Background
Types of high-lift devices
Mechanical high-lift devices
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Plain Flap As shown in Figure 3(1), in order to increase camber angle, the part of trailing edge of airfoil is bended to downward of the airfoil.×
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Split Flap As shown in Figure 3(2), this devise mechanism is resembled with the plane flap. However, the sprit device is only bended the lower side of the trailing edge.
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Slotted Flap As shown in Figure 3(3), a flap increase a camber angle and make a space said as slot between main part of the airfoil and the flap. By leading the high pressure flow slot from under the airfoil to the upside the airfoil through the slot, the peeling air flow in the trailing edge area is prevented and CL is increase.
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Triple Slotted Flap As shown in Figure 3(4), the small airfoil with high camber is provided between the main airfoil and the flap. This small airfoil is said as vane. There are 3 sections of slots.
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Fowler Flap As shown in Figure 3(5) this flap mechanism has two deformation and two effects. Firstly, the flap is moved almost to the rear, to increase the lift by increasing the wing area. Secondly, further flap is moved to the rear, it is bend in downward at the same time. In addition by increasing the camber angle with increasing the wing area, to increase the lift.
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Slats As shown in Figure 3(6), The part of the airfoil in leading edge side is separated in order to provide a space as said slats between flap and main airfoil. The high pressure air thorough the slats to upside of airfoil form under side. This flow leading is help to prevent the peeling of airflow. Therefore, stall angle and Max CL are increase.
Boundary Layer Control
Static control high-lift devices
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Vortex generator This device uses the property that turbulent boundary layer to the flow is not easily peeled off than the laminar boundary layer. The projection on the airfoil surface forcibly transition boundary layer from laminar flow to turbulent. This projection is said as the vortex generator [6]. At high angle of attack, the effect of increasing the stall angle. However, at low angle of attack, projections increase the drag and exacerbate the high-speed performance.
Active control high-lift devices
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Suction and/or blowing High lift is obtained by adding momentum to the wing surface boundary layer by means of suction and/or blowing. Conventionally, suction and/or blowing utilizes the engine exhaust flow or a compressor driven by the engine. Therefore, it is expected that the effect of suction/blowing is not worth the weight increase because electrically powered SUAVs don’t have an engine exhaust, making it necessary to mount an additional motor for the compressor.
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Vibration type As shown in Figure 4, the high lift device has small size Electromagnetic actuators on the upside surface of the airfoil in the leading edge [10]. Each actuator generates the vibration in vertical direction to the airflow direction in order to add the momentum to the airflow of upside surface of the airfoil. In case of high angle of attack, the device provides to increase the stall angle by 3° and Maximum CL by 25%. However, this device needs a lot of actuators, the mass increase is a challenge to the practical design.×
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The Sound wave type This high lift device improves the aerodynamic characterstics of the airfoil by utilizing properties such as prompting the reattachment of laminar separation by an acoustic excitation vibration [11]. This device system is as follow. The speakers of sound source are placed around the wing as shown in Figure 5. The sound wave (pressure) is provided toward the wing. The L/D is increased then the ordinary airfoil. However, the speaker must be placed above the surface of the airfoil. It is a challenge to the practical design.×
Present challenge
Methods
Design requirements
Proposed mechanism and its effect
Results
Validation of proposed mechanism
Experimental wing
Experimental conditions
Experimental results
Belt speed [m/s]
|
0
|
10
|
20
|
---|---|---|---|
Max CL
| 1.62 | 1.66 | 2.68 |
Max CL angle [deg] | 11 | 17 | 23 |
Max L/D | 69.8 | 117 | 66.3 |
Max L/D angle [deg] | 4 | 0 | 4 |
Max L/D CL
| 1.18 | 1.17 | 1.25 |
Stall angle [deg] | 11 | 23 | 27 |
Discussion
Flow visualization
Experimental conditions
Airfoil
|
GOE478(Moving surface)
|
GOE478
| |
---|---|---|---|
Belt Speed [M/s] | 10 | 20 | - |
Airspeed [m/s} | 10 | 10 | 10 |
Re | 1.1×105
| ||
Attack of Angle [deg] | 0 deg~ |
Experimental results
Design feasibility of SUAV with circulation-controlled high-lift wing
The amount of extra battery for the task of sUAV
The mechanism design of the high lift device to SUAV
Without the devise [g]
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With the device [g]
| |
---|---|---|
Wing mass | 220 | 341 |
Extra battery mass | 42 | |
Weight of UAV | 750 | 913 |
Total increase in mass | 163 | |
Increae payload | 340 |