Rotational body aircraft resistance reduction method based on segmented skin rotation oscillation

Abstract

The invention discloses a rotation body aircraft resistance reduction method based on segmented skin rotation oscillation. The rotation body aircraft resistance reduction method comprises the steps that fluid mechanics parameters of a fuselage of a rotation body aircraft entering a turbulence stage in a cruising state are determined; determining a preset area for arranging a movable skin on the revolution body aircraft, and axially segmenting the revolution body aircraft body in the preset area according to a preset length; arranging a movable skin outside the fuselage in the preset area, wherein the axial length of the movable skin is the preset length; each movable skin is of a cylindrical rotary body structure, a driving mechanism is arranged between the movable skin and the fuselage and used for driving the movable skin to rotate and oscillate on the surface of the fuselage, and the rotating and oscillating directions of the adjacent movable skins are opposite; determining a movable skin rotation oscillation parameter at the initial moment when the revolution body aircraft enters the cruising stage; in the actual flight process of the rotorcraft, after the rotorcraft enters a cruising stage, the driving mechanism is used for driving the movable skin to rotate and oscillate according to the determined rotating oscillation parameters.

Description

Technical Field

[0001] The invention relates to the fields of aviation, navigation and aerodynamics, and in particular to a method for reducing the drag of a rotating body aircraft based on segmented skin rotational oscillation. Background Art

[0002] Drag reduction design is an important research issue in the design process of rotating body vehicles, and it is also an important way to improve the performance indicators of rotating body vehicles. Many underwater vehicles adopt a rotating body shape. When moving at high speed, their friction accounts for more than 80% of the total resistance; for rotating body aircraft, friction resistance also accounts for a considerable proportion.

[0003] Because frictional drag accounts for a high proportion of the drag of underwater spinning body vehicles, people are constantly exploring ways to reduce frictional drag. So far, many active and passive drag reduction methods have been explored. For underwater environments, in addition to the general boundary layer method to reduce frictional drag, some people have proposed supercavitation drag reduction methods; some drag reduction methods applicable to air environments are difficult to use in underwater environments, such as plasma excitation methods applicable to air environments.

[0004] Passive drag reduction technology has gained more popularity due to its low cost and simple implementation. For example, micro-grooves on the wall have begun to be used in actual engineering. However, passive drag reduction methods often have limited drag reduction effects. For example, micro-grooves can only reduce friction resistance by about 10% in theory, but this indicator cannot be achieved in actual engineering applications. There are few studies on active drag reduction technology in this field, and no practical application solutions can be formed. Summary of the invention

[0005] The purpose of the present invention is to provide a method for reducing the drag of a rotating body aircraft based on the rotational oscillation of a segmented skin. An active skin that rotates and oscillates circumferentially is arranged on the surface of the aircraft fuselage. The segments rotate and oscillate in relatively opposite directions to offset the excess torque, thereby realizing an active drag reduction mechanism of lateral oscillation.

[0006] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0007] A method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation, comprising:

[0008] Determine the fluid dynamics parameters of the rotating body vehicle when it enters the turbulent stage under the cruising state;

[0009] Based on the fluid mechanics parameters, determining a preset area on the fuselage of the rotating body of aircraft for arranging the movable skin, and axially segmenting the fuselage of the rotating body of aircraft in the preset area according to preset lengths;

[0010] A movable skin is arranged outside the fuselage within the preset area, and the axial length of the movable skin is the preset length; the movable skin is a cylindrical rotating body structure, and a driving mechanism is arranged between each section of the movable skin and the fuselage, which is used to drive the section of the movable skin to rotate and oscillate on the surface of the fuselage, and the rotation and oscillation directions of adjacent movable skins are opposite;

[0011] Determine the active skin rotation oscillation parameters when the rotating body vehicle enters the initial cruise phase;

[0012] During the actual flight of the rotational body vehicle, when it enters the cruise phase, the driving mechanism drives the movable skin to perform rotational oscillation according to the determined rotational oscillation parameters.

[0013] Furthermore, the method further comprises:

[0014] The fluid dynamics parameters in the current cruising state are collected in real time by sensors so as to correct the rotational oscillation parameters in real time; the active skin is driven and controlled in real time using the corrected rotational oscillation parameters.

[0015] Furthermore, the fluid mechanics parameters of the rotating body vehicle when entering the turbulent stage in the cruising state include: the position of the fuselage entering the turbulent stage, the boundary layer thickness δ, the surface kinematic viscosity coefficient ν and the surface friction speed u τ The fluid dynamic parameters are obtained through actual navigation tests or numerical simulation after modeling the rotating body of vehicle.

[0016] Furthermore, the preset area starts from the position where the rotating body vehicle enters the turbulent stage and ends at a distance of twelve times the boundary layer thickness δ from the rotating body vehicle's control surface; the control surface is a tail wing or a winglet.

[0017] Furthermore, the calculation formula of the preset length L is:

[0018]

[0019] Among them, L + is a dimensionless length, which represents the average streamwise length of the vortex faced by the rotating body vehicle in the cruising state. This length can be obtained by numerical simulation and post-processing analysis of the flow field; ν represents the surface kinematic viscosity coefficient, u τ Represents the surface friction speed.

[0020] Furthermore, within the preset area, it is segmented according to a preset length L, which is expressed as:

[0021]

[0022] in, Indicates rounding down, and M indicates the length of the preset area;

[0023] That is, an integer number of active skins are finally arranged in the preset area, and the remaining part that is less than the length of L is not arranged.

[0024] Furthermore, the parameters of the active skin rotation oscillation are:

[0025]

[0026] Where V θ is the rotational circumferential speed, V0 is the maximum circumferential speed, T0 is the rotational oscillation period, t is the oscillation time, and the maximum circumferential speed Rotational oscillation period V0 + and T + are the dimensionless maximum circumferential velocity and dimensionless oscillation period, respectively, which are obtained through numerical simulation.

[0027] Furthermore, the real-time collection of fluid dynamics parameters in the current cruising state includes the friction velocity of the active skin surface and the surface motion viscosity coefficient at the current moment, and these two values ​​are respectively used as parameters u τ , ν are substituted into the calculation formula of V0 and T0 to calculate V in real time θ , which continuously adjusts the motion of the active skin.

[0028] A rotating body aircraft is provided with a movable skin designed in the rotating body aircraft drag reduction method based on segmented skin rotational oscillation.

[0029] Compared with the prior art, the present invention has the following technical features:

[0030] The present invention constructs a segmented active skin on the surface of a rotating body aircraft that can rotate and vibrate within a certain range. Two adjacent segments of active skin rotate and oscillate in opposite directions, thereby achieving the purpose of reducing drag and noise by changing the near-wall self-sustaining system of the boundary layer. This solution can not only significantly reduce the frictional resistance of the aircraft, but also reduce the noise generated by the aircraft due to high-speed navigation, thereby improving the performance of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the segmentation of the active skin of the rotating body spacecraft;

[0032] Figure 2 It is a schematic diagram of the oscillation process of the active skin of the rotating body spacecraft;

[0033] Figure 3 This is a comparison chart of the friction resistance between the fixed skin (the original outer skin of the aircraft) and the movable skin;

[0034] Figure 4 Cross-sectional flow field diagrams of fixed skin and movable skin; (a) is the distribution of fixed skin, (b) is the distribution of movable skin when the drag coefficient is large, and (c) is the distribution of movable skin when the drag coefficient is small. DETAILED DESCRIPTION

[0035] Referring to the accompanying drawings, the present invention provides a method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation, comprising the following steps:

[0036] Step 1: Determine the fluid mechanics parameters of the rotating body vehicle when it enters the turbulent stage in the cruising state, including the position where the fuselage enters the turbulent stage, the boundary layer thickness δ, the surface kinematic viscosity coefficient ν, and the surface friction velocity u τ .

[0037] For the rotating-body vehicle to be modified, the position where the rotating-body vehicle enters the turbulent stage can be obtained through actual navigation tests or numerical simulation after modeling the rotating-body vehicle.

[0038] Step 2: Based on the fluid mechanics parameters, determine a preset area on the fuselage of the rotating body of aircraft for arranging the movable skin, and axially segment the fuselage of the rotating body of aircraft in the preset area according to preset lengths.

[0039] See attached Figure 1 The preset area starts from the position where the rotating body vehicle enters the turbulent stage and ends at a distance of twelve times the boundary layer thickness δ from the control surface (tail or winglet) of the rotating body vehicle; in this area, the influence of rotational oscillation on the flow field at the control surface position can be ignored, and the maximum drag reduction effect can be obtained.

[0040] The calculation formula of the preset length L is:

[0041]

[0042] Among them, L + is a dimensionless length, which represents the average streamwise length of the vortex faced by the vortex-forming vehicle in the cruising state. This length can be obtained by numerical simulation of the flow field and post-processing analysis of the flow field; in this scheme, it is determined to be 150.

[0043] In the preset area, it is segmented according to the preset length L, which is expressed as:

[0044]

[0045] in, Indicates rounding down, and M indicates the length of the preset area.

[0046] That is, if the ratio of the preset area length to L is not an integer, it is rounded down as the final number of segments; that is, an integer number of active skins are finally arranged in the preset area, and the remaining part is not longer than the length of L and is not arranged.

[0047] Step 3, arrange a movable skin outside the fuselage within the preset area, and the axial length of the movable skin is the preset length; the movable skin is a cylindrical rotating body structure, arranged outside the outer skin of the fuselage, and there is a gap between adjacent movable skins; a driving mechanism is arranged between each section of the movable skin and the fuselage, for driving the section of the movable skin to rotate and oscillate on the surface of the fuselage; and the rotation and oscillation directions of adjacent movable skins are opposite; the driving mechanism is a motor or a hydraulic mechanism.

[0048] Step 4, determine the active skin rotation oscillation parameters when the rotating body vehicle enters the initial moment of the cruise phase.

[0049] Among them, the parameters of active skin rotation oscillation are:

[0050]

[0051] Where V θ is the rotational circumferential speed, V0 is the maximum circumferential speed, T0 is the rotational oscillation period, t is the oscillation time, and the maximum circumferential speed Rotational oscillation period V0 + and T + are the dimensionless maximum circumferential velocity and dimensionless oscillation period, respectively, which are obtained through numerical simulation.

[0052] This paper designs a numerical simulation scheme, models the surface of the rotating body vehicle in ICEM, sets the surface boundary condition as active skin, assumes that the surface of the rotating body vehicle is in a fully turbulent state, and fixes the dimensionless maximum circumferential velocity V0. + =12, the dimensionless oscillation period ranges from T + =50-200; the simulated Reynolds number is 2800 and the Mach number is 0.2. Under this condition, the simulation results show that when the dimensionless oscillation period is T + =100, the maximum drag reduction effect can be obtained. Therefore, in this scheme, the dimensionless maximum circumferential speed V0 + =12, dimensionless oscillation period T + =100.

[0053] Step 5: During the actual flight of the rotating body vehicle, at the initial moment after entering the cruise phase, the active skin is driven by the driving mechanism to perform rotational oscillation according to the rotational oscillation parameters determined in step 4.

[0054] Furthermore, the fluid dynamics parameters in the current cruising state, including the surface friction speed of the active skin and the surface motion viscosity coefficient, can be collected in real time through sensors. The rotational oscillation parameters can be corrected in real time using these two values, and the active skin can be driven and controlled in real time using the corrected rotational oscillation parameters.

[0055] That is, in actual application, after entering the cruise phase, the rotating body vehicle continuously collects the current active skin surface friction speed and surface motion viscosity coefficient, and uses these two values ​​as parameters u τ , ν are substituted into the calculation formula of V0 and T0 to calculate V in real time θ The value is used to continuously adjust the movement of the active skin to achieve better drag reduction effect.

[0056] Example:

[0057] Based on the above scheme, the inventors calculated the movable skin and the fixed skin respectively. In order to accurately simulate the flow details inside the boundary layer, the direct numerical simulation method based on the Navier-Stokes equation was used to calculate the local boundary layer flow. In order to reduce the amount of calculation, the channel flow model method commonly used at home and abroad was used to simulate the fine flow inside the boundary layer.

[0058] In the calculation, the incoming flow Mach number is 0.2, and the Reynolds number based on the half-height of the channel is 3180; the atmospheric density, temperature and viscosity coefficient are calculated using sea level parameters. Figure 3 It is a comparison chart of the friction resistance between the fixed skin and the movable skin; Figure 4 It is the cross-sectional flow field diagram of the fixed skin and the oscillating wall; it can be seen that the friction resistance of the movable wall is reduced by more than 30% compared with the fixed skin.

[0059] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation, characterized in that: include: Determine the fluid dynamics parameters of the rotating body vehicle when it enters the turbulent stage under the cruising state; Based on the fluid mechanics parameters, determining a preset area on the fuselage of the rotating body of aircraft for arranging the movable skin, and axially segmenting the fuselage of the rotating body of aircraft in the preset area according to preset lengths; Arranging a movable skin outside the fuselage within the preset area, wherein the axial length of the movable skin is the preset length; The movable skin is a cylindrical rotating body structure, arranged outside the fuselage outer skin; A driving mechanism is arranged between each section of the movable skin and the fuselage, for driving the section of the movable skin to rotate and oscillate on the surface of the fuselage; and the rotation and oscillation directions of adjacent movable skins are opposite; Determine the active skin rotation oscillation parameters when the rotating body vehicle enters the initial cruise phase; During the actual flight of the rotational body vehicle, when it enters the cruise phase, the driving mechanism drives the movable skin to perform rotational oscillation according to the determined rotational oscillation parameters.

2. The method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation according to claim 1, characterized in that: The method further comprises: The fluid dynamics parameters in the current cruising state are collected in real time by sensors so as to correct the rotational oscillation parameters in real time; the active skin is driven and controlled in real time using the corrected rotational oscillation parameters.

3. The method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation according to claim 1, characterized in that: The fluid mechanics parameters of the rotating body vehicle when entering the turbulent stage in the cruising state include: the position where the fuselage enters the turbulent stage, the boundary layer thickness δ, the surface kinematic viscosity coefficient ν and the surface friction speed u τ The fluid dynamic parameters are obtained through actual navigation tests or numerical simulation after modeling the rotating body of vehicle.

4. The method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation according to claim 1, characterized in that: The preset area starts from the position where the rotating body vehicle enters the turbulent stage and ends at a distance of twelve times the boundary layer thickness δ from the control surface of the rotating body vehicle; the control surface is a tail wing or a winglet.

5. The method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation according to claim 1, characterized in that: The calculation formula of the preset length L is: Among them, L + is a dimensionless length, which represents the average streamwise length of the vortex faced by the rotating body vehicle in the cruising state. This length can be obtained by numerical simulation and post-processing analysis of the flow field; ν represents the surface kinematic viscosity coefficient, u τ Represents the surface friction speed.

6. The method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation according to claim 1, characterized in that: In the preset area, it is segmented according to the preset length L, which is expressed as: in, Indicates rounding down, and M indicates the length of the preset area; That is, an integer number of active skins are finally arranged in the preset area, and the remaining part that is less than the length of L is not arranged.

7. The method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation according to claim 1, characterized in that: The parameters of the active skin rotation oscillation are: Where V θ is the rotational circumferential speed, V0 is the maximum circumferential speed, T0 is the rotational oscillation period, t is the oscillation time, and the maximum circumferential speed Rotational oscillation period V0 + and T + are the dimensionless maximum circumferential velocity and dimensionless oscillation period, respectively, which are obtained through numerical simulation.

8. The method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation according to claim 7, characterized in that: The real-time collection of fluid dynamics parameters in the current cruising state includes the friction velocity of the active skin surface and the surface motion viscosity coefficient at the current moment, and these two values ​​are respectively used as parameters u τ , ν are substituted into the calculation formula of V0 and T0 to calculate V in real time θ , which continuously adjusts the motion of the active skin.

9. A spinning body vehicle, characterized in that: The rotating body vehicle is provided with an active skin designed according to the rotating body vehicle drag reduction method based on segmented skin rotational oscillation according to any one of claims 1-8.

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