APPROACH TO THE DESIGN OF AIRFOILS WITH HIGH LIFT TO DRAG RATIOS.

A design procedure for low-speed single-element airfoils with high lift/drag ratios is presented. The procedure uses an inverse approach which proceeds from a set of desirable boundary layer characteristics, determined from the performance objectives, to a velocity distribution and, finally, to an airfoil shape. The boundary layer shape factor, which is a measure of the nearness of the boundary layer to separation, is used to define the boundary layer characteristics in the upper surface pressure recovery region. The velocities on the upper surface prior to pressure recovery are chosen to cause boundary layer transition at a desired location. The lower surface velocity distribution is selected to satisfy the requirement that a closed, non-reentrant shape which meets the specified structural requirements results.