A method for controlling flow-induced noise in porous media based on sensitivity distribution

Abstract

The present invention discloses a porous medium flow-induced noise control method based on sensitivity distribution, which relates to the field of flow control, including: selecting an aircraft landing gear compartment configuration and building a corresponding aircraft landing gear compartment model, setting a calculation domain for numerical simulation; bringing the aircraft landing gear compartment model and the boundary conditions into a numerical solution model to solve the flow field and obtain a flow solution. Q ; Establish the adjoint equations and solve the flow Q Substitute it into the adjoint equation system and solve it to get the adjoint solution Q † Based on the adjoint solution Q † , statistically analyzing the sensitivity distribution on the wall surface where the porous medium is arranged in the aircraft landing gear compartment model, and obtaining the sensitivity distribution result; based on the sensitivity distribution result, setting the wall boundary condition for simulating the porous medium; substituting the wall boundary condition into the numerical solution model for numerical simulation calculation, and obtaining the flow controlled by the porous medium; this method improves the control effect on the flow by optimizing the spatial distribution of the porous medium.

Description

Technical Field

[0001] The present invention relates to the field of flow control, and in particular to a method for controlling flow-induced noise in porous media based on sensitivity distribution. Background Art

[0002] With the rapid development of the aviation industry, passenger comfort requirements are increasing, and aviation noise has become a key component of aircraft airworthiness certification. Existing technologies, based on existing aerodynamic noise standards, have further raised the noise level required for flight airworthiness. New passenger aircraft applying for airworthiness certification at each stage must achieve a 10 EPNdB (Effective Perceived Noise) reduction compared to previous levels, further increasing the difficulty of airworthiness certification. Currently, the primary source of aircraft noise is noise from the landing gear bay, which contributes approximately 30% of the total aircraft noise during approach. Control of flow and flow-induced noise is urgently needed. Currently, there are two main approaches to controlling landing gear bay flow: active and passive. Traditional passive control methods improve flow and suppress noise by modifying the configuration or adding flow controllers to raise the shear layer, which can severely compromise aerodynamic performance. Recently, researchers have proposed a passive control approach based on porous media that maintains the aerodynamic properties of the flow configuration and offers excellent flow control. However, the uniformly distributed porosity used in these approaches has limited effectiveness and may reduce strength. On the one hand, when the porosity increases to a certain level, the control effect becomes saturated or even rapidly decreases. This is primarily because the flow across the porous media surface is uneven, leading to localized flow blockages when using evenly distributed porous media for control. On the other hand, when porous media is deployed across the entire wall, the surface strength of the equipment decreases, significantly shortening its service life. Summary of the Invention

[0003] The purpose of the present invention is to propose a porous media flow-induced noise control method based on sensitivity distribution based on flow sensitivity and porous media, and to improve the flow control effect by optimizing the spatial distribution of porous media.

[0004] To achieve the above object, the present invention provides a method for controlling flow-induced noise in a porous medium porosity distribution, the method comprising:

[0005] Step 1: Select the aircraft landing gear bay configuration and build the corresponding aircraft landing gear bay model, and set the computational domain and boundary conditions for the numerical simulation;

[0006] Step 2: Bring the aircraft landing gear compartment model and the boundary conditions into the numerical solution model to solve the flow field and obtain the flow solution Q ;

[0007] Step 3: Establish the adjoint equations and solve the flow QSubstitute into the adjoint equation system and solve to obtain the adjoint solution Q † ;

[0008] Step 4: Based on the adjoint solution Q † , statistically analyze the sensitivity distribution on the wall surface of the porous medium in the aircraft landing gear compartment model and obtain the sensitivity distribution results;

[0009] Step 5: Based on the sensitivity distribution results, setting the wall boundary conditions for simulating the porous medium;

[0010] Step 6: Substitute the wall boundary conditions of the porous medium into the numerical solution model to perform numerical simulation calculations to obtain the landing gear bay flow based on porous medium control.

[0011] The one or more technical solutions provided by the present invention have at least the following technical effects or advantages:

[0012] The present invention uses sensitivity analysis to examine the sensitivity distribution of flow. The spatial distribution of porous media is determined based on the principle of adopting a high-density porosity distribution in highly sensitive areas, a low-density porosity distribution in less sensitive areas, or no porous media in less sensitive areas, thereby further improving the control effect of porous media on flow and noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of the present invention, and do not constitute a limitation of the embodiments of the present invention;

[0014] Figure 1 Schematic diagram of a flow chart of a porous media flow-induced noise control method based on sensitivity distribution;

[0015] Figure 2 Schematic diagram of the porous wall flow control technology route based on sensitivity analysis;

[0016] Figure 3 Schematic diagram of the distribution of the computational domain;

[0017] Figure 4 Schematic diagram of sensitivity distribution and porosity distribution on the wall of porous media;

[0018] Figure 5 Schematic diagram of the full-field sound pressure level distribution at the bottom of the solid wall cavity of example Beta0;

[0019] Figure 6 Schematic diagram of the full-field sound pressure level distribution of porous media with porosity distribution corresponding to the example Beta0.6;

[0020] Figure 7Schematic diagram of the full-field sound pressure level distribution of porous media with porosity distribution corresponding to the example BetaQ;

[0021] Figure 8 is the cavity bottom sound pressure level ( Figure 3 (7 in the middle) Distribution diagram;

[0022] Figure 9 is the sound pressure level in the upper part of the deep cavity ( Figure 3 (shown in ⑧) Distribution diagram;

[0023] Figure 10 for Figure 5 Center arc ( Figure 3 Schematic diagram of the sound pressure level distribution at the monitoring points (shown in Figure 9). DETAILED DESCRIPTION

[0024] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features therein can be combined with each other without conflict.

[0025] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0026] Embodiment 1;

[0027] Please refer to Figure 1 , Figure 1 Schematic diagram of a flow chart of a porous media flow-induced noise control method based on sensitivity distribution. The present invention provides a porous media flow-induced noise control method based on sensitivity distribution, the method comprising:

[0028] Step 1: Select the aircraft landing gear bay configuration and build the corresponding aircraft landing gear bay model, and set the computational domain and boundary conditions for the numerical simulation;

[0029] Step 2: Bring the aircraft landing gear compartment model and the boundary conditions into the numerical solution model to solve the flow field and obtain the flow solution Q ;

[0030] Step 3: Establish the adjoint equations and solve the flow Q Substitute into the adjoint equation system and solve to obtain the adjoint solution Q † ;

[0031] Step 4: Based on the adjoint solution Q †, statistically analyze the sensitivity distribution on the wall surface of the porous medium in the aircraft landing gear compartment model and obtain the sensitivity distribution results;

[0032] Step 5: Based on the sensitivity distribution results, setting the wall boundary conditions for simulating the porous medium;

[0033] Step 6: Substitute the wall boundary conditions of the porous medium into the numerical solution model to perform numerical simulation calculations to obtain the landing gear bay flow based on porous medium control.

[0034] The applicant's research has found that the flow control effect is very sensitive to the distribution of porous media. It is necessary to arrange the porous media as needed according to the flow field characteristics and adjust the porosity distribution of the porous media. This invention uses sensitivity analysis to first examine the flow sensitivity distribution. The spatial distribution of the porous media is determined based on the principle of using a high-density porosity distribution in highly sensitive areas, a low-density porosity distribution in less sensitive areas, or no porous media in less sensitive areas. This further improves the porous media's control effect on flow and noise.

[0035] The technical solution of the present invention includes: solving the adjoint equation group to obtain the adjoint solution, the adjoint solution is used to characterize the flow sensitivity information, the high sensitivity area indicates that the flow has the strongest response to the control, and the low sensitivity area indicates that the flow has a weaker response to the control.

[0036] Porous media can allow flow in and out, and will produce obvious blowing and suction phenomena under fixed back pressure. Arranging porous media at the bottom of the aircraft landing gear compartment can improve the flow in the compartment.

[0037] The control effect of porous media with uniform porosity distribution is limited. The flow on the surface of porous media is not uniformly distributed. Uniformly distributed porous media will cause local flow blockage and affect the overall control effect.

[0038] The present invention is characterized in that sensitivity analysis is introduced into the control scheme of porous media, the porosity of porous media is increased in highly sensitive areas, the porosity of porous media is reduced in less sensitive areas, and porous media is not used in less sensitive areas.

[0039] The present invention proposes a mathematical relationship between an adjoint solution characterizing flow sensitivity information and the porosity distribution of porous media, which can be extended to engineering applications.

[0040] The technical circuit diagram of the present invention is as follows Figure 2 As shown, the specific implementation steps of the technical route in the technical solution are:

[0041] Step 1: Select the aircraft landing gear compartment configuration and model it, such as Figure 3 As shown, Figure 3In the figure, ① and ③ are the inlet and outlet boundaries, ② is the far-field boundary, ④ and ⑤ are the aircraft fuselage walls, and ⑥ is the porous medium. Set the computational domain for the numerical simulation, including boundary conditions and buffer zones. The boundary conditions include:

[0042] a) Inflow boundary conditions: The boundary conditions for the flow entering and leaving the computational domain in the incoming direction. For subsonic flow conditions, subsonic inlet and outlet boundary conditions are selected.

[0043] b) Far-field boundary condition: This condition is far away from the computational domain of the landing gear bay. The main simulated flow is flowing out of the computational domain at this boundary, and the reflection of sound waves at the boundary must be prevented.

[0044] c) Outflow boundary conditions: The boundary conditions for the flow out of the calculation domain in the outflow direction, using the extrapolation method;

[0045] d) No-slip wall boundary condition: The flow cannot slip on the fuselage plane around the landing gear compartment of the simulator, so the no-slip wall boundary condition is used;

[0046] Step 2: Substitute the aircraft landing gear compartment model and boundary conditions in step 1 into the numerical solution model established by the control equation of formula 1.1 to solve the flow field and obtain the flow solution Q The model follows the governing fluid equations using a numerical solution based on the finite difference method.

[0047] The solution formula of the numerical solution model is:

[0048] ; (1.1)

[0049] Flow parameters Q And three non-stick F 、 G and H The calculation method is:

[0050] ; (1.2)

[0051] Sticky Items F v 、 G v and H v The calculation method is:

[0052] ; (1.3)

[0053] in, N ( Q ) is the Navier-Stokes equation, Q is the flow solution, E is the total energy per unit volume of fluid, tFor time, x, y and z are the stream direction, normal direction and span direction respectively, ∂ is the symbol for partial differential calculation, ρ is the density, p For pressure, u 、 v and w The fluid particles are x 、 y and z The velocity component in the direction, τ xx 、 τ yy and τ zz Acting on x, y and z Normal forces per unit area in three directions, τ xy For the x Direction acting on y The shear stress per unit area in the direction τ xz For the x Direction acting on z The shear stress per unit area in the direction, τ yx For the y Direction acting on x The shear stress per unit area in the direction, τ yz For the y Direction acting on z The shear stress per unit area in the direction, τ zx For the z Direction acting on x The shear stress per unit area in the direction, τ zy For the z Direction acting on y The shear stress per unit area in the direction, q x 、 q y and q z They are x 、 y and z Energy exchange caused by directional heat flux and material diffusion.

[0054] Step 3: Establish the adjoint equations and transform the flow solution obtained in step 2 into Q Substitute into the adjoint equation system and solve to obtain the adjoint solution Q† The governing equations based on the adjoint method, the adjoint solution Q † The calculation method is:

[0055] ; (1.4)

[0056] in, N † ( Q † ) is the adjoint state equation, T † 、 X † 、 Y † 、 Z † and D † are coefficient matrices, Ma and Re represent the far-field Mach number and Reynolds number, respectively;

[0057] in, T † 、 X † 、 Y † 、 Z † and D † The calculation methods are:

[0058] ; (1.5)

[0059] Where γ is the specific heat ratio of the fluid;

[0060] ; (1.6)

[0061] ; (1.7)

[0062] ; (1.8)

[0063] ; (1.9)

[0064] in, 、 and They are all intermediate quantities, and the calculation formulas are:

[0065] ; (1.10)

[0066] in, is the intermediate amount, , Pr is the Prandtl number of the fluid;

[0067] ; (1.11)

[0068] . (1.12)

[0069] Step 4: The adjoint solution obtained in step 3 Q † , analyze the sensitivity distribution of the flow field. Statistically arrange the sensitivity distribution on the wall of the porous medium, that is, Figure 3 The sensitivity on the wall corresponding to ⑥ is as follows Figure 4 Indicated by the black dotted line.

[0070] Step 5: Based on the sensitivity distribution obtained in step 4, set the wall boundary conditions that can simulate the porous material. The porous wall boundary conditions determine the properties of the porous material through two parameters, namely porosity and β and backpressure p b The present invention combines porosity and the concomitant solution that characterizes flow sensitivity. Q † Correlation, through the porosity parameter of a given porous medium β ref , using the adjoint solution Q † The obtained porosity distribution β ( Q † ) is set as the closest porosity parameter β ref .

[0071] The porosity distribution and back pressure are calculated as follows:

[0072] ;

[0073] in, β is the porosity, β ref is the porosity parameter of a given porous medium, β ( Q † ) is the porosity distribution, Q † max For the space Q † The maximum value of porosity β The spatial distribution and adjoint solution of Q † Consistent, use space Q † The maximum value Q† max Normalized, we get β ( Q † )like Figure 4 Shown as solid line.

[0074] Permeation velocity of porous wall v porous It can be expressed as:

[0075] ;

[0076] in, v porous is the penetration velocity of the porous wall, p w represents the pressure on the wall, p b is the back pressure. The porous wall penetration rate v porous and porosity distribution β ( Q † ) and wall pressure difference p b - p w Related.

[0077] Step 6: Substitute the porous wall boundary conditions obtained in step 5 into the control equation of step 2 for numerical simulation calculation to obtain the flow based on porous media control. Figure 4 Schematic diagram of sensitivity distribution and porosity distribution on the wall of porous media. Figure 4 The horizontal axis represents the flow direction.

[0078] The embodiment of the present invention proposes a new porous medium wall boundary condition, which combines flow sensitivity analysis and porous medium-based control.

[0079] In order to verify the accuracy of the technical solution, the implementation of the present invention is described below with reference to the accompanying drawings. The embodiments described herein are only used for illustration and explanation and are not intended to limit the present invention.

[0080] The research object is a typical M219 aircraft landing gear bay configuration, with a length: width: depth ratio of 5:1:1. When Mach number Ma=0.5, Re=0.5*10 5 When the flow passes through this configuration, a typical self-sustaining oscillation phenomenon will occur. In order to prevent the radiation noise from being emitted in the far field and affecting the flow field, a non-reflecting boundary condition is imposed at the far field boundary. The calculation model is as follows: Figure 3 shown. Figure 3There are three design options for the aircraft landing gear compartment shown in Figure 6: a solid, non-slip wall that is impenetrable to flow, a porous medium with uniform porosity distribution, and a porous medium with a porosity distribution obtained based on sensitivity analysis. The specific parameters are shown in Table 1.

[0081] Table 1 Parameters

[0082]

[0083] Among them, Beta0, Beta0.6 and BetaQ are the names of the examples. The schematic diagram of the full-field sound pressure level distribution corresponding to the above examples is as follows Figures 5 to 7 As shown, Figures 5 to 7 The abscissa represents the streamwise position, and the ordinate represents the normal position.

[0084] By comparing with the non-slip and impenetrable solid wall of the aircraft landing gear bottom, the sound pressure level pulsation of the penetrable porous wall bottom is significantly reduced, and the noise level radiated to the far field is also greatly reduced. Figures 7 to 10 As shown in the figure. The porous media-based flow control effectively suppressed the noise level of the landing gear compartment and improved the flow inside the compartment, successfully reducing the noise level of the landing gear. Figure 8-Figure 9 The horizontal axis represents the flow direction, and the vertical axis represents the noise level. Figure 10 The sound pressure level distribution on the arc with center (5,0) and radius r=2.5.

[0085] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0086] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for controlling flow-induced noise in porous media based on sensitivity distribution, characterized in that: The method comprises: Step 1: Select the aircraft landing gear bay configuration and build the corresponding aircraft landing gear bay model, and set the calculation domain and boundary conditions of the numerical simulation; Step 2: Bring the aircraft landing gear compartment model and the boundary conditions into the numerical solution model to solve the flow field and obtain the flow solution Q ; Step 3: Establish the adjoint equations and solve the flow Q Substitute it into the adjoint equation system and solve it to get the adjoint solution Q † ; Step 4: Based on the adjoint solution Q † , statistically analyze the sensitivity distribution on the wall surface where porous media is arranged in the aircraft landing gear compartment model, and obtain the sensitivity distribution results; Step 5: Based on the sensitivity distribution result, setting the wall boundary conditions for simulating the porous medium; Step 6: Substituting the wall boundary conditions of the porous medium into the numerical solution model to perform numerical simulation calculations to obtain the landing gear compartment flow based on porous medium control; The solution formula of the numerical solution model is: ； in, N ( Q ) is the Navier-Stokes equation, Q is the flow parameter, F , G and H For non-sticky, F v , G v and H v is the sticky term, t For time, x, y and z are the stream direction, normal direction and span direction respectively, ∂ is the symbol for partial differential calculation; The adjoint solution Q † The calculation method is: ； in, N † ( Q † ) is the adjoint state equation, T † , X † , Y † , Z † and D † are coefficient matrices, Ma and Re represent the far-field Mach number and Reynolds number, respectively.

2. The porous media flow-induced noise control method based on sensitivity distribution according to claim 1 is characterized in that: The boundary conditions include: Inflow boundary conditions: boundary conditions for the flow entering and leaving the computational domain in the inflow direction; Far-field boundary conditions: The area in the computational domain far away from the aircraft landing gear compartment, used to simulate the flow out of the computational domain at this boundary and to prevent the reflection of sound waves at the boundary; Outflow boundary conditions: boundary conditions for the flow out of the computational domain in the outflow direction; No-slip wall boundary condition: used to simulate the fuselage plane around the aircraft landing gear compartment, using no-slip wall boundary conditions.

3. The porous media flow-induced noise control method based on sensitivity distribution according to claim 1, characterized in that: Flow parameters Q And three non-stick F , G and H The calculation method is: ； Sticky Items F v , G v and H v The calculation method is: ； in, E is the total energy per unit volume of fluid, ρ is the density, p For pressure, u , v and w The fluid particles are x , y and z The velocity component in the direction, τ xx , τ yy and τ zz They act on x, y and z Normal forces per unit area in three directions, τ xy For along x Direction acting on y The shear stress per unit area in the direction, τ xz For along x Direction acting on z The shear stress per unit area in the direction, τ yx For along y Direction acting on x The shear stress per unit area in the direction, τ yz For along y Direction acting on z The shear stress per unit area in the direction, τ zx For along z Direction acting on x The shear stress per unit area in the direction, τ zy For along z Direction acting on y The shear stress per unit area in the direction, q x , q y and q z They are x , y and z Energy exchange caused by directional heat flux and material diffusion.

4. The porous media flow-induced noise control method based on sensitivity distribution according to claim 3 is characterized in that: T † , X † , Y † , Z † and D † The calculation methods are: ； Where, γ is the specific heat ratio of the fluid; ； ； ； ； in, , and They are all intermediate quantities, and the calculation methods are: ； in, is the intermediate quantity, , Pr is the Prandtl number of the fluid; ； 。 5. The porous media flow-induced noise control method based on sensitivity distribution according to claim 1, characterized in that: The wall boundary conditions include porosity distribution and back pressure.

6. The porous media flow-induced noise control method based on sensitivity distribution according to claim 5, characterized in that: The porosity distribution and back pressure are calculated as: ； in, β is the porosity, β ref is the porosity parameter of a given porous medium, β ( Q † ) is the porosity distribution, Q † max For space Q † The maximum value of ； in, v porous is the penetration velocity of the porous wall, p w is the pressure on the wall, p b For back pressure.

7. The porous media flow-induced noise control method based on sensitivity distribution according to claim 1, characterized in that: The corresponding area of ​​the cavity bottom of the aircraft landing gear compartment is a porous medium.

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