Method for determining porous medium resistance coefficient of water permeable building in CFD numerical simulation

Abstract

This invention discloses a method for determining the resistance coefficient of porous media in permeable structures during CFD numerical simulation. The method includes: conducting a series of physical model tests to measure the upstream and downstream water depths and velocities of the permeable structure under given inflow conditions, obtaining the hydraulic characteristics of the permeable structure under different geometric scales; inverting physical model tests at different scales through CFD numerical simulation, where the permeable structure is simulated using porous media in the CFD model, and the resistance of the porous media to the water flow is calculated using the Forchheimer form of the resistance formula, obtaining the resistance characteristics of the permeable structure; establishing the mathematical relationship between the viscous resistance coefficient and the inertial resistance coefficient and the geometric scale, and determining the viscous resistance coefficient and inertial resistance coefficient at the prototype scale and other unknown scales. This method improves the accuracy of the resistance coefficient of porous media in permeable structures and is applicable to submerged and outlet permeable structures composed of various porous or open structures.

Description

Technical Field

[0001] This invention relates to the field of numerical simulation technology for water conservancy, water transport and marine engineering, and in particular to a method for determining the resistance coefficient of porous media in permeable structures in CFD numerical simulation. Background Technology

[0002] Permeable structures, due to their large porosity and permeability, are conducive to water exchange, dissipation of wave energy, and enhancement of ecological effects. In recent years, they have been widely used in groynes, revetments, seawalls, and breakwaters.

[0003] Analyzing the flow field characteristics around water-related structures through CFD numerical simulation, and optimizing the cross-sectional design and planar layout of these structures, is an important approach for research on water-related structures in water conservancy, water transport, and marine engineering. Since permeable structures are generally composed of porous or open structures such as permeable frames, hollow blocks, and interlocking structures, their overall structure is complex. Directly characterizing the morphology of permeable structures for CFD numerical simulation faces challenges such as small mesh sizes and enormous computational demands.

[0004] Currently, porous media methods are generally used to simulate permeable structures. When using this method to simulate permeable structures, determining a reasonable porous media resistance coefficient is key to accurately simulating the hydraulic characteristics of permeable structures. Summary of the Invention

[0005] The problem to be solved by this invention is to provide a method for determining the resistance coefficient of porous media in permeable structures in CFD numerical simulation. Through flume tests, numerical inversion and resistance coefficient regression, the resistance coefficient of porous media in permeable structures of different scales can be determined, laying the foundation for accurately simulating the hydraulic characteristics of permeable structures and providing a reliable basis for engineering design.

[0006] This invention adopts the following technical solution: a method for determining the resistance coefficient of porous media in permeable structures in CFD numerical simulation, comprising the following steps:

[0007] Step 1: For the permeable structure to be studied, which is composed of several perforated or open structures (such as permeable frames, hollow blocks, H-shaped blocks, and interlocking bodies), obtain the cross-sectional dimensions of the permeable structure and the dimensions of individual perforated or open structures.

[0008] Step 2: Determine the n normal geometric scales in the permeable structure cross-section water tank test based on the cross-sectional dimensions of the permeable structure, the dimensions of a single perforated or open structure, the dimensions of the water tank, and the flow capacity.

[0009] Step 3: Determine the cross-sectional dimensions of permeable structures and the dimensions of individual perforated or open structures under each normal geometric scale condition, and fabricate several test structures under the normal geometric scale condition;

[0010] Step 4: Design a flue test for the cross section of a permeable structure under various normal geometric scale conditions. The number of test groups is m under each scale condition. Set the water depth and average flow velocity or water depth and flow rate for each test group.

[0011] Step 5: Conduct flow flume tests on permeable structure cross sections under various normal geometric scale conditions;

[0012] Step 6: Conduct CFD numerical flume tests on the cross-section of permeable structures under various normal geometric scales. Use the Forchheimer form of the resistance formula to calculate the resistance of porous media to water flow, and obtain the resistance coefficients of porous media under all normal geometric scales, including the viscous resistance coefficient A and the inertial resistance coefficient B.

[0013] Step 7: Based on the resistance coefficients (viscous resistance coefficient A and inertial resistance coefficient B) of porous media in permeable structures under different normal geometric scale conditions obtained in Step 6, establish the mathematical relationship between the viscous resistance coefficient A and the inertial resistance coefficient B and the normal geometric scale λ.

[0014] Step 8: Based on the mathematical relationship established in Step 8, calculate the viscous drag coefficient A and inertial drag coefficient B for the prototype scale (i.e., the normal geometric scale is 1) and other unknown normal geometric scales.

[0015] Furthermore, in step 2, the n normal geometric scales are λ1, λ2, λ3, ..., λ n When designing the geometric scale, ensure that there are 5-6 rows of perforated or open structures in the width direction of the water tank.

[0016] Furthermore, in step 3, the test structure should be made of a high-density material, preferably concrete or weight-added plastic.

[0017] Furthermore, in step 4, if the permeable structure is a non-submerged structure, the water depth in the flue test should be less than the top elevation of the permeable structure; if the permeable structure is a submerged structure, the water depth in the flue test should be greater than the top elevation of the permeable structure.

[0018] Furthermore, in step 5, a normal geometric scale λ is developed. i The specific steps for the permeable structure cross-section through a flow channel test under the condition of (i=1,2,3,…,n) are as follows:

[0019] Step 5.1: According to the scaled-down cross-sectional dimensions of the permeable structure, use the normal geometric scale λ. i Under the given conditions, permeable structures are constructed in the test section of the water tank. The permeable structures occupy the entire width of the water tank, and the width of the water tank is the cross-section of the permeable structures. The arrangement of the structures must be consistent with the actual production.

[0020] Step 5.2: Conduct the water tank test designed in Step 4 in the water tank. For each test, measure the water depth h in the upstream stable section of the permeable structure. 1j Cross-sectional average flow velocity u 1j Downstream stable section water depth h 2j and cross-sectional average flow velocity u 2j Where j is the label for different groups, j=1,2,3,…,m;

[0021] Step 5.3: Repeat steps 5.1 and 5.2 to complete the flume test for all permeable structure sections with normal geometric scales.

[0022] Furthermore, in step 6, a normal geometric scale λ is developed. i The following are the specific steps of the CFD numerical flume test for the flow of permeable structure cross sections under the condition of (i=1,2,3,…,n):

[0023] Step 6.1: Conduct a CFD numerical flume experiment for a specific scale. Establish a CFD numerical flume with the same range as the physical flume. The upstream boundary is a flow rate or velocity boundary, the downstream boundary is a pressure boundary, the side boundaries are symmetrical boundaries, the top is an air pressure boundary, and the bottom boundary is a sidewall boundary. Use no-slip conditions. The numerical model uses the porous media method to simulate the permeable structure. The size of the permeable structure is the same as that of the permeable structure in the physical flume with the same normal geometric scale.

[0024] Step 6.2: Use a CFD numerical flume to invert the physical flume tests conducted in Step 5.2 under the corresponding normal geometric scale conditions. That is, for each flume test group, adjust the porous medium resistance coefficient of the permeable structure in the CFD numerical simulation to ensure that the water depth h in the stable section upstream of the permeable structure is... 1j and cross-sectional average flow velocity u 1j Under the given conditions, the average flow velocity at the steady-state section in the lower reaches of the numerical flume is compared with the water depth h of the physical flume. 2j and cross-sectional average flow velocity u 2j This matches, thus yielding the resistance coefficient (viscous resistance coefficient A) of porous media in permeable structures under the corresponding normal geometric scale conditions. i and inertial drag coefficient B i );

[0025] Step 6.3: Repeat steps 6.1 and 6.2 to complete the CFD numerical flume tests for all permeable structure sections with normal geometric scales, and obtain the porous media drag coefficient (viscous drag coefficient A) for all normal geometric scales. i and inertial drag coefficient B i ).

[0026] Furthermore, in step 6.1, the resistance of the porous medium in the permeable structure in the CFD numerical simulation adopts the Forchheimer form of the resistance formula, characterized in that the resistance is the sum of the first and second terms of the micro-velocities in the porous medium region:

[0027] ;

[0028] In the formula: For porous media resistance; This is the viscous resistance term. This is the inertial drag term; The microscopic flow velocity in the porous medium region; For fluid density; Apparent flow rate; and Porosity of permeable structures The function; and These are the viscous drag coefficient and the inertial drag coefficient, respectively.

[0029] The present invention adopts the above technical solution and has the following advantages compared with the prior art:

[0030] 1. This invention employs a series of scale-based physical flume tests and CFD numerical flume tests to establish the viscous resistance coefficient. and inertial drag coefficient The mathematical relationship of normal geometric scale is used to obtain the values ​​of viscous drag coefficient and inertial drag coefficient under the prototype scale and other unknown normal geometric scales, which improves the accuracy of the drag coefficient of porous media, solves the problem of difficult accurate simulation of complex porous structures, and has significant engineering application value.

[0031] 2. This invention is applicable to permeable structures composed of different perforated or open structures (such as permeable frames, hollow blocks, H-shaped blocks, and interlocking bodies), and is suitable for both submerged and outlet forms. Attached Figure Description

[0032] Figure 1 This is a flowchart of the method for determining the resistance coefficient of porous media in permeable structures in CFD numerical simulation according to the present invention.

[0033] Figure 2 This is a cross-sectional dimension diagram of a hollow block breakwater according to an embodiment of the present invention (unit: m);

[0034] Figure 3 This is a schematic diagram of a hollow block in an embodiment of the present invention;

[0035] Figure 4 This is a diagram showing the results of numerical inversion of upstream and downstream water depths in a cross-section of a hollow block breakwater according to an embodiment of the present invention, obtained from a flume test.

[0036] Figure 5 This is a diagram showing the results of numerical inversion of the upstream and downstream flow velocity distribution along the flow path in the cross-section of the hollow block breakwater according to an embodiment of the present invention.

[0037] Figure 6 This is a graph showing the relationship between the viscous drag coefficient and the inertial drag coefficient as a function of the normal geometric scale in an embodiment of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments involved in this invention. All non-innovative embodiments based on these embodiments by other researchers in the art are within the protection scope of this invention. Furthermore, the step numbers in the embodiments of this invention are only set for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0039] In one embodiment of the present invention, a project plans to construct a breakwater (with its crest elevation above sea level) using hollow block materials. Compared with traditional riprap breakwaters, hollow block breakwaters offer better permeability, wave-control capabilities, and ecological benefits. To study the hydraulic characteristics and flow structure at the breakwater head of the hollow block breakwater, a CFD three-dimensional numerical simulation of the hollow block breakwater at a prototype scale is required. This necessitates accurately determining the porous medium resistance coefficient (including resistance coefficient) corresponding to the prototype scale of the hollow block breakwater. and inertial drag coefficient ).

[0040] In this embodiment, a method for determining the resistance coefficient of porous media in permeable structures during CFD numerical simulation is described, such as... Figure 1 As shown, it includes the following steps:

[0041] Step 1: For the breakwater composed of hollow blocks as described above, its cross-section is an isosceles trapezoid, such as... Figure 2 As shown, the upper base is 5m, the lower base is 35m, the height is 10m, and the slopes on both sides are 1:1.5.

[0042] Hollow blocks, such as Figure 3 As shown, it is a hollow cube with an outer contour side length of 1.8m. The surrounding rods are 0.35m wide and 1.1m long, and the inner reinforcing triangular rods are 0.2m × 0.2m × 0.35m in size.

[0043] The porosity of a single block is 0.64.

[0044] Step 2: The existing water tank is 41.2m long, 0.8m wide, and 0.8m deep, with an adjustable maximum slope of 1:60 and a maximum flow rate of approximately 0.1m³. 3 / s. Based on the size of the water tank and the flow capacity, combined with the cross-sectional dimensions of the water structure and the dimensions of the hollow block, four normal geometric scales were determined for the permeable structure cross-section through the water tank test, namely 15, 30, 50 and 75.

[0045] Under normal geometric scales of 15, 30, 50 and 75, the side lengths of the hollow blocks are 120mm, 60mm, 36mm and 24mm respectively, and the width of the water tank is 0.8m, satisfying that there are at least 5-6 rows of hollow blocks in the width direction of the water tank.

[0046] Step 3: Under the conditions of normal geometric scales of 15, 30, 50 and 75, the cross-sectional dimensions of permeable structures are shown in Table 1, and the dimensions of hollow blocks are shown in Table 2.

[0047] Table 1. Cross-sectional dimensions of permeable structures under different normal geometric scales.

[0048]

[0049] Table 2. Dimensions of hollow blocks under different normal geometric scales

[0050]

[0051] Furthermore, based on the determined hollow block size, a sufficient number of hollow blocks are manufactured under different normal geometric scales. In this embodiment, the number of hollow blocks under normal geometric scales of 15, 30, 50, and 75 are 270, 540, 900, and 1400, respectively. The hollow blocks with scales of 15 and 30 are made of weight-added plastic, as are the hollow blocks with scales of 50 and 75.

[0052] Step 4: Design a flow flume test for the permeable structure cross section under normal geometric scales of 15, 30, 50 and 75. Two test groups (m=2) are set for each scale condition. The water depth and flow rate of each test group are given in Table 3. The breakwater is an outflow breakwater. The water depth under each scale is lower than the height of the breakwater (see Table 1).

[0053] Table 3. Test parameters of permeable structure cross-sections with overflow flumes under different normal geometric scales.

[0054]

[0055] Step 5: Conduct a flume test on the cross-section of a permeable structure under the condition of normal geometric scale 15. The specific steps are as follows:

[0056] Step 5.1: According to the cross-sectional dimensions of the permeable structure under the normal geometric scale of 15, the permeable structure is constructed in the test section of the water tank using hollow blocks under the condition of normal geometric scale of 15. The permeable structure occupies the entire width of the water tank, and the width direction of the water tank is the cross-section of the permeable structure. The arrangement of the hollow blocks is consistent with the actual production. The first layer at the bottom is arranged in a regular manner, and the second layer and above are arranged randomly to ensure that the porosity is consistent with the prototype.

[0057] Step 5.2: Conduct the experiment designed in Step 4 in the water tank. For each set of experiments, measure the water depth h in the upstream stable section of the permeable structure. 1j Cross-sectional average flow velocity u 1j Downstream stable section water depth h 2j and cross-sectional average flow velocity u 2j Where j is the label for different groups, j=1,2,3,…,m;

[0058] Step 5.3: Repeat steps 5.1 and 5.2 to complete the flue test for all normal geometric scales (15, 30, 50 and 75) of the permeable structure cross section. The test measurement results are shown in Table 4.

[0059] Table 4. Test results of permeable structure cross-sections with overflow channels under different normal geometric scales.

[0060]

[0061] Step 6: Conduct CFD numerical flume tests on the permeable structure cross-section under normal geometric scales of 15, 30, 50, and 75. The specific steps are as follows:

[0062] Step 6.1. Conduct a CFD numerical flume experiment for a specific scale (e.g., 15). Establish a CFD numerical flume with the same range as the physical flume. The numerical flume is 41.2m long, 0.8m wide, and 0.8m deep. The grid resolution of the numerical flume in the horizontal direction is 0.002~0.5m, and the grid resolution in the vertical direction is 0.002~0.05m.

[0063] The turbulence model is a renormalization group (RNG) turbulence model, with the upstream boundary being the flow boundary, the downstream boundary being the pressure boundary, the side boundaries being the symmetry boundary, the bottom boundary being the sidewall boundary, and the top boundary being the air pressure boundary.

[0064] The sidewalls are designed for no-slip conditions, and the Volume of Fluid (VOF) method is used to track the free surface of the liquid. A hollow block breakwater is installed in the middle of the numerical flume, with its cross-section set in the width direction of the numerical flume, occupying the entire width of the numerical flume. The cross-sectional dimensions of the breakwater are the same as those of the breakwater at the same scale in the physical flume, as shown in Table 1.

[0065] In CFD numerical simulations, the resistance of porous media in permeable structures is expressed using the Forchheimer form of the resistance formula:

[0066] ;

[0067] In the formula: For porous media resistance; This is the viscous resistance term. This is the inertial drag term; The microscopic flow velocity in the porous medium region; It refers to the porosity of permeable structures; and These are the viscous drag coefficient and the inertial drag coefficient, respectively.

[0068] Step 6.2: Use a CFD numerical flume to invert the physical flume experiments conducted in Step 5.2 under the corresponding normal geometric scale conditions. That is, for each group of flume experiments (e.g., Group 1 in scale 15: static water depth 0.550m, flow rate 0.063m³ / h),... 3 / s), by adjusting the porous medium resistance coefficient of the permeable structure in the CFD numerical simulation, the water depth h in the stable section upstream of the permeable structure is made possible. 1j and cross-sectional average flow velocity u 1j Under the given conditions, the average flow velocity at the steady-state section in the lower reaches of the numerical flume is compared with the water depth h of the physical flume. 2j and cross-sectional average flow velocity u 2j They match perfectly.

[0069] In this embodiment, for a normal geometric scale of 15, when the viscous drag coefficient A and inertial drag coefficient B of the porous medium are adjusted to 0 and 45 respectively, the results of the numerical inversion of the upstream and downstream water depths of the hollow block breakwater cross-section through the flume are as follows: Figure 4 As shown, the velocity distribution along the upstream and downstream sides is as follows: Figure 5 As shown.

[0070] Figure 5 Different sub-graphs correspond to the velocity distribution at different locations along the flow path in the flume. In the sub-graph title, negative numbers represent the upstream distance of the structure, and positive numbers represent the downstream distance. For example: Figure 5 (a) shows the flow velocity distribution 4.68m upstream of the structure in the water tank. Figure 5 (l) represents the velocity distribution 14.04m downstream of the structure in the water tank.

[0071] Depend on Figure 4 and Figure 5 It can be seen that when the viscous resistance coefficient A of the porous medium is 0 and the inertial resistance coefficient B is 45, the water depth and flow velocity upstream and downstream of the hollow block breakwater are in good agreement with the measured values ​​in the physical flume.

[0072] Step 6.3: Repeat steps 6.1 and 6.2 to complete the CFD numerical flume tests for all permeable structure sections with normal geometric scales, and obtain the porous media drag coefficient (viscous drag coefficient A) for all normal geometric scales. i and inertial drag coefficient B i (See Table 5);

[0073] Table 5. Viscous and inertial drag coefficients of hollow block breakwaters under different normal geometric scales.

[0074]

[0075] Step 7: Based on different normal geometric scales λ i The resistance coefficients of porous media in permeable structures under certain conditions (viscous resistance coefficient A and inertial resistance coefficient B in Table 5) were analyzed. The variation of viscous resistance coefficient A and inertial resistance coefficient B with the normal geometric scale λ was also analyzed. The results are as follows: Figure 6 As shown. Figure 6 (a) reflects the variation of the viscous drag coefficient A with the normal geometric scale λ. Figure 6 (b) reflects the variation of the inertial drag coefficient B with the normal geometric scale λ.

[0076] It can be observed that the viscous drag coefficient A does not change with the normal geometric scale and its value is always 0; the inertial drag coefficient B increases approximately linearly with the increase of the geometric scale. Therefore, a relationship can be established between the viscous drag coefficient A and the inertial drag coefficient B and the normal geometric scale λ. i The mathematical relationship is as follows;

[0077] ;

[0078] .

[0079] Step 8: Based on the viscous drag coefficient A and inertial drag coefficient B established in Step 7, and the normal geometric scale λ... i Mathematical relationships, calculating the scale ratio of the prototype ( The corresponding viscous drag coefficient A and inertial drag coefficient B are 0m. -2 and 3m -1 Normal geometric scale 60 ( The corresponding viscous drag coefficient A and inertial drag coefficient B are 0m. -2 and 192m -1 .

[0080] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining the drag coefficient of a porous medium of a permeable structure in a CFD numerical simulation, characterized in that, Includes the following steps: Step 1: For the permeable structure to be studied, which consists of several perforated or open structures, obtain the cross-sectional dimensions of the permeable structure and the dimensions of individual perforated or open structures. Step 2: Determine the n normal geometric scales in the permeable structure cross-section water tank test based on the cross-sectional dimensions of the permeable structure, the dimensions of a single perforated or open structure, the dimensions of the water tank, and the flow capacity. Step 3: Determine the cross-sectional dimensions of permeable structures and the dimensions of individual perforated or open structures under each normal geometric scale condition, and fabricate several test structures under the normal geometric scale condition; Step 4: Design a flue test for the cross section of a permeable structure under various normal geometric scale conditions. The number of test groups is m under each scale condition. Set the water depth and average flow velocity or water depth and flow rate for each test group. Step 5: Conduct flow flume tests on permeable structure cross sections under various normal geometric scale conditions; Step 6: Conduct CFD numerical flume tests on the cross-section of permeable structures under various normal geometric scales. Use the Forchheimer form of the resistance formula to calculate the resistance of porous media to water flow, and obtain the resistance coefficients of porous media under all normal geometric scales, including the viscous resistance coefficient A and the inertial resistance coefficient B. Step 7: Based on the obtained resistance coefficients of porous media in permeable structures under different normal geometric scale conditions, establish the mathematical relationship between the viscous resistance coefficient A and the inertial resistance coefficient B and the normal geometric scale. Step 8: Based on the mathematical relationship, calculate the viscous drag coefficient A and inertial drag coefficient B for the prototype scale and other unknown normal geometric scales.

2. The porous media resistance coefficient determination method for a permeable structure according to claim 1, characterized by, In step 1, the perforated or open structure includes a permeable frame, a hollow block, a rectangular block, and a connecting body.

3. The porous media resistance coefficient determination method for permeable structures of claim 1, wherein, In step 2, there are n normal geometric scales, denoted as λ1, λ2, λ3, ..., λ n When designing the geometric scale, ensure that 5-6 rows of perforated or open structures are placed in the width direction of the water tank.

4. The porous media resistance coefficient determination method for permeable structures of claim 1, wherein, In step 3, the experimental structure is made of concrete or weight-added plastic.

5. The porous media resistance coefficient determination method for permeable structures of claim 1, wherein, In step 4, if the permeable structure is a non-submerged structure, the water depth in the flue test is less than the top elevation of the permeable structure; if the permeable structure is a submerged structure, the water depth in the flue test is greater than the top elevation of the permeable structure.

6. The porous media resistance coefficient determination method for permeable structures of claim 1, wherein, In step 5, normal geometric scale λ is carried out i The specific steps of the water permeable building section flow tank test under the condition of i = 1, 2, 3, …, n are as follows: Step 5.1: According to the scaled-down cross-sectional dimensions of the permeable structure, use the normal geometric scale λ. i Under the conditions, the test structure was constructed with permeable structures in the water tank test section. The permeable structures occupied the entire width of the water tank, and the width of the water tank was the cross-section of the permeable structures. The arrangement of the structures was consistent with the actual production. Step 5.2: Conduct the water tank test designed in Step 4 in the water tank. For each test, measure the water depth h in the upstream stable section of the permeable structure. 1j Cross-sectional average flow velocity u 1j Downstream stable section water depth h 2j and cross-sectional average velocity u 2j Where j is the label for different groups, j=1,2,3,…,m; Step 5.3: Repeat steps 5.1 and 5.2 to complete the flue test for all permeable structure sections with normal geometric scales.

7. The method for determining the resistance coefficient of porous media in permeable structures according to claim 6, characterized in that, In step 6, the normal geometric scale λ is developed. i The specific steps of the CFD numerical flume test for the flow-through section of a permeable structure under the specified conditions are as follows: Step 6.1: Select a scale from the normal geometric scale to conduct a CFD numerical flume experiment. Establish a CFD numerical flume with the same range as the physical flume. The upstream boundary is a flow rate or velocity boundary, the downstream boundary is a pressure boundary, the side boundary is a symmetrical boundary, the top is an air pressure boundary, and the bottom boundary is a sidewall boundary. Use no-slip conditions. The numerical model uses the porous media method to simulate the permeable structure. The size of the permeable structure is the same as the size of the permeable structure in the physical flume under the same normal geometric scale. Step 6.2: Use a CFD numerical flume to invert the physical flume tests conducted in Step 5.2 under the corresponding normal geometric scale conditions. For each flume test group, adjust the CFD numerical simulation of the porous medium resistance coefficient of the permeable structure so that the water depth h in the stable section upstream of the permeable structure is... 1j and cross-sectional average velocity u 1j Under the conditions, the average flow velocity in the downstream steady-state section of the numerical flume and the water depth h in the downstream steady-state section of the physical flume 2j and cross-sectional average velocity u 2j This is consistent with the results, yielding the porous media resistance coefficient of permeable structures under the corresponding normal geometric scale conditions, including the viscous resistance coefficient A. i and inertial drag coefficient B i ; Step 6.3: Repeat steps 6.1 and 6.2 to complete the CFD numerical flume test of the permeable structure cross section for all normal geometric scales, and obtain the resistance coefficient of porous media under all normal geometric scales.

8. The porous media resistance coefficient determination method for permeable structures of claim 7, wherein, In step 6, the resistance of the porous medium in the permeable structure in the CFD numerical simulation adopts the Forchheimer form of the resistance formula, where the resistance is the sum of the first and second terms of the micro-velocities in the porous medium region: ； In the formula: For porous media resistance; This is the viscous resistance term. This is the inertial drag term; The microscopic flow velocity in the porous medium region; For fluid density; Apparent flow rate; and Porosity of permeable structures The function; and These are the viscous drag coefficient and the inertial drag coefficient, respectively.

Images