Aeroelastic dynamic grid construction method oriented to SU2 format aerodynamic grid

Abstract

The invention relates to an aeroelastic dynamic grid construction method oriented to an SU2 format aerodynamic grid, belongs to the technical field of aeroelastic mechanics, and comprises the following steps: reading grid and deformation parameters of an SU2 format aerofoil aerodynamic grid model under working conditions, and obtaining coordinates of all grid nodes and deformation information of deformation points; before deformation calculation is started, an efficient greedy simplification method is adopted, part of nodes are selected from grid nodes to serve as supporting points of the aeroelastic dynamic grid, and low-dimensional radial basis function interpolation meeting the precision requirement is established according to displacement on the nodes. Constructing an interpolation matrix through a radial basis function, solving a deformation weight coefficient, obtaining deformation information of all nodes, recovering node connection information of the SU2 grid, and obtaining a finally deformed grid; the construction of grid deformation in efficient and high-precision aeroelastic analysis is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of aeroelasticity, and in particular to a method for constructing an aeroelasticity dynamic grid for an SU2 format aerodynamic grid, and in particular to a method for constructing an aeroelasticity dynamic grid for an SU2 format aerodynamic grid combined with a greedy simplification method. Background Art

[0002] Aeroelasticity mainly studies the coupling between aerodynamic force, elastic force and inertial force. The structure is deformed by aerodynamic loads, and the structural deformation will change the size and distribution of aerodynamic loads, which is a typical fluid-solid coupling problem. With the increasing requirements of modern aircraft for various performances such as flight time and speed, and the innovation and development of various new technologies and theories, aeroelastic design has gradually changed from passive verification to active design, becoming an indispensable part of the overall aircraft design process and playing an irreplaceable key role.

[0003] Given the key role of aeroelasticity in aircraft design, it is necessary to conduct a relatively accurate analysis of the deformation, load distribution and other issues of civil aircraft during the aeroelastic design stage. The solution of aerodynamic forces is one of the core issues in the aeroelastic calculation process. Thanks to the development of computational fluid dynamics (CFD) technology and the substantial improvement of computer performance, in recent years, CFD technology based on the transonic small perturbation equation, Euler equation or NS equation is increasingly being used in aeroelastic calculations to calculate aerodynamic forces. The CFD method starts from the basic flow equation, uses fewer assumptions, can effectively simulate the essential characteristics of the flow, and obtains a high accuracy in aerodynamic calculations. In the aeroelastic calculation process, structural deformation changes the topological structure of the flow field, and dynamic mesh technology needs to be used to realize the deformation of the solution domain. Therefore, dynamic mesh technology is a key technology in the study of aeroelastic calculations. The development of dynamic mesh technology with good versatility, high computational efficiency and strong applicability has always been a key area of ​​concern in the study of aeroelastic mechanics.

[0004] SU2 is an open source toolkit for computational fluid dynamics (CFD), structural analysis, heat transfer and chemical reactions. SU2 Mesh is a tool used in the SU2 software package to generate and process geometry and meshes. SU2 Mesh can handle a variety of physical problems, including fluid, structure, heat transfer, etc., multi-dimensional meshes, and supports the generation of one-dimensional, two-dimensional and three-dimensional meshes. SU2 is widely used in fluid dynamics simulation in the aerospace field and has good application prospects. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for constructing an aeroelastic dynamic grid for an SU2 format aerodynamic grid. The present invention reads the grid and deformation parameters of the SU2 format wing aerodynamic grid model under working conditions, and obtains the coordinates of all grid nodes and the deformation information of the deformation points. Before the deformation calculation begins, an efficient greedy simplification method is used to select some nodes from the grid nodes as support points of the aeroelastic dynamic grid, and a low-dimensional radial basis function interpolation that meets the accuracy requirements is established based on the displacements on these nodes. An interpolation matrix is ​​constructed through radial basis functions, and the deformation weight coefficient is solved to obtain the deformation information of all nodes. The node connection information of the SU2 grid is restored to obtain the final deformed grid; the construction of grid deformation in efficient and high-precision aeroelastic analysis is realized.

[0006] The present invention provides an aeroelastic dynamic grid construction method for SU2 format aerodynamic grids, comprising:

[0007] Step S1, using finite element software and an aerodynamic mesh file in SU2 format to establish an aerodynamic mesh model of a wing in SU2 format;

[0008] Obtain the coordinate points of each grid node in the SU2 format wing aerodynamic grid model, the connection information between each grid node, and the distinguishing information of each grid node;

[0009] Step S2, setting working conditions, deforming the wing aerodynamic mesh model in SU2 format based on the working conditions, and obtaining a deformed aerodynamic mesh, deformed mesh nodes, and deformation amounts of the deformed mesh nodes;

[0010] Performing three-dimensional spline curve interpolation in each deformed mesh node to obtain an interpolation point of each deformed mesh node;

[0011] Step S3, simplifying the multiple deformed mesh nodes based on the interpolation points of each deformed mesh node, the deformation amount of the deformed mesh node and the greedy simplification method to obtain simplified mesh nodes and corresponding displacements;

[0012] Preferably, the specific steps of obtaining the simplified grid nodes in step S3 include:

[0013] Step S31, presetting a displacement error threshold;

[0014] Step S32, let t=1, when t=1, it represents the first grid node set;

[0015] Step S33, randomly selecting 2% of the deformed mesh nodes from the multiple deformed mesh nodes as the tth mesh node set;

[0016] Perform three-dimensional spline curve interpolation on each deformed mesh node in the t-th mesh node set to obtain an interpolation point of each deformed mesh node as an interpolation point set of the t-th mesh node set;

[0017] Step S34, obtaining the deformation amount corresponding to each deformed mesh node in the t-th mesh node set; solving the displacement of each deformed mesh node based on the interpolation point set of the t-th mesh node set, the deformation amount corresponding to each deformed mesh node and the radial basis function;

[0018] Calculating the actual deformation of each deformed mesh node; obtaining the displacement error of each deformed mesh node based on the actual deformation of each deformed mesh node and the displacement of each deformed mesh node in the t-th mesh node set;

[0019] Step S35, determine whether the displacement error of each deformed grid node is less than the displacement error threshold. If so, stop the calculation and use the t-th grid node set as the simplified grid node; if not, update the interpolation point set of the t-th grid node set to obtain the interpolation point set of the t+1-th grid node set, and return to step S34.

[0020] Furthermore, the specific steps of updating the interpolation point set of the t-th grid node set in step S35 to obtain the interpolation point set of the t+1-th grid node set include:

[0021] The first 1% of the grid nodes in descending order of error size are selected from multiple grid nodes that have not been added to the t-th grid node set as interpolation points, and are added to the interpolation point set corresponding to the t-th grid node set to obtain the interpolation point set corresponding to the t+1-th grid node set.

[0022] Furthermore, the radial basis function is a Wendland C2 function

[0023] Furthermore, the expression of the radial basis function is:

[0024]

[0025] Where s(x) is the displacement of the grid node x; ω i is the weight coefficient of the i-th interpolation point, N b is the total number of interpolation points; φ(||xx i ||) is the basis function of the interpolation point set corresponding to the i-th interpolation point of the grid node, and p(x) is a polynomial related to the grid node x that can satisfy the force and torque balance, which can realize the accurate recovery of the rigid translation motion of the grid.

[0026] Step S4, obtaining coordinate points corresponding to the simplified grid nodes based on the coordinate points of each grid node in the SU2 format wing aerodynamic grid model;

[0027] Add the displacement of the simplified mesh node to the corresponding coordinate point to obtain the updated coordinate point of the simplified mesh node;

[0028] Based on the node connection information of each grid node and the distinguishing information of each grid node in step S1, the node connection information and aerodynamic calculation partitions of the simplified multiple grid nodes are obtained.

[0029] The aeroelastic dynamic grid is constructed by using the node connection information of the simplified multiple grid nodes, the aerodynamic calculation partitions and the updated coordinate points of the simplified grid nodes.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] (1) The present invention provides an aeroelastic dynamic mesh construction method for SU2 format aerodynamic meshes. In the deformation calculation process, a greedy simplification method is used to simplify the number of interpolation points required for aeroelastic dynamic mesh calculation, thereby improving the simplification efficiency and achieving efficient dynamic mesh calculation.

[0032] (2) The present invention provides an aeroelastic dynamic grid construction method for SU2 format aerodynamic grids, which can deform SU2 format aerodynamic grids of any grid unit type, such as structured grids and unstructured grids, and has good versatility;

[0033] (3) The present invention provides an aeroelastic dynamic grid construction method for SU2 format aerodynamic grids, which is applicable to any type of wing tip deformation exceeding 10% of the wing half span, and can realize dynamic grid calculation. The mesh quality after deformation is high, and no negative volume grid appears, which can meet the requirements of CFD calculation accuracy and has good robustness.

[0034] (4) The aeroelastic dynamic grid construction method for SU2 format aerodynamic grids of the present invention is helpful for application in aeroelastic calculations and realizes efficient and high-precision aeroelastic calculations. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings are only for the purpose of illustrating particular embodiments and are not to be construed as limiting the invention.

[0036] Figure 1 A flow chart of dynamic grid construction in an embodiment of the present invention;

[0037] Figure 2 is a schematic diagram of a geometrical schematic diagram of a large flexible wing in an embodiment of the present invention;

[0038] Figure 3 (a)-(b) are schematic diagrams of the airfoil structure of a large flexible wing in an embodiment of the present invention;

[0039] Figure 4 Schematic diagram of a large flexible wing aerodynamic grid in an embodiment of the present invention;

[0040] Figure 5 Schematic diagram of the deformation amount of the large flexible wing in an embodiment of the present invention;

[0041] Figure 6 Schematic diagram of the grid after deformation of the large flexible wing in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0043] A specific embodiment of the present invention, as Figure 1-6 , discloses a method for constructing aeroelastic dynamic grids for SU2 format aerodynamic grids,

[0044] In order to illustrate the effectiveness of the method proposed in the present invention, the above technical solution of the present invention is described in detail below through a specific embodiment, and the specific implementation steps are as follows:

[0045] The present invention provides an aeroelastic dynamic grid construction method for SU2 format aerodynamic grids, comprising:

[0046] Step S1, using finite element software and an aerodynamic mesh file in SU2 format to establish an aerodynamic mesh model of a wing in SU2 format;

[0047] Obtain the coordinate points of each grid node in the SU2 format wing aerodynamic grid model, the connection information between each grid node, and the distinguishing information of each grid node;

[0048] Step S2, setting working conditions, deforming the wing aerodynamic mesh model in SU2 format based on the working conditions, and obtaining a deformed aerodynamic mesh, deformed mesh nodes, and deformation amounts of the deformed mesh nodes;

[0049] Perform three-dimensional spline curve interpolation in each deformed mesh node to obtain an interpolation point of each deformed mesh node;

[0050] Step S3, simplifying the multiple deformed mesh nodes based on the interpolation points of each deformed mesh node, the deformation amount of the deformed mesh node and the greedy simplification method to obtain simplified mesh nodes and corresponding displacements;

[0051] Preferably, the specific steps of obtaining the simplified grid nodes in step S3 include:

[0052] Step S31, presetting a displacement error threshold;

[0053] Step S32, let t=1, when t=1, it represents the first grid node set;

[0054] Step S33, randomly selecting 2% of the deformed mesh nodes from the multiple deformed mesh nodes as the tth mesh node set;

[0055] Perform three-dimensional spline curve interpolation on each deformed mesh node in the t-th mesh node set to obtain an interpolation point of each deformed mesh node as an interpolation point set of the t-th mesh node set;

[0056] Step S34, obtaining the deformation amount corresponding to each deformed mesh node in the t-th mesh node set; solving the displacement of each deformed mesh node based on the interpolation point set of the t-th mesh node set, the deformation amount corresponding to each deformed mesh node and the radial basis function;

[0057] Calculating the actual deformation of each deformed mesh node; obtaining the displacement error of each deformed mesh node based on the actual deformation of each deformed mesh node and the displacement of each deformed mesh node in the t-th mesh node set;

[0058] Step S35, determine whether the displacement error of each deformed grid node is less than the displacement error threshold. If so, stop the calculation and use the t-th grid node set as the simplified grid node; if not, update the interpolation point set of the t-th grid node set to obtain the interpolation point set of the t+1-th grid node set, and return to step S34.

[0059] Furthermore, the specific steps of updating the interpolation point set of the t-th grid node set in step S35 to obtain the interpolation point set of the t+1-th grid node set include:

[0060] The first 1% of the grid nodes in descending order of error size are selected from multiple grid nodes that have not been added to the t-th grid node set as interpolation points, and are added to the interpolation point set corresponding to the t-th grid node set to obtain the interpolation point set corresponding to the t+1-th grid node set.

[0061] Furthermore, the radial basis function is a Wendland C2 function

[0062] Furthermore, the expression of the radial basis function is:

[0063]

[0064] Where s(x) is the displacement of the grid node x; ω i is the weight coefficient of the i-th interpolation point, N b is the total number of interpolation points; φ(||xx i ||) is the basis function of the interpolation point set corresponding to the i-th interpolation point of the grid node, and p(x) is a polynomial related to the grid node x that can satisfy the force and torque balance, which can realize the accurate recovery of the rigid translation motion of the grid.

[0065] Step S4, obtaining coordinate points corresponding to the simplified grid nodes based on the coordinate points of each grid node in the SU2 format wing aerodynamic grid model;

[0066] Add the displacement of the simplified mesh node to the corresponding coordinate point to obtain the updated coordinate point of the simplified mesh node;

[0067] Based on the node connection information of each grid node and the distinguishing information of each grid node in step S1, the node connection information and aerodynamic calculation partitions of the simplified multiple grid nodes are obtained.

[0068] The aeroelastic dynamic grid is constructed by using the node connection information of the simplified multiple grid nodes, the aerodynamic calculation partitions and the updated coordinate points of the simplified grid nodes.

[0069] Embodiment 1

[0070] Using large flexible wings, such as Figure 2 As shown, the wing root is fully fixed. The geometric characteristics of the example wing are as follows: the half span of the large flexible wing is 1542.1mm, the chord length of the wing root is 263.24mm, the chord length of the tip is 70.92mm, and the sweep angle is 3.4°. A supercritical airfoil is used, and the airfoil schematic diagram is shown in Figure 3 As shown;

[0071] According to an embodiment of the present invention, a method for constructing an aeroelastic dynamic grid for an SU2 format aerodynamic grid includes:

[0072] The first step is to establish a finite element model of the large flexible wing, use the finite element software pointwise to perform structured grid division on the entire flow field, establish the aerodynamic grid model of the wing in SU2 format, and set the grid partition information; the SU2 grid has a total of 2,000,000 hexahedral grids; Figure 4 ;

[0073] Step 2: After the SU2 aerodynamic mesh is divided, the deformation of each mesh node needs to be input. The structural deformation under the current working condition calculated by nastran software (such as Figure 5 ), and the deformation magnitudes of all wall nodes are obtained by interpolating three-dimensional spline curves.

[0074] This time, two calculation conditions with an angle of attack of 5° and incoming flow velocities of 30m / s and 40m / s were selected to carry out dynamic grid calculations.

[0075] Step 3: Greedy simplification method to simplify interpolation points: After inputting the deformation data of the wall nodes, the greedy simplification method is used to simplify the deformation data. The error threshold is set to 0.01mm. 2% of the nodes are selected from the wall nodes to add to the initial control point set, totaling 50 nodes. Then enter the greedy algorithm iteration loop.

[0076] After 4 cycles of the 30 m / s condition, 146 control points were selected; after 5 cycles of the 40 m / s condition, 169 control points were selected.

[0077] Step 4: Perform dynamic mesh calculation and restore connection relationship: After determining the control points, use the radial basis function method to calculate the displacement of all mesh nodes and obtain the coordinates of all mesh nodes. Then, restore the node connection and aerodynamic calculation partition of the SU2 mesh through the stored connection relationship and partition information. After testing, the deformed mesh did not produce negative volume mesh, and the mesh quality did not show a significant decrease, which met the calculation requirements of aerodynamic force in aeroelasticity. The deformed aerodynamic mesh, such as Figure 6 .

[0078] The present invention can take into account the calculation efficiency, solution accuracy and applicability of complex models in the dynamic grid calculation in aeroelastic calculation, and has important significance in the actual aircraft design application. The contents not described in detail in the present invention are well known to those skilled in the art.

[0079] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for constructing an aeroelastic dynamic grid for SU2 format aerodynamic grids, characterized in that: include: Step S1, establishing a SU2 format wing aerodynamic grid model; obtaining coordinate points of each grid node in the SU2 format wing aerodynamic grid model, connection information between each grid node, and distinguishing information of each grid node; Step S2, setting working conditions, deforming the wing aerodynamic grid model in SU2 format based on the working conditions, and obtaining a deformed aerodynamic grid, a plurality of deformed grid nodes, and a deformation amount of each deformed grid node; Performing three-dimensional spline curve interpolation in each deformed mesh node to obtain an interpolation point of each deformed mesh node; Step S3, simplifying the multiple deformed mesh nodes based on the interpolation points of each deformed mesh node, the deformation amount of the deformed mesh node and the greedy simplification method to obtain simplified mesh nodes and corresponding displacements; Step S4, obtaining coordinate points corresponding to the simplified grid nodes based on the coordinate points of each grid node in the SU2 format wing aerodynamic grid model; Add the displacement of the simplified mesh node to the corresponding coordinate point to obtain the updated coordinate point of the simplified mesh node; Based on the node connection information of each grid node and the distinguishing information of each grid node in step S1, the node connection information and aerodynamic calculation partitions of the simplified multiple grid nodes are obtained; The aeroelastic dynamic grid is constructed by using the node connection information of the simplified multiple grid nodes, the aerodynamic calculation partitions and the updated coordinate points of the simplified grid nodes.

2. The method for constructing an aeroelastic dynamic grid according to claim 1, characterized in that: The specific steps of establishing the SU2 format wing aerodynamic grid model in step S1 include: The SU2 format wing aerodynamic mesh model is established using finite element software and SU2 format aerodynamic mesh files.

3. The method for constructing an aeroelastic dynamic grid according to claim 1, characterized in that: The specific steps of obtaining the simplified grid nodes in step S3 include: Step S31, presetting a displacement error threshold; Step S32, let t=1, when t=1, it represents the first grid node set; Step S33, randomly selecting 2% of the deformed mesh nodes from the multiple deformed mesh nodes as the tth mesh node set; Perform three-dimensional spline curve interpolation on each deformed mesh node in the t-th mesh node set to obtain an interpolation point of each deformed mesh node as an interpolation point set of the t-th mesh node set; Step S34, obtaining the deformation amount corresponding to each deformed mesh node in the t-th mesh node set; solving the displacement of each deformed mesh node based on the interpolation point set of the t-th mesh node set, the deformation amount corresponding to each deformed mesh node and the radial basis function; Calculating the actual deformation of each deformed mesh node; obtaining the displacement error of each deformed mesh node based on the actual deformation of each deformed mesh node and the displacement of each deformed mesh node in the t-th mesh node set; Step S35, determine whether the displacement error of each deformed grid node is less than the displacement error threshold. If so, stop the calculation and use the t-th grid node set as the simplified grid node; if not, update the interpolation point set of the t-th grid node set to obtain the interpolation point set of the t+1-th grid node set, and return to step S34.

4. The method for constructing an aeroelastic dynamic grid according to claim 3, characterized in that: The specific steps of updating the interpolation point set of the t-th grid node set to obtain the interpolation point set of the t+1-th grid node set in step S35 include: The first 1% of the grid nodes in descending order of error size are selected from multiple grid nodes that have not been added to the t-th grid node set as interpolation points, and are added to the interpolation point set corresponding to the t-th grid node set to obtain the interpolation point set corresponding to the t+1-th grid node set.

5. The method for constructing an aeroelastic dynamic grid according to claim 3, characterized in that: The radial basis function is the Wendland C2 function.

6. The method for constructing an aeroelastic dynamic grid according to claim 3, characterized in that: The expression of the radial basis function is: Where s(x) is the displacement of the grid node x; ω i is the weight coefficient of the i-th interpolation point, N b is the total number of interpolation points; φ(||xx i ||) is the basis function of the interpolation point set corresponding to the i-th interpolation point of the grid node, and p(x) is the polynomial related to the grid node x that can satisfy the force and moment balance.

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