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

Abstract

This invention belongs to the field of helicopter technology and relates to a method and system for analyzing the suppression effect of helicopter rotor blade-vortex interference noise. The method includes: establishing a CFD model to solve the helicopter rotor blade-vortex interference flow field; establishing a CSD model to solve the helicopter rotor blade-vortex interference flow field; establishing a coupling model; performing helicopter rotor blade-vortex interference flow field simulation; establishing an FW-H model to calculate BVI noise for the rotor blades; establishing an HHC numerical calculation model; and evaluating the suppression effect of the HHC numerical calculation model on BVI noise. This invention not only fully considers the unsteady effects of the blades and accurately simulates the unsteady air loads on the rotor blade surface, but also deeply considers the blade elastic deformation and aeroelastic coupling effects caused by the HHC numerical calculation model, simulating the actual dynamic behavior of the blades, thereby enhancing the prediction accuracy of the HHC numerical calculation model for BVI noise suppression.

Description

Technical Field

[0001] This invention belongs to the field of helicopter technology, and more specifically, relates to a method and system for analyzing the noise suppression effect of helicopter rotor blade-vortex interference. Background Technology

[0002] Helicopters are widely used in rescue, medical, cargo, policing, and firefighting fields due to their vertical takeoff and landing, low-speed flight, and high maneuverability. However, helicopter noise, especially blade-vortex interference (BVI) noise generated by the interaction between shedding vortices at the rotor blade tips and the rear rotor blades, is a long-standing problem. It not only affects the acoustic environment of residential areas around the helicopter but also reduces cabin comfort. 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; however, existing methods for evaluating its suppression effect have shortcomings. The free wake method uses digital airflow analysis to calculate aerodynamic data for the airfoil, neglecting unsteady effects of time-dependent flow field changes (such as vortex generation and shedding, and pulsating pressure). This fails to accurately simulate unsteady air loads on the rotor blade surface, leading to significant deviations between the calculated aerodynamic data and actual conditions, resulting in large errors in the predicted BVI noise suppression effect. Computational fluid dynamics (CFD) methods assume rigid rotor blades, failing to consider elastic deformation (such as flapping and torsion) and aeroelastic coupling effects. This fails to reflect the actual dynamic behavior of the rotor blades, causing deviations between the simulated flow field and aerodynamic results and actual conditions, further contributing to large errors in the predicted BVI noise suppression effect. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method and system for analyzing the suppression effect of helicopter rotor blade-vortex interference noise.

[0005] In a first aspect, the present invention provides a method for analyzing the suppression effect of helicopter rotor blade-vortex interference noise, including:

[0006] A CFD model was established to solve the unsteady flow field of helicopter rotor blade-vortex interference, capture the interaction between rotor blades and vortices, and obtain information on rotor blade aerodynamic loads and noise sources.

[0007] 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.

[0008] Establish a coupled model of CFD and CSD models to describe the information transfer between fluid and solid;

[0009] The dynamic behavior of the rotor blades was simulated using a structural dynamics model to simulate the rotor blade-vortex interference flow field of a helicopter, and the air pressure pulsation data of the rotor blade region was obtained. 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.

[0010] An FW-H model for solving helicopter rotor blade-vortex interference noise was established, BVI noise was calculated for rotor blades, and sound pressure fluctuation data at the microphone receiver location was calculated using air pressure pulsation data.

[0011] A numerical calculation model for HHC (helicopter rotor-vortex interference) is established to suppress helicopter rotor blade pitch 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.

[0012] Evaluate the HHC numerical calculation model's suppression effect on BVI noise.

[0013] Secondly, the present invention provides a helicopter rotor blade-vortex interference noise suppression effect analysis system, including 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;

[0014] The first model building unit is used to build a CFD model to solve the unsteady flow field of the helicopter rotor blade-vortex interference flow field, capture the interaction between the rotor blade and the vortex, and obtain information on the aerodynamic load and noise source of the rotor blade.

[0015] The second model building unit is used to build a CSD model for solving the helicopter rotor blade-vortex interference flow field as a structural dynamics model of the rotor blade to simulate the dynamic behavior of the rotor blade.

[0016] The third model building unit is used to build a coupled model of the CFD model and the CSD model to describe the information transfer between the fluid and the solid.

[0017] The simulation unit is used to simulate the dynamic behavior of rotor blades using structural dynamics models, to simulate the rotor blade-vortex interference flow field of helicopter rotor blades, and to obtain air pressure pulsation data in the rotor blade region; 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;

[0018] The fourth model building unit is used to build the FW-H model for solving the helicopter rotor blade-vortex interference noise, perform BVI noise calculation on the rotor blades, and use air pressure pulsation data to calculate the sound pressure fluctuation data at the microphone receiver location.

[0019] The fifth model building unit is used to build an HHC numerical calculation model to suppress helicopter rotor blade-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.

[0020] The evaluation unit is used to evaluate the HHC numerical calculation model's suppression effect on BVI noise.

[0021] Based on the above technical solution, the present invention can be further improved as follows.

[0022] Optionally, a large eddy simulation model can be used to solve the turbulent structure in the core fluid region near the main rotor, while a RANS model can be used to solve the turbulent structure in the region outside the core fluid region near the main rotor.

[0023] Optional, set air density, It is the average speed. It is the average pressure. It is a unit tensor. It is the mean viscous stress tensor. It is a volume force. Filtering energy per unit mass It is the filtered heat flux. It is the Reynolds stress tensor, and the solution variables are: The filter value is The sub-filter value is Each solution variable Decomposed into filtered values Sub-filter values : Solve for variables Given one of the velocity component, pressure, energy, and component concentration, the differential form of the governing equations in the RANS model is expressed as:

[0024] ;

[0025] ;

[0026] .

[0027] Furthermore, 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 its dynamic behavior. This includes: using the finite element method to obtain the governing equations for the elastic motion of the rotor blade in the CSD model, where the rotor blade is divided into several finite elements, each containing several degrees of freedom; using Hermite polynomials to describe flap bending deformation and Lagrange polynomials to describe elastic torsional deformation; and establishing the governing equations for the elastic motion of the rotor blade based on the Hamiltonian variational principle. It is the first Finite element method for beam, It is time. It is the start time. It is the end time. It is the total number of finite elements. It is a change in strain energy. For the change of kinetic energy, The virtual work done for the aerodynamic load is then expressed as the governing equation for the elastic motion of the rotor blades:

[0028] .

[0029] Furthermore, a coupled model of the CFD model and the CSD model is established to describe the information transfer between the fluid and the solid, including: 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; repeating iterative calculations until the structural deformation and air load of the rotor blade converge.

[0030] Furthermore, the dynamic behavior of the rotor blades was simulated using a structural dynamics model, and the helicopter rotor blade-vortex interference flow field was simulated to obtain air pressure fluctuation data in the rotor blade region, including:

[0031] Create a basic three-dimensional model of the rotor blade based on its basic geometric parameters;

[0032] The overlapping grid method is used to discretize the computational domain of the rotor blade flow field.

[0033] The turbulent structure of the rotor blades was solved using the large eddy simulation model and the RANS model.

[0034] Assign the meshes for the fuselage and rotor blades to the solid region, and assign the background mesh and overlapping meshes to the fluid region;

[0035] Set initial conditions, define calculation parameters, rotor blade motion parameters, and rotor blade material properties;

[0036] Set the inlet and outlet boundary conditions, and set the boundary conditions for all walls;

[0037] Set the solver parameters and execute the simulation process;

[0038] The calculation stops after a set convergence time.

[0039] Output helicopter rotor blade tip vortex field information, aerodynamic data, and pressure load data corresponding to grid points on the rotor blade surface.

[0040] Furthermore, a Free-Wave-H model for solving helicopter rotor blade-vortex interference noise is established. BVI noise is calculated for the rotor blades, and sound pressure fluctuation data at the microphone receiver location is calculated using air pressure pulsation data. This includes: accurately rearranging the continuity and momentum equations into non-uniform wave equations to obtain the FW-H model; calculating the sound pressure at the observer location based on the free-space Green's function; and considering the pressure disturbance radiated from the rotor blade surface to the far-field microphone location, assuming:

[0041] and These represent the sound pressure levels caused by thickness noise and load noise, respectively. For far-field density, This represents the surface velocity component perpendicular to the surface. Indicates the surface of the sound source. Indicates the location of the observation point. It is the component of the surface Mach number in the direction of propagation, subscript and Terms representing radial and normal directions, It concerns the source Mach number fixed on an undisturbed medium. Representative observer The pressure per unit area on the fluid in the direction of its movement. , and The point on the denominator represents the derivative with respect to time, and in the denominator, it has... The term of the factor is the far-field term, which has The dependent term is the near-field term, and it is in the denominator. The term is the Doppler factor term. The Doppler factor amplifies the signal and is responsible for frequency shift control. When the value is close to 1, it is called Doppler amplification, and the subscript ret represents the delay time. This represents the quantity calculated over the delay time. By integrating the FW-H equation over the delay time, the sound pressure time signal at the observation point is obtained. The FW-H equation is expressed as follows:

[0042] ;

[0043] ;

[0044] .

[0045] Furthermore, a numerical calculation model for HHC (Helicopter Hurricane Control) to suppress helicopter rotor-vortex interference noise is established, including: setting... For propeller pitch, For the total distance, For the first The azimuth angle of each rotor blade. and These are the cosine and sine components of the periodic pitch, respectively. For high-order harmonic control input, To control the amplitude, To control the phase, the transfer matrix is ​​T, and the response vector is... Response vector This includes the cosine and sine components of the vertical, longitudinal, and lateral loads on the rotor blades, as well as the pitch and roll moments. It is an uncontrolled response vector, with the reference input being... , The objective function for the HHC optimization process is... and They are diagonal matrices. for Assign relative weights, for By assigning relative weights and using the relative azimuth angles of the rotor blades, the expression for the variable pitch motion of the rotor blades is as follows:

[0046] ;

[0047] ;

[0048] The control equation for variable blade pitch is expressed as:

[0049] ;

[0050] The HHC model is equivalent to a first-order Taylor series expansion of a more general static nonlinear description:

[0051] ;

[0052] The transfer matrix T is the Jacobian matrix of the first-order Taylor series expansion with respect to a reference input. Calculation:

[0053] ;

[0054] Determining the optimal control input pitch based on minimizing a quadratic performance index :

[0055] .

[0056] Furthermore, by comparing noise test data, the suppression effect of the HHC numerical calculation model on BVI noise is evaluated, including: by calculating the noise without applying the HHC numerical calculation model and with applying the HHC numerical calculation model, comparing the noise peak and location of the two, and comparing the impact of the HHC numerical calculation model on the maximum noise value.

[0057] The beneficial effects of this invention are: the calculation results of this invention are in significantly better agreement with experimental data than those of the traditional CFD method. Therefore, when using the CFD / CSD coupling method to solve the rotor blade-vortex interference flow field under high-order harmonic control, this invention can not only fully consider the unsteady effect of the blade and accurately simulate the unsteady air load on the rotor blade surface, but also take into account the blade elastic deformation and aeroelastic coupling effect 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 for BVI noise suppression. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the helicopter rotor blade-vortex interference noise suppression effect analysis method provided in Embodiment 1 of the present invention;

[0059] Figure 2 A schematic diagram of a microphone array; attached. Figure 2 (a) is the main view; Appendix Figure 2 (b) is the top view;

[0060] Figure 3 Contour plots showing experimental and calculated BVI noise levels under HHC control; attached. Figure 3 (a) shows the experimental results of the noise level without HHC control; Appendix Figure 3 (b) shows the experimental results of the noise level when HHC control is applied; Appendix Figure 3 (c) in the figure represents the noise level calculation result of the traditional CFD method when HHC control is applied; Appendix Figure 3 (d) represents the noise level calculation result of the present invention when HHC control is applied;

[0061] Figure 4 This is a schematic diagram of the helicopter rotor blade-vortex interference noise suppression effect analysis system provided in Embodiment 1 of the present invention. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0063] Example 1

[0064] As an example, see the attached document. Figure 1 As shown, to solve the above-mentioned technical problems, this embodiment provides a method for analyzing the suppression effect of helicopter rotor blade-vortex interference noise, including:

[0065] A CFD (Computational Fluid Dynamics) model is established to solve the flow field of helicopter rotor blade-vortex interference, simulate the unsteady flow field, capture the interaction between rotor blades and vortices, and obtain information on rotor blade aerodynamic loads and noise sources.

[0066] A CSD (Computational Solid Dynamics) model for solving the flow field of helicopter rotor blade-vortex interference is established as a structural dynamics model of rotor blade to simulate the dynamic behavior of rotor blade;

[0067] Establish a coupled model of CFD and CSD models to describe the information transfer between fluid and solid;

[0068] The dynamic behavior of the rotor blades was simulated using a structural dynamics model to simulate the rotor blade-vortex interference flow field of a helicopter, and the air pressure pulsation data of the rotor blade region was obtained. 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.

[0069] An FW-H model for solving helicopter rotor blade-vortex interference noise was established, BVI noise was calculated for rotor blades, and sound pressure fluctuation data at the microphone receiver location was calculated using air pressure pulsation data.

[0070] A numerical calculation model for HHC (Higher Harmonic Control) to suppress helicopter rotor blade-vortex interference noise was established. The HHC numerical calculation model drives the rotor blades to change pitch through high harmonic excitation with a frequency related to the rotational speed.

[0071] Evaluate the HHC numerical calculation model's suppression effect on BVI noise.

[0072] First, computational fluid dynamics (CFD) is used to simulate the details of the unsteady flow field, thereby capturing the interaction between the rotor blades and vortices and obtaining information on the aerodynamic loads and noise sources of the rotor blades. Next, considering the elastic characteristics of the rotor blades and their significant impact on aerodynamic performance, computational solid mechanics (CSM) is used to model the dynamics of the rotor blades. Then, after establishing CFD and CSD models respectively, a loose coupling strategy is applied to achieve data exchange between the fluid and solid components to solve for the pressure pulsation data of the flow field near the main rotor. Second, an FW-H model is established, and using the obtained near-field air pressure pulsation data of the rotor blades, small-amplitude sound pressure fluctuations at the far-field microphone receiver location are calculated. Finally, an HHC numerical calculation model for suppressing propeller vortex interference noise is established, and the effect of high-order harmonic control on suppressing helicopter rotor propeller-vortex interference noise is evaluated.

[0073] When using CFD to solve the rotor blade-vortex interference flow field under high-order harmonic control, this invention not only fully considers the unsteady effects of rotor blades and accurately simulates the unsteady air loads on the rotor blade surface, but also takes into account the elastic deformation and aeroelastic coupling effects of rotor blades caused by HHC, simulating the actual dynamic behavior of rotor blades, thereby enhancing the prediction accuracy of HHC on BVI noise suppression effect.

[0074] Specifically, a CFD model for solving the rotor-vortex interference flow field of a helicopter is established to simulate the rotor aerodynamics and flow field characteristics under rotor-vortex interference conditions, in order to obtain air pressure pulsation data in the near field of the rotor blades.

[0075] Optionally, a large eddy simulation model can be used to solve the turbulent structure in the core fluid region near the main rotor, while a RANS model can be used to solve the turbulent structure in the region outside the core fluid region near the main rotor.

[0076] To improve computational accuracy while reducing computation time, a detached eddy simulation (DES) model is used to solve the turbulent structure. The DES model combines Large Eddy Simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) models. LES is used to solve the turbulent structure in the core fluid region near the main rotor, while RANS is used for other regions. This approach avoids the excessive mesh count problem associated with using LES as the sole turbulence model and ensures the accuracy of the turbulent structure analysis of noise sources near the main rotor.

[0077] Specifically, let's set air density, It is the average speed. It is the average pressure. It is a unit tensor. It is the mean viscous stress tensor. It is a volume force. Filtering energy per unit mass It is the filtered heat flux. It is the Reynolds stress tensor, and the solution variables are: The filter value is The sub-filter value is Each solution variable Decomposed into filtered values Sub-filter values : Solve for variables Given one of the velocity component, pressure, energy, and component concentration, the differential form of the governing equations in the RANS model is expressed as:

[0078] ;

[0079] ;

[0080] .

[0081] A structural dynamics model of the rotor blade is constructed using the CSD method to accurately simulate its dynamic behaviors, such as torsion and flapping. The CSD model employs the finite element method to obtain discrete equations governing the elastic motion of the rotor blade. The blade is divided into several finite element units, preferably each containing 15 degrees of freedom. The deformation distribution within each element is represented using appropriate interpolation polynomials. Hermite polynomials are used for flap bending deformation to ensure the continuity of displacement and slope between elements. For elastic torsional deformation, Lagrange polynomials are used to guarantee displacement continuity. Specifically, the governing equations for the elastic motion of the rotor blade are established based on the Hamiltonian variational principle.

[0082] 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 its dynamic behavior. This includes: obtaining the governing equations for the elastic motion of the rotor blade using the finite element method in the CSD model; dividing the rotor blade into several finite elements, each containing several degrees of freedom; using Hermite polynomials to describe flap bending deformation and Lagrange polynomials to describe elastic torsional deformation; and establishing the governing equations for the elastic motion of the rotor blade based on the Hamiltonian variational principle. It is the first Finite element method for beam, It is time. It is the start time. It is the end time. It is the total number of finite elements. It is a change in strain energy. For the change of kinetic energy, The virtual work done for the aerodynamic load is then expressed as the governing equation for the elastic motion of the rotor blades:

[0083] .

[0084] Optionally, a coupled model of the CFD model and the CSD model can be established to describe the information transfer between the fluid and the solid, including: 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; repeating the iterative calculation until the structural deformation and air load of the rotor blade converge.

[0085] After establishing CFD and CSD models respectively, a loosely coupled CFD / CSD strategy is adopted to realize the information transfer between fluid and structure.

[0086] Optionally, the dynamic behavior of the rotor blades can be simulated using a structural dynamics model to perform a helicopter rotor blade-vortex interference flow field simulation, obtaining air pressure fluctuation data in the rotor blade region, including:

[0087] A basic three-dimensional model of the rotor blade is created based on its basic geometric parameters. Specifically, a basic three-dimensional model of the rotor is created based on the basic geometric parameters of the rotor, such as the number of blades, length, chord length, twist angle, leading and trailing edge shapes, and airfoil profile. The specific steps for creating the basic three-dimensional model also include defining the centerline of the rotor blade (usually the rotor axis) and each section of the rotor blade (airfoil profile) to ensure that the surface is smooth and without abrupt changes or discontinuities, in order to meet aerodynamic requirements.

[0088] An overlapping mesh method is used to discretize the computational domain of the rotor blade flow field. Specifically, the blade motion includes periodic rotation, pitch variation, and flapping motion. To handle the complex relative motion between rotor blades, an overlapping mesh method is used to discretize the computational domain of the rotor blade flow field. The mesh system for simulating the interaction between the rotor blade and the fuselage based on the overlapping mesh consists of a background mesh representing the complete computational domain around the fuselage and an overlapping mesh region around the rotor blades that moves with the rotor blades. The overlapping mesh and the background mesh exchange data directly through overlapping mesh cell layers. In the overlapping mesh region, the sizes of the overlapping mesh and the background mesh are set to be the same to match them and reduce data exchange errors. The minimum mesh size for the blade surface and the fuselage surface is set to... To ensure the requirements of the blade boundary layer, polyhedral meshes with dimensions of 0.05 and 0.1 times the blade chord length were used in the rotating region and fuselage region, respectively, to ensure simulation accuracy.

[0089] The turbulent structure of the rotor blades was solved using the large eddy simulation model and the RANS model.

[0090] Assign the meshes for the fuselage and rotor blades to the solid region, and assign the background mesh and overlapping meshes to the fluid region;

[0091] Set initial conditions, define calculation parameters, rotor blade motion parameters, and rotor blade material properties; rotor blade material properties include elastic modulus, density, Poisson's ratio, etc.

[0092] Set the inlet and outlet boundary conditions, and set the boundary conditions for all walls;

[0093] Set the solver parameters and execute the simulation process; to simulate the periodic motion of the rotor blade, the rotor blade rotation is divided into 360 intervals by calculation, that is, the time advance step is the time of rotating 1° azimuth angle;

[0094] The calculation stops after a set convergence time.

[0095] Output helicopter rotor blade tip vortex field information, aerodynamic data, and pressure load data corresponding to grid points on the rotor blade surface.

[0096] Optionally, an FW-H model is established to solve for helicopter rotor blade-vortex interference noise. BVI noise is calculated for the rotor blades, and sound pressure fluctuation data at the microphone receiver location is calculated using air pressure pulsation data. This includes: accurately rearranging the continuity and momentum equations into non-uniform wave equations to obtain the FW-H model; calculating the sound pressure at the observer location based on the free-space Green's function; and considering the pressure disturbance radiated from the rotor blade surface to the far-field microphone location, assuming:

[0097] and These represent the sound pressure levels caused by thickness noise and load noise, respectively. For far-field density, This represents the surface velocity component perpendicular to the surface. Indicates the surface of the sound source. Indicates the location of the observation point. It is the component of the surface Mach number in the direction of propagation, subscript and Terms representing radial and normal directions, It concerns the source Mach number fixed on an undisturbed medium. Representative observer The pressure per unit area on the fluid in the direction of its movement. , and The point on the denominator represents the derivative with respect to time, and in the denominator, it has... The term of the factor is the far-field term, which has The dependent term is the near-field term, and it is in the denominator. The term is the Doppler factor term. The Doppler factor amplifies the signal and is responsible for frequency shift control. When the value is close to 1, it is called Doppler amplification, and the subscript ret represents the delay time. This represents the quantity calculated over the delay time. By integrating the FW-H equation over the delay time, the sound pressure time signal at the observation point is obtained. The FW-H equation is expressed as follows:

[0098] ;

[0099] ;

[0100] .

[0101] Optional, set For propeller pitch, For the total distance, For the first The azimuth angle of each rotor blade. and These are the cosine and sine components of the periodic pitch, respectively. For high-order harmonic control input, To control the amplitude, To control the phase, the transfer matrix is ​​T, and the response vector is... Response vector This includes the cosine and sine components of the vertical, longitudinal, and lateral loads on the rotor blades, as well as the pitch and roll moments. It is an uncontrolled response vector, with the reference input being... , The objective function for the HHC optimization process is... and They are diagonal matrices. for Assign relative weights, for By assigning relative weights and using the relative azimuth angles of the rotor blades, the expression for the variable pitch motion of the rotor blades is as follows:

[0102] ;

[0103] ;

[0104] The control equation for variable blade pitch is expressed as:

[0105] ;

[0106] The HHC model is equivalent to a first-order Taylor series expansion of a more general static nonlinear description:

[0107] ;

[0108] The transfer matrix T is the Jacobian matrix of the first-order Taylor series expansion with respect to a reference input. Calculation:

[0109] ;

[0110] Determining the optimal control input pitch based on minimizing a quadratic performance index :

[0111] .

[0112] Optionally, the suppression effect of the HHC numerical calculation model on BVI noise can be evaluated by comparing noise test data, including: calculating the noise without applying the HHC numerical calculation model and with applying the HHC numerical calculation model, comparing the noise peak and location of the two, and comparing the impact of the HHC numerical calculation model on the maximum noise value.

[0113] Taking a four-bladed articulated rotor as the research object, and using noisy experimental data as a comparison, the BVI flow field simulation and BVI noise prediction simulation of the rotor blades are used as examples to evaluate the suppression effect of 3 / rev HHC on BVI noise. The experimental state of 6-degree descent flight was selected for calculation, which corresponds to the BVI conditions during low-speed descent flight.

[0114] Appendix Figure 2 A schematic diagram of the microphone array is shown, with appendix. Figure 2 (a) is the main view, with appendix... Figure 2 (b) in the diagram is a top view. This array is used to generate noise level contour maps, which can be used to assess the level of BVI noise. To evaluate the suppression effect of HHC on BVI noise, the noise level (SPL) is used as a metric. The noise level is calculated with and without HHC control, and the noise peaks and locations are compared. The specific impact of HHC on the maximum noise value is further analyzed.

[0115] As attached Figure 3 The contour plots shown are of the experimental and calculated results of the BVI noise level under HHC control. The horizontal axis is the horizontal coordinate of the microphone array (unit: m), and the vertical axis is the vertical coordinate of the microphone array (unit: m). Indicates the rotor advance ratio; noise level is measured in dB. (Appendix) Figure 3 (a) shows the experimental results for the noise level without HHC control, with a maximum noise level of 115.5 dB; Appendix Figure 3 (b) shows the experimental results of the noise level when HHC control is applied, with a maximum noise level of 112.8 dB; Appendix Figure 3(c) shows the noise level calculation result of the traditional CFD method when HHC control is applied, with a maximum noise level of 112.6 dB; Appendix Figure 3 In the figure, (d) represents the noise level calculation result of the present invention under HHC control, with a maximum noise level of 112.7 dB. The location and magnitude of the noise peak in the calculation results of the present invention are closer to the experimental results. The results show that the calculation results of the present invention are in significantly better agreement with the experimental data than the traditional CFD method. Therefore, when using the CFD / CSD coupling method to solve the rotor blade-vortex interference flow field under high-order harmonic control, the present invention can not only fully consider the unsteady blade effect and accurately simulate the unsteady air load on the rotor blade surface, but also deeply consider the blade elastic deformation and aeroelastic coupling effect 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 for BVI noise suppression.

[0116] Example 2

[0117] Based on the same principle as the method shown in Embodiment 1 of the present invention, as illustrated in the appendix. Figure 4 As shown, the embodiments of the present invention also provide a helicopter rotor blade-vortex interference noise suppression effect analysis system, including 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;

[0118] The first model building unit is used to build a CFD model to solve the unsteady flow field of the helicopter rotor blade-vortex interference flow field, capture the interaction between the rotor blade and the vortex, and obtain information on the aerodynamic load and noise source of the rotor blade.

[0119] The second model building unit is used to build a CSD model for solving the helicopter rotor blade-vortex interference flow field as a structural dynamics model of the rotor blade to simulate the dynamic behavior of the rotor blade.

[0120] The third model building unit is used to build a coupled model of the CFD model and the CSD model to describe the information transfer between the fluid and the solid.

[0121] The simulation unit is used to simulate the dynamic behavior of rotor blades using structural dynamics models, to simulate the rotor blade-vortex interference flow field of helicopter rotor blades, and to obtain air pressure pulsation data in the rotor blade region; 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;

[0122] The fourth model building unit is used to build the FW-H model for solving the helicopter rotor blade-vortex interference noise, perform BVI noise calculation on the rotor blades, and use air pressure pulsation data to calculate the sound pressure fluctuation data at the microphone receiver location.

[0123] The fifth model building unit is used to build an HHC numerical calculation model to suppress helicopter rotor blade-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.

[0124] The evaluation unit is used to evaluate the HHC numerical calculation model's suppression effect on BVI noise.

[0125] Optionally, a large eddy simulation model can be used to solve the turbulent structure in the core fluid region near the main rotor, while a RANS model can be used to solve the turbulent structure in the region outside the core fluid region near the main rotor.

[0126] Optional, set air density, It is the average speed. It is the average pressure. It is a unit tensor. It is the mean viscous stress tensor. It is a volume force. Filtering energy per unit mass It is the filtered heat flux. It is the Reynolds stress tensor, and the solution variables are: The filter value is The sub-filter value is Each solution variable Decomposed into filtered values Sub-filter values : Solve for variables Given one of the velocity component, pressure, energy, and component concentration, the differential form of the governing equations in the RANS model is expressed as:

[0127] ;

[0128] ;

[0129] .

[0130] 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 its dynamic behavior. This includes: obtaining the governing equations for the elastic motion of the rotor blade using the finite element method in the CSD model; dividing the rotor blade into several finite elements, each containing several degrees of freedom; using Hermite polynomials to describe flap bending deformation and Lagrange polynomials to describe elastic torsional deformation; and establishing the governing equations for the elastic motion of the rotor blade based on the Hamiltonian variational principle. It is the first Finite element method for beam, It is time. It is the start time. It is the end time. It is the total number of finite elements. It is a change in strain energy. For the change of kinetic energy, The virtual work done for the aerodynamic load is then expressed as the governing equation for the elastic motion of the rotor blades:

[0131] .

[0132] Optionally, a coupled model of the CFD model and the CSD model can be established to describe the information transfer between the fluid and the solid, including: 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; repeating the iterative calculation until the structural deformation and air load of the rotor blade converge.

[0133] Optionally, the dynamic behavior of the rotor blades can be simulated using a structural dynamics model to perform a helicopter rotor blade-vortex interference flow field simulation, obtaining air pressure fluctuation data in the rotor blade region, including:

[0134] Create a basic three-dimensional model of the rotor blade based on its basic geometric parameters;

[0135] The overlapping grid method is used to discretize the computational domain of the rotor blade flow field.

[0136] The turbulent structure of the rotor blades was solved using the large eddy simulation model and the RANS model.

[0137] Assign the meshes for the fuselage and rotor blades to the solid region, and assign the background mesh and overlapping meshes to the fluid region;

[0138] Set initial conditions, define calculation parameters, rotor blade motion parameters, and rotor blade material properties;

[0139] Set the inlet and outlet boundary conditions, and set the boundary conditions for all walls;

[0140] Set the solver parameters and execute the simulation process;

[0141] The calculation stops after a set convergence time.

[0142] Output helicopter rotor blade tip vortex field information, aerodynamic data, and pressure load data corresponding to grid points on the rotor blade surface.

[0143] Optionally, an FW-H model is established to solve for helicopter rotor blade-vortex interference noise. BVI noise is calculated for the rotor blades, and sound pressure fluctuation data at the microphone receiver location is calculated using air pressure pulsation data. This includes: accurately rearranging the continuity and momentum equations into non-uniform wave equations to obtain the FW-H model; calculating the sound pressure at the observer location based on the free-space Green's function; and considering the pressure disturbance radiated from the rotor blade surface to the far-field microphone location, assuming:

[0144] and These represent the sound pressure levels caused by thickness noise and load noise, respectively. For far-field density, This represents the surface velocity component perpendicular to the surface. Indicates the surface of the sound source. Indicates the location of the observation point. It is the component of the surface Mach number in the direction of propagation, subscript and Terms representing radial and normal directions, It concerns the source Mach number fixed on an undisturbed medium. Representative observer The pressure per unit area on the fluid in the direction of its movement. , and The point on the denominator represents the derivative with respect to time, and in the denominator, it has... The term of the factor is the far-field term, which has The dependent term is the near-field term, and it is in the denominator. The term is the Doppler factor term. The Doppler factor amplifies the signal and is responsible for frequency shift control. When the value is close to 1, it is called Doppler amplification, and the subscript ret represents the delay time. This represents the quantity calculated over the delay time. By integrating the FW-H equation over the delay time, the sound pressure time signal at the observation point is obtained. The FW-H equation is expressed as follows:

[0145] ;

[0146] ;

[0147] .

[0148] Optionally, an HHC numerical calculation model for suppressing helicopter rotor-vortex interference noise is established, including: setting... For propeller pitch, For the total distance, For the first The azimuth angle of each rotor blade. and These are the cosine and sine components of the periodic pitch, respectively. For high-order harmonic control input, To control the amplitude, To control the phase, the transfer matrix is ​​T, and the response vector is... Response vector This includes the cosine and sine components of the vertical, longitudinal, and lateral loads on the rotor blades, as well as the pitch and roll moments. It is an uncontrolled response vector, with the reference input being... , The objective function for the HHC optimization process is... and They are diagonal matrices. for Assign relative weights, for By assigning relative weights and using the relative azimuth angles of the rotor blades, the expression for the variable pitch motion of the rotor blades is as follows:

[0149] ;

[0150] ;

[0151] The control equation for variable blade pitch is expressed as:

[0152] ;

[0153] The HHC model is equivalent to a first-order Taylor series expansion of a more general static nonlinear description:

[0154] ;

[0155] The transfer matrix T is the Jacobian matrix of the first-order Taylor series expansion with respect to a reference input. Calculation:

[0156] ;

[0157] Determining the optimal control input pitch based on minimizing a quadratic performance index :

[0158] .

[0159] Optionally, the suppression effect of the HHC numerical calculation model on BVI noise can be evaluated by comparing noise test data, including: calculating the noise without applying the HHC numerical calculation model and with applying the HHC numerical calculation model, comparing the noise peak and location of the two, and comparing the impact of the HHC numerical calculation model on the maximum noise value.

[0160] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for analyzing the noise suppression effect of helicopter rotor blade-vortex interference, characterized in that, include: A CFD model was established to solve the unsteady flow field of helicopter rotor blade-vortex interference, capture the interaction between rotor blades and vortices, and obtain information on rotor blade aerodynamic loads and noise sources. 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. Establish a coupled model of CFD and CSD models to describe the information transfer between fluid and solid; This study simulates the dynamic behavior of helicopter rotor blades using a structural dynamics model to perform a rotor-vortex interference flow field simulation, obtaining air pressure fluctuation data in the rotor blade region. The process includes: creating a basic 3D model of the rotor blade based on its fundamental geometric parameters; discretizing the computational domain of the rotor blade flow field using an overlapping mesh method; solving for the turbulent structure of the rotor blade using a large eddy simulation (LES) model and a RANS model; assigning the fuselage and rotor blade meshes to the solid region, and the background and overlapping meshes to the fluid region; setting initial conditions, defining computational parameters, rotor blade motion parameters, and rotor blade material properties; setting inlet and outlet boundary conditions, and setting boundary conditions for all walls; setting solver parameters and executing the simulation; stopping the calculation after a set convergence time; and outputting helicopter rotor blade tip vortex field information, aerodynamic data, and pressure load data corresponding to the mesh points on the rotor blade surface. The air pressure fluctuation data includes rotor blade tip vortex field information, aerodynamic data, and pressure load data corresponding to the mesh points on the rotor blade surface. An FW-H model for solving helicopter rotor blade-vortex interference noise was established, BVI noise was calculated for rotor blades, and sound pressure fluctuation data at the microphone receiver location was calculated using air pressure pulsation data. A numerical calculation model for HHC (helicopter rotor-vortex interference) is established to suppress helicopter rotor blade pitch 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 HHC numerical calculation model's suppression effect on BVI noise.

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

3. The method for analyzing the suppression effect of helicopter rotor blade-vortex interference noise according to claim 2, characterized in that, set up air density, It is the average speed. It is the average pressure. It is a unit tensor. It is the mean viscous stress tensor. It is a volume force. Filtering energy per unit mass It is the filtered heat flux. It is the Reynolds stress tensor, and the solution variables are: The filter value is The sub-filter value is Each solution variable Decomposed into filtered values Sub-filter values : Solve for variables Given one of the velocity component, pressure, energy, and component concentration, the differential form of the governing equations in the RANS model is expressed as: ； ； 。 4. The method for analyzing the suppression effect of helicopter rotor blade-vortex interference noise according to claim 1, characterized in that, 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 its dynamic behavior. This includes: using the finite element method to obtain the governing equations for the elastic motion of the rotor blade in the CSD model, where the rotor blade is divided into several finite element units, each containing several degrees of freedom; using Hermite polynomials to describe flap bending deformation and Lagrange polynomials to describe elastic torsional deformation; and establishing the governing equations for the elastic motion of the rotor blade based on the Hamiltonian variational principle. It is the first Finite element method for beam, It is time. It is the start time. It is the end time. It is the total number of finite elements. It is a change in strain energy. For the change of kinetic energy, The virtual work done for the aerodynamic load is then expressed as the governing equation for the elastic motion of the rotor blades: 。 5. The method for analyzing the suppression effect of helicopter rotor blade-vortex interference noise according to claim 1, characterized in that, A coupled model of CFD and CSD models is established to describe the information transfer between fluid and solid, including: 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; repeating iterative calculations until the structural deformation and air load of the rotor blade converge.

6. The method for analyzing the suppression effect of helicopter rotor blade-vortex interference noise according to claim 1, characterized in that, A Free-Wave-Helmet (FW-H) model is established to solve for helicopter rotor blade-vortex interference noise. BVI noise is calculated for the rotor blades, and sound pressure fluctuations at the microphone receiver location are calculated using air pressure pulsation data. This includes: accurately rearranging the continuity and momentum equations into non-uniform wave equations to obtain the FW-H model; calculating the sound pressure at the observer location based on the free-space Green's function; and considering the pressure disturbance radiated from the rotor blade surface to the far-field microphone location, assuming: This represents the sound pressure level caused by thickness noise. This represents the sound pressure level caused by load noise. For far-field density, This represents the surface velocity component perpendicular to the surface. Indicates the surface of the sound source. Indicates the location of the observation point. It is the component of the surface Mach number in the direction of propagation, subscript and Terms representing radial and normal directions, It concerns the source Mach number fixed on an undisturbed medium. Representative observer The pressure per unit area on the fluid in the direction of its movement. , and The point on the denominator represents the derivative with respect to time, and in the denominator, it has... The term of the factor is the far-field term, which has The dependent term is the near-field term, and it is in the denominator. The term is the Doppler factor term. The Doppler factor amplifies the signal and is responsible for frequency shift control. When the value is close to 1, it is called Doppler amplification, and the subscript ret represents the delay time. This represents the quantity calculated over the delay time. By integrating the FW-H equation over the delay time, the sound pressure time signal at the observation point is obtained. The FW-H equation is expressed as follows: ； ； 。 7. The method for analyzing the suppression effect of helicopter rotor blade-vortex interference noise according to claim 1, characterized in that, A numerical calculation model for HHC (Helicopter Hurricane Control) to suppress helicopter rotor-vortex interference noise was established, including: setting... For propeller pitch, For the total distance, For the first The azimuth angle of each rotor blade. and These are the cosine and sine components of the periodic pitch, respectively. For high-order harmonic control input, To control the amplitude, To control the phase, the transfer matrix is ​​T, and the response vector is... Response vector This includes the cosine and sine components of the vertical, longitudinal, and lateral loads on the rotor blades, as well as the pitch and roll moments. It is an uncontrolled response vector, with the reference input being... , The objective function for the HHC optimization process is... and They are diagonal matrices. for Assign relative weights, for By assigning relative weights and using the relative azimuth angles of the rotor blades, the expression for the variable pitch motion of the rotor blades is as follows: ； ； The control equation for variable blade pitch 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 minimizing a quadratic performance index : 。 8. The method for analyzing the suppression effect of helicopter rotor blade-vortex interference noise according to claim 1, characterized in that, The HHC numerical calculation model was evaluated for its suppression effect on BVI noise by comparing noise test data. This included calculating the noise without and with the HHC numerical calculation model, comparing the noise peaks and locations, and comparing the impact of the HHC numerical calculation model on the maximum noise value.

9. A system for analyzing the noise suppression effect of helicopter rotor blade-vortex interference, 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 unsteady flow field of the helicopter rotor blade-vortex interference flow field, capture the interaction between the rotor blade and the vortex, and obtain information on the aerodynamic load and noise source of the rotor blade. The second model building unit is used to build a CSD model for solving the helicopter rotor blade-vortex interference 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 coupled model of 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 helicopter rotor blades using a structural dynamics model, performing rotor-vortex interference flow field simulation to obtain air pressure fluctuation data in the rotor blade region. This includes: creating a basic 3D model of the rotor blade based on its fundamental geometric parameters; discretizing the computational domain of the rotor blade flow field using an overlapping mesh method; solving the turbulent structure of the rotor blade using a large eddy simulation model and a RANS model; assigning the fuselage and rotor blade meshes to the solid region, and the background and overlapping meshes to the fluid region; setting initial conditions, defining calculation parameters, rotor blade motion parameters, and rotor blade material properties; setting inlet and outlet boundary conditions, and setting boundary conditions for all walls; setting solver parameters and executing the simulation process; stopping the calculation after a set convergence time; and outputting helicopter rotor blade tip vortex field information, aerodynamic data, and pressure load data corresponding to the mesh points on the rotor blade surface. The air pressure fluctuation data includes rotor blade tip vortex field information, aerodynamic data, and pressure load data corresponding to the mesh points on the rotor blade surface. The fourth model building unit is used to build the FW-H model for solving the helicopter rotor blade-vortex interference noise, perform BVI noise calculation on the rotor blades, and use air pressure pulsation data to calculate the sound pressure fluctuation data at the microphone receiver location. The fifth model building unit is used to build an HHC numerical calculation model to suppress helicopter rotor blade-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. The evaluation unit is used to evaluate the HHC numerical calculation model's suppression effect on BVI noise.

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