An experimental device and method for the interaction between internal solitary waves

Abstract

The present invention discloses an experimental device and an experimental method for the interaction between internal solitary waves. The device includes a transparent water tank with a regular shape, a baffle group, a gate system, and a water injection system, wherein: The baffle group is used to design the flow channels of internal solitary waves, and the baffle group is detachably assembled in the transparent water tank; The baffle group includes at least two baffles, and all the baffles are jointly assembled into at least one flow channel independent of the transparent water tank; When there are multiple flow channels, an angle required for the experiment is formed between the flow channels; The water injection system includes a water injection device and buried water injection ports distributed on the bottom surface of the transparent water tank; When constructing the flow channels, multiple water injection ports should be provided in each flow channel; All the water injection ports inside the flow channels are connected to the water injection device through a connecting pipeline; The gate system includes an openable and closable gate that cooperates with the flow channels; The gate is used to isolate the flow channels, thereby realizing wave generation and wave elimination.

Description

Technical Field

[0001] The present invention belongs to the technical field of marine environment and internal wave simulation, and particularly relates to an experimental device and an experimental method for the interaction between internal solitary waves. Background Art

[0002] With the continuous deepening of China's development and utilization of marine resources, complex flow phenomena in the marine environment, especially internal solitary waves, have gradually become important topics in research and engineering applications. An internal solitary wave is a special non-linear wave, whose waveform only contains one wave crest or wave trough, and the energy is highly concentrated, so it is also called a soliton. The formation of internal solitary waves depends on the balance between the dispersion effect and the non-linear effect, which enables them to maintain a stable waveform during propagation and travel a relatively long distance. However, when internal solitary waves interact during propagation, more complex flow phenomena will occur, which have a significant impact on the characteristics of the flow field such as velocity and pressure. Therefore, studying the interaction between internal solitary waves has important theoretical significance and engineering value for understanding their characteristics, the design of marine structures and safe operation.

[0003] Internal solitary waves usually occur at the pycnocline in the ocean interior, and have the characteristics of large scale, long propagation distance, and concentrated energy. Its formation mechanism mainly includes two types: one is that when the tidal current passes through the seabed topography (such as seamounts, ridges or continental shelf edges), the vertical movement of the fluid is restricted by the topography, the energy is concentrated and internal waves are excited, and the internal waves undergo non-linear effects during propagation to form internal solitary waves; the other is that after the pycnocline is externally disturbed, internal solitary waves are excited under the action of gravity. The methods for studying the characteristics of internal solitary waves mainly include theoretical analysis, numerical simulation and model experiments. Among them, model experiments can accurately generate and measure the required internal solitary waves, and conduct systematic research by controlling the experimental environment, which is an indispensable technical means. Although some experimental flume design schemes have been proposed in the prior art, there is a lack of an experimental device that can be used for simulating the interaction between internal solitary waves. Summary of the Invention

[0004] The purpose of the present invention is to provide an experimental device and an experimental method for the interaction between internal solitary waves, so as to overcome the deficiencies of the existing experimental flumes with low modularity and inability to be used for the study of wave-wave coupling processes, and better meet the experimental requirements for studying the interaction process between internal solitary waves.

[0005] To achieve the above task, the present invention adopts the following technical solutions:

[0006] An experimental device for the interaction between internal solitary waves, comprising a transparent flume with a regular shape, a baffle group, a gate system and a water injection system, wherein:

[0007] The baffle group is used for designing the flow channels of internal solitary waves, and the baffle group is detachably assembled in the transparent water tank; the baffle group includes at least two baffles, and all the baffles are jointly assembled into at least one flow channel independent of the transparent water tank; when there are multiple flow channels, an angle required for the experiment is formed between the flow channels.

[0008] The water injection system includes a water injection device and buried water injection ports distributed on the bottom surface of the transparent water tank; when constructing the flow channels, multiple water injection ports should be provided in each flow channel; all the water injection ports inside the flow channels are connected to the water injection device through connecting pipelines.

[0009] The gate system includes an openable and closable gate that cooperates with the flow channel; the gate is used to isolate the flow channel, thereby realizing wave generation and wave elimination.

[0010] Further, two flow channels are constructed by using four baffles; the end of the baffle and the side wall of the transparent water tank, and the bottom of the baffle and the bottom surface of the transparent water tank are sealed by glass glue or the like.

[0011] Further, the water injection ports are distributed in an array on the bottom surface of the transparent water tank; the water injection port includes a circular water inlet cavity and a water injection pipe arranged at the bottom of the water inlet cavity, and limiting bayonets are distributed on the side wall of the water inlet cavity; a water retaining plate with an outer diameter smaller than the inner diameter of the water inlet cavity is arranged in the upper part of the water inlet cavity, and clamping blocks are arranged around the water retaining plate, and the clamping blocks are assembled in the limiting bayonets, so that a plurality of arc-shaped water outlet channels are formed between the outer wall of the water retaining plate and the inner wall of the water inlet cavity.

[0012] Further, when the water injection device is closed, all the water injection ports inside the flow channels are connected through the connecting pipelines to form a communicating vessel structure.

[0013] Further, the gate system includes a bracket arranged outside the transparent water tank, a pulley block and a motor installed on the top of the bracket; the motor is connected to the gate through a flexible wire assembled on the pulley block, and flexible sealing strips are installed on the side and bottom of the gate.

[0014] When generating waves, the gate is driven by the motor to be placed at a specified position in the flow channel to close the gate, and a gravity collapse area is isolated in the flow channel inside the gate; when the motor drives the gate to lift and open the gate, the fluid in the gravity collapse area will be released to the flow channel outside the gate to realize the wave generation process of internal solitary waves.

[0015] When eliminating waves, the incoming internal solitary waves from a distance are isolated outside the gate by closing the gate to realize the wave elimination process.

[0016] An experimental method for the non-zero angle interaction of internal solitary waves in a two-layer fluid, which is based on the experimental device for the interaction between internal solitary waves, includes the following steps:

[0017] Step 10: Determine the angle between the flow channels according to the experimental requirements, and construct two flow channels inside the transparent water tank at the said angle by means of a baffle group, denoted as the first flow channel and the second flow channel;

[0018] Step 20: Select four sets of gate systems and arrange them at both ends of the first flow channel and the second flow channel respectively; among them, the gate systems arranged at the front ends of the first flow channel and the second flow channel are used for wave generation. The gate in the gate system for wave generation forms a gravity collapse area with the nearest side wall of the transparent water tank, and the distance between the two is ; the gate systems arranged at the rear ends of the first flow channel and the second flow channel are used for wave dissipation. The gate in the gate system for wave dissipation forms a wave dissipation area with the nearest side wall of the transparent water tank, and the distance between the two is ; the area between the gravity collapse areas and the wave dissipation areas in the first flow channel and the second flow channel is the experimental section; where represents the characteristic wavelength of the internal solitary wave to be constructed;

[0019] Step 30: Close the gates at the front ends of the first flow channel and the second flow channel, and open the gates at the rear ends of the first flow channel and the second flow channel; use the water injection equipment to inject the upper fluid with a height of and the lower fluid with a height of into the first flow channel and the second flow channel in sequence through the water injection ports;

[0020] Step 40: Turn off the water injection equipment, and add the upper fluid above the gravity collapse areas in the first flow channel and the second flow channel. The lower fluid in the two gravity collapse areas will gradually flow into the experimental section and the wave dissipation areas;

[0021] Step 50: Assume that the length of the second flow channel is greater than that of the first flow channel. The time when the internal solitary wave formed in the gravity collapse area of the second flow channel propagates to the intersection of the first flow channel and the second flow channel is denoted as , and the time when it propagates to the wave dissipation area of the second flow channel is denoted as ; the time when the internal solitary wave formed in the gravity collapse area of the first flow channel propagates to the intersection of the first flow channel and the second flow channel is denoted as , and the time when it propagates to the wave dissipation area of the first flow channel is denoted as ; then:

[0022] Open the gate at the front end of the second flow channel at the zero moment, so that the internal solitary wave is formed in the gravity collapse area of the second flow channel and propagates along the second flow channel; open the gate at the front end of the first flow channel at moment, so that the internal solitary wave is formed in the gravity collapse area of the first flow channel and propagates along the first flow channel;

[0023] Step 60, At moment, the internal solitary waves in the first flow channel and the second flow channel interact at the intersection of the first flow channel and the second flow channel;

[0024] Step 70, at the moment, the internal solitary wave in the first flow channel propagates to the wave dissipation area. At this time, the gate at the rear end of the first flow channel is controlled to close, isolating the internal solitary wave in the wave dissipation area; at the moment, the internal solitary wave in the second flow channel propagates to the wave dissipation area. At this time, the gate at the rear end of the second flow channel is controlled to close.

[0025] Furthermore, the characteristic wavelength of the internal solitary wave is determined by the following formula:

[0026] ;

[0027] wherein, is the target wave amplitude of the internal solitary wave, and represent the thickness and density of the upper fluid injected into the gravity collapse area, and represent the thickness and density of the lower fluid injected into the gravity collapse area.

[0028] Furthermore, when the internal solitary wave to be constructed is a concave internal solitary wave, it is necessary to ensure that the density and thickness of the upper fluid are both less than those of the lower fluid.

[0029] Furthermore, is calculated as follows:

[0030] , ; is the wave speed of the internal solitary wave, is the distance from the gravity collapse area of the second flow channel to the intersection of the first and second flow channels, is the acceleration due to gravity.

[0031] An experimental method for head-on collision of a mono-modal solitary wave and a bi-modal internal solitary wave, which is based on the experimental device for interaction between internal solitary waves and includes the following steps:

[0032] Step 11, construct a straight flow channel inside the transparent water tank through the baffle group and the side wall of the transparent water tank;

[0033] Step 21, set a set of gate systems at the front end and the rear end of the flow channel respectively, so as to form a gravity collapse area at the front end and the rear end of the flow channel respectively. The experimental section is between the two gravity collapse areas; the gravity collapse area at the front end is used to form a mono-modal internal solitary wave, and the gravity collapse area at the rear end is used to form a bi-modal internal solitary wave; the distance between the gate and the front side wall of the transparent water tank in the gate system at the front end is and the distance between the gate and the rear side wall of the water tank in the gate system at the rear end is ; Denote the characteristic wavelength of an internal solitary wave within one mode;

[0034] Step 31: Close the gates at the front end and the back end of the flow channel, and use the water injection device to inject into the flow channel successively through the water injection port the upper fluid of a certain height and the middle fluid of a certain height; then extract part of the upper fluid from above the gravity collapse area at the back end, and the middle fluid in the experimental section will flow towards the gravity collapse area at the back end;

[0035] Step 41: Use the water injection device again to inject into the flow channel through the water injection port the lower fluid of a certain height, and then add half of the extracted upper fluid from above the gravity collapse area at the back end; the lower fluid in the gravity collapse area at the back end will partially flow into the experimental section, thereby forming a gravity potential well required for constructing a two - mode internal solitary wave in the gravity collapse area at the back end;

[0036] Step 51: Add the upper fluid from above the gravity collapse area at the front end; the lower fluid in the gravity collapse area at the front end will partially flow into the experimental section, thereby forming a gravity potential well required for constructing a one - mode internal solitary wave in the gravity collapse area at the front end;

[0037] Step 61: Denote the time when the two - mode internal solitary wave propagates to the middle of the experimental section as , and the time when it propagates to the gravity collapse area at the front end as ; denote the time when the one - mode internal solitary wave propagates to the middle of the experimental section as , and the time when it propagates to the gravity collapse area at the back end as ; then:

[0038] At the zero moment, first open the gate at the back end to form a two - mode internal solitary wave propagating towards the front end of the flow channel; then at moment, open the gate at the front end to form a one - mode internal solitary wave propagating towards the back end of the flow channel; the one - mode internal solitary wave and the two - mode internal solitary wave interact in the experimental section;

[0039] Step 71: Manually move the gate at the back end towards the front end so that the distance between the moved gate and the rear side wall of the transparent water tank increases to ; then at moment, the one - mode internal solitary wave first propagates to the gravity collapse area at the back end, and at this time, close the gate at the back end; finally at moment, the two - mode internal solitary wave propagates to the gravity collapse area at the front end, and after closing the gate at the front end, the experiment ends.

[0040] Furthermore, the calculation formula for the characteristic wavelength of the one - mode internal solitary wave is:

[0041] ;

[0042] In the above formula, is the target wave amplitude of an internal solitary wave in a mode, and represent the thickness and density of the upper fluid injected in the experimental section, and represent the thickness and density of the middle fluid injected in the experimental section, and represent the thickness and density of the lower fluid injected in the experimental section; .

[0043] Compared with the prior art, the present invention has the following technical features:

[0044] 1. In the present invention, the baffle group can be directly placed inside the transparent water tank and fixed by the pressure generated by the water flow and glass glue, etc., which is convenient for quick replacement and maintenance; users can flexibly configure or replace the baffles according to experimental needs to form different types of flow channels, thereby significantly improving the flexibility and efficiency of the experiment.

[0045] 2. A plurality of buried water injection ports are provided at the bottom of the transparent water tank, which can be quickly enabled or disabled; this design can ensure that there are water injection ports inside the flow channel under different flow channel settings, and the disturbance of the fluid in the tank during the water injection process is small.

[0046] 3. The gate system is placed on the ground and is independent of the transparent water tank and can be used on either side of the flow channel. By automatically opening and closing the gate, the rapid conversion of the wave generation and wave elimination functions can be achieved.

[0047] 4. The device of the present invention has the advantages of simple operation, wide applicability, strong expandability, easy replacement of modules, etc.; this device can not only generate typical internal solitary waves, but also be used for experimental studies of complex flow processes such as wave-fluid coupling and wave-wave coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a schematic diagram of the overall structure of the experimental device of the present invention;

[0049] Figure 2 is a schematic diagram of the structure of the water injection port in the water injection system;

[0050] Figure 3 is a top view schematic diagram of the transparent water tank, and four different types of flow channel structures are shown on the right side;

[0051] Figure 4 is a schematic diagram of the structure of the gate system;

[0052] Figure 5 is a schematic diagram of the flow channel structure adopted by the experimental method for the non-zero angle interaction of internal solitary waves in two-layer fluids;

[0053] Figure 6 (a)-(f) in the figure are schematic diagrams of the fluid changes in different stages in the experimental method of non-zero angle interaction of internal solitary waves in two-layer fluids;

[0054] Figure 7 are the fluid interfaces before, during, and after the interaction of internal solitary waves in the experimental method of non-zero angle interaction of internal solitary waves in two-layer fluids;

[0055] Figure 8 (a)-(f) in the figure are schematic diagrams of different stages of the formation of the gravity collapse areas at the front and rear ends of the flow channel in the experimental method of head-on collision of a single-mode solitary wave and a two-mode internal solitary wave;

[0056] Figure 9 (a)-(f) in the figure are schematic diagrams of different stages of the interaction between a single-mode internal solitary wave and a two-mode internal solitary wave in the experimental method of head-on collision of a single-mode solitary wave and a two-mode internal solitary wave.

[0057] Explanation of the labels in the figure: 1 transparent water tank, 2 baffle group, 21 baffle, 3 gate system, 31 support, 32 pulley block, 33 flexible wire, 34 gate, 35 motor, 4 water injection system, 41 water injection port, 42 water injection pipe, 43 water inlet cavity, 44 water retaining plate, 45 limit bayonet, 46 water outlet channel, 5 flow channel, 51 first flow channel, 52 second flow channel. Detailed implementation mode

[0058] The present invention first provides an experimental device for the interaction between internal solitary waves, including a regularly shaped transparent water tank 1, a baffle group 2, a gate system 3, and a water injection system 4, wherein:

[0059] The baffle group 2 is used to design the flow channel 5 of the internal solitary wave, and the baffle group 2 is detachably assembled in the transparent water tank 1; the baffle group 2 includes at least two baffles 21, and all the baffles 21 are jointly assembled into at least one flow channel 5 independent of the transparent water tank 1; when there are multiple flow channels 5, an included angle required for the experiment is formed between the flow channels 5;

[0060] The water injection system 4 includes a water injection device and buried water injection ports 41 distributed on the bottom surface of the transparent water tank 1; when constructing the flow channel 5, multiple water injection ports 41 should exist in each flow channel 5; all the water injection ports 41 inside the flow channel 5 are connected to the water injection device through a communication pipeline;

[0061] The gate system 3 includes an openable and closable gate 34 matched with the flow channel 5; the gate 34 is used to isolate the flow channel 5, so as to realize wave generation and wave elimination.

[0062] The following further explains the specific design of the experimental device of the present invention.

[0063] I. Transparent water tank 1.

[0064] See the appendix Figure 1 In the present invention, the transparent water tank 1 has a regular shape, for example, it can be a rectangular transparent water tank 1 or a circular transparent water tank 1. Figure 1 The structure of the rectangular transparent water tank 1 is shown in the example of . The transparent structure is adopted to facilitate the observation of the inside of the flow channel 5 during the experiment.

[0065] II. Baffle group 2.

[0066] The baffle group 2 is used to design the flow channel 5 and includes at least two baffles 21; see the appendix Figure 3 , Figure 3 Several different forms of the flow channel 5 are shown on the right side of . When two baffles 21 are used, a straight flow channel 5 can be constructed in combination with the side wall of the transparent water tank 1; when four baffles 21 are used, two flow channels 5 with an included angle required for the experiment can be formed through the combination of the baffles 21; the design of the included angle is determined according to actual needs, so that the two flow channels 5 can be in a cross shape, a fork shape, etc.

[0067] Taking the construction of two fork-shaped flow channels 5 with a certain included angle as an example in this solution, see Figure 3 . Four baffles 21 are arranged in the transparent water tank 1. The end of the baffle 21 is sealed with the side wall of the transparent water tank 1 and the bottom of the baffle 21 is sealed with the bottom surface of the transparent water tank 1 through glass glue or the like, so that the constructed flow channel 5 is independent of the transparent water tank 1 and the two are not connected; by replacing the baffles 21 with different shapes, the construction of different types of flow channels 5 can be realized.

[0068] III. Gate system 3.

[0069] See Figure 1 . In this solution, the gate system 3 includes a bracket 31 arranged outside the transparent water tank 1, a pulley group 32 and a motor 35 installed on the top of the bracket 31; the motor 35 is connected to the gate 34 through a flexible wire 33 assembled on the pulley group 32, and flexible sealing strips are installed on the side and bottom of the gate 34.

[0070] The gate system 3 is used for wave dissipation and wave generation:

[0071] When generating waves, the gate 34 is driven by the motor 35 to be lowered into the designated position in the flow channel 5 to close the gate 34, and the flexible sealing strip ensures the seal between the gate 34 and the bottom surface of the transparent water tank 1 of the flow channel 5, so that a gravity collapse area (gravity potential well) can be isolated in the flow channel 5 inside the gate 34; when the motor 35 drives the gate 34 to be lifted to open the gate 34, the fluid in the gravity collapse area will be released to the flow channel 5 outside the gate 34 to realize the wave generation process of internal solitary waves.

[0072] When wave dissipation is carried out, the internal solitary waves coming from afar can be isolated outside the gate 34 by closing the gate 34, so that it does not contaminate the inner area of the gate 34 to achieve the wave dissipation process.

[0073] The isolation position of the gate 34 in the flow channel 5 is adjusted by changing the position of the bracket 31; the number of the gate systems 3 is set according to the experimental requirements.

[0074] IV. Water injection system 4.

[0075] The water injection system 4 is used to inject water into the flow channel 5 to meet the experimental requirements; in this solution, the water injection system 4 includes a water injection device, a water injection port 41 and a connecting pipeline; among them, the water injection device can adopt a water pump, for example, and is connected to all the water injection ports 41 located inside the flow channel 5 through the connecting pipeline.

[0076] As Figure 1 and Figure 3 shown, in this solution, the water injection ports 41 are arranged in an array on the bottom surface of the transparent water tank 1 and adopt an embedded design; as Figure 2 shown; the water injection port 41 includes a circular water inlet cavity 43 and a water injection pipe 42 arranged at the bottom of the water inlet cavity 43, and limiting bayonets 45 are distributed on the side wall of the water inlet cavity 43; a water retaining disc 44 with an outer diameter smaller than the inner diameter of the water inlet cavity 43 is arranged in the upper part of the water inlet cavity 43, and clamping blocks are arranged around the water retaining disc 44, and the clamping blocks are assembled in the limiting bayonets 45, so that a plurality of arc-shaped water outlet channels 46 are formed between the outer wall of the water retaining disc 44 and the inner wall of the water inlet cavity 43.

[0077] The water injection device provides fluid to the water injection port 41 through the connecting pipeline. After the fluid enters the water inlet cavity 43 through the water injection pipe 42, the upward impact force is offset by the blockage of the water retaining disc 44. At this time, the fluid will diffuse around the water retaining disc 44 and gradually overflow into the inside of the flow channel 5 from the water outlet channels 46.

[0078] When the water injection device is closed, all the water injection ports 41 inside the flow channel 5 are still connected through the connecting pipeline to form a communicating vessel structure.

[0079] In this solution, such a structural design of the water injection port 41 can make the fluid injection process have little disturbance to the existing fluid in the flow channel 5 and reduce the influence on the fluid.

[0080] It should be noted that in order to ensure smooth water injection in the flow channel 5, when constructing the flow channel 5, there should be multiple water injection ports 41 in each flow channel 5.

[0081] On the basis of the above technical solutions, the present invention provides an experimental method for non-zero angle interaction of internal solitary waves in two-layer fluids, including the following steps:

[0082] Step 10: Determine the angle between the flow channels 5 according to the experimental requirements, and construct two flow channels 5 inside the transparent water tank 1 at the said angle by means of the baffle group 2, denoted as the first flow channel 51 and the second flow channel 52; wherein, the first flow channel 51 is parallel to the side wall of the transparent water tank 1, see Figure 5 .

[0083] Step 20: Select four sets of gate systems 3 and arrange them at both ends of the first flow channel 51 and the second flow channel 52 respectively; wherein, the gate systems 3 arranged at the front end of the first flow channel 51 and the front end of the second flow channel 52 are used for wave generation, and a gravity collapse area is formed between the gate 34 in the gate system 3 for wave generation and the nearest side wall of the transparent water tank 1, and the distance between the two (the gate 34 and the side wall of the transparent water tank 1) is ; the gate systems 3 arranged at the rear end of the first flow channel 51 and the rear end of the second flow channel 52 are used for wave dissipation, and a wave dissipation area is formed between the gate 34 in the gate system 3 for wave dissipation and the nearest side wall of the transparent water tank 1, and the distance between the two (the gate 34 and the side wall of the transparent water tank 1) is ; the area between the gravity collapse area and the wave dissipation area in the first flow channel 51 and the second flow channel 52 is the experimental section.

[0084] Wherein represents the characteristic wavelength of the internal solitary wave to be constructed, and is determined by the following formula:

[0085] ;

[0086] Wherein, is the target wave amplitude of the internal solitary wave, and represent the thickness and density of the upper fluid injected into the gravity collapse area, and represent the thickness and density of the lower fluid injected into the gravity collapse area; wherein when the internal solitary wave to be constructed is a concave internal solitary wave, it is necessary to ensure that the density and thickness of the upper fluid are both less than those of the lower fluid. In this embodiment, takes 0.05 m, takes 1000 kg / m 3 , takes 0.25 m, takes 1020 kg / m 3 .

[0087] The gravity collapse areas of the first flow channel 51 and the second flow channel 52 do not affect each other, so the generated internal solitary waves are independent of each other in the initial stage and only interact at the intersection of the flow channels 5.

[0088] Step 30, close the gates 34 at the front ends of the first flow channel 51 and the second flow channel 52, and open the gates 34 at the rear ends of the first flow channel 51 and the second flow channel 52; use the water injection device to sequentially inject into the first flow channel 51 and the second flow channel 52 through the water injection port 41 upper-layer fluid of a certain height and Figure 6 lower-layer fluid of a certain height, see the light blue and dark blue areas in (a) of

[0089] Step 40, turn off the water injection device. At this time, the water injection ports 41 in the first flow channel 51 and the second flow channel 52 are connected through the connecting pipeline; add upper-layer fluid above the gravity collapse areas of the first flow channel 51 and the second flow channel 52. Then, due to the connection between the water injection ports 41, the lower-layer fluid in the two gravity collapse areas will gradually flow into the experimental section and the wave dissipation area, as shown in Figure 6 (b) of

[0090] In this step, the gravity collapse method is adopted to construct a fluid density stratification different from other areas in the gravity collapse area and release it to form an internal solitary wave.

[0091] Step 50, record that the length of the second flow channel 52 is greater than that of the first flow channel 51. Denote the time when the internal solitary wave formed in the gravity collapse area of the second flow channel 52 propagates to the intersection of the first flow channel 51 and the second flow channel 52 as , and the time when it propagates to the wave dissipation area of the second flow channel 52 as ; Denote the time when the internal solitary wave formed in the gravity collapse area of the first flow channel 51 propagates to the intersection of the first flow channel 51 and the second flow channel 52 as , and the time when it propagates to the wave dissipation area of the first flow channel 51 as ; Then:

[0092] Open the gate 34 at the front end of the second flow channel 52 at the zero moment, so that an internal solitary wave is formed in the gravity collapse area of the second flow channel 52 and propagates along the second flow channel 52; Open the gate 34 at the front end of the first flow channel 51 at the moment, so that an internal solitary wave is formed in the gravity collapse area of the first flow channel 51 and propagates along the first flow channel 51, as shown in Figure 6 (c) of

[0093] Among them, The calculation method of is: ; is the wave speed of the internal solitary wave, is the distance from the gravity collapse area of the second flow channel 52 to the intersection of the first flow channel 51 and the second flow channel 52, is the acceleration due to gravity.

[0094] The rest , and has the same calculation method, and only needs to replace in with the corresponding distance.

[0095] Step 60, At the moment, the internal solitary waves in the first flow channel 51 and the second flow channel 52 interact at the intersection of the first flow channel 51 and the second flow channel 52, as shown in Figure 6 (d) of; in this experiment, both internal solitary waves are manifested as an increase in wave amplitude.

[0096] Step 70, after the internal solitary waves in the first flow channel 51 and the second flow channel 52 interact, they will continue to propagate along the experimental sections of the first flow channel 51 and the second flow channel 52, as shown in Figure 6 (e) of; at At the moment, the internal solitary wave in the first flow channel 51 propagates to the wave dissipation area. At this time, the gate 34 at the rear end of the first flow channel 51 is closed to isolate the internal solitary wave in the wave dissipation area and prevent it from propagating back and polluting the experimental section, as shown in Figure 6 (f) of; similarly, at At the moment, the internal solitary wave in the second flow channel 52 propagates to the wave dissipation area. At this time, the gate 34 at the rear end of the second flow channel 52 is closed.

[0097] During the above experimental process, the generation and elimination methods of the internal solitary waves in the first flow channel 51 and the second flow channel 52 are the same. However, due to the differences in wave amplitude and wave speed, there are slight differences in the parameters of the gravity collapse area and the movement time of the gate 34. The above experiment can be combined with methods such as fluid dyeing and PIV for flow field observation, or structures can be placed at the intersection of the first flow channel 51 and the second flow channel 52 for further research on the interaction of internal solitary waves.

[0098] Based on the above technical solutions, the present invention also provides an experimental method for the head-on impact of a first-mode solitary wave and a second-mode internal solitary wave in a three-layer fluid. In this method, it is necessary to construct upper, middle, and lower three-layer fluids, and only one flow channel 5 is required. The specific steps are as follows:

[0099] Step 11, construct a linear flow channel 5 inside the transparent water tank 1 through the baffle group 2 and the side wall of the transparent water tank 1, as shown in the right side of Figure 3 .

[0100] Step 21, set a set of gate systems 3 at the front end and the rear end of the flow channel 5 respectively, so as to form a gravity collapse area at the front end and the rear end of the flow channel 5 respectively. The experimental section is between the two gravity collapse areas; the gravity collapse area at the front end is used to form a first-mode internal solitary wave, and the gravity collapse area at the rear end is used to form a second-mode internal solitary wave; the distance between the gate 34 in the front-end gate system 3 and the front side wall of the transparent water tank 1 is , the distance between the gate 34 in the gate system 3 at the back end and the side wall of the water trough is , because in the case of a uniform density distribution, the width of the gravitational collapse zone required for the two-mode internal solitary wave is relatively narrow.

[0101] Among them, represents the characteristic wavelength of the first-mode internal solitary wave, and the calculation formula is as follows:

[0102] ;

[0103] In the above formula, is the target wave amplitude of the first-mode internal solitary wave, and represent the thickness and density of the upper fluid injected into the experimental section, and represent the thickness and density of the middle fluid injected into the experimental section, and represent the thickness and density of the lower fluid injected into the experimental section; generally, .

[0104] In this embodiment, takes 0.05 m, takes 1000 kg / m 3 ; takes 0.05 m, takes 1010 kg / m 3 ; takes 0.25 m, takes 1020 kg / m 3 .

[0105] Step 31, close the gates 34 at the front end and the back end of the flow channel 5, and use the water injection device to inject the upper fluid with a height of and the middle fluid with a height of into the flow channel 5 in sequence through the water injection port 41, as shown in (a) and (b) of Figure 8 ; then pump out part of the upper fluid from above the gravitational collapse zone at the back end. According to the principle of communicating vessels, the middle fluid in the experimental section will flow to the gravitational collapse zone at the back end, as shown in (c) of Figure 8 .

[0106] Step 41, use the water injection device again to inject the lower fluid with a height of into the flow channel 5 through the water injection port 41, as shown in (d) of Figure 8 ; then add about half of the pumped-out upper fluid from above the gravitational collapse zone at the back end; during this process, part of the lower fluid in the gravitational collapse zone at the back end will flow into the experimental section, so as to form a gravitational potential well required for constructing the two-mode internal solitary wave in the gravitational collapse zone at the back end, asFigure 8 as shown in (e).

[0107] Step 51: Add upper fluid from above the gravity collapse area at the front end; during this process, part of the lower fluid in the gravity collapse area at the front end will flow into the experimental section, thereby forming a gravity potential well required for constructing a first-mode internal solitary wave in the gravity collapse area at the front end, as Figure 8 shown in (f).

[0108] Step 61: Denote the time when the second-mode internal solitary wave propagates to the middle of the experimental section as , and the time when it propagates to the gravity collapse area at the front end as ; denote the time when the first-mode internal solitary wave propagates to the middle of the experimental section as , and the time when it propagates to the gravity collapse area at the rear end as ; where , , and can be calculated through the distance and the wave speeds of the first-mode internal solitary wave and the second-mode internal solitary wave; then:[[]]

[0109] Since the wave speed of the second-mode internal solitary wave is much smaller than that of the first-mode internal solitary wave, at the zero moment, first open the gate 34 at the rear end to form a second-mode internal solitary wave propagating towards the front end of the flow channel 5, as Figure 9 shown in (a); then at open the gate 34 at the front end to form a first-mode internal solitary wave propagating towards the rear end of the flow channel 5, as Figure 9 shown in (b); the first-mode internal solitary wave and the second-mode internal solitary wave interact in the experimental section, which in this experiment is manifested as an increase in the wave amplitude of the lower wave surface and a decrease in the wave amplitude of the upper wave surface, as Figure 9 shown in (c) and (d).

[0110] Step 71: Manually move the gate 34 at the rear end forward so that the distance between the moved gate 34 and the rear side wall of the transparent water tank 1 increases to ; then at the first-mode internal solitary wave first propagates to the gravity collapse area at the rear end, and at this time, close the gate 34 at the rear end to prevent the first-mode internal solitary wave from being reflected and contaminating the experimental section, as Figure 9 shown in (e); finally, at the second-mode internal solitary wave propagates to the gravity collapse area at the front end, and after closing the gate 34 at the front end, the experiment ends, as Figure 9 shown in (f).

[0111] The above experiment can be combined with methods such as fluid staining and PIV for flow field observation, or structures can be placed in the experimental section of the flow channel 5 for further research.[[]]

[0112] In the above two experiments, the propagation directions of the concave-down type, convex-up type, first-mode internal solitary waves, second-mode internal solitary waves, and internal solitary waves can be adjusted according to experimental requirements; terrain models, structures, submersibles and other equipment can also be installed in the experimental section to meet different experimental needs. This device is mainly used for the generation and elimination of internal solitary waves, and there are no restrictions on the observation of experimental phenomena and post-processing operations. In addition, this device can be combined with equipment or technologies such as particle image velocimetry (PIV), multi-view positioning, and three-component balance to further expand the research scope.

[0113] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. An experimental method for non-zero angle interaction of internal solitary waves in two layers of fluid, characterized in that: The method is based on an internal solitary wave interaction experimental device, which comprises a transparent water tank (1) with a regular shape, a baffle group (2), a gate system (3) and a water injection system (4), wherein: The baffle group (2) is used to design a flow channel (5) of an internal solitary wave, and the baffle group (2) is detachably assembled in a transparent water tank (1); the baffle group (2) includes at least two baffles (21), and all the baffles (21) are assembled together to form at least one flow channel (5) that is independent of the transparent water tank (1); when there are multiple flow channels (5), angles required for the experiment are formed between the flow channels (5); The water injection system (4) comprises a water injection device and embedded water injection ports (41) distributed on the bottom surface of the transparent water tank (1); when constructing the flow channel (5), a plurality of water injection ports (41) should be provided in each flow channel (5); all water injection ports (41) inside the flow channel (5) are connected to the water injection device via a connecting pipe; The gate system (3) comprises an openable and closable gate (34) cooperating with the flow channel (5); the gate (34) is used to isolate the flow channel (5), thereby achieving wave generation and wave elimination; The method comprises the following steps: Step 10, determining the angle between the flow channels (5) according to experimental requirements, and constructing two flow channels (5) at the angle inside the transparent water tank (1) through the baffle group (2), which are recorded as the first flow channel (51) and the second flow channel (52); Step 20, four gate systems (3) are selected and arranged at both ends of the first flow channel (51) and the second flow channel (52), respectively; wherein the gate systems (3) arranged at the front end of the first flow channel (51) and the front end of the second flow channel (52) are used for wave generation, and a gravity collapse zone is formed between the gate (34) in the gate system (3) used for wave generation and the side wall of the transparent water tank (1) closest to the gate system (3), and the distance between the two is The gate system (3) arranged at the rear end of the first flow channel (51) and the rear end of the second flow channel (52) is used for wave elimination, and a wave elimination zone is formed between the gate (34) in the gate system (3) for wave elimination and the side wall of the transparent water tank (1) closest to the gate system (3), and the distance between the two is ; The area between the gravity collapse zone and the wave-breaking zone in the first flow channel (51) and the second flow channel (52) is the experimental section; wherein represents the characteristic wavelength of the internal solitary wave to be constructed; Step 30, closing the gates (34) at the front end of the first flow channel (51) and the front end of the second flow channel (52), opening the gates (34) at the rear end of the first flow channel (51) and the rear end of the second flow channel (52); using a water injection device to inject water into the first flow channel (51) and the second flow channel (52) in sequence through the water injection port (41); The height of the upper fluid and Highly subsurface fluid; Step 40, closing the water injection device, adding the upper layer fluid into the gravity collapse area of ​​the first flow channel (51) and the second flow channel (52), and the lower layer fluid of the two gravity collapse areas will gradually flow into the experimental section and the wave-breaking area; Step 50, record that the length of the second flow channel (52) is greater than that of the first flow channel (51), and the time for the internal solitary wave formed in the gravity collapse zone of the second flow channel (52) to propagate to the intersection of the first flow channel (51) and the second flow channel (52) is recorded as The time it takes to propagate to the wave-breaking zone of the second flow channel (52) is recorded as The time for the internal solitary wave formed in the gravity collapse zone of the first flow channel (51) to propagate to the intersection of the first flow channel (51) and the second flow channel (52) is recorded as The time it takes to propagate to the wave-breaking zone of the first flow channel (51) is recorded as ;but: At time zero, the gate (34) at the front end of the second flow channel (52) is opened, so that the gravity collapse area of ​​the second flow channel (52) forms an internal solitary wave and propagates along the second flow channel (52); The gate (34) at the front end of the first flow channel (51) is always opened, so that the gravity collapse area of ​​the first flow channel (51) forms an internal solitary wave and propagates along the first flow channel (51); Step 60, At time t, the internal solitary waves in the first flow channel (51) and the second flow channel (52) interact with each other at the intersection of the first flow channel (51) and the second flow channel (52); Step 70, At time , the internal solitary wave in the first flow channel (51) propagates to the wave-breaking zone, and at this time, the gate (34) at the rear end of the first flow channel (51) is controlled to close, isolating the internal solitary wave to the wave-breaking zone; At time t, the internal solitary wave in the second flow channel (52) propagates to the wave-breaking zone, and at this time, the gate (34) at the rear end of the second flow channel (52) is controlled to close.

2. The experimental method for non-zero angle interaction of internal solitary waves in two-layer fluids according to claim 1, characterized in that: Characteristic wavelength of internal solitary waves Determined by the following formula: ； in, is the target amplitude of the inner solitary wave, and represents the thickness and density of the upper fluid injected into the gravity collapse zone, and Represents the thickness and density of the underlying fluid injected into the gravity collapse zone.

3. The experimental method for non-zero angle interaction of internal solitary waves in two-layer fluids according to claim 1, characterized in that: When the internal solitary wave to be constructed is a concave internal solitary wave, it is necessary to ensure that the density and thickness of the upper fluid are smaller than the density and thickness of the lower fluid.

4. The experimental method for non-zero angle interaction of internal solitary waves in two-layer fluids according to claim 2, characterized in that: The calculation method is: , ; is the velocity of the internal solitary wave, is the distance from the gravity collapse area of ​​the second flow channel (52) to the intersection of the first flow channel (51) and the second flow channel (52), is the acceleration due to gravity.

5. The experimental method for non-zero angle interaction of internal solitary waves in two-layer fluids according to claim 1, characterized in that: The water injection ports (41) are distributed in an array on the bottom surface of the transparent water tank (1); the water injection ports (41) include a circular water inlet cavity (43) and a water injection pipe (42) arranged at the bottom of the water inlet cavity (43); a limiting clamping opening (45) is distributed on the side wall of the water inlet cavity (43); a water retaining plate (44) having an outer diameter smaller than an inner diameter of the water inlet cavity (43) is arranged at the upper part of the water inlet cavity (43); clamping blocks are arranged around the water retaining plate (44), and the clamping blocks are assembled in the limiting clamping opening (45), so that a plurality of arc-shaped water outlets (46) are formed between the outer wall of the water retaining plate (44) and the inner wall of the water inlet cavity (43).

6. The experimental method for non-zero angle interaction of internal solitary waves in two-layer fluids according to claim 1, characterized in that: When the water injection device is closed, all water injection ports (41) inside the flow channel (5) are connected via the connecting pipeline to form a communicating vessel structure.

7. The experimental method for non-zero angle interaction of internal solitary waves in two-layer fluids according to claim 1, characterized in that: The gate system (3) comprises a bracket (31) arranged outside the transparent water tank (1), a pulley block (32) installed on the top of the bracket (31), and a motor (35); the motor (35) is connected to the gate (34) through a flexible line (33) mounted on the pulley block (32), and the side and bottom of the gate (34) are equipped with flexible sealing strips; When generating waves, the gate (34) is placed in a designated position in the flow channel (5) by driving the motor (35) to close the gate (34), thereby isolating a gravity collapse zone in the flow channel (5) inside the gate (34); when the motor (35) drives the gate (34) upward to open the gate (34), the fluid in the gravity collapse zone is released to the flow channel (5) outside the gate (34), thereby realizing the wave generation process of the internal solitary wave; When wave absorbing is performed, the gate (34) is closed to isolate the inner solitary wave coming from a distance to the outside of the gate (34), thereby achieving the wave absorbing process.

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