EFFECT OF MOVING SURFACES ON THE AIRFOIL BOUNDARY-LAYER CONTROL

The concept of moving surface boundary-layer control, as applied to a Joukowsky airfoil, is investigated through a planned experimental program complemented by a flow visualization study. The moving surface was provided by rotating cylinders located at the leading and trailing edges of the airfoil. The leading-edge rotating cylinder extends the lift curve without substantially affecting its slope, thus effectively increasing the maximum lift and delaying stall. In general, the performance improves with an increase in the ratio of cylinder surface speed Uc to the freestream speed V. A rotating trailing-edge cylinder affects the airfoil characteristics in a fundamentally different manner. It acts as a flap and shifts the CL vs α curves to the left, thus increasing the lift coefficients before stall. For example, at α = 4 deg, it increased the CL by about 320%. In conjunction with the leading-edge cylinder, it can provide significant improvements hi lift over the entire range of small to moderately high angles of incidence (α ≤ 18 deg). A flow visualization study substantiates, rather spectacularly, effectiveness of the concept. © 1988 by the authors. © The American Institute of Aeronautics and Astronautics, Inc. All rights reserved.