Rotor aerodynamic force and flow field analogue simulation method

Abstract

The invention discloses a rotor aerodynamic force and flow field simulation method, and relates to the field of aerospace, and the method comprises the steps: generating a blade skin grid according to rotor configuration parameters, and constructing a Cartesian background grid; constructing a calculation model of variable-diameter rotor flow field simulation based on the blade skin grid and the Cartesian background grid; and in the constructed calculation model for variable-diameter rotor flow field simulation, a high-precision CFD method suitable for variable-diameter rotor flow field solving is established, rotor aerodynamic force and a flow field in the dynamic diameter changing process are simulated, and a CFD calculation result is output. The aerodynamic performance of the rotor wing can be improved by simulating the variable-diameter rotor wing flow field.

Description

Technical Field

[0001] The present application relates to the field of aerospace, and in particular to a method for simulating rotor aerodynamics and flow fields. Background Art

[0002] The aerodynamic performance of the rotor greatly affects the flight performance of the rotorcraft. Therefore, adaptively changing the aerodynamic shape or motion parameters of the rotor according to the airflow environment and working state of the rotor can directly change the aerodynamic characteristics of the rotor. As the main lift component of the helicopter, the aerodynamic performance of the rotor largely determines the flight performance of the aircraft. Therefore, improving the performance of the rotor has always been the research focus of rotorcraft technology. Traditional rotor passive design has achieved remarkable results in improving rotor performance, and can obtain better flight performance in a certain or local flight state. However, as the flight environment or flight state changes, the flight performance of the rotor will decrease after it deviates from the better working state. The existing method of simulating the rotor flow field cannot improve the aerodynamic performance of the rotor. The rotor variable diameter technology belongs to a kind of intelligent rotor. The blade variable diameter technology has a significant effect on improving the aerodynamic performance of the aircraft, so a method is needed to improve the aerodynamic performance of the rotor by simulating the variable diameter rotor flow field. Summary of the invention

[0003] The purpose of this application is to provide a rotor aerodynamic and flow field simulation method, which can improve the rotor aerodynamic performance by simulating the variable diameter rotor flow field.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In a first aspect, the present application provides a rotor aerodynamic and flow field simulation method, comprising:

[0006] Generate blade body-fitting grid and construct Cartesian background grid according to rotor configuration parameters;

[0007] A computational model for simulating the flow field of a variable diameter rotor is constructed based on the blade body-fitting grid and the Cartesian background grid;

[0008] In the constructed calculation model for variable diameter rotor flow field simulation, a high-precision CFD method suitable for solving the variable diameter rotor flow field is established, and the rotor aerodynamic force and flow field in the dynamic variable diameter process are simulated, and the CFD calculation results are output.

[0009] Optionally, generating a blade body-fitted mesh according to the rotor configuration parameters specifically includes:

[0010] Generate a two-dimensional airfoil mesh according to rotor configuration parameters;

[0011] A three-dimensional blade mesh is constructed based on the two-dimensional airfoil mesh as the blade body-fitted mesh.

[0012] Optionally, a computational model for simulating the variable diameter rotor flow field is constructed based on the blade body-fitting grid and the Cartesian background grid, specifically comprising:

[0013] A computational model for variable diameter rotor flow field simulation is constructed by using a moving nested grid method and an applied displacement function method; the moving nested grid method includes digging holes, contributing unit search and interpolation; the applied displacement function method is to apply a variable diameter displacement function to the blade body-fitting grid.

[0014] Optionally, in the constructed computational model for variable diameter rotor flow field simulation, a high-precision CFD method suitable for solving the variable diameter rotor flow field is established, specifically including:

[0015] The unsteady Reynolds-averaged NS equations are used as the control equations to numerically simulate the unsteady flow field of the rotor with dynamically variable diameter.

[0016] After the numerical simulation is completed, the grid-centered finite volume method is used to numerically discretize the spatial grid information in the simulation results to obtain the final calculation model; during the numerical discretization process, the convective flux at the interface of the grid unit is calculated using the Roe format, and the flow state quantities on both sides of the grid surface are obtained by interpolation using the MUSCL / CD scheme.

[0017] Optionally, the rotor aerodynamic force and flow field during the dynamic diameter change process are simulated, and the CFD calculation results are output, including:

[0018] Perform nesting initialization, dig holes and search for contributing units in the blade body-fitting grid in the background grid, and store the nesting relationship between the two; when the blade moves with time or azimuth, update and store the nesting relationship between the rotor blade body-fitting grid and the background grid at each station;

[0019] Applying a variable diameter displacement function to the blade body-fitting grid in the computational model for variable diameter rotor flow field simulation;

[0020] The overlapping grids in the computational model of the variable diameter rotor flow field simulation after applying the variable diameter displacement function are set to dynamic overlapping behavior, and then the grid units are corrected to obtain the corrected computational model;

[0021] The final calculation model is used to calculate the rotor flow field of the modified calculation model, the flow field is initialized and the nested relationship is repeatedly updated, and the flow field information at each station is updated and recorded until the calculation is completed, and the CFD calculation results are output.

[0022] Optionally, the CFD calculation results include: an unsteady tensile load diagram, a cross-sectional vorticity diagram, and a flow field isosurface vorticity diagram.

[0023] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0024] The present application provides a method for simulating rotor aerodynamics and flow fields. The rotor will cause performance degradation in certain specific flight states or aerodynamic environments. In essence, the compromise of parameter design makes it difficult to achieve the best performance of the aircraft. At present, the adaptive active variant technology is developing rapidly. The design of intelligent rotors (rotor variable diameter technology or blade variable diameter technology) is expected to improve the flight performance of the rotor in such a state. For example, the stall of the rotor backward blades and the shock wave of the forward blades are the main factors limiting the flight speed. When the rotor blades pass the forward side, a shock wave effect will be generated, which has a great inhibitory effect on the flight performance of the aircraft. Research on the flow mechanism of blade variable diameter shows that the blade variable diameter technology can adaptively adjust the length according to the flight state, adaptively change the variant in different flight environments, thereby changing the rotor aerodynamic layout to significantly improve the hovering efficiency and cruising efficiency of helicopters and tilt-rotor aircraft. The use of a variable diameter rotor structure can obtain the advantages of low rotor disc load and high cruising speed in hovering. In addition, blade variable diameter technology also has broad application prospects in the fields of fixed-wing, missile wing and cross-medium aircraft technology. However, there is still a lack of systematic research on rotor variable diameter technology at home and abroad. In the computational model of variable diameter rotor flow field simulation, the present application establishes a high-precision CFD method suitable for solving variable diameter rotor flow field and simulates the rotor aerodynamic force and flow field during the dynamic variable diameter process, and outputs the CFD calculation results. An increase in rotor diameter will improve hovering performance, while a decrease in rotor diameter will improve cruise performance. Therefore, the present application can achieve the purpose of improving the aerodynamic performance of the rotor by simulating the variable diameter rotor flow field. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic diagram of a nested grid system and hole digging and contribution unit search for NACA rotor motion in an embodiment of the present application;

[0027] Figure 2 A schematic diagram of a NACA rotor variable diameter motion grid boundary and information transmission in an embodiment of the present application;

[0028] Figure 3 A comparison diagram of the unsteady pull load of the rotor in transient aerodynamic behavior in an embodiment of the present application;

[0029] Figure 4This is a comparison diagram of the unsteady tensile load during the variable diameter rotor in the hovering state in the embodiment of the present application;

[0030] Figure 5 This is a cross-sectional vorticity diagram of a variable diameter rotor in a hovering state in an embodiment of the present application;

[0031] Figure 6 This is a comparison diagram of unsteady tensile loads during the variable diameter rotor process in the forward flight state in the embodiment of the present application;

[0032] Figure 7 This is a flow field isosurface vorticity diagram of the variable diameter rotor in the forward flight state in the embodiment of the present application;

[0033] Figure 8 This is a flow chart of a method for simulating rotor aerodynamics and flow field in one embodiment of the present application. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0035] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0036] In an exemplary embodiment, Figure 8 As shown, a rotor aerodynamic and flow field simulation method is provided, comprising the following steps:

[0037] Step 201: Generate a blade body-fitting grid and construct a Cartesian background grid according to the rotor configuration parameters. The Cartesian background grid is constructed to support accurate flow field analysis and reduce computing resource consumption.

[0038] Step 202: construct a computational model for variable diameter rotor flow field simulation based on the blade body-fitting grid and the Cartesian background grid.

[0039] Step 203, in the constructed calculation model for variable diameter rotor flow field simulation, a high-precision CFD method suitable for solving the variable diameter rotor flow field is established and the rotor aerodynamic force and flow field in the dynamic variable diameter process are simulated, and the CFD calculation results are output. The CFD calculation results are used to analyze the rotor vortex field to obtain analysis results, and the analysis results can be used to change the rotor variable diameter motion law.

[0040] By implementing the above steps 201 to 203, the purpose of improving the aerodynamic performance of the rotor can be achieved.

[0041] In another exemplary embodiment of the present application, generating a blade body-fitting grid according to the rotor configuration parameters specifically includes:

[0042] A two-dimensional airfoil mesh is generated according to the rotor configuration parameters; the rotor configuration parameters are the rotor shape parameters required for the flow field simulation process.

[0043] A three-dimensional blade mesh is constructed based on the two-dimensional airfoil mesh as a blade body-fitting mesh. Specifically, the two-dimensional airfoil mesh is used to establish the mesh distribution number along the blade span direction, and the blade body-fitting mesh is generated by interpolation method. Based on the established blade body-fitting mesh, iterative correction and adjustment are performed according to the chord length distribution and chord line position, and then a three-dimensional blade mesh is constructed through operations such as folding and tiling.

[0044] In another exemplary embodiment of the present application, a computational model for simulating the flow field of a variable diameter rotor is constructed based on the blade body-fitting grid and the Cartesian background grid, specifically including:

[0045] The computational model for variable diameter rotor flow field simulation is constructed by using the moving nested grid method and the method of applying displacement function; the moving nested grid method includes digging holes, contributing unit search and interpolation; the method of applying displacement function is to apply a variable diameter displacement function to the blade body-fitting grid. The digging holes and the contributing unit search can establish the connection between each block of grids, which is used to transmit the information of the interface boundary required for the flow field calculation in each area. The interpolation is used to process the blade body-fitting grid, and complete the process of obtaining the grid boundary unit information from the contributing unit information in order to formulate the information transmission strategy. The specific application of the variable diameter displacement function to the blade body-fitting grid is to apply the required diameter spanwise displacement to the mobile grid nodes in the blade body-fitting grid, collect the set control points and their known displacement vectors in the area, and generate an interpolation field to obtain the diameter spanwise displacement of other grid nodes in the area.

[0046] In another exemplary embodiment of the present application, in the constructed computational model for variable diameter rotor flow field simulation, a high-precision CFD method suitable for solving the variable diameter rotor flow field is established, specifically including:

[0047] The unsteady Reynolds Averaged Navier-Stockes (URANS) equations are used as the control equations to numerically simulate the unsteady flow field of the rotor with dynamically variable diameter.

[0048] After the numerical simulation is completed, the grid-center finite volume method is used to numerically discretize the spatial grid information in the simulation results to obtain the final calculation model; during the numerical discretization process, the convective flux at the interface of the grid unit is calculated using the Roe format to improve the accuracy and robustness of the rotor flow field, and the flow state quantities on both sides of the grid surface are obtained by interpolation using the MUSCL / CD scheme.

[0049] In another exemplary embodiment of the present application, the rotor aerodynamic force and flow field during the dynamic diameter change process are simulated, and the CFD calculation results are output, specifically including:

[0050] Perform nesting initialization, dig holes and search for contributing units in the blade body-fitting grid in the background grid, and store the nesting relationship between the two; when the blade moves with time or azimuth, update and store the nesting relationship between the rotor blade body-fitting grid and the background grid at each station.

[0051] A variable diameter displacement function is applied to the blade body-fitting grid in the computational model of variable diameter rotor flow field simulation.

[0052] The overlapping grids in the computational model of the variable diameter rotor flow field simulation after applying the variable diameter displacement function are set to dynamic overlapping behavior, and then the grid units are corrected to obtain the corrected computational model. Since the blade spatial position is different at each time step during the variable diameter process, the overlapping grids are set to dynamic overlapping behavior, that is, when the blade intersects with another overlapping area, the previous wall boundary will be converted to an overlapping boundary (or the overlapping boundary will be converted to a wall boundary) according to the specific position. Affected by the interpolation at the interface of the overlapping grid, the mass correction of the grid unit is required to prevent mass imbalance through flux correction.

[0053] The final calculation model is used to calculate the rotor flow field of the modified calculation model, the flow field is initialized and the nested relationship is repeatedly updated, and the flow field information at each station is updated and recorded until the calculation is completed, and the CFD calculation results are output.

[0054] In another exemplary embodiment of the present application, the CFD calculation results include: an unsteady tensile load diagram, a cross-sectional vorticity diagram, and a flow field isosurface vorticity diagram.

[0055] This application also provides an embodiment to introduce the above method in detail:

[0056] This embodiment mainly includes:

[0057] Step 1: Generate grid and construct calculation model according to rotor configuration parameters.

[0058] Step 1.1: Mesh generation:

[0059] This application uses the motion nested grid method to simulate the motion of the rotor blades to generate a grid system. The grid system includes the rotor blade body grid and the background grid, and the generated grid system is processed as follows: the background grid is encrypted near the rotor blades, and the overall calculation domain size is: (10×10×12)L, where L is the blade length. At the same time, in order to capture the rotor dynamic wake vortex and blade-vortex interference and other phenomena, the background grid area where the blade is located is encrypted, and the total number of grids is about 10 million. Figure 1 shown.

[0060] Step 1.2: Computational model construction:

[0061] The motion nested grid method and the displacement function method are used to construct a computational model for the simulation of the variable diameter rotor flow field. The movement of the rotor includes not only rotation, but also flapping, oscillation, pitch change and other movements. In order to realize complex rotation, flapping and pitch change movements, the motion nested grid method is required. At the same time, the displacement function is set in the body-fitting grid area of ​​the blade. Taking the 0° azimuth position of the propeller disc plane as the reference, the blade starts to move in the radial direction with variable diameter synchronously. The motion trajectory of the variable diameter blade is parameterized and modeled, which can be expressed as:

[0062]

[0063] Where, θ=ωt represents the blade azimuth, ω is the rotor rotation angular velocity, and t is the time; (x n ,y n ) represents the position coordinate of the blade tip after n time steps at time t; R0 represents the initial radius of the blade; V0 represents the speed of the blade changing diameter. The blade rotation direction is specified as right-hand direction (in accordance with the right-hand rule).

[0064] On the basis of nested grids, the variable diameter motion of the blade is realized by applying displacement function. The variable diameter displacement function expression is:

[0065]

[0066] Where V represents the radial velocity of the blade; A and C are correlation coefficients. A m , B m 、a n and b n is the correlation coefficient of the motion shape function, t n is the time under n time steps. The multi-dimensional motion of the blade is realized by associating the nested grid nodes with the known displacement vector. The information is transferred between the nested grids using the trilinear interpolation method.

[0067] Step 2: Establish a high-precision CFD method suitable for solving the flow field of variable diameter rotors, which is used to simulate the rotor aerodynamic force and flow field during the dynamic diameter change process. The dynamic diameter change process of the variable diameter blade body-fitting grid is as follows: the blade body-fitting grid rotates around the center of the hub, and radial displacement is applied to the grid node. The set control points and their known displacement vectors are collected in the area, and the interpolation field is generated to obtain the radial displacement of other grid nodes in the area. Update the node position of the current time step, optimize the grid of the body-fitting grid or the nodes near the boundary, and ensure flux conservation by correcting the displacement grid unit during the blade variable diameter movement process (dynamic diameter change process). The blade body-fitting grid transmits information with the background grid at each unit time step.

[0068] Step 2.1: Establish a high-precision CFD method suitable for solving the variable diameter rotor flow field:

[0069] In the CFD method, URANS is used as the control equation to numerically simulate the unsteady flow field of the rotor with dynamically variable diameter. URANS is:

[0070]

[0071] In the formula, vectors U and F v are the conserved variables and viscous flux respectively; q=[u,v,w] T is the absolute velocity of the rotor grid unit, u, v, w represent the three components of the grid unit velocity in the absolute coordinate system, and V represents the volume of the control volume. Based on the motion of the blade body-fitting grid, the corrected convective flux is: where q b =ω×r+v MRF =[u b ,v b ,w b ] T is the velocity involved in the blade body-fitting mesh motion, including blade rotation, pitch change, flapping motion and diameter change motion, u b , v b , w b It is the three components of the velocity along the coordinate axis, ω represents the angular velocity, r represents the vector from the grid unit to the coordinate origin, v MRF is the additional variable diameter velocity, S represents the infinitesimal area, and n represents the out-of-plane normal vector of the infinitesimal element.

[0072] After the numerical simulation is completed, the grid-centered finite volume method is used to numerically discretize the spatial grid information in the simulation results to obtain the final calculation model; during the numerical discretization process, the convective flux at the interface of the grid unit is calculated using the Roe format, and the flow state quantities on both sides of the grid surface are obtained by interpolation using the MUSCL / CD scheme. In order to avoid the non-physical solution that may appear in the Roe format approximate Riemann solution, the entropy proposed by Harten and Hyman is used for correction. The implicit LU-SGS method based on the dual time advancement method is used for time advancement. The turbulence model adopts the Spalart-Allmaras equation model.

[0073] Since the blade body-fitting grid is attached with variable diameter motion, it is necessary to introduce additional flux in the convection term to modify the conservation equation. When the grid moves, the following formula is used to correct the mass of the grid unit to achieve spatial conservation. The formula is as follows:

[0074]

[0075] Where V g is the grid velocity in the base reference frame.

[0076] Step 2.2: Simulate the rotor aerodynamic force and flow field during the dynamic diameter change process:

[0077] Step 2.2.1. Perform nesting initialization, dig holes and search for contributing units in the background grid for the blade body-fitting grid, and store the nesting relationship between the two. Taking the 0° azimuth position of the propeller disc plane as the reference, the blades synchronously start to move along the radial direction with variable diameters. As time (azimuth) changes, the blades move, and the nesting relationship between the rotor blade body-fitting grid and the background grid at each station is updated and stored.

[0078] Step 2.2.2. Apply a variable diameter displacement function to the blade body-fitting grid in the computational model of the variable diameter rotor flow field simulation: divide the blade rotation into 720 stations, that is, the time advancement step is 0.5° azimuth. Read the rotor blade body-fitting grid and background grid coordinates in the computational model of the variable diameter rotor flow field simulation, set the variable diameter displacement function according to the time step and act on the blade body-fitting grid area. Then set the overlapping grid in the computational model of the variable diameter rotor flow field simulation after applying the variable diameter displacement function to dynamic overlapping behavior, and then correct the grid unit to obtain the corrected computational model; use the above-mentioned URANS method based on the hybrid format to calculate the rotor flow field, initialize the flow field and repeat the update of the nested relationship in step 2.2.1, and update and record the flow field information at each station until the calculation is completed.

[0079] Step 2.2.3. Output the rotor flow field information (flow field isosurface vorticity diagram), vortex field evolution diagram (cross-sectional vorticity diagram), and aerodynamic load fluctuation changes (unsteady tension load diagram) during the diameter change process.

[0080] In order to obtain the unsteady aerodynamic behavior and flow mechanism of the rotor's dynamic variable diameter process, the present application also provides an embodiment using a NACA rotor blade model.

[0081] Configure the initial parameter conditions for variable diameter: the radius range is 0.8R~1.2R, R represents the initial radius. The variable diameter speed uses a shape function related to the rotor cycle, the forward ratio in the forward flight state is 0.24, and the time advancement step is 0.25° azimuth. The speed function can be expressed as:

[0082]

[0083] Perform nesting initialization, dig holes and search for contribution units in the blade body-fitting grid in the background grid, and store the nesting relationship between the two; when the blade moves with time (azimuth), update and store the nesting relationship between the rotor blade body-fitting grid and the background grid at each station ( Figure 2 The above-mentioned URANS method is used to calculate the rotor flow field, initialize the flow field, and update and record the nesting relationship and flow field information at each station until the calculation is completed.

[0084] Output the flow field information, eddy field evolution diagram, and aerodynamic load fluctuation changes of the established NACA rotor model during the diameter change process.

[0085] pass Figure 3 It can be seen that the rotor aerodynamic force and flow field simulation method disclosed in this application effectively simulates the unsteady aerodynamic loads during the sudden increase in total pitch, and the fit is good, indicating that the rotor aerodynamic force and flow field simulation method can effectively simulate the unsteady flow field.

[0086] Figure 4 The comparison diagram of unsteady pulling force load during the variable diameter rotor in hovering state is given. Figure 4 Part (a) is a comparison of the unsteady tensile loads during the variable diameter rotor process in the hovering state when the diameter increases. Figure 4Part (b) is a comparison chart of the unsteady thrust load during the variable diameter rotor in the hovering state when the diameter is reduced, considering the two cases of dynamic increase and dynamic decrease of the rotor diameter. It can be seen that the change of the rotor thrust load increases with the increase of the variable diameter amplitude; in the process of uniform variable diameter, the thrust shows a monotonic linear change trend with time; when the variable diameter movement stops, the thrust amplitude will monotonically fall back, forming a typical "overshoot response" behavior, and the overshoot and fallback process of the thrust change is closely related to the variable diameter amplitude; whether it is dynamic elongation or dynamic telescoping, the larger the absolute value of the blade diameter, the more obvious the overshoot.

[0087] Figure 5 From the perspective of the evolution law of the vortex field, the cross-sectional vorticity cloud diagram of the rotor during the process of changing diameter is given. Figure 5 Part (a) shows the evolution of the vortex field when the diameter increases. The cross-sectional vorticity cloud diagram of the rotor in the process of changing diameter is given. Figure 5 Part (b) shows the evolution law of the vortex field when the diameter decreases, and gives the cross-sectional vortex cloud diagram of the rotor during the process of changing diameter. It can be seen that as the blade changes diameter, an induced trailing vortex appears on the blade surface under the action of the spanwise flow, and the trailing vortex gradually moves toward the root / tip of the blade as the blade lengthens / shortens. When the blade is extended, the vortex trajectory develops toward the inner section and gradually collides and merges with the previous blade tip vortex in the middle section of the blade. During the development process, the blade tip vortex cannot remain on the rotor motion trajectory and gradually shrinks and merges inward. When the blade is shortened, the vortex moves toward the outer section of the blade tip, gradually expands outward as a whole, and gradually dissipates.

[0088] Figure 6 The comparison diagram of unsteady thrust load in the process of variable diameter rotor in forward flight is given. Figure 6 Part (a) in the middle is a comparison diagram of the unsteady thrust loads during the variable diameter rotor process in forward flight when the diameter increases. Figure 6 Part (b) is a comparison of the unsteady thrust loads of the variable diameter rotor in the forward flight state when the diameter is reduced. It can be seen that the rotor thrust load shows periodic fluctuations during the forward flight process. During the blade extension / contraction process, the larger the absolute value of the diameter, the more obvious the fluctuation of the rotor unsteady load.

[0089] Figure 7 The contour vorticity cloud diagram of the rotor changing diameter in the forward flight state is given. Figure 7 Part (a) in the middle is the contour vorticity cloud diagram of the rotor diameter change process in the forward flight state when the diameter increases. Figure 7The middle part (b) is the contour vorticity cloud of the rotor diameter change process in the forward flight state when the diameter decreases. It can be seen that in the forward flight, the tip vortices of each rotor blade form concentric vortex columns with the flow and develop towards the rear space. As the diameter decreases, the boundary of the vortex column shows an expansion trend. Under the action of the spanwise flow, the tip vortex collides with the surface of different blades. The rolling phenomenon of the secondary shedding vortex formed by the rotor wake during the movement is more obvious, and the boundary of the overall vortex column shows a contraction trend as the diameter increases.

[0090] The steps of this application are to construct a Cartesian background grid and a variable diameter blade body-fitting grid system, and to establish a calculation model of the dynamic variable diameter of the rotor based on the Cartesian background grid and the variable diameter blade body-fitting grid. In the established calculation model, a CFD method for solving the flow field in the process of dynamic variable diameter of the rotor is established, and the rotor aerodynamic force and flow field are simulated, and the rotor aerodynamic performance analysis is performed based on the simulation results.

[0091] This application discloses the following technical effects:

[0092] 1. It can effectively capture the unsteady aerodynamic loads during the dynamic diameter change of the rotor. It can study the aerodynamic behaviors and unsteady aerodynamic characteristics such as the spanwise motion of the blade tip vortex, complex blade vortex interference, and vortex-vortex interference caused by the dynamic change of the rotor diameter.

[0093] 2. Based on the URANS equations and motion nested grids, a high-precision analysis method suitable for simulating the unsteady aerodynamic behavior of rotors with dynamic variable diameter is developed. The hybrid format is used to solve the rotor flow field, which can effectively capture the aerodynamic characteristics, unsteady phenomena and eddy field evolution mechanism during the rotor diameter change process, and can provide theoretical guidance for the dynamic variable diameter strategy of variable diameter intelligent rotors.

[0094] 3. It can effectively simulate the variable diameter rotor flow field, and can more accurately calculate the unsteady aerodynamic loads and reveal the evolution mechanism of the vortex field.

[0095] 4. The applicability of variable diameter rotor CFD simulation has been increased, the difficulty of understanding and processing data has been reduced, and this technology can be extended to areas such as wings / missile wings.

[0096] 5. Solving the variable diameter rotor flow field based on the hybrid format can effectively capture the development law of the rotor flow field wake during changes and improve the calculation accuracy of the rotor aerodynamic load.

[0097] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A rotor aerodynamic and flow field simulation method, characterized in that: The rotor aerodynamic force and flow field simulation method comprises: Generate blade body-fitting grid and construct Cartesian background grid according to rotor configuration parameters; A computational model for simulating the flow field of a variable diameter rotor is constructed based on the blade body-fitting grid and the Cartesian background grid; In the constructed calculation model for variable diameter rotor flow field simulation, a high-precision CFD method suitable for solving the variable diameter rotor flow field is established, and the rotor aerodynamic force and flow field in the dynamic variable diameter process are simulated, and the CFD calculation results are output.

2. The rotor aerodynamic and flow field simulation method according to claim 1, characterized in that: Generate blade body-fitted mesh according to rotor configuration parameters, including: Generate a two-dimensional airfoil mesh according to rotor configuration parameters; A three-dimensional blade mesh is constructed based on the two-dimensional airfoil mesh as the blade body-fitted mesh.

3. The rotor aerodynamic and flow field simulation method according to claim 1, characterized in that: A computational model for simulating the flow field of a variable diameter rotor is constructed based on the blade body-fitting grid and the Cartesian background grid, specifically including: A computational model for variable diameter rotor flow field simulation is constructed by using a moving nested grid method and an applied displacement function method; the moving nested grid method includes digging holes, contributing unit search and interpolation; the applied displacement function method is to apply a variable diameter displacement function to the blade body-fitting grid.

4. The rotor aerodynamic and flow field simulation method according to claim 1, characterized in that: In the constructed computational model for variable diameter rotor flow field simulation, a high-precision CFD method suitable for solving the variable diameter rotor flow field is established, specifically including: The unsteady Reynolds-averaged NS equations are used as the control equations to numerically simulate the unsteady flow field of the rotor with dynamically variable diameter. After the numerical simulation is completed, the grid-centered finite volume method is used to numerically discretize the spatial grid information in the simulation results to obtain the final calculation model; during the numerical discretization process, the convective flux at the interface of the grid unit is calculated using the Roe format, and the flow state quantities on both sides of the grid surface are obtained by interpolation using the MUSCL / CD scheme.

5. The rotor aerodynamic and flow field simulation method according to claim 4, characterized in that: Simulate the rotor aerodynamic force and flow field during the dynamic diameter change process and output CFD calculation results, including: Perform nesting initialization, dig holes and search for contributing units in the blade body-fitting grid in the background grid, and store the nesting relationship between the two; when the blade moves with time or azimuth, update and store the nesting relationship between the rotor blade body-fitting grid and the background grid at each station; Applying a variable diameter displacement function to the blade body-fitting grid in the computational model for variable diameter rotor flow field simulation; The overlapping grids in the computational model of the variable diameter rotor flow field simulation after applying the variable diameter displacement function are set to dynamic overlapping behavior, and then the grid units are corrected to obtain the corrected computational model; The final calculation model is used to calculate the rotor flow field of the modified calculation model, the flow field is initialized and the nested relationship is repeatedly updated, and the flow field information at each station is updated and recorded until the calculation is completed, and the CFD calculation results are output.

6. The rotor aerodynamic and flow field simulation method according to claim 1, characterized in that: The CFD calculation results include: unsteady tensile load diagram, cross-sectional vorticity diagram and flow field isosurface vorticity diagram.

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