand tray; the sand scraping boards are used to level the surface of the experimental sand laid in a plurality of sand-laying sections.

[0046] In some preferred embodiments, the wind erosion particle starting wind speed testing device further includes an upwind extension section, and the upwind extension section and the sand table are arranged in sequence along the wind direction.

[0047] In some preferred embodiments, the wind erosion particle starting wind speed testing device further includes a lifting platform connected to the sandbox.

[0048] In some preferred embodiments, when in operation, the wind erosion particle starting wind speed test device is arranged in the wind tunnel test section, and the sand surface of the experimental sand in each sand-laying section is on the same horizontal plane as the surface of the bottom plate of the test section, the surface of the upwind extension section, and the bottom surface of each vertical partition, and the leading edge of the wind erosion particle starting wind speed test device is seamlessly connected to the bottom plate of the wind tunnel.

[0049] In some preferred embodiments, both ends of the sand scraping plate are arranged on vertical partitions, and the bottom edge is located at the sand surface of the experimental sand in multiple sand-laying sections.

[0050] In some preferred embodiments, the sandbox is a rectangular sunken structure with a length of 70 cm, a width of 30-45 cm, and a depth of 4 cm.

[0051] In some preferred embodiments, the length of the sand-topped section is 70 cm and the width is 10-15 cm.

[0052] In some preferred embodiments, the width of one end of the contraction section is equal to that of the corresponding sand-laying section, the width of the other end is equal to that of the corresponding shooting channel, and the length is 8 cm.

[0053] In some preferred embodiments, the shooting channel has a length of 12 cm and a width of 3-5 cm.

[0054] In some preferred embodiments, the height of the vertical partition is 3 cm.

[0055] In some preferred embodiments, the shooting area is a circular area with a radius of 3-5 cm.

[0056] In some preferred embodiments, the upwind extension section has a length of 5 cm and a width of 30-45 cm.

[0057] In some preferred embodiments, two corners cooperating with vertical partitions are protruded in the horizontal direction at both ends of the upper part of the sand scraper plate. The upper end length of the sand scraper plate is 14-19 cm, the lower end length is 10-15 cm, the total height is 5 cm, the protruding length of the corner is 2 cm, and the height is 2 cm.

[0058] In some preferred embodiments, a magnifying glass is also connected to the lower portion of the sand collection tank, and the magnifying glass is arranged corresponding to the sand identification area.

[0059] In some preferred embodiments, the sand identification region is a linear region.

[0060] In some preferred embodiments, the top opening of the sand collection tank is 15 cm in length, 10-15 cm in width, and 30 cm in depth.

[0061] In some preferred embodiments, the sand collecting groove is a V-shaped groove.

[0062] In some preferred embodiments, the angle of the bottom of the sand collection trough is 30°.

[0063] In some preferred embodiments, the V-shaped groove bottom is assembled from ultra-white glass with a light transmittance greater than 93%.

[0064] In some preferred embodiments, the wind erosion particle starting wind speed testing device further includes a camera bracket for arranging a miniature high-speed camera above a corresponding shooting area.

[0065] In some preferred embodiments, the vertical distance between the micro high-speed camera and the shooting area is 5-10 cm, and the lens of the micro high-speed camera is directed downward to the corresponding shooting area.

[0066] Another aspect of an embodiment of the present invention provides a wind tunnel wind erosion particle starting wind speed test system, including a wind tunnel and the wind tunnel wind erosion particle starting wind speed test device coordinated with the wind tunnel.

[0067] In some preferred embodiments, the wind tunnel wind erosion particle starting wind speed test system also includes a gradient Pitot tube, which is connected to a data logger and a computer; the gradient Pitot tube is arranged on the central axis of the experimental section 1-3m away from the upper wind direction edge of the sand table, and is used to measure the wind speed at multiple heights.

[0068] Another aspect of the embodiments of the present invention further provides a method for testing the starting wind speed of wind erosion particles in a wind tunnel, comprising:

[0069] (1) Providing the wind erosion particle starting wind speed test system;

[0070] (2) A notch is cut in the middle of the bottom plate of the wind tunnel test section, and the wind erosion particle starting wind speed test device is placed in the notch position, and the surface of the upwind extension section is flush with the surface of the bottom plate of the test section;

[0071] (3) laying different types or particle sizes of experimental sand on each sand-laying section, and leveling the sand surface of each sand-laying section with a sand scraper, while ensuring that each sand surface is at the same level as the bottom plate of the experimental section, and then cleaning the sand around the sand tray and at the bottom of the sand collection tank, and placing micro high-speed cameras above each shooting area to aim at the corresponding shooting area for aerial photography;

[0072] (4) A gradient pitot tube is set at the central axis of the experimental section 1-3 m away from the windward edge of the sand table to measure the wind speed at different heights, and the gradient pitot tube is connected to the data acquisition instrument and computer outside the experimental section;

[0073] (5) Experiment: First, start the fan and turn on the micro high-speed camera. The observer holds a strong flashlight next to the sand collection tank and observes the bottom of the tank through a magnifying glass. If experimental sand is found at the bottom of the tank, the exact time and the corresponding test unit number are recorded immediately. During the process of slowly increasing wind speed, the micro high-speed camera also continuously records high-definition images of the shooting area. Continue to increase the wind speed until the start of each test unit is monitored and recorded at the bottom of the sand collection tank, and then turn off the fan.

[0074] (6) Method for determining the starting wind speed and starting friction wind speed: Based on the video playback, determine the exact time when sand particles pass through each shooting area. If the time is earlier than the time recorded by the observer, the time determined by the video shall prevail. If the time recorded by the observer is earlier, the time determined by the observer shall prevail. Then, based on the earlier time data, find the starting wind speed value corresponding to each test unit from the time series wind speed data of the gradient pitot tube at the entrance of the wind tunnel test section, or use the gradient wind speed data of the gradient pitot tube to calculate the starting friction wind speed value by the least squares method.

[0075] In some preferred embodiments, the gradient Pitot tube is capable of measuring wind speeds at heights of 0.4 mm, 0.8 mm, 1.2 mm, 2.4 mm, 4 mm, 8 mm, 12 mm, 16 mm, 20 mm, and 25 mm.

[0076] In some preferred embodiments, the wind speed collection frequency of the gradient pitot tube is 1-100 Hz.

[0077] In some preferred embodiments, the method for calculating the starting friction wind speed value by the least squares method includes:

[0078] 1) Fit the wind speed data at each height into a logarithmic curve:

[0079] U z =a+b ln Z (1)

[0080] Among them, U z is the wind speed at height Z, a and b are fitting coefficients;

[0081] 2) Calculate the starting friction wind speed value according to the friction wind speed calculation formula:

[0082] U * =kb (2)

[0083] Wherein, k is the Karman constant and its value is 0.4.

[0084] The embodiments of the present invention provide a wind erosion particle starting wind speed testing device, testing system and testing method. Since the speed of the sand particles is relatively low at the beginning of starting, and they are basically in a ground-closed moving state, almost all the starting sand particles fall into the V-shaped sand collecting groove and are concentrated in the linear area of ​​the V-shaped groove bottom identification area. The highly transparent ultra-white glass and 10x rectangular magnifying glass allow observers to easily find the sand particles at the bottom of the groove. When a few sand particles are found at the bottom of the groove, the exact time at this moment is recorded as the starting time. According to this starting time, the corresponding starting wind speed value is found in the wind speed data of the time series, or the starting friction wind speed value is calculated according to the wind speed gradient data. Compared with the starting process of the sand particles on the bed surface directly observed by the human eye, this method has the advantages of easy identification and high accuracy, so the experimental results are more objective, which basically solves the defects encountered in various current measurement methods, and provides a scientific and practical new device and method for accurately defining the starting wind speed of sand particles in the wind tunnel.

[0085] The following will describe the technical solutions in the embodiments of the present invention in detail 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, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0086] Example

[0087] See also Figure 1 The present embodiment provides a wind tunnel wind erosion particle starting wind speed test device, including a sandbox 1, which is a rectangular sunken structure with a length of 70 cm, a width of 30-45 cm, and a depth of 4 cm; a plurality of test units separated from each other are arranged on the sandbox 1, each test unit includes a sand-laying section, a contraction section, a shooting channel 8 and a sand collecting trough 2 arranged in sequence along the wind direction, the sand-laying section is used to lay the experimental sand, the widths of the sand-laying section, the contraction section and the shooting channel 8 decrease in sequence, a shooting area 5 corresponding to a micro high-speed camera 4 is arranged in the shooting channel 8, and the sand collecting trough 2 has a V-shaped The bottom of the groove and the V-shaped groove are distributed with a sand identification area 3; among them, the length of the sand-laying section is 70cm and the width is 10-15cm; the width of one end of the contraction section is equal to that of the corresponding sand-laying section, and the width of the other end is equal to that of the corresponding shooting channel 8, and the length is 8cm; the length of the shooting channel 8 is 12cm and the width is 3-5cm; the shooting area 5 is a circular area with a radius of 3-5cm; the specifications of the micro high-speed camera 4 are 4cm×3cm×3cm, equipped with a 20-megapixel high-definition FA industrial lens, the lens diameter is 4cm, the length is 8cm, and a 128Gsd card is used to automatically store images.

[0088] A magnifying glass 11 is also connected to the lower part of the sand collecting trough 2, and the magnifying glass 11 is arranged corresponding to the sand identification area 3; the sand identification area 3 is a linear area; the top opening length of the sand collecting trough 2 is 15 cm, the width is 10-15 cm, and the depth is 30 cm; the sand collecting trough 2 is a V-shaped groove, and the angle of the bottom of the sand collecting trough 2 is 30°, and the V-shaped groove bottom is assembled by ultra-white glass with a transmittance of >93%.

[0089] A plurality of vertical partitions 6 and a sand scraping board 10 are provided on the sand tray 1. The plurality of vertical partitions 6 are arranged at intervals from each other, so as to separate a plurality of test units on the sand tray 1. The height of the vertical partitions 6 is 3 cm. The sand scraping board 10 is used to level the sand surface of the experimental sand laid on the plurality of sand laying sections. The two ends of the sand scraping board 10 are arranged on the vertical partitions 6, and the bottom edge is located at the sand surface position of the experimental sand in the plurality of sand laying sections. Figure 2 As shown, two corners cooperating with the vertical partition 6 are protruded in the horizontal direction at both ends of the upper part of the sand scraper board 10. The upper end length of the sand scraper board 10 is 14-19 cm, the lower end length is 10-15 cm, the total height is 5 cm, the protruding length of the corner is 2 cm, and the height is 2 cm.

[0090] The wind erosion particle starting wind speed test device also includes an upwind extension section 7, the upwind extension section 7 and the sand table 1 are arranged in sequence along the wind direction; a lifting platform 16 connected to the sand table 1 and a camera bracket 9, the camera bracket 9 is used to set the miniature high-speed camera 4 above the corresponding shooting area 5; the length of the upwind extension section 7 is 5 cm and the width is 30-45 cm; the vertical distance between the miniature high-speed camera 4 and the shooting area 5 is 5-10 cm, and the lens of the miniature high-speed camera 4 is aimed downward at the corresponding shooting area 5.

[0091] When in operation, the wind erosion particle starting wind speed test device is arranged in the wind tunnel test section, and the sand surface of the experimental sand in each sand-laying section is on the same horizontal plane as the surface of the bottom plate of the test section, the surface of the upwind extension section 7, and the bottom surface of each vertical partition 6, and the front edge of the wind erosion particle starting wind speed test device is seamlessly connected to the bottom plate of the wind tunnel.

[0092] This embodiment provides a wind erosion particle starting wind speed test system, such as Figure 3 As shown, it includes a wind tunnel and the aforementioned wind tunnel wind erosion particle starting wind speed test device matched with the wind tunnel; it also includes a gradient pitot tube 12, which is connected to a data acquisition instrument 13 and a computer 14; the gradient pitot tube 12 is set at the center axis 15 of the experimental section 1-3m away from the windward edge of the sand table 1, and is used to measure the wind speed at multiple heights.

[0093] The method for testing the starting wind speed of wind erosion particles by using the wind erosion particle starting wind speed testing system of this embodiment includes:

[0094] (1) A notch is cut in the middle of the bottom plate of the wind tunnel test section, and the wind erosion particle starting wind speed test device is placed in the notch position, and the surface of the upwind extension section 7 is flush with the surface of the bottom plate of the test section;

[0095] (2) laying different types or particle sizes of experimental sand on each sand-laying section, and leveling the sand surface of each sand-laying section with a sand scraper 10, while ensuring that each sand surface is at the same level as the bottom plate of the experimental section, and then cleaning the sand around the sand tray 1 and the bottom of the sand collection tank 2, and placing a micro high-speed camera 4 above each shooting area 5 to aim at the corresponding shooting area 5 for overhead shooting;

[0096] (3) A gradient pitot tube 12 is set at the central axis 15 of the experimental section 1-3 m away from the windward edge of the sand table 1, and the wind speed at different heights (heights of 0.4 mm, 0.8 mm, 1.2 mm, 2.4 mm, 4 mm, 8 mm, 12 mm, 16 mm, 20 mm, and 25 mm) is measured. The wind speed collection frequency of the gradient pitot tube 12 is 1-100 Hz. The gradient pitot tube 12 is connected to the data acquisition instrument 13 and the computer 14 outside the experimental section;

[0097] (4) Experiment: First, start the fan and turn on the micro high-speed camera 4. The observer holds a strong flashlight beside the sand collection tank 2 and observes the bottom of the tank through the magnifying glass 11. If the experimental sand is found at the bottom of the tank, the exact time and the corresponding test unit number are recorded immediately. During the process of slowly increasing the wind speed, the micro high-speed camera 4 also continuously records the high-definition image of the shooting area 5. Continue to increase the wind speed until the start of each test unit is monitored and recorded at the bottom of the sand collection tank 2, and then turn off the fan.

[0098] (5) Method for determining the starting wind speed and the starting friction wind speed: According to the video playback, the exact time when the sand particles passed through each shooting area 5 is determined respectively. If the time is earlier than the time recorded by the observer, the time determined by the video shall prevail. If the time recorded by the observer is earlier, the time determined by the observer shall prevail. Then, based on the earlier time data, the starting wind speed value corresponding to each test unit is found from the time series wind speed data of the gradient pitot tube 12 at the entrance of the wind tunnel test section, or the starting friction wind speed value is calculated by the least square method using the gradient wind speed data of the gradient pitot tube 12, as follows:

[0099] 1) Fit the wind speed data at each height into a logarithmic curve:

[0100] U z =a+b ln Z (1)

[0101] Among them, U z is the wind speed at height Z, a and b are fitting coefficients;

[0102] 2) Calculate the starting friction wind speed value according to the friction wind speed calculation formula:

[0103] U * =kb (2)

[0104] Wherein, k is the Karman constant and its value is 0.4.

[0105] The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all aspects and are not intended to limit the present invention, the scope of the present invention is defined only by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0106] The use of headings and sections in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the disclosure.

[0107] Throughout this disclosure, where a composition is described as having, containing, or comprising particular components, or where a process is described as having, containing, or comprising particular process steps, it is contemplated that the compositions taught by the present invention also consist essentially of or consist of the recited components, and that the processes taught by the present invention also consist essentially of or consist of the recited process steps.

[0108] Unless specifically stated otherwise, use of the terms "include," "includes," "including," "have," "has," or "having" should generally be construed as open ended and non-limiting.

[0109] It should be understood that the order of the various steps or the order in which a particular action is performed is not very important, as long as the teachings of the present invention remain operable. In addition, two or more steps or actions may be performed simultaneously.

[0110] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0111] Although the present invention has been described with reference to illustrative embodiments, it will be appreciated by those skilled in the art that various other changes, omissions and / or additions may be made without departing from the spirit and scope of the present invention and that the elements of the embodiments may be replaced by substantial equivalents. In addition, many modifications may be made without departing from the scope of the present invention to adapt specific circumstances or materials to the teachings of the present invention. Therefore, it is not intended herein to limit the present invention to the disclosed specific embodiments for performing the present invention, but it is intended that the present invention will include all embodiments within the scope of the appended claims. In addition, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather uses the terms first, second, etc. to distinguish one element from another.

Claims

1. A method for testing the starting wind speed of wind erosion particles in a wind tunnel, characterized in that: include: (1) Providing a wind erosion particle starting wind speed test system, wherein the wind erosion particle starting wind speed test system for a wind tunnel comprises a wind tunnel and a wind erosion particle starting wind speed test device for a wind tunnel that cooperates with the wind tunnel; The wind tunnel wind erosion particle starting wind speed test device comprises a sand table (1), on which a plurality of test units separated from each other are arranged, each test unit comprising a sand-laying section, a contraction section, a shooting channel (8) and a sand collection trough (2) arranged in sequence along the wind direction, the sand-laying section being used to lay sand for the experiment, the widths of the sand-laying section, the contraction section and the shooting channel (8) decreasing in sequence, a shooting area (5) corresponding to a micro high-speed camera (4) being arranged in the shooting channel (8), the sand collection trough (2) having a V-shaped groove bottom, the V-shaped groove bottom being provided with sand identification areas (3); a magnifying glass (11) is further connected to the lower part of the sand collection trough (2), the magnifying glass (11) being arranged corresponding to the sand identification area (3); The sand tray (1) is provided with a plurality of vertical partitions (6) and a sand scraping board (10); the plurality of vertical partitions (6) are arranged at intervals from each other, thereby separating a plurality of test units on the sand tray (1); the sand scraping board (10) is used to level the surface of the experimental sand laid on the plurality of sand laying sections; The wind erosion particle starting wind speed test device further comprises an upwind extension section (7), wherein the upwind extension section (7) and the sand table (1) are arranged in sequence along the wind direction; The wind tunnel wind erosion particle starting wind speed test system further comprises a gradient pitot tube (12), wherein the gradient pitot tube (12) is connected to a data acquisition instrument (13) and a computer (14); the gradient pitot tube (12) is arranged at a position of a central axis (15) of the experimental section 1-3 m away from the upwind edge of the sand table (1), and is used to measure wind speeds at multiple heights; (2) A notch is cut in the middle of the bottom plate of the wind tunnel test section, and the wind erosion particle starting wind speed test device is placed in the notch position, and the surface of the upwind extension section (7) is flush with the surface of the bottom plate of the test section; (3) laying different types or particle sizes of experimental sand on each sand-laying section, and leveling the sand surface of the experimental sand on each sand-laying section with a sand scraper (10), while ensuring that each sand surface is at the same level as the bottom plate of the experimental section, and then cleaning the sand around the sand tray (1) and at the bottom of the sand collection tank (2), and placing micro high-speed cameras (4) above each shooting area (5) to aim at the corresponding shooting area (5) for aerial photography; (4) a gradient pitot tube (12) is arranged at a position of the central axis (15) of the experimental section 1-3 m away from the upwind edge of the sand table (1) to measure the wind speed at different heights, and the gradient pitot tube (12) is connected to a data acquisition instrument (13) and a computer (14) outside the experimental section; (5) Experiment: First, start the fan and turn on the micro high-speed camera (4). The observer holds a strong flashlight next to the sand collection tank (2) and observes the bottom of the tank through a magnifying glass (11). If experimental sand is found at the bottom of the tank, the exact time and the corresponding test unit number are recorded immediately. During the process of slowly increasing the wind speed, the micro high-speed camera (4) also continuously records the high-definition image of the shooting area (5). Continue to increase the wind speed until the start of each test unit is monitored and recorded at the bottom of the sand collection tank (2), and then turn off the fan. (6) Method for determining the starting wind speed and the starting friction wind speed: Based on the video playback, determine the exact time when sand particles pass through each shooting area (5). If the time is earlier than the time recorded by the observer, the time determined by the video shall prevail. If the time recorded by the observer is earlier, the time determined by the observer shall prevail. Then, based on the earlier time data, find the starting wind speed value corresponding to each test unit from the time series wind speed data of the gradient pitot tube (12) at the entrance of the wind tunnel test section, or use the gradient wind speed data of the gradient pitot tube (12) to calculate the starting friction wind speed value by the least squares method.

2. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The method for calculating the starting friction wind speed value by the least square method comprises: 1) Fit the wind speed data at each height into a logarithmic curve: U z = a + b ln Z （1） in, U z For height Z The wind speed at a and b is the fitting coefficient; 2) Calculate the starting friction wind speed value according to the friction wind speed calculation formula: U * = kb （2） in, k is the Karman constant, and its value is 0.

4.

3. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The gradient Pitot tube (12) is capable of measuring wind speeds at positions with heights of 0.4 mm, 0.8 mm, 1.2 mm, 2.4 mm, 4 mm, 8 mm, 12 mm, 16 mm, 20 mm, and 25 mm.

4. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The wind speed collection frequency of the gradient pitot tube (12) is 1 Hz-100 Hz.

5. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The wind erosion particle starting wind speed testing device further comprises a lifting platform (16) connected to the sandbox (1).

6. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: When in operation, the wind erosion particle starting wind speed test device is arranged in the wind tunnel test section, and the sand surface of the experimental sand in each sand-laying section is on the same horizontal plane as the surface of the test section bottom plate, the surface of the upwind extension section (7), and the bottom surface of each vertical partition (6), and the front edge of the wind erosion particle starting wind speed test device is seamlessly connected to the wind tunnel bottom plate.

7. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: Both ends of the sand scraping plate (10) are arranged on the vertical partition plate (6), and the bottom edge is located at the sand surface position of the experimental sand in the plurality of sand-laying sections.

8. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The sandbox (1) is a rectangular sunken structure with a length of 70 cm, a width of 30-45 cm, and a depth of 4 cm.

9. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The length of the sand-topped section is 70 cm and the width is 10-15 cm.

10. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 9, characterized in that: The width of one end of the contraction section is equal to that of the corresponding sand-laying section, and the width of the other end is equal to that of the corresponding shooting channel (8), and the length is 8 cm.

11. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 10, characterized in that: The shooting channel (8) has a length of 12 cm and a width of 3-5 cm.

12. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The height of the vertical partition (6) is 3 cm.

13. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The shooting area (5) is a circular area with a radius of 3-5 cm.

14. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The upwind extension section (7) has a length of 5 cm and a width of 30-45 cm.

15. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: Two corners cooperating with the vertical partition plate (6) are protruded in the horizontal direction at both ends of the upper part of the sand scraping plate (10); the upper end of the sand scraping plate (10) is 14-19 cm long, the lower end is 10-15 cm long, and the total height is 5 cm; the protruding length of the corners is 2 cm and the height is 2 cm.

16. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The sand particle identification region (3) is a linear region.

17. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The top opening of the sand collecting tank (2) has a length of 15 cm, a width of 10-15 cm and a depth of 30 cm.

18. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The sand collecting groove (2) is a V-shaped groove.

19. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 18, characterized in that: The angle of the bottom of the sand collecting trough (2) is 30°.

20. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The V-shaped groove bottom is formed by assembling ultra-white glass with a light transmittance of more than 93%.

21. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The wind erosion particle starting wind speed testing device also includes a camera bracket (9) for arranging a miniature high-speed camera (4) above a corresponding shooting area (5).

22. The method for testing the starting wind speed of wind erosion particles in a wind tunnel according to claim 1, characterized in that: The vertical distance between the micro high-speed camera (4) and the shooting area (5) is 5-10 cm, and the lens of the micro high-speed camera (4) is directed downwards towards the corresponding shooting area (5).

Images