Porous medium flow-induced noise control method based on sensitivity distribution

Abstract

The invention discloses a porous medium flow-induced noise control method based on sensitive distribution, which relates to the field of flow control, and comprises the following steps: selecting an aircraft landing gear cabin configuration, building a corresponding aircraft landing gear cabin model, and setting a computational domain of numerical simulation; substituting the aircraft landing gear cabin model and the boundary conditions into a numerical solution model to solve a flow field to obtain a flow solution Q; establishing an adjoint equation set, and substituting the flow solution Q into the adjoint equation set to obtain an adjoint solution Q; based on the adjoint solution Q, performing statistics on sensitivity distribution on the wall surface where the porous medium is arranged in the aircraft landing gear cabin model to obtain a sensitivity distribution result; setting wall surface boundary conditions for simulating a porous medium based on the sensitivity distribution result; substituting the wall surface boundary conditions into the numerical solution model for numerical simulation calculation to obtain flow based on porous medium control; according to the method, the flow control effect is improved by optimizing the spatial distribution of the porous medium.

Description

Technical Field

[0001] The 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, passengers' requirements for aviation comfort have been further improved, and aviation noise has become the key to aircraft airworthiness certification. Based on the existing aerodynamic noise standard level, the existing technology has further improved the noise level of flight airworthiness, requiring the noise level of new passenger aircraft in each stage of airworthiness application to be reduced by 10EPNdB (Effective perceived noise) compared with the previous stage, which further increases the difficulty of airworthiness certification. At present, the main source of aircraft noise is the noise caused by the landing gear compartment. The noise generated during the approach phase accounts for about 30% of the total aircraft noise, and it is urgent to control the flow and flow-induced noise. At present, there are two main control methods for the control of the landing gear compartment flow: active and passive. Traditional passive control improves the flow and suppresses noise by changing the configuration or adding flow controllers to lift the shear layer, which will seriously damage the aerodynamic performance. Recently, scholars have proposed a passive control method based on porous media, which can maintain the aerodynamic characteristics of the flow configuration and has a good flow control effect. However, the uniformly distributed porosity control effect is limited and may reduce the strength. On the one hand, when the porosity increases to a certain extent, the control effect will be saturated or even rapidly reduced. This is mainly because the flow on the surface of the porous medium is not uniform, and when the uniformly distributed porous medium is used for control, it will cause local flow blockage. On the other hand, after the porous medium is arranged on the entire wall, the strength of the equipment surface is reduced and the service life is seriously shortened. Summary of the invention

[0003] The purpose of the present invention is to propose a porous medium 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 of porous medium porosity distribution, the method comprising: 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: 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.

[0005] One or more technical solutions provided by the present invention have at least the following technical effects or advantages: The present invention adopts sensitivity analysis to examine the sensitivity distribution of flow, and determines the spatial distribution of porous media according to the principle of adopting high-density porosity distribution in highly sensitive areas, adopting low-density porosity distribution in less sensitive areas, or not arranging porous media in less sensitive areas, so as to further improve the control effect of porous media on flow and noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] 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 on the embodiments of the present invention; Figure 1 It is a flow chart of a porous media flow-induced noise control method based on sensitivity distribution; Figure 2 A schematic diagram of the porous wall flow control technology route based on sensitivity analysis; Figure 3 It is a schematic diagram of the distribution of the computational domain; Figure 4 Schematic diagram of sensitivity distribution and porosity distribution on the wall of porous media; Figure 5 This is a schematic diagram of the full-field sound pressure level distribution of the solid wall cavity bottom of the example Beta0; Figure 6 Schematic diagram of the full-field sound pressure level distribution of porous media with porosity distribution corresponding to the example Beta0.6; Figure 7 Schematic diagram of the full-field sound pressure level distribution of porous media corresponding to the porosity distribution of the example BetaQ; Figure 8 is the cavity bottom sound pressure level ( Figure 3 Distribution diagram (shown in ⑦); Fig. 9 is the sound pressure level in the upper part of the deep cavity ( Figure 3 (as shown in ⑧) distribution diagram; Fig.10 for Figure 5 Middle arc ( Figure 3 Schematic diagram of the sound pressure level distribution at the monitoring points (shown in (9)). DETAILED DESCRIPTION

[0007] In order to more clearly understand the above-mentioned purpose, 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 in the embodiments can be combined with each other without conflict.

[0008] 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 within the scope of this description. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0009] Embodiment 1;

[0010] Please refer to Figure 1 , Figure 1 The figure is a flow chart of a porous medium flow-induced noise control method based on sensitivity distribution. The present invention provides a porous medium flow-induced noise control method based on sensitivity distribution, and 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: 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 applicant has found that the flow control effect is very sensitive to the distribution of porous media, and it is necessary to arrange porous media as needed according to the flow field characteristics and adjust the distribution of the porosity of the porous media. The present invention will first examine the sensitivity distribution of the flow by using sensitivity analysis, and determine the spatial distribution of the porous media according to the principle of using high-density porosity distribution in highly sensitive areas, low-density porosity distribution in less sensitive areas, or not arranging porous media in less sensitive areas, so as to further improve the control effect of porous media on flow and noise.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] The invention is characterized in that sensitivity analysis is introduced into the control scheme of porous media, the porosity of porous media is increased in high-sensitivity areas, the porosity of porous media is reduced in low-sensitivity areas, and porous media is not used in low-sensitivity areas.

[0016] 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.

[0017] 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: Step 1: Select the aircraft landing gear compartment configuration and model it, such as Figure 3 As shown, Figure 3 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 numerical simulation, including boundary conditions and buffer zones. The boundary conditions include: a) Inflow boundary conditions: boundary conditions for the flow entering and leaving the calculation domain in the incoming flow direction. In the subsonic flow state, subsonic inflow and outflow boundary conditions are selected; b) Far-field boundary conditions: far away from the calculation domain of the landing gear compartment, mainly simulating the flow out of the calculation domain at this boundary, and preventing the reflection of sound waves at the boundary; c) Outflow boundary conditions: The boundary conditions of the flow out of the calculation domain in the outflow direction, using the extrapolation method; d) No-slip wall boundary condition: The fuselage plane around the landing gear compartment of the simulator is used. The flow cannot slip on the fuselage plane, so the no-slip wall boundary condition is used. 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 equations of the fluid using a numerical solution based on the finite difference method.

[0018] The solution formula of the numerical solution model is: ; (1.1) Flow parameters Q And three non-stick F , G and H The calculation method is: ; (1.2) Sticky Items F v , G v and H v The calculation method is: ; (1.3) in, N ( Q ) is the Navier-Stokes equation, Q For the flow solution, E is the total energy per unit volume of fluid, t For 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 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.

[0019] Step 3: Establish the adjoint equations and convert the flow solution obtained in step 2 Q Substitute it into the adjoint equation system and solve it to get the adjoint solution Q † The adjoint solution is based on the governing equations of the adjoint method. Q † The calculation method is: ; (1.4) 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; in, T † ,X † , Y † , Z † and D † The calculation methods are: ; (1.5) Where γ is the specific heat ratio of the fluid; ; (1.6) ; (1.7) ; (1.8) ; (1.9) in, , and They are all intermediate quantities, and the calculation formulas are: ; (1.10) in, is the intermediate quantity, , Pr is the Prandtl number of the fluid; ; (1.11) . (1.12) Step 4: The adjoint solution obtained in step 3 Q † , analyze the sensitivity distribution of the flow field. The sensitivity distribution on the wall of the porous medium is statistically arranged, that is, Figure 3 The sensitivity on the wall corresponding to ⑥ is as follows: Figure 4 Indicated by the black dashed line.

[0020] 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: 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 βref .

[0021] The porosity distribution and back pressure are calculated as follows: ; 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 porosity β The spatial distribution and adjoint solution of Q † Consistent, use space Q † The maximum value of Q † max Normalized, we get β ( Q † )like Figure 4 Shown by the solid line.

[0022] The penetration rate of porous wall v porous It can be expressed as: ; in, v porous is the penetration velocity of the porous wall, p w is the pressure on the wall, p b is the back pressure. The porous wall penetration rate v porous Porosity distribution β ( Q † ) and wall pressure difference p b - p w Related.

[0023] 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 abscissa represents the flow direction.

[0024] The embodiment of the present invention proposes a new porous medium wall boundary condition, which combines flow sensitivity analysis with porous medium-based control.

[0025] In order to verify the accuracy of the technical solution, the implementation of the present invention is described below in conjunction with the accompanying drawings. The embodiments described herein are only used for illustration and explanation and are not intended to limit the present invention.

[0026] The research object is a typical M219 aircraft landing gear bay configuration, with a length: width: depth ratio of 5:1:1. When the 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 3 There are three setting schemes for the bottom of the aircraft landing gear shown in Figure ⑥, namely, a non-slip solid wall that is impenetrable by flow, a porous medium with uniform porosity distribution, and a porous medium with porosity distribution obtained based on sensitivity analysis. The specific parameters are shown in Table 1.

[0027] Table 1 Parameters

[0028] 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.

[0029] By comparing with the non-slip and impenetrable solid wall of the aircraft landing gear cabin bottom, the sound pressure level pulsation of the penetrable porous wall cabin bottom is significantly reduced, and the noise level radiated to the far field is also greatly reduced, such as Figures 7 to 10 As shown. 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. Fig.10 Sound pressure level distribution on an arc with center (5,0) and radius r=2.5.

[0030] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other 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.

[0031] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

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: 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.

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: The solution formula of the numerical solution model is: ； in, N ( Q ) is the Navier-Stokes equation, the flow parameter 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, t For 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 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: 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; in, 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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