Method and system for adjusting interface difference of bulk water in internal wave generation experiment using gravity collapse method

Abstract

The present invention belongs to the technical field of internal wave tank experiments, and discloses a method and system for adjusting the interface difference of bulk water in an internal wave experiment generated by a gravity collapse method. The method configures two layers of fluids with different densities in an experimental tank, and divides the experimental tank into a wave-making area and a working area by a baffle; by changing the way of adding or removing bulk water in the wave-making area, and combining the state of inserting the baffle into the lower salt water layer, a height difference is formed in the interface of the stratified fluids on both sides of the baffle, so that the interface of the stratified fluids in the wave-making area is lower than the interface of the stratified fluids in the working area, or the interface of the stratified fluids in the wave-making area is higher than the interface of the stratified fluids in the working area; when the baffle is pulled out, the fluid at the junction of the wave-making area and the working area of ​​the experimental tank generates internal waves due to the gravity collapse mechanism, and propagates into the working area. The present invention replaces the water injection / pumping process in the traditional method with the addition / subtraction of bulk water, which can accelerate the process of forming the interface difference, reduce the disturbance to the two layers of fluids, and the volume of the fluid in the tank remains unchanged before and after the experiment.

Description

Technical Field

[0001] The invention belongs to the technical field of internal wave water tank experiments, and in particular relates to a method and system for adjusting interface differences of block water in an internal wave experiment generated by a gravity collapse method. Background Art

[0002] The gravity collapse method is a commonly used wave-making method in internal wave tank experiments. A baffle is used to separate the tank containing stratified fluid into two parts, the left and right parts, and the bottom layer is kept connected, so that the two parts form a communicating vessel. After adding fresh water to the wave-making area (the area between the baffle and its closer side wall), the pressure on both sides of the baffle must be balanced, and the salt water at the bottom of the wave-making area will be squeezed into the working area, thereby forming a height difference between the interface depths of the two layers of fluid on the left and right sides of the baffle. Since the density of fresh water is relatively small, there is also a certain height difference between the free surfaces of the fluid on both sides of the baffle, but this height difference is small and almost invisible, while the height difference of the interface on both sides of the baffle is large, which is an important factor affecting the amplitude of the internal wave. Therefore, when using the gravity collapse method to make internal waves, the interface difference between the two layers of fluid on the left and right sides of the baffle is usually used as the control variable.

[0003] The operation of traditional gravity collapse wave generation can be roughly divided into three steps: (1) After the stratified fluid has been fully static, slowly insert the baffle vertically into the fluid so that the lower edge of the baffle enters the salt water and leaves a certain gap with the bottom of the water tank (the depth of the baffle inserted into the salt water should be greater than the interface difference in the gravity collapse method), forming a communicating vessel. (2) Slowly inject fresh water into the wave-making area. At this time, the fresh water level in the wave-making area increases. According to the communicating vessel principle, the fluid in the wave-making area will slowly flow to the working area. Since the lower edge of the baffle is in the salt water, only the lower salt water will flow into the working area through the bottom of the baffle. With the continuous addition of fresh water, a height difference will appear at the fresh-salt water interface on both sides of the baffle. (3) The baffle is pulled out vertically and stably. The gravity difference of the fluid on both sides of the baffle near the interface will cause disturbance of the stratified fluid interface, thereby forming internal waves.

[0004] If the thickness of the saltwater layer is small, the injection of fresh water is not enough to generate a large interface height difference. At this time, fresh water is pumped out from the upper layer of the wave-making area to make the interface between the two layers of fluid in the wave-making area higher than the fluid interface in the working area. When making concave internal waves, fresh water is generally injected into the wave-making area to make the interface between the stratified fluids in the wave-making area lower than the fluid interface in the working area; when making convex internal waves, the upper layer of fresh water is generally pumped out of the wave-making area to make the interface between the stratified fluids in the wave-making area higher than the fluid interface in the working area.

[0005] Taking water injection to adjust the fluid interface height difference as an example, the traditional gravity collapse method has the following problems when implementing wave generation: (1) Strong mixing in the wave generation zone. Since the free surface area of ​​the wave generation zone is small, there is not enough space to buffer the momentum of the injected fresh water. Therefore, the water injection process has a strong disturbance to the wave generation zone, resulting in a strong mixing of fresh water and salt water; (2) The water injection time is long. Injecting water too quickly will not only cause the mixing of fresh water and salt water, but the rapid adjustment of the pressure difference on both sides of the baffle will also cause the baffle to shake. Therefore, the water injection process needs to be carried out slowly. This puts higher requirements on the sealing of the baffle. If the sealing of the baffle is not good enough, the longer the water injection time, the more leakage on both sides of the baffle, which affects the formation of the interface height difference and the stability of the fluid interface itself; (3) The fluid volume changes. After the baffle is pulled out, the fresh water injected in the process of creating the interface height difference will raise the liquid level in the water tank. If the experiment is repeated, a certain amount of upper fresh water needs to be pumped out to restore the liquid level. The pumping process will also cause disturbances to the freshwater-salt water interface.

[0006] The above problems also exist in the operation of pumping water in the wave-making zone to adjust the fluid interface height. Summary of the invention

[0007] In order to overcome the problems existing in the related art, the disclosed embodiments of the present invention provide a method and system for adjusting the interface difference by using block water in an internal wave experiment using a gravity collapse method, and specifically relate to a method for adjusting the fluid interface height difference by using block water in a wave-making experiment using a gravity collapse method. The purpose of the present invention is to solve the problems that during traditional gravity collapse wave making, the water injection or pumping process easily causes a large disturbance to the fluid in the wave-making area, causing a certain degree of mixing of the stratified fluid; the water injection or pumping time is long, which affects the formation of the interface height difference and the stability of the fluid interface itself; the injection of fresh water in the process of making the interface height difference will raise the liquid level of the original fluid in the water tank, and conversely, the extraction of fresh water will lower the liquid level of the fluid, thereby increasing the difficulty of conducting experiments on the reuse of stratified fluids.

[0008] The technical scheme is as follows: a method for adjusting the interface difference of bulk water in an internal wave experiment using a gravity collapse method, comprising:

[0009] S1, two layers of fluids with different densities are arranged in the experimental water tank, and the experimental water tank is divided into a wave-making area and a working area by a baffle; wherein the two layers of fluids with different densities include fresh water in the upper layer and salt water in the lower layer; the smaller area on both sides of the baffle is the wave-making area, and the larger area is the working area;

[0010] S2, by changing the way of adding or removing the bulk water in the wave-making zone, combined with the state of the baffle plate inserted into the lower salt water layer, a height difference is formed between the stratified fluid interfaces on both sides of the baffle plate, so that the stratified fluid interface in the wave-making zone is lower than the stratified fluid interface in the working zone, or the stratified fluid interface in the wave-making zone is higher than the stratified fluid interface in the working zone; the depth of the baffle plate inserted into the lower salt water layer is such that there is a gap with the bottom of the experimental water tank, so that the wave-making zone and the working zone on both sides of the baffle plate form a communicating vessel;

[0011] S3, after the height difference is formed, the interface of the stratified fluid in the wave-making area is lower than the interface of the stratified fluid in the working area, or the interface of the stratified fluid in the wave-making area is higher than the interface of the stratified fluid in the working area, the baffle is pulled out, and the fluid at the junction of the wave-making area and the working area of ​​the experimental water tank generates internal waves due to the gravity collapse mechanism, and propagates into the working area.

[0012] In step S2, the step of achieving a lower interface of the layered fluid in the wave-making zone than the layered fluid in the working zone comprises:

[0013] S211: estimating the required volume of bulk water according to the target difference between the bottom area of ​​the wave-making zone and the interface height in the working condition;

[0014] S212: Based on the gravity collapse method, after the fluid stratification is stable, the baffle is slowly inserted into the lower salt water layer; block water is added to the wave-making area to raise the fresh water level in the upper layer of the wave-making area, increase the water pressure, and cause a pressure difference on both sides of the baffle; according to the principle of communicating vessels, the lower salt water in the wave-making area is squeezed into the working area to adjust the pressure balance on both sides of the baffle, so that the interface of the stratified fluid in the wave-making area drops and is lower than the interface of the stratified fluid in the working area;

[0015] S213: Prepare water blocks of different sizes, and adjust the height difference between the stratified fluid interface in the wave-making area and the stratified fluid interface in the working area on both sides of the baffle.

[0016] In step S211, the bottom area of ​​the wave-making zone is , the target interface height difference is , the volume of bulk water required is: ;in, is the length of the bottom of the wave-making area, is the width of the bottom surface of the wave-making area;

[0017] In order to maintain the same pressure on both sides of the baffle, when the liquid level changes, the prepared small block of water is used to fine-tune the height difference between the layered fluid interface in the wave-making area and the layered fluid interface in the working area.

[0018] In step S2, the step of achieving a higher level of the fluid interface in the wave-making zone than the fluid interface in the working zone comprises:

[0019] S221: estimating the volume of the required bulk water according to the bottom area of ​​the wave-making zone and the height difference of the target interface;

[0020] S222: After the fluid is stratified and fully settled, the baffle is slowly inserted into the upper fresh water;

[0021] S223: adding bulk water to the wave-making zone;

[0022] S224: let the baffle stand for a while until the fluid on both sides of the baffle plate is stable, and then slowly press the baffle plate down so that the lower edge of the baffle plate penetrates into the lower salt water layer and leaves a gap with the bottom of the water tank;

[0023] S225: The block water is taken out, the liquid level in the wave-making zone is lowered, the water pressure is reduced, and the lower salt water in the working zone enters the wave-making zone through the gap under the baffle. A height difference between the stratified fluid interface in the wave-making zone and the stratified fluid interface in the working zone on both sides of the baffle is formed, so that the stratified fluid interface in the wave-making zone is higher than the stratified fluid interface in the working zone.

[0024] In step S221, when the liquid level changes in order to maintain the same pressure on both sides of the baffle, the height difference between the layered fluid interface in the wave-making area and the layered fluid interface in the working area is fine-tuned using the prepared small block of water;

[0025] In step S222, the baffle is inserted into the upper fresh water at a position where the lower edge of the baffle is above the interface of the stratified fluid.

[0026] In step S223, the volume of the added bulk water is greater than the estimated bulk water volume;

[0027] In step S224, the height of the gap is half the thickness of the lower salt water layer.

[0028] In step S2, the bulk water is a relatively closed water body with a fixed volume and no mixing or substance exchange with the outside world, including fresh water enclosed in a thin plastic barrel or plastic bag.

[0029] Another object of the present invention is to provide a system for adjusting the interface difference of bulk water in an internal wave experiment using a gravity collapse method, the system implementing the method for adjusting the interface difference of bulk water in an internal wave experiment using a gravity collapse method, the system comprising:

[0030] The experimental water tank is used to contain two layers of fluids with different densities, wherein the upper layer is a freshwater layer and the lower layer is a saltwater layer;

[0031] The baffle is used to divide the two layers of fluid with different densities into a wave-making area and a working area; wherein the smaller areas on both sides of the baffle serve as the wave-making area;

[0032] The block water is used to form a height difference between the stratified fluid interfaces on both sides of the baffle by changing the adding or removing method in the wave-making zone and combining the state of the baffle inserted into the lower salt water, so as to achieve that the stratified fluid interface in the wave-making zone is lower than the stratified fluid interface in the working zone or the stratified fluid interface in the wave-making zone is higher than the stratified fluid interface in the working zone.

[0033] Furthermore, the baffle is inserted into the lower salt water to such a depth that there is a gap between the baffle and the bottom of the experimental water tank, so that the wave-making area and the working area on both sides of the baffle form a communicating vessel.

[0034] Further, the bulk water comprises:

[0035] Large bulk water with a volume larger than the estimated bulk water volume. The estimated bulk water volume is ;in, is the length of the bottom of the wave-making area, is the width of the bottom surface of the wave-making zone; the bottom area of ​​the wave-making zone is , the target interface height difference is ;

[0036] Small pieces of water are used to maintain the same pressure on both sides of the baffle. When the liquid level changes, the height difference between the layered fluid interface in the wave-making area and the layered fluid interface in the working area is fine-tuned.

[0037] In combination with all the above-mentioned technical solutions, the beneficial effects possessed by the present invention are as follows: bulk water refers to a relatively closed water body with a fixed volume (weight) that does not mix or exchange substances with the outside world. Two layers of fluids with different densities are arranged in the experimental water tank, and the water tank is divided into a wave-making area and a working area by a baffle. If the interface of the stratified fluid in the wave-making area is to be lower than the working area, the lower edge of the baffle is inserted below the interface of the two layers of fluid (inside the lower salt water / high-density water), leaving a gap with the bottom of the water tank, so that a communicating vessel is formed on both sides of the baffle. Add bulk water to the wave-making area, and gradually squeeze the lower layer of salt water in the wave-making area into the working area, so that a height difference is formed at the interface of the stratified fluid on both sides of the baffle;

[0038] If the interface of the layered fluid in the wave-making zone is to be higher than that in the working zone, first place block water in the wave-making zone, then insert the lower edge of the baffle under the interface of the two layers of fluid, and then gradually remove the block water, so that the lower salt water in the working zone enters the wave-making zone, raising the liquid level of the layered fluid in the wave-making zone. After the interface height difference is formed, the baffle is pulled out, and internal waves are generated inside the fluid due to the gravity collapse mechanism. The traditional gravity collapse method of wave-making realizes the interface height difference on both sides of the baffle by injecting or pumping out fresh water in the wave-making zone, which is time-consuming and easily forms interface disturbance in the wave-making zone, causing a certain degree of mixing of the two layers of fluid, and the total volume of the fluid will also change after the experiment. The present invention replaces the water injection / pumping process in the traditional method with the addition / subtraction of block water, which can accelerate the process of forming the interface difference, reduce the disturbance to the two layers of fluid, and the volume of the fluid in the water tank remains unchanged before and after the experiment.

[0039] Wave making by gravity collapse method requires the generation of two layers of fluid, at least one of which needs to be added with salt and dye. This technical solution significantly shortens the experimental time while reducing the disturbance of the fluid interface during the wave making process, thereby increasing the number of experiments that can be repeated with the stratified fluid configured once, reducing the number of times the stratified fluid is configured, and saving the cost of materials such as water, salt and dye. In the link of generating the height difference of the fluid interface in the gravity collapse method wave making experiment, using block water instead of flowing water is an innovation in experimental technology. The time required for water injection in the gravity collapse method wave making experiment is long, the control of interface disturbance is difficult, and the reusability of the stratified fluid configured once is low. These are all difficulties that need to be faced in conducting water tank experiments. The block water solution has obvious improvements in these three aspects. It is relatively more difficult to maintain the stability of the fluid stratification when using the gravity collapse method to make waves in experiments with simple water tanks and supporting equipment. This technical solution has relatively greater improvements on such experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the description, serve to explain the principles of the present disclosure;

[0041] Figure 1 It is a flow chart of a method for adjusting interface difference of bulk water in an internal wave experiment generated by a gravity collapse method provided by an embodiment of the present invention;

[0042] Figure 2 It is a schematic diagram of a system for adjusting interface difference of bulk water in an internal wave generation experiment using a gravity collapse method provided by an embodiment of the present invention;

[0043] Figure 3 is a schematic diagram of the relationship between internal wave polarity and water depth provided by an embodiment of the present invention;

[0044] Figure 4 This is a simulation effect diagram of a water tank used in a wave-making example provided in an embodiment of the present invention;

[0045] Figure 5 This is an example diagram of an upward convex internal solitary wave generated by adjusting the fluid interface height difference by using block water in a gravity collapse method wave generation experiment provided by an embodiment of the present invention;

[0046] Figure 6 This is an example diagram of a concave internal solitary wave generated by adjusting the fluid interface height difference by using bulk water in a gravity collapse wave generation experiment provided by an embodiment of the present invention;

[0047] In the figure: 1. Experimental water tank; 2. Baffle; 3. Block water. DETAILED DESCRIPTION

[0048] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0049] The innovation of the present invention lies in that: by adding or removing block water in the wave-making zone, the process of water injection or water pumping during wave-making by the traditional gravity collapse method is replaced, so that it is easy to control and reduce the disturbance of the fluid in the wave-making zone and the mixed denaturation of the stratified fluid when the fluid interface height difference on both sides of the baffle is generated; the time for generating the interface height difference is shortened, thereby stabilizing the stratified properties of the fluid and improving the experimental efficiency; it is easy to restore the original state of the fluid after the experiment, reducing the difficulty of repeatedly using the stratified fluid to carry out experiments.

[0050] Embodiment 1, as Figure 1 As shown, the method for adjusting the interface difference of bulk water in the internal wave experiment generated by the gravity collapse method provided in the embodiment of the present invention includes:

[0051] S1, two layers of fluids with different densities are arranged in the experimental water tank, and the experimental water tank is divided into a wave-making area and a working area by a baffle; wherein the two layers of fluids with different densities include fresh water in the upper layer and salt water in the lower layer; the smaller area on both sides of the baffle is the wave-making area, and the larger area is the working area;

[0052] S2, by changing the way of adding or removing the bulk water in the wave-making zone, combined with the state of the baffle plate inserted into the lower salt water layer, a height difference is formed between the stratified fluid interfaces on both sides of the baffle plate, so that the stratified fluid interface in the wave-making zone is lower than the stratified fluid interface in the working zone, or the stratified fluid interface in the wave-making zone is higher than the stratified fluid interface in the working zone; the depth of the baffle plate inserted into the lower salt water layer is such that there is a gap with the bottom of the experimental water tank, so that the wave-making zone and the working zone on both sides of the baffle plate form a communicating vessel;

[0053] S3, after the height difference is formed, the interface of the stratified fluid in the wave-making area is lower than the interface of the stratified fluid in the working area, or the interface of the stratified fluid in the wave-making area is higher than the interface of the stratified fluid in the working area, the baffle is pulled out, and the fluid at the junction of the wave-making area and the working area of ​​the experimental water tank generates internal waves due to the gravity collapse mechanism, and propagates into the working area.

[0054] Example 2, as another implementation of the present invention, the method for adjusting the interface difference of bulk water in the internal wave generation experiment using the gravity collapse method provided in the embodiment of the present invention is divided into two cases according to the relative height of the fluid interface between the wave-making area and the working area, and includes the following steps respectively:

[0055] If you want to make the wave-making area interface lower than the working area interface, do the following:

[0056] S211: Estimate the required volume of bulk water based on the target difference between the bottom area of ​​the wave-making zone and the interface height in the working condition. Assume that the bottom area of ​​the wave-making zone (that is, the free surface area of ​​the fluid in the wave-making zone) is , the target interface height difference is , then the volume of bulk water required is: .

[0057] S212: As with the traditional gravity collapse method, after the fluid stratification is stable, the baffle is slowly inserted into the lower salt water. Slowly add bulk water (fresh water) to the wave-making area to raise the fresh water level in the upper wave-making area and increase the water pressure, thereby causing a pressure difference on both sides of the baffle. According to the principle of communicating vessels, the salt water in the lower layer of the wave-making area is squeezed into the working area to adjust the pressure balance on both sides of the baffle, so that the freshwater-saltwater interface slowly drops.

[0058] S213: Block water of different sizes can be prepared in advance. Block water is slowly added to the wave-making area and replenished or removed according to actual conditions. As in S212, replenishing block water will cause the interface of the wave-making area to drop, while removing block water is the opposite process, which will make the interface of the wave-making area higher than the working area, thereby achieving the effect of adjusting the interface height difference on both sides of the baffle.

[0059] S214: Pull out the baffle to create waves, the principle is the same as the traditional gravity collapse method.

[0060] S215: After the experiment is completed, the block water can be slowly removed to restore the liquid level to the height before the experiment.

[0061] For example, if the interface of the wave-making area is to be higher than the interface of the working area, the following steps are performed:

[0062] S221: estimating the volume of the required bulk water according to the bottom area of ​​the wave-making zone and the height difference of the target interface;

[0063] S222: After the fluid has been stratified and allowed to fully settle, slowly insert the baffle into the upper fresh water layer (the lower edge of the baffle is above the interface).

[0064] S223: Slowly add bulk water to the wave-making area. Because high-density salt water enters the wave-making area in the later stage of the experiment, when the water pressure on both sides of the baffle is the same, the liquid level in the wave-making area will be slightly lower than the working area. Therefore, the volume of bulk water added can be larger than the estimated bulk water volume, so as to avoid the estimated bulk water being insufficient to cause the expected interface height difference. If the interface difference reaches the expected height, the excess bulk water that has not been taken out is in the upper fresh water, which is no different from the fresh water itself and will not affect the wave-making results.

[0065] S224: Let it stand for a while until the fluid on both sides of the baffle plate is stable, then slowly press the baffle plate down so that its lower edge penetrates into the lower layer of salt water and leaves a sufficient gap with the bottom of the water tank (the gap height should preferably be about half the thickness of the salt water).

[0066] S225: Slowly take out the block water. At this time, the liquid level in the wave-making zone is lowered, the water pressure is reduced, and the lower salt water in the working area enters the wave-making zone through the gap under the baffle. The interface height difference on both sides of the baffle is gradually formed.

[0067] S226: Pull out the baffle to create waves, the principle is the same as the traditional gravity collapse method.

[0068] S227: Restore the liquid level to the height before the experiment.

[0069] For example, bulk water refers to a relatively closed body of water with a fixed volume (weight) and no mixing or substance exchange with the outside world, such as fresh water enclosed in a thin plastic bucket or plastic bag. In this experiment, bulk water is fresh water used in experiments filled with mineral water bottles of different sizes.

[0070] For example, S211 and S221 can estimate the volume of bulk water to be added or removed before the experiment begins, and make preparations accordingly. However, the traditional method of injecting water through a water pipe is not easy to estimate the injection time and volume even if the injection amount can be known in advance. Generally, it is necessary to observe the interface height on both sides of the baffle while injecting water.

[0071] For example, in S211 and S221, due to the difference in density between fresh water and salt water and the injection of fresh water or the addition of bulk water, in order to maintain the same pressure on both sides of the baffle, the liquid level will change slightly, and the volume of bulk water required will be slightly different from the estimated result. Some small bulk water is prepared for fine-tuning the interface height difference.

[0072] Exemplarily, the density of the bulk water in S212 is the same as that of fresh water, and adding bulk water to the wave-making zone has the same effect as injecting fresh water through a water pipe, which increases the total volume of the fresh water, thereby pressing down the interface of the wave-making zone.

[0073] For example, in S212, due to the large volume of block water, adding or subtracting block water can complete the water addition or subtraction task in a shorter time, so the speed of forming the target interface height difference in the wave-making area is faster than the water pipe injection method, which can save experimental time.

[0074] For example, in S212, since the bulk water does not mix or exchange substances with the surrounding water, the slow addition of the bulk water does not cause much disturbance to the fluid interface, and is easier to maintain the stratified characteristics of the fluid than the water injection method. Within the allowable error range, the same stratified fluid can be used to repeat the experiment more times by adjusting the liquid level difference with the bulk water.

[0075] Exemplarily, in S215 and S225, bulk water can be added or removed completely during the experiment without changing the volumes of fresh water and salt water in the tank before the experiment begins.

[0076] Exemplarily, the functions of the baffle in S222 are, first, to prevent the bulk water from drifting toward the working area, and second, to form a communicating vessel on both sides of the baffle; after the bulk water is added, the upper fresh water enters the working area through the bottom of the baffle, while the interface between the salt water and the stratified fluid will not change.

[0077] Exemplarily, in S223, both sides of the baffle are still communicating vessels, but only the lower salt water can enter and exit the wave-making area through the lower edge of the baffle.

[0078] Exemplarily, in S227, after all the bulk water is taken out, the liquid level can be restored to the height before the experiment, and the volumes of the two layers of fluid remain unchanged.

[0079] It can be seen from the above embodiments that in the experimental wave generation of the present invention, the traditional gravity collapse method is improved, and the interface height is adjusted by using bulk water. Bulk water refers to a relatively closed water body with a fixed volume (weight) and no mixing or material exchange with the outside world, such as fresh water enclosed in a thin plastic barrel or plastic bag. In the experiment of the present invention, the bulk water is fresh water for the experiment filled with mineral water bottles of different sizes.

[0080] The method of the present invention is characterized in that bulk water is used to adjust the interface height difference, the target interface height difference can be formed quickly, the disturbance to the stratified fluid interface is small, and the fluid volume is not changed during the experiment. This brings great convenience to the experiment and saves time.

[0081] Embodiment 3, as Figure 2 As shown in the figure, the bulk water adjustment interface difference system (gravity collapse wave making device) in the internal wave generation experiment using the gravity collapse method includes:

[0082] Experimental water tank 1, used to contain two layers of fluids with different densities, wherein the upper layer is a freshwater layer and the lower layer is a saltwater layer;

[0083] The baffle 2 is used to divide the two layers of fluid with different densities into a wave-making area and a working area; wherein the smaller area of ​​the experimental water tank 1 divided by the baffle 2 is used as the wave-making area;

[0084] The block water 3 is used to form a height difference between the stratified fluid interfaces on both sides of the baffle 2 by changing the adding or removing method in the wave-making zone and combining the state of the baffle 2 inserted into the lower salt water, so as to achieve that the stratified fluid interface in the wave-making zone is lower than the stratified fluid interface in the working zone or the stratified fluid interface in the wave-making zone is higher than the stratified fluid interface in the working zone.

[0085] The baffle plate 2 is inserted into the lower salt water to a depth where there is a gap between the baffle plate 2 and the bottom of the experimental water tank, so that the wave-making area and the working area on both sides of the baffle plate form a communicating vessel.

[0086] The bulk water 3 includes: a large bulk water having a volume larger than the estimated bulk water volume, the estimated bulk water volume being ,in, is the length of the bottom of the wave-making area, is the width of the bottom surface of the wave-making zone; the bottom area of ​​the wave-making zone is , the target interface height difference is ;

[0087] Small pieces of water are used to maintain the same pressure on both sides of the baffle 2. When the liquid level changes, the height difference between the layered fluid interface in the wave-making area and the layered fluid interface in the working area is fine-tuned.

[0088] Among them, exemplary, Figure 2 middle, are the thickness of the upper freshwater layer and the lower dyed saltwater layer, , is the collapse depth (the height difference between the two layers of fluid interface on the left and right sides of the baffle). The baffle is set at L on the left side of the flume, and the dotted line in the experimental flume is the observation section (i.e., the section where the high-speed camera is arranged).

[0089] Application examples.

[0090] Figure 3 It is a schematic diagram of the relationship between the internal wave polarity and the water depth provided by an embodiment of the present invention. In the left figure, the thickness of the upper fluid layer is greater than that of the lower fluid layer, and the interface internal wave is usually convex; in the right figure, the thickness of the upper fluid layer is less than that of the lower fluid layer, and the interface internal wave is usually concave. In the gravity collapse wave-making experiment, the convex internal wave must make the interface of the stratified fluid in the wave-making area higher than the interface of the working area. In the corresponding block water method, block water must be taken out of the wave-making area of ​​the water tank; the concave internal wave must make the interface of the stratified fluid in the wave-making area lower than the interface of the working area. In the corresponding block water method, block water must be added to the wave-making area of ​​the water tank.

[0091] Figure 4 This is the simulation effect of the water tank used in the wave-making example provided in the embodiment of the present invention. The total length of the water tank is 500.0 cm, the width is 48.6 cm, and the height is 60.0 cm. The two side surfaces and the bottom surface are each made of 5 acrylic plates with lengths ranging from 96.1 to 103.7 cm and thicknesses of 1.0 cm. The bottom surface of the water tank is supported by two metal plates with a length of 500 cm, a width of 8 cm, and a height of 4 cm, 45 cm above the ground. The acrylic plate is fixed to the metal frame with structural adhesive, and then pasted with acrylic glue for a second time, supplemented with glass glue for waterproofing. Make a mark at about 25 cm at one end of the water tank, which is the insertion position of the baffle when making waves. The baffle divides the water tank into two large and small areas. The smaller side is the wave-making area, and the larger side is the working area. Two 50cm long transparent plastic rulers and several label stickers are pasted on the side walls of the sink to determine the depth; two saw blades are pasted on the bottom of the sink to allow the PIV pulse laser to pass through the narrow gap in the middle of the saw blades, reducing the scattering of the laser by the acrylic plate.

[0092] Figure 5This is an example of an upward convex internal solitary wave generated by adjusting the fluid interface height difference with block water in the gravity collapse wave generation experiment provided by the embodiment of the present invention. The density of the lower salt water is 1030kg / m 3 , thickness 12.3cm; add tracer particles and blue ink. Stir evenly and let stand. Add fresh water to the upper layer, layer thickness 17.5cm, total liquid level height 29.8cm. Fluid interface is clear. Fresh water density 996kg / m 3 The method of removing the bulk water was used to make the interface of the stratified fluid in the wave-making area 8 cm higher than the working area. After the baffle was pulled out, the change of the interface height over time was recorded at a distance of about 2 m from the wave-making area, and an upward convex internal solitary wave was observed.

[0093] Figure 6 This is an example of a concave internal solitary wave generated by adjusting the fluid interface height difference with block water in the gravity collapse wave generation experiment provided by the embodiment of the present invention. Salt water density 1030kg / m 3 , thickness 20cm; add tracer particles and blue ink. Stir evenly and let stand. Add fresh water to the upper layer, layer thickness 10cm, total liquid level height 30cm. Fluid interface is clear. Fresh water density 996kg / m 3 By adding bulk water, the interface of the stratified fluid in the wave-making area was made 8 cm lower than the working area. After the baffle was pulled out, the change of the interface height over time was recorded at a distance of about 2 m from the wave-making area, and a concave internal solitary wave was observed.

[0094] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0095] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for adjusting the interface difference of bulk water in an internal wave experiment using a gravity collapse method, characterized in that: The method includes: S1, two layers of fluids with different densities are arranged in the experimental water tank, and the experimental water tank is divided into a wave-making area and a working area by a baffle; wherein the two layers of fluids with different densities include fresh water in the upper layer and salt water in the lower layer; the smaller area on both sides of the baffle is the wave-making area, and the larger area is the working area; S2, by changing the way of adding or removing the bulk water in the wave-making zone, combined with the state of the baffle plate inserted into the lower salt water layer, a height difference is formed between the stratified fluid interfaces on both sides of the baffle plate, so that the stratified fluid interface in the wave-making zone is lower than the stratified fluid interface in the working zone, or the stratified fluid interface in the wave-making zone is higher than the stratified fluid interface in the working zone; the depth of the baffle plate inserted into the lower salt water layer is such that there is a gap with the bottom of the experimental water tank, so that the wave-making zone and the working zone on both sides of the baffle plate form a communicating vessel; S3, after the height difference is formed, the interface of the stratified fluid in the wave-making area is lower than the interface of the stratified fluid in the working area, or the interface of the stratified fluid in the wave-making area is higher than the interface of the stratified fluid in the working area, the baffle is pulled out, and the fluid at the junction of the wave-making area and the working area of ​​the experimental water tank generates internal waves due to the gravity collapse mechanism, and propagates into the working area; In step S2, the step of achieving a lower interface of the layered fluid in the wave-making zone than the layered fluid in the working zone comprises: S211: estimating the required volume of bulk water according to the target difference between the bottom area of ​​the wave-making zone and the interface height in the working condition; S212: Based on the gravity collapse method, after the fluid stratification is stable, the baffle is slowly inserted into the lower salt water layer; block water is added to the wave-making area to raise the fresh water level in the upper layer of the wave-making area, increase the water pressure, and cause a pressure difference on both sides of the baffle; according to the principle of communicating vessels, the lower salt water in the wave-making area is squeezed into the working area to adjust the pressure balance on both sides of the baffle, so that the interface of the stratified fluid in the wave-making area drops and is lower than the interface of the stratified fluid in the working area; S213: preparing blocks of water of different sizes, and adjusting the height difference between the layered fluid interface of the wave-making area and the layered fluid interface of the working area on both sides of the baffle; In step S2, the step of achieving a stratified fluid interface in the wave-making zone higher than a stratified fluid interface in the working zone comprises: S221: estimating the volume of the required bulk water according to the bottom area of ​​the wave-making zone and the height difference of the target interface; S222: After the fluid is stratified and fully allowed to stand, the baffle is slowly inserted into the upper fresh water layer; the position where the baffle is inserted into the upper fresh water layer is: the lower edge of the baffle is above the interface of the stratified fluid; S223: adding bulk water to the wave-making zone; S224: After the fluid on both sides of the baffle plate is stable, the baffle plate is pressed down so that the lower edge of the baffle plate penetrates into the lower salt water layer and leaves a gap with the bottom of the water tank; S225: The block water is taken out, the liquid level in the wave-making area is lowered, the water pressure is reduced, and the lower salt water in the working area enters the wave-making area through the gap under the baffle. A height difference between the layered fluid interface in the wave-making area and the layered fluid interface in the working area on both sides of the baffle is formed, so that the layered fluid interface in the wave-making area is higher than the layered fluid interface in the working area. Bulk water is a relatively closed body of water with a fixed volume that does not mix or exchange substances with the outside world, including fresh water enclosed in thin plastic barrels or plastic bags.

2. The method for adjusting the interface difference of bulk water in the internal wave generation experiment using the gravity collapse method according to claim 1, characterized in that: In step S211, the bottom area of ​​the wave-making zone is , the target interface height difference is , the volume of bulk water required is: ;in, is the length of the bottom of the wave-making area, is the width of the bottom surface of the wave-making area; In order to maintain the same pressure on both sides of the baffle, when the liquid level changes, the prepared small block of water is used to fine-tune the height difference between the layered fluid interface in the wave-making area and the layered fluid interface in the working area.

3. The method for adjusting the interface difference of bulk water in the internal wave experiment using the gravity collapse method according to claim 1, characterized in that: In step S223, the volume of the added bulk water is greater than the estimated bulk water volume; In step S224, the height of the gap is half the thickness of the lower salt water layer.

4. A bulk water adjustment interface difference system in an internal wave generation experiment using a gravity collapse method, characterized in that: The system implements the method for adjusting the interface difference of bulk water in the internal wave generation experiment using the gravity collapse method as claimed in any one of claims 1 to 3, and the system comprises: An experimental water tank (1) is used to contain two layers of fluids with different densities, wherein the upper layer is a freshwater layer and the lower layer is a saltwater layer; The baffle (2) is used to divide two layers of fluid with different densities into a wave-making area and a working area; wherein the smaller areas on both sides of the baffle (2) serve as the wave-making area; The block water (3) is used to change the adding or removing method in the wave-making zone and the state of the baffle plate (2) inserted into the lower salt water layer, so that the interface of the stratified fluid on both sides of the baffle plate (2) forms a height difference, so that the interface of the stratified fluid in the wave-making zone is lower than the interface of the stratified fluid in the working zone or the interface of the stratified fluid in the wave-making zone is higher than the interface of the stratified fluid in the working zone; The baffle (2) is inserted into the lower salt water layer to a depth where there is a gap between the baffle and the bottom of the experimental water tank, so that the wave-making area and the working area on both sides of the baffle form a communicating vessel.

5. The bulk water adjustment interface difference system in the internal wave generation experiment using the gravity collapse method according to claim 4 is characterized in that: The bulk water (3) comprises: Large bulk water with a volume larger than the estimated bulk water volume. The estimated bulk water volume is ;in, is the length of the bottom of the wave-making area, is the width of the bottom surface of the wave-making zone; the bottom area of ​​the wave-making zone is , the target interface height difference is ; The small block of water is used to fine-tune the height difference between the layered fluid interface in the wave-making zone and the layered fluid interface in the working zone so that the height difference of the liquid surface on both sides of the baffle (2) reaches the target height difference.

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