CN114444416B - Grid aggregation method and device for fluid dynamics simulation - Google Patents
Grid aggregation method and device for fluid dynamics simulation Download PDFInfo
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Abstract
The application discloses a grid polymerization method and a grid polymerization device for fluid dynamics simulation, which are used for calculating the aerodynamic characteristics of an object to be measured. Firstly, acquiring a grid type in an initial fine grid graph of the object to be detected and a topological adjacency relation of a fine grid; and then, aggregating the initial fine grid graph according to the grid type and the topological adjacency relation to obtain a coarse grid. Aiming at the fine grids of different grid types, different methods can be adopted for polymerization to obtain a coarse grid with smaller stretching, the quality of the coarse grid is ensured, the numerical rigidity problem of flow field numerical simulation is avoided, and the stability of the flow field numerical simulation can be improved.
Description
Technical Field
The application belongs to the field of fluid dynamics simulation technology research, and particularly relates to a grid aggregation method and a grid aggregation device for fluid dynamics simulation.
Background
In the prior art, the processing method of the unstructured grid multi-polymerization technology is single, while the aircraft has different grid areas in the fluid dynamics simulation, the grid shapes of the different grid areas are different, and the grids comprise anisotropic grids and isotropic grids. The existing unstructured multi-grid aggregation methods include a "leading edge advancing method" and a "multi-level map partitioning method", etc. The basic idea of the 'leading edge advancing method' is to select an initial 'seed' grid unit set at a fine grid level, select adjacent units with the best quality after being aggregated with the current 'seed' units at the leading edge boundary of the current 'seed' unit set according to a greedy strategy to aggregate to form a new coarse grid level unit, update the leading edge boundary, and repeat the operation until all fine grids are aggregated with each other to form a new level coarse grid. The multi-level graph partitioning method considers the grid aggregation process as a global optimization problem, aggregates the grid aggregation process according to the strategy of graph partitioning, and ensures that the aggregated grid quality meets the set target function requirement by setting a specific aggregation proportion and a target function, but has the defects that a graph structure of a global grid needs to be constructed in advance, and the implementation process is complex. When viscous high-Reynolds-number flow simulation is considered, in order to ensure simulation accuracy, the grids near the wall surface of an object are often anisotropic high-stretch-ratio grids, and both of the above-mentioned multiple-grid methods are designed for isotropic grid types, directional information of the grids is not considered during aggregation, coarse grids with larger stretch ratios may be aggregated near the wall surface, so that the problem of 'numerical rigidity' is easily caused, the acceleration efficiency of a multiple-grid algorithm is influenced, and the problem of calculation stability is easily caused.
Disclosure of Invention
In order to solve the defects of the prior art, the present application provides a mesh aggregation method for fluid dynamics simulation, which may obtain a mesh type in an initial fine mesh map of the object to be measured and a topological adjacency relation of the fine mesh, and then aggregate the initial fine mesh map according to the mesh type and the topological adjacency relation to obtain a coarse mesh. According to the grid type and the topological adjacency relation, the initial fine grid is aggregated, namely, for the fine grids of different grid types, different methods can be adopted for aggregation to obtain a coarse grid with smaller stretching, the quality of the coarse grid is ensured, the numerical rigidity problem of flow field numerical simulation is avoided, and the stability of the flow field numerical simulation can be improved.
In a first aspect, the present application provides a mesh aggregation method for fluid dynamics simulation, for calculating aerodynamic characteristics of an object to be measured, the method comprising:
acquiring the grid type in the initial fine grid graph of the object to be detected and the topological adjacency relation of the fine grid;
and aggregating the initial fine grid graph according to the grid type and the topological adjacency relation to obtain a coarse grid.
Optionally, the mesh types include anisotropic meshes and isotropic meshes, and the mesh topological adjacency relations include anisotropic mesh topological adjacency relations; acquiring the grid type and the grid topological adjacency relation in the initial fine grid graph of the object to be detected, wherein the method comprises the following steps:
acquiring an initial fine grid map of the object to be detected;
obtaining the anisotropic grid and the isotropic grid according to the initial fine grid map;
and obtaining the topological adjacency relation of the anisotropic mesh according to the anisotropic mesh.
Optionally, the aggregating the initial fine mesh graph according to the mesh type and the topological adjacency relation to obtain a coarse mesh includes:
obtaining a grid unit set according to the anisotropic grid and the topological adjacency relation of the anisotropic grid; constructing a plurality of implicit lines on the anisotropic grid, wherein the implicit lines are uniformly distributed along the normal direction of the object plane from the object plane of the object to be detected to form the grid unit set with a plurality of grid units;
aggregating the grid units of the grid unit set according to a preset aggregation ratio M to form a coarse grid; and aggregating every M grid units to form the coarse grid, wherein M is a natural number which is not zero.
Optionally, the obtaining a set of grid cells according to the anisotropic grid and the anisotropic grid topological adjacency includes:
traversing the anisotropic grid to determine a first grid unit; the first grid unit comprises points on the object plane of the object to be detected, and has a pushing plane, and all points of the pushing plane are not on the object plane of the object to be detected;
obtaining the first grid unit set according to the first grid unit and the topological adjacency relation of the opposite-type grid;
constructing the implicit line in the first grid unit set from the advancing surface until the advancing surface is a boundary surface, and stopping constructing the implicit line;
and obtaining the grid unit set with a plurality of grid units according to the implicit line.
Optionally, the heterogeneous mesh topological adjacency relation includes a mesh adjacency relation, and the obtaining the first mesh unit set according to the first mesh unit and the topological adjacency relation includes:
determining an Nth of the first grid cells of the first set of grid cells, wherein N is a non-zero natural number;
acquiring a grid unit to be confirmed, wherein the opposite-type grid topological adjacency relation of the Nth first grid unit is a grid adjacency relation;
if the grid cell to be confirmed has a marking surface, and the points of the marking surface are not on the pushing surface of the Nth first grid cell, the grid cell to be confirmed is taken as the (N + 1) th first grid cell into the first grid cell set, and the order of taking the grid cells into the first grid cell set is marked;
taking the marked surface as the pushing surface after the grid unit to be confirmed is brought into the first grid unit set;
repeating the steps from the determining the Nth first grid cell of the first grid cell set to the step of incorporating the mark surface as the grid cell to be confirmed into the advancing surface of the first grid cell set until the grid cell no longer has the mark surface.
Optionally, the aggregating the grid cells of the grid cell set according to a preset aggregation ratio N to form a coarse grid includes:
acquiring an inclusion order of the first grid unit for inclusion in the first grid unit set;
acquiring a construction sequence of the implicit line constructed in the first grid unit set according to the inclusion sequence;
and aggregating the grid units of the grid unit set according to the construction sequence and the preset aggregation proportion N to form a coarse grid.
Optionally, the aggregating the initial fine mesh graph according to the mesh type and the topological adjacency relation to obtain a coarse mesh further includes:
constructing a sparse map for the isotropic mesh;
and aggregating the grid units of the sparse graph by adopting a multilevel graph partitioning algorithm to form a coarse grid.
In a second aspect, the present application also provides a mesh aggregation apparatus for fluid dynamics simulation, the apparatus comprising:
the acquisition module is used for acquiring the grid type in the initial fine grid graph of the object to be detected and the topological adjacency relation of the fine grids;
and the aggregation module is used for aggregating the initial fine grid graph according to the grid type and the topological adjacency relation to obtain a coarse grid.
Optionally, the obtaining module is configured to:
acquiring an initial fine grid map of the object to be detected;
obtaining the anisotropic grid and the isotropic grid according to the initial fine grid map;
and obtaining the topological adjacency relation of the anisotropic mesh according to the anisotropic mesh.
Optionally, the aggregation module is configured to:
obtaining a grid unit set according to the anisotropic grid and the topological adjacency relation of the anisotropic grid; constructing a plurality of implicit lines on the anisotropic grid, wherein the implicit lines are uniformly distributed along the normal direction of the object plane from the object plane of the object to be detected to form the grid unit set with a plurality of grid units;
aggregating the grid units of the grid unit set according to a preset aggregation ratio M to form a coarse grid; and aggregating every M grid units to form the coarse grid, wherein M is a natural number which is not zero.
Optionally, the aggregation module is configured to:
traversing the anisotropic grid and determining a first grid unit; the first grid unit comprises points on the object plane of the object to be detected, and has a pushing plane, and all points of the pushing plane are not on the object plane of the object to be detected;
obtaining the first grid unit set according to the topological adjacency relation between the first grid unit and the heterogeneous grid;
constructing the implicit line in the first grid unit set from the advancing surface until the advancing surface is a boundary surface, and stopping constructing the implicit line;
and obtaining the grid unit set with a plurality of grid units according to the implicit line.
Optionally, the aggregation module is configured to:
determining an Nth of the first grid cells of the first set of grid cells, wherein N is a non-zero natural number;
acquiring a grid unit to be confirmed, wherein the opposite-type grid topological adjacency relation of the Nth first grid unit is a grid adjacency relation;
if the grid cell to be confirmed has a marking surface, and the points of the marking surface are not on the pushing surface of the Nth first grid cell, the grid cell to be confirmed is taken as the (N + 1) th first grid cell into the first grid cell set, and the order of taking the grid cells into the first grid cell set is marked;
taking the marked surface as the pushing surface after the grid unit to be confirmed is brought into the first grid unit set;
repeating the steps from the determining the Nth first grid cell of the first grid cell set to the step of incorporating the mark surface as the grid cell to be confirmed into the advancing surface of the first grid cell set until the grid cell no longer has the mark surface.
Optionally, the aggregation module is configured to:
acquiring an inclusion order of the first grid unit for inclusion in the first grid unit set;
acquiring a construction sequence of the implicit line constructed in the first grid unit set according to the inclusion sequence;
and aggregating the grid units of the grid unit set according to the construction sequence and the preset aggregation proportion N to form a coarse grid.
In a third aspect, the present application also provides a readable medium, which includes an execution instruction, and when a processor of an electronic device executes the execution instruction, the electronic device executes the method according to the first aspect.
In a fourth aspect, the present application further provides an electronic device, which includes a processor and a memory storing execution instructions, and when the processor executes the execution instructions stored in the memory, the processor executes the method of the first aspect.
The grid polymerization method for the fluid dynamics simulation is used for calculating the pneumatic characteristics of an object to be measured and obtaining the grid type in an initial fine grid graph of the object to be measured and the topological adjacency relation of fine grids; and then, according to the grid type and the topological adjacency relation, aggregating the initial fine grid graph to obtain a coarse grid. Aiming at the fine grids of different grid types, different methods can be adopted for polymerization to obtain a coarse grid with smaller stretching, the quality of the coarse grid is ensured, the numerical rigidity problem of flow field numerical simulation is avoided, and the stability of the flow field numerical simulation can be improved.
Drawings
In order to more clearly illustrate the embodiments or prior art solutions of the present application, the drawings needed for describing the embodiments or prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present application, and that other drawings can be obtained by those skilled in the art without inventive exercise.
FIG. 1 is a flowchart of a mesh aggregation method for fluid dynamics simulation according to an embodiment of the present application;
FIG. 2 is an initial fine grid diagram of an object under test according to an embodiment of the present application;
FIG. 3 is a diagram illustrating the construction of hidden lines in an embodiment of the present application;
FIG. 4 is a schematic diagram of grid cells aggregated into a coarse grid according to an embodiment of the present application;
FIG. 5 is a coarse grid diagram of an object under test according to an embodiment of the present application;
FIG. 6 is a schematic structural diagram of a mesh aggregation apparatus for fluid dynamics simulation according to an embodiment of the present application;
fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following embodiments and accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the prior art, the multiple grid method is a technique for accelerating iterative solution of an algebraic equation system formed by discretization of partial differential equations. In the field of Computational Fluid Dynamics (CFD), a Geometric Multiple Grid (GMG) method is commonly used to aggregate and coarsen original grids to form coarse grids with different levels of density, and the convergence acceleration is achieved by using the principle of eliminating different wavelength residuals through cyclic calculation among grids with different density levels. The multiple grid convergence acceleration effect highly depends on the grid quality after aggregation and coarsening, namely the aggregated grid units are regular convex polyhedrons as much as possible and are usually measured by the aspect ratio index of the grid units, and the lower the aspect ratio, the better the quality. The structural grids are all composed of hexahedrons with directional information, so that high-quality coarsened grids can be easily obtained in different coordinate directions in a pairwise aggregation mode, but for non-structural grids, due to the irregularity of grid unit arrangement, the aggregation forming of high-quality multi-level coarse grids is difficult. In the prior art, the processing method of the unstructured grid multi-polymerization technology is single, while the aircraft has different grid areas in the fluid dynamics simulation, the grid shapes of the different grid areas are different, and the grids comprise anisotropic grids and isotropic grids. The multi-grid method is designed for the isotropic grid type, directional information of grids is not considered during aggregation, coarse grids with larger stretching ratio can be aggregated near the wall surface, the problem of numerical rigidity of fluid pressure calculation is easily caused, the acceleration efficiency of the multi-grid algorithm is influenced, and the problem of calculation stability is easily caused. In order to solve the above problems, the present application provides a mesh aggregation method for fluid dynamics simulation, which can obtain a mesh type in an initial fine mesh graph of the object to be measured and a topological adjacency relation of the fine mesh; and then, aggregating the initial fine grid graph according to the grid type and the topological adjacency relation to obtain a coarse grid. Aiming at the fine grids of different grid types, different methods can be adopted for polymerization to obtain a coarse grid with smaller stretching, the quality of the coarse grid is ensured, the numerical rigidity problem of flow field numerical simulation is avoided, and the stability of the flow field numerical simulation can be improved.
Various non-limiting embodiments of the present application are described in detail below with reference to the accompanying drawings.
Aggregation coarsening is performed by taking the aircraft NACA0012 airfoil non-structural initial fine grid diagram as an example.
Referring to fig. 1, a grid aggregation method for fluid dynamics simulation for calculating an aerodynamic characteristic of an object to be measured, the aerodynamic characteristic including a fluid pressure, in an embodiment of the present application is shown, and the method includes:
s101: and acquiring the grid type in the initial fine grid graph of the object to be detected and the topological adjacency relation of the fine grid.
When the initial fine grid of the object to be measured (aircraft) needs to be aggregated into the coarse grid, the grid type in the initial fine grid graph of the object to be measured and the topological adjacency relation of the fine grid can be obtained first, the initial fine grid graph of the object to be measured comprises a plurality of grid types, the grid types in the initial fine grid graph are obtained by the aid of different graphic characteristics of the grid types, and different aggregation methods can be adopted according to the grid types. The quality and stability of the coarse mesh can be improved. The topological adjacency relation of the fine grids can be obtained, so that the position relation among the fine grids can be clearly known, and the fine grids can be better aggregated into the coarse grids. Referring to fig. 2, in the non-structural initial fine grid diagram of the airfoil profile of the aircraft NACA0012, in the boundary layer area close to the surface of the airfoil profile, the grid types are mostly anisotropic quadrilateral grids, and the rest area far away from the surface of the airfoil profile is isotropic triangular grids. The initial fine mesh map in this embodiment is a data structure.
In this embodiment, the mesh types include anisotropic meshes and isotropic meshes, and the mesh topological adjacency relationship includes anisotropic mesh topological adjacency relationship; acquiring the grid type and the grid topological adjacency relation in the initial fine grid graph of the object to be detected, wherein the grid type and the grid topological adjacency relation comprise the initial fine grid graph of the object to be detected; then, obtaining the anisotropic grid and the isotropic grid according to the initial fine grid map; and then, obtaining the topological adjacency relation of the anisotropic grid according to the anisotropic grid. The initial fine grid graph is a computer graph used for simulating a flow phenomenon, the initial fine grid can be obtained from a simulation tool, and due to a plurality of factors influencing the fluid pressure of an object to be measured, fine grids of different grid types in the initial fine grid graph are formed. The anisotropic grid means that the grid cells have a large degree of extension in one direction and a small degree of extension in the other direction, and the grid cells are flat in shape. Conversely, an isotropic grid means that the grid cells have approximately the same degree of stretch in each direction, and the grid cells are square in shape. The shape characteristics of the anisotropic grids and the isotropic grids are different, and the same grid aggregation means is adopted, so that the stretching of some coarse grids is larger, the quality of the coarse grids is influenced, the anisotropic grids and the isotropic grids need to be obtained according to an initial fine grid diagram, namely, the fine grids in the initial fine grid diagram are divided into the anisotropic grids and the isotropic grids, and aggregation is conveniently carried out according to the grid types. The stretching degrees of the anisotropic grids in all directions are different, and the stretching degrees in all directions can influence the aggregation of the adjacent fine grids, so that the topological adjacent relation of the anisotropic grids can facilitate the aggregation of the adjacent fine grids into a coarse grid.
It should be understood that: the mesh is actually a discrete division of a continuous three-dimensional (or two-dimensional) space by polyhedral nature, and the fine mesh (fine grid) and the coarse mesh (coarse grid) are relative concepts. If we get a new set of grids again by aggregation on the basis of a set of original grids, the new grids are coarse grids, the original grids are fine grids, and they are opposite, and each grid cell of the coarse grids is formed by merging cells of the fine grids. The aggregation refers to merging at least two fine meshes into one coarse mesh.
S102: and aggregating the initial fine grid graph according to the grid type and the topological adjacency relation to obtain a coarse grid.
In the initial fine grid for fluid dynamics simulation of the object to be tested, because the factors influencing the fluid pressure of the object to be tested are more, the generated initial fine grid graph contains anisotropic grids and isotropic grids, and different aggregation processing methods are required for the fine grids of different grid types, so that the aggregated coarse grid is a regular convex polyhedron, namely a coarse grid with small stretching and square and regular grid units. The topological adjacency relation can clearly know the position relation of each fine mesh, and the anisotropic mesh and the isotropic mesh can be better aggregated according to the position relation of the fine meshes.
As shown in fig. 3-5, in this embodiment, the initial fine grid graph is aggregated according to the grid type and the topological adjacent relation to obtain a coarse grid, and a grid cell set may be obtained according to the anisotropic grid and the anisotropic grid topological adjacent relation; constructing a plurality of implicit lines on the anisotropic grid, wherein the implicit lines are uniformly distributed along the normal direction of the object plane from the object plane of the object to be detected to form the grid unit set with a plurality of grid units; then, aggregating the grid units of the grid unit set according to a preset aggregation ratio M to form a coarse grid; and aggregating every M grid units to form the coarse grid, wherein M is a natural number which is not zero. In this embodiment, the anisotropic mesh is stretched in a direction perpendicular to the normal direction of the object to be measured, and the mesh units are aggregated in the normal direction of the object to be measured to form a coarse mesh having approximately the same degree of stretchability. The implicit lines are uniformly distributed along the normal direction of the object plane from the object plane of the object to be detected, namely the implicit lines are perpendicular to the normal direction of the object plane. The grid cell is a grid that is re-established with the implicit lines over the area where the anisotropic grid is located.
In this embodiment, the mesh unit set is obtained according to the topological adjacency relationship between the anisotropic mesh and the anisotropic mesh, and the anisotropic mesh may be traversed to determine a first mesh unit; the first grid unit comprises points on the object plane of the object to be detected, and has a pushing plane, and all points of the pushing plane are not on the object plane of the object to be detected; then, obtaining the first grid unit set according to the first grid unit and the topological adjacency relation of the opposite-type grid; then, constructing the implicit line in the first grid unit set from the propelling surface until the propelling surface is a boundary surface, and stopping constructing the implicit line; then, the grid cell set with a plurality of grid cells is obtained according to the implicit line. The boundary surface is an edge of the grid map. And determining that the anisotropic grid is a fine grid needing aggregation by determining the first grid unit, namely the first grid unit is the anisotropic grid to be aggregated. And taking all the first grid cells and the heterogeneous grid topological adjacency relation as the first grid cell set. Constructing the implicit line in the first grid cell set, wherein the implicit line divides the first grid cell set into a plurality of grid cells, and the grid cells form the grid cell set. The propelling surface is a surface or a line in the aggregation direction of the fine grids, if the fine grids are three-dimensional grids, the propelling surface is a surface, and if the fine grids are two-dimensional grids, the propelling surface is a line. That is, in the aggregation direction, at least two fine meshes are combined into one coarse mesh. For example, the fine meshes are arranged in an array having an up-down direction and a left-right direction, and if the aggregation direction is the left-right direction, at least two fine meshes are merged into one coarse mesh in the left-right direction, in which case, the width of the coarse mesh in the up-down direction is the same as that of a single fine mesh, and the width of the coarse mesh in the left-right direction is equal to the sum of the widths of the aggregated at least two fine meshes.
In this embodiment, the topological adjacent relationship of the heterogeneous meshes includes a mesh adjacent relationship, where the mesh adjacent relationship refers to that two meshes are adjacent to each other, and they have the same plane, and the first mesh unit set is obtained according to the first mesh unit and the topological adjacent relationship, so that the nth first mesh unit of the first mesh unit set can be determined, where N is a natural number that is not zero; then, obtaining the mesh unit to be confirmed, wherein the opposite-type mesh topological adjacency relation of the Nth first mesh unit is the mesh adjacency relation; since the adjacent first grid cells meeting the conditions found according to the grid adjacency relation may already be in the first grid cell set, then, if the grid cell to be confirmed is not in the first grid cell set and has a marking surface, and the points of the marking surface are not in the advancing surface of the nth first grid cell, the grid cell to be confirmed is taken as the N +1 th first grid cell into the first grid cell set, and the order of taking the grid cells into the first grid cell set is marked; then, taking the mark surface as the pushing surface after the grid unit to be confirmed is brought into the first grid unit set; then, repeating the steps from the step of determining the nth first grid cell of the first grid cell set to the step of incorporating the mark surface as the mesh cell to be confirmed into the push surface of the first grid cell set until the mesh cell to be confirmed no longer has the mark surface. According to the order of the first grid unit in the first grid unit set, the implicit line is constructed for the first grid unit according to the order, so that the arrangement of the implicit line is regular, and the grid units are convenient to aggregate subsequently. And if the points of the marking surface are not on the pushing surface of the nth first grid unit, it means that the grid unit to be confirmed is not brought into the first grid unit, and the marking surface is not constructed with the implicit line, the implicit line needs to be constructed on the marking surface of the grid unit to be confirmed.
In one example, all of the anisotropic grids are traversed in a loop, if one of the anisotropic grids C1If one said pushing plane can be found, said isotropic grid is used as said first grid unit, and a first grid unit set is constructed, and said anisotropic grid C is used1Including the first grid cell set as the first grid cell and within the anisotropic grid C1And constructing an implicit line, namely constructing the implicit line on the first grid unit, and marking that the implicit line is constructed on the first grid unit. And when the implicit line is constructed for the first grid unit, if the push surface is a boundary surface, the construction of the implicit line is stopped. According to the topological adjacency relation of the anisotropic grids, confirming the anisotropic grids adjacent to the first grid unit newly added into the first grid unit, and if the anisotropic grids are positioned on the anisotropic grid C2If a mark surface can be found, and all points of the mark surface are not on the pushing surface of the first grid cell, the anisotropic grid cell is taken as the first grid cell and is included in the first grid cell set, and the order of the anisotropic grid cell to be included in the first grid cell set is marked, and for new inclusionThe first grid cell of the first set of grid cells performs the construction of the implicit line. And continuing repeating the process, namely confirming whether the anisotropic grid unit adjacent to the first grid unit newly included in the first grid unit set is a first grid unit, if so, including the anisotropic grid unit in the first grid unit set, and constructing the implicit line until confirming that the fine grid adjacent to the first grid unit newly included in the first grid unit set does not have a marking surface any more, and stopping constructing the implicit line.
In this embodiment, the aggregating the grid cells of the grid cell set according to a preset aggregation ratio M to form a coarse grid may obtain an inclusion order in which the first grid cell is included in the first grid cell set; then, acquiring a construction sequence of the implicit line constructed in the first grid unit set according to the inclusion sequence; and then, aggregating the grid units of the grid unit set according to the construction sequence and the preset aggregation ratio M to form a coarse grid. The implicit lines are sequentially constructed according to the inclusion sequence of the first grid unit in the first grid unit set, the grid units are sequentially aggregated according to the construction sequence of the implicit lines, the grid units in the grid unit set can be sequentially aggregated, the aggregated coarse grids are sequentially arranged, and the coarse grids are closely connected. In this embodiment, if the grid cells are sequentially aggregated according to a preset aggregation ratio M and the construction sequence of the implicit line, and the number of the remaining grid cells is not enough than M, the remaining grid cells are aggregated into a coarse grid, where M is 4 in this embodiment.
In this embodiment, the initial fine grid map is aggregated according to the grid type and the topological adjacency relation to obtain a coarse grid, and a sparse map may be constructed for the isotropic grid; and then, aggregating the grid units of the sparse graph by adopting a multilevel graph partitioning algorithm to form a coarse grid. A "sparse map" in CSR format is constructed for the remaining isotropic grid cells that have not yet been aggregated. The CSR format is a generic data structure that stores "sparse maps". For the unstructured grid, one grid unit forms one node of the sparse graph, and two adjacent units which share the same surface are connected to form one edge of the sparse graph. And aggregating the residual isotropic grids by adopting a multilevel graph partitioning strategy. And the obtained CSR format data and the number range (maximum maxsize and minimum minisize) of the fine grids contained in each coarse grid unit are used as input and are transmitted into a grid aggregator MGridge, the MGridge is operated, and the coarse grids are aggregated.
In this embodiment, after the fine grids in the initial fine grid map are aggregated to form the coarse grid, the coarse grid map formed by aggregation may be used as the fine grid of the next level, and the fine grids of the next level are aggregated repeatedly to form the coarse grid map of the next level until the coarse grid map reaches the preset multiple grid aggregation level K, so as to obtain a K-fold-level coarse grid map, as shown in fig. 5, the aggregation process is ended, and K may be set to 3.
As shown in fig. 6, the present embodiment is a mesh aggregation apparatus for fluid dynamics simulation, the apparatus comprising:
the acquisition module is used for acquiring the grid type in the initial fine grid graph of the object to be detected and the topological adjacency relation of the fine grids;
and the aggregation module is used for aggregating the initial fine grid graph according to the grid type and the topological adjacency relation to obtain a coarse grid.
Optionally, the obtaining module is configured to:
acquiring an initial fine grid map of the object to be detected;
obtaining the anisotropic grid and the isotropic grid according to the initial fine grid graph;
and obtaining the topological adjacency relation of the anisotropic mesh according to the anisotropic mesh.
Optionally, the aggregation module is configured to:
obtaining a grid unit set according to the anisotropic grid and the topological adjacency relation of the anisotropic grid; constructing a plurality of implicit lines on the anisotropic grid, wherein the implicit lines are uniformly distributed along the normal direction of the object plane from the object plane of the object to be detected to form the grid unit set with a plurality of grid units;
aggregating the grid units of the grid unit set according to a preset aggregation ratio M to form a coarse grid; and aggregating every M grid units to form the coarse grid, wherein M is a natural number which is not zero.
Optionally, the aggregation module is configured to:
traversing the anisotropic grid and determining a first grid unit; the first grid unit comprises points on the object plane of the object to be detected, and has a pushing plane, and all points of the pushing plane are not on the object plane of the object to be detected;
obtaining the first grid unit set according to the first grid unit and the topological adjacency relation of the opposite-type grid;
constructing the implicit line in the first grid unit set from the advancing surface until the advancing surface is a boundary surface, and stopping constructing the implicit line;
and obtaining the grid unit set with a plurality of grid units according to the implicit line.
Optionally, the aggregation module is to:
determining an Nth of the first grid cells of the first set of grid cells, wherein N is a non-zero natural number;
acquiring a grid unit to be confirmed, wherein the topological adjacent relation of the opposite-type grid with the Nth first grid unit is a grid adjacent relation;
if the grid cell to be confirmed is not in the first grid cell set and has a marking surface, and the point of the marking surface is not on the pushing surface of the Nth first grid cell, the grid cell to be confirmed is taken as the (N + 1) th first grid cell into the first grid cell set, and the order of taking the grid cell into the first grid cell set is marked;
taking the marked surface as the pushing surface after the grid unit to be confirmed is brought into the first grid unit set;
repeating the steps from the determining the Nth first grid cell of the first grid cell set to the step of incorporating the mark surface as the grid cell to be confirmed into the advancing surface of the first grid cell set until the grid cell no longer has the mark surface.
Optionally, the aggregation module is configured to:
acquiring an inclusion order of the first grid unit for inclusion in the first grid unit set;
acquiring a construction sequence of the implicit line constructed in the first grid unit set according to the inclusion sequence;
and aggregating the grid units of the grid unit set according to the construction sequence and the preset aggregation ratio N to form a coarse grid.
Fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the present application. On the hardware level, the electronic device comprises a processor and optionally an internal bus, a network interface and a memory. The Memory may include a Memory, such as a Random-Access Memory (RAM), and may further include a non-volatile Memory, such as at least 1 disk Memory. Of course, the electronic device may also include hardware required for other services.
The processor, the network interface, and the memory may be connected to each other via an internal bus, which may be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, an EISA (Extended Industry Standard Architecture) bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one double-headed arrow is shown in FIG. 7, but this does not indicate only one bus or one type of bus.
And the memory is used for storing the execution instruction. In particular, a computer program that can be executed by executing instructions. The memory may include both memory and non-volatile storage and provides execution instructions and data to the processor.
In a possible implementation manner, the processor reads corresponding execution instructions from the nonvolatile memory into the memory and then executes the execution instructions, and corresponding execution instructions can also be obtained from other devices so as to form a grid aggregation method for the fluid dynamics simulation on a logic level. The processor executes the execution instructions stored in the memory to implement a mesh aggregation method for fluid dynamics simulation provided in any embodiment of the present application through the executed execution instructions.
The method executed by the grid aggregation method for fluid dynamics simulation according to the embodiment shown in fig. 1 of the present application may be applied to or implemented by a processor. The processor may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be performed by integrated logic circuits of hardware in a processor or by instructions in the form of software. The Processor may be a general-purpose Processor, including a Central Processing Unit (CPU), a Network Processor (NP), and the like; but also Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or other Programmable logic devices, discrete Gate or transistor logic devices, discrete hardware components. The various methods, steps, and logic blocks disclosed in the embodiments of the present application may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The steps of the method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in a memory, and a processor reads information in the memory and completes the steps of the method in combination with hardware of the processor.
The present application further provides a readable storage medium storing executable instructions, which when executed by a processor of an electronic device, enable the electronic device to perform a mesh aggregation method for fluid dynamics simulation provided in any embodiment of the present application, and in particular to perform the above-mentioned mesh aggregation method for fluid dynamics simulation.
The electronic device described in the foregoing embodiments may be a computer.
It will be apparent to those skilled in the art that embodiments of the present application may be provided as a method or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects.
The embodiments in the present application are described in a progressive manner, and the same and similar parts among the embodiments can be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, as for the apparatus embodiment, since it is substantially similar to the method embodiment, the description is relatively simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (6)
1. A mesh aggregation method for fluid dynamics simulation for calculating aerodynamic properties of an object under test, the method comprising:
acquiring the grid type in the initial fine grid graph of the object to be detected and the topological adjacency relation of the fine grid;
aggregating the initial fine grid graph according to the grid type and the topological adjacency relation to obtain a coarse grid;
the mesh types include anisotropic meshes and isotropic meshes;
the aggregating the initial fine grid graph according to the grid type and the topological adjacency relation to obtain a coarse grid includes:
obtaining a grid unit set according to the anisotropic grid and the topological adjacency relation of the anisotropic grid; constructing a plurality of implicit lines on the anisotropic grid, wherein the implicit lines are uniformly distributed along the normal direction of the object plane from the object plane of the object to be detected to form the grid unit set with a plurality of grid units;
aggregating the grid units of the grid unit set according to a preset aggregation ratio M to form a coarse grid; wherein, every M grid units are aggregated to form one coarse grid, and M is a natural number which is not zero;
the obtaining a grid cell set according to the anisotropic grid and the anisotropic grid topological adjacency relation includes:
traversing the anisotropic grid and determining a first grid unit; the first grid unit comprises points on the object surface of the object to be detected, and is provided with a propelling surface, and all points of the propelling surface are not on the object surface of the object to be detected;
obtaining the first grid unit set according to the first grid unit and the topological adjacency relation of the opposite-type grid;
starting to construct the implicit line in the first grid unit set from the push surface, and stopping constructing the implicit line until the push surface is a boundary surface;
and obtaining the grid unit set with a plurality of grid units according to the implicit line.
2. The mesh aggregation method for fluid dynamics simulation of claim 1, wherein the mesh topological adjacency relationships comprise heterogeneous mesh topological adjacency relationships; obtaining the grid type and the grid topological adjacency relation in the initial fine grid graph of the object to be measured, including:
acquiring an initial fine grid map of the object to be detected;
obtaining the anisotropic grid and the isotropic grid according to the initial fine grid map;
and obtaining the topological adjacency relation of the anisotropic mesh according to the anisotropic mesh.
3. The method of claim 1, wherein the heterogeneous mesh topological adjacency includes a mesh adjacency, and the deriving the first set of mesh cells from the first mesh cell and the topological adjacency comprises:
determining an Nth of the first grid cells of the first set of grid cells, wherein N is a non-zero natural number;
acquiring a grid unit to be confirmed, wherein the topological adjacent relation of the opposite-type grid with the Nth first grid unit is a grid adjacent relation;
if the grid cell to be confirmed is not in the first grid cell set and has a marking surface, and the point of the marking surface is not on the pushing surface of the Nth first grid cell, the grid cell to be confirmed is taken as the (N + 1) th first grid cell into the first grid cell set, and the order of taking the grid cell into the first grid cell set is marked;
taking the marked surface as the pushing surface after the grid unit to be confirmed is brought into the first grid unit set;
repeating the steps from the determining the Nth first grid cell of the first grid cell set to the step of incorporating the mark surface as the grid cell to be confirmed into the first grid cell set until the grid cell to be confirmed no longer has the mark surface.
4. The method of claim 3, wherein the aggregating the grid cells of the grid cell set according to a preset aggregation ratio M to form a coarse grid comprises:
acquiring an inclusion order of the first grid unit for inclusion in the first grid unit set;
acquiring a construction sequence of the implicit line constructed in the first grid unit set according to the inclusion sequence;
and aggregating the grid cells of the grid cell set according to the construction sequence and the preset aggregation ratio M to form a coarse grid.
5. The method of claim 1, wherein the aggregating the initial fine grid graph according to the grid type and the topological adjacency relation to obtain a coarse grid, further comprises:
constructing a sparse map for the isotropic mesh;
and aggregating the grid units of the sparse graph by adopting a multilevel graph partitioning algorithm to form a coarse grid.
6. A mesh aggregation apparatus for fluid dynamics simulation, the apparatus comprising:
the acquisition module is used for acquiring the grid type in the initial fine grid graph of the object to be detected and the topological adjacency relation of the fine grid, wherein the grid type comprises an anisotropic grid and an isotropic grid;
the aggregation module is used for aggregating the initial fine grid graph according to the grid type and the topological adjacency relation to obtain a coarse grid;
the aggregation module is configured to:
obtaining a grid unit set according to the anisotropic grid and the topological adjacency relation of the anisotropic grid; constructing a plurality of implicit lines on the anisotropic grid, wherein the implicit lines are uniformly distributed along the normal direction of the object plane from the object plane of the object to be detected to form the grid unit set with a plurality of grid units;
aggregating the grid units of the grid unit set according to a preset aggregation ratio M to form a coarse grid; wherein, every M grid units are aggregated to form one coarse grid, and M is a natural number which is not zero;
the aggregation module is configured to: traversing the anisotropic grid and determining a first grid unit; the first grid unit comprises points on the object plane of the object to be detected, and has a pushing plane, and all points of the pushing plane are not on the object plane of the object to be detected;
obtaining the first grid unit set according to the first grid unit and the topological adjacency relation of the opposite-type grid;
constructing the implicit line in the first grid unit set from the advancing surface until the advancing surface is a boundary surface, and stopping constructing the implicit line;
and obtaining the grid unit set with a plurality of grid units according to the implicit line.
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