Rainwater inspection well flow field analysis optimization model based on FLUENT and application thereof

Abstract

The invention discloses a rainwater inspection well flow field analysis optimization model based on FLUENT and application of the rainwater inspection well flow field analysis optimization model. According to the model, a rainwater inspection well circulation model is established, an inner flow channel structure of the rainwater inspection well circulation model is extracted, grid division is carried out on an inner flow channel, grid quality is detected, the divided grids are imported into FLUENT software, a turbulence energy model and a flow state model are loaded, boundary conditions are set, and water and gas distribution in an inspection well and a pipeline system is defined. Initializing setting, setting a solving step length and iteration precision, carrying out solving calculation, setting parameters, monitoring a flow field characteristic cloud picture, and checking a flow field distribution condition. According to the rainwater inspection well flow field analysis method based on FLUENT, overall simulation analysis of the rainwater inspection well and a pipeline system can be achieved, the change condition of the internal flow field can be accurately reflected, the rainwater inspection well prepared according to the model in an optimized mode can effectively improve the overflowing capacity of the inspection well, the risks of water flow blocking and overflowing are reduced, and the rainwater inspection well flow field analysis efficiency is improved. And head loss caused by an adverse flow state is reduced.

Description

Technical Field

[0001] The invention relates to a rainwater inspection well flow field model, in particular to a rainwater inspection well flow field analysis optimization model based on FLUENT and application thereof, belonging to the technical field of inspection wells. Background Art

[0002] With the continuous development of urbanization and the increase in extreme weather, the existing drainage system cannot meet the drainage needs under high-intensity precipitation, resulting in frequent urban waterlogging and seriously affecting people's quality of life. As an important component of the rainwater drainage system, the energy loss of rainwater inspection wells is one of the reasons that cannot be ignored for the decline in the drainage capacity of the pipe network.

[0003] At present, the flow field analysis of rainwater drainage systems is mostly aimed at pipes and special structures. The analysis results ignore the energy loss phenomenon inside the inspection well and the interaction characteristics between the inspection well and the pipe, and there is a large error with the actual situation. Accurate simulation of the flow field inside the rainwater inspection well can analyze its defects and deficiencies in the flow process, so as to optimize and improve its structure. Summary of the invention

[0004] In view of the problems existing in the prior art, the first purpose of the present invention is to provide a FLUENT-based rainwater inspection well flow field analysis optimization model. The model is based on the FLUENT-based rainwater inspection well flow field analysis method, which can realize the overall simulation analysis of the rainwater inspection well and the pipeline system, and more accurately reflect the changes in its internal flow field, which is of great significance to the design and optimization of the inspection well.

[0005] The second purpose of the present invention is to provide an application of a FLUENT-based rainwater inspection well flow field analysis optimization model for preparing a high-drainage, low-resistance rainwater inspection well. Based on the authenticity and accuracy of the description of the internal flow field of the inspection well by the above model, the optimized high-drainage, low-resistance rainwater inspection well can effectively improve the flow capacity of the rainwater inspection well, reduce the risk of water blockage and overflow, and reduce the head loss caused by unfavorable flow states.

[0006] In order to achieve the above technical objectives, the present invention provides a flow field analysis optimization model for a rainwater inspection well based on FLUENT, comprising:

[0007] Step S1, establishing a rainwater inspection well circulation model and extracting its internal flow channel structure;

[0008] Step S2, using unstructured tetrahedral meshes to divide the internal flow channel structure, and testing the quality of the divided meshes;

[0009] Step S3, importing the divided grid into FLUENT software, loading the turbulence energy model and flow state model;

[0010] Step S4, setting the boundary conditions of the model described in step S3, defining the water vapor distribution in the inspection well and the pipeline system according to the actual water flow fullness in the rainwater inspection well and the pipeline system, and then performing initialization settings, setting the time iteration step, iteration accuracy and total iteration step, and performing solution calculation;

[0011] Step S5, setting parameters and flow field characteristic cloud map monitoring according to the calculation results obtained in step S4, and checking the flow field distribution.

[0012] As a preferred solution, the rainwater inspection well circulation model is established through SOLIDWORK in ANSYS.

[0013] As a preferred solution, the inner flow channel structure is extracted through the Fill module in SOLIDWORK.

[0014] As a preferred solution, when the inner flow channel structure is meshed, the mesh size needs to be selected to reduce the number of meshes.

[0015] As a preferred solution, the quality of the divided grid is tested by FLUENT software.

[0016] As a preferred solution, the turbulence energy model and the flow state model respectively select the VOF two-phase flow model and the RNG k-ε model, and the fluid properties are set such that the liquid phase is liquid water and the gas phase is air.

[0017] As a preferred solution, the boundary condition setting process of the model is as follows: the upstream pipeline inlet surface is the velocity inlet, the ratio of water phase and gas phase is set to 0-1, the manhole cover opening surface is the velocity inlet, the ratio of water phase and gas phase is set to 0-1, and the downstream pipeline outlet surface is free outflow.

[0018] As a preferred solution, the initialization setting process is: use Region register to divide the liquid-gas distribution area at the initial time of flow, use Initialization to initialize the overall model, and use Phase value in the Patch function to define that the upper space of the inspection well is filled with air, the pressure is standard atmospheric pressure, and the lower space is filled with water.

[0019] As a preferred solution, the time iteration step is 0.001-0.005s, and the convergence residual is <10 -5 , the total number of iterations is > 20000 steps.

[0020] As a preferred solution, the process of monitoring the flow field characteristic cloud map is: importing the model calculation results into Tecplot and then extracting the velocity cloud map, velocity vector map and streamline map of the specific cross-section movement.

[0021] The present invention also includes an application of a FLUENT-based rainwater inspection well flow field analysis optimization model for preparing a high-drainage, low-resistance rainwater inspection well; the rainwater inspection well includes an inspection well chamber and a pipeline that are orthogonally distributed to each other, and a ventilation pipe is also provided between the inspection well chamber and the pipeline; the ventilation pipe is composed of a horizontal pipe (1), a vertical pipe (2) and a 90° elbow (3), wherein the horizontal pipe (1) is connected to the inspection well chamber (4), and the vertical pipe (2) is connected to the downstream pipe section (5) of the inspection well.

[0022] After the ventilation pipe is added to the inspection well provided by the present invention, the turbulence of the water flow in the downstream pipeline is weakened, the flow velocity classification is significantly improved, and the water flow can gradually return to stability during the flow along the pipeline. This shows that the addition of the ventilation pipe can effectively improve the flow state of the water flow in the downstream pipeline of the inspection well and reduce the energy loss caused by the turbulence of the water flow.

[0023] As a preferred solution, the diameter of the ventilation pipe is 0.08 to 0.15 m.

[0024] The vertical distance a between the horizontal pipe and the downstream pipe section of the inspection well is determined by formula 1:

[0025] Formula 1: a = xD;

[0026] In formula 1, the value range of x is 1 to 2 and is dimensionless; D is the diameter of the downstream pipe section of the inspection well and has a dimension of m.

[0027] As a preferred solution, the horizontal distance b between the vertical pipe and the inspection well chamber is determined by Formula 2:

[0028] Formula 2: b =yD;

[0029] In formula 2, the value range of y is 5 to 10 and is dimensionless; D is the diameter of the downstream pipe section of the inspection well and has a dimension of m.

[0030] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are:

[0031] 1) The model provided by the present invention is based on the stormwater inspection well flow field analysis method of FLUENT, which can realize the overall simulation analysis of the stormwater inspection well and the pipeline system, and more accurately reflect the changes in its internal flow field, which is of great significance to the design and optimization of the inspection well.

[0032] 2) In the technical solution provided by the present invention, based on the authenticity and accuracy of the above-mentioned model's description of the internal flow field of the inspection well, the optimized and prepared high-drainage and low-resistance rainwater inspection well can effectively improve the flow capacity of the rainwater inspection well, reduce the risk of water blockage and overflow, and reduce the head loss caused by adverse flow states. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of a common rainwater inspection well structure in the prior art;

[0034] Among them, 1-inspection well upstream pipe section, 2-inspection well downstream pipe section, 3-inspection well chamber;

[0035] Figure 2 A schematic diagram of the flow field of a common rainwater inspection well in the prior art;

[0036] in, Figure 2 (a) is the velocity contour diagram of the cross-sectional motion. Figure 2 (b) is the velocity vector diagram of the cross-sectional motion.

[0037] Figure 2 (c) is the streamline diagram of the cross-sectional motion;

[0038] Figure 3 This is a schematic diagram of the optimized inspection well structure in Example 1 of the present invention;

[0039] Among them, 1- upstream pipe section of the inspection well, 2- downstream pipe section of the inspection well, 3- inspection well chamber, 4- horizontal pipe, 5- vertical pipe, 6- 90° elbow;

[0040] Figure 4 This is a schematic diagram of the flow field of the inspection well after optimization in Example 1 of the present invention;

[0041] in, Figure 4 (a) is the velocity contour diagram of the cross-sectional motion. Figure 4 (b) is the velocity vector diagram of the cross-sectional motion.

[0042] Figure 4 (c) is the streamline diagram of the cross-sectional motion;

[0043] Figure 5 This is a schematic diagram of the flow field of the inspection well after optimization in Example 2 of the present invention;

[0044] in, Figure 5 (a) is the velocity contour diagram of the cross-sectional motion. Figure 5 (b) is the velocity vector diagram of the cross-sectional motion.

[0045] Figure 5 (c) is the streamline diagram of the cross-sectional motion;

[0046] Figure 6This is a schematic diagram of the flow field of the inspection well after optimization in Example 3 of the present invention;

[0047] in, Figure 6 (a) is the velocity contour diagram of the cross-sectional motion. Figure 6 (b) is the velocity vector diagram of the cross-sectional motion. Figure 6 (c) is the streamline diagram of the cross-sectional motion;

[0048] Figure 7 It is a graph showing the change of water flow and gas accumulation over time in a common rainwater inspection well in the prior art and the inspection well optimized in Examples 1 to 3;

[0049] Figure 8 This is a schematic flow chart of the flow field analysis method for a rainwater inspection well provided by the present invention. DETAILED DESCRIPTION

[0050] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0051] Example 1

[0052] Taking the common rainwater inspection well in the prior art as an example, its structure is as follows Figure 1 As shown in the figure, the flow field analysis optimization model is established, and the process is as follows:

[0053] 1. Use SOLIDWORK, the modeling software that comes with ANSYS, to build a circular rainwater straight inspection well flow channel model with the same diameter, and use the Fill function to extract the internal flow channel;

[0054] 2. Use ANSYS's own meshing software Meshing to mesh the inner flow channel. Use unstructured tetrahedral mesh in the inner flow channel area, select appropriate mesh size, reduce the number of meshes to reduce computing memory, and use FLUENT software to test the mesh quality of the mesh file after meshing.

[0055] 3. Import the grid into FLUENT software, load the turbulence energy model and flow state model, select the VOF two-phase flow model and RNG k-ε model, and set the fluid properties to liquid water for the liquid phase and air for the gas phase;

[0056] 4. Set each inlet and outlet, set the upstream pipeline inlet surface as the velocity inlet, set the water phase and gas phase ratio to 1, set the manhole cover opening surface as the velocity inlet, set the water phase and gas phase ratio to 0, and the downstream pipeline outlet surface as free outflow. Define the water vapor distribution in the inspection well and pipeline system according to the actual water flow fullness in the rainwater inspection well and pipeline system;

[0057] 5. Perform initialization settings, set the solution step size and iteration accuracy, and solve;

[0058] The initial condition setting method includes using the Region register in the Cellregisters option under Automatic mesh adaption to divide the liquid-gas distribution area at the initial time of the flow; using Initialization to initialize the overall model, using Phase value in the Patch function to define that the upper space of the inspection well is filled with air, the pressure is standard atmospheric pressure, and the lower space is filled with water; setting the time iteration step to 0.005s and the convergence residual to 10 -5 , the total number of iterations is 20,000, check whether the convergence residual meets the requirements;

[0059] 6. Set parameters and flow field characteristic cloud map monitoring to check the flow field distribution. Import the simulation calculation results into Tecplot, extract the velocity cloud map, velocity vector map, and streamline map of its cross-sectional motion, and the results are as follows: Figure 2 shown.

[0060] pass Figure 2 It can be seen that the water flow velocity distribution in the well chamber and downstream pipe section of the rainwater inspection well in the prior art is disordered, which is specifically manifested in the disordered distribution of the red high-velocity area and the green low-velocity area in the velocity cloud diagram, and the turbulent effect continues to affect the water flow at the rear end of the downstream pipeline; in addition, at the inlet of the downstream pipeline, there is an obvious velocity gradient grading, and a large vortex is generated on the inside of the pipeline bend.

[0061] In order to solve the above problems, the structure of the inspection well needs to be optimized, the main purpose of which is to weaken the turbulence of the water flow in the downstream pipe section and improve the flow velocity classification. Therefore, this embodiment proposes an optimized inspection well based on the data obtained by the above optimization model. A ventilation pipe is added between the inspection well and the pipeline. Its structure is as follows: Figure 3 As shown;

[0062] The ventilation pipe is composed of a horizontal pipe (1), a vertical pipe (2) and a 90° elbow (3);

[0063] The horizontal pipe (1) is connected to the inspection well chamber (4);

[0064] The vertical pipe (2) is connected to the downstream pipe section (5) of the inspection well.

[0065] The diameter of the ventilation pipe is 0.1m.

[0066] The vertical distance a between the horizontal pipe (1) and the downstream pipe section (5) of the inspection well meets the following conditions:

[0067] a=1D

[0068] Wherein, D is the diameter of the downstream pipe section (5) of the inspection well.

[0069] The horizontal distance b between the vertical pipe (2) and the inspection well chamber (4) meets the following conditions:

[0070] b=5D

[0071] Wherein, D is the diameter of the downstream pipe section (5) of the inspection well.

[0072] According to the optimized rainwater inspection well structure, the flow field analysis optimization model is re-established. The specific process is as follows:

[0073] 1. Use SOLIDWORK, the modeling software that comes with ANSYS, to build a circular rainwater straight inspection well flow channel model with the same diameter, and use the Fill function to extract the internal flow channel;

[0074] 2. Use ANSYS's own meshing software Meshing to mesh the inner flow channel. Use unstructured tetrahedral mesh in the inner flow channel area, select appropriate mesh size, reduce the number of meshes to reduce computing memory, and use FLUENT software to test the mesh quality of the mesh file after meshing.

[0075] 3. Import the grid into FLUENT software, load the turbulence energy model and flow state model, select the VOF two-phase flow model and RNG k-ε model, and set the fluid properties to liquid water for the liquid phase and air for the gas phase;

[0076] 4. Set each inlet and outlet, set the upstream pipeline inlet surface as the velocity inlet, set the water phase and gas phase ratio to 1, set the manhole cover opening surface as the velocity inlet, set the water phase and gas phase ratio to 0, and the downstream pipeline outlet surface as free outflow. Define the water vapor distribution in the inspection well and pipeline system according to the actual water flow fullness in the rainwater inspection well and pipeline system;

[0077] 5. Perform initialization settings, set the solution step size and iteration accuracy, and solve;

[0078] The initial condition setting method includes using the Region register in the Cellregisters option under Automatic mesh adaption to divide the liquid-gas distribution area at the initial time of the flow; using Initialization to initialize the overall model, using Phase value in the Patch function to define that the upper space of the inspection well is filled with air, the pressure is standard atmospheric pressure, and the lower space is filled with water; setting the time iteration step to 0.005s and the convergence residual to 10 -5 , the total number of iterations is 20,000, check whether the convergence residual meets the requirements;

[0079] 6. Set parameters and flow field characteristic cloud map monitoring to check the flow field distribution. Substitute the simulation calculation results into Tecplot, export the velocity cloud map, velocity vector map, and streamline map of the specific cross-section movement. The results show that the flow pattern of the water flow downstream of the inspection well has been improved, such as Figure 4 shown.

[0080] pass Figure 4 It can be seen that after adding the ventilation pipe, the water flow turbulence in the downstream pipeline is weakened, the flow velocity classification is significantly improved, and the water flow can gradually return to stability during the flow along the pipeline. This shows that adding the ventilation pipe can effectively improve the flow state of the water flow in the downstream pipeline of the inspection well and reduce the energy loss caused by water flow turbulence.

[0081] Example 2

[0082] This embodiment is exactly the same as Embodiment 1, except that:

[0083] An optimized inspection well, in which a ventilation pipe is added between the inspection well and the pipeline;

[0084] The ventilation pipe is composed of a horizontal pipe (1), a vertical pipe (2) and a 90° elbow (3);

[0085] The horizontal pipe (1) is connected to the inspection well chamber (4);

[0086] The vertical pipe (2) is connected to the downstream pipe section (5) of the inspection well.

[0087] The diameter of the ventilation pipe is 0.1m.

[0088] The vertical distance a between the horizontal pipe (1) and the downstream pipe section (5) of the inspection well meets the following conditions:

[0089] a=1D

[0090] Wherein, D is the diameter of the downstream pipe section (5) of the inspection well.

[0091] The horizontal distance b between the vertical pipe (2) and the inspection well chamber (4) meets the following conditions:

[0092] b=8D

[0093] Wherein, D is the diameter of the downstream pipe section (5) of the inspection well.

[0094] Through the rainwater inspection well structure of this embodiment, the flow field analysis optimization model is re-established, and its flow field distribution is as follows: Figure 5 shown.

[0095] Example 3

[0096] This embodiment is exactly the same as Embodiment 1, except that:

[0097] An optimized inspection well, in which a ventilation pipe is added between the inspection well and the pipeline;

[0098] The ventilation pipe is composed of a horizontal pipe (1), a vertical pipe (2) and a 90° elbow (3);

[0099] The horizontal pipe (1) is connected to the inspection well chamber (4);

[0100] The vertical pipe (2) is connected to the downstream pipe section (5) of the inspection well.

[0101] The diameter of the ventilation pipe is 0.1m.

[0102] The vertical distance a between the horizontal pipe (1) and the downstream pipe section (5) of the inspection well meets the following conditions:

[0103] a=1D

[0104] Wherein, D is the diameter of the downstream pipe section (5) of the inspection well.

[0105] The horizontal distance b between the vertical pipe (2) and the inspection well chamber (4) meets the following conditions:

[0106] b=10D

[0107] Wherein, D is the diameter of the downstream pipe section (5) of the inspection well.

[0108] Through the rainwater inspection well structure of this embodiment, the flow field analysis optimization model is re-established, and its flow field distribution is as follows: Figure 6 shown.

[0109] The present invention also tests the changes of water flow and gas accumulation over time in the common rainwater inspection wells and the optimized inspection wells in Examples 1 to 3, and the results are as follows: Figure 7 As shown, "1D1D" represents the horizontal distance b=1D between the vertical pipe and the manhole chamber and the vertical distance a=1D between the horizontal pipe and the downstream section of the manhole, and the meanings of the other legends are the same as above. Figure 7 It can be seen that in the inspection well of the prior art, in the initial stage of flow, it takes a long time for water to be discharged from the downstream pipeline through the inspection well; at the same time, when the flow state reaches stability after a long time, a persistent air resistance section is easily generated at the entrance of the downstream pipeline, hindering the discharge of water. Through the targeted optimization of the model provided by the present invention, by adding a vent pipe, water can be quickly discharged from the downstream pipeline after flowing through the inspection well in the initial stage, and after the flow reaches stability, no fixed air resistance section is generated, and the entire downstream pipe section can maintain full pipe flow drainage.

[0110] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A FLUENT-based rainwater inspection well flow field analysis optimization model, characterized in that: include: Step S1, establishing a rainwater inspection well circulation model and extracting its internal flow channel structure; Step S2, using unstructured tetrahedral meshes to divide the internal flow channel structure, and testing the quality of the divided meshes; Step S3, importing the divided grid into FLUENT software, loading the turbulence energy model and flow state model; Step S4, setting the boundary conditions of the model described in step S3, defining the water vapor distribution in the inspection well and the pipeline system according to the actual water flow fullness in the rainwater inspection well and the pipeline system, and then performing initialization settings, setting the time iteration step, iteration accuracy and total iteration step, and performing solution calculation; Step S5, setting parameters and flow field characteristic cloud map monitoring according to the calculation results obtained in step S4, and checking the flow field distribution.

2. According to the FLUENT-based rainwater inspection well flow field analysis optimization model of claim 1, it is characterized by: The rainwater inspection well circulation model is established through SOLIDWORK in ANSYS; the internal flow channel structure is extracted through the Fill module in SOLIDWORK.

3. According to the FLUENT-based rainwater inspection well flow field analysis optimization model of claim 1, it is characterized by: When the inner flow channel structure is meshed, the mesh size needs to be selected and the number of meshes needs to be reduced; the quality of the mesh after the meshing is tested by FLUENT software.

4. The FLUENT-based rainwater inspection well flow field analysis optimization model according to claim 1 is characterized in that: The turbulence energy model and flow state model are selected as VOF two-phase flow model and RNG k-ε model respectively, and the fluid properties are set as liquid water for the liquid phase and air for the gas phase.

5. The FLUENT-based rainwater inspection well flow field analysis optimization model according to claim 1 is characterized in that: The boundary condition setting process of the model is as follows: the upstream pipeline inlet surface is the velocity inlet, the ratio of water phase and gas phase is set to 0-1, the manhole cover opening surface is the velocity inlet, the ratio of water phase and gas phase is set to 0-1, and the downstream pipeline outlet surface is free outflow.

6. The FLUENT-based rainwater inspection well flow field analysis optimization model according to claim 1 is characterized by: The process of the initialization setting is: using Region register to divide the liquid-gas phase distribution area at the initial time of the flow, using Initialization to initialize the overall model, using Phasevalue in the Patch function to define that the upper space of the inspection well is filled with air, the pressure is standard atmospheric pressure, and the lower space is filled with water; The time iteration step is 0.001-0.005s, and the convergence residual is <10 -5 , the total number of iterations is > 20000 steps.

7. The FLUENT-based rainwater inspection well flow field analysis optimization model according to claim 1 is characterized by: The process of monitoring the flow field characteristic cloud map is as follows: importing the model calculation results into Tecplot and then extracting the velocity cloud map, velocity vector map and streamline map of the specific cross-section movement.

8. The application of a FLUENT-based rainwater inspection well flow field analysis optimization model as described in any one of claims 1 to 7, characterized in that: Used for preparing a high-discharge, low-resistance rainwater inspection well; the rainwater inspection well comprises an inspection well chamber and a pipeline which are orthogonally distributed to each other, and a ventilation pipe is also provided between the inspection well chamber and the pipeline; the ventilation pipe consists of a horizontal pipe (1), a vertical pipe (2) and a 90° elbow (3), wherein the horizontal pipe (1) is connected to the inspection well chamber (4), and the vertical pipe (2) is connected to the downstream pipe section (5) of the inspection well.

9. The application of a FLUENT-based rainwater inspection well flow field analysis optimization model according to claim 8 is characterized in that: The diameter of the ventilation pipe is 0.08-0.15 m; the vertical distance a between the horizontal pipe and the downstream pipe section of the inspection well is determined by formula 1: Formula 1: a = xD; In formula 1, the value range of x is 1 to 2 and is dimensionless; D is the diameter of the downstream pipe section of the inspection well and has a dimension of m.

10. The application of a FLUENT-based rainwater inspection well flow field analysis optimization model according to claim 8, characterized in that: The horizontal distance b between the vertical pipe and the inspection well chamber is determined by formula 2: Formula 2: b =yD In formula 2, the value range of y is 5 to 10 and is dimensionless; D is the diameter of the downstream pipe section of the inspection well and has a dimension of m.

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