CN112810800A - Laminar flow separation control method based on local vibration of wing surface - Google Patents
Laminar flow separation control method based on local vibration of wing surface Download PDFInfo
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- CN112810800A CN112810800A CN202110113589.6A CN202110113589A CN112810800A CN 112810800 A CN112810800 A CN 112810800A CN 202110113589 A CN202110113589 A CN 202110113589A CN 112810800 A CN112810800 A CN 112810800A
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- vibration
- airfoil
- laminar flow
- flow separation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C3/00—Wings
- B64C3/36—Structures adapted to reduce effects of aerodynamic or other external heating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C23/00—Influencing air flow over aircraft surfaces, not otherwise provided for
- B64C23/04—Influencing air flow over aircraft surfaces, not otherwise provided for by generating shock waves
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
Abstract
The invention discloses a laminar flow separation control method based on local vibration of a wing surface, and belongs to the technical field of aircraft flow control. The method is characterized in that a flexible structure and a driving mechanism for driving the flexible structure to vibrate are arranged on the local part of the surface of the airfoil, the flexible structure vibrates in a reciprocating manner around a balance position under the action of the driving mechanism or external air flow, and the displacement of one point of the surface of the airfoil in a vibration area is determined by the deformation perpendicular to the chord length direction of the airfoil and the distribution rule of the deformation along the chord length direction of the airfoil. The invention can simplify the structure of the control system, reduce the volume and simultaneously obtain good laminar flow separation control effect.
Description
Technical Field
The invention belongs to the technical field of aircraft flow control, and particularly relates to a laminar flow separation control method based on local vibration of a wing surface.
Background
In recent years, as for the rapidly developed aircrafts such as the micro unmanned aerial vehicle and the high-altitude long-endurance unmanned aerial vehicle, the characteristic length reynolds number is low (Re is 10) due to small size, low flying speed or low air density of flying environment4～106). Viscous effect and unsteady effect of air under low Reynolds number conditionThe flow state is mainly laminar flow, the momentum is small, the capability of resisting the adverse pressure gradient is weak, and the flow is easy to separate from the wall surface to generate laminar flow separation. After laminar flow separation, the aircraft has reduced lift, increased drag, and stall, which adversely affects aerodynamic characteristics. There is therefore a need for flow control to inhibit laminar flow separation and improve aircraft aerodynamics.
There are many current laminar flow separation flow control techniques, which can be divided into two broad categories, passive and active, depending on whether energy is consumed, the former including local deformations, gurney flaps, etc., and the latter including blowing/suction, synthetic jets, plasma, etc.
In various active flow control technologies, control methods such as blowing/suction and the like need to arrange an air source pipeline inside a machine body, and the mechanism is complex; the plasma flow control technology needs a high-voltage power supply, and the miniaturization difficulty of a control system is very high
Disclosure of Invention
In view of this, the invention provides a laminar flow separation control method based on local vibration of a wing surface, which can simplify a control system structure, reduce the volume and simultaneously obtain a good laminar flow separation control effect.
A laminar flow separation control method based on local vibration of a wing surface is characterized in that a flexible structure and a driving mechanism for driving the flexible structure to vibrate are arranged on a local part of the wing surface, the flexible structure performs reciprocating vibration around a balance position under the action of the driving mechanism or external airflow, and the displacement of one point of the wing surface in a vibration region is determined by deformation perpendicular to the chord length direction of the wing and the distribution rule of the deformation along the chord length direction of the wing.
Further, the expression of the deformation amount Δ y in the direction perpendicular to the chord length of the airfoil is as follows:
wherein: a is the amplitude of the maximum point of deformation;
controlling the distribution of the deformation along the chord length direction of the airfoil profile for a normalized x coordinate; ω is angular frequency, equal to 2 pi times the vibration frequency, ω 2 pi f; t is time.
Further, the distribution rule of the deformation along the chord length direction of the airfoil profile is as follows:
wherein x1、x2And x denotes the x coordinates of the left and right end points and the middle point of the deformed region, respectively.
Further, the vibration mode and the vibration position of the flexible structure are defined differently.
Further, the driving mechanism adopts a pneumatic linear vibrator.
Has the advantages that:
1. the laminar flow separation control method based on the local vibration of the wing surface only needs to generate the small-amplitude vibration of the local surface of the wing, thereby greatly simplifying the structure of a control system and reducing the volume; and the controller can be flexibly arranged according to the specific conditions of different wings and wing profiles.
2. According to the laminar flow separation control method based on local vibration of the wing surface, energy is injected into fluid of a boundary layer through vibration of a small-scale local structure of the wing surface, so that the capability of flow resisting adverse pressure gradient is enhanced, and flow separation can be effectively inhibited.
Drawings
FIG. 1 is a schematic illustration of a local vibratory deformation mode of an airfoil and a coordinate system definition;
FIG. 2 is a plot of airfoil lift coefficient versus time;
FIG. 3 is a plot of airfoil drag coefficient versus time;
fig. 4 is a contour-flow diagram of the instantaneous pressure coefficient.
Detailed Description
The invention is described in detail below by way of example with reference to the accompanying drawings.
The invention provides a laminar flow separation control method based on local vibration of a wing surface, which is characterized in that a flexible structure and a driving mechanism for driving the flexible structure to vibrate are arranged on the local part of the wing surface, the flexible structure vibrates around a balance position in a reciprocating manner under the action of the driving mechanism or external airflow, and the vibration mode is shown as the attached drawing 1. The displacement expression of one point on the surface of the airfoil in the vibration region is shown as the formula (1) and the formula (2)
In the formula (1), delta y is the deformation amount in the direction vertical to the chord length of the airfoil, and A is the amplitude of the maximum deformation point;
controlling the distribution of the deformation along the chord length direction of the airfoil profile for a normalized x coordinate; ω is angular frequency, equal to 2 pi times the vibration frequency, ω 2 pi f; t is time. The distribution rule of the deformation along the chord length direction of the airfoil profile is as follows:
x in the formula (2)1、x2And x denotes the x coordinates of the left and right end points and the middle point of the deformed region, respectively.
The flow control by the laminar flow separation control method based on the local vibration of the wing surface, which is obtained by numerical simulation calculation and is based on the local vibration of the wing surface, is shown in the attached figures 2 and 3, and the flow control is carried out under the low Reynolds number flight condition (Reynolds number Re is 3 multiplied by 10)4Angle of attack α is 4 °), the lift coefficient and drag coefficient curves of the E387 airfoil are compared with the uncontrolled case, where the parameters of the controller are taken as: the position of the deformation region is 0-0.1 c, and the excitation frequency f is f0Excitation amplitude a is 2 × 10-3c (c is airfoil chord length, f)0The vortex shedding frequency of the airfoil in an uncontrolled condition). In fig. 2 and 3, the non-control case is shown by a solid line, and the control case is shown by a broken line; the curve represents the value of the transient state,the straight line represents the time mean. Compared with the uncontrolled condition, the time-average value of the unsteady lift coefficient of the airfoil profile is increased by about 36 percent, the time-average value of the drag coefficient is reduced by about 33 percent, and the time-average value of the lift-drag ratio is increased by about 102 percent after the flow control is added, which shows that the laminar flow separation control method based on the local vibration of the airfoil surface has obvious lift-increasing and drag-reducing effects. FIG. 4 shows a comparison of the contour-flow diagram of the instantaneous pressure coefficient of the flow around the airfoil under controlled conditions with the uncontrolled conditions. It can be seen that after the flow control is added, the separation zone at the rear of the upper surface of the airfoil disappears, and instead a series of vortices move downstream along the upper surface of the airfoil, and the pressure at the vortices is lower, so that the lift of the controlled case is greater.
From the above results it can be seen that: the laminar flow separation control method based on local vibration of the surface of the wing can obtain an obvious laminar flow separation control effect under the conditions that a control system is simple in structure and small in size.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A laminar flow separation control method based on local vibration of a wing surface is characterized in that a flexible structure and a driving mechanism for driving the flexible structure to vibrate are arranged on a local part of the wing surface, the flexible structure performs reciprocating vibration around a balance position under the action of the driving mechanism or external airflow, and the displacement of one point of the wing surface in a vibration region is determined by deformation perpendicular to the chord length direction of the wing and the distribution rule of the deformation along the chord length direction of the wing.
2. The method for controlling laminar flow separation based on local vibration of the surface of the airfoil according to claim 1, wherein the expression of the deformation amount Δ y in the direction perpendicular to the chord length of the airfoil is as follows:
wherein: a is the amplitude of the maximum point of deformation;
controlling the distribution of the deformation along the chord length direction of the airfoil profile for a normalized x coordinate; ω is angular frequency, equal to 2 pi times the vibration frequency, ω 2 pi f; t is time.
3. The method for controlling laminar flow separation based on local vibration of the surface of the airfoil according to claim 2, wherein the distribution rule of the deformation along the chord length direction of the airfoil is as follows:
wherein x1、x2And x denotes the x coordinates of the left and right end points and the middle point of the deformed region, respectively.
4. The method of claim 3, wherein the flexible structure has a vibration mode and a vibration position defined differently.
5. The method of claim 4, wherein the drive mechanism is a pneumatic linear vibrator.
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| CN202110113589.6A CN112810800B (en) | 2021-01-27 | 2021-01-27 | Laminar flow separation control method based on local vibration of wing surface |
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| CN202110113589.6A CN112810800B (en) | 2021-01-27 | 2021-01-27 | Laminar flow separation control method based on local vibration of wing surface |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB605765A (en) * | 1946-01-04 | 1948-07-29 | Norman Kenneth Walker | Improvements in or relating to aerofoil sections for low reynolds numbers |
| US5209438A (en) * | 1988-06-20 | 1993-05-11 | Israel Wygnanski | Method and apparatus for delaying the separation of flow from a solid surface |
| US6267331B1 (en) * | 1997-06-26 | 2001-07-31 | Ramot University Authority For Applied Research & Industrial Development Ltd. | Airfoil with dynamic stall control by oscillatory forcing |
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2021
- 2021-01-27 CN CN202110113589.6A patent/CN112810800B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB605765A (en) * | 1946-01-04 | 1948-07-29 | Norman Kenneth Walker | Improvements in or relating to aerofoil sections for low reynolds numbers |
| US5209438A (en) * | 1988-06-20 | 1993-05-11 | Israel Wygnanski | Method and apparatus for delaying the separation of flow from a solid surface |
| US6267331B1 (en) * | 1997-06-26 | 2001-07-31 | Ramot University Authority For Applied Research & Industrial Development Ltd. | Airfoil with dynamic stall control by oscillatory forcing |
Non-Patent Citations (3)
| Title |
|---|
| 刘强等: "低雷诺数翼型蒙皮主动振动气动特性及流场结构数值研究", 《力学学报》 * |
| 康伟等: "低雷诺数下翼面局部振动增升机理研究", 《航空学报》 * |
| 李冠雄等: "低雷诺数翼型局部振动非定常气动特性", 《航空学报》 * |
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