阅读说明：本技术 一种基于结构化网格的目标粗糙表面生成方法 (Target rough surface generation method based on structured grid ) 是由 高伟 林嘉轩 廖意 朱丽丽 霍熠炜 于 2021-09-14 设计创作，主要内容包括：本发明提供一种基于结构化网格的目标粗糙表面生成方法,包括：步骤S1、建立确定起伏高度、确定相关长度的功率谱密度函数的粗糙面模型；步骤S2、对目标的模型开展结构化网格剖分,计算每个点处的法向矢量；步骤S3、根据结构化网格的特点,获取点坐标之间的关联关系,形成点坐标关联关系矩阵；步骤S4、选取结构化网格的参考点,计算所有点坐标在其相应表面上与参考点之间的沿两个网格节点编号方向上的相对距离；步骤S5、以粗糙面模型为基础数据,采用拉格朗日插值方法计算曲面上每个点的起伏,沿法向矢量方向与目标的结构化网格矢量叠加形成目标粗糙表面。本发明生成的目标粗糙表面包含完整的粗糙面信息,保证了生成方法的精确性和有效性。(The invention provides a target rough surface generation method based on structured grids, which comprises the following steps: step S1, establishing a rough surface model for determining the height of fluctuation and the power spectral density function of the correlation length; step S2, carrying out structured grid subdivision on the target model, and calculating a normal vector at each point; s3, acquiring incidence relations among the point coordinates according to the characteristics of the structured grid, and forming a point coordinate incidence relation matrix; step S4, selecting a reference point of the structured grid, and calculating the relative distance between the coordinates of all points on the corresponding surface and the reference point along the numbering direction of the two grid nodes; and step S5, calculating the fluctuation of each point on the curved surface by adopting a Lagrange interpolation method based on the rough surface model, and superposing the fluctuation with the structured grid vector of the target along the normal vector direction to form the rough surface of the target. The target rough surface generated by the invention contains complete rough surface information, and the accuracy and the effectiveness of the generation method are ensured.)

1. A method for generating a target rough surface based on a structured grid is characterized by comprising the following steps:

step S1, establishing a rough surface model of a power spectral density function for determining the height of fluctuation and the correlation length according to actual requirements;

step S2, carrying out structured grid subdivision on the target model, and calculating a normal vector at each point;

s3, acquiring incidence relations among the point coordinates according to the characteristics of the structured grid, and forming a point coordinate incidence relation matrix;

and step S4, selecting reference points of the structured grid, and calculating the relative distance between the coordinates of all points on the corresponding surfaces and the reference points along the numbering direction of the two grid nodes.

And S5, calculating the fluctuation of each point on the curved surface by adopting a Lagrange interpolation method according to the relative distance between each point and a reference point on the curved surface by taking the rough surface model generated in the step S1 as basic data, and overlapping the rough surface model with the structured grid vector of the target along the normal vector direction to form the rough surface of the target.

2. The method for generating a target rough surface based on a structured grid according to claim 1, wherein in step S1, the gaussian distribution rough surface model is generated by performing two-dimensional fourier transform on a power spectral density function, and the expression of the gaussian power spectral density function is:

wherein σ_zRoot mean square height of the roughened surface, L_cxAnd L_cyThe relative lengths of the matte in the x and y directions, respectively.

3. The method for generating a target rough surface based on a structured grid according to claim 1, wherein the step S2 of dividing the structured grid using the ICEM software comprises geometric model cleaning, Block creation, mapping, grid node number definition and grid 5 generation.

4. The method for generating a target rough surface based on a structured grid according to claim 1, wherein in step S2, the unit normal vector at each point isCalculated according to the following expression:

wherein S is_uAnd S_vIs the unit tangent of the point along the numbering direction of the two grid nodes.

5. The method of claim 1, wherein the set range of the subdivision size of the structured grid is λ/8- λ/5, λ representing the operating wavelength.

6. The method for generating a target rough surface based on a structured grid as claimed in claim 1, wherein in step S3, the points in the structured grid are obviously connected in a back-and-forth manner, and the point sequence numbers are mapped into a two-dimensional matrix along the node numbering directions of the two grids to obtain the point coordinate association matrix.

7. The method for generating a target rough surface based on a structured grid as claimed in claim 1, wherein in step S4, a center point of a certain surface of the target is selected as a reference point, and each point P on the surface is calculated one by one_ijRelative distance d to reference point along the numbering direction of two grid nodes_x、d_y：

In the formula (x)₀,y₀,z₀) Representing point P_ijIs determined by the coordinate of (a) in the space, sequentially represents a point sequence in the numbering direction of the nodes of the grid, sequentially representing the point sequence in the numbering direction of the nodes of another grid.

8. The method for generating a target rough surface based on a structured grid according to claim 7, wherein the step S5, calculating the undulation of each point on the curved surface by using the lagrange interpolation method, comprises:

calculating the fluctuation of each point on the curved surface by adopting the following two-dimensional Lagrange interpolation polynomial;

in the formula, h (x)_i,y_j) For the coordinate point (x) in the rough surface model of step S1_i,y_j) Height of undulation of (d), m₁、m₂The number of points in the x and y directions in the rough surface model in step S1, as a function of Lagrangian interpolation, z (d)_x,d_y) As a coordinate point P_ijThe interpolated height of (c).

9. The method for generating a target rough surface based on a structured grid according to claim 8, wherein the step S5, forming the target rough surface by superimposing the structured grid vectors of the target along the normal vector direction, comprises:

interpolating along the normal vector direction of the points, the expression of the points on the target rough surface is:

in the formula, the coordinates are,representing the normal vector at point (x, y, z) on the target model.

Technical Field

The invention relates to the technical field of radar target characteristic simulation, in particular to a target rough surface generation method based on a structured grid.

Background

The electromagnetic scattering property of the radar target has a close and inseparable relationship with geometric modeling and electromagnetic modeling. When the frequency of the electromagnetic wave is in a sub-millimeter wave band or even higher, the smooth surface in the microwave band is not smooth any more, and the influence caused by the rough characteristic is not negligible.

Therefore, a method for generating a target rough surface containing complete rough surface information is needed to be provided, so that a closed loop on a simulation modeling level is realized, and effective input is provided for calculation of the scattering characteristics of the submillimeter wave band.

Disclosure of Invention

The invention aims to provide a target rough surface generation method based on a structured grid, which is based on the establishment of a traditional rough surface and is superimposed with the interpolation vector of the structured grid of a target along the normal vector direction, so that the target rough surface comprises complete rough surface information, and the accuracy and the effectiveness of the generation method are ensured.

In order to achieve the above purpose, the invention is realized by the following technical scheme:

a method for generating a target rough surface based on a structured grid, comprising:

step S1, establishing a rough surface model of a power spectral density function for determining the height of fluctuation and the correlation length according to actual requirements;

step S2, carrying out structured grid subdivision on the target model, and calculating a normal vector at each point;

s3, acquiring incidence relations among the point coordinates according to the characteristics of the structured grid, and forming a point coordinate incidence relation matrix;

and step S4, selecting reference points of the structured grid, and calculating the relative distance between the coordinates of all points on the corresponding surfaces and the reference points along the numbering direction of the two grid nodes.

And S5, calculating the fluctuation of each point on the curved surface by adopting a Lagrange interpolation method according to the relative distance between each point and a reference point on the curved surface by taking the rough surface model generated in the step S1 as basic data, and overlapping the rough surface model with the structured grid vector of the target along the normal vector direction to form the rough surface of the target.

Further, in step S1, the gaussian distribution rough surface model is generated by performing two-dimensional fourier transform on a power spectral density function, where the expression of the gaussian power spectral density function is:

wherein σ_zRoot mean square height of the roughened surface, L_cxAnd L_cyThe relative lengths of the matte in the x and y directions, respectively.

Further, in step S2, the step of dividing the structured grid using the ICEM software includes 5 links of geometric model cleaning, Block creation, mapping relationship establishment, grid node number definition, and grid generation.

Further, in the step S2, the unit normal vector at each point isCalculated according to the following expression:

wherein S is_uAnd S_vIs the unit tangent of the point along the numbering direction of the two grid nodes.

Furthermore, the setting range of the subdivision size of the structured grid is lambda/8-lambda/5, and lambda represents the working wavelength.

Further, in step S3, the points in the structured grid are obviously linked, and the point sequence numbers are mapped into a two-dimensional matrix along the numbering direction of the two grid nodes, so as to obtain the point coordinate association relationship matrix.

Further, the method can be used for preparing a novel materialIn step S4, a center point of a certain curved surface of the target is selected as a reference point, and each point P on the curved surface is calculated one by one_ijRelative distance d to reference point along the numbering direction of two grid nodes_x、d_y：

In the formula (x)₀，y₀，z₀) Representing point P_ijIs determined by the coordinate of (a) in the space, sequentially represents a point sequence in the numbering direction of the nodes of the grid, sequentially representing the point sequence in the numbering direction of the nodes of another grid.

Further, in step S5, calculating the fluctuation of each point on the curved surface by using a lagrange interpolation method includes:

calculating the fluctuation of each point on the curved surface by adopting the following two-dimensional Lagrange interpolation polynomial;

in the formula, h (x)_i，y_j) Is composed of a main body and a lower bodyStep S1 coordinate points (x) in the rough surface model_i，y_j) Height of undulation of (d), m₁、m₂The number of points in the x and y directions in the rough surface model in step S1, as a function of Lagrangian interpolation, z (d)_x，d_y) As a coordinate point P_ijThe interpolated height of (c).

Further, in step S5, the forming the target rough surface by superimposing the structured grid vectors of the target along the normal vector direction includes:

interpolating along the normal vector direction of the points, the expression of the points on the target rough surface is:

in the formula, the coordinates are,representing the normal vector at point (x, y, z) on the target model.

Compared with the prior art, the invention has the following advantages:

the target rough surface established by the invention comprises rough surface complete parameters such as fluctuation variance, correlation length, power spectral density function and the like.

According to the invention, the target surface structured grid and the traditional random rough surface are organically superposed to form the target rough surface with relevant characteristics, so that the most basic research input is provided for researching the submillimeter wave band simulation modeling.

The traditional random rough surface generation method comprises rough surface completion parameters such as fluctuation variance, correlation length and power spectral density function.

The invention fully utilizes the characteristics of the structured grid and organizes the split point coordinates according to a topological mode. However, the unstructured grid subdivision is adopted, the correlation relationship arrangement between point coordinates needs to be carried out, and meanwhile, the unstructured grid relates to very complex and troublesome geodesic distance calculation in the process of calculating the relative coordinates between the point coordinates and the reference points. And the distance in the subdivision direction is simply and approximately utilized by adopting the structured grid, so that the requirement on modeling precision can be met.

For the target model with the extremely large number of grid points, a parallel Lagrange interpolation mode can be adopted to accelerate the calculation, and the interpolation mode has the characteristic of linear acceleration.

Therefore, on the basis of establishing the traditional rough surface, the method is superimposed with the interpolation vector of the structured grid of the target along the normal vector direction, so that the target rough surface comprises complete rough surface information, and the accuracy and the effectiveness of the generation method are ensured.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the drawings used in the description will be briefly introduced, and it is obvious that the drawings in the following description are an embodiment of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts according to the drawings:

fig. 1 is a schematic flowchart of a method for generating a target rough surface based on a structured grid according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a rough surface model generation according to an embodiment of the present invention;

FIG. 3 is a schematic view of a structural grid of an airfoil according to an embodiment of the invention;

fig. 4 is a schematic diagram illustrating a local enlargement of an airfoil grid and parameters used in interpolation according to an embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the figures and the detailed description. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise scale for the purpose of facilitating and distinctly aiding in the description of the embodiments of the present invention. To make the objects, features and advantages of the present invention comprehensible, reference is made to the accompanying drawings. It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the implementation conditions of the present invention, so that the present invention has no technical significance, and any structural modification, ratio relationship change or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention.

The core idea of the invention is to provide a method for generating a target rough surface.

Referring to fig. 1, a method for generating a target rough surface based on a structured grid according to the present invention includes the following steps:

and step S1, establishing a rough surface model of the power spectral density function for determining the height of the fluctuation and the correlation length according to actual requirements.

Specifically, the rough surface model shown in fig. 2 is gaussian distributed and generated by performing two-dimensional fourier transform on a power spectral density function, where the expression of the gaussian power spectral density function is:

wherein σ_zRoot mean square height of the roughened surface, L_cxAnd L_cyThe relative lengths of the matte in the x and y directions, respectively.

And step S2, carrying out structured grid subdivision on the target model, and calculating a normal vector at each point.

Specifically, the structured mesh generation can be performed on the target model by using common mesh generation software such as ICEM. The ICEM software division of the structured grid comprises 5 links of geometric model cleaning, Block creation, mapping relation establishment, grid node number definition and grid generation, and the specific implementation method can refer to the prior art and is not described herein in detail.

Structured mesh division size the structured mesh division size is related to the operating wavelength λ and is typically set to λ/8 to λ/5. Fig. 3 shows an exemplary result of a structured meshing of the wing model.

Calculating a normal vector at each point, specifically: calculating a unit tangent S along the numbering direction of two grid nodes_uAnd S_vThen the unit normal vector is expressed as:

and step S3, acquiring the incidence relation among the point coordinates according to the characteristics of the structured grid, and forming a point coordinate incidence relation matrix.

The structured grid points are obviously connected in an anteroposterior mode, the point sequence numbers are mapped into a two-dimensional matrix form along the numbering directions of two grid nodes (namely the splitting direction in the step S2), and a point coordinate incidence relation matrix is obtained to prepare for calculating the relative distance in the step S4.

And step S4, selecting reference points of the structured grid, and calculating the relative distance between the coordinates of all points on the corresponding surfaces and the reference points along the numbering direction of the two grid nodes.

Specifically, as shown in fig. 4, a center point of a certain curved surface of the target is selected as a reference point, and each point P on the curved surface is calculated one by one_ijDistance d to reference point along the numbering direction of two grid nodes_x、d_y：

In the formula (x)₀，y₀，z₀) Representing point P_ijIs determined by the coordinate of (a) in the space, sequentially represents a point sequence in the numbering direction of the nodes of the grid, sequentially representing the point sequence in the numbering direction of the nodes of another grid.

Only point P is shown in FIG. 4_ijDistance d to reference point in the numbering direction (y-direction) of one grid node_y，d_yIs the sum of the distances between the point sequences in the mesh node numbering direction (y direction). Calculating a point P_ijDistance d to reference point in the numbering direction (x-direction) of another grid node_xThe principle of the method is the same, and the detailed description is omitted here.

And S5, calculating the fluctuation of each point on the curved surface by adopting a Lagrange interpolation method according to the relative distance between each point and a reference point on the curved surface by taking the rough surface model generated in the step S1 as basic data, and overlapping the rough surface model with the structured grid vector of the target along the normal vector direction to form the rough surface of the target.

Specifically, the following two-dimensional lagrange interpolation polynomial can be used to calculate the fluctuation of each point on the curved surface:

in the formula, h (x)_i，y_j) For the coordinate point (x) in the rough surface model of step S1_i，y_j) Height of undulation of (d), m₁、m₂The number of points in the x and y directions in the rough surface model in step S1, as a function of Lagrangian interpolation, z (d)_x，d_y) As a coordinate point P_ijThe interpolated height of (c).

Then, interpolating along the normal vector direction of the points, the expression of the points on the target rough surface is:

in the formula, the coordinates are,representing the normal vector at point (x, y, z) on the target model.

In summary, the present invention first uses a conventional fourier transform method to obtain the conventional rough surface fluctuation characteristics, then forms a structured grid of a target with the aid of common grid subdivision software, calculates a normal vector at each point, obtains an association relationship between point coordinates according to the characteristics of the structured grid, then selects a reference point of the structured grid, calculates the relative distance (in two division directions) between the reference point and each point coordinate on the corresponding surface of the point coordinates, and finally calculates the fluctuation of each point on a curved surface by using a lagrange interpolation method for the rough surface fluctuation characteristics generated in the first step, and superimposes the rough surface with the target structured grid vectors along the normal vector direction to form a target rough surface.

The target rough surface established by the invention comprises rough surface complete parameters such as fluctuation variance, correlation length, power spectral density function and the like. According to the invention, the target surface structured grid and the traditional random rough surface are organically superposed to form the target rough surface with relevant characteristics, so that the most basic research input is provided for researching the submillimeter wave band simulation modeling. The traditional random rough surface generation method comprises rough surface completion parameters such as fluctuation variance, correlation length and power spectral density function. The invention fully utilizes the characteristics of the structured grid and organizes the split point coordinates according to a topological mode. However, the unstructured grid subdivision is adopted, the correlation relationship arrangement between point coordinates needs to be carried out, and meanwhile, the unstructured grid relates to very complex and troublesome geodesic distance calculation in the process of calculating the relative coordinates between the point coordinates and the reference points. And the distance in the subdivision direction is simply and approximately utilized by adopting the structured grid, so that the requirement on modeling precision can be met. For the target model with the extremely large number of grid points, a parallel Lagrange interpolation mode can be adopted to accelerate the calculation, and the interpolation mode has the characteristic of linear acceleration. Therefore, on the basis of establishing the traditional rough surface, the method is superimposed with the interpolation vector of the structured grid of the target along the normal vector direction, so that the target rough surface comprises complete rough surface information, and the accuracy and the effectiveness of the generation method are ensured.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, 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. The term "comprising", without further limitation, means that the element so defined is not excluded from the group consisting of additional identical elements in the process, method, article, or apparatus that comprises the element.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.