CN110503882A - Apparatus and method for simulating uniform density-driven circulation in coastal aquifers - Google Patents

Abstract

The invention relates to a circulation simulation device driven by uniform density in coastal aquifers, which is characterized in that it includes a main body box, and two permeable baffles each with a plurality of permeable holes are fixed in the main box, which are respectively the first permeable baffles and the second permeable baffle, the first permeable baffle and the second permeable baffle are arranged oppositely, and the two permeable baffles divide the main box into a first cavity, a second cavity and a second cavity. The third cavity, the first cavity, the second cavity and the third cavity are connected in sequence, and the second cavity is equipped with a porous medium; it also includes a fresh water system and a salt water system, the The salt water system includes a salt water inlet system and a salt water outlet system respectively connected to the first cavity, and the fresh water system includes a fresh water inlet system and a fresh water outlet system respectively connected to the third cavity; The main box body is made of transparent material.

Description

Apparatus and method for simulating uniform density-driven circulation in coastal aquifers

technical field

The invention relates to the field of freshwater resources research, in particular to a circulation simulation device driven by uniform density in coastal aquifers and a method for using it.

Background technique

Groundwater flow patterns within the brackish-fresh water transition zone of coastal aquifers include rotational cycles of generation from the ocean and flow of brackish water in the aquifer. The tracer experiments presented here are to analyze the structure of the brackish-fresh water cycle and quantitatively simulate the distribution of salinity at the brackish-fresh water interface. The experimental results show that the rotation along the brine streamline starts from the bottom of the interface (99% of the salt water concentration contour) and completes at the bottom tenth of the interface (94% of the salt water concentration contour). In the upper part of the interface, after the rotation is completed, the water flows from the fresh water to the sea. The known hydrochemical salt-fresh water interface can be divided into two parts according to its physical properties: (1) the lower part is the "flow rotation zone", which is defined by the convective circulation streamline; (2) the upper part is the "diffusion zone", which defines Dilution for diffusion. Sensitivity analysis shows that the physical structure of the interface is related to the lateral dispersibility. At higher diffusivity conditions, the spin width increases, but is done at most in the lower third of the interface. For the diffusion coefficient, the rotation starts at the bottom of the interface. So, since there is no line with a flow below 99%, the brackish water going to the sea is always diluted relative to its original salinity. These flow patterns can affect coastal hydrological processes, such as submarine groundwater discharge and the transport of chemicals in aquifers.

The circulation of saline water in coastal aquifers reflects the interaction between terrestrial hydrological processes and ocean circulation. This cyclic flow pattern is driven by short-time scales, such as waves and tides, as well as diffusion cycles driven by seasonal and even long-term density currents. The latter is often a natural phenomenon caused by density differences between fresh groundwater and saltwater from the ocean. These water bodies tend to approach the brackish-fresh water interface, which can also be called the mixed zone. Hydrodynamic diffusion drives the circulation of salt water, and causes the salt water body in the ocean to continuously intrude into the freshwater aquifer, and on the other hand, it also discharges to the sea along the salt-fresh water interface. Knowledge of the long-term coastal water circulation structure is important for submarine groundwater discharge and mass balance in coastal areas. The saline water cycle mentioned here is an important content for the study of hydrogeochemical processes, pollutants and nutrient transport and other aspects that play a decisive role in the brackish-fresh water interface. And it can be said that this is very important for water resource management and planned use in coastal areas. A structural understanding of the hydrodynamic processes at the land-sea interface is important for the identification of seafloor groundwater discharge and for the calculation of water balance in coastal areas.

In the past, many studies have used a variety of technical methods to quantitatively study the circulation process driven by the density of salt water. There have been many studies on fluid dynamics and salt transport based on field monitoring and numerical simulation. However, studies of the effects of saline water circulation on seafloor groundwater discharge have revealed a strong dependence of convective circulation on aquifer dispersibility. Physical simulation experiments related to this are very rare. The indoor physical simulation experiment designed here can be used to obtain information related to the variable density salt water cycle. Quantify and better understand the process of variable-density saline water circulation through the combination of acquired information and numerical simulations, analyze the precise water flow pattern of the brackish-fresh water interface/mixed zone, and understand the structure of the brackish-fresh water interface through changes in water body salinity and physical parameters feature.

Contents of the invention

The technical problem to be solved by the invention is to provide a circulation simulation device driven by uniform density in the coastal aquifer and a use method.

The technical solution of the present invention to solve the above-mentioned technical problems is as follows: the uniform density-driven circulation simulation device in the coastal aquifer includes a main box, and two vertical permeable baffles with a number of permeable holes are fixed inside the main box , respectively the first permeable baffle and the second permeable baffle, the first permeable baffle and the second permeable baffle are oppositely arranged, and the two permeable baffles divide the main box into a first A cavity, a second cavity and a third cavity, the first cavity, the second cavity and the third cavity communicate in sequence, the second cavity is filled with porous media; fresh water is also included system and a salt water system, the salt water system includes a salt water inlet system and a salt water outlet system respectively communicated with the first cavity, and the fresh water system includes a fresh water inlet system respectively communicated with the third cavity Water system and fresh water outlet system; the main box is made of transparent material; there is transparent fresh water in the fresh water inlet system, and colored salt water in the salt water inlet system.

The beneficial effect of the invention is that it can be used to obtain information related to variable density salt water circulation. Quantify and better understand the process of variable-density saline water circulation through the combination of acquired information and numerical simulations, analyze the precise water flow pattern of the brackish-fresh water interface/mixed zone, and understand the structure of the brackish-fresh water interface through changes in water body salinity and physical parameters feature. Characterization and quantification of circulation flow patterns within the freshwater-brine interface driven by density flow in littoral phreatic aquifers under steady-state conditions. On the basis of certain hydrochemical monitoring data, it is possible to determine the vertical profile of the groundwater flow velocity in the brackish-fresh water transition zone, which can be used to calculate the contribution of solutes (such as salt, pollutants and nutrients) to the ocean.

On the basis of above-mentioned technical scheme, the present invention can also be improved as follows:

Further, the salt water inlet system includes a salt water inlet tank and a salt water pump, the salt water inlet tank communicates with the salt water pump through a pipe, and the salt water pump and the first cavity are connected through a pipe The salt water pump pumps the liquid in the salt water inlet tank into the first cavity; the salt water outlet system includes a salt water collection tank, and the salt water collection tank is connected with the first chamber through a pipe A cavity is connected, and the salt water collection tank is used to collect the liquid flowing out of the first cavity; the fresh water inlet system includes a fresh water inlet tank and a fresh water pump, and the fresh water inlet tank and the fresh water The pump is connected, the fresh water pump is connected with the third cavity, and the fresh water pump pumps the water in the fresh water inlet tank into the third cavity; the fresh water outlet system includes a fresh water collection tank, The fresh water collection tank communicates with the third cavity through a tube, and the fresh water collection tank is used to collect liquid flowing out of the third cavity.

The beneficial effect of adopting the above further solution is to set up a salt water inlet system, a salt water outlet system, a fresh water inlet system and a fresh water outlet system which are simple and easy to operate.

Further, the upper end of the main box is open, and the salt water inlet system communicates with the first cavity through the hole on the side wall of the main box corresponding to the first cavity, and the salt water The water outlet system communicates with the first cavity through the hole on the side wall of the main box corresponding to the first cavity; the fresh water inlet system communicates with the third cavity through the opening The fresh water outlet system communicates with the third cavity through a hole on the side wall of the main box corresponding to the third cavity.

The beneficial effect of adopting the above further scheme is that the upper end of the main box is open, which facilitates the exchange of porous media and the discharge and intake of water in the first cavity and the third cavity; the fresh water inlet system and the fresh water outlet system are specifically defined , the location and setting of the salt water inlet system and the salt water outlet system can better realize the required simulation functions.

Further, the main box is a cuboid, the length of the main box is 1m, the width is 0.05m, and the height is 0.5m.

The beneficial effect of adopting the above further solution is that the rectangular parallelepiped is a more commonly used form of the main box, the simulation effect is good, the length, width and height are limited, and the simulation effect can be well realized under the premise of saving materials.

Further, one end of the porous medium is in contact with the first water-permeable baffle, and the other end of the porous medium is in contact with the second water-permeable baffle.

The beneficial effect of adopting the above further scheme is that the porous medium occupies a relatively large space in the second cavity and makes full use of it.

Further, the porous medium is silica sand particles, and the diameter of the silica sand particles is in the range of 500-850 μm.

The beneficial effect of adopting the above further solution is that the silica sand grains have a good simulation effect, and the silica sand grains are more commonly used in this particle size range.

Further, the side of the main box corresponding to the second cavity has a water injection hole, and a sealing cover for sealing the water injection hole is detachably connected outside the water injection hole.

The beneficial effect of adopting the above further solution is that it is used to inject brine into the second cavity, and the color of the brine injected into the second cavity by the brine tank is different, so as to achieve the effect of simulation.

The present invention also relates to a method for using the uniform density-driven circulation simulation device in the coastal aquifer, comprising the following steps, step 1: prepare transparent fresh water, prepare brine with the same concentration for dyeing in different colors, and obtain the first zone Colored brine and second colored brine; step 2: first discharge the first colored brine into the first cavity through the salt water inlet system, and at the same time, let the fresh water through the freshwater inlet The system is discharged into the third cavity; step 3: the first salt water in the first cavity and the fresh water in the third cavity both flow into the second cavity, and the first The salt water and the fresh water contact, merge and form a stable state in the second cavity. During this process, the color distribution of the water in the second cavity is observed or photographed. The salt water outlet system and the first cavity correspond to the height of the main tank connection, and the water is discharged through the salt water outlet system, and the third cavity exceeds the fresh water outlet system and the third cavity The water corresponding to the height of the connection of the main tank is discharged through the fresh water outlet system; step 4: the second colored brine is discharged into the first cavity through the salt water inlet system to replace the first belt At the same time, the fresh water is discharged into the third cavity through the fresh water inlet system. During this process, the color distribution of the water in the second cavity is observed or photographed, and the first cavity The water in the body that exceeds the height of the connection between the salt water outlet system and the first cavity corresponding to the main box is discharged through the salt water outlet system, and the water in the third cavity exceeds the height between the fresh water outlet system and the The water at the height of the third cavity corresponding to the connecting part of the main box is discharged through the fresh water outlet system; Step 5: According to the color migration and distribution conditions recorded in the step 3 and step 4, the stable water in the simulated coastal phreatic aquifer is obtained. Circulation patterns driven by uniform seawater density under state conditions.

The beneficial effect of adopting the above-mentioned further scheme is that the front source tracing method can be used to simulate the migration and formation process of the front in the process of sea surface intrusion through the observed phenomenon, and the simulation results are clear and intuitive. , making the density-driven circulation process more obvious, easy to observe and record, and the simulation effect is in good agreement with the natural process.

The present invention also relates to a method for using the uniform density-driven circulation simulation device in the coastal aquifer, comprising the following steps, step 1: preparing fresh water, preparing salt water with the same concentration for dyeing with different colors, and obtaining the first colored salt water and the second colored brine; step 2: first discharge the first colored brine into the first cavity through the salt water inlet system, and at the same time, discharge the fresh water through the fresh water inlet system into the third cavity; step 3: the first salt water in the first cavity and the fresh water in the third cavity flow into the second cavity, and the first salt water Contact with the fresh water in the second cavity, merge and form a stable state, during this process, observe or take pictures of the color distribution of the water in the second cavity, and the salt water in the first cavity The water outlet system and the first cavity correspond to the height of the main box connected to the water through the salt water outlet system, and the fresh water outlet system in the third cavity exceeds the main body corresponding to the third cavity. The water at the height of the connection of the tank is discharged through the fresh water outlet system; step 4: open the water injection hole, and inject the second colored brine into the second cavity through the water injection hole with the first colored salt water. At the same time, the fresh water is discharged into the third chamber through the fresh water inlet system. During this process, the color distribution of the water in the second chamber is observed or photographed, and the first The water in a cavity that exceeds the height of the connection between the salt water outlet system and the first cavity corresponding to the main box is discharged through the salt water outlet system, and the water in the third cavity exceeds the height between the fresh water outlet system and the first cavity. The water at the height of the third cavity corresponding to the connecting part of the main box is discharged through the fresh water outlet system; Step 5: According to the color migration and distribution recorded in Step 3 and Step 4, a simulated coastal phreatic aquifer is obtained Circulation patterns driven by uniform seawater density under mesosteady-state conditions.

The beneficial effect of adopting the above-mentioned further scheme is that the formation, migration and disappearance process of point source pollutants with different densities in the intruded aquifer can be accurately simulated in the coastal phreatic aquifer through the observed phenomenon by using the point source method. The simulation process is clear and intuitive, the method is simple and convenient, and the simulation effect is in good agreement with the natural situation.

Further, the dyeing process of the brine is to add a dye to the brine to obtain the colored brine.

The beneficial effect of adopting the above further solution is to provide a convenient and quick dyeing method.

Description of drawings

Fig. 1 is a schematic diagram of the present invention.

In the accompanying drawings, the list of parts represented by each label is as follows:

1. Main box body, 201. First permeable baffle, 202. Second permeable baffle, 3. First cavity, 4. Second cavity, 5. Third cavity, 6. Porous medium, 7. Salt water inlet system, 8. Salt water outlet system, 9. Fresh water inlet system, 10. Fresh water outlet system, 11. Water injection hole, 12. Salt water inlet tank, 13. Salt water pump, 14. Salt water collection tank , 15, fresh water inlet tank, 16, fresh water pump, 17, fresh water collection tank.

Detailed ways

The principles and features of the present invention are described below in conjunction with the accompanying drawings, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention.

Example

The uniform density-driven circulation simulation device in coastal aquifers includes a main body box 1, and two vertical permeable baffles with a number of permeable holes are fixed inside the main box 1, which are respectively the first permeable baffles 201 and the second permeable baffle 202, the first permeable baffle 201 and the second permeable baffle 202 are arranged oppositely, and the two permeable baffles divide the main box 1 into the first cavity 3 , the second cavity 4 and the third cavity 5, the first cavity 3, the second cavity 4 and the third cavity 5 communicate in sequence, and the second cavity 4 is equipped with a porous medium 6; It also includes a fresh water system and a salt water system, the salt water system includes a salt water inlet system 7 and a salt water outlet system 8 respectively communicated with the first cavity 3, and the fresh water system includes a salt water outlet system respectively connected to the first cavity 3 Fresh water inlet system 9 and fresh water outlet system 10 connected by the third cavity 5; the main box 1 is made of transparent material; transparent fresh water is arranged in the fresh water inlet system 9, and the salt water inlet system 7 contains colored brine.

Specifically, as shown in Fig. 1 , the main box body is a cuboid, and the first water-permeable baffle plate and the second water-permeable baffle plate are parallel to and perpendicular to the side wall of the main box body.

Specifically, as shown in Figure 1, the porous medium is made of silica sand, one end of the porous medium is in contact with the first permeable baffle, and the other end is in contact with the second permeable baffle, and the height of the first permeable baffle is higher than that of one end of the porous medium. The height of the second permeable baffle is higher than the height of the other end of the porous medium. When the main box is a cuboid, the porous medium is preferably a cuboid.

Specifically, the permeable baffle allows water to pass through, but does not allow porous media to pass through. When the porous medium is silica sand, the diameter of the holes on the permeable baffle is smaller than the silica sand; in order not to affect the experimental results, the permeable baffle is made of stainless material. to make.

Specifically, the height of the connection between the salt water outlet system and the salt water tank determines the water level in the salt water tank, and the height of the connection between the fresh water outlet system and the fresh water tank determines the water level in the fresh water tank. Preferably, the height of the connection between the salt water outlet system and the salt water tank is the same as the height of the connection between the fresh water outlet system and the fresh water tank.

The experiments were carried out in a quasi-two-dimensional rectangular Plexiglas (12 mm thick) main box to simulate diving coastal aquifers (Fig. 1). Water-sand tank The launder is divided into three distinct chambers: a central water-sand chamber filled with porous media as an aquifer, flanked by brackish and fresh water tanks controlled by constant head boundary conditions. As shown in Figure 1, the left chamber is the offshore saltwater boundary, and the right chamber is the regional freshwater inland boundary. The three chambers are separated by fine mesh permeable baffles to prevent particulate matter from passing through the central water-sand chamber into the brackish water on both sides. A small hole (water injection hole) is left at the rear of the water sand tank and plugged with a small cap for injecting tracer.

The water flask was filled with porous media silica sand (diameter range 500-850 μm), and the dust and clay minerals were removed with distilled water. In order to prevent the tracer from being adsorbed, dilute hydrochloric acid was used to remove the oxide layer on the surface of the quartz particles. The filling of the sand box is carried out under saturated conditions, and the sand body is poured into the water to avoid trapping air bubbles. The filling process creates slight horizontal stratification in the porous media, resulting in anisotropy. The average porosity (0.37) of sandy soil was directly measured by the volume method. The longitudinal dispersion of 0.003m can be calculated from the breakthrough curve, and the transverse dispersion is estimated to be 0.0003m, which is 10 times smaller than the longitudinal dispersion. Throughout the experiment, the distribution of the tracer dye in the water sandbox was recorded with a digital camera. Documentation is done at various time intervals, controlled by the rate of change of the location of the water type.

As a further solution of this embodiment, the salt water inlet system 7 includes a salt water inlet tank 12 and a salt water pump 13, the salt water inlet tank 12 and the salt water pump 13 are connected through pipes, and the salt water The water pump 13 communicates with the first cavity 3 through a pipe, and the salt water pump 13 pumps the liquid in the salt water inlet tank 12 into the first cavity 3; the salt water outlet system 8 Including a salt water collection tank 14, the salt water collection tank 14 communicates with the first cavity 3 through a pipe, and the salt water collection tank 14 is used to collect the liquid flowing out of the first cavity 3; The fresh water intake system 9 includes a fresh water intake tank 15 and a fresh water pump 16, the fresh water intake tank 15 communicates with the fresh water pump 16, and the fresh water pump 16 communicates with the third cavity 5, so The fresh water pump 16 pumps the water in the fresh water inlet tank 15 into the third cavity 5; the fresh water outlet system 10 includes a fresh water collection tank 17, and the fresh water collection tank 17 is connected to the third chamber through a pipe. The cavities 5 are connected, and the fresh water collection tank 17 is used to collect the liquid flowing out of the third cavity 5 .

Specifically, the connection between the salt water outlet system 8 and the first cavity 3 corresponding to the main box 1 has a height value greater than 0, and the specific height value depends on the situation; the fresh water outlet system 10 and the The third cavity 5 has a height greater than 0 corresponding to the connecting part of the main box 1, and the specific height depends on the situation.

The initial conditions and boundary conditions of the whole experiment are determined by the water levels of the salt water chamber and the fresh water chamber on both sides (namely, the water levels of the first chamber and the third chamber, respectively). These water levels are controlled by a make-up-overflow device, piping, and pumping system, as shown in Figure 1. The water level is higher than the height of the connection between the salt water outlet system and the corresponding side wall of the first cavity, and the water will flow out from the connection between the salt water outlet system and the corresponding side wall of the first cavity to ensure a constant salt water level, that is to say, the salt water The height of the connection between the water outlet system and the corresponding side wall of the first cavity determines the height of the water level in the first cavity, and also represents the open sea water level. The water level is higher than the height of the connection between the fresh water outlet system and the corresponding side wall of the third cavity, and water will flow out from the connection between the fresh water outlet system and the corresponding side wall of the third cavity to ensure a constant fresh water level, that is to say, the fresh water outlet system and The height of the communication part of the third cavity corresponding to the side wall determines the height of the third water level.

As a further solution of this embodiment, the upper end of the main box 1 is open, and the salt water inlet system 7 corresponds to the hole on the side wall of the main box 1 through the first cavity 3 and the The first cavity 3 communicates, and the salt water outlet system 8 communicates with the first cavity 3 through a hole on the side wall of the main box 1 corresponding to the first cavity 3; The water inlet system 9 communicates with the third cavity 5 through the opening, and the fresh water outlet system 10 communicates with the third cavity 5 through a hole on the side wall of the main box 1 . The third cavity 5 is in communication with each other.

As a further solution of this embodiment, the main box body 1 is a cuboid, and the length of the main box body 1 is 1 m, the width is 0.05 m, and the height is 0.5 m.

As a further solution of this embodiment, one end of the porous medium 6 is in contact with the first water-permeable baffle 201 , and the other end of the porous medium 6 is in contact with the second water-permeable baffle 202 .

As a further solution of this embodiment, the porous medium 6 is silica sand particles, and the diameter of the silica sand particles is in the range of 500-850 μm.

As a further solution of this embodiment, the side of the main box 1 corresponding to the second cavity 4 has a water injection hole 11, and a seal for sealing the water injection hole 11 is detachably connected outside the water injection hole 11. cover.

Specifically, the side refers to the side where the permeable baffle is not installed, and there may be water injection holes on either side or both sides.

The present invention also relates to a method for using the uniform density-driven circulation simulation device in the coastal aquifer, comprising the following steps,

Step 1: prepare transparent fresh water, prepare the same brine of concentration to dye in different colors, obtain the first colored brine and the second colored brine;

Step 2: first discharge the first colored salt water into the first chamber 3 through the salt water inlet system 7, and at the same time, discharge the fresh water into the first cavity through the fresh water inlet system 9 Inside the third cavity 5;

Step 3: Both the first colored brine in the first cavity 3 and the fresh water in the third cavity 5 flow into the second cavity 4, and the first colored brine Contact with the fresh water in the second cavity 4, merge and form a stable state, in the process, observe or take pictures of the color distribution of the water in the second cavity 4, the first cavity 3 The water that exceeds the height of the connection between the salt water outlet system 8 and the first cavity 3 corresponding to the main box 1 is discharged through the salt water outlet system 8, and the water in the third cavity 5 exceeds the The fresh water outlet system 10 is discharged through the fresh water outlet system 10 through the fresh water outlet system 10;

Step 4: Discharging the second colored brine into the first chamber 3 through the salt water inlet system 7 to replace the first colored brine, and at the same time, feeding the fresh water through the fresh water inlet The water system 9 is discharged into the third cavity 5. During this process, the color distribution of the water in the second cavity 4 is observed or photographed, and the salt water outlet system in the first cavity 3 exceeds 8 The water at the height of the connection with the first cavity 3 corresponding to the main box 1 is discharged through the salt water outlet system 8, and the third cavity 5 exceeds the fresh water outlet system 10 and the second The water at the height of the connecting part of the three chambers 5 corresponding to the main box 1 is discharged through the fresh water outlet system 10;

Step 5: According to the color distribution obtained in Step 3 and Step 4, a circulation pattern driven by uniform seawater density under steady-state conditions in the simulated littoral phreatic aquifer is obtained.

The present invention also relates to a method for using the uniform density-driven circulation simulation device in the coastal aquifer, comprising the following steps,

Step 1: prepare transparent fresh water, prepare the same brine of concentration to dye in different colors, obtain the first colored brine and the second colored brine;

Step 2: first discharge the first colored salt water into the first chamber 3 through the salt water inlet system 7, and at the same time, discharge the fresh water into the first cavity through the fresh water inlet system 9 Inside the third cavity 5;

Step 3: Both the first colored brine in the first cavity 3 and the fresh water in the third cavity 5 flow into the second cavity 4, and the first colored brine Contact with the fresh water in the second cavity 4, merge and form a stable state, in the process, observe or take pictures of the color distribution of the water in the second cavity 4, the first cavity 3 The water that exceeds the height of the connection between the salt water outlet system 8 and the first cavity 3 corresponding to the main box 1 is discharged through the salt water outlet system 8, and the water in the third cavity 5 exceeds the The fresh water outlet system 10 is discharged through the fresh water outlet system 10 through the fresh water outlet system 10;

Step 4: Open the water injection hole 11, inject the second colored brine through the water injection hole 11 into the part with the color of the first colored brine in the second cavity 4, and at the same time, inject the fresh water The fresh water is discharged into the third cavity 5 through the fresh water inlet system 9. In the process, the color distribution of the water in the second cavity 4 is observed or photographed. The water at the height of the connection between the salt water outlet system 8 and the first cavity 3 corresponding to the main box 1 is discharged through the salt water outlet system 8, and the third cavity 5 exceeds the fresh water outlet system 10 The water at the height of the connection with the third cavity 5 corresponding to the main box body 1 is discharged through the fresh water outlet system 10;

Step 5: According to the color distribution obtained in Step 3 and Step 4, a circulation pattern driven by uniform seawater density under steady-state conditions in the simulated littoral phreatic aquifer is obtained.

As a further solution of this embodiment, the dyeing process of the brine is to add dyes to the brine to obtain the colored brine.

work process:

Three different types of water were used in the experiment: (1) colorless fresh water (tap water and distilled water are acceptable); (2) red salt water (density of 1100kg m-3); (3) green salt water (density of 1100kg· m-3). Dissolve NaCl in tap water before the experiment, add 10g of red food coloring or fluorescent yellow dye to 20L of the solution to form red and green tracers, respectively.

The circulating flow field was traced by two tracer experimental methods, front source and point source. In both solutions, the saline solution of one color was replaced by the saline solution of the other color. To prevent buoyancy or density difference effects, keep their densities consistent.

Former source method:

In the first experiment, the steady-state conditions of the salty-fresh water interface were obtained by the front-source tracing method, and then the entire salty-water boundary was instantly replaced with a different-colored salty-water solution to form a salty-water end of another color. While maintaining conditions, push forward within the saltwater wedge. Soon after, the green tracer seeps into the aquifer, displacing the red tracer, pushing it toward the brackish-water interface. In the experiment, the green tracer penetrated inland and the red tracer was replaced by the green tracer, creating a green front that was not perpendicular to the lower boundary within the red saline wedge. This front does not reach the colorless subsurface area of fresh water, and a narrow red tracer band develops along the brackish water interface. This narrow band of tracer is the last to wash out, even after the toe region of the wedge (where the wedge fades out). At the end of the experiment, the entire red tracer was washed out of the elongated strip and the saline wedge was completely occupied by the green tracer. This method can be used to detect brine circulation flow. The advantage of this method compared to the point source method is that it prevents the effects of lateral diffusion/scattering and can measure flow velocity over a larger range.

Specific steps are as follows,

Step 1: Prepare transparent fresh water, dissolve NaCl in tap water to obtain brine with a density of 1100kg m-3, add 10g of red food coloring to 20L of brine to obtain a red tracer, the first colored brine, add 10g Add fluorescent yellow dye to 20L of saline to obtain green tracer, which is the second colored saline;

Step 2: first place the first colored salt water in the salt water inlet tank, pump it into the first cavity 3 through the salt water pump, and at the same time, place the fresh water in the fresh water inlet tank, pumped into the third cavity 5 by a fresh water pump;

Step 3: Both the first colored brine in the first cavity 3 and the fresh water in the third cavity 5 flow into the second cavity 4, and the first colored brine Contact with the fresh water in the second cavity 4, merge and form a stable state, in the process, observe or take pictures of the color distribution of the water in the second cavity 4, the first cavity 3 The water that exceeds the height of the connection between the pipe in the salt water outlet system 8 and the first cavity 3 corresponding to the main tank 1 is discharged to the salt water collection through the pipe in the salt water outlet system 8 In the tank, the water in the third cavity 5 that exceeds the height of the connection between the pipe in the fresh water outlet system 10 and the corresponding main tank 1 of the third cavity 5 is discharged through the tube in the fresh water outlet system 10 into the fresh water collection tank;

Step 4: Change the first salt water in the salt water inlet tank to second salt water, and the second colored salt water is pumped into the first cavity 3 by the salt water pump to replace the first colored salt water At the same time, the fresh water is still discharged into the third cavity 5 through the fresh water inlet system 9, and in the process, the color distribution of the water in the second cavity 4 is observed or photographed, and the The water in the first cavity 3 that exceeds the height of the connection between the pipe in the salt water outlet system 8 and the first cavity 3 corresponding to the main tank 1 is discharged through the pipe in the salt water outlet system 8 to In the salt water collection tank, the water in the third cavity 5 that exceeds the height of the connection between the pipe in the fresh water outlet system 10 and the corresponding main tank 1 of the third cavity 5 passes through the fresh water outlet system The pipe in 10 is discharged into the fresh water collection tank;

Step 5: According to the color migration and distribution recorded in Step 3 and Step 4, explore the diffusion cycle driven by density flow during the invasion process, simulating the density between fresh groundwater and salt water from the ocean in the natural state Poor-induced saline-water displacement processes, identification of seafloor groundwater discharge, and circulation patterns driven by uniform seawater density under steady-state conditions in simulated littoral phreatic aquifers.

Point source method:

In the second experiment, using the point source method, a red saltwater tracer was injected at a known location (which would form a red circle) at a specific time, and its spatial and temporal distribution was recorded, which was used to track flow patterns above and below the brackish-fresh water interface . In this experiment, a red tracer was injected into a green saltwater wedge, which produced a red plume of exactly the same density as the green tracer wedge. The tracers are then transported horizontally farther inland. The total volume of the red tracer used is 25mL, injected for 1min, and the coordinates of the injection point are: as shown in Figure 1, with the lower left corner of the sand body as the origin, the horizontal direction to the right is the x-axis direction, and the vertical upward direction is the z-axis direction x = 6cm , z=6.5cm. This position can be changed, that is, injection holes at other points can be selected to observe changes in brackish and fresh water, which is the circulation effect of brackish and fresh water at different locations. Shortly before approaching the brackish water interface (color changes from green to colorless), the red circle has upward diffuse flow and a long red tracer band appears along the brackish water interface. The strip and circle boundaries are surrounded by green tracer in the lower part of the wedge and diluted green tracer in the upper part of the wedge along the brackish-water interface. Over time, the line continues to move upwards, at the expense of the red circle, which gets smaller in size and eventually disappears.

Specific steps are as follows,

Step 1: Prepare transparent fresh water, dissolve NaCl in tap water to obtain brine with a density of 1100kg m-3, add 10g of fluorescent yellow dye to 20L of brine to obtain a green tracer, the first colored brine, add 10g of red Add food coloring to 20L of brine to obtain red tracer, i.e. the second colored brine;

Step 2: first place the first colored salt water in the salt water inlet tank, pump it into the first cavity 3 through the salt water pump, and at the same time, place the fresh water in the fresh water inlet tank, pass The fresh water pump is pumped into the third cavity 5;

Step 3: Both the first salt water in the first cavity 3 and the fresh water in the third cavity 5 flow into the second cavity 4, and the first salt water and the fresh water The fresh water contacts, merges and forms a stable state in the second cavity 4. During this process, the pipes in the first cavity 3 beyond the salt water outlet system 8 and the first cavity 3 The water corresponding to the height of the connection point of the main tank 1 is discharged into the salt water collection tank through the pipe in the salt water outlet system 8, and the inside of the third cavity 5 exceeds the fresh water outlet system 10 The water at the height of the connection between the pipe and the third cavity 5 corresponding to the main box 1 is discharged into the fresh water collection tank through the pipe in the fresh water outlet system 10;

Step 4: Open the water injection hole 11, inject the second colored brine through the water injection hole 11 into the part with the color of the first colored brine in the second cavity 4, and at the same time, inject the fresh water The fresh water is discharged into the third cavity 5 through the fresh water inlet system 9. In the process, the color distribution of the water in the second cavity 4 is observed or photographed. The water at the height of the connection between the pipe in the salt water outlet system 8 and the first cavity 3 corresponding to the main tank 1 is discharged into the salt water collection tank through the pipe in the salt water outlet system 8, The water in the third cavity 5 that exceeds the height of the connection between the pipe in the fresh water outlet system 10 and the corresponding main box 1 of the third cavity 5 is discharged to the fresh water collection tank;

Step 5: According to the color migration and distribution recorded in Step 3 and Step 4, explore the diffusion cycle driven by density flow during the invasion process, simulating the density between fresh groundwater and salt water from the ocean in the natural state Poor-induced saline-water displacement processes, identification of seafloor groundwater discharge, and circulation patterns driven by uniform seawater density under steady-state conditions in simulated littoral phreatic aquifers.

The "pump" used in the present invention is a peristaltic pump in the prior art unless otherwise specified.

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inner", "Outer", "Clockwise", "Counterclockwise", "Axial", The orientation or positional relationship indicated by "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying the referred device or element Must be in a particular orientation, be constructed in a particular orientation, and operate in a particular orientation, and therefore should not be construed as limiting the invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrated; it may be mechanically connected or electrically connected; it may be directly connected or indirectly connected through an intermediary, and it may be the internal communication of two components or the interaction relationship between two components, unless otherwise specified limit. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

In the present invention, unless otherwise clearly specified and limited, the first feature may be in direct contact with the first feature or the first and second feature may be in direct contact with the second feature through an intermediary. touch. Moreover, "above", "above" and "above" the first feature on the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. "Below", "beneath" and "beneath" the first feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is less horizontally than the second feature.

In the description of this specification, descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (10)

1. the circulation simulator that uniform density drives in coastal aquifer, which is characterized in that including main body case (1), the master It is fixed in cabinet (1) that there are two the permeable baffle for being vertically arranged and having several permeable holes, the respectively first permeable baffles (201) it is set relatively with the second permeable baffle (202), the first permeable baffle (201) and the second permeable baffle (202) It sets, the main box (1) is divided into the first cavity (3), the second cavity (4) and third cavity (5), institute by two permeable baffles It states the first cavity (3), second cavity (4) and the third cavity (5) to be sequentially communicated, second cavity (4) is provided with Porous media (6)；

It further include freshwater system and salt water system, the salt water system includes the salt water being connected to respectively with first cavity (3) Water inlet system (7) and salt water outlet system (8), the freshwater system include the fresh water being connected to respectively with the third cavity (5) Water inlet system (9) and fresh water outlet system (10)；

The main box (1) is made of transparent material；

There is transparent fresh water in the fresh water water inlet system (9), has colored salt water in the salt water water inlet system (7).

2. the circulation simulator that uniform density drives in coastal aquifer according to claim 1, which is characterized in that described Salt water water inlet system (7) includes salt water water inlet tank (12) and salt water pump (13), and salt water water inlet tank (12) and the salt water pump (13) it is connected by pipe, the salt water pump (13) is connected with first cavity (3) by pipe, and the salt water pump (13) will Liquid in salt water water inlet tank (12) is pumped into first cavity (3)；The salt water outlet system (8) includes that salt water is received Collect tank (14), the salt water collecting tank (14) is connected by pipe with first cavity (3), and the salt water collecting tank (14) is used In the liquid for collecting outflow in first cavity (3)；

The fresh water water inlet system (9) includes fresh water water inlet tank (15) and fresh water pump (16), and the fresh water is intake tank (15) and institute It states fresh water pump (16) to be connected, the fresh water pump (16) is connected with the third cavity (5), and the fresh water pump (16) will be described Water in fresh water water inlet tank (15) is pumped into the third cavity (5)；The fresh water outlet system (10) includes fresh water collecting tank (17), the fresh water collecting tank (17) is connected by pipe with the third cavity (5), and the fresh water collecting tank (17) is for receiving Collect the liquid flowed out in the third cavity (5).

3. the circulation simulator that uniform density drives in coastal aquifer according to claim 1, which is characterized in that described Main box (1) upper end is opening, and the salt water water inlet system (7) passes through corresponding main box (1) side of first cavity (3) Hole on wall is connected with first cavity (3), and the salt water outlet system (8) passes through corresponding with the first cavity (3) Hole on main box (1) side wall is connected with first cavity (3)；The fresh water water inlet system (9) passes through described spacious Mouth is connected with the third cavity (5), and the fresh water outlet system (10) passes through the master corresponding with third cavity (5) Hole on cabinet (1) side wall is connected with the third cavity (5).

4. the circulation simulator that uniform density drives in coastal aquifer according to claim 3, which is characterized in that described Main box (1) is cuboid, a length of 1m of the main box (1), width 0.05m, a height of 0.5m.

5. the circulation simulator that uniform density drives in coastal aquifer according to claim 1, which is characterized in that described Porous media (6) one end is contacted with the described first permeable baffle (201), and porous media (6) other end is saturating with described second Water baffle (202) contact.

6. the circulation simulator that uniform density drives in coastal aquifer according to claim 5, which is characterized in that described Porous media (6) is silica sand particles, and the silica sand particles diameter range is at 500-850 μm.

7. the circulation simulator that uniform density drives into any one of 6 coastal aquifers according to claim 1, feature It is, corresponding main box (1) side of second cavity (4) has water injection hole (11), in the water injection hole (11) Outside is removably connected with the sealing cover for sealing the water injection hole (11).

8. a kind of circulation simulator that uniform density drives in coastal aquifer as described in any one of claim 1 to 6 makes With method, which is characterized in that include the following steps,

Step 1: preparing transparent fresh water, prepare the dyeing that the identical salt water of concentration carries out different colours, obtain the first colored salt Water and the second colored salt water；

Step 2: being first discharged into the described first colored salt water in first cavity (3) by the salt water water inlet system (7), together When, the fresh water is discharged into the third cavity (5) by the fresh water water inlet system (9)；

Step 3: the fresh water in the described first colored salt water and the third cavity (5) in first cavity (3) is equal It flows into second cavity (4), the first colored salt water and the fresh water contact, fusion in second cavity (4) And stable state is formed, in the process, the distribution of color situation for the interior water of second cavity (4) of observing or take pictures is described Exceed the salt water outlet system (8) main box (1) connectivity part corresponding with the first cavity (3) in first cavity (3) The water of height is discharged by the salt water outlet system (8), and the fresh water outlet system (10) is exceeded in the third cavity (5) The water of main box (1) connectivity part height corresponding with third cavity (5) is discharged by the fresh water outlet system (10)；

Step 4: the described second colored salt water being discharged into first cavity (3) by the salt water water inlet system (7) and is replaced The first colored salt water, meanwhile, the fresh water is discharged into the third cavity (5), In by the fresh water water inlet system (9) During this, the distribution of color situation for the interior water of second cavity (4) of observing or take pictures, first cavity (3) is interior to exceed The water of salt water outlet system (8) main box (1) the connectivity part height corresponding with the first cavity (3) passes through described salty Water outlet system (8) discharge, the third cavity (5) is interior to exceed the fresh water outlet system (10) and the third cavity (5) The water of corresponding main box (1) connectivity part height is discharged by the fresh water outlet system (10)；

Step 5: according to the color migration recorded in the step 3 and step 4 and distribution situation, it is aqueous to obtain simulation strand diving In layer under limit uniform sea density-driven circulation patterns.

9. a kind of application method for the circulation simulator that uniform density drives in coastal aquifer as claimed in claim 7, It is characterized in that, includes the following steps,

Step 1: preparing fresh water, prepare the dyeing that the identical salt water of concentration carries out different colours, obtain the first colored salt water and the Two colored salt water；

Step 2: being first discharged into the described first colored salt water in first cavity (3) by the salt water water inlet system (7), together When, the fresh water is discharged into the third cavity (5) by the fresh water water inlet system (9)；

Step 3: the fresh water in the described first colored salt water and the third cavity (5) in first cavity (3) is equal It flows into second cavity (4), the first colored salt water and the fresh water contact, fusion in second cavity (4) And stable state is formed, in the process, the distribution of color situation for the interior water of second cavity (4) of observing or take pictures is described Exceed the salt water outlet system (8) main box (1) connectivity part corresponding with the first cavity (3) in first cavity (3) The water of height is discharged by the salt water outlet system (8), and the fresh water outlet system (10) is exceeded in the third cavity (5) The water of main box (1) connectivity part height corresponding with third cavity (5) is discharged by the fresh water outlet system (10)；

Step 4: opening the water injection hole (11), the described second colored salt water is passed through into the water injection hole (11) injection described second The part of the first colored salt water color is had in cavity (4), meanwhile, the fresh water is arranged by the fresh water water inlet system (9) Enter the third cavity (5), in the process, the distribution of color situation for the interior water of second cavity (4) of observing or take pictures, institute It states in the first cavity (3) beyond the salt water outlet system (8) main box (1) connection corresponding with the first cavity (3) The water for locating height is discharged by the salt water outlet system (8), and the fresh water outlet system is exceeded in the third cavity (5) (10) water of main box (1) connectivity part height corresponding with third cavity (5) is discharged by the fresh water outlet system (10)；

Step 5: according to the color migration recorded in the step 3 and step 4 and distribution situation, it is aqueous to obtain simulation strand diving In layer under limit uniform sea density-driven circulation patterns.

10. the circulation simulator driven according to uniform density in coastal aquifer described in claim 7-8, which is characterized in that The dyeing course of the salt water is that dyestuff is added into the salt water to obtain the colored salt water.