Active Flow Control

Since the beginning of human flight, many researcher and engineers have attempted to increase lift and reduce drag by changing aircraft structure or configuration. These efforts have led to efficient design of modern aircraft. However, existing high-lift generation system does not satisfy the strict design requirements for a higher-efficiency and higher-performance aircraft, and as a result, more efficient flow control strategy has been investigated.

If an aircraft operates in a variety of flow condition, turbulent transition and flow separation can be occur in the wing surface. The flow separation phenomena cause decrease lift-to-drag ratio, reduce the controllability of the flight. Therefore, flow separation and laminar flow control is essential to improve the aerodynamic performance of aircraft.

Fig. 1. Flow seperation at high angle of attack

There have been continual researches in the field of flow control, especially, on the flow control methods using MEMS since the 1990s. Based on the industrial development of MEMS technology, flow control technology can be applied to aircraft. Many researchers and engineer are conducted about the flow separation delay, turbulent transition adjustment, missile's attitude control etc. In addition, the flow control system can be used in the reducing the takeoff distance, payload, aircraft noise and obtaining high mobility. It can lead to many economic benefits.

Fig. 2. Active flow control system

As a result, The wind tunnel test and numerical analysis is conducted for develop active flow control device using MEMS. For this purpose, the theoretical study of MEMS flow control devices, accurate and efficient development of numerical methods, 2-D and 3-D flow analysis using CFD, MEMS design and manufacturing technology acquisition, wind tunnel tests researches are studied.

Fig. 3. Seperation conrol on 2-D airfoil (left) / Fig. 4. Flow structure of synthetic jet slot exit (right)

Fig. 5. Active flow control of 3-D wing by synthetic jet array