Gap-containing fluid mechanical mesh generation method, device, equipment and medium

Abstract

The invention relates to the technical field of grid processing, and discloses a gap-containing fluid mechanical grid division method, device and equipment and a medium, and the method comprises the steps: obtaining a target flow field domain which comprises gaps; identifying a gap region in the target flow field domain, and determining a mainstream region based on the gap region; obtaining gap information of the gap region, and performing grid division based on the gap information; and performing grid division on the mainstream region. According to the method, the gaps contained in the target flow field domain are divided into the gap regions and the mainstream regions, and the corresponding grid processing is performed on each region, so that effective grid division can be realized, the grid processing efficiency is improved to a great extent, and the processing efficiency of the grid is improved. And a theoretical basis is further provided for gap-containing grid division in the field of rotating fluid machinery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of grid processing, and in particular to a fluid mechanical grid division method with gaps, device, equipment and medium. BACKGROUND

[0002] Computational Fluid Dynamics (CFD) is a scientific and technological technique for numerical simulation and analysis of fluid mechanics problems using computers and discrete numerical methods. It is a branch of fluid mechanics that has emerged in the contemporary era. With the rapid development of computing technology and computer technology, CFD technology has been applied to various aspects of national production, especially in the fields of aerospace, automobiles, ships, water conservancy, etc. It is widely used and is a very important auxiliary tool in engineering application and product design.

[0003] Further, the numerical simulation in CFD engineering uses grid division into structured grid and unstructured grid; among them, the main idea of structured grid is to split the complex geometry into several topological hexahedrons, and to cut each hexahedron into a generalized orthogonal, obtaining neat hexahedral grid; the cutting strategy is the core work of drawing structured grid, and the grid with regular cutting, angle and flow parallel or orthogonal can not only greatly reduce the number of grids, but also ensure high flow calculation accuracy. Unstructured grid is divided into tetrahedron according to various algorithms, and the nodes of tetrahedron can be further connected to form polyhedral grid (such as icosahedron) closer to sphere; algorithm is the core work of unstructured grid, and it is the main development direction of unstructured grid to stably and quickly generate topologically correct unstructured grid and maintain high grid quality as much as possible in the face of complex geometry.

[0004] Currently, the grid drawing strategy for the mainstream area of the rotary fluid machinery is relatively mature, and the structured grid can be quickly generated by professional software; the general algorithm of the unstructured grid is also good in the applicability to the mainstream area. However, when the gap is included, especially the gap with a large size ratio transition, the economy and the success rate of drawing of the two ways are greatly reduced. Specifically, for drawing the grid in the gap area, the general idea of the existing technology is to draw a small size grid in the gap area and a large size grid in the mainstream area, and to make a transition between the two, but the specific implementation details and the implementation difficulty are all lacking. In short, when the gap feature size and the mainstream feature size ratio is greater than 1:100, the gap area can be simply locally encrypted to draw the grid, that is, the gap area is still regarded as the mainstream area in essence; but when the ratio is less than 1:1000, the gap and the mainstream area size cannot be combined, and there is a lack of clear implementation technology to realize the drawing idea of the grid of such gap. In fact, for the drawing of the gap area in the rotary fluid, some simple structures of the gap do not need special technical solutions, so that when facing complex gaps, there is a lack of clear scheme in the field. In addition, the grid division of the tip gap is only mentioned in the field, and the drawing of other gaps and the generality between different kinds of gap technical schemes have not been considered. SUMMARY

[0005] Therefore, the present application provides a fluid machinery grid division method, device, equipment and medium containing a gap, to solve the problem that the existing rotary fluid machinery containing a gap lacks effective grid division, resulting in many defects, and further seriously affecting the grid processing efficiency.

[0006] In a first aspect, the present application provides a fluid machinery grid division method containing a gap, the method comprising:

[0007] obtaining a target flow field domain, the target flow field domain containing a gap;

[0008] identifying the gap area in the target flow field domain, and determining the mainstream area based on the gap area;

[0009] obtaining the gap information of the gap area, and performing grid division based on the gap information;

[0010] performing grid division on the mainstream area.

[0011] The present application obtains a target flow field domain, and after the region division of the gap area and the mainstream area in the gap contained in the target flow field domain, the corresponding grid processing is performed on each region, which can realize the effective division of the grid, greatly improve the processing efficiency of the grid, and further provide a theoretical basis for the grid division containing a gap in the field of rotary fluid machinery.

[0012] In an optional embodiment, a gap region in the target flow field domain is identified, and a main flow region is determined based on the gap region, comprising:

[0013] The gap region in the target flow field domain is determined based on a preset gap type, the preset gap type including a slit-shaped flow region, and a ratio of a flow extension direction of the slit-shaped flow region to a characteristic dimension of a normal direction thereof is greater than a preset threshold value; or the preset gap type including at least one typical gap of a target research object, wherein the target research object is used to construct the target flow field domain;

[0014] The gap region is subtracted from the target flow field domain to obtain the main flow region;

[0015] An interface between the gap region and the main flow region is determined, and a current gap type of the gap region is determined;

[0016] A cut position in the gap region is determined based on the current gap type, and the main flow region is updated based on the cut position and the interface to obtain an updated main flow region.

[0017] The present application identifies the gap region in the target flow field domain based on the general gap type and its geometric size, and the typical gap in the field of rotary fluid machinery, and obtains the main flow region from the gap region and performs the updating operation of the region optimization, which can guarantee the accuracy of the region division, and further guarantee the accuracy and efficiency of the subsequent grid division.

[0018] In an optional embodiment, the current gap type includes a wall gap and an intermediate gap; the wall gap is a gap at the boundary of the main flow region, and the intermediate gap is a gap inside the main flow region; the cut position in the gap region is determined based on the current gap type, comprising:

[0019] If the current gap type is the wall gap, a first multiple gap height is extended from the interface to the gap direction to obtain the cut position;

[0020] If the current gap type is the intermediate gap, a second multiple gap height is extended from the interface to the gap direction to obtain the cut position.

[0021] The present application takes into account the influence of the actual gap type on the corresponding cut position of the main flow region and the gap region, which can further improve the rationality of the region division, and further enhance the improvement effect of the region division on the grid drawing speed and drawing quality.

[0022] In an optional embodiment, before the main flow region is updated based on the cut position and the interface, the fluid mechanical grid division method with a gap further comprises:

[0023] It is detected whether there is edge transition geometric data, the edge transition geometric data including at least one of a chamfer and a round corner.

[0024] if the edge transition geometry data exists, extending the cut location to the gap direction by a target length, the target length being determined based on the edge transition geometry data;

[0025] if the edge transition geometry data does not exist, performing a step of updating the primary flow region based on the cut location and the interface.

[0026] The present application also considers the influence of the edge transition geometry data on the cut location corresponding to the primary flow region and the gap region, which greatly guarantees the accuracy of the region division.

[0027] In an optional embodiment, the gap information includes a gap shape and a gap height; the gap information of the gap region is acquired, and the mesh division is performed based on the gap information, including:

[0028] the gap shape and the gap height of the gap region are determined respectively;

[0029] whether the gap shape is regular and whether the gap height varies are determined respectively;

[0030] if the gap shape is regular, a quadrilateral swept mesh is used for the mesh division to generate the mesh of the gap region;

[0031] if the gap shape is irregular and the gap height is constant, a triangular swept mesh is used to generate the corresponding mesh of the gap region;

[0032] if the gap height varies, a variation rate of the gap height is determined, and the mesh division is performed based on the variation rate to generate the mesh of the gap region;

[0033] if the variation rate is low, the gap region is divided into blocks and then swept;

[0034] if the variation rate is high, the gap region is regionally divided based on the gap height to obtain a plurality of gap sub-regions; the sub-gap region and the sub-primary flow region are determined for each gap sub-region, and the step of determining the gap shape and the gap height of the gap region is returned for each sub-gap region until the corresponding mesh of each sub-gap region is generated.

[0035] The present application determines the mesh generation mode of the gap region by the variation of the gap shape and the gap height, which can guarantee the accurate generation of the mesh in the region, and further improves the accuracy and efficiency of the mesh division.

[0036] In an optional embodiment, the mesh division of the primary flow region includes:

[0037] a common node is set at the cut location, and the mesh division of the primary flow region is performed by using a preset division strategy, the preset division strategy including a first strategy and a second strategy;

[0038] The first strategy is to extend the main flow wall surface, so that the gap grid evolves into a wall boundary layer grid.

[0039] The second strategy is to expand the nodes in the main flow area radially around the interface, so that the gap radially evolves into the main flow.

[0040] The present application can ensure accurate generation of the grid in the region by setting different grid generation strategies, thereby improving the accuracy and efficiency of grid division.

[0041] In an optional embodiment, after setting the common node at the cut-off position, the fluid mechanical grid division method with a gap further comprises:

[0042] The nodes in the main flow area are generated into unstructured grids according to the node distribution at the interface; wherein the first layer of unstructured grids at the interface includes a four-pyramid grid or a three-prism grid.

[0043] The present application also takes into account the unstructured grid generation requirements in the main flow area, and can realize different ways of grid generation, further improving the accuracy and efficiency of grid generation.

[0044] In a second aspect, the present application provides a fluid mechanical grid division device with a gap, the device comprising:

[0045] The acquisition module is configured to acquire a target flow field domain, the target flow field domain containing a gap;

[0046] The identification module is configured to identify the gap region in the target flow field domain, and determine the main flow region based on the gap region;

[0047] The first division module is configured to acquire the gap information of the gap region, and perform grid division based on the gap information;

[0048] The second division module is configured to perform grid division on the main flow region.

[0049] The fluid mechanical grid division device with a gap of the present application divides the gap region and the main flow region in the target flow field domain obtained, and performs corresponding grid processing on each region, which can realize effective grid division, greatly improve the processing efficiency of the grid, and further provide a theoretical basis for grid division with a gap in the field of rotating fluid machinery.

[0050] In a third aspect, the present application provides a computer device, comprising a memory and a processor, which are communicatively connected with each other, and the memory stores computer instructions, and the processor executes the computer instructions to perform the gap-containing fluid mechanical grid partitioning method according to the first aspect or any one of the corresponding embodiments.

[0051] In a fourth aspect, the present application provides a computer readable storage medium, which stores computer instructions for making a computer execute the gap-containing fluid mechanical grid partitioning method according to the first aspect or any one of the corresponding embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0052] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0053] Figure 1 is a flowchart of a gap-containing fluid mechanical grid partitioning method according to an embodiment of the present application;

[0054] Figure 2 is a flowchart of another gap-containing fluid mechanical grid partitioning method according to an embodiment of the present application;

[0055] Figure 3 is a structural diagram of grid partitioning;

[0056] Figure 4 is a structural diagram of region position cutting;

[0057] Figure 5 is a structural diagram of gap grid partitioning;

[0058] Figure 6 is a structural diagram of another gap grid partitioning;

[0059] Figure 7 is a structural diagram of still another gap grid partitioning;

[0060] Figure 8 is a structural diagram of yet another gap grid partitioning;

[0061] Figure 9 is a structural block diagram of a gap-containing fluid mechanical grid partitioning device according to an embodiment of the present application;

[0062] Figure 10 is a structural diagram of a computer device according to an embodiment of the present application. DETAILED DESCRIPTION

[0063] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0064] Currently, mesh generation technology is not mature enough to handle mesh transitions with large-scale differences. Specifically, for rotating fluid machinery with gaps, traditional structured and unstructured meshes each have their own shortcomings. Structured meshes require a sound structural segmentation strategy. For geometries with large local curvature or narrow gaps, the segmentation complexity increases dramatically. Furthermore, established segmentation algorithms cannot reasonably segment complex geometries, requiring manual segmentation. This not only requires a certain level of segmentation experience and thinking, but also places significant pressure on practitioners when the number of blocks is too large. Furthermore, when the walls on either side of the gap are very close, the two parallel planes corresponding to the hexahedron are too close when associating the topology, which can easily lead to association errors. This reduces the robustness of the workflow and limits the potential for parameterization. Unstructured meshes, on the other hand, are primarily tetrahedral meshes, which are more adaptable to complex boundary shapes. However, to control mesh quality, the aspect ratio is strictly constrained by the algorithm. If there is a large difference between the gap height and the global characteristic size (such as more than 1000 times), but the gap extension area is large and reaches the global characteristic size, then the unstructured grid will still maintain a high density of small-scale grids in the gap extension direction, causing the number of grids to increase sharply. Ultimately, whether in the grid drawing step or in the solution step, it can easily exceed the current computing power level of the computer, and the large consumption of computing power does not bring about the corresponding accuracy improvement. Therefore, a fluid machinery meshing method with gaps is designed in this embodiment to solve the problems of difficult block segmentation ideas, large number of grids, and poor adaptability of the partitioning strategy in the CFD engineering of rotating fluid machinery containing gaps.

[0065] An embodiment of a method for meshing a fluid machinery with gaps is provided in an embodiment of the present invention. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0066] In this embodiment, a method for meshing fluid machinery with gaps is provided. Figure 1is a flowchart of a gap-containing fluid mechanical grid division method according to an embodiment of the present application, as shown in Figure 1 The flowchart includes the following steps:

[0067] In step S101, a target flow field domain is obtained, which contains a gap.

[0068] In this embodiment, the target flow field domain is the flow field domain of a target research object determined by a user (it should be noted that the specific content of the target research object in this embodiment can be adaptively adjusted according to actual project requirements, such as the target research object being a hydraulic unit), and its specific acquisition method can be determined according to related technologies in the art. For example, for a certain hydraulic unit containing a gap, its flow field domain can be obtained from a CAD (Computer Aided Design) three-dimensional model to obtain a corresponding geometric model, and the flow field domain is determined based on the geometric model, which is only exemplary.

[0069] In step S102, a gap region in the target flow field domain is identified, and a main flow region is determined based on the gap region.

[0070] It should be noted that the gap region in this embodiment is the corresponding region containing the gap, and the main flow region is other regions except the gap region.

[0071] In step S103, gap information of the gap region is obtained, and grid division is performed based on the gap information.

[0072] In this embodiment, the specific content of the gap information can be adaptively set according to actual requirements, such as the gap information including a gap type, which is only exemplary.

[0073] In step S104, the main flow region is subjected to grid division.

[0074] The gap-containing fluid mechanical grid division method according to the embodiment of the present application first obtains a target flow field domain, and then performs region division of a gap region and a main flow region in the target flow field domain containing a gap, and performs corresponding grid processing on each region, which can realize effective division of the grid, greatly improve the processing efficiency of the grid, and further provide a theoretical basis for gap grid division in the field of rotary fluid machinery.

[0075] In this embodiment, a gap-containing fluid mechanical grid division method is provided, Figure 2 is a flowchart of another gap-containing fluid mechanical grid division method according to an embodiment of the present application, as shown in Figure 2 The flowchart includes the following steps:

[0076] In step S201, a target flow field domain is obtained, which contains a gap. For details, please refer to Figure 1Step S101 of the illustrated embodiment, which will not be described here again.

[0077] Step S202, identify the gap region in the target flow field domain, and determine the main flow region based on the gap region.

[0078] Specifically, the above step S202 includes:

[0079] Step S2021, determine the gap region in the target flow field domain based on the preset gap type, the preset gap type includes a slit-shaped flow region and the ratio of the flow extension direction of the slit-shaped flow region to the normal direction thereof is greater than a preset threshold value; or, the preset gap type includes at least one typical gap of a target research object, wherein the target research object is used to construct the target flow field domain.

[0080] It should be explained that the gap refers to a geometric parameter, that is, the size of one or two dimensions in three-dimensional size is much smaller than the size of the remaining dimensions, such as the length-width-height ratio of 100:100:1, or 100:1:1; generally, such a region is found in the entire geometric model and is defined as a gap region, and the remaining larger part is called a main flow region. Specifically, for a hydraulic unit, the gap region can be determined according to industry consensus, such as the upper crown cavity gap, the lower ring cavity gap, the guide vane end surface gap, etc.

[0081] It should be noted that the specific value of the preset threshold value in the present embodiment can be adaptively set according to actual needs, which will not be limited in detail. In addition, the specific type of the typical gap in the present embodiment can be adaptively determined according to the actual content of the target research object, such as for a certain hydraulic unit, according to the industry consensus, it is known that the typical gap at least includes the upper crown cavity gap, the lower ring cavity gap, the guide vane end surface gap, the guide vane vertical surface gap, the blade tip gap, the guide bearing oil film, the thrust bearing oil film and the motor stator-rotor gap; wherein the actual meaning of each type of gap can be known by referring to the common knowledge in the art, which will not be described in detail.

[0082] Step S2022, subtract the gap region in the target flow field domain to obtain the main flow region.

[0083] Step S2023, respectively determine the interface of the gap region and the main flow region, and the current gap type of the gap region.

[0084] In the present embodiment, the current gap type is determined according to the relative position of the gap in the main flow region, such as the wall gap at the boundary of the main flow region, which is only exemplary.

[0085] Step S2024, determine the cutting position in the gap region based on the current gap type, and update the main flow region based on the cutting position and the interface to obtain the updated main flow region.

[0086] It should be noted that, because the actual distribution of the mainstream area and the gap area at the intersection is complex, a transition area may be formed. Therefore, it is necessary to effectively identify this transition area and use it to update the mainstream area. Specifically, in this embodiment, the gap area between the cut-off position and the interface is merged into the mainstream area to ensure the rationality of the mainstream area.

[0087] In this embodiment, the current gap types include wall gaps and middle gaps; the wall gaps are gaps at the boundary of the mainstream area, and the middle gaps are gaps inside the mainstream area.

[0088] Specifically, the above step S2024 includes:

[0089] Step A1: If the current gap type is a wall gap, extend the first multiple of the gap height from the interface toward the gap direction to obtain the cutting position.

[0090] In this embodiment, the value of the first multiple gap height needs to meet the set conditions, where the set conditions include that the transition area (i.e., the corresponding area formed by the cut position and the interface) is a square (i.e., the cross-sectional perspective in this area forms a square surface grid with an aspect ratio of 1:1).

[0091] Step A2: If the current gap type is an intermediate gap, extend the second multiple of the gap height from the interface toward the gap direction to obtain the cutting position.

[0092] In this embodiment, the specific value of the second multiple gap height is adaptively determined by referring to the value determination method of the first multiple gap height, and will not be repeated here.

[0093] Step A3: updating the mainstream area based on the cut-off position and the interface to obtain an updated mainstream area.

[0094] In this embodiment, the gap area between the cut position and the interface is merged into the mainstream area to obtain an updated mainstream area.

[0095] In the embodiment of the present invention, by considering the influence of the actual gap type on the corresponding cut-off positions of the mainstream area and the gap area, the rationality of the area division can be further improved, thereby enhancing the effect of area division on improving the mesh drawing speed and drawing quality.

[0096] It should be noted that, since the edge transition geometric data such as chamfers and fillets have a certain impact on the cut-off position corresponding to the mainstream area and the gap area, before the above steps to update the mainstream area based on the cut-off position and the interface, the meshing method of fluid machinery with gaps in this embodiment also includes:

[0097] Step B1, detecting whether edge transition geometry data exists, the edge transition geometry data including at least one of a chamfer and a fillet.

[0098] In the embodiment, the related meanings of the chamfer and the fillet can be known according to the prior art, which will not be described in detail here.

[0099] Step B2, if the edge transition geometry data exists, extending the cutting position to the gap direction by a target length, the target length being determined based on the edge transition geometry data.

[0100] In the embodiment, the target length is determined according to the actual edge transition geometry data, for example, if the chamfer exists, the target length of extending the cutting position to the gap direction is determined according to the length of the chamfer.

[0101] Step B3, if the edge transition geometry data does not exist, performing the step of updating the main flow region based on the cutting position and the interface.

[0102] In the embodiment, considering the influence of the edge transition geometry data on the corresponding cutting position of the main flow region and the gap region, the accuracy of the region division is greatly guaranteed.

[0103] In the embodiment, the gap region in the target flow field is identified based on the general gap type and the geometric size thereof and the typical gap in the field of rotary fluid machinery, the main flow region is obtained according to the gap region, and the region optimization update operation is performed, which can guarantee the accuracy of the region division, and further guarantee the accuracy and efficiency of subsequent mesh division.

[0104] Step S203, obtaining gap information of the gap region, and performing mesh division based on the gap information.

[0105] In the embodiment, the gap information includes a gap shape and a gap height.

[0106] Specifically, the above step S203 includes:

[0107] Step C1, respectively determining the gap shape and the gap height of the gap region.

[0108] Step C2, respectively judging whether the gap shape is regular and whether the gap height varies.

[0109] In the embodiment, since the gap shapes are various and the gap heights are different, the corresponding mesh division strategy is determined by analyzing the above gap information, which can guarantee the rationality of the mesh division strategy. It should be noted that the regular gap shape in the embodiment represents a regular gap shape such as a rectangular or a circular disc shape, which belongs to an ideal gap case, and the corresponding mesh can be directly generated by a sweeping operation.

[0110] Step C3, if the gap shape is regular, a quadrilateral swept grid is used to generate the grid of the gap region.

[0111] It should be noted that the quadrilateral swept grid is a form of generating structured grid by a specific way, which has the advantages of structural regularity (i.e. the grid cells are arranged neatly, the node distribution is orderly, and the grid density and direction are easy to control), high grid quality (i.e. the aspect ratio and angle of quadrilateral / hexahedral cells are easy to optimize, reducing the error in numerical calculation), high computational efficiency (i.e. the storage and calculation complexity of structured grid is lower than that of unstructured grid), boundary fitting (i.e. the cross-sectional grid is adjusted to adapt to the complex boundary shape), etc.

[0112] Step C4, if the gap shape is irregular and the gap height is constant, a triangular swept grid is used to generate the corresponding grid of the gap region.

[0113] In this embodiment, the related meaning of the triangular swept grid can be understood in the adaptability of the quadrilateral swept grid. It should be noted that compared with the quadrilateral swept grid, the triangular swept grid has the characteristics of strong adaptability to any geometry, no strict topological structure, high automation of grid generation, suitable for complex models, and lower computational accuracy.

[0114] Step C5, if the gap height changes, the change rate of the gap height is determined, and the grid is divided based on the change rate to generate the grid of the gap region.

[0115] In this embodiment, the change rate of the gap height represents the degree of change of the gap height.

[0116] Step C6, wherein, if the change rate is low, the gap region is divided into blocks and then swept.

[0117] In this embodiment, this step can decompose the complex geometry into sweepable blocks, and use the existing sweeping method to generate the volume grid.

[0118] Step C7, if the change rate is high, the gap region is regionally divided based on the gap height to obtain a plurality of gap sub-regions; the sub-gap region and the sub-main flow region are determined for each gap sub-region, and the step of determining the gap shape and the gap height of each gap sub-region is returned for each sub-gap region until the corresponding grid of each sub-gap region is generated.

[0119] In this embodiment, the regional division of the gap region in this step can refer to the division of the gap region and the main flow region described above, which will not be repeated here.

[0120] In a specific embodiment, the processing strategy for the gap height change rate is:

[0121] 1. When the change rate is low, the gap is divided into several sub-regions and then swept in blocks;

[0122] 2. When the change rate is high, the gap with large height is regarded as a secondary mainstream region, forming a nested structure of mainstream-secondary mainstream-gap;

[0123] 3. In addition, for the gap with regular wall shape, the sweeping direction can be changed to improve the grid processing efficiency.

[0124] Step S204, grid division is performed on the mainstream region.

[0125] Specifically, the above step S204 includes:

[0126] Step S2041, a common node is set at the cut-off position, and a preset division strategy is used to divide the grid of the mainstream region, the preset division strategy including a first strategy and a second strategy.

[0127] In this embodiment, the processing of the common node aims to ensure that the node position of the gap and the mainstream interface coincide, to realize direct transmission of physical quantities, and to avoid interpolation errors.

[0128] Step S2042, wherein the first strategy is a strategy of extending the mainstream wall surface so that the gap grid evolves into a wall boundary layer grid.

[0129] Step S2043, the second strategy is a strategy of expanding the nodes of the mainstream region radially around the interface, so that the gap evolves radially into the mainstream.

[0130] In this embodiment, the first strategy is also called the wall surface extension strategy, which is obtained by evolving the gap grid into the mainstream wall surface grid (i.e., the mainstream wall surface grid is obtained by extending the gap, and the gap grid is adsorbed and extended near the wall surface); and the second strategy is also called the spider strategy, which is obtained by gradually shrinking the mainstream grid as a whole; the two strategies can be adaptively determined according to the actual target research object, such as the specific gap type contained in the hydraulic unit.

[0131] In the embodiment of the application, different grid generation strategies are set to generate the grid of the mainstream region, which can ensure the accurate generation of the grid in the region, and thus improve the accuracy and efficiency of grid division.

[0132] In practical applications, the structural grid has less number of generated grids, fast calculation speed, but complex division steps, more labor time consumption, and is suitable for simple shape mainstream area; the non-structural grid has fast generation speed, but poor generation stability (high failure probability), more number of grids, slightly poor calculation speed and accuracy, and is suitable for complex shape mainstream area. Therefore, different grid division strategies can be adopted according to actual requirements for the mainstream area, that is, in addition to considering the generation requirements of the structural grid, the generation requirements of the non-structural grid in the mainstream area should also be considered. Therefore, after setting the common node at the cut-off position, the grid division method for the fluid mechanical gap in the embodiment further includes: generating a non-structural grid for the nodes of the mainstream area according to the node distribution at the interface; wherein the first layer of non-structural grid at the interface includes a four-pyramid grid or a three-prism grid.

[0133] It should be noted that the existing non-structured grid scheme contains tetrahedron + prism layer, so the four-pyramid grid or three-prism grid in the embodiment can be understood adaptively by referring to the existing technology. Specifically, considering the non-structural grid generation requirements in the mainstream area, different ways of grid generation can be realized, further improving the accuracy and efficiency of grid generation.

[0134] In a specific embodiment, in order to solve the problems of difficult block division idea, large number of grids, and poor adaptability of division strategy in the CFD engineering of rotating fluid machinery containing gaps, a grid division strategy is designed to be applied to a hydraulic unit, and the overall idea is as follows: in the gap flow (that is, in the rotating fluid machinery, in order to avoid the friction between the rotating parts and the static parts, a certain gap must be reserved between them, such as between the impeller and the pump body, the moving blade and the static blade; when the fluid machinery is running, due to the pressure difference on both sides of the gap, the fluid will flow through the gap, thereby forming the gap flow), the gap part has a small characteristic size, and fine grid is crucial for analyzing the gap flow. However, not all directions of flow require high accuracy. In the gap of the rotating fluid machinery, the flow scale in many gap extension directions is much larger than the gap height. Therefore, by analogy with the drawing idea of wall boundary layer grid, the embodiment uses a large aspect ratio flat structure grid in the gap, uses a non-structural grid or a structural grid with size transition in the large size area outside the gap, and shares a node at the interface between the two. As can be seen from the above, the embodiment is suitable for a general drawing strategy of the grid in any form of gap area and the transition area from the mainstream area to the gap in the rotating fluid machinery; wherein the gap types of the hydraulic unit include but are not limited to: upper crown cavity gap, lower ring cavity gap, guide vane end surface gap, guide vane vertical surface gap, blade tip gap, guide bearing oil film, thrust bearing oil film, motor stator-rotor gap, etc.

[0135] It should be explained that the gap area and the mainstream area in the embodiment each occupy a range in the flow field, which is distinguished as follows:

[0136] (1), Gap region refers to a long and narrow or flat gap-like flow region, the ratio of the characteristic size of the flow extension direction and its normal direction is large (usually at least 10:1 or more, in the case of smaller ratio, the embodiment is also applicable, but in the case of smaller ratio, there are more other simple and fast drawing methods, such as the installation gap between the runner and the top cover, the oil film region of the thrust bearing). Generally speaking, the grid of the gap region cannot be automatically and quickly drawn by commercial software unless it is an extremely simple geometric shape.

[0137] (2), the main flow region is a cavity-like flow region with complex shape and uniform characteristic scale, which is adjacent to the gap region, such as the internal cavity of the runner and the bearing oil tank. Generally speaking, if the main flow region and the gap region grid are required to be adjacent, the common node needs to be ensured, so the main flow region grid is also difficult to be automatically and quickly drawn by commercial software (the larger the ratio mentioned in the gap region, the more difficult it is).

[0138] In this embodiment, Figure 3 is a structural schematic diagram of grid division. From Figure 3 it can be seen that, no matter the type and shape of the gap, it should be drawn step by step according to the following steps, and the specific division steps include:

[0139] 1, cut off the main flow region and the gap region.

[0140] In this embodiment, this step belongs to the geometric processing step, which is to cut off the main flow region and the gap region at a suitable position. It should be noted that the cutting position should be inside the gap. Figure 4 is a structural schematic diagram of region position cutting, and it should be noted that the cutting position of the four transition regions is shown by the dashed line in the figure. Preferably, for the gap close to the main flow wall (i.e. the wall gap), it should be extended to 1 times the gap height from the geometric junction to the inside of the gap; for the gap in the middle of the main flow (such as the middle gap), it should be extended to 0.5 times the gap height from the geometric junction to the gap direction. In addition, if there is a fillet, the gap length occupied by the fillet should be excluded, such as reserving a section of the gap on the parallel part of the gap two side walls.

[0141] Further, the cutting position in the figure can form 2 or 1 square cross-sectional regions (i.e. the shaded part in the figure) at the junction, so that this region can quickly generate a face grid with an aspect ratio of 1. It should be noted that the purpose of cutting is to separate out a simple geometric pure gap region on the one hand, and on the other hand, it is necessary to retain the local size characteristics of the main flow to the gap.

[0142] 2, draw a large aspect ratio flat sweep grid of the gap.

[0143] In this embodiment, this step belongs to drawing the flat grid of the gap region shape rule. Specifically, for a simple rectangular or circular ring disc-shaped gap, a quadrilateral swept grid can be used, such as top-to-bottom or bottom-to-top sweeping. For a gap with a complex extension direction shape but a constant gap height, a triangular swept grid can be used. For a gap with a varying height, the following three strategies are used according to the degree of variation: (1) for a low variation rate, the gap can be directly divided into several low variation rate gap regions, and the block is swept; (2) for a high variation rate, the large height gap region can be regarded as a secondary primary flow region, and the above step 1 is used to process it to form a nested form of primary flow-secondary primary flow-gap; (3) if the shape of the gap on both sides is regular, the sweeping direction can be changed to the original orthogonal direction, that is, the wall surface is changed to a virtual surface inside the fluid as the sweeping starting surface.

[0144] Further, after forming the gap region drawing strategy, a reasonable grid size should be set to control the number of grids. Assuming that the grid size of the primary flow region is A and the grid size of the gap region is a, the wall surface grid size on both sides of the gap should be set to A, and the grid size in the height direction of the gap should be set to a or smaller (depending on the thickness of the boundary layer). Compared with simply reducing the grid size of the gap region, this method can greatly reduce the number of grids without affecting the analysis accuracy of the gap height.

[0145] 3. Draw the primary flow grid.

[0146] In this embodiment, the primary flow region is drawn in this step, which contains a structured grid or an unstructured grid. First, a common node should be set at the cut-off to avoid introducing artificial grid discontinuity, which affects the accuracy of subsequent calculations. Then, the degree of recognition is turned on to introduce the influence of the small grid size of the gap. Finally, the primary flow region grid is generated. If the primary flow region uses a structured grid, the size transition from the gap region to the primary flow region should be realized in the following two strategies:

[0147] (1) The wall boundary layer grids of the gap and the primary flow region are connected, and the node distribution is still maintained. Formally, it is shown that the gap is an extension of the primary flow region wall grid, which is called the wall extension strategy in this embodiment.

[0148] (2) The nodes of the primary flow region gradually expand in a radial manner according to the node distribution at the interface, which is called the spider web strategy in this embodiment.

[0149] It should be noted that the spider web strategy is more efficient and stable in generating results when other settings are the same. Since the wall extension may extend far, the number of spider web strategy grids is less than that of the wall extension strategy; in addition, the wall extension has a fundamental deficiency in handling flow fields containing rounded corners, so the spider web strategy is more recommended in this embodiment.

[0150] In this embodiment, if the main flow region adopts unstructured grids, the unstructured grids should be generated in the main flow region by inheriting the gap nodes at the interface, and the first layer grid at the interface should be a quadrangular pyramid or a triangular prism grid.

[0151] It should be noted that in this embodiment, based on the actual gap type, the embodiment of the corresponding gap grid division is also set (i.e., the specific grid division method suitable for the gap shape with different characteristics is given, wherein the guide vane end surface gap belongs to "gap height unchanged but shape irregular + main flow region complex", the upper crown cavity gap belongs to "gap shape regular but height changes + main flow region simple", which is only used as an exemplary illustration), please refer to Figures 5-8 It should be noted that, Figure 5 The uniform rotating sweep gap is related to the fluid area inlet and outlet between the upper and lower cover plates (or top cover and bottom ring) and the runner of the hydraulic machine, the blade tip gap, and the oil film area of the upper guide, lower guide, and water guide bearing. Figure 6 The uniform rotating sweep gap is related to the mechanical labyrinth seal ring of the rotating hydraulic machine due to the rounded transition at the interface, and the implementation method is mainly improved by the spider web strategy; the wall extension strategy is not easy to implement, and the grid quality is easy to lose control when the boundary layer grid layer is large, so it is not recommended. Figure 7 and Figure 8 The non-uniform rotating sweep gap is related to the non-circular circumferential symmetric rotating part, such as the guide vane end surface gap; this geometry has a high stability requirement for the generation of the main flow region cross-sectional plane grid, and the generation algorithm should have sufficient fault tolerance. It should be noted that two main flow region cross-sectional plane grid generation methods are given in this embodiment, one is triangular grid transition (such as Figure 7 ), and the swept three-prism grid is formed; one is quadrilateral transition (such as Figure 8 ), and the swept hexahedral grid is formed. In order to facilitate the display of the transition idea, the transition ratio in the figure is 1:1.5 to 1:2, which can be adjusted appropriately in actual application (generally 1:1.2, and the grid quality will be higher).

[0152] Specifically, the grid division has the beneficial effect that, according to the particularity of the intermediate gap in the rotary fluid machine, a grid drawing strategy of the rotary fluid machine containing the intermediate gap is designed. Compared with the pure structure grid, the embodiment greatly reduces the workload of manual operation and reduces the drawing difficulty; compared with the pure unstructured grid, the embodiment greatly reduces the total number of grids and improves the drawing speed; finally, the grid maintains good editability, can add a boundary layer, change the size or adjust the geometry at any time without repeating the manual operation process; the analytical accuracy of the flow field is ensured, and the grid is encrypted in the most important intermediate gap height direction.

[0153] In summary, the grid division method of the fluid machine containing the intermediate gap can effectively divide the grid, greatly improve the processing efficiency of the grid, and further provide a theoretical basis for the grid division of the rotary fluid machine containing the intermediate gap.

[0154] In the embodiment, a grid division device of a fluid machine containing an intermediate gap is also provided, which is used to implement the above-mentioned embodiments and preferred embodiments, and will not be described again. As used below, the term "module" can be a combination of software and / or hardware that can achieve a predetermined function. Although the device described in the following embodiments is preferably implemented in software, implementation of hardware or a combination of software and hardware is also possible and is contemplated.

[0155] The present application provides a grid division device of a fluid machine containing an intermediate gap, as shown in the figure, Figure 9 The device comprises:

[0156] The acquisition module 901 is configured to acquire a target flow field domain containing an intermediate gap.

[0157] The identification module 902 is configured to identify an intermediate gap region in the target flow field domain and determine a main flow region based on the intermediate gap region.

[0158] The first division module 903 is configured to acquire intermediate gap information of the intermediate gap region and perform grid division based on the intermediate gap information.

[0159] The second division module 904 is configured to perform grid division on the main flow region.

[0160] In some optional embodiments, the identification module 902 comprises a first identification submodule, a second identification submodule, a third identification submodule, and a fourth identification submodule; the first identification submodule is configured to determine a gap region in the target flow field based on a preset gap type, the preset gap type comprises a slit flow region, and a ratio of a flow extension direction of the slit flow region to a characteristic dimension of a normal direction thereof is greater than a preset threshold; or the preset gap type comprises at least one typical gap of a target research object, wherein the target research object is used to construct the target flow field; the second identification submodule is configured to subtract the gap region from the target flow field to obtain a main flow region; the third identification submodule is configured to determine an interface between the gap region and the main flow region, and a current gap type of the gap region; and the fourth identification submodule is configured to determine a cutting position in the gap region based on the current gap type, and update the main flow region based on the cutting position and the interface to obtain an updated main flow region.

[0161] In some optional embodiments, the fourth identification submodule comprises a first identification unit, a second identification unit, and a third identification unit; the first identification unit is configured to, if the current gap type is a wall gap, extend a first multiple of a gap height from the interface in a gap direction to obtain the cutting position; the second identification unit is configured to, if the current gap type is a middle gap, extend a second multiple of the gap height from the interface in the gap direction to obtain the cutting position; and the third identification unit is configured to determine the main flow region and a transition region based on the gap region.

[0162] In some optional embodiments, the fourth identification submodule comprises a detection unit configured to detect whether there is edge transition geometric data, the edge transition geometric data comprising at least one of a chamfer and a fillet; if there is the edge transition geometric data, the cutting position is extended by a target length in the gap direction, the target length being determined based on the edge transition geometric data; and if there is no edge transition geometric data, the step of updating the main flow region based on the cutting position and the interface is performed.

[0163] In some optional embodiments, the first dividing module 903 comprises a first judging submodule, a second judging submodule, a third judging submodule, a fourth judging submodule, a fifth judging submodule, a sixth judging submodule and a seventh judging submodule; wherein the first judging submodule is configured to determine the gap shape and the gap height of the gap region respectively; the second judging submodule is configured to determine whether the gap shape is regular and whether the gap height is variable respectively; the third judging submodule is configured to, if the gap shape is regular, perform grid division on the gap region by using a quadrilateral swept grid to generate a grid of the gap region; the fourth judging submodule is configured to, if the gap shape is irregular and the gap height is constant, generate a corresponding grid of the gap region by using a triangular swept grid; the fifth judging submodule is configured to, if the gap height is variable, determine a variation rate of the gap height and perform grid division based on the variation rate to generate a grid of the gap region; the sixth judging submodule is configured to, wherein if the variation rate is low, perform sweeping after dividing the gap region into blocks; and the seventh judging submodule is configured to, if the variation rate is high, perform regional segmentation on the gap region based on the gap height to obtain a plurality of gap sub-regions; determine a sub-gap region and a sub-main flow region for each gap sub-region respectively, and return to perform the steps of determining the gap shape and the gap height of the gap region for each sub-gap region until a corresponding grid of each sub-gap region is generated.

[0164] In some optional embodiments, the first dividing module 903 comprises a first identifying submodule, a second identifying submodule, a third identifying submodule and a fourth identifying submodule; wherein the first identifying submodule is configured to; the second identifying submodule is configured to; the third identifying submodule is configured to; and the fourth identifying submodule is configured to.

[0165] In some optional embodiments, the second dividing module 904 comprises a first dividing submodule, a second dividing submodule, a third dividing submodule and a fourth dividing submodule; wherein the first dividing submodule is configured to set a common node at the cut-off position and perform grid division on the main flow region by using a preset division strategy, and the preset division strategy comprises a first strategy and a second strategy; the second dividing submodule is configured to, wherein the first strategy is a strategy of extending the main flow wall surface so that the gap grid evolves into a wall boundary layer grid; the third dividing submodule is configured to, the second strategy is a strategy of radially expanding the nodes of the main flow region with the interface as the center so that the gap radially evolves into the main flow; and the fourth dividing submodule is configured to generate unstructured grids according to the node distribution at the interface; wherein the first layer of unstructured grids at the interface comprises a quadrangular pyramid grid or a triangular prism grid.

[0166] Further function descriptions of the above modules are the same as those of the above corresponding embodiments, which will not be described herein again.

[0167] The gap-containing fluid mechanical grid division device in the embodiment is in the form of a functional unit, where the unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and a memory executing one or more software or fixed programs, and / or other devices that can provide the above functions.

[0168] The gap-containing fluid mechanical grid division device in the embodiment performs region division on the gap region and the main flow region in the obtained gap contained in the target flow field, and performs corresponding grid processing on each region, so that effective division of the grid is achieved, the processing efficiency of the grid is greatly improved, and a theoretical basis for grid division containing gaps in the field of rotating fluid machinery is further provided.

[0169] The embodiment of the present application also provides a computer device, Figure 10 is a structural schematic diagram of the computer device provided in the optional embodiment of the present application, as Figure 10 indicated, the computer device comprises one or more processors 10, a memory 20, and an interface for connecting components, including a high-speed interface and a low-speed interface. Various components are communicatively connected to each other by different buses, and can be installed on a common mainboard or in other ways as needed. The processor can process instructions executed in the computer device, including instructions stored in the memory or graphics information of the memory to display a GUI on an external input / output system (such as a display device coupled to the interface). In some optional embodiments, multiple processors and / or multiple buses can be used with multiple memories and multiple memories, if necessary. Similarly, multiple computer devices can be connected, each computer device providing part of the necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Figure 9 In the embodiment, the processor 10 is taken as an example.

[0170] The processor 10 can be a central processor, a network processor, or a combination thereof. The processor 10 can further include a hardware chip. The hardware chip can be an application specific integrated circuit, a programmable logic device, or a combination thereof. The programmable logic device can be a complex programmable logic device, a field programmable logic gate array, a general array logic, or any combination thereof.

[0171] The memory 20 stores instructions executable by the at least one processor 10, so that the at least one processor 10 executes the method shown in the above embodiment.

[0172] The memory 20 can include a program storage area and a data storage area. The program storage area can store an operating system and application programs required by at least one function. The data storage area can store data created according to the use of the computer device, and the like. In addition, the memory 20 can include a high-speed random access memory, and can also include a non-transitory memory such as at least one magnetic disk storage device, a flash memory device, or other non-transitory solid-state memory device. In some alternative embodiments, the memory 20 can optionally include a memory disposed remotely from the processor 10, which can be connected to the computer device through a network. Examples of the network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0173] The memory 20 can include a volatile memory such as a random access memory, and can also include a non-volatile memory such as a flash memory, a hard disk, or a solid state disk. The memory 20 can also include a combination of the above-mentioned types of memories.

[0174] The computer device also includes a communication interface 30 for the host chip to communicate with other devices or communication networks.

[0175] The embodiments of the present application also provide a computer readable storage medium. The above-mentioned method according to the embodiments of the present application can be implemented in hardware, firmware, or recorded in a storage medium, or stored in a remote storage medium or a non-transitory machine readable storage medium through network downloading and stored in a local storage medium, so that the method described herein can be processed by such software on a storage medium using a general-purpose computer, a special-purpose processor, or programmable or special-purpose hardware. The storage medium can be a magnetic disk, an optical disk, a read-only memory, a random access memory, a flash memory, a hard disk, or a solid state disk, and the like. Further, the storage medium can also include a combination of the above-mentioned types of memories. It can be understood that the computer, the processor, the microprocessor host chip, or the programmable hardware includes a storage component that can store or receive software or computer code, which, when accessed and executed by the computer, the processor, or the hardware, implements the method shown in the above-mentioned embodiments.

[0176] Although the embodiments of the present application are described in conjunction with the accompanying drawings, various modifications and changes can be suggested by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and changes are intended to fall within the scope of the appended claims.

Claims

1. A method for meshing fluid machinery with gaps, characterized in that: The method comprises: Acquiring a target flow field, wherein the target flow field includes a gap; Identifying a gap region in the target flow field, and determining a mainstream region based on the gap region; Acquiring gap information of the gap area, and performing grid division based on the gap information; The main flow area is divided into grids.

2. The method for meshing a fluid machinery with gaps according to claim 1, characterized in that: The identifying of the gap area in the target flow field and determining the mainstream area based on the gap area includes: Determining a gap region in the target flow field based on a preset gap type, wherein the preset gap type includes a slit flow region and a characteristic dimension ratio of a flow extension direction to a normal direction of the slit flow region is greater than a preset threshold; or, the preset gap type includes at least one typical gap of a target research object, wherein the target research object is used to construct the target flow field; subtracting the gap area from the target flow field to obtain the mainstream area; respectively determining an interface between the gap region and the mainstream region, and a current gap type of the gap region; A cut-off position is determined in the gap region based on the current gap type, and the mainstream region is updated based on the cut-off position and the interface to obtain an updated mainstream region.

3. The method for meshing a fluid machinery with gaps according to claim 2, wherein: The current gap type includes a wall gap and an intermediate gap; the wall gap is a gap at the boundary of the mainstream area, and the intermediate gap is a gap inside the mainstream area; The determining a cut-off position in the gap area based on the current gap type includes: If the current gap type is a wall gap, extending the first multiple of the gap height from the interface toward the gap direction to obtain the cut-off position; If the current gap type is an intermediate gap, the second multiple of the gap height is extended from the interface toward the gap direction to obtain the cutting position.

4. The method for meshing a fluid machinery with gaps according to claim 2 or 3, characterized in that: Before updating the mainstream area based on the cut-off position and the interface, the method further includes: detecting whether there is edge transition geometric data, wherein the edge transition geometric data includes at least one of a chamfer and a rounded corner; If edge transition geometry data exists, extending the cut position in the gap direction by a target length, wherein the target length is determined based on the edge transition geometry data; If the edge transition geometry data does not exist, the step of updating the mainstream area based on the cut-off position and the interface is performed.

5. The method for meshing a fluid machinery with gaps according to claim 1, characterized in that: The gap information includes gap shape and gap height; The obtaining of gap information of the gap area and performing grid division based on the gap information includes: respectively determining a gap shape and a gap height of the gap area; respectively determining whether the shape of the gap is regular and whether the height of the gap changes; If the gap has a regular shape, a quadrilateral swept mesh is used for mesh division to generate a mesh for the gap area; If the gap shape is irregular and the gap height is constant, a triangular swept mesh is used to generate a corresponding mesh for the gap area; If the gap height changes, determining a rate of change of the gap height, and performing mesh division based on the rate of change to generate a mesh of the gap area; If the rate of change is low, the gap area is divided into blocks and then swept; If the rate of change is high, the gap area is divided into regions based on the gap height to obtain multiple gap sub-regions; a sub-gap area and a sub-mainstream area are respectively determined for each of the gap sub-regions, and the steps of respectively determining the gap shape and gap height of the gap area are returned to for each of the sub-gap areas until a corresponding grid is generated for each of the sub-gap areas.

6. The method for meshing a fluid machinery with gaps according to any one of claims 2 to 4, characterized in that: The gridding of the mainstream area includes: Setting a common node at the cut-off position and performing grid division on the main flow area using a preset division strategy, wherein the preset division strategy includes a first strategy and a second strategy; The first strategy is to extend the main wall surface so as to evolve the gap grid into the wall boundary layer grid; The second strategy is to radially expand the nodes in the mainstream area with the interface as the center, so that the gaps radially evolve into the mainstream.

7. The method for meshing a fluid machinery with gaps according to claim 6, characterized in that: After setting the common node at the cut-off position, the method further includes: The nodes in the mainstream area are distributed according to the nodes at the interface to generate an unstructured grid; wherein the first layer of unstructured grid at the interface includes a tetrahedral grid or a triangular prism grid.

8. A fluid machinery grid division device with gaps, characterized in that: The device comprises: An acquisition module, configured to acquire a target flow field, wherein the target flow field includes a gap; an identification module, configured to identify a gap region in the target flow field and determine a mainstream region based on the gap region; A first division module is used to obtain gap information of the gap area and perform grid division based on the gap information; The second division module is used to divide the mainstream area into grids.

9. A computer device, characterized in that: The computer device includes: a memory and a processor, the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the gap-containing fluid machinery grid division method according to any one of claims 1 to 7 by executing the computer instructions.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the gap-containing fluid machinery meshing method according to any one of claims 1 to 7.

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