Karst water system physical experiment model based on double-conduit structure

Abstract

The invention relates to the technical field of karst hydrogeology, and discloses a karst water system physical experiment model based on a double-conduit structure, the karst water system physical experiment model comprises a double-conduit structure, a water supply module and a data acquisition module, the double-conduit structure comprises an inlet section, a double-conduit section and an outlet section, the inlet section is a single-channel part, and the double-conduit section is a single-channel part; the double-guide-pipe section comprises two guide pipes which are connected in parallel and are different in length, the included angle between the guide pipes is adjustable, and the water outlet end of the double-guide-pipe section is connected with the outlet section. The double-catheter design with an adjustable structure is adopted, the length and the connecting angle of the two catheters can be flexibly adjusted, and the inner diameters of the catheters are allowed to be adjusted according to experiment requirements; the experimental model provided by the scheme is flexible in structure, the model can simulate flow paths of various actual karst systems through combination of different lengths and angles, and the influence of different geometric structures on water flow and solute transmission can be conveniently researched.

Description

Technical Field

[0001] The invention relates to the technical field of karst hydrogeology, and in particular to a physical experimental model of a karst water system based on a double-conduit structure. Background Art

[0002] In karst hydrogeology, tracer tests are an important method for studying water flow paths and solute transport characteristics in karst aquifers. This method was originally developed for investigating karst aquifers and is still widely used in this field. Tracer tests can be used to obtain groundwater flow trajectories and breakthrough curves (BTCs), which can be used to estimate the parameters of transport models. However, due to the strong heterogeneity of karst aquifers, BTCs often exhibit asymmetric characteristics with long tails or multiple peaks, which poses a challenge to the traditional advection-diffusion equation (ADE) model. In order to more accurately characterize the tail effect, researchers have introduced other transport models, such as the moving-stationary model (MIM), the dual permeability model (MRAD), and the continuous-time random walk (CTRW) theory, to better simulate the solute transport characteristics in karst aquifers.

[0003] Dual-peaked BTCs in karst aquifers are usually caused by pools (underground lakes) or multiple flow paths in the main channel. In addition, experimental studies at different laboratory scales have also found that the presence of auxiliary channels or ponds can lead to an extended tail of the BTC. However, these studies have not yet clearly demonstrated whether the geometric properties of the karst conduits can be inferred from the BTC shape.

[0004] Defects and shortcomings of the existing technology:

[0005] Traditional models cannot accurately characterize the complex characteristics of BTC:

[0006] The traditional advection-diffusion equation (ADE) model performs poorly in dealing with breakthrough curves of karst aquifers, especially when there are tail extensions or multiple peaks. The heterogeneity of karst aquifers leads to complex and variable fluid migration characteristics, and a single ADE model is difficult to capture these complex behaviors. Although existing studies have introduced more complex models (such as MIM, MRAD, CTRW, etc.), these models have high computational complexity and still have certain limitations in experimental verification.

[0007] The existing technology lacks research on the impact of dual-catheter geometry:

[0008] The dual-conduit geometry in karst water systems may have a significant impact on the morphology of BTC. Although previous studies have suggested that the presence of multiple flow paths or ponds may cause bimodal BTC, these studies are mostly conceptual models and lack systematic experimental analysis of BTC under dual-conduit geometry. Therefore, the existing technology still has a gap in understanding the relationship between conduit geometry and breakthrough curve morphology, and cannot provide sufficient reference for tracer analysis of actual karst water systems.

[0009] The current experimental scale is limited:

[0010] Most of the existing experiments are single-channel or small-scale experiments, which are difficult to fully simulate the complex geometric structure of the actual karst aquifer. The applicability of the experimental results is limited and it is difficult to generalize to a wider range of karst landform scenarios. In addition, the conduit structure in the experiment is usually too simple to reflect the complex geometric characteristics of the actual karst system, resulting in the lack of pertinence of the experimental results in practical applications.

[0011] The properties of the karst conduits cannot be inferred from the BTC shape:

[0012] Although the tracer test can generate breakthrough curves, there is no effective method to directly infer the geometric properties of karst conduits from the BTC shape. The influence of conduit geometry (such as double conduit morphology, conduit spacing, etc.) on water flow and solute transport is relatively complex, and existing research lacks systematic research on the quantitative relationship between geometric properties and BTC shape.

[0013] Therefore, in order to better understand the effect of double-conduit geometry on BTC morphology, this paper proposes a tracer test model of a karst water system with double-conduit geometry and analyzes the relationship between conduit geometry and solute transport characteristics through experimentally generated BTC shapes. Summary of the invention

[0014] In order to solve the technical problems raised in the background technology, the present invention provides a karst water system physical experimental model based on a double-conduit structure.

[0015] The present invention is implemented by the following technical scheme: a physical experimental model of a karst water system based on a double-conduit structure, comprising a double-conduit structure, a water supply module and a data acquisition module, wherein:

[0016] The double-duct structure includes an inlet section, a double-duct section, and an outlet section. The inlet section is a single-channel portion for introducing water flow into the double-duct section. The double-duct section includes two parallel-connected ducts of different lengths, and the angle between the ducts is adjustable. The water outlet end of the double-duct section is connected to the outlet section.

[0017] The water supply module includes a peristaltic pump and a three-way joint. The peristaltic pump is connected in series to the outlet section and is used to provide a water source with a constant flow rate. One port of the three-way joint is connected to the inlet section, and the other two joints of the three-way joint are used to connect to a pure water source and a salt water source respectively.

[0018] The data acquisition module is used to measure liquid flow rate, tracer concentration and store flow rate and concentration data.

[0019] Preferably, the inner diameter, length and angle of the catheter are all adjustable, and the catheter is made of a flexible silicone tube.

[0020] Preferably, the experimental model is installed on a horizontal platform to ensure that the experimental process is not affected by gravity, so as to focus on the effects of geometric structure and flow rate on tracer transport.

[0021] Preferably, the liquid flow is measured using an electronic scale, which is used to receive the liquid discharged by the peristaltic pump to measure the flow in real time.

[0022] Preferably, the tracer concentration is measured by a conductivity meter. Specifically, a conductivity meter is installed at the outlet section to record the concentration change of the tracer to obtain the transmission process data of the tracer in the water flow.

[0023] Preferably, the electronic scale and the conductivity meter are electrically connected to a data recorder to achieve automated data collection, and the sampling frequency can be adjusted according to experimental requirements to achieve continuous monitoring of concentration changes.

[0024] Preferably, the platform comprises a mounting plate, and the mounting plate is used to fix the double-conduit structure and the three-way joint.

[0025] Preferably, adhesive tape is used to fix the conduits in the double-conduit structure and the three-way connector on the mounting plate.

[0026] Preferably, a magnetic layer is provided on the surface of the mounting plate, and the conduits in the double-conduit structure are fixed by a card block magnetically adsorbed to the mounting plate. A notch is provided on the mounting plate, and an adjustment mechanism for adjusting the height of the three-way joint is installed at the notch.

[0027] Preferably, the condition mechanism comprises a bottom plate fixed in the notch, a convex plate fixed to the three-way joint, a through hole is formed on the convex plate, a screw rod movably passing through the through hole is fixed on the bottom plate, a columnar spring is installed on the outside of the screw rod between the convex plate and the bottom plate, a clamping nut is spirally installed on the top end of the screw rod, and the height of the three-way joint is adjusted by rotating the clamping nut;

[0028] The clamping block is provided with a clamping slot for the catheter to pass through.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The existing experimental models have complex structures and are difficult to adjust. The length and angle of the catheter are fixed, resulting in a lack of flexibility in the experimental design. It is difficult to adjust the geometric parameters of the catheter to simulate different karst conditions. The cost is high and the experimental consumables are many. In addition, the traditional model uses rigid materials, which has high manufacturing costs and is difficult to reuse. In addition, due to the complex design, the experimental process requires more consumables. The data acquisition accuracy is limited and the operation is cumbersome.

[0031] The traditional tracer test model has certain limitations in data collection, especially the lack of accurate flow and concentration monitoring methods, which leads to low accuracy of experimental results. At the same time, the traditional system operation is cumbersome and requires a lot of manual intervention.

[0032] The present invention adopts a double-conduit design with an adjustable structure, which can flexibly adjust the length and connection angle of the two conduits, and allows the inner diameter of the conduit to be adjusted according to experimental requirements; the flexibility of the experimental model structure proposed in this scheme: the combination of different lengths and angles enables the model to simulate the flow paths of various actual karst systems, which is convenient for studying the effects of different geometric structures on water flow and solute transport. The adjustable double-conduit structure can support multiple experimental combination settings (such as different conduit length ratios, total conduit lengths and connection angles), thereby reducing the number of replacements of the experimental device and greatly improving the flexibility of the experimental design. In addition, the experimental operator can quickly change the conduit parameters according to the research requirements, saving adjustment time and improving work efficiency.

[0033] The double-duct structure proposed by the present invention adopts a flexible silicone tube, which reduces material costs, and the flexible silicone tube has good flexibility and sealing. Silicone materials are cheaper and easier to process than traditional rigid materials, reducing manufacturing and replacement costs.

[0034] The flexible pipe structure proposed in this scheme makes the experimental device simpler in design and can be more conveniently assembled and disassembled. The durability and reusability of the parts are greatly improved. In addition, the silicone tube is corrosion-resistant, easy to clean and reusable, which reduces the use of experimental consumables.

[0035] The present invention introduces an automated data acquisition system to improve experimental accuracy and efficiency. By configuring a high-precision conductivity meter and an electronic scale at the outlet and realizing automated data acquisition through a data recorder, the data has high accuracy and can record tracer concentration and flow changes at a high frequency in a short time, avoiding errors caused by manual operation, improving the accuracy of experimental results, reducing the burden on operators, and ensuring the continuity and integrity of data acquisition. Automatic data recording greatly reduces the time for manual recording and monitoring, allowing multiple experiments to be repeated to obtain more reliable average data, thereby further improving experimental efficiency.

[0036] The experimental model proposed in the present invention is installed on a horizontal platform to ensure that it is not affected by gravity during the experiment; in addition, the adjustable design of the structure minimizes the impact of external environmental factors on the experiment. The horizontal installation reduces the impact of gravity on the flow path, can more accurately simulate the natural flow conditions of the karst system, and make the experimental results more stable and reliable. The horizontal installation of the structure ensures the stability of the water flow, eliminates unnecessary sources of error, and further improves the accuracy of the experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The schematic diagram of the physical experimental model of the karst water system proposed by the present invention;

[0038] Figure 2 This is a schematic diagram of the installation structure of the installation plate and the conduit in Example 3 of the present invention;

[0039] Figure 3 For the present invention Figure 2 Side view of the middle structure;

[0040] Figure 4 A three-dimensional diagram of a card block according to Embodiment 3 of the present invention;

[0041] Figure 5 This is a real shot of the conduit and the mounting plate being fixed by adhesive tape in Example 1-2 of the present invention;

[0042] Figure 6 For the present invention Figure 5 Actual photo after catheter replacement;

[0043] Figure 7 This is a real shot of the double-duct structure of the present invention when the angle between the two ducts is greater than 90 degrees.

[0044] Description of main symbols:

[0045] Computer 1, electronic balance 2, peristaltic pump 3, conductivity meter 4, double-tube structure 5, three-way connector 6, pure water source 7, salt water source 8, mounting plate 10, block 11, slot 1101, notch 12, long tube 501, short tube 502, bottom plate 13, columnar spring 14, clamping nut 15, screw 16. DETAILED DESCRIPTION

[0046] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0047] Example 1: Reference Figure 1,This scheme proposes a physical experimental model of karst water system based on double-conduit structure, including double-conduit structure, water supply module and data acquisition module, among which:

[0048] The double-duct structure includes an inlet section, a double-duct section, and an outlet section. The inlet section is a single-channel portion for introducing water flow into the double-duct section. The double-duct section includes two parallel-connected ducts of different lengths, and the angle between the ducts is adjustable. The water outlet end of the double-duct section is connected to the outlet section.

[0049] The water supply module includes a peristaltic pump and a three-way joint. The peristaltic pump is connected in series to the outlet section and is used to provide a water source with a constant flow rate. One port of the three-way joint is connected to the inlet section, and the other two joints of the three-way joint are used to connect to a pure water source and a salt water source respectively.

[0050] The data acquisition module is used to measure liquid flow rate, tracer concentration and store flow rate and concentration data.

[0051] The inner diameter, length and angle of the catheter are all adjustable, and the catheter adopts a flexible silicone tube.

[0052] The experimental model was installed on a horizontal platform to ensure that the experimental process was not affected by gravity, so as to focus on the effects of geometry and flow rate on tracer transport.

[0053] The liquid flow is measured by an electronic scale, which is used to receive the liquid discharged by the peristaltic pump to measure the flow in real time.

[0054] The tracer concentration is measured by a conductivity meter. Specifically, a conductivity meter is installed at the outlet section to record the concentration change of the tracer to obtain the transmission process data of the tracer in the water flow.

[0055] The electronic scale and the conductivity meter are electrically connected to a data recorder to realize automatic data collection, and the sampling frequency can be adjusted according to experimental requirements to realize continuous monitoring of concentration changes.

[0056] Embodiment 2:

[0057] This proposal proposes the construction steps and usage methods of a physical experimental model of a karst water system based on a double-conduit structure.

[0058] The main components are as follows:

[0059] Double tube structure:

[0060] The experimental pipeline adopts flexible silicone tube, and the inner diameter of the pipeline can be adjusted according to the experimental needs to meet different water flow control accuracy requirements.

[0061] Inlet section: The inlet section is a single-channel part used to introduce water flow into the system to ensure stable flow and easy control.

[0062] Double-duct section: After the water flow enters the double-duct section, it is divided into two duct channels, forming a double-duct structure. The duct length and connection angle of this section can be adjusted. The lengths of the shorter duct and the longer duct are denoted as l1 and l2, respectively, and the connection angles of the ducts are θ1 and θ2, respectively. By adjusting these parameter combinations, the effects of different geometric structures on the water flow path and solute transport are studied.

[0063] Outlet section: The water flow after the double conduit section rejoins into a single channel in the outlet section, which is convenient for flow and concentration measurement.

[0064] Reference Figure 5-Figure 7 The platform includes a mounting plate 10 , and the mounting plate 10 is used to fix the double-conduit structure and the three-way joint 6 .

[0065] In this solution, the conduits in the double-conduit structure and the three-way connector 6 are fixed to the mounting plate 1 by using adhesive tape.

[0066] Reference Figure 2-Figure 4 Embodiment 3: A magnetic layer is provided on the surface of the mounting plate 10, and the catheters in the double-catheter structure (including the long catheter 501 and the short catheter 502) are fixed by a block 11 that is magnetically adsorbed to the mounting plate 10, and a notch 12 is opened on the mounting plate 10, and an adjustment mechanism for adjusting the height of the three-way joint 6 is installed at the notch 12.

[0067] The condition mechanism comprises a bottom plate 12 fixed in the notch 12, a convex plate fixed to the three-way joint 6, a through hole is formed on the convex plate, a screw 16 movably passing through the through hole is fixed on the bottom plate 12, a columnar spring 14 is installed on the outside of the screw between the convex plate and the bottom plate 13, a clamping nut 15 is spirally installed on the top of the screw 16, and the height of the three-way joint 6 is adjusted by rotating the clamping nut 15;

[0068] The block 11 is provided with a slot 1101 for the catheter to pass through.

[0069] Experimental platform:

[0070] The experimental model proposed in this scheme is installed on a horizontal platform to ensure that the entire experimental process is not affected by gravity, so as to focus on the effects of geometric structure and flow rate on tracer transport.

[0071] Water supply module:

[0072] Use a peristaltic pump (such as Lead Fluid) to provide a constant flow of water. This pump can accurately set the flow rate to ensure that the flow rate remains constant during the experiment.

[0073] A three-way joint is installed at the inlet section to connect the pure water and brine supply systems respectively. Pure water is used for basic control of the system flow, and brine (tracer) can be briefly injected during the experiment to simulate the instantaneous diffusion behavior of the solute.

[0074] Data acquisition module:

[0075] Flow measurement: Equipped with an electronic scale to monitor the flow in real time and ensure accurate control of the flow.

[0076] Concentration measurement: A conductivity meter is installed at the outlet to record the concentration changes of the tracer and obtain the data of the tracer's transport process in the water flow.

[0077] Data recording equipment: electronic scales and conductivity meters are connected to data loggers to achieve automated data collection. The sampling frequency can be adjusted according to experimental requirements to achieve continuous monitoring of concentration changes.

[0078] The specific experimental operation steps are as follows:

[0079] Step 1: Model installation and setup:

[0080] Step 1.1. Fix the model on a horizontal platform and ensure that all connections are leak-free.

[0081] Step 1.2: According to the experimental requirements, adjust the inner diameter, catheter length (l1 and l2) and connection angle (θ1 and θ2) of the double catheter segment.

[0082] Step 2: Water injection and system stabilization: Start the peristaltic pump and introduce pure water at a constant flow rate to ensure that the system water flow reaches a stable state.

[0083] Step 3: Tracer injection: Use a three-way connector to switch to the saline supply system and perform a short pulse injection to achieve instantaneous entry of the tracer. After the tracer is injected, resume the pure water supply to observe the diffusion behavior of the solute in the system.

[0084] Step 4: Data collection:

[0085] Step 4.1. Automatically record the tracer concentration change at the outlet until the concentration returns to the background value.

[0086] Step 4.2: Repeat each set of experiments multiple times to ensure the accuracy and reliability of the data.

[0087] When conducting the experiment in this scheme, the experimental group is set up as follows:

[0088] This experiment designed multiple experimental groups to adjust the inner diameter, the length of the conduit and the connection angle to explore the effects of these parameters on water flow and solute transport characteristics. The specific design is as follows:

[0089] 1. Effect of catheter length ratio

[0090] The length ratio of the two tubes in the double tube was adjusted and different tube length combinations were set to study the effect of the tube length ratio on the water flow path and tracer diffusion.

[0091] 2. Changes in total catheter length

[0092] Keeping the conduit length ratio constant, the absolute lengths of the two conduits were adjusted to observe the effect of the total conduit length on the water flow transport behavior.

[0093] 3. Changes in catheter connection angle

[0094] The angle combination of θ1 and θ2 was adjusted to study the effect of the connection angle on the flow path and tracer migration.

[0095] Through these different experimental combinations, we can systematically analyze the water flow and solute transport behaviors in the double-duct structure.

[0096] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A physical experimental model of karst water system based on a double-conduit structure, characterized in that: It includes a double-duct structure, a water supply module and a data acquisition module, wherein: The double-duct structure includes an inlet section, a double-duct section, and an outlet section. The inlet section is a single-channel portion for introducing water flow into the double-duct section. The double-duct section includes two parallel-connected ducts of different lengths, and the angle between the ducts is adjustable. The water outlet end of the double-duct section is connected to the outlet section. The water supply module includes a peristaltic pump and a three-way joint. The peristaltic pump is connected in series to the outlet section and is used to provide a water source with a constant flow rate. One port of the three-way joint is connected to the inlet section, and the other two joints of the three-way joint are used to connect to a pure water source and a salt water source respectively. The data acquisition module is used to measure liquid flow rate, tracer concentration and store flow rate and concentration data.

2. A karst water system physical experimental model based on a double-conduit structure as claimed in claim 1, characterized in that: The inner diameter, length and angle of the catheter are all adjustable, and the catheter adopts a flexible silicone tube.

3. A karst water system physical experimental model based on a double-conduit structure as claimed in claim 1, characterized in that: The experimental model was installed on a horizontal platform to ensure that the experimental process was not affected by gravity, so as to focus on the effects of geometry and flow rate on tracer transport.

4. The physical experimental model of karst water system based on double conduit structure according to claim 1, characterized in that: The liquid flow is measured by an electronic scale, which is used to receive the liquid discharged by the peristaltic pump to measure the flow in real time.

5. The physical experimental model of karst water system based on double conduit structure as claimed in claim 1, characterized in that: The tracer concentration is measured by a conductivity meter. Specifically, a conductivity meter is installed at the outlet section to record the concentration change of the tracer to obtain the transmission process data of the tracer in the water flow.

6. The physical experimental model of karst water system based on double conduit structure according to claim 1, characterized in that: The electronic scale and the conductivity meter are electrically connected to a data recorder to realize automatic data collection, and the sampling frequency can be adjusted according to experimental requirements to realize continuous monitoring of concentration changes.

7. The physical experimental model of karst water system based on double conduit structure according to claim 1, characterized in that: The platform comprises a mounting plate, and the mounting plate is used for fixing the double-pipe structure and the three-way joint.

8. A karst water system physical experimental model based on a double-conduit structure as claimed in claim 7, characterized in that: Use tape to secure the conduits in the double conduit structure and the tee connector to the mounting plate.

9. A karst water system physical experimental model based on a double-conduit structure as claimed in claim 8, characterized in that: The surface of the mounting plate is provided with a magnetic layer, and the conduits in the double-conduit structure are fixed by a clamping block magnetically adsorbed to the mounting plate. A notch is provided on the mounting plate, and an adjusting mechanism for adjusting the height of the three-way joint is installed at the notch.

10. A karst water system physical experimental model based on a double-conduit structure as claimed in claim 9, characterized in that: The condition mechanism comprises a bottom plate fixed in the notch, a convex plate fixed to the three-way joint, a through hole is formed on the convex plate, a screw rod movably passing through the through hole is fixed on the bottom plate, a columnar spring is installed on the outside of the screw rod between the convex plate and the bottom plate, a compression nut is spirally installed on the top of the screw rod, and the height of the three-way joint is adjusted by rotating the compression nut; The clamping block is provided with a clamping slot for the catheter to pass through.

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