A drag reduction method for a spinning vehicle based on segmented skin rotating oscillation

Abstract

This invention discloses a drag reduction method for a rotary-body vehicle based on segmented skin rotational oscillation, comprising: determining the hydrodynamic parameters of the rotary-body vehicle when the fuselage enters the turbulent phase during cruise; determining a preset area on the rotary-body vehicle for arranging movable skin, and axially segmenting the fuselage of the rotary-body vehicle within the preset area according to a preset length; arranging movable skin outside the fuselage within the preset area, the axial length of the movable skin being the preset length; the movable skin being a cylindrical rotating body structure, with a drive mechanism arranged between it and the fuselage to drive the segment of movable skin to rotate and oscillate on the fuselage surface, and the rotational oscillation directions of adjacent movable skin segments being opposite; determining the rotational oscillation parameters of the movable skin at the initial moment when the rotary-body vehicle enters the cruise phase; during actual flight of the rotary-body vehicle, after entering the cruise phase, driving the movable skin to rotate and oscillate according to the determined rotational oscillation parameters using the drive mechanism.

Description

Technical Field

[0001] This invention relates to the fields of aviation, navigation, and aerodynamics, and specifically to a drag reduction method for a rotating body vehicle based on segmented skin rotational oscillation. Background Technology

[0002] Drag reduction design is an important research issue in the design process of rotary-body vehicles and a crucial way to improve their performance. Many underwater vehicles adopt rotary-body shapes, and when traveling at high speeds, friction accounts for almost 80% of the total drag; for rotary-body aircraft, frictional drag also accounts for a considerable proportion.

[0003] Because frictional drag accounts for a high proportion of the drag of underwater rotating vehicles, people have been constantly exploring methods to reduce it. To date, many active and passive drag reduction methods have been developed. For the underwater environment, in addition to the commonly used boundary layer method to reduce frictional drag, some researchers have proposed supercavitation drag reduction methods. Some drag reduction methods suitable for air environments are difficult to apply to underwater environments, such as plasma excitation methods suitable for air environments.

[0004] Passive drag reduction technologies have gained popularity due to their low cost and ease of implementation. For example, drag reduction using micro-grooves has begun to be applied in practical engineering projects. However, passive drag reduction methods often have limited drag reduction effects. For instance, micro-grooves can theoretically reduce frictional resistance by a maximum of about 10%, but this target cannot be achieved in practical engineering applications. Active drag reduction technologies have received less research in this field, and no practical application solutions have been developed. Summary of the Invention

[0005] The purpose of this invention is to provide a drag reduction method for a rotating body aircraft based on segmented skin rotational oscillation. The method involves arranging a movable skin with circumferential rotational oscillation on the surface of the aircraft fuselage. By having each segment rotate and oscillate in opposite directions, excess torque is offset, thereby achieving an active drag reduction mechanism based on lateral oscillation.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A drag reduction method for a rotating body vehicle based on segmented skin rotational oscillation includes:

[0008] Determine the hydrodynamic parameters of the spinning body vehicle as it enters the turbulent phase during cruise;

[0009] Based on the aforementioned hydrodynamic parameters, a preset area for arranging movable skin on the fuselage of the spinning-body vehicle is determined, and the fuselage of the spinning-body vehicle within the preset area is axially segmented according to a preset length.

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

[0011] Determine the rotational oscillation parameters of the active skin at the initial moment when the rotating body vehicle enters the cruise phase;

[0012] During actual flight, once the cruise phase begins, the moving skin rotates and oscillates according to the determined rotational oscillation parameters, driven by the drive mechanism.

[0013] Furthermore, the method also includes:

[0014] The fluid dynamic parameters under the current cruise state are collected in real time by sensors to correct the rotational oscillation parameters in real time; the corrected rotational oscillation parameters are then used to drive and control the moving skin in real time.

[0015] Furthermore, the hydrodynamic parameters of the rotating vehicle entering the turbulent stage during cruise 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 velocity u. τ The fluid dynamic parameters are obtained through numerical simulation after actual navigation tests or modeling of counter-rotating aircraft.

[0016] Furthermore, the preset area starts from the position where the spinning vehicle enters the turbulent stage and extends to a distance of twelve times the boundary layer thickness δ from the control surface of the spinning vehicle; the control surface is the tail fin or winglet.

[0017] Furthermore, the formula for calculating the preset length L is as follows:

[0018]

[0019] Among them, L + ν is a dimensionless length representing the average flow-direction length of the vortex encountered by the spinning vehicle during cruise. This length can be obtained through numerical simulation of the flow field and subsequent post-processing analysis; ν represents the surface kinematic viscosity coefficient, u τ This indicates the surface friction speed.

[0020] Furthermore, within the preset area, it is divided into segments according to a preset length L, as follows:

[0021]

[0022] in, This indicates rounding down, and M represents the length of the preset region.

[0023] That is, an integer number of active skins will be placed within the preset area. If the remaining part is not long enough for one L, it will not be placed.

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

[0025]

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

[0027] Furthermore, the real-time acquisition of hydrodynamic parameters under the current cruise state includes the friction velocity and surface kinematic viscosity of the active skin surface at the current moment, and these two values ​​are used as parameters u. τ Substitute ν into the calculation formulas for V0 and T0 to calculate V in real time. θ The value is used to continuously adjust the movement of the active skin.

[0028] A rotating body vehicle, wherein the rotating body vehicle is provided with a movable skin designed in the aforementioned method for reducing drag of a rotating body vehicle based on segmented skin rotational oscillation.

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

[0030] This invention constructs movable skins on the surface of a rotating body vehicle in segments, which are capable of rotating and vibrating within a certain range. Two adjacent movable skin segments rotate and oscillate in opposite directions. By changing the near-wall self-sustaining system of the boundary layer, the purpose of drag reduction and noise reduction is achieved. This solution can not only significantly reduce the frictional drag of the vehicle, but also reduce the noise generated by the vehicle due to high-speed navigation, thereby improving the performance of the vehicle. Attached Figure Description

[0031] Figure 1 A schematic diagram of the segmented movable skin of a rotating body-type aircraft;

[0032] Figure 2 A schematic diagram of the oscillation process of the moving skin of a rotating body-type aircraft;

[0033] Figure 3 A comparison diagram of the frictional resistance between the fixed skin (the original outer skin of the aircraft) and the movable skin;

[0034] Figure 4 The diagrams show the cross-sectional flow fields of the fixed skin and the movable skin; where (a) is the distribution of the fixed skin, (b) is the distribution of the movable skin when the drag coefficient is large, and (c) is the distribution of the movable skin when the drag coefficient is small. Detailed Implementation

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

[0036] Step 1: Determine the hydrodynamic parameters of the rotating body vehicle when it enters the turbulent phase during cruise, including the position of the fuselage entering the turbulent phase, the boundary layer thickness δ, the surface kinematic viscosity coefficient ν, and the surface friction velocity u. τ .

[0037] For a spinning vehicle to be modified, the position where the spinning vehicle enters the turbulent stage can be obtained through actual flight tests or numerical simulation after modeling the spinning vehicle.

[0038] Step 2: Based on the fluid dynamic parameters, determine the preset area on the fuselage of the spinning vehicle for arranging the movable skin, and divide the fuselage of the spinning vehicle within the preset area into axial segments according to the preset length.

[0039] See appendix Figure 1 The preset region is defined as the area from the point where the spinning vehicle enters the turbulent phase to a distance of twelve times the boundary layer thickness δ from the control surface (tail or winglet) of the spinning vehicle. Within this region, the influence of rotational oscillation on the flow field at the control surface position can be ignored, while the maximum drag reduction effect can be obtained.

[0040] The formula for calculating the preset length L is:

[0041]

[0042] Among them, L + The dimensionless length represents the average flow-direction length of the vortex faced by the spinning vehicle during cruise. 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] Within the preset area, it is divided into segments according to a preset length L, represented as follows:

[0044]

[0045] in, This indicates rounding down, and M represents the length of the preset region.

[0046] That is, if the ratio of the preset area length to L is not an integer, it is rounded down to the nearest integer 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 long enough to be arranged.

[0047] Step 3: A movable skin is arranged outside the fuselage within the preset area. The axial length of the movable skin is the preset length. The movable skin is a cylindrical rotating structure arranged outside the fuselage outer skin. Adjacent movable skins are fitted with a clearance. A drive mechanism is arranged between each movable skin segment and the fuselage to drive the movable skin segment to rotate and oscillate on the fuselage surface. The rotation and oscillation directions of adjacent movable skins are opposite. The drive mechanism is a motor or a hydraulic mechanism.

[0048] Step 4: Determine the active skin rotation oscillation parameters at the initial moment when the rotating body vehicle enters the cruise phase.

[0049] The parameters for the rotational oscillation of the active skin are:

[0050]

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

[0052] This paper proposes a numerical simulation scheme. The surface of the spinning vehicle is modeled in ICEM, and the surface boundary condition is set as a moving skin. During the simulation, it is assumed that the surface of the spinning vehicle is in a fully turbulent state, and the dimensionless maximum circumferential velocity V0 is fixed. + =12, the dimensionless oscillation period takes values ​​in the range of T. + =50-200; the simulated Reynolds number is 2800 and the Mach number is 0.2. Under these conditions, the simulation results show that when the dimensionless oscillation period is T + The maximum drag reduction effect can be obtained when V = 100. Therefore, in this scheme, the dimensionless maximum circumferential velocity 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 moving skin is driven to rotate and oscillate according to the rotational oscillation parameters determined in Step 4.

[0054] Furthermore, the fluid dynamics parameters under the current cruise state can be collected in real time by sensors, including the friction speed and surface kinematic viscosity coefficient of the moving skin. These two values ​​are used to correct the rotational oscillation parameters in real time, and the corrected rotational oscillation parameters are used to drive and control the moving skin in real time.

[0055] In practical applications, after entering the cruise phase, the rotating body vehicle continuously collects the friction velocity and surface kinematic viscosity of the moving skin surface at the current moment, and uses these two values ​​as parameters u. τ Substitute ν into the calculation formulas for V0 and T0 to calculate V in real time. θ The value is used to continuously adjust the movement of the active skin in order to achieve a better drag reduction effect.

[0056] Example:

[0057] Based on the above scheme, the inventors performed calculations for both the movable and fixed skins. To accurately simulate the flow details within the boundary layer, a direct numerical simulation method based on the Navier-Stokes equations was used to calculate the local boundary layer flow. To reduce computational load, the commonly used channel flow model was adopted, aiming for detailed simulation of the flow within the boundary layer.

[0058] The Mach number of the incoming flow was 0.2, and the Reynolds number based on the half-height of the channel was 3180. Atmospheric density, temperature, and viscosity were calculated using sea-level parameters. Figure 3 This is a comparison chart of the frictional resistance between fixed skin and movable skin; Figure 4 This is a cross-sectional flow field diagram of a fixed skin and an oscillating wall; it can be seen that the frictional resistance of the moving wall is reduced by more than 30% compared to the fixed skin.

[0059] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A drag reduction method for a rotating body-type aircraft based on segmented skin rotational oscillation, characterized in that, include: Determine the hydrodynamic parameters of a spinning vehicle entering the turbulent phase during cruise, including: the position of the fuselage entering the turbulent phase, the boundary layer thickness δ, and the surface kinematic viscosity coefficient. ν and surface friction speed u τ The fluid dynamic parameters are obtained through numerical simulation after actual sea trials or modeling of counter-rotating integrated aircraft. Based on the aforementioned fluid dynamics parameters, a preset area for arranging movable skin on the fuselage of the spinning-body vehicle is determined, and the fuselage of the spinning-body vehicle within the preset area is axially segmented according to a preset length. A movable skin is arranged on the exterior of the fuselage within the preset area, with an axial length equal to the preset length. The movable skin is a cylindrical rotating structure arranged outside the outer fuselage skin. A drive mechanism is arranged between each segment of the movable skin and the fuselage to drive that segment of the movable skin to rotate and oscillate on the fuselage surface. The rotational oscillation directions of adjacent movable skins are opposite. The preset area begins at the point where the spinning vehicle enters the turbulent stage and extends to a distance of twelve times the boundary layer thickness δ from the control surfaces of the spinning vehicle. The control surfaces are tail fins or winglets. The preset length... L The calculation formula is: in, L + , a dimensionless length, represents the average flow-direction length of the vortex faced by the spinning vehicle during cruise. This length can be obtained by numerical simulation of the flow field and post-processing analysis of the flow field. Determine the rotational oscillation parameters of the active skin at the initial moment when the rotating body vehicle enters the cruise phase; During actual flight, once the cruise phase begins, the moving skin rotates and oscillates according to the determined rotational oscillation parameters, driven by the drive mechanism.

2. The drag reduction method for a rotating body-type vehicle based on segmented skin rotational oscillation according to claim 1, characterized in that, The method further includes: The fluid dynamic parameters under the current cruise state are collected in real time by sensors to correct the rotational oscillation parameters in real time; the corrected rotational oscillation parameters are then used to drive and control the moving skin in real time.

3. The drag reduction method for a rotating body-type vehicle based on segmented skin rotational oscillation according to claim 1, characterized in that, Within the preset area, according to the preset length L It is divided into segments, represented as: in, This indicates rounding down. M Indicates the length of the preset area; That is, an integer number of active skins will be placed within the preset area, with the remaining portion not enough for one. L If the length is too short, then no arrangement will be made.

4. The drag reduction method for a rotating body-type vehicle based on segmented skin rotational oscillation according to claim 2, characterized in that, The parameters for the rotational oscillation of the active skin are: in V θ The circumferential speed is the rotational speed. V 0 represents the maximum circumferential velocity. T 0 represents the rotational oscillation period. t Oscillation time, maximum circumferential velocity Rotational oscillation period ; V 0 + and T + These are the dimensionless maximum circumferential velocity and the dimensionless oscillation period, respectively, obtained through numerical simulation.

5. The drag reduction method for a rotating body-type vehicle based on segmented skin rotational oscillation according to claim 4, characterized in that, The real-time acquisition of hydrodynamic parameters under the current cruise state includes the friction velocity and surface kinematic viscosity of the active skin surface at the current moment, and these two values ​​are used as parameters. u τ , ν Substitute into , In the calculation formula, thus calculating in real time. The value is used to continuously adjust the movement of the active skin.

6. A rotating body-shaped aircraft, characterized in that, The rotating body vehicle is provided with a movable skin designed in the drag reduction method for rotating body vehicles based on segmented skin rotational oscillation according to any one of claims 1-5.

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