Oscillation jet device parameter optimization method based on flow control

Abstract

The invention discloses an oscillating jet device parameter optimization method based on flow control, which belongs to the field of aircraft flow control, and comprises the following steps: establishing an oscillating jet device model, and parameterizing an oscillating jet device; the oscillating jet device is assembled on a wing for flow control; grid division is carried out on the wing and the oscillating jet device; carrying out numerical simulation calculation according to the research working condition; parameterization optimization is carried out on the oscillation jet device, the lift coefficient is used as a research target, and the oscillation jet controller with the optimal flow control is obtained. According to the mechanism that the geometrical parameters of the oscillation jet device can influence the oscillation characteristic of the oscillation jet device, the separation vortex size of the wing is effectively reduced by changing the geometrical parameters of the oscillation jet device according to the research working condition in flow control, and the lift augmentation performance of the wing is further improved.

Description

Technical Field

[0001] The invention belongs to the field of aircraft flow control, and in particular relates to an oscillating ejector parameter optimization method based on flow control. Background Art

[0002] The most straightforward way to reduce aircraft drag is to reduce the number of components in the aircraft while maintaining aerodynamic performance. This can be achieved through high-lift systems that allow for shorter takeoff and landing maneuvers. But high-lift systems are susceptible to boundary layer separation at high angles of attack and large deflections. The boundary layer separates when the fluid within the boundary layer lacks the energy to offset the kinetic energy losses caused by adverse pressure gradients and viscous dissipation in a given application. This separation results in significant energy losses, resulting in increased drag, reduced lift, or reduced total pressure recovery, which reduces system performance. To suppress boundary layer separation, flow control methods are often used to add momentum and vorticity to the boundary layer. Such flow control methods can be either active or passive.

[0003] At present, many flow control technologies such as vortex generators and plasma have been developed and applied in various fields. Typical applications include drag reduction, lift increase and noise reduction. In the development of these technologies, the oscillating ejector has been widely studied due to its simple structure and the ability to convert a stable jet into an oscillating jet without the need for external flow. However, in the study of the characteristics of the oscillating ejector, it was found that the oscillation characteristics of the oscillating ejector are related to the geometric dimensions of the oscillating ejector in addition to the momentum coefficient. Therefore, it is very important to select the appropriate size of the oscillating ejector according to the working environment and the wing in flow control, which can effectively improve work efficiency and delay stall. However, the current research basically only studies the flow control characteristics of the oscillating ejector, and does not study the influence of the size change of the oscillating ejector on the flow control, which leads to poor control effect. Summary of the invention

[0004] The present invention provides a method for optimizing parameters of an oscillating ejector based on flow control, which can overcome the defects in the prior art that the oscillating ejector cannot provide a reasonable size according to actual working conditions during the flow control process and cannot achieve the best control effect.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions:

[0006] A method for optimizing parameters of an oscillating ejector based on flow control comprises a wing and an oscillating ejector arranged near a separation point of the wing, wherein the oscillating ejector is an optimization object of the present invention, and the size of the rear oscillating ejector can be changed accordingly by parameter design of the oscillating ejector, and the size of the oscillating ejector is taken as a research object, improving the lift coefficient is taken as a research target, and optimization methods such as genetic algorithms are used as research methods for optimization; the method comprises the following steps:

[0007] 1) Establish an oscillating ejector model and parameterize the oscillating ejector;

[0008] 2) Attach an oscillating ejector to the wing for flow control;

[0009] 3) Mesh the wing and oscillating ejector;

[0010] 4) Based on the wing grid, numerical simulation is performed on the wing flight conditions;

[0011] 5) Based on numerical simulation, the parameters of the oscillating ejector are optimized with the lift coefficient as the target.

[0012] The oscillating ejector with the best lift coefficient for the wing is obtained.

[0013] In the above steps, in the process of parameterizing the oscillating ejector in the oscillating ejector model in step 1), modeling software such as Solidworks, Catia and Caeses can be selected for modeling. The oscillating ejector parameters that can be optimized are the length and width of the oscillating ejector. In the parameterization process, the length and width of the oscillating ejector that can be optimized are defined as parameters A and B, respectively, and the dimensions associated or related thereto are defined as f(A)=A+X, f(B)=B+Y, wherein the units of X and Y are mm, which can be positive or negative.

[0014] In step 2), an oscillating ejector is applied to the wing, and its installation position is near the wing separation point. The angle between the oscillating ejector and the external flow is 10°, and the flow direction of the oscillating ejector outlet is the same as the direction of the external flow;

[0015] In step 3), during the meshing of the wing and the oscillating ejector, according to Y + =1 is the division standard to define the number of first-layer grids of the boundary layer of the wing and the oscillating ejector. The number of boundary layers is selected to be 10 to 20 layers, and the growth ratio of each boundary layer grid is 1.05 to 1.2. ICEM CFD and Fluent meshing and other grid division software are selected for grid division, and automatic grid division scripts and grid division software call scripts are established;

[0016] In step 4), in the numerical simulation calculation according to the actual flight condition of the wing, the external flow velocity is set to 0.2-0.3 Ma according to the flight speed of the take-off and landing configuration, and the flight condition parameters and the numerical simulation method script are established in FLUENT, and a FLUENT software script is established;

[0017] In step 5), during the process of optimizing the design method for the oscillating ejector parameters, the optimization design method is selected as a genetic algorithm or simulated annealing optimization method through multidisciplinary optimization software such as ISIGHT or CASES, with the goal of improving the lift coefficient. The lift coefficient is used as a measurement standard, and the lift coefficient C L for:

[0018]

[0019] Where L is the lift of the wing; ρ is the atmospheric density, V ∞ is the velocity of the external flow on the wing, l is the wing area;

[0020] The optimizable oscillating ejector length dimension A is 30 to 40 mm, and the oscillating ejector width dimension B is 33 to 80 mm. During the optimization process, a new oscillating jet controller will be randomly generated according to the variation range of the oscillating ejector length A and the oscillating ejector width B, and then applied to the flow control of the wing to obtain the lift coefficient of the wing under control, and compared with the lift coefficient of the wing under the control of the basic oscillating jet controller. If the optimization effect is better, the basic oscillating ejector will be replaced, and based on this, the optimization will continue until the optimization standard is reached.

[0021] The optimization method is selected as a simulated annealing algorithm to optimize the parameters of the oscillating jet controller, specifically including:

[0022] The original size of the oscillating jet controller is used as the initialization parameter (A0, B0), and the lift coefficient increment is set to be above 0.1 as the termination condition;

[0023] A new solution (A1, B1) is randomly generated according to the variation range of the optimization parameters A and B of the oscillating jet controller; then the lift coefficient under the parameter environment is calculated, and then the acceptance probability α=min1,e is calculated. -ΔE / Tn , where ΔE=f(A1,B1)-f(A0,B0), T n Indicates the current temperature;

[0024] Then update the solution with acceptance probability α. If accepted, the state becomes (A1, B1), otherwise the state remains (A0, B0);

[0025] The temperature is then reduced according to the specified annealing rate and T is checked. n Whether the termination conditions are met;

[0026] Repeat the above steps until the optimal solution is found or the maximum number of iterations is reached;

[0027] After the group meets the evaluation conditions, the group is output to obtain the optimization parameter library for the current time;

[0028] Based on the lift coefficient, the oscillating ejector with the best flow control effect is selected from the optimization parameter library.

[0029] Beneficial effects: The present invention provides a method for optimizing parameters of an oscillating ejector based on flow control. Compared with the prior art, the present invention has the following advantages:

[0030] (1) The oscillating ejector of the present invention can act on the boundary layer of the wing by actively flowing the swept jet, thereby providing additional momentum for the boundary layer of the wing, thereby bringing the shear layer close to the wing surface, reducing the separation vortex on the wing surface, and suppressing flow separation;

[0031] (2) The oscillating ejector optimization method of the present invention can optimize the collective parameters of the oscillating ejector according to the flight conditions and shape of the wing, so that the oscillation characteristics of the oscillating ejector can be optimized accordingly according to the flight conditions. Under the same momentum coefficient, the separation vortex of the wing can be effectively reduced and the lift coefficient can be effectively improved, thereby effectively improving the lift efficiency of the oscillating ejector and further improving the lift performance of the wing. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the principle of the oscillating ejector model.

[0033] Figure 2 Flow chart of the method for optimizing parameters of an oscillating ejector based on flow control provided as an example of the present invention.

[0034] Figure 3 Schematic diagram of the optimized geometric parameters of the oscillating ejector provided in the example of the present invention.

[0035] Figure 4 A schematic diagram of the basic flow of the simulated annealing algorithm provided for the example of the present invention.

[0036] Figure 5 The basic oscillating ejector model.

[0037] Figure 6 This is to optimize the oscillating ejector model in the embodiment of the present invention.

[0038] Figure 7 In order to optimize the lift coefficient of the oscillating ejector and the basic oscillating ejector at the same momentum coefficient, the change of the lift coefficient with the angle of attack is studied. DETAILED DESCRIPTION

[0039] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0040] like Figure 1The figure shows the working principle of the oscillating ejector. When the fluid passes through the oscillating ejector, the jet adheres to one side of the mixing chamber due to the Coanda effect. The pressure in the feedback channel increases, pushing the jet to the opposite side, generating an oscillating jet at the outlet.

[0041] like Figure 2 As shown, the oscillating ejector parameter optimization method based on flow control includes the following steps:

[0042] 1) Select modeling software such as Solidworks, Catia and Caeses to establish an oscillating ejector model, parameterize the oscillating ejector, and the oscillating ejector parameters that can be optimized are the length and width of the oscillating ejector;

[0043] 2) Assemble the oscillating ejector on the wing for flow control. The installation position is near the wing separation point. The angle between the oscillating ejector and the external flow is 10°.

[0044] 3) Select meshing software such as ICEM CFD and Fluent meshing to mesh the wing and oscillating ejector, and establish an automatic meshing script and a meshing software calling script;

[0045] 4) Based on the wing grid, in the numerical simulation calculation according to the actual flight conditions of the wing, the external flow velocity is set to 0.2-0.3Ma according to the flight speed of the take-off and landing configuration, and the flight condition parameters and numerical simulation method script are established in FLUENT, and a FLUENT software script is established;

[0046] 5) Based on numerical simulation, with the lift coefficient as the target, the optimization methods such as genetic algorithm and simulated annealing are selected to optimize the parameters of the oscillating ejector, and the oscillating ejector with the best lift coefficient of the wing is obtained. The research goal is to improve the lift coefficient. The lift coefficient is used as a measurement standard. The lift coefficient C L for:

[0047]

[0048] Where L is the lift of the wing; ρ is the atmospheric density, V ∞ is the velocity of the external flow on the wing, and l is the wing area.

[0049] The optimizable oscillating ejector parameters are as follows: Figure 3 As shown, the length dimension A of the oscillating ejector is 30 to 40 mm, and the width dimension B of the oscillating ejector is 33 to 80 mm.

[0050] When the optimization method is selected as the simulated annealing algorithm to optimize the parameters of the oscillating jet controller, such as Figure 4 Specifically include:

[0051] The number of evaluations was selected as 50, the number of iterations as 10, and the number of temperatures as 3. The lift coefficient of the wing under each oscillating ejector control was calculated;

[0052] Repeat the above steps until the optimal solution is found or the maximum number of iterations is reached;

[0053] After the group meets the evaluation conditions, the group is output to obtain the optimization parameter library for the current time;

[0054] Based on the lift coefficient, the oscillating ejector with the best flow control effect is selected from the optimization parameter library.

[0055] The working conditions of civil aircraft are complex during take-off and landing, and the aerodynamic characteristics are prone to deterioration, which seriously endangers flight safety. The oscillating characteristics of the oscillating ejector can provide additional momentum to the wings of civil aircraft, effectively reduce the size of the separation vortex of the wings in the take-off and landing configuration, and improve the aerodynamic characteristics of the wings in the take-off and landing configuration. According to this mechanism, by optimizing the parameters of the oscillating ejector and optimizing the oscillating characteristics of the oscillating ejector, the size of the separation vortex and wingtip vortex of the wing is further reduced under the same momentum coefficient, and the pressure coefficient of the wing surface is increased, thereby further increasing the lift coefficient of the wing, and effectively improving the lift-increasing efficiency of the oscillating ejector.

[0056] Example 1

[0057] ICEM CFD and Fluent under ANSYS platform are used to simulate and optimize an oscillating ejector. Its basic model is as follows Figure 5 As shown, the wing equipped with the oscillating ejector is in a take-off and landing configuration, and its operating condition parameters are: the external flow velocity is 30m / s, the direction is horizontal to the right, and the wing attack angle is 0° and 6°.

[0058] Combination Figure 5 , select the basic oscillating ejector with length A and width B, perform parameter optimization through simulated annealing algorithm, select 50 evaluation times, 10 iterations, and 3 temperatures to calculate the lift coefficient of the wing under the control of each oscillating ejector; in the whole optimization process, the original size of the oscillating ejector controller is used as the initialization parameter (A0, B0), and the lift coefficient increment is set to be greater than 0.1 as the termination condition; according to the variation range of the optimization parameters A and B of the oscillating ejector controller, a new solution (A1, B1) is randomly generated; then the lift coefficient under the parameter environment is obtained by calculation, and then the acceptance probability α=min1,e is calculated. -ΔE / Tn , where ΔE=f(A1,B1)-f(A0,B0), T nrepresents the current temperature; then update the solution with acceptance probability α, if accepted, the state becomes (A1, B1), otherwise the state remains (A0, B0); then reduce the temperature according to the specified annealing rate and check T n Whether the termination condition is met; repeat the optimization steps until the termination condition is met, and the results are shown in Table 1.

[0059] Table 1 Optimized values ​​of length A and width B of oscillating ejector

[0060]

[0061] Figure 7 The variation of lift coefficient of the wing with angle of attack of the basic oscillating ejector and the optimized oscillating ejector under the same wing, the same momentum coefficient and the same flight condition is studied. It can be found that under the same momentum coefficient, compared with the basic oscillating ejector, the optimized oscillating ejector can increase the lift coefficient of the wing by 0.13 relatively. This proves the feasibility of applying the oscillating ejector to flow control and the feasibility of applying the oscillating ejector parameter optimization method to flow control, and verifies the reliability and practicality of the method of the present invention.

[0062] The above are only preferred embodiments of the present invention, which cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical ideas proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for optimizing parameters of an oscillating ejector based on flow control, characterized in that: The following steps are involved: 1) Establish an oscillating ejector model and parameterize the oscillating ejector; 2) Assembling an oscillating ejector near the wing separation point for flow control; 3) Mesh the wing and oscillating ejector; 4) Based on the wing grid, numerical simulation is performed on the wing flight conditions; 5) Based on numerical simulation and taking the lift coefficient as the target, the parameters of the oscillating ejector are optimized and designed to obtain the oscillating ejector with the best lift coefficient for improving the wing.

2. The method for optimizing parameters of an oscillating ejector based on flow control according to claim 1, characterized in that: The parameters of the oscillating ejector that can be optimized are the length and width of the oscillating ejector.

3. The method for optimizing parameters of an oscillating ejector based on flow control according to claim 1 or 2, characterized in that: During the parameterization process, the length and width of the oscillating ejector parameters that can be optimized are defined as parameters A and B respectively, and the dimensions associated or related thereto are defined as f(A)=A+X, f(B)=B+Y, where X and Y are in mm and can be positive or negative.

4. The method for optimizing parameters of an oscillating ejector based on flow control according to claim 1, characterized in that: The included angle between the oscillating ejector and the external flow is 10°, and the flow direction of the outlet of the oscillating ejector is the same as the direction of the external flow.

5. The method for optimizing parameters of an oscillating ejector based on flow control according to claim 1, characterized in that: In the process of meshing the wing and the oscillating jet, the Y + =1 is the division standard to define the number of grids in the first layer of the boundary layer of the wing and the oscillating ejector. The number of boundary layers is selected to be 10 to 20 layers, and the growth ratio of each boundary layer grid is 1.05 to 1.

2.

6. The method for optimizing parameters of an oscillating ejector based on flow control according to claim 1 or 5, characterized in that: Select ICEM CFD or Fluent meshing software for meshing, and create an automatic meshing script and a meshing software calling script.

7. The method for optimizing parameters of an oscillating ejector based on flow control according to claim 1, characterized in that: The wing flight condition is an incoming flow velocity of 0.2 to 0.3 Ma.

8. The method for optimizing parameters of an oscillating ejector based on flow control according to claim 1, characterized in that: Genetic algorithm or simulated annealing optimization method is selected for optimizing the design of oscillating ejector parameters.

9. The method for optimizing parameters of an oscillating ejector based on flow control according to claim 1, characterized in that: The lift coefficient C L for: Where L is the lift of the wing; ρ is the atmospheric density, V ∞ is the velocity of the external flow on the wing, and l is the wing area.

10. The method for optimizing parameters of an oscillating ejector based on flow control according to claim 8, characterized in that: The simulated annealing optimization method optimizes the parameters of the oscillating jet controller specifically including: The original size of the oscillating jet controller is used as the initialization parameter (A0, B0), and the lift coefficient increment is set to be above 0.1 as the termination condition; A new solution (A1, B1) is randomly generated according to the variation range of the optimization parameters A and B of the oscillating jet controller; then the lift coefficient under the parameter environment is calculated, and then the acceptance probability α=min1,e is calculated. -ΔE / Tn , where ΔE=f(A1,B1)-f(A0,B0), T n Indicates the current temperature; Then update the solution with acceptance probability α. If accepted, the state becomes (A1, B1), otherwise the state remains (A0, B0); The temperature is then reduced according to the specified annealing rate and T is checked. n Whether the termination conditions are met; Repeat the above steps until the optimal solution is found or the maximum number of iterations is reached; After the group meets the evaluation conditions, the group is output to obtain the optimization parameter library for the current time; Based on the lift coefficient, the oscillating ejector with the best flow control effect is selected from the optimization parameter library.

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