Method for establishing water distribution ring pipe CFD analysis block structured grid

Abstract

The invention discloses a method for establishing a structured grid of a CFD analysis block of a water distribution ring pipe, belongs to the technical field of topological optimization, and aims to overcome the defects of establishing an unstructured grid model. Firstly, NX Open Grip is used for establishing a three-dimensional model of each pipe section of the water distribution ring pipe, Boolean summation calculation is conducted on all the main pipe sections, the branch pipe upstream sections, the branch pipe downstream sections, the branch pipe branch sections and the branch pipe sections after modeling is completed, modeling of the water distribution ring pipe is completed, then a hexahedron set isomorphic with the water distribution ring pipe in the topological sense is established through ICEM, and the three-dimensional model of each pipe section of the water distribution ring pipe is established. According to the method, according to the structural characteristics of different parts of the water distribution ring pipe, the coordinate of each control point and the diameter of the control section are utilized to establish a block structured grid on an isomorphic hexahedron group in the ICEM, the established block structured grid is mapped to the water distribution ring pipe, and establishment of the CFD analysis block structured grid of the water distribution ring pipe is completed. Open Grip and ICEM software is used for quickly completing modeling of the impact type water distribution ring pipe and establishment of a structured grid, and the method is used for CFD flow analysis of the water distribution ring pipe.

Description

Technical Field

[0001] This invention belongs to the field of topology optimization technology, and in particular relates to a method for establishing a structured mesh for CFD analysis of a water distribution loop using NX Open Grip and ICEM. This method can be used to quickly establish a structured mesh for an impingement water distribution loop and to perform CFD flow analysis of the water distribution loop. Background Technology

[0002] Impulse turbines are widely used in high-head power plants, and their single-unit capacity is constantly increasing. As a crucial flow-through component of the impulse turbine, the distribution ring pipe evenly introduces water flow into each branch pipe, significantly impacting the turbine's performance. Therefore, CFD flow analysis of the distribution ring pipe is necessary during the hydraulic design phase.

[0003] Currently, CFD analysis of water distribution loop pipes generally involves establishing an unstructured mesh model. However, unstructured mesh models have drawbacks such as slow mesh generation speed, low computational mesh quality, long computation cycle, and relatively coarse computational results. Summary of the Invention

[0004] The purpose of this invention is to provide a method for establishing a structured mesh for CFD analysis of water distribution loop pipes, thereby overcoming the shortcomings of establishing unstructured mesh models. The technical solution adopted by this invention is as follows:

[0005] A method for establishing a structured mesh for CFD analysis of a water distribution loop, wherein the water distribution loop consists of several pipe segments, which are divided into three types: main pipe segments, branch pipe segments, and branch pipe segments. Each branch pipe segment is formed by the confluence of an upstream branch pipe segment, a downstream branch pipe segment, and a branch pipe segment at one end. Several branch pipe segments are arranged sequentially from upstream to downstream. The downstream branch pipe segment of an upstream branch pipe segment is sequentially connected to the upstream branch pipe segment of an adjacent downstream branch pipe segment via several main pipe segments. The downstream branch pipe segment of the downstream end branch pipe segment is sequentially connected to several main pipe segments. Each branch pipe segment is sequentially connected to several branch pipe segments. The main pipe segments, the upstream and downstream branches of the branch pipe segments form the main water distribution path. Each branch pipe segment of the branch pipe segments forms a branch water distribution path with its corresponding branch pipe segment. The main water distribution path is vortex-shaped, and its diameter gradually decreases from upstream to downstream. The diameter of each branch water distribution path also gradually decreases from upstream to downstream. The method includes the following steps:

[0006] Step 1: In the Unigraphics NX program, based on the coordinates X of the control points on both sides of the main pipe section, upstream section of the branch pipe, downstream section of the branch pipe, branch pipe branch section, and branch pipe branch section... i Y i and control section diameter D iThe Open Grip module is used to create a 3D model of the corresponding cylindrical or conical control body, so that the cross-sectional contours at both ends are on the outer circumferential surface of the corresponding control body, and the parts at the outer ends of the cross-sectional contours are redundant parts.

[0007] Step 2: Using the Open Grip module, based on the control points and cross-sectional diameter D of the control volume... i Establish dividing planes; for the cylindrical or conical control bodies of the main pipe section and the branch pipe section, two dividing planes need to be established: the upstream dividing plane and the downstream dividing plane; for the control body of the upstream section of the branch pipe, three dividing planes need to be established: the upstream dividing plane, the main-main dividing plane between the upstream and downstream sections of the branch pipe, and the main-branch dividing plane between the upstream and branch pipe sections; for the control body of the downstream section of the branch pipe, three dividing planes need to be established: the main-main dividing plane between the upstream and downstream sections of the branch pipe, the branch-main dividing plane between the downstream and branch pipe sections, and the downstream dividing plane; for the control body of the branch pipe section, three dividing planes need to be established: the main-branch dividing plane between the upstream and branch pipe sections, the branch-main dividing plane between the downstream and branch pipe sections, and the corresponding downstream dividing plane; in any two connected pipe sections, the downstream dividing plane of the preceding pipe section is the same as the upstream dividing plane of the following pipe section;

[0008] Step 3: For the main pipe section and the branch pipe section, use the corresponding upstream and downstream dividing planes to cut and remove the control body of the main pipe section or the branch pipe section. After removing the excess parts at both ends of the control body, the corresponding main pipe section and branch pipe section are obtained.

[0009] Step 4: For the upstream section of the fork pipe, use the corresponding upstream side dividing plane, main dividing plane and main branch dividing plane to cut and remove the excess parts at both ends of the control body of the upstream section of the fork pipe to obtain the corresponding upstream section of the fork pipe;

[0010] Step 5: For the downstream section of the fork pipe, use the corresponding main main dividing plane, branch main dividing plane and downstream side dividing plane to cut and remove the excess parts at both ends of the control body of the downstream section of the fork pipe to obtain the corresponding downstream section of the fork pipe;

[0011] Step 6: For the branch road segment, use the corresponding main branch dividing plane, branch main dividing plane and downstream side dividing plane to cut and remove the excess parts at both ends of the control body of the branch road segment to obtain the corresponding branch road segment;

[0012] Step 7: Perform Boolean summation calculations on all main pipe sections, upstream sections of branch pipes, downstream sections of branch pipes, branch pipe sections of branch pipes, and branch pipe sections of branch pipes that have completed the design to complete the design of the water distribution ring pipe;

[0013] Step 8: Divide the water distribution ring pipe into two symmetrical parts using the mid-section surface, and only perform structured meshing on one half of it;

[0014] Step 9: Based on the cross-section of the water distribution ring pipe and the number of branch pipes, use ICEM software to create a hexahedron group that is topologically isomorphic to the water distribution ring pipe;

[0015] Step 10: Create a block structured mesh on the isomorphic hexahedron group in ICEM, and map the completed block structured mesh onto the water distribution loop pipe to complete the creation of the block structured mesh for CFD analysis of the water distribution loop pipe.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] Impulse turbines are widely used in high-head power plants, and their single-unit capacity is constantly increasing. As a crucial flow-through component of the impulse turbine, the distribution ring pipe evenly introduces water flow into each branch pipe, significantly impacting the turbine's performance. Therefore, CFD flow analysis of the distribution ring pipe is necessary during the hydraulic design phase. Compared to unstructured meshes, structured meshes offer advantages such as faster mesh generation, higher mesh quality, shorter computation cycles, and more accurate results. Therefore, structured meshes are more suitable for distribution ring pipes. This invention establishes a structured mesh algorithm for distribution ring pipe blocks to meet the computational needs of flow analysis in distribution ring pipes. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method steps of the present invention;

[0019] Figure 2 A 3D model of the water distribution ring pipe;

[0020] Figure 3 This is a 3D model of the bifurcation pipe section;

[0021] Figure 4 Cutting diagram for the main pipe section or branch pipe section;

[0022] Figure 5 A schematic diagram of the completed main pipe section or branch pipe section after cutting;

[0023] Figure 6 This is a cutting diagram of the upstream section of the forked pipe.

[0024] Figure 7 This is a design drawing of the upstream section of the bifurcation pipe after it has been cut.

[0025] Figure 8 This is a cutting diagram of the downstream section of the forked pipe.

[0026] Figure 9 This is a schematic diagram of the downstream section of the bifurcation pipe after cutting.

[0027] Figure 10 This is a cut-out diagram of the branch road section;

[0028] Figure 11 This is a schematic diagram of the completed branch pipe section after cutting.

[0029] Figure 12 This is a design drawing of a water distribution ring, cut through a mid-section.

[0030] Figure 13 for Figure 12 isomorphic hexahedral set;

[0031] Figure 14 for Figure 13 The block-structured mesh diagram.

[0032] In the diagram, 1-water distribution ring pipe; 2-pipe section; 3-main pipe section; 4-branch pipe section; 5-branch pipe branch section; 6-upstream section of the branch pipe; 7-downstream section of the branch pipe; 8-branch pipe branch section; 9-control point; 10-control body; 11-splitting plane; 12-upstream side splitting plane; 13-downstream side splitting plane; 14-main-main splitting plane; 15-main-branch splitting plane; 16-branch-main splitting plane; 17-mid-splitting plane. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0034] The connections mentioned in this invention are divided into fixed connections and detachable connections. Fixed connections, also known as non-detachable connections, include but are not limited to conventional fixed connection methods such as folded connections, riveted connections, adhesive connections, and welded connections. Detachable connections include but are not limited to conventional disassembly methods such as bolted connections, snap-fit ​​connections, pin connections, and hinged connections. When a specific connection method is not explicitly defined, it is assumed that at least one existing connection method can be found to achieve this function, and those skilled in the art can choose according to their needs. For example, a welded connection can be chosen for fixed connections, and a bolted connection can be chosen for detachable connections.

[0035] The present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0036] Example: Figures 1 to 14As shown, a method for establishing a structured mesh for CFD analysis of a water distribution loop is described. The water distribution loop 1 consists of several pipe segments 2, which are divided into three types: main pipe segments 3, branch pipe segments 4, and branch pipe segments 5. Each branch pipe segment 4 is formed by the confluence of an upstream branch pipe segment 6, a downstream branch pipe segment 7, and a branch pipe segment 8 at one end. Several branch pipe segments 4 are arranged sequentially from upstream to downstream. The downstream branch pipe segment 7 of the upstream branch pipe segment 4 is connected to the upstream branch pipe segment 6 of the adjacent downstream branch pipe segment 4 through several main pipe segments 3. The downstream branch pipe segment 7 is connected to the downstream branch pipe segment 4 through several main pipe segments 3. The downstream section 7 of segment 4 is sequentially connected to several main pipe sections 3. The branch pipe sections 8 of segment 4 are sequentially connected to several branch pipe sections 5. The main pipe sections 3, the upstream sections 6 and downstream sections 7 of segment 4 form a main water distribution route. The branch pipe sections 8 of segment 4 are sequentially connected to their corresponding branch pipe sections 5 to form water distribution branches. The main water distribution route is vortex-shaped, and its diameter gradually decreases from upstream to downstream. The diameter of the water distribution branches also gradually decreases from upstream to downstream. The method includes the following steps:

[0037] Step 1: In the Unigraphics NX program, based on the coordinates X of the control points 9 on both sides of the main pipe section 3, the upstream section 6 of the branch pipe, the downstream section 7 of the branch pipe, the branch pipe branch section 8, and the branch pipe branch section 5... i Y i and control section diameter D i The Open Grip module is used to create a 3D model of the corresponding cylindrical or conical control body 10, so that the cross-sectional contours at both ends are on the outer circumferential surface of the corresponding control body 10, and the parts at the outer ends of the cross-sectional contours are redundant parts.

[0038] Step 2: Using the Open Grip module, based on control point 9 of control body 10 and cross-sectional diameter D... iEstablish dividing planes 11; for the cylindrical or conical control bodies 10 of the main pipe section 3 and the branch pipe section 5, two dividing planes 11 need to be established, namely the upstream dividing plane 12 and the downstream dividing plane 13; for the control body 10 of the upstream section 6 of the branch pipe, three dividing planes 11 need to be established, namely the upstream dividing plane 12, the main dividing plane 14 between the upstream section 6 and the downstream section 7 of the branch pipe, and the main branch dividing plane 15 between the upstream section 6 and the branch pipe section 8 of the branch pipe; for the control body 10 of the downstream section 7 of the branch pipe, three dividing planes 11 need to be established, namely the branch pipe... The main dividing plane 14 between the upstream segment 6 and the downstream segment 7 of the branch pipe, the branch dividing plane 16 between the downstream segment 7 of the branch pipe and the branch segment 8 of the branch pipe, and the downstream dividing plane 13; for the control body 10 of the branch segment 8 of the branch pipe, three dividing planes 11 need to be established, namely the main branch dividing plane 15 between the upstream segment 6 of the branch pipe and the branch segment 8 of the branch pipe, the branch main dividing plane 16 between the downstream segment 7 of the branch pipe and the branch segment 8 of the branch pipe, and the corresponding downstream dividing plane 13; in any two connected pipe segments, the downstream dividing plane 13 of the preceding pipe segment is the same as the upstream dividing plane 12 of the following pipe segment;

[0039] Step 3: For the main pipe section 3 and the branch pipe section 5, the control body 10 of the main pipe section 3 or the branch pipe section 5 is cut and removed using the corresponding upstream side dividing plane 12 and downstream side dividing plane 13. After removing the excess parts at both ends of the control body, the corresponding main pipe section 3 and branch pipe section 5 are obtained.

[0040] Step 4: For the upstream section 6 of the fork pipe, use the corresponding upstream side dividing plane 12, main dividing plane 14 and main branch dividing plane 15 to cut and remove the excess parts at both ends of the control body 10 of the upstream section 6 of the fork pipe to obtain the corresponding upstream section 6 of the fork pipe.

[0041] Step 5: For the downstream section 7 of the fork pipe, use the corresponding main main dividing plane 14, branch main dividing plane 16 and downstream side dividing plane 13 to cut and remove the excess parts at both ends of the control body 10 of the downstream section 7 of the fork pipe to obtain the corresponding downstream section 7 of the fork pipe.

[0042] Step 6: For the branch road segment 8, use the corresponding main branch dividing plane 15, branch main dividing plane 16 and downstream dividing plane 13 to cut and remove the excess parts at both ends of the control body 10 of the branch road segment 8 to obtain the corresponding branch road segment 8.

[0043] Step 7: Perform Boolean summation calculations on all the main pipe section 3, upstream section 6, downstream section 7, branch section 8, and branch section 5 of the completed pipe to complete the design of the water distribution ring pipe 1.

[0044] Step 8: Considering the symmetry of the water distribution ring pipe 1 structure, the water distribution ring pipe 1 is divided into two symmetrical parts by the mid-plane 17, and only one half is divided into structured meshes.

[0045] Step 9: Based on the cross-section of the water distribution ring pipe 1 and the number of branch pipes 4, use ICEM software to establish a hexahedral group that is topologically isomorphic to the water distribution ring pipe 1.

[0046] Step 10: Create a block structured mesh on the isomorphic hexahedron group 18 in ICEM, and map the completed block structured mesh onto the water distribution loop 1 to complete the creation of the block structured mesh for CFD analysis of the water distribution loop 1.

[0047] Impulse turbines are widely used in high-head power plants, and their single-unit capacity is constantly increasing. As a crucial flow-through component of the impulse turbine, the distribution ring pipe evenly introduces water flow into each branch pipe, significantly impacting the turbine's performance. Therefore, CFD flow analysis of the distribution ring pipe is necessary during the hydraulic design phase. Compared to unstructured meshes, structured meshes offer advantages such as faster mesh generation, higher mesh quality, shorter computation cycles, and more accurate results. Therefore, structured meshes are more suitable for distribution ring pipes. This invention establishes a structured mesh algorithm for distribution ring pipe blocks to meet the computational needs of flow analysis in distribution ring pipes.

[0048] The above embodiments are merely illustrative examples of the present invention and do not limit its scope of protection. Those skilled in the art can make partial changes to them, as long as they do not exceed the spirit and essence of the present invention, they are all within the scope of protection of the present invention.

Claims

1. A method for establishing a structured grid for a CFD analysis block of a water distribution loop, wherein the water distribution loop (1) is composed of several pipe segments (2), and the pipe segments (2) are divided into three types: main pipe segment (3), branch pipe segment (4), and branch pipe segment (5). The branch pipe segment (4) is composed of a branch pipe upstream segment (6), a branch pipe downstream segment (7), and a branch pipe segment (8) connected at one end. Several branch pipe segments (4) are arranged sequentially from upstream to downstream. The branch pipe downstream segment (7) of the upstream branch pipe segment (4) is connected to the branch pipe upstream segment (6) of the adjacent downstream branch pipe segment (4) through several main pipe segments (3). The downstream section (7) of the fork pipe section (4) is sequentially connected to several main pipe sections (3), and the branch pipe sections (8) of the fork pipe section (4) are sequentially connected to several branch pipe sections (5). The several main pipe sections (3), the upstream sections (6) and the downstream sections (7) of the fork pipe sections (4) form the main water distribution route. The branch pipe sections (8) of the fork pipe section (4) are sequentially connected to the corresponding branch pipe sections (5) to form water distribution branches. The main water distribution route is vortex-shaped, and the pipe diameter gradually decreases from upstream to downstream. The pipe diameter of the water distribution branches gradually decreases from upstream to downstream. The method includes the following steps: Step 1: In the Unigraphics NX program, based on the coordinates (X) of the control points (9) on both sides of the main pipe section (3), the upstream section (6) of the branch pipe, the downstream section (7) of the branch pipe, the branch pipe section (8) and the branch pipe section (5), i Y i ) and control section diameter D i Using the Open Grip module, a three-dimensional model of the corresponding cylindrical or conical control body (10) is established, so that the cross-sectional contours at both ends are on the outer circumferential surface of the corresponding control body (10), and the part at the outer end of the cross-sectional contours at both ends is the redundant part. Step 2: Using the Open Grip module, based on the control point (9) of the control body (10) and the cross-sectional diameter D i Establish dividing planes (11); for the cylindrical or conical control bodies (10) of the main pipe section (3) and the branch pipe section (5), two dividing planes (11) need to be established, namely the upstream dividing plane (12) and the downstream dividing plane (13); for the control body (10) of the upstream section (6) of the branch pipe, three dividing planes (11) need to be established, namely the upstream dividing plane (12), the main dividing plane (14) between the upstream section (6) and the downstream section (7) of the branch pipe, and the main branch dividing plane (15) between the upstream section (6) and the branch pipe section (8); for the control body (10) of the downstream section (7) of the branch pipe, three dividing planes (11) need to be established, namely the branch dividing plane (12), the main dividing plane (14) between the upstream section (6) and the branch pipe section (8), and the main branch dividing plane (15) between the upstream section (6) and the branch pipe section (8). The main dividing plane (14) between the upstream section (6) and the downstream section (7) of the branch pipe, the branch dividing plane (16) between the downstream section (7) and the branch section (8) of the branch pipe, and the downstream dividing plane (13); for the control body (10) of the branch section (8), three dividing planes (11) need to be established, namely the main dividing plane (15) between the upstream section (6) and the branch section (8) of the branch pipe, the branch dividing plane (16) between the downstream section (7) and the branch section (8) of the branch pipe, and the corresponding downstream dividing plane (13); in any two connected pipe sections, the downstream dividing plane (13) of the previous pipe section is the same as the upstream dividing plane (12) of the next pipe section; Step 3: For the main pipe section (3) and the branch pipe section (5), use the corresponding upstream side dividing plane (12) and downstream side dividing plane (13) to cut and remove the control body (10) of the main pipe section (3) or the branch pipe section (5). After removing the excess parts at both ends of the control body, the corresponding main pipe section (3) and branch pipe section (5) are obtained. Step 4: For the upstream section (6) of the fork pipe, use the corresponding upstream side dividing plane (12), main dividing plane (14) and main branch dividing plane (15) to cut and remove the excess parts at both ends of the control body (10) of the upstream section (6) of the fork pipe to obtain the corresponding upstream section (6). Step 5: For the downstream section (7) of the fork pipe, use the corresponding main main dividing plane (14), branch main dividing plane (16) and downstream side dividing plane (13) to cut and remove the excess parts at both ends of the control body (10) of the downstream section (7) of the fork pipe to obtain the corresponding downstream section (7). Step 6: For the branch road segment (8), use the corresponding main branch dividing plane (15), branch main dividing plane (16) and downstream side dividing plane (13) to cut and remove the excess parts at both ends of the control body (10) of the branch road segment (8) to obtain the corresponding branch road segment (8). Step 7: Perform Boolean summation calculation on all the main pipe sections (3), upstream section (6), downstream section (7), branch section (8), and branch pipe section (5) of the completed pipe to complete the design of the water distribution ring pipe (1); Step 8: Divide the water distribution ring pipe (1) into two symmetrical parts by the mid-section (17), and only perform structured meshing on one half of it; Step 9: Based on the cross-section of the water distribution ring pipe (1) and the number of branch pipes (4), use ICEM software to establish a hexahedral group that is topologically isomorphic to the water distribution ring pipe (1); Step 10: Establish a block structured mesh on the isomorphic hexahedron group (18) in ICEM, and map the completed block structured mesh onto the water distribution ring pipe (1) to complete the establishment of the block structured mesh for CFD analysis of the water distribution ring pipe (1).

Images