CN103337097A - Multiple Cartesian grid generation method applicable to LBM) - Google Patents
Multiple Cartesian grid generation method applicable to LBM) Download PDFInfo
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- CN103337097A CN103337097A CN2013102745620A CN201310274562A CN103337097A CN 103337097 A CN103337097 A CN 103337097A CN 2013102745620 A CN2013102745620 A CN 2013102745620A CN 201310274562 A CN201310274562 A CN 201310274562A CN 103337097 A CN103337097 A CN 103337097A
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Abstract
The invention discloses a multiple Cartesian grid generation method applicable to LBM (lattice Boltzmann method). The method can be used for generating multiple Cartesian grids for the interior or exterior of any complex geometric object and comprises the following steps: A, setting the parameters of the multiple Cartesian grids according to the requirement of a user; B, calculating to generate the coarsest single lattices, judging the position of the center of each grid unit relative to the object by a ray method, deleting the grid unit if the center of the grid unit is positioned in the object, and calculating the distance from the center of the grid unit to the periphery of the object if the center of the grid unit is positioned on the periphery of the object, wherein the distance is to be used in the LBM; C, densifying the grids from the surface of the object layer by layer, judging the position of each generated sub-grid unit relative to the object, deleting the sub-grid unit if the sub-grid unit is positioned in the object, calculating the distance from the center of the sub-grid unit to the periphery of the object if the sub-grid unit is positioned on the periphery of the object, and finally searching to form the neighbor information of the sub-grid unit. Through the steps, the multiple Cartesian grids are formed eventually.
Description
Technical field
The present invention relates to Fluid Mechanics Computation and computer realm, proposed to be applicable to the multiple cartesian grid generation method of lattice Boltzmann method.
Background technology
Lattice Boltzmann method (Lattice Boltzmann Method, LBM) be particle rapidity to be distributed be separated into limited several values, between the grid node, simulate the solution that to press the Navier-Stokes equation along moving of limited velocity reversal with collision process by molecule.LBM is simple because of its algorithm, counting yield is high, concurrency good and can conveniently handle advantage such as complicated boundary condition is subjected to extensive concern, and development is very rapid for over ten years recently.On the one hand, use LBM and obtained success in a lot of fields, comprise that complicated turbulent flow, polyphasic flow, reaction are flowed, flowing in aerodynamic noise, phase interface and phase transformation, the porous medium, heat transfer free convection, have the flowing of the flowing of Free Surface, high Knudsen number, the prediction of mutually soluble liquids coefficient of diffusion, unstable state to flow etc.On the other hand, LBM also has very big progress on numerical simulation disposal route and skill, as the processing of the processing of random geometry, complicated boundary condition, non-ly divide equally grid and stability analysis etc.But, because negative value appears in the existing equilibrium state density fonction under the flow at high speed situation, can't guarantee the stability of LBM form, therefore use LBM and calculate the compressible mobile bigger difficulty that has.
In recent years, another kind of computing method based on the BGK model of being set out by the Boltzmann equation have been developed.Its basic thought is the Boltzmann equation from statistical physics, and wherein collision term adopts the BGK model to simplify, and sets up the difference scheme of macroscopic quantity based on this, is called gas dynamics BGK form (Gas-Kinetic BGK Scheme).This method flows at chemical reaction, heterogeneously flow, rarefied gaseous flow, compressiblely flow, obtained application in water wave motion and the magnetic fluid.These application show that this method has abundant physical connotation, can solve some complicated flow field problems, but this method are bigger to the calculated amount of three-dimensional problem.
Along with the development of LBM method, it is used also more and more widely, but this method need be used a kind of computing grid that is called cartesian grid.At present, yet there are no the generation software of the cartesian grid that is applicable to the LBM method of maturation, only occurred in large commercial software for calculation PowerFLOW, very necessary invention is applicable to the cartesian grid generation method of LBM method for this reason.
Summary of the invention
The objective of the invention is to, a kind of cartesian grid generation method of the LBM of being applicable to method is provided in order to address the above problem, this method can or outsidely generate multiple cartesian grid to the inside of the object of any complex geometry, avoided to carry out a concrete simple objects limitation of mesh generation in the past, be that method can adapt to the object of complex geometry well, thereby have higher adaptability.
For achieving the above object, design of the present invention is: if outflow calculating, at first with a zoning object is surrounded, and with the thickest size of mesh opening mesh generation is carried out in this zone and (calculate if carry out interior flowmeter, just directly interior of articles is carried out subdivision, this patent is only set forth to the situation of outflow in the back, interior stream repeats no more), then grid element center is positioned at the grid deletion of interior of articles, begin grid is encrypted from body surface layer by layer at last, finally form multiple cartesian grid.
According to the foregoing invention design, for the zoning of an object outside, the present invention adopts following technical proposals:
A, the parameter of multiple cartesian grid is set according to customer requirements; The trellis-type of LBM method (as D3Q15, D3Q19 or D3Q27 etc.), size of mesh opening, grid tuple and the grid number of plies etc.;
B, calculating generate the thickest substance grid, and utilize rays method to judge the relative position of grid cell center and object, if just delete this grid cell in inside, if on the object boundary the computing grid unit center to the distance (this distance will be used in the LBM method) on border, the neighbor information of generating mesh;
C, successively make up multi grid from coarse to fine by encrypting: begin grid is encrypted from body surface layer by layer, the sub-grid unit that generates also needs to judge the relative position with object, if just delete this sub-grid unit in inside, if on object boundary then calculate the sub-grid unit center to the distance on border, final search forms the neighbor information of sub-grid, finally forms new one heavy cartesian grid.
The multiple cartesian grid generation method that is applicable to lattice Boltzmann method of the present invention is compared with existing grid generation technique, has following outstanding substantive distinguishing features and remarkable advantage:
1. the multiple cartesian grid of this method foundation is applicable to the grid cell type of various LBM methods, and having avoided in the past, the LBM method does not have special-purpose grid maker;
2. this method can adopt parallel mesh generation at each computing node of trunking computer, and having avoided in the past, mesh generation all is to transmit each computing node then at a node;
3. after the present invention having been arranged, when the Flow Field Calculation of carrying out in the future, can carry out adaptive refinement to local grid according to the Flow Field Calculation result.
Description of drawings
Fig. 1 is the process flow diagram that is applicable to the multiple cartesian grid generation method of lattice Boltzmann method of the present invention.
Fig. 2 is the described particular flow sheet that the last layer grid is encrypted of step C among Fig. 1.
Fig. 3 is the described process flow diagram that a grid cell is encrypted of C2 among Fig. 2.
Fig. 4 is the geometric shape of wing body assembly of the test of concrete embodiment.
Fig. 5 is the partial result figure of the final multiple cartesian grid that generates of the present invention.
Embodiment
Below in conjunction with accompanying drawing the preferred embodiments of the present invention are further described.
Embodiment one:
Referring to Fig. 1, originally be applicable to the multiple cartesian grid generation method of lattice Boltzmann method, it is characterized in that: can be to inside or the outside multiple cartesian grid that is applicable to lattice Boltzmann method that generates of the object of any complex geometry; The concrete operations step is as follows:
A, the parameter of multiple cartesian grid is set according to customer requirements: trellis-type D3Q15, the D3Q19 of lattice Boltzmann method or D3Q27, size of mesh opening, grid tuple and the grid number of plies;
B, calculating generate the thickest substance grid, and utilize rays method to judge the relative position of grid cell center and object, if just delete this grid cell in inside, and if on object boundary the computing grid unit center to the distance on border, the neighbor information of generating mesh;
Successively make up multi grid from coarse to fine by encrypting: begin grid is encrypted from body surface layer by layer, the sub-grid unit that generates also needs to judge the relative position with object, if just delete this sub-grid unit in inside, if on object boundary then calculate the sub-grid unit center to the distance on border, final search forms the neighbor information of sub-grid, finally forms new one heavy cartesian grid.
Embodiment two:
Referring to Fig. 1-Fig. 3, present embodiment and embodiment one are basic identical, and special feature is as follows:
It is as follows that described step B calculates the concrete steps that generate the thickest substance grid:
B1, do a ray from unit center along certain direction, calculate the crossing number of times of this ray and body surface, be that even number shows that unit center is positioned at the object outside if intersect number of times, otherwise be positioned at inside;
B2, computing grid center be to the minimum distance of body surface, if this distance less than size of mesh opening then grid and body surface are crossing, otherwise non-intersect;
If the B3 grid element center is positioned at interior of articles and non-intersect with body surface, then delete this grid;
B4, according to the trellis-type of lattice Boltzmann method, search forms neighbours' unit information of grid.
Passing through described in the described step C encrypted the concrete grammar that successively makes up multi grid from coarse to fine:
C1, scanning the
nHeavy grid, the grid cell that intersects with body surface is encrypted, and the employing method identical with step B judged the position of the sub-grid unit that generates and handled, at last encrypted father unit is marked, the grid that is noted as encryption does not participate in calculating in the future in lattice Boltzmann method;
C2, repeatedly scan
nHeavy grid, the number of times of scanning is decided according to the grid number of plies that the user arranges, and the neighbours of the grid that is labeled as encryption are encrypted, and the sub-grid of Xing Chenging needn't be judged its position more like this;
C3, generate the th at last
n+ 1 heavy grid, search forms neighbours' unit information of sub-grid;
C4, repeating step C1-C3 successively form multiple cartesian grid.
Embodiment three:
In the present embodiment, originally be applicable to the multiple cartesian grid generation method of lattice Boltzmann method, adopt the C language compilation of standard, move under passable Windows and the (SuSE) Linux OS.
Geometric description for object adopts the stl file layout.The multiple cartesian grid generation method that is applicable to lattice Boltzmann method of the present invention as shown in Figure 1-Figure 3, may further comprise the steps:
The initialization of A, algorithm, concrete steps comprise:
A1, read the stl file of describing how much on object, the user arranges flow field regions;
A2, the trellis-type that the LBM method is set, size of mesh opening, grid tuple and the number of plies.
B, according to the mesh parameter that the user arranges, whole zoning is split into the thickest substance grid uniformly, and judges the position of the grid cell that subdivision goes out, concrete steps comprise:
B1, from unit center along certain direction (for example directions X) do a ray, calculate the crossing number of times of this ray and body surface, be that even number shows that unit center is positioned at the object outside if intersect number of times, otherwise be positioned at inside;
B2, computing grid center be to the minimum distance of body surface, if this distance less than size of mesh opening then grid and body surface are crossing, otherwise non-intersect;
If the B3 grid element center is positioned at interior of articles and non-intersect with body surface, then delete this grid;
B4, according to the trellis-type of LBM method, search forms neighbours' unit information of grid.
C, successively make up multi grid from coarse to fine by encrypting, concrete steps comprise:
C1, the heavy grid of scanning n, the grid cell that intersects with body surface is encrypted, and the employing method identical with step B judge the position of the sub-grid unit that generates and handle, at last encrypted father unit marked (grid that is noted as encryption does not participate in calculating future in the LBM method);
C2, repeatedly scan the heavy grid of n (number of times of scanning is decided according to the grid number of plies that the user arranges), the neighbours of the grid that is labeled as encryption are encrypted, the sub-grid of Xing Chenging needn't be judged its position more like this;
C3, generate the heavy grid of n+1 at last, search forms neighbours' unit information of sub-grid;
C4, repetition C1-C3 successively form multiple cartesian grid.
With reference to Fig. 4, show the geometric shape of the wing body assembly of the concrete embodiment of multiple cartesian grid generation method that is applicable to lattice Boltzmann method of the present invention.With reference to Fig. 5, show the design sketch of the final multiple cartesian grid that generates of the present invention.
This paper sets forth just for helping to understand method of the present invention and core concept in conjunction with Figure of description and specific embodiment.Method of the present invention is not limited to the embodiment described in the embodiment, and those skilled in the art belong to technological innovation scope of the present invention equally according to other embodiment that method of the present invention and thought draw.This description should not be construed as limitation of the present invention.
Claims (3)
1. be applicable to the multiple cartesian grid generation method of lattice Boltzmann method, it is characterized in that: can be to inside or the outside multiple cartesian grid that is applicable to lattice Boltzmann method that generates of the object of any complex geometry; The concrete operations step is as follows:
A, the parameter of multiple cartesian grid is set according to customer requirements: trellis-type D3Q15, the D3Q19 of lattice Boltzmann method or D3Q27, size of mesh opening, grid tuple and the grid number of plies;
B, calculating generate the thickest substance grid, and utilize rays method to judge the relative position of grid cell center and object, if just delete this grid cell in inside, and if on object boundary the computing grid unit center to the distance on border, the neighbor information of generating mesh;
C, successively make up multi grid from coarse to fine by encrypting: begin grid is encrypted from body surface layer by layer, the sub-grid unit that generates also needs to judge the relative position with object, if just delete this sub-grid unit in inside, if on object boundary then calculate the sub-grid unit center to the distance on border, final search forms the neighbor information of sub-grid, finally forms new one heavy cartesian grid.
2. the multiple cartesian grid generation method that is applicable to lattice Boltzmann method according to claim 1 is characterized in that, it is as follows that described step B calculates the concrete steps that generate the thickest substance grid:
B1, do a ray from unit center along certain direction, calculate the crossing number of times of this ray and body surface, be that even number shows that unit center is positioned at the object outside if intersect number of times, otherwise be positioned at inside;
B2, computing grid center be to the minimum distance of body surface, if this distance less than size of mesh opening then grid and body surface are crossing, otherwise non-intersect;
If the B3 grid element center is positioned at interior of articles and non-intersect with body surface, then delete this grid;
B4, according to the trellis-type of lattice Boltzmann method, search forms neighbours' unit information of grid.
3. the multiple cartesian grid generation method that is applicable to lattice Boltzmann method according to claim 1 is characterized in that, passing through described in the described step C encrypted the concrete grammar that successively makes up multi grid from coarse to fine and be:
C1, scanning the
nHeavy grid, the grid cell that intersects with body surface is encrypted, and the employing method identical with step B judged the position of the sub-grid unit that generates and handled, at last encrypted father unit is marked, the grid that is noted as encryption does not participate in calculating in the future in lattice Boltzmann method;
C2, repeatedly scan
nHeavy grid, the number of times of scanning is decided according to the grid number of plies that the user arranges, and the neighbours of the grid that is labeled as encryption are encrypted, and the sub-grid of Xing Chenging needn't be judged its position more like this;
C3, generate the th at last
n+ 1 heavy grid, search forms neighbours' unit information of sub-grid;
C4, repeating step C1-C3 successively form multiple cartesian grid.
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| CN109712178A (en) * | 2017-10-23 | 2019-05-03 | 上海汽车集团股份有限公司 | A kind of grid model hole inspection method and device |
| CN112992294A (en) * | 2021-04-19 | 2021-06-18 | 中国空气动力研究与发展中心计算空气动力研究所 | Porous medium LBM calculation grid generation method |
| CN115564925A (en) * | 2022-11-21 | 2023-01-03 | 广州中望龙腾软件股份有限公司 | Grid generation method based on B-rep model and Cartesian grid slices |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109712178A (en) * | 2017-10-23 | 2019-05-03 | 上海汽车集团股份有限公司 | A kind of grid model hole inspection method and device |
| CN109712178B (en) * | 2017-10-23 | 2022-06-14 | 上海汽车集团股份有限公司 | Method and device for inspecting pores of grid model |
| CN112992294A (en) * | 2021-04-19 | 2021-06-18 | 中国空气动力研究与发展中心计算空气动力研究所 | Porous medium LBM calculation grid generation method |
| CN115564925A (en) * | 2022-11-21 | 2023-01-03 | 广州中望龙腾软件股份有限公司 | Grid generation method based on B-rep model and Cartesian grid slices |
| CN115564925B (en) * | 2022-11-21 | 2024-04-16 | 广州中望龙腾软件股份有限公司 | Grid generation method based on B-rep model and Cartesian grid slice |
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Application publication date: 20131002 |