Helicopter rotor blade-vortex interference noise suppression effect analysis method and system

Abstract

The invention belongs to the technical field of helicopters, and relates to a helicopter rotor blade-vortex interference noise suppression effect analysis method and system. The method comprises the following steps: establishing a CFD model for solving a helicopter rotor paddle-vortex interference flow field; establishing a CSD model for solving the helicopter rotor paddle-vortex interference flow field; establishing a coupling model; carrying out helicopter rotor paddle-vortex interference flow field simulation; establishing an FW-H model, and performing BVI noise calculation on the rotor blade; establishing an HHC numerical calculation model; and evaluating the inhibition effect of the HHC numerical calculation model on the BVI noise. According to the method, the unsteady effect of the blade can be fully considered, the unsteady air load on the surface of the rotor blade can be accurately simulated, the blade elastic deformation and the aeroelastic coupling effect caused by the HHC numerical calculation model are further deeply considered, the actual dynamic behavior of the blade is simulated, and then the prediction precision of the HHC numerical calculation model on the BVI noise suppression effect is enhanced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of helicopters, and in particular relates to a method and system for analyzing the suppression effect of rotor blade-vortex interaction noise of a helicopter. BACKGROUND

[0002] Helicopters are widely used in rescue, medical treatment, cargo transportation, police service and fire fighting due to their vertical take-off and landing, low-speed flight and high maneuverability. However, helicopter noise, especially the blade-vortex interaction (BVI) noise generated by the interaction of the shedding vortex at the tip of the rotor blade and the rear rotor blade, is a long-term problem, which not only affects the sound environment of the residential area around the helicopter, but also reduces the comfort in the cabin. Therefore, controlling BVI noise is crucial for reducing noise pollution and improving passenger experience.

[0003] Higher Harmonic Control (HHC) is an effective method for controlling BVI noise, but the existing methods for evaluating the suppression effect have deficiencies. The free wake method uses a digital blowing method to calculate the aerodynamic force data of the airfoil, without considering the unsteady effects of time-dependent changes in the flow field (such as vortex generation and shedding, and pulsating pressure, etc.), which cannot accurately simulate the unsteady air load on the surface of the rotor blade, resulting in significant deviations between the calculated aerodynamic force data and the actual situation, and thus leading to large errors in the prediction results of the BVI noise suppression effect. The method of Computational Fluid Dynamics (CFD) assumes that the rotor blade is rigid, without considering the elastic deformation of the rotor blade (such as flapping and twisting, etc.) and the aeroelastic coupling effect, which cannot reflect the actual dynamic behavior of the rotor blade, resulting in deviations between the simulation results of the flow field and aerodynamic force and the actual situation, and thus leading to large errors in the prediction results of the BVI noise suppression effect. SUMMARY

[0004] To solve the above technical problems, the present application provides a method and system for analyzing the suppression effect of rotor blade-vortex interaction noise of a helicopter.

[0005] In a first aspect, the present application provides a method for analyzing the suppression effect of rotor blade-vortex interaction noise of a helicopter, comprising: establishing a CFD model for solving the rotor blade-vortex interaction flow field of a helicopter to simulate the unsteady flow field, capture the interaction between the rotor blade and the vortex flow, and obtain the aerodynamic load and noise source information of the rotor blade; establishing a CSD model for solving the rotor blade-vortex interaction flow field of a helicopter as a structural dynamics model of the rotor blade to simulate the dynamic behavior of the rotor blade; A coupling model of the CFD model and the CSD model is established to describe the information transmission between the fluid and the solid; The dynamic behavior of the rotor blade is simulated by using the structural dynamics model, the rotor-pylon vortex interference flow field of the helicopter is simulated, and air pressure fluctuation data of the rotor blade region are obtained; the air pressure fluctuation data include rotor tip vortex flow field information, aerodynamic force data and pressure load data corresponding to the surface grid points of the rotor blade; An FW-H model for solving the rotor-pylon vortex interference noise of the helicopter is established, BVI noise calculation is performed on the rotor blade, and sound pressure fluctuation data of the microphone receiver position are calculated by using the air pressure fluctuation data; An HHC numerical calculation model for suppressing the rotor-pylon vortex interference noise of the helicopter is established, and the HHC numerical calculation model drives the rotor blade pitch by high harmonic excitation of the frequency related to the rotating speed; The suppression effect of the HHC numerical calculation model on the BVI noise is evaluated.

[0006] In the second aspect, the application provides a helicopter rotor-pylon vortex interference noise suppression effect analysis system, which comprises a first model establishment unit, a second model establishment unit, a third model establishment unit, a simulation unit, a fourth model establishment unit, a fifth model establishment unit and an evaluation unit; The first model establishment unit is used for establishing a CFD model for solving the rotor-pylon vortex interference flow field of the helicopter to simulate a non-steady flow field, capture the interaction between the rotor blade and the vortex flow, and obtain aerodynamic load and noise source information of the rotor blade; The second model establishment unit is used for establishing a CSD model for solving the rotor-pylon vortex interference flow field of the helicopter to simulate the dynamic behavior of the rotor blade as a structural dynamics model of the rotor blade; The third model establishment unit is used for establishing a coupling model of the CFD model and the CSD model to describe the information transmission between the fluid and the solid; The simulation unit is used for simulating the dynamic behavior of the rotor blade by using the structural dynamics model, simulating the rotor-pylon vortex interference flow field of the helicopter, and obtaining air pressure fluctuation data of the rotor blade region; the air pressure fluctuation data include rotor tip vortex flow field information, aerodynamic force data and pressure load data corresponding to the surface grid points of the rotor blade; The fourth model establishment unit is used for establishing an FW-H model for solving the rotor-pylon vortex interference noise of the helicopter to perform BVI noise calculation on the rotor blade, and calculate sound pressure fluctuation data of the microphone receiver position by using the air pressure fluctuation data; The fifth model establishment unit is used for establishing an HHC numerical calculation model for suppressing the rotor-pylon vortex interference noise of the helicopter, and the HHC numerical calculation model drives the rotor blade pitch by high harmonic excitation of the frequency related to the rotating speed; The evaluation unit is used to evaluate the suppression effect of the HHC numerical calculation model on BVI noise.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Optionally, a large eddy simulation model is used to solve the turbulence structure of the core fluid region near the main rotor, and a RANS model is used to solve the turbulence structure of the region other than the core fluid region near the main rotor.

[0009] Optional, set is the air density, is the average speed, is the average pressure, is the unit tensor, is the mean viscous stress tensor, is the volume force, Filter energy per unit mass, is the filtered heat flux, is the Reynolds stress tensor, and the solution variable is , the filter value is , the sub-filter value is , each solution variable Decompose into filtered values Sum filter value : , solving for the variable is one of the velocity component, pressure, energy and component concentration. The differential form of the control equation under the RANS model is expressed as: ; ; .

[0010] Furthermore, a CSD model for solving the helicopter rotor blade-vortex interaction flow field is established as a structural dynamics model of the rotor blade to simulate the dynamic behavior of the rotor blade, including: the CSD model uses the finite element method to obtain the control equation of the elastic motion of the rotor blade. The rotor blade is divided into several finite elements, each of which contains several degrees of freedom; the Hermite polynomials are used to describe the bending deformation of the flap, and the Lagrange polynomials are used to describe the elastic torsion deformation; the control equation of the elastic motion of the rotor blade is established according to the Hamiltonian variation principle, and it is assumed that It is A beam finite element, It's time, is the start time, It's the end time, is the total number of finite elements, is the change in strain energy, is the change in kinetic energy, The virtual work done by the aerodynamic load, the control equation of the elastic motion of the rotor blade is expressed as: .

[0011] Further, the coupling model of the CFD model and the CSD model is established to describe the information transmission between the fluid and the solid, including: calculating the CSD model to obtain the deformation of the rotor blade; input the grid of the deformed rotor blade into the CFD model; return the calculation results of the CFD model to the CSD model; repeat the iteration calculation until the structural deformation of the rotor blade and the air load converge.

[0012] Further, the structural dynamics model is used to simulate the dynamic behavior of the rotor blade, the helicopter rotor blade-vortex interaction flow field is simulated, and the air pressure fluctuation data of the rotor blade region are obtained, including: According to the basic geometric parameters of the rotor blade, a basic three-dimensional model of the rotor blade is created; The overlapping grid method is used to discretize the space according to the rotor blade flow field calculation domain; The large eddy simulation model and the RANS model are used to solve the turbulent structure of the rotor blade; The grid of the fuselage and the rotor blade is assigned to the solid region, and the background grid and the overlapping grid are assigned to the fluid region; Set the initial conditions, define the calculation parameters, the motion parameters of the rotor blade and the material properties of the rotor blade; Set the inlet and outlet boundary conditions, and set the boundary conditions of all wall surfaces; Set the solver parameters and execute the simulation process; Stop the calculation after the convergence setting time; Output the helicopter rotor blade tip vortex flow field information, aerodynamic force data and pressure load data corresponding to the rotor blade surface grid points.

[0013] Further, the FW-H model for solving the helicopter rotor blade-vortex interaction noise is established, the BVI noise calculation of the rotor blade is performed, and the sound pressure fluctuation data at the microphone receiver position is calculated using the air pressure fluctuation data, including: The continuity equation and the momentum equation are accurately rearranged into the form of the inhomogeneous wave equation to obtain the FW-H model, the sound pressure at the observer position is calculated according to the free space Green function, and the pressure disturbance radiated by the fluid on the surface of the rotor blade to the far-field microphone position is set as: and Pi and P2 represent the sound pressure caused by the thickness noise and the load noise respectively, is the far-field density, represents the surface velocity component perpendicular to the surface, represents the sound source surface, represents the observation point position, is the component of the surface Mach number in the propagation direction, subscript and represents the terms in the radial and normal directions, is the Mach number of the source fixed on the undisturbed medium, Representative Observer The pressure per unit area of ​​the fluid in the direction, 、 and The points on the graph represent the derivatives with respect to time, and in the denominator, they have The terms of the factor are far-field terms with The dependent terms are near-field terms, and the denominator The term is the Doppler factor term, which amplifies the signal and is responsible for frequency shift control. When it is close to 1, it is called Doppler amplification, and the subscript ret represents the delay time. represents the quantity calculated at the delay time. By integrating the FW-H equation at the delay time, the sound pressure time signal at the observation point is obtained. The FW-H equation is expressed as follows: ; ; .

[0014] Furthermore, a numerical calculation model of HHC for suppressing helicopter rotor-vortex interference noise is established, including: setting is the propeller pitch, is the total distance, For the The azimuth angle of the rotor blades, and are the cosine and sine components of the periodic pitch variation, is the high-order harmonic control input, To control the amplitude, To control the phase, the transfer matrix is ​​T and the response vector is , the response vector Including the vertical, longitudinal, and lateral loads and the cosine and sine components of the pitch and roll moments of the rotor blades, is the uncontrolled response vector, and the reference input is , is the objective function of the HHC optimization process, and are diagonal matrices, for Assign relative weights, for The relative weight is allocated, and the expression of the rotor blade variable pitch motion is represented by the relative azimuth angle of the rotor blade, and the expression is as follows: ; ; The blade variable pitch control equation is represented as follows: ; The HHC model is equivalent to a more general static nonlinear description of a first-order Taylor series expansion: ; The transfer matrix T is the Jacobian matrix of the first-order Taylor series expansion with respect to a reference input : ; The optimal control input pitch is determined based on the minimization problem of the quadratic performance index: : .

[0015] Further, by comparing the noise test data, the suppression effect of the HHC numerical calculation model on the BVI noise is evaluated, including: by calculating the noise without applying the HHC numerical calculation model and applying the HHC numerical calculation model, comparing the noise peak values and positions of the two, and comparing the influence of the HHC numerical calculation model on the noise maximum value.

[0016] The beneficial effects of the present application are: the consistency of the calculation results of the present application with the experimental data is significantly better than that of the traditional CFD method, therefore, when using the CFD / CSD coupling method to solve the rotor blade-vortex interaction flow field under high-order harmonic control, the present application can not only fully consider the unsteady effect of the blade, accurately simulate the unsteady air load on the surface of the rotor blade, but also deeply consider the elastic deformation of the blade caused by the HHC numerical calculation model and the aeroelastic coupling effect, simulate the actual dynamic behavior of the blade, and further enhance the prediction accuracy of the BVI noise suppression effect of the HHC numerical calculation model. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The principle diagram of the helicopter rotor blade-vortex interaction noise suppression effect analysis method provided for embodiment 1 of the present application is shown in the figure; Figure 2 The schematic diagram of the microphone array is shown in the figure; Figure 2 (a) in the figure is a front view; Figure 2 (b) in the figure is a top view; Figure 3 The contour plot of the BVI noise level experimental results and calculation results under HHC control is shown in the figure; Figure 3 (a) in the figure is the noise level experimental results without applying HHC control;Figure 3 (b) is the noise level experimental result when HHC control is applied; Figure 3 (c) in the figure is the noise level calculation result of the traditional CFD method when HHC control is applied; Figure 3 (d) is the noise level calculation result of the present invention when HHC control is applied; Figure 4 This is a schematic diagram of the helicopter rotor blade-vortex interference noise suppression effect analysis system provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0019] Example 1 As an example, Figure 1 As shown, in order to solve the above technical problems, this embodiment provides a method for analyzing the effect of suppressing helicopter rotor-vortex interference noise, including: A CFD model (Computational Fluid Dynamics) was developed to solve the helicopter rotor-vortex interaction flow field. This model simulates the unsteady flow field, captures the interaction between the rotor blades and the vortex, and obtains information on the rotor blade aerodynamic loads and noise sources. A CSD model (Computational Solid Dynamics) was established to solve the helicopter rotor blade-vortex interaction flow field and used as a structural dynamics model to simulate the dynamic behavior of the rotor blade. Establish a coupling model between CFD model and CSD model to describe the information transfer between fluid and solid; Using a structural dynamics model to simulate the dynamic behavior of rotor blades, a helicopter rotor-vortex interaction flow field simulation was performed to obtain air pressure pulsation data in the rotor blade area. The air pressure pulsation data includes rotor tip vortex flow field information, aerodynamic data, and pressure load data corresponding to grid points on the rotor blade surface. Establish a FW-H model for solving helicopter rotor-vortex interference noise, calculate the BVI noise of the rotor blades, and use air pressure pulsation data to calculate the sound pressure fluctuation data at the microphone receiver position; A numerical calculation model for HHC (Higher Harmonic Control) was established to suppress helicopter rotor-vortex interference noise. The HHC numerical calculation model drives the rotor blades to change pitch through high harmonic excitation at a frequency related to the rotational speed. Evaluate the suppression effect of HHC numerical calculation model on BVI noise.

[0020] First, the computational fluid dynamics method is used to simulate the details of the unsteady flow field to capture the interaction between the rotor blades and the vortex and obtain the aerodynamic load and noise source information of the rotor blades; then, considering the elastic characteristics of the rotor blades and their significant influence on the aerodynamic performance, the computational solid mechanics method is used to perform dynamic modeling of the rotor blades; then, after establishing the CFD model and the CSD model respectively, the loose coupling strategy is applied to realize the data exchange between the fluid and the solid to solve the pressure pulsation data of the flow field near the main rotor; secondly, the FW-H model is established, and the obtained near-field air pressure pulsation data of the rotor blades are used to calculate the small-amplitude sound pressure fluctuations at the far-field microphone receiver position; finally, the HHC numerical calculation model for suppressing the blade-vortex interference noise is established to evaluate the effect of high-order harmonic control on the suppression of helicopter rotor-vortex interference noise.

[0021] When using CFD to solve the rotor blade-vortex interference flow field under high-order harmonic control, the present invention can not only fully consider the unsteady effects of the rotor blades and accurately simulate the unsteady air loads on the rotor blade surface, but also deeply consider the elastic deformation and aeroelastic coupling effects of the rotor blades caused by HHC, simulate the actual dynamic behavior of the rotor blades, and thus enhance the prediction accuracy of the HHC effect on BVI noise suppression.

[0022] Specifically, a CFD model for solving the helicopter rotor blade-vortex interaction flow field is established to simulate the rotor aerodynamic force and flow field characteristics under the blade-vortex interaction state, so as to obtain the air pressure pulsation data near the rotor blade.

[0023] Optionally, a large eddy simulation model is used to solve the turbulence structure of the core fluid region near the main rotor, and a RANS model is used to solve the turbulence structure of the region other than the core fluid region near the main rotor.

[0024] To improve accuracy and reduce computation time, a detached eddy simulation (DES) model was used to solve the turbulent structure. This model combines large eddy simulation (LES) with the Reynolds-averaged Navier-Stokes (RANS) model. The LES model is used to solve the turbulent structure in the core flow region near the main rotor, while the RANS model is used in other regions. This approach not only avoids the excessive number of meshes associated with using the LES turbulence model as a whole, but also ensures accurate analysis of the turbulent structure of noise sources near the main rotor.

[0025] Specifically, is the air density, is the average speed, is the average pressure, is the unit tensor, is the mean viscous stress tensor, is the volume force, Filter energy per unit mass, is the filtered heat flux, is the Reynolds stress tensor, and the solution variable is , the filter value is , the sub-filter value is , each solution variable Decompose into filtered values Sum filter value : , solving for the variable is one of the velocity component, pressure, energy and component concentration. The differential form of the control equation under the RANS model is expressed as: ; ; .

[0026] The CSD method is used to construct a structural dynamic model of the rotor blade, aiming to accurately simulate the dynamic behaviors of the rotor blade, such as torsion and flapping. The CSD model uses the finite element method to obtain the discrete equations that control the elastic motion of the rotor blade. The blade is divided into several finite elements. Preferably, each finite element contains 15 degrees of freedom, and the deformation distribution within each unit is represented by an appropriate interpolation polynomial. Hermite polynomials are used for flap bending deformation, which can ensure the continuity of displacement and slope between units. For elastic torsional deformation, Lagrange polynomials are used to ensure the continuity of displacement. Specifically, the control equations of the elastic motion of the rotor blade are established based on the Hamiltonian variation principle.

[0027] Optionally, a CSD model for solving the helicopter rotor blade-passage vortex interference flow field is established as a structural dynamics model of the rotor blade to simulate the dynamic behavior of the rotor blade, including: the CSD model uses a finite element method to obtain control equations of elastic motion of the rotor blade, the rotor blade is divided into a plurality of finite elements, each finite element contains a plurality of degrees of freedom; a Hermite polynomial is used to describe the flap bending deformation, and a Lagrange polynomial is used to describe the elastic torsion deformation; control equations of elastic motion of the rotor blade are established according to the Hamiltonian variation principle, and the control equations of elastic motion of the rotor blade are represented as: is the first beam finite element, is time, is a start time, is an end time, is a total number of finite elements, is a change in strain energy, is a change in kinetic energy, is virtual work done by aerodynamic loads, and the control equations of elastic motion of the rotor blade are represented as: .

[0028] Optionally, a coupling model of the CFD model and the CSD model is established to describe information transmission between the fluid and the solid, including: the CSD model is calculated to obtain deformation of the rotor blade; the grid of the deformed rotor blade is input into the CFD model; the calculation result of the CFD model is returned to the CSD model; the iterative calculation is repeated until the structural deformation of the rotor blade and the air load converge.

[0029] After the CFD model and the CSD model are established respectively, a loose coupling CFD / CSD strategy is used to realize information transmission between the fluid and the structure.

[0030] Optionally, the structural dynamics model is used to simulate the dynamic behavior of the rotor blade, the helicopter rotor blade-passage vortex interference flow field simulation is performed, and air pressure fluctuation data of the rotor blade region are obtained, including: A basic three-dimensional model of the rotor blade is created according to basic geometric parameters of the rotor blade; specifically, the basic three-dimensional model of the rotor is created according to basic geometric parameters of the rotor such as the number of blades, the length, the chord length, the twist angle, the shape of the leading edge and the trailing edge, the airfoil profile, etc. The specific steps of creating the basic three-dimensional model also include defining the center line of the rotor blade (usually the rotor shaft) and each cross section (airfoil profile) of the rotor blade, ensuring that the curved surface is smooth and has no mutation or discontinuity to meet the requirements of aerodynamics.

[0031] ​The space of the flow field calculation domain of the rotor blade is discretized by using the overlapping grid method; specifically, the blade movement includes periodic rotation, pitch change and flapping movement, in order to deal with the complex relative movement between the rotor blades, the space of the flow field calculation domain of the rotor blades is discretized by using the overlapping grid method. The grid system of the simulation of the interaction between the rotor blades and the fuselage based on the overlapping grid includes the background grid of the complete calculation domain around the fuselage and the overlapping grid area moving with the rotor blades around the rotor blades. The overlapping grid and the background grid exchange data directly through the overlapping grid cell layer, in the area where the grids overlap, the size of the overlapping grid and the background grid is set to be the same, so that the two are matched, and the data exchange error is reduced. The minimum grid size of the blade surface and the fuselage surface is set to be 0.05 and 0.1 times the chord length of the blade respectively, so as to ensure the accuracy of the simulation.

[0032] The large eddy simulation model and the RANS model are used to solve the turbulent structure of the rotor blade; The grids of the fuselage and the rotor blades are distributed to the solid area, and the background grid and the overlapping grid are distributed to the fluid area; The initial conditions are set, and the calculation parameters, the movement parameters of the rotor blades and the material properties of the rotor blades are defined; the material properties of the rotor blades such as the elastic modulus, the density and the Poisson's ratio are set; The inlet and outlet boundary conditions are set, and the boundary conditions of all the walls are set; The solver parameters are set, and the simulation process is executed; in order to simulate the periodic movement of the blade, the rotation of the rotor blade is divided into 360 intervals by calculation, that is, the time step is the time of the rotation of 1° azimuth angle; The calculation is stopped after the convergence setting time; The information of the tip vortex flow field of the helicopter rotor, the aerodynamic force data and the pressure load data corresponding to the surface grid points of the rotor blade are output.

[0033] Optionally, the FW-H model for solving the rotor-vortex interference noise of the helicopter rotor is established, the BVI noise of the rotor blade is calculated, and the sound pressure fluctuation data at the microphone receiver position are calculated by using the air pressure fluctuation data, including: the continuity equation and the momentum equation are accurately rearranged into the form of the inhomogeneous wave equation to obtain the FW-H model, the sound pressure at the observer position is calculated according to the free space Green function, and for the pressure disturbance radiated by the fluid on the surface of the rotor blade to the far-field microphone position, it is set that and respectively represent the sound pressure caused by the thickness noise and the load noise, is the far-field density, represents the surface velocity component perpendicular to the surface, represents the sound source surface, represents the observer position, is the component of the surface Mach number in the propagation direction, subscript and represent the radial and normal components, is the source Mach number with respect to the fixed, undisturbed medium, represents the observer direction, , and denote the derivative with respect to time, in the denominator, the term with factor is the far field term, the term with dependence is the near field term, the term in the denominator is the Doppler factor term, the Doppler factor amplifies the signal and is responsible for the frequency shift control, when is close to 1, it is called Doppler amplification, subscript ret represents the retardation time, denotes the quantity computed at the retardation time, by integrating the FW-H equation at the retardation time, the sound pressure time signal at the observer position is obtained; the FW-H equation is expressed as follows: ; ; .

[0034] Optionally, let be the pitch, be the collective pitch, be the azimuth angle of the th rotor blade, and be the cosine and sine components of the cyclic pitch respectively, be the high order harmonic control input, be the control amplitude, be the control phase, the transfer matrix is T, the response vector is , the response vector includes the cosine and sine components of the vertical, longitudinal, lateral loads and the pitch, roll moments of the rotor blades, is the uncontrolled response vector, the reference input is , is the objective function of the HHC optimization process, and are the diagonal matrices respectively, is the relative weight assigned to , is the relative weight assigned to , the rotor blade pitch motion expression is expressed by using the rotor blade relative azimuth angle as​ ; ; The blade pitch control equation is expressed as: ; The HHC model is equivalent to a first-order Taylor series expansion of a more general static nonlinear description: ; The transfer matrix T is the Jacobian matrix of the first-order Taylor series expansion with respect to a reference input Calculation: ; Determining the optimal control input pitch based on minimization of quadratic performance index : .

[0035] Optionally, the noise test data is compared to evaluate the suppression effect of the HHC numerical calculation model on BVI noise, including: calculating the noise without applying the HHC numerical calculation model and with applying the HHC numerical calculation model, comparing the noise peaks and positions of the two, and comparing the influence of the HHC numerical calculation model on the maximum value of the noise.

[0036] A four-blade, hingeless rotor was studied, and noisy test data was used for comparison. The BVI flow field simulation and BVI noise prediction simulation of the rotor blades were used as examples to evaluate the effectiveness of the 3 / rev HHC on BVI noise suppression. The calculations were performed using a 6-degree descent flight condition from the test, which corresponds to the BVI condition during low-speed descent flight.

[0037] Attachment Figure 2 A schematic diagram of the microphone array is shown, with Figure 2 (a) is the main view, Figure 2 (b) shows a top view. The array is used to generate noise level contour maps, which can be used to assess the BVI noise level. To evaluate the effectiveness of HHC on BVI noise suppression, the sound pressure level (SPL) was used as a metric. By calculating the noise levels without and with HHC control, the noise peaks and locations were compared, and the specific impact of HHC on the maximum noise level was further analyzed.

[0038] As attached Figure 3 The contour map of the experimental and calculated results of BVI noise level under HHC control is shown. The horizontal axis is the abscissa of the microphone array, unit: m, and the vertical axis is the ordinate of the microphone array, unit: m; Indicates rotor advance ratio, noise level unit: dB. Figure 3 (a) is the noise level experimental result when HHC control is not applied, and the maximum noise level is 115.5dB; Figure 3 (b) is the noise level experimental result when HHC control is applied, and the maximum noise level is 112.8dB; Figure 3 (c) is the noise level calculation result of the traditional CFD method when HHC control is applied, and the maximum noise level is 112.6dB; Figure 3 (d) in the figure is the noise level calculation result of the present invention when HHC control is applied, and the maximum noise level is 112.7dB. The position and size of the noise peak in the calculation results of the present invention are closer to the experimental results. The results show that the degree of agreement between the calculation results of the present invention and the experimental data is significantly better than that of the traditional CFD method. Therefore, when the present invention uses the CFD / CSD coupling method to solve the rotor blade-vortex interference flow field under high-order harmonic control, it can not only fully consider the unsteady effect of the blade and accurately simulate the unsteady air load on the surface of the rotor blade, but also deeply consider the elastic deformation and aeroelastic coupling effect of the blade caused by the HHC numerical calculation model, simulate the actual dynamic behavior of the blade, and thus enhance the prediction accuracy of the HHC numerical calculation model on the BVI noise suppression effect.

[0039] Example 2 Based on the same principle as the method shown in Example 1 of the present invention, as shown in the attached Figure 4 As shown, an embodiment of the present invention further provides a helicopter rotor blade-vortex interference noise suppression effect analysis system, including a first model building unit, a second model building unit, a third model building unit, a simulation unit, a fourth model building unit, a fifth model building unit and an evaluation unit; The first model building unit is used to build a CFD model to solve the helicopter rotor blade-vortex interaction flow field to simulate the unsteady flow field, capture the interaction between the rotor blade and the vortex, and obtain the rotor blade aerodynamic load and noise source information; The second model building unit is used to build a CSD model for solving the helicopter rotor blade-vortex interaction flow field as a structural dynamics model of the rotor blade to simulate the dynamic behavior of the rotor blade; The third model building unit is used to build a coupling model between the CFD model and the CSD model to describe the information transfer between the fluid and the solid; The simulation unit is used to simulate the dynamic behavior of the rotor blades using a structural dynamics model, perform helicopter rotor-vortex interaction flow field simulation, and obtain air pressure pulsation data in the rotor blade area; the air pressure pulsation data includes rotor tip vortex flow field information, aerodynamic data, and pressure load data corresponding to grid points on the rotor blade surface; The fourth model building unit is used to establish a FW-H model for solving helicopter rotor blade-vortex interference noise, calculate the BVI noise of the rotor blades, and calculate the sound pressure fluctuation data at the microphone receiver position using air pressure pulsation data; The fifth model building unit is used to establish an HHC numerical calculation model for suppressing helicopter rotor blade-vortex interference noise. The HHC numerical calculation model drives the rotor blade to change the pitch through high harmonic excitation of a frequency related to the rotation speed; The evaluation unit is used to evaluate the suppression effect of the HHC numerical calculation model on BVI noise.

[0040] Optionally, a large eddy simulation model is used to solve the turbulence structure of the core fluid region near the main rotor, and a RANS model is used to solve the turbulence structure of the region other than the core fluid region near the main rotor.

[0041] Optional, set is the air density, is the average speed, is the average pressure, is the unit tensor, is the mean viscous stress tensor, is the volume force, Filter energy per unit mass, is the filtered heat flux, is the Reynolds stress tensor, and the solution variable is , the filter value is , the sub-filter value is , each solution variable Decompose into filtered values Sum filter value : , solving for the variable is one of the velocity component, pressure, energy and component concentration. The differential form of the control equation under the RANS model is expressed as: ; ; .

[0042] Optionally, a CSD model for solving the helicopter rotor blade-vortex interference flow field is established as a structural dynamics model of the rotor blade to simulate the dynamic behavior of the rotor blade, including: the CSD model uses the finite element method to obtain the control equation of the elastic motion of the rotor blade, the rotor blade is divided into several finite elements, each finite element contains several degrees of freedom; the Hermite polynomial is used to describe the bending deformation of the flap, and the Lagrange polynomial is used to describe the elastic torsion deformation; the control equation of the elastic motion of the rotor blade is established according to the Hamiltonian variation principle, and it is assumed It is beam finite element, is the time, is the start time, is the end time, is the total number of finite elements, is the change of strain energy, is the change of kinetic energy, is the virtual work done by the aerodynamic load, then the control equation of the elastic motion of the rotor blade is expressed as: .

[0043] Optionally, a coupling model of the CFD model and the CSD model is established to describe the information transmission between the fluid and the solid, including: calculating the CSD model to obtain the deformation of the rotor blade; inputting the grid of the deformed rotor blade into the CFD model; returning the calculation results of the CFD model to the CSD model; repeating the iterative calculation until the structural deformation of the rotor blade and the air load converge.

[0044] Optionally, the structural dynamics model is used to simulate the dynamic behavior of the rotor blade, the helicopter rotor blade-vortex interaction flow field simulation is performed, and the air pressure fluctuation data of the rotor blade region are obtained, including: a basic three-dimensional model of the rotor blade is created according to the basic geometric parameters of the rotor blade; the spatial discretization of the rotor blade flow field calculation domain is performed by using the overset grid method; the large eddy simulation model and the RANS model are used to solve the turbulent structure of the rotor blade; the grid of the fuselage and the rotor blade is assigned to the solid region, and the background grid and the overset grid are assigned to the fluid region; initial conditions are set, calculation parameters, motion parameters of the rotor blade and material properties of the rotor blade are defined; the inlet and outlet boundary conditions are set, and the boundary conditions of all wall surfaces are set; the solver parameters are set, and the simulation process is executed; the calculation is stopped after the convergence setting time; the helicopter rotor blade tip vortex flow field information, aerodynamic force data and pressure load data corresponding to the surface grid points of the rotor blade are output.

[0045] Optionally, the FW-H model for solving the helicopter rotor blade-vortex interaction noise is established, the BVI noise calculation of the rotor blade is performed, and the sound pressure fluctuation data at the microphone receiver position are calculated by using the air pressure fluctuation data, including: the continuity equation and the momentum equation are accurately rearranged into the form of the inhomogeneous wave equation to obtain the FW-H model, the sound pressure at the observer position is calculated according to the free space Green function, and for the pressure disturbance radiated by the surface fluid of the rotor blade to the far-field microphone position, it is: and denote the sound pressure caused by thickness noise and loading noise respectively, is the far-field density, represents the surface velocity component normal to the surface, represents the surface of the sound source, represents the location of the observation point, is the component of the surface Mach number in the propagation direction, subscript and represents the terms in the radial and normal directions, is the Mach number of the source fixed on the undisturbed medium, Representative Observer The pressure per unit area of ​​the fluid in the direction, 、 and The points on the graph represent the derivatives with respect to time, and in the denominator, they have The terms of the factor are far-field terms with The dependent terms are near-field terms, and the denominator The term is the Doppler factor term, which amplifies the signal and is responsible for frequency shift control. When it is close to 1, it is called Doppler amplification, and the subscript ret represents the delay time. represents the quantity calculated at the delay time. By integrating the FW-H equation at the delay time, the sound pressure time signal at the observation point is obtained. The FW-H equation is expressed as follows: ; ; .

[0046] Optionally, establish a HHC numerical calculation model for suppressing helicopter rotor-vortex interference noise, including: setting is the propeller pitch, is the total distance, For the The azimuth angle of the rotor blades, and are the cosine and sine components of the periodic pitch variation, is the high-order harmonic control input, To control the amplitude, To control the phase, the transfer matrix is ​​T and the response vector is , the response vector Including the vertical, longitudinal, and lateral loads and the cosine and sine components of the pitch and roll moments of the rotor blades, is the uncontrolled response vector, and the reference input is , is the objective function of the HHC optimization process, and are diagonal matrices, for Assign relative weights, for Assign relative weights and use the relative azimuth angle of the rotor blades to express the rotor blade pitch motion expression as follows: ; ; The blade pitch control equation is expressed as: ; The HHC model is equivalent to a first-order Taylor series expansion of a more general static nonlinear description: ; The transfer matrix T is the Jacobian matrix of the first-order Taylor series expansion with respect to a reference input Calculation: ; Determining the optimal control input pitch based on minimization of quadratic performance index : .

[0047] Optionally, the noise test data is compared to evaluate the suppression effect of the HHC numerical calculation model on BVI noise, including: calculating the noise without applying the HHC numerical calculation model and with applying the HHC numerical calculation model, comparing the noise peaks and positions of the two, and comparing the influence of the HHC numerical calculation model on the maximum value of the noise.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for analyzing the effect of suppressing helicopter rotor-vortex interference noise, characterized in that: include: Establish a CFD model to solve the helicopter rotor-vortex interaction flow field to simulate the unsteady flow field, capture the interaction between the rotor blades and the vortex, and obtain the rotor blade aerodynamic load and noise source information; A CSD model for solving helicopter rotor blade-vortex interaction flow field is established as the structural dynamics model of the rotor blade to simulate the dynamic behavior of the rotor blade. Establish a coupling model between CFD model and CSD model to describe the information transfer between fluid and solid; Using a structural dynamics model to simulate the dynamic behavior of rotor blades, a helicopter rotor-vortex interaction flow field simulation was performed to obtain air pressure pulsation data in the rotor blade area. The air pressure pulsation data includes rotor tip vortex flow field information, aerodynamic data, and pressure load data corresponding to grid points on the rotor blade surface. Establish a FW-H model for solving helicopter rotor-vortex interference noise, calculate the BVI noise of the rotor blades, and use air pressure pulsation data to calculate the sound pressure fluctuation data at the microphone receiver position; A HHC numerical calculation model for suppressing helicopter rotor-vortex interference noise is established. The HHC numerical calculation model drives the rotor blade pitch through high harmonic excitation at a frequency related to the rotational speed. Evaluate the suppression effect of HHC numerical calculation model on BVI noise.

2. The method for analyzing the effect of suppressing helicopter rotor-vortex interference noise according to claim 1, characterized in that: The large eddy simulation model is used to solve the turbulent structure of the core fluid region near the main rotor, and the RANS model is used to solve the turbulent structure of the region outside the core fluid region near the main rotor.

3. The method for analyzing the effect of suppressing helicopter rotor-vortex interference noise according to claim 1, characterized in that: set up is the air density, is the average speed, is the average pressure, is the unit tensor, is the mean viscous stress tensor, is the volume force, Filter energy per unit mass, is the filtered heat flux, is the Reynolds stress tensor, and the solution variable is , the filter value is , the sub-filter value is , each solution variable Decompose into filtered values Sum filter value : , solving for the variable is one of the velocity component, pressure, energy and component concentration. The differential form of the control equation under the RANS model is expressed as: ； ； 。 4. The method for analyzing the effect of suppressing helicopter rotor-vortex interference noise according to claim 1, characterized in that: A CSD model for solving the helicopter rotor blade-vortex interaction flow field is established as a structural dynamics model of the rotor blade to simulate the dynamic behavior of the rotor blade, including: the CSD model uses the finite element method to obtain the control equation of the elastic motion of the rotor blade. The rotor blade is divided into several finite elements, each of which contains several degrees of freedom; the Hermite polynomials are used to describe the bending deformation of the flap, and the Lagrange polynomials are used to describe the elastic torsion deformation; the control equation of the elastic motion of the rotor blade is established according to the Hamiltonian variation principle, and it is assumed that It is A beam finite element, It's time, is the start time, It's the end time, is the total number of finite elements, is the change in strain energy, is the change in kinetic energy, is the virtual work done by the aerodynamic load, then the governing equation for the elastic motion of the rotor blade is expressed as: 。 5. The method for analyzing the effect of suppressing helicopter rotor-vortex interference noise according to claim 1, characterized in that: A coupling model between the CFD model and the CSD model is established to describe the information transfer between the fluid and the solid. This includes: calculating the CSD model to obtain the deformation of the rotor blade; inputting the mesh of the deformed rotor blade into the CFD model; returning the calculation results of the CFD model to the CSD model; and repeating the iterative calculation until the structural deformation and air load of the rotor blade converge.

6. The method for analyzing the effect of suppressing helicopter rotor-vortex interference noise according to claim 1, characterized in that: The dynamic behavior of the rotor blades is simulated using a structural dynamics model. The helicopter rotor-vortex interaction flow field is simulated to obtain air pressure pulsation data in the rotor blade area, including: Create a basic three-dimensional model of the rotor blade according to the basic geometric parameters of the rotor blade; The overlapping grid method is used to discretize the computational domain of the rotor blade flow field; The large eddy simulation model and RANS model are used to solve the turbulent structure of the rotor blades; Assign the fuselage and rotor blade meshes to the solid region, and the background mesh and overlay meshes to the fluid region; Set initial conditions, define calculation parameters, rotor blade motion parameters, and rotor blade material properties; Set the inlet and outlet boundary conditions, and set the boundary conditions of all walls; Set the solver parameters and execute the simulation process; Stop calculation after converging to set time; Output helicopter rotor blade tip vortex field information, aerodynamic data and pressure load data corresponding to the rotor blade surface grid points.

7. The method for analyzing the effect of suppressing helicopter rotor-vortex interference noise according to claim 1, characterized in that: A FW-H model for solving helicopter rotor-vortex interference noise is established, and the BVI noise of the rotor blades is calculated. The sound pressure fluctuation data at the microphone receiver position is calculated using air pressure pulsation data. This includes accurately rearranging the continuity equation and momentum equation into the form of an inhomogeneous wave equation to obtain the FW-H model. The sound pressure at the observer position is calculated based on the free-space Green's function. For the pressure disturbance radiated from the fluid on the rotor blade surface to the far-field microphone position, it is assumed that: and denote the sound pressure caused by thickness noise and loading noise respectively, is the far-field density, represents the surface velocity component normal to the surface, represents the surface of the sound source, represents the observation point location, is the component of the surface Mach number in the propagation direction, subscript and represents the terms in the radial and normal directions, is the Mach number of the source fixed on the undisturbed medium, Representative Observer The pressure per unit area of ​​the fluid in the direction, 、 and The points on the graph represent the derivatives with respect to time, and in the denominator, they have The terms of the factor are far-field terms with The dependent terms are near-field terms, and the denominator The term is the Doppler factor term, which amplifies the signal and is responsible for frequency shift control. When it is close to 1, it is called Doppler amplification, and the subscript ret represents the delay time. represents the quantity calculated at the delay time. By integrating the FW-H equation at the delay time, the sound pressure time signal at the observation point is obtained. The FW-H equation is expressed as follows: ； ； 。 8. The method for analyzing the effect of suppressing helicopter rotor-vortex interference noise according to claim 1, characterized in that: Establish a HHC numerical calculation model for suppressing helicopter rotor-vortex interference noise, including: setting is the propeller pitch, is the total distance, For the The azimuth angle of the rotor blades, and are the cosine and sine components of the periodic pitch variation, is the high-order harmonic control input, To control the amplitude, To control the phase, the transfer matrix is ​​T and the response vector is , the response vector Including the vertical, longitudinal, and lateral loads and the cosine and sine components of the pitch and roll moments of the rotor blades, is the uncontrolled response vector, and the reference input is , is the objective function of the HHC optimization process, and are diagonal matrices, for Assign relative weights, for Assign relative weights and use the relative azimuth angle of the rotor blades to express the rotor blade pitch motion expression as follows: ； ； The blade pitch control equation is expressed as: ； The HHC model is equivalent to a first-order Taylor series expansion of a more general static nonlinear description: ； The transfer matrix T is the Jacobian matrix of the first-order Taylor series expansion with respect to a reference input Calculation: ； Determining the optimal control input pitch based on minimization of quadratic performance index : 。 9. The method for analyzing the effect of suppressing helicopter rotor-vortex interference noise according to claim 1, characterized in that: The noise test data were compared to evaluate the suppression effect of the HHC numerical calculation model on BVI noise, including: calculating the noise without and with the HHC numerical calculation model, comparing the noise peaks and positions between the two, and comparing the impact of the HHC numerical calculation model on the maximum noise value.

10. Helicopter rotor blade-vortex interference noise suppression effect analysis system, characterized in that: It includes a first model building unit, a second model building unit, a third model building unit, a simulation unit, a fourth model building unit, a fifth model building unit and an evaluation unit; The first model building unit is used to build a CFD model to solve the helicopter rotor blade-vortex interaction flow field to simulate the unsteady flow field, capture the interaction between the rotor blade and the vortex, and obtain the rotor blade aerodynamic load and noise source information; The second model building unit is used to build a CSD model for solving the helicopter rotor blade-vortex interaction flow field as a structural dynamics model of the rotor blade to simulate the dynamic behavior of the rotor blade; The third model building unit is used to build a coupling model between the CFD model and the CSD model to describe the information transfer between the fluid and the solid; The simulation unit is used to simulate the dynamic behavior of the rotor blades using a structural dynamics model, perform helicopter rotor-vortex interaction flow field simulation, and obtain air pressure pulsation data in the rotor blade area; the air pressure pulsation data includes rotor tip vortex flow field information, aerodynamic data, and pressure load data corresponding to grid points on the rotor blade surface; The fourth model building unit is used to establish a FW-H model for solving helicopter rotor blade-vortex interference noise, calculate the BVI noise of the rotor blades, and calculate the sound pressure fluctuation data at the microphone receiver position using air pressure pulsation data; The fifth model building unit is used to establish an HHC numerical calculation model for suppressing helicopter rotor blade-vortex interference noise. The HHC numerical calculation model drives the rotor blade to change the pitch through high harmonic excitation of a frequency related to the rotation speed; The evaluation unit is used to evaluate the suppression effect of the HHC numerical calculation model on BVI noise.

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