Lift enhancement control method of thin flat-plate at post stall angles of attack

An investigation on lift characteristics of thin flat-plate airfoil was conducted in a low speed wind tunnel. The effect of suction on the airfoil surface was studied in this experiment at various locations downstream of the airfoil leading-edge with different suction coefficients. A strain gauge force balance was used to measure the axial force and normal force on the airfoil. A TSI 2D-PIV system was used to measure the velocity field over the airfoil. The free stream velocity is 5m/s, and the Reynolds number is 6.7×10⁴/m. The results indicate that appropriate suction flow control has the effects of delaying the stall angle of attack by 7° and nearly double enhancing the lift coefficient. When suction is applied near the leading-edge, it may be easier to reattach the flow for smaller suction coefficients. However, for the suction coefficients in a certain range, the lift of the airfoil almost keeps constant with increasing suction coefficient. There is an optimal location for the suction control. A maximum lift coefficient can be generated for suction coefficients less than 3% when x/c equals to 0.4.