Unified blade grid generation method and device

Abstract

The invention provides a unified blade grid generation method and device, and the method comprises the steps: adaptively generating unified grid division control parameters through wing configuration, chord length distribution, sweepback downward inversion and torsion distribution layout parameter information, and generating a blade grid based on the grid division control parameters. By means of the blade grid generation method and device, the blade grid with good consistency can be generated, the use steps of an existing grid generation program are simplified, and the practical engineering application range of the blade grid generation program is widened.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of helicopter rotor aerodynamic analysis, and particularly relates to a unified blade grid generation method and device. BACKGROUND

[0002] Mesh division has a crucial influence on the CFD calculation evaluation results, and a large number of CFD calculation evaluations of aerodynamic calibration models at home and abroad need to first conduct mesh independence research to eliminate the influence of mesh division on the calculation results as much as possible. For a rotor, due to the strong unsteady characteristics of the flow and the existence of aerodynamic interference between the blades, the blade mesh division has a more important influence on the capture of flow details and the evaluation results of blade performance, and the calculation cost brought by blindly increasing the grid amount is often unacceptable in engineering practice. Therefore, in order to reflect the performance difference between different shape schemes as much as possible in engineering design and reduce the influence of mesh on the calculation results, it is necessary to ensure that the blade meshes used by different shape schemes have good consistency in division, which is specifically reflected in the grid amount, grid point arrangement, first layer grid height, near-wall growth rate, grid shape boundary size and the like.

[0003] The existing mesh generation means adopts the idea of first generating a two-dimensional airfoil grid and then generating a three-dimensional blade grid, and there are many control parameters in the mesh generation process, and the control parameters cannot be adaptively adjusted with the change of the layout shape, so that the method has certain limitations when applied to the fine design of the blade layout. SUMMARY

[0004] In order to solve the problem that there are many control parameters in the mesh generation process in the prior art, and the control parameters cannot be adaptively adjusted with the change of the layout shape, and the method has certain limitations when applied to the fine design of the blade layout, the application provides a unified blade grid generation method and device. The application proposes an automatic parameterized mesh generation method based on the existing blade grid generation program, and writes a corresponding program based on the method. The method adaptively generates unified mesh division control parameters by directly inputting airfoil configuration, chord length distribution, sweep down, twist distribution and other layout parameter information, generates blade meshes with good consistency, simplifies the use steps of the existing mesh generation program, and expands the engineering practical application range of the program. The technical scheme is as follows: In a first aspect, a unified blade grid generation method is provided. The method adaptively generates unified mesh division control parameters through airfoil configuration, chord length distribution, sweep down, twist distribution and other layout parameter information, and generates blade meshes based on the mesh division control parameters.

[0005] Optionally, the method specifically includes: Step 1, write the number of blade sections, airfoil configuration, chord length distribution, forward and backward sweep / up and down reverse distance, twist distribution parameters into the grid generation control file as the blade profile input; Step 2, determine the profile airfoil grid generation parameters; and write the profile airfoil grid generation parameters into the airfoil two-dimensional grid generation control file to generate the two-dimensional airfoil grid of each airfoil profile, and sort the generated two-dimensional airfoil grid file according to the airfoil station arrangement order; Step 3, convert the chord length in step 1 to the chord length under the preset radius and write it into the file, convert the forward and backward sweep / up and down reverse distance in step 1 to the forward and backward sweep / up and down reverse distance under the preset radius and write it into the file; process the spanwise station points of the blade surface grid points and write them into the file, so that all grid points are distributed on the blade surface in the spanwise station; Step 4, based on the number of airfoil surface grid points n_foil, the number of trailing edge slot grid points n_wake, and the number of normal surface grid points n_normal, calculate the number of two-dimensional airfoil grid I direction grid points IMAX, J direction grid points JMAX, airfoil surface I direction starting point sequence number ISTA, airfoil surface I direction terminal point sequence number IEND, and generate a control file in combination with the spanwise station data; Step 5, based on all the files of steps 1 to 4, generate a three-dimensional calculation grid file.

[0006] Optionally, the airfoil grid generation parameters include two-dimensional grid far field size, number of airfoil surface grid points n_foil, number of trailing edge slot grid points n_wake, and number of normal surface grid points n_normal, first layer of wall normal grid height near the airfoil leading edge, airfoil trailing edge point surface grid chord length, first layer of wall normal grid height near the airfoil trailing edge, and trailing edge point slot grid length.

[0007] Optionally, in step 2, the two-dimensional grid far field size is 1.5 times the local chord length by default, the average chord length of the blade in each airfoil section is calculated, when the average chord length of the airfoil is greater than 0.1R, the two-dimensional grid far field size of the airfoil is selected as 1.5 times the average chord length, and when the spanwise station of the airfoil is less than 0.4R, the two-dimensional grid far field size is determined according to the following formula: .

[0008] Optionally, in step 3, the formula used for processing the spanwise station points of the blade surface grid points is: , All grid spanwise station points are traversed, and when the spanwise distribution control point satisfies the following relationship: , otherwise , The relationship is: .

[0009] Optionally, in step 4, .

[0010] In a second aspect, a unified blade grid generation device is provided, comprising: A first generation module is configured to generate unified grid division control parameters by using wing profile configuration, chord length distribution, sweep down, twist distribution layout parameter information, and adaptively generating the unified grid division control parameters; A second generation module is configured to generate a blade grid based on the grid division control parameters.

[0011] The first generation module is specifically configured to: Write the number of blade pieces, wing profile configuration, chord length distribution, forward and backward sweep distance, and twist distribution parameters into a grid generation control file as a blade profile input, and scale the chord length and forward and backward sweep distance according to a preset radius; Determine the profile wing grid generation parameters, write the profile wing grid generation parameters into a two-dimensional wing grid generation control file, generate a two-dimensional wing grid for each wing profile, and sort the generated two-dimensional wing grid files according to the wing station arrangement order; Convert the chord length into a chord length under a preset radius and write it into a file, convert the forward and backward sweep distance into a forward and backward sweep distance under a preset radius and write it into a file, process the spanwise station points of the blade surface grid points and write them into a file, and make all the spanwise station points distributed on the blade surface; Based on the number of wing profile surface grid points n_foil, the number of grid points at the trailing edge gap n_wake, and the number of normal surface grid points n_normal, calculate the number of two-dimensional wing grid I direction grid points IMAX, the number of J direction grid points JMAX, the starting point sequence number ISTA of the wing profile surface in the I direction, and the ending point sequence number IEND of the wing profile surface in the I direction, and generate a control file in combination with the spanwise station data; The second generation module is specifically configured to generate a three-dimensional calculation grid file based on all the above files.

[0012] The present application has at least the following advantages: The present application can generate a blade grid with good consistency more conveniently and quickly. The method can be applied to the calculation grid division of blades of helicopters, propellers, fans, etc., and has universality. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The present application is a method flowchart; Figure 2 The present application is a blade profile parameter input schematic diagram; Figure 3Schematic diagram for generating control files for airfoil 2D mesh; Figure 4 A diagram illustrating the naming of an airfoil 2D mesh file.

[0014] Figure 5 A schematic diagram showing the comparison before and after the surface grid point spanwise replacement; Figure 6 Schematic diagram for generating control files for 3D propeller blade mesh; Figure 7 This is a schematic diagram of the airfoil configuration; Figure 8 This is a schematic diagram of the chord length distribution; Figure 9 This is a schematic diagram of the forward and backward sweep distribution; Figure 10 This is a schematic diagram of the torsional distribution; Figure 11 This is a schematic diagram of a three-dimensional blade mesh. Figure 12 This is a schematic diagram of a two-dimensional airfoil cross-sectional mesh. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0017] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited from each other.

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] This invention proposes an automatic parametric mesh generation method. This method adaptively generates unified mesh generation control parameters by directly inputting layout parameters such as airfoil configuration, chord length distribution, sweep-down anhedral, and torsional distribution, resulting in a blade mesh with good consistency. The specific process of this invention is as follows: Figure 1 As shown.

[0020] The specific implementation steps are as follows: 1. Input parameters such as the number of blades, airfoil configuration, chord length distribution, forward / backward sweep / vertical diagonal distance, and torsional distribution into the mesh generation control file as input for the blade shape. See [link to relevant documentation]. Figure 2 .

[0021] 2. Determine the airfoil mesh generation parameters for each profile: The default far-field boundary size of the 2D airfoil mesh is 1.5 times the local chord length. Simultaneously, the average chord length of the blades within each airfoil segment is calculated. When the average chord length of the airfoil segment is greater than 0.1R, the far-field size of the 2D mesh for that airfoil is set to 1.5 times the average chord length. Otherwise, when the spanwise position of the airfoil is less than 0.4R, the far-field size of the 2D mesh is determined according to the following formula:

[0022] Set the number of mesh points on the airfoil surface (n_foil), the number of mesh points at the trailing edge slit (n_wake), and the number of mesh points in the normal direction of the airfoil surface (n_normal) according to user needs. For example, based on existing usage experience, it is recommended to set the above three parameters to 160, 32, and 49 respectively.

[0023] The height of the first-layer mesh in the normal direction near the leading edge of the airfoil is adaptively determined according to the following formula:

[0024] The chord length of the object-plane mesh at the trailing edge point of the airfoil is adaptively determined according to the following formula:

[0025] The height of the first-layer mesh in the normal direction near the trailing edge of the airfoil is adaptively determined according to the following formula:

[0026] The mesh length at the trailing edge notch of the airfoil is adaptively determined according to the following formula:

[0027] In the above formulas, c is the local chord length of the blade at the airfoil profile position read in step 1.

[0028] 3. Write the information from step 2 above into the following file: Figure 3The control file for generating the 2D mesh of the airfoil shown is used to generate the 2D airfoil mesh for each airfoil profile. The generated 2D airfoil mesh file is then named airfoil_n.dat according to the airfoil station placement order, where n is the airfoil profile number, as shown in the following format. Figure 4 As shown.

[0029] 4. Process the string length read in step 1 using the following formula and write it to the file CHORD.DAT:

[0030] The forward / backward sweep / upward / downward anti-sweep distances read in step 1 are processed according to the following formula and then written to the file TIP.DAT:

[0031] Where c, Xo, and Yo are the chord length and forward / backward sweep / upward / downward anti-reverse distance read in step 1, respectively, and Chord, X_tip, and Y_tip are the chord length and forward / backward sweep / upward / downward anti-reverse distance after scaling the blade to the preset radius, respectively.

[0032] Write the torsion distribution read in step 1 directly into the file TWIST.DAT.

[0033] The spanwise distribution of the blade surface grid points is as shown in Table 1 by default, with a total of 93 stations.

[0034] Table 1 Default spanwise distribution of grid points on the blade surface

[0035] However, it should be noted that the blade has a certain root shear. In order to ensure that all grid points are distributed on the blade surface, the points in Table 1 are processed using the following formula.

[0036]

[0037] To ensure the accuracy of the blade surface mesh shape and to guarantee that the arrangement of the airfoil's two-dimensional mesh reflects the actual airfoil design location during subsequent three-dimensional mesh generation, points near the airfoil design location are replaced using the following method: Traverse all grid spanwise control points, and when the spanwise distribution control points satisfy the following relationship...

[0038] make

[0039] otherwise , Where span(i) represents the spanwise station location, i is the station number, and r_foil is the airfoil design station location.

[0040] Specifically, such as Figure 5 As shown, the top image shows the original spanwise station position, and the bottom image shows the station position after replacement according to the actual airfoil. Afterwards, the spanwise distribution points of the replaced blade surface mesh are written to the file SPAN.DAT.

[0041] 5. Fill in the 3D mesh generation control file INPUT.DAT. The number of airfoil control profiles NAIR is the number of airfoil profiles read in step 1, NSEC is NAIR-1, NAFN0 and NAFAN1 are the number of folded mesh points on the blade root and blade tip surfaces, which are fixed at 10. The number of mesh points IMAX in the I direction, the number of mesh points JMAX in the J direction, the starting point number ITA of the airfoil surface in the I direction, and the ending point number IEND of the airfoil surface in the I direction obtained in step 3 are determined by the following formulas. The peeling control parameters of the blade 3D mesh in the I and J directions can be set by the user according to their actual needs, with a default value of 0. The blade mesh radius is set to 10 by default.

[0042]

[0043] The spanwise station data in the file SPAN.DAT generated in step 4 is traversed. When the following relationship is satisfied, the spanwise station number corresponding to the i-th airfoil two-dimensional grid is determined to be j.

[0044]

[0045] Fill in the 2D airfoil mesh spanwise arrangement control parameters KSTA, KEND, AIRFOIL1, and AIRFOIL2 in sequence according to the above correspondence. The completed 3D mesh generation control file INPUT.DAT is as follows: Figure 6 As shown. Running the 3D blade mesh generation program will generate a computational mesh file with good consistency.

[0046] The following example, using a tilting propeller blade, illustrates the application effect of this invention. The airfoil configuration is as follows: Figure 7 As shown, the chord length distribution is as follows Figure 8 As shown, the front-to-back sweep / up-down reverse distribution is as follows: Figure 9 As shown, Figure 10 The blades are twisted. Figure 11 and Figure 12 These are the 3D and 2D airfoil profile meshes for the blade, respectively. It can be seen that the meshes generated by this method are automatically refined near the blade surface, at the leading and trailing edges of the blade surface, and at the blade root and tip. Simultaneously, the outer boundary size of the 3D mesh at the blade root is reduced to prevent mesh overlap at the blade root of adjacent blades during full-model calculations.

[0047] The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Furthermore, any parts of the present invention not described in detail are conventional techniques.

Claims

1. A unified method for generating blade meshes, characterized in that, By using airfoil configuration, chord length distribution, sweep-down, and torsional distribution layout parameters, unified mesh generation control parameters are adaptively generated, and blade mesh is generated based on these mesh generation control parameters.

2. The method according to claim 1, characterized in that, The method specifically includes: Step 1: Write the blade number, airfoil configuration, chord length distribution, forward and backward sweep / vertical reverse distance, and torsional distribution parameters into the mesh generation control file as the blade shape input; Step 2: Determine the airfoil mesh generation parameters for each section; and write the airfoil mesh generation parameters for each section into the airfoil 2D mesh generation control file to generate the 2D airfoil mesh for each airfoil section. Sort the generated 2D airfoil mesh files according to the airfoil station layout order. Step 3: Convert the chord length in Step 1 to the chord length under the preset radius and write it to the file; convert the forward and backward sweep / upward and downward anti-sweep distance in Step 1 to the forward and backward sweep / upward and downward anti-sweep distance under the preset radius and write it to the file; process the spanwise station points of the blade surface grid and write them to the file so that all grid point spanwise station points are distributed on the blade surface. Step 4: Based on the number of mesh points n_foil on the airfoil surface, the number of mesh points n_wake at the trailing edge slit, and the number of mesh points n_normal in the surface normal, calculate the number of mesh points IMAX in the I direction, the number of mesh points JMAX in the J direction, the starting point number ITA of the airfoil surface in the I direction, and the ending point number IEND of the airfoil surface in the I direction. Combine this with the spanwise station data to generate a control file. Step 5: Generate a 3D computational mesh file based on all the files from Steps 1 to 4.

3. The method according to claim 2, characterized in that, The airfoil mesh generation parameters include the far-field size of the two-dimensional mesh, the number of mesh points on the airfoil surface n_foil, the number of mesh points at the trailing edge slit n_wake, the number of mesh points in the normal direction of the airfoil surface n_normal, the height of the first layer of mesh in the normal direction of the wall near the leading edge of the airfoil, the chord length of the mesh on the airfoil surface at the trailing edge point, the height of the first layer of mesh in the normal direction of the wall near the trailing edge of the airfoil, and the mesh length at the slit point of the airfoil trailing edge point.

4. The method according to claim 2, characterized in that, In step 2, when determining the far-field dimensions of the two-dimensional mesh, the default far-field boundary dimension of the two-dimensional airfoil mesh is 1.5 times the local chord length. The average chord length of the blades within each airfoil segment is calculated. When the average chord length of the airfoil segment is greater than 0.1R, the far-field dimensions of the two-dimensional mesh for that airfoil are determined by 1.5 times the average chord length. Otherwise, when the spanwise position of the airfoil is less than 0.4R, the far-field dimensions of the two-dimensional mesh are determined according to the following formula: 。 5. The method according to claim 2, characterized in that, In step 3, the formula used to process the spanwise station points of the blade surface grid is: , Traverse all grid spanwise control points, and when the spanwise distribution control points satisfy the following relationship, let... ,otherwise , The relation is: .

6. The method according to claim 2, characterized in that, In step 4, 。 7. An apparatus for performing the unified blade mesh generation method according to any one of claims 1 to 6, characterized in that, include: The first generation module is used to adaptively generate unified mesh generation control parameters based on airfoil configuration, chord length distribution, sweep-down and torsional distribution layout parameter information. The second generation module is used to generate blade meshes based on mesh generation control parameters.

8. The apparatus according to claim 7, characterized in that, The first generation module is specifically used for: The number of blades, airfoil configuration, chord length distribution, forward and backward sweep / vertical reverse distance, and torsional distribution parameters are written into the mesh generation control file as the blade shape input. The chord length and forward and backward sweep / vertical reverse distance are obtained by scaling according to the preset radius. Determine the airfoil mesh generation parameters for each profile; write the airfoil mesh generation parameters for each profile into the airfoil 2D mesh generation control file, generate the 2D airfoil mesh for each airfoil profile, and sort the generated 2D airfoil mesh files according to the airfoil station layout order; Convert the chord length to the chord length under the preset radius and write it to the file; convert the forward / backward sweep / up / downward reverse distance to the forward / backward sweep / up / downward reverse distance under the preset radius and write it to the file. Process the spanwise station points of the blade surface grid and write them into a file so that all spanwise station points of the grid are distributed on the blade surface; Based on the number of mesh points n_foil on the airfoil surface, the number of mesh points n_wake at the trailing edge slit, and the number of mesh points n_normal in the surface normal, the number of mesh points IMAX in the I direction, the number of mesh points JMAX in the J direction, the starting point number ITA of the airfoil surface in the I direction, and the ending point number IEND of the airfoil surface in the I direction are calculated. Combined with spanwise station data, a control file is generated. The second generation module is specifically used to generate a 3D computational mesh file based on all the above files.

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