A method for comprehensive optimization of aerodynamic stealth and leading edge radius of a flying wing aircraft

Abstract

The present invention belongs to the technical field of multidisciplinary optimization of aircraft aerodynamic stealth, and discloses a method for comprehensive optimization of the aerodynamic stealth of the leading edge radius of a flying wing layout aircraft, comprising S1, drawing a surface structure grid of the flying wing layout aircraft; S2, parameterizing the surface structure grid by adopting a guide line contour line method; S3, giving a curve of the variation law of the leading edge radius of the flying wing layout along the span direction; S4, drawing an aerodynamic calculation grid and a stealth calculation grid of the initial shape of the flying wing layout; S5, establishing a mapping relationship between an aerodynamic calculation surface grid, a stealth calculation surface grid and a parameterized surface structure grid by adopting a mapping linkage method; S6, after the parameterized grid is deformed, obtaining aerodynamic calculation and stealth calculation surface grid points according to the mapping relationship in S5, and performing aerodynamic stealth calculation, thereby completing the comprehensive optimization of the aerodynamic stealth of the leading edge radius of the flying wing layout aircraft; the present invention realizes the parameterization of the leading edge radius of the flying wing layout aircraft and carries out comprehensive optimization of the aerodynamic stealth.

Description

Technical Field

[0001] The present invention relates to the technical field of multidisciplinary optimization of aircraft aerodynamic stealth, and in particular to a method for comprehensive optimization of the aerodynamic stealth of the leading edge radius of a flying wing layout aircraft. Background Art

[0002] For flying wing aircraft, the leading edge radius is an important parameter affecting the aerodynamic and stealth performance of the aircraft. The leading edge radius of the flying wing aircraft not only affects the pitch moment matching of the flying wing layout and the separation characteristics at large angles of attack, but also has an important impact on the forward radar scattering area (RCS).

[0003] A crucial step in the multidisciplinary optimization of the aerodynamic stealth characteristics of flying-wing aircraft is the parameterization of their shape. While the leading edge radius parameter is relatively simple for two-dimensional airfoils, for three-dimensional aircraft, modifying the shape according to a specified leading edge radius variation pattern and generating both aerodynamic and stealth analysis grids is a complex process that is difficult to automate, limiting the application of quantitative analysis and multidisciplinary optimization of the leading edge radius across the entire aircraft. Currently, sensitivity analyses of leading edge shape to aerodynamic stealth characteristics have only been conducted for airfoils; no research has examined the impact of spanwise variations in the leading edge radius on the aerodynamic stealth characteristics of a flying-wing aircraft configuration. Summary of the Invention

[0004] The present invention aims to provide a method for comprehensive optimization of the aerodynamic stealth of the leading edge radius of a flying wing layout aircraft, realize the parameterization of the leading edge radius of the flying wing layout aircraft, and carry out comprehensive optimization of the aerodynamic stealth.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for comprehensive optimization of the aerodynamic stealth of the leading edge radius of a flying wing layout aircraft comprises the following steps:

[0007] S1. Draw the surface structure grid of the flying wing layout aircraft:

[0008] Given the initial shape of a flying wing aircraft, meshing software is used to draw a surface structure mesh. During the meshing process, the i direction is along the flow field, and the j direction is along the span of the aircraft. A leading edge line is used to divide the flying wing aircraft into two parts, the upper and lower surfaces. This leading edge line is composed of the leading edge points of the local airfoil along the span. The upper and lower surfaces are meshed as two regions, with similar distribution of points behind the leading edge. This makes the i-direction mesh approximately parallel to the fuselage axis, and the mesh file is output.

[0009] S2. Use the guide line contour method to parameterize the surface structure mesh:

[0010] According to the j-direction lines of the upper and lower surface grids drawn in S1, which are approximately parallel to the fuselage axis, they are considered to be local airfoil lines. The CST method is used to parameterize this line. The mathematical expression of a curve expressed by the CST method is:

[0011]

[0012] Where, is the type function. Different N1 and N2 determine the curve type. When N1 = 0.5 and N2 = 1, the curve has a round head and a round tail. When N1 = 1 and N2 = 1, the curve has a pointed head and a pointed tail. ψ is the dimensionless chord length coordinate, ζ is the T is the airfoil trailing edge thickness term, S(ψ) is the shape function, which is defined by Bernstein polynomials, and its mathematical expression is:

[0013]

[0014] S r，n (ψ)=K r，n ×ψ r (1-ψ) n-r

[0015]

[0016] Where A r is the shape parameter, n is the order of Bernstein polynomial, and the type parameters N1 = 0.5, N2 = 1, and the shape parameter A r As the optimization variable, the optimization method is used to search for the parameters that are most balanced with the curve. The relationship between the leading edge radius and the shape parameter A0 is as follows:

[0017]

[0018] Obtain the curve of the leading edge radius of the flying wing layout changing along the span direction;

[0019] S3, given the wing layout leading edge radius along the span direction of the variation curve:

[0020] Given a flying wing layout with multiple spanwise positions, the leading edge radius of the middle point is obtained by spline interpolation of the given position and leading edge radius; the relationship between the leading edge radius and the shape parameter A0 in S2 is used get Calculate the A0 parameter value of the CST curve of the occupied airfoil, replace the original A0, calculate the coordinates of the corresponding position of the airfoil again, find the difference with the original airfoil coordinates, and superimpose them on the original curve coordinates. The mathematical expression for the replacement is:

[0021] xyz new =xyz old +(CST new -CSTold )

[0022] After the spanwise operation is completed, the surface structure grid of the leading edge radius of the wing layout design is obtained;

[0023] S4. Draw the aerodynamic calculation grid and stealth calculation grid of the initial shape of the flying wing layout;

[0024] S5. Use the mapping linkage method to establish the mapping relationship between the aerodynamic calculation surface grid, the stealth calculation surface grid and the parameterized surface structure grid:

[0025] Traverse the surface grid points of aerodynamic and stealth disciplines, find out where the point is located in a grid cell of the parameterized structural grid, and use the area proportional coefficient method to obtain the proportional relationship between the four intersection points of the quadrilateral cell and the grid point;

[0026] S6. After the parameterized grid is deformed, the surface grid points for aerodynamic calculation and stealth calculation are obtained according to the mapping relationship in S5, and aerodynamic stealth calculation is performed, thereby completing the comprehensive optimization of the aerodynamic stealth of the leading edge radius of the flying wing layout aircraft.

[0027] Furthermore, in S1, the surface structure network is drawn using the meshing software PointWise, and the final output mesh is a plot3d format file.

[0028] Furthermore, in S5, the area ratio coefficient is calculated as follows:

[0029]

[0030]

[0031]

[0032]

[0033] The mapping coordinates of the point to be mapped in the quadrilateral are expressed as:

[0034] P t '=P1×k1+P2×k2+P3×k3+P4×k4

[0035] Where p1, p2, p3, and p4 are the coordinates of the four points of the quadrilateral, a1, a2, a3, and a4 are the areas of the triangle formed by the mapped point and two of the points, and Pt is the mapping coordinate.

[0036] The beneficial effects of the technical solution are:

[0037] The method provided by the present invention can realize the deformation of the leading edge radius of a flying wing layout aircraft according to a given value, and obtain the deformed aerodynamic calculation grid and stealth calculation grid. It can be used to study the influence of the leading edge radius on the aerodynamic and stealth characteristics, and can be used for the comprehensive optimization of the leading edge radius distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flow chart of a comprehensive optimization method for aerodynamic stealth of the leading edge radius of a flying wing layout aircraft according to the present invention;

[0039] Figure 2 This is an example diagram of the surface structure grid of a flying wing layout aircraft according to a method for comprehensive optimization of the leading edge radius of a flying wing layout aircraft of the present invention;

[0040] Figure 3 A partial diagram of a surface structure grid example of a flying wing layout aircraft according to a method for comprehensive optimization of the leading edge radius of a flying wing layout aircraft of the present invention;

[0041] Figure 4 A distribution diagram of the leading edge radius of a flying wing layout aircraft obtained by optimal matching of a flying wing layout aircraft leading edge radius aerodynamic stealth comprehensive optimization method according to the present invention;

[0042] Figure 5 A distribution diagram of a given leading edge radius of a flying wing layout aircraft leading edge radius aerodynamic stealth comprehensive optimization method according to the present invention;

[0043] Figure 6 A comparison diagram of the changed leading edge radius and the original grid of a method for comprehensive optimization of the leading edge radius of a flying wing layout aircraft according to the present invention;

[0044] Figure 7 This is a comparison diagram of the changed leading edge radius of the head and the original grid in a comprehensive aerodynamic stealth optimization method for the leading edge radius of a flying wing layout aircraft according to the present invention;

[0045] Figure 8 This is a comparison diagram of the wing tip leading edge radius after change and the original grid in a comprehensive aerodynamic stealth optimization method for the leading edge radius of a flying wing layout aircraft according to the present invention;

[0046] Figure 9 A spatial grid diagram of a flying wing layout aircraft aerodynamic analysis calculation grid for a flying wing layout aircraft leading edge radius aerodynamic stealth comprehensive optimization method of the present invention;

[0047] Figure 10 A physical surface grid diagram of a flying wing layout aircraft aerodynamic analysis calculation grid for a flying wing layout aircraft leading edge radius aerodynamic stealth comprehensive optimization method of the present invention;

[0048] Figure 11A grid diagram for calculating stealth analysis of a flying wing layout aircraft according to a method for comprehensively optimizing the leading edge radius of a flying wing layout aircraft according to the present invention;

[0049] Figure 12 This is a schematic diagram of the relationship between the judgment points and the positions of the quadrilateral grid units in a comprehensive aerodynamic stealth optimization method for the leading edge radius of a flying wing layout aircraft according to the present invention. DETAILED DESCRIPTION

[0050] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0051] like Figures 1 to 12 As shown, a method for comprehensive optimization of the aerodynamic stealth of the leading edge radius of a flying wing layout aircraft includes the following steps:

[0052] S1. Draw the surface structure grid of the flying wing layout aircraft:

[0053] Given the initial shape of a flying-wing aircraft, the surface structure mesh is drawn using the meshing software PointWise. During the meshing process, the i direction is along the flow field, and the j direction is along the span of the aircraft. A leading edge line is used to divide the flying-wing aircraft into upper and lower surfaces. This leading edge line is composed of the leading edge points of the local airfoil along the span. The upper and lower surfaces are meshed separately, with the points behind the leading edge distributed similarly, so that the i-direction mesh is approximately parallel to the fuselage axis. The mesh is output as a plot3d format file.

[0054] S2. Use the guide line contour method to parameterize the surface structure mesh:

[0055] According to the j-direction lines of the upper and lower surface grids drawn in S1, which are approximately parallel to the fuselage axis, they are considered to be local airfoil lines. The CST method is used to parameterize this line. The mathematical expression of a curve expressed by the CST method is:

[0056]

[0057] Where, is the type function. Different N1 and N2 determine the curve type. When N1 = 0.5 and N2 = 1, the curve has a round head and a round tail. When N1 = 1 and N2 = 1, the curve has a pointed head and a pointed tail. ψ is the dimensionless chord length coordinate, ζ is the T is the airfoil trailing edge thickness term, S(ψ) is the shape function, which is defined by Bernstein polynomials, and its mathematical expression is:

[0058]

[0059] S r，n (ψ)=K r，n ×ψ r (1-ψ) n-r

[0060]

[0061] Where A r is the shape parameter, n is the order of Bernstein polynomial, and the type parameters N1 = 0.5, N2 = 1, and the shape parameter A r As the optimization variable, the optimization method is used to search for the parameters that are most balanced with the curve. The relationship between the leading edge radius and the shape parameter A0 is as follows:

[0062]

[0063] Obtain the curve of the leading edge radius of the flying wing layout changing along the span direction;

[0064] S3, given the wing layout leading edge radius along the span direction of the variation curve:

[0065] Given a flying wing layout with multiple spanwise positions, the leading edge radius of the middle point is obtained by spline interpolation of the given position and leading edge radius; the relationship between the leading edge radius and the shape parameter A0 in S2 is used get Calculate the A0 parameter value of the CST curve of the occupied airfoil, replace the original A0, calculate the coordinates of the corresponding position of the airfoil again, find the difference with the original airfoil coordinates, and superimpose them on the original curve coordinates. The mathematical expression for the replacement is:

[0066] xyz new =xyz old +(CST new -CST old )

[0067] After the spanwise operation is completed, the surface structure grid of the leading edge radius of the wing layout design is obtained;

[0068] S4. Draw the aerodynamic calculation grid and stealth calculation grid of the initial shape of the flying wing layout;

[0069] S5. Use the mapping linkage method to establish the mapping relationship between the aerodynamic calculation surface grid, the stealth calculation surface grid and the parameterized surface structure grid:

[0070] Traverse the surface grid points of aerodynamic and stealth disciplines, find the point located in a grid unit of the parameterized structural grid, and use the area ratio coefficient method to obtain the proportional relationship between the four intersection points of the quadrilateral unit and the grid point; the area ratio coefficient is calculated as follows:

[0071]

[0072]

[0073]

[0074]

[0075] The mapping coordinates of the point to be mapped in the quadrilateral are expressed as:

[0076] P t '=P1×k1+P2×k2+P3×k3+P4×k4

[0077] Where p1, p2, p3, and p4 are the coordinates of the four points of the quadrilateral, a1, a2, a3, and a4 are the areas of the triangle formed by the mapped point and two of the points, and Pt is the mapping coordinate;

[0078] The specific steps of the mapping linkage method are:

[0079] A1 Prepare the initial aircraft shape subject analysis model and background mesh model:

[0080] Given the initial shape of the aircraft, meshing software is used to create initial shape analysis models for the aerodynamics and stealth disciplines, respectively. The stealth discipline uses a surface triangular mesh, while the aerodynamic discipline uses an unstructured spatial mesh. The object surface meshes are then extracted and the surface structural meshes of the aircraft's pseudo-deformable components are drawn as the background mesh.

[0081] A2. Establish the mapping relationship between the surface grid of the subject analysis model and the background grid. The surface grid of the aerodynamic and stealth subject analysis model consists of disordered grid points and the connection relationship between grid points. The mapping relationship between the grid points and the background grid is established by:

[0082] A2.1. Calculate the center point of the background grid quadrilateral element;

[0083] A2.2. Organize all the center points obtained in A2.1 into a KD tree to facilitate searching;

[0084] A2.3. Search the KD numbers for the nearest center points to the point to be mapped, and find the quadrilateral elements corresponding to the center points.

[0085] A2.4. Use the boundary judgment method to determine whether the point to be mapped is within the rectangular space formed by the maximum and minimum three-coordinate values ​​of all points in the quadrilateral, and find all quadrilaterals that contain the mapping point.

[0086] A2.5. When the number of quadrilateral elements containing the mapping point is 0, the point to be mapped is considered not on the background grid. When the number of quadrilateral elements containing the mapping point is 1, the scale factor of the point to be mapped in the quadrilateral element is calculated. The scale factor is the proportion of the contribution of the four points in the quadrilateral element to the coordinates of the point to be mapped. When the number of quadrilateral elements containing the mapping point is greater than 1, the scale factor of each element is calculated and used to calculate the mapping point. The mapping relationship between the mapping point and the element with the smallest scale factor is taken as the mapping relationship for that point.

[0087] A3. After the background grid is parametrically deformed, the coordinates of the mapped points are obtained by multiplying the background grid and the scale coefficients of each point and summing them up. This is used to update the coordinates of the subject model surface grid to obtain a new subject model surface grid.

[0088] A4. The aerodynamics analysis model uses the spring method to propagate the surface mesh deformation to the spatial mesh for aerodynamic analysis of the new shape. The stealth analysis model directly uses the new surface mesh as the subject model, thus forming a mapping linkage between different subject analysis models.

[0089] S6. After the parameterized grid is deformed, the surface grid points for aerodynamic calculation and stealth calculation are obtained according to the mapping relationship in S5, and aerodynamic stealth calculation is performed, thereby completing the comprehensive optimization of the aerodynamic stealth of the leading edge radius of the flying wing layout aircraft.

[0090] The above is only an embodiment of the present invention, and common knowledge such as the specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A method for comprehensive optimization of the leading edge radius and aerodynamic stealth of a flying wing aircraft, characterized by: The following steps are involved: S1. Draw the surface structure grid of the flying wing layout aircraft: S2. Use the guide line contour method to parameterize the surface structure mesh: According to the j-direction lines of the upper and lower surface grids drawn in S1, which are approximately parallel to the fuselage axis, they are considered to be the local airfoil lines. The lines are parameterized using the CST method to obtain the curve of the leading edge radius of the flying wing layout along the span direction. S3, given the wing layout leading edge radius along the span direction of the variation curve: Given a flying wing layout with multiple spanwise positions, the leading edge radius of the middle point is obtained by spline interpolation of the given position and leading edge radius; using the relationship between the leading edge radius and the shape parameter A0 get Calculate the A0 parameter value of the CST curve of the occupied airfoil, replace the original A0, calculate the coordinates of the corresponding position of the airfoil again, find the difference with the original airfoil coordinates, and superimpose them on the original curve coordinates. The mathematical expression for the replacement is: xyz new =xyz old +(CST new -CST old ); After the spanwise operation is completed, the surface structure grid of the leading edge radius of the wing layout design is obtained; S4. Draw the aerodynamic calculation grid and stealth calculation grid of the initial shape of the flying wing layout; S5. Use the mapping linkage method to establish the mapping relationship between the aerodynamic calculation surface grid, the stealth calculation surface grid and the parameterized surface structure grid: Traverse the surface grid points of aerodynamic and stealth disciplines, find the grid cell containing the point in the parameterized structural grid, and obtain the proportional relationship between the four vertices of the quadrilateral cell and the grid point by the area proportional coefficient method; The specific steps of the mapping linkage method are: A1 Prepare the initial aircraft shape subject analysis model and background mesh model: A2. Establish a mapping relationship between the object surface grid of the subject analysis model and the background grid. The object surface grid of the aerodynamic and stealth subject analysis model consists of disordered grid points and the connection relationship between grid points. Establish a mapping relationship between the grid points and the background grid; A3. After the background grid is parametrically deformed, the coordinates of the mapped points are obtained by multiplying the background grid and the scale coefficients of each point and summing them up. This is used to update the coordinates of the subject model surface grid to obtain a new subject model surface grid. A4. The aerodynamics analysis model uses the spring method to propagate the surface mesh deformation to the spatial mesh for aerodynamic analysis of the new shape. The stealth analysis model directly uses the new surface mesh as the subject model, thus forming a mapping linkage between different subject analysis models. S6. After the parameterized grid is deformed, the surface grid points for aerodynamic calculation and stealth calculation are obtained according to the mapping relationship in S5, and aerodynamic stealth calculation is performed, thereby completing the comprehensive optimization of the aerodynamic stealth of the leading edge radius of the flying wing layout aircraft.

2. The method for comprehensive optimization of the leading edge radius and aerodynamic stealth of a flying wing layout aircraft according to claim 1, characterized in that: In S1, the surface structure network is drawn using the meshing software PointWise, and the final output mesh is a plot3d format file.

3. The method for comprehensive optimization of the leading edge radius and aerodynamic stealth of a flying wing layout aircraft according to claim 1, characterized in that: In S5, the area ratio coefficient is calculated as: ； The mapping coordinates of the point to be mapped in the quadrilateral are expressed as: P t =P1×k1+P2×k2+P3×k3+P4×k4 Where P1, P2, P3, and P4 are the coordinates of the four points of the quadrilateral, a1, a2, a3, and a4 are the areas of the triangle formed by the mapped point and two of the points, and P t is the mapping coordinate.

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