阅读说明：本技术 基于无网格法的高精度几何模型粒子离散方法、装置及系统 (High-precision geometric model particle dispersion method, device and system based on gridless method ) 是由 孙中国 王�锋 席光 于 2021-09-09 设计创作，主要内容包括：本发明公开了一种基于无网格法的高精度几何模型粒子离散方法、装置及系统,将三维几何模型通过多组面网格进行离散,提取网格节点并生成多个单层壁面粒子,定义法向光滑角度为评判标准,构建可视化离散误差分布图,根据误差图应用变尺度粒子局部嵌套加密技术,在较短的周期内得到精度高且计算资源消耗少的壁面粒子模型。本发明可视化离散精度评估方法可具体有效的指导加密位置以及加密程度,结合先粗后细的离散方案,缩短了建立高精度壁面粒子模型的时间周期；局部嵌套加密技术克服了传统加密技术较难实现相邻网格模块之间的网格加密突跃的困难,可将局部结构进行独立加密并与其他结构直接组合,实现薄壁结构的高精度离散与法向量的准确计算。(The invention discloses a high-precision geometric model particle discretization method, device and system based on a meshless method. The visual discrete precision evaluation method can specifically and effectively guide the encryption position and the encryption degree, and shortens the time period for establishing the high-precision wall particle model by combining a coarse-then-fine discrete scheme; the local nested encryption technology overcomes the difficulty that the traditional encryption technology is difficult to realize the mesh encryption leap between adjacent mesh modules, can independently encrypt the local structure and directly combine the local structure with other structures, and realizes the high-precision dispersion of the thin-wall structure and the accurate calculation of a normal vector.)

1. The high-precision geometric model particle dispersion method based on the gridless method is characterized by comprising the following steps of:

step 1: carrying out a plurality of groups of surface grid discrete processing on the three-dimensional geometric model, extracting grid nodes and correspondingly generating a wall surface particle model;

step 2: processing the wall surface particle model to obtain a discrete precision numerical value and a discrete error distribution diagram;

and step 3: observing a plurality of groups of single-resolution discrete error graphs, dividing the components and determining the resolution required by each component;

and 4, step 4: independently dispersing the three-dimensional geometric models of the components by using surface grids with different resolutions to obtain particle models with different resolutions;

and 5: splicing the particle models with different resolutions to obtain a multi-resolution particle model;

step 6: carrying out data processing on the multi-resolution particle model, importing a discrete precision evaluation program, and acquiring an error distribution map and a discrete precision numerical value;

and 7: judging whether the required discrete precision is achieved or not according to the error distribution map and the discrete precision numerical value, and if so, executing a step 8; if not, adopting high-resolution discretization and local nesting for the part with insufficient precision, and repeating the steps 4, 5, 6 and 7;

and 8: and outputting a new wall surface particle model.

2. The method for discretizing particles of geometric model with high precision based on meshless method according to claim 1, wherein the number of unit sizes of each of the plurality of sets of surface meshes in step 1 is different, and before performing a plurality of sets of surface mesh discretization processing on the three-dimensional geometric model, the method further comprises: the number of sizes for the grid cell is determined, generating a size sequence.

3. The method for high-precision geometric model particle dispersion based on the meshless method of claim 1, wherein the surface mesh is an unstructured triangular mesh, and the mesh unit size is smaller than the fluid particle diameter.

4. The method for discretizing the particles of the high-precision geometric model based on the meshless method according to claim 1, wherein the step 2 of processing the wall particle model to obtain a discretization precision value and a discretization error distribution map comprises the following steps: and performing wall particle normal vector calculation on the wall particle model, and introducing particle data containing normal vectors into a discrete precision evaluation program to obtain a discrete precision numerical value and a discrete error distribution diagram.

5. The method for high-precision geometric model particle dispersion based on the meshless method of claim 2, wherein the wall particle normal vector calculation method is based on local surface fitting and adopts MESHLAB software for calculation.

6. The improved gridless particle method-based numerical simulation method for a centrifugal pump according to claim 1, wherein said discrete accuracy assessment method is based on a normal smooth angle, and the normal smooth angle of the wall particle i is calculated by the following formula:

wherein n is_iIs the normal vector of the i particle; n is_ikSearching a normal vector of a nearest wall surface particle in the k-th searching direction around the i particle; d is the number of search directions; outputting the spatial position of each particle and expressing the NSA value by color distribution to obtain a dispersion error distribution diagram; NSA is expressed as normal smooth angle;

the discrete accuracy of the model was calculated by taking the standard deviation of the NSA value for each wall particle:

wherein the content of the first and second substances,the average value of the normal smooth angle of the wall particles.

7. The method for high-precision geometric model particle dispersion based on the gridless method according to claim 1, wherein the local nesting is to adopt a component with insufficient high-resolution dispersion precision to obtain a new wall particle model meeting precision requirements, only the component with insufficient dispersion precision in step 7 is retained in the new wall particle model, the rest particles are deleted, and the component high-resolution particle data is nested with the component with sufficient precision in step 7 to obtain the partially nested encrypted wall particle model.

8. The high-precision geometric model particle dispersion system based on the gridless method is characterized by comprising the following steps:

the first processing module is used for carrying out a plurality of groups of surface grid discrete processing on the three-dimensional geometric model, extracting grid nodes and correspondingly generating a wall surface particle model;

the second processing module is used for processing the wall surface particle model to obtain a discrete precision numerical value and a discrete error distribution diagram;

the dividing module is used for observing a plurality of groups of single-resolution discrete error graphs, dividing the components and determining the resolution required by each component;

the discrete module is used for independently dispersing the three-dimensional geometric models of all the parts by applying surface grids with different resolutions to obtain particle models with different resolutions;

the splicing module is used for splicing the particle models with different resolutions to obtain a multi-resolution particle model;

the third processing module is used for carrying out data processing on the multi-resolution particle model, importing a discrete precision evaluation program and obtaining an error distribution map and a discrete precision numerical value;

the judging module is used for judging whether the required discrete precision is achieved according to the error distribution map and the discrete precision numerical value; if not, adopting high-resolution dispersion and local nesting for the part with insufficient precision;

and the output module is used for outputting a new wall surface particle model.

9. A terminal device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the steps of the method according to any of claims 1-7 when executing the computer program.

10. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 7.

Technical Field

The invention belongs to the field of geometric model particle dispersion, and relates to a high-precision geometric model particle dispersion method, device and system based on a gridless method.

Background

The meshless method is based on a fluid particle concept, adopts discrete particles without a fixed topological relation to replace meshes and nodes under a Lagrange framework, is suitable for calculating the flow with extremely large deformation, does not need to carry out block processing on a flow domain, can integrally disperse a model and integrally solve a flow field, and has great potential in the field of engineering problem flow field calculation; however, three-dimensional modeling of complex shapes is one of the difficulties restricting the application of a non-grid particle method to practical engineering problems, most of geometric models targeted by the existing research are regular and do not have sharp-angled or thin-walled structures, the used wall surface boundaries are all three layers of wall surface particles, and the inner wall surface particles participate in pressure calculation, but for the engineering problems of complex revolution surfaces, sharp angles and slender twisted blades, such as internal flow simulation of fluid machinery, the traditional method is difficult to directly arrange, and particle number density loss caused by insufficient arrangement precision can also cause non-physical phenomena such as particle penetration and the like; a single-layer wall model based on a distance function is commonly used for a discrete complex geometric wall, but the direct introduction of the distance function easily causes severe fluctuation of the pressure of fluid particles near the wall, so that the stability of calculation is influenced; in addition, the wall function is difficult to accurately compensate the lack of the particle number density in the three-dimensional situation, and the boundary particles participating in the pressure calculation are easy to increase the calculation amount.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a high-precision geometric model particle discretization method, device and system based on a gridless method.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a high-precision geometric model particle dispersion method based on a gridless method comprises the following steps:

step 1: carrying out a plurality of groups of surface grid discrete processing on the three-dimensional geometric model, extracting grid nodes and correspondingly generating a wall surface particle model;

step 2: processing the wall surface particle model to obtain a discrete precision numerical value and a discrete error distribution diagram;

and step 3: observing a plurality of groups of single-resolution discrete error graphs, dividing the components and determining the resolution required by each component;

and 4, step 4: independently dispersing the three-dimensional geometric models of the components by using surface grids with different resolutions to obtain particle models with different resolutions;

and 5: splicing the particle models with different resolutions to obtain a multi-resolution particle model;

step 6: carrying out data processing on the multi-resolution particle model, importing a discrete precision evaluation program, and acquiring an error distribution map and a discrete precision numerical value;

and 7: judging whether the required discrete precision is achieved or not according to the error distribution map and the discrete precision numerical value, and if so, executing a step 8; if not, adopting high-resolution discretization and local nesting for the part with insufficient precision, and repeating the steps 4, 5, 6 and 7;

and 8: and outputting a new wall surface particle model.

The invention is further improved in that:

in step 1, the unit sizes and numbers of each group of surface meshes in the plurality of groups of surface meshes are different, and the method further comprises the following steps before the discrete processing of the plurality of groups of surface meshes is carried out on the three-dimensional geometric model: the number of sizes for the grid cell is determined, generating a size sequence.

The surface mesh is an unstructured triangular mesh, and the mesh unit size is smaller than the diameter of the fluid particles.

Processing the wall surface particle model in the step 2 to obtain a discrete precision value and a discrete error distribution diagram, wherein the discrete precision value and the discrete error distribution diagram comprise the following steps: and performing wall particle normal vector calculation on the wall particle model, and introducing particle data containing normal vectors into a discrete precision evaluation program to obtain a discrete precision numerical value and a discrete error distribution diagram.

The wall particle normal vector calculation method is based on local surface fitting and adopts MESHLAB software to calculate.

The discrete precision evaluation method is based on a normal smooth angle, and the normal smooth angle of the wall surface particle i is calculated by the following formula:

wherein n is_iIs the normal vector of the i particle; n is_ikSearching a normal vector of a nearest wall surface particle in the k-th searching direction around the i particle; d is the number of search directions; outputting the spatial position of each particle and expressing the NSA value by color distribution to obtain a dispersion error distribution diagram; NSA is expressed as normal smooth angle;

the discrete accuracy of the model was calculated by taking the standard deviation of the NSA value for each wall particle:

wherein the content of the first and second substances,the average value of the normal smooth angle of the wall particles.

And local nesting is to adopt a part with insufficient high-resolution discrete precision to obtain a new wall particle model meeting the precision requirement, only the part with insufficient discrete precision in the step 7 is reserved in the new wall particle model, the rest particles are deleted, and the part high-resolution particle data is nested with the part with the precision in the step 7 to obtain the wall particle model after local nesting encryption.

A high-precision geometric model particle dispersion system based on a gridless method comprises the following steps:

the first processing module is used for carrying out a plurality of groups of surface grid discrete processing on the three-dimensional geometric model, extracting grid nodes and correspondingly generating a wall surface particle model;

the second processing module is used for processing the wall surface particle model to obtain a discrete precision numerical value and a discrete error distribution diagram;

the dividing module is used for observing a plurality of groups of single-resolution discrete error graphs, dividing the components and determining the resolution required by each component;

the discrete module is used for independently dispersing the three-dimensional geometric models of all the parts by applying surface grids with different resolutions to obtain particle models with different resolutions;

the splicing module is used for splicing the particle models with different resolutions to obtain a multi-resolution particle model;

the third processing module is used for carrying out data processing on the multi-resolution particle model, importing a discrete precision evaluation program and obtaining an error distribution map and a discrete precision numerical value;

the judging module is used for judging whether the required discrete precision is achieved according to the error distribution map and the discrete precision numerical value; if not, adopting high-resolution dispersion and local nesting for the part with insufficient precision;

and the output module is used for outputting a new wall surface particle model.

A terminal device comprising a memory, a processor and a computer program stored in said memory and executable on said processor, said processor implementing the steps of the above method when executing said computer program.

A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the above-mentioned method.

Compared with the prior art, the invention has the following beneficial effects:

the wall modeling method is suitable for any complex three-dimensional geometric model, is convenient and quick, and realizes the flow field calculation of the gridless particle method of any geometry.

The visual discrete precision evaluation method can specifically and effectively guide the encryption position and the encryption degree, and greatly shortens the time period for establishing the high-precision wall particle model by combining a discrete scheme of firstly thickening and then thinning.

The local nested encryption technology of the invention overcomes the difficulty that the traditional encryption technology is difficult to realize the mesh encryption leap between adjacent mesh modules, can independently encrypt the local structure and directly combine the local structure with other structures, and realizes the high-precision dispersion of the thin-wall structure and the accurate calculation of the normal vector.

Drawings

In order to more clearly explain the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a schematic flow chart of a high-precision geometric model particle discretization method based on a gridless method according to the present invention;

FIG. 2 is a geometric model diagram of a discrete impeller;

FIG. 3 is a schematic diagram of wall particle modeling;

FIG. 4 is a graph of 6 sets of single resolution discretized error contrast profiles;

wherein a is an error distribution diagram of a particle dispersion impeller with the resolution of 0.6;

b is an error distribution diagram of a particle dispersion impeller with the resolution of 0.4;

c is an error distribution diagram of a particle dispersion impeller with the resolution of 0.3;

d is an error distribution diagram of a particle dispersion impeller with the resolution of 0.2;

e is an error distribution diagram of a particle dispersion impeller with the resolution of 0.1;

f is an error distribution diagram of a particle dispersion impeller with the resolution of 0.08;

FIG. 5 is a schematic diagram of a process for constructing a multi-resolution wall particle model;

FIG. 6 is a graph of error distribution for a multi-resolution wall particle model;

FIG. 7 is a schematic structural diagram of a high-precision geometric model particle discretization system based on a gridless method.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. 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 invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. are used for indicating the orientation or positional relationship based on the orientation or positional relationship shown in the drawings or the orientation or positional relationship which is usually arranged when the product of the present invention is used, the description is merely for convenience and simplicity, and the indication or suggestion that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, cannot be understood as limiting the present invention. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.

Furthermore, the term "horizontal", if present, does not mean that the component is required to be absolutely horizontal, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the description of the embodiments of the present invention, it should be further noted that unless otherwise explicitly stated or limited, the terms "disposed," "mounted," "connected," and "connected" should be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

The invention is described in further detail below with reference to the accompanying drawings:

referring to fig. 1, fig. 1 discloses a high-precision geometric model particle discretization method based on a gridless method, which includes:

step 1, determining the size number of grid cells for preliminary calculation, and adopting 6 sets of single-resolution surface grids for discretization of an impeller model shown in fig. 2, wherein the generated size sequence is [0.6, 0.4, 0.3, 0.2, 0.1 and 0.08 ]; the size for preliminary dispersion is related to a specific model, but the minimum size is required to obtain an overall high-precision particle model; the larger the number of the initial division sizes is, the easier the local precision required by each part is to be established in the subsequent steps, and the smaller the number of the particles required by the constructed multi-resolution wall surface particle model is, the higher the precision is.

Step 2, sequentially dispersing the geometric models by using the surface grids with the sizes of the above 6 groups and correspondingly generating particle models; taking the bullet geometry as an example, the principle of dispersion is shown in fig. 3; performing wall surface particle normal vector calculation on the 6 obtained particle models by using MESHLAB software; and then introducing the particle data containing the normal vector into a discrete precision evaluation program to obtain discrete precision numerical values of each model, referring to table 1, wherein table 1 is the discrete precision data of each model, and expressing the normal smooth angle numerical value of each wall particle by using color and describing the position of each particle in space to obtain a discrete error distribution diagram, as shown in fig. 4, the deeper the color is, the smaller the normal smooth angle is, and the higher the discrete precision is.

TABLE 1 discrete precision data for each model

Step 3, observing a plurality of groups of single-resolution discrete error graphs, dividing the components and determining the resolution required by each component; firstly, dividing the component according to a dispersion error distribution diagram, as shown in fig. 4, wherein profiles with similar curvatures can present similar colors in the diagram; accordingly, the impeller can be divided into 4 parts: 1. the molded surface of the front cover plate and the rear cover plate of the impeller, which are close to the outlet side, and an inlet pipeline; 2. the molded surface of the front cover plate and the rear cover plate of the impeller, which is close to the inlet side; 3. the top of the hub is provided with a large fillet and a blade; 4. a small fillet curved surface and a side wall surface of the blade; then determining the discrete precision of each part according to the target precision of the required integral model, wherein the target precision is determined according to specific calculation conditions; for example, the color is marked with the discrete accuracy of the small corner surface at the particle scale of 0.08 as the target accuracy; for the part 1, when the discrete precision is 0.6, the color of the part is darker than that of the mark, as shown in a in fig. 4, which shows that when the particle discrete part 1 with the resolution of 0.6 is adopted, the wall surface particle model of the part is obtained to reach the required target precision; for the other 3 parts, the required resolution is judged by adopting the same method; the resolution required for the available part 2 is 0.4; the required resolution of the part 3 is 0.3; the required resolution of the component 4 is 0.08; the impeller geometric model is dispersed into particles according to the particle size, and the required multi-resolution particle model can be obtained after splicing, wherein the splicing process is as shown in fig. 5, and the impeller geometric model, the geometric models of the impeller parts, the multi-resolution particle models of the impeller parts and the multi-resolution particle models of the impeller are sequentially arranged from left to right in fig. 5.

Step 4, calculating the wall surface particle normal vector of the multi-resolution particle model,and introducing a discrete precision evaluation program to output an error distribution map and discrete precision, as shown in FIG. 6, the discrete precision is 3.37 × 10^-2The total number of wall particles is 438386, and the precision of single-scale particles is 3.43X 10^-2The desired wall particle count is 700105.

And 5, outputting the established high-precision wall surface particle model.

Referring to fig. 7, fig. 7 discloses a high-precision geometric model particle discretization system based on the gridless method, which includes:

the first processing module is used for carrying out a plurality of groups of surface grid discrete processing on the three-dimensional geometric model, extracting grid nodes and correspondingly generating a wall surface particle model;

the second processing module is used for processing the wall surface particle model to obtain a discrete precision numerical value and a discrete error distribution diagram;

the dividing module is used for observing a plurality of groups of single-resolution discrete error graphs, dividing the components and determining the resolution required by each component;

the dispersion module is used for independently dispersing the three-dimensional geometric models of all the parts by applying surface grids with different resolutions to obtain particle models with different resolutions;

the splicing module is used for splicing the particle models with different resolutions to obtain a multi-resolution particle model;

the third processing module is used for processing data of the multi-resolution particle model, importing a discrete precision evaluation program and acquiring an error distribution map and a discrete precision numerical value;

the judging module is used for judging whether the required discrete precision is achieved or not according to the error distribution map and the discrete precision numerical value; if not, adopting high-resolution dispersion and local nesting for the part with insufficient precision;

and the output module outputs the new wall surface particle model.

An embodiment of the present invention provides a schematic diagram of a terminal device. The terminal device of this embodiment includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. The processor realizes the steps of the above-mentioned method embodiments when executing the computer program. Alternatively, the processor implements the functions of the modules/units in the above device embodiments when executing the computer program.

The computer program may be partitioned into one or more modules/units that are stored in the memory and executed by the processor to implement the invention.

The terminal device can be a desktop computer, a notebook, a palm computer, a cloud server and other computing devices. The terminal device may include, but is not limited to, a processor, a memory.

The processor may be a Central Processing Unit (CPU), other general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, etc.

The memory may be used for storing the computer programs and/or modules, and the processor may implement various functions of the terminal device by executing or executing the computer programs and/or modules stored in the memory and calling data stored in the memory.

The terminal device integrated modules/units, if implemented in the form of software functional units and sold or used as separate products, may be stored in a computer readable storage medium. Based on such understanding, all or part of the flow of the method according to the embodiments of the present invention may also be implemented by a computer program, which may be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method embodiments may be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, usb disk, removable hard disk, magnetic disk, optical disk, computer memory, Read-only memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution medium, etc. It should be noted that the computer readable medium may contain content that is subject to appropriate increase or decrease as required by legislation and patent practice in jurisdictions, for example, in some jurisdictions, computer readable media does not include electrical carrier signals and telecommunications signals as is required by legislation and patent practice.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.