Control of the Periodic Turbulent Flow over a Semicircular Airfoil with the Use of the Slot Suction of the Air from a Circular Vortex Cell at Small Angles of Attack

It is shown that, in the case where, into the back wall of a semicircular airfoil with an angle of attack of 5°, a vortex cell of diameter 0.2 in fractions of the airfoil chord is built in and the mean-mass rate of slot suction of the air from this cell is larger than 0.15 of the incident-flow velocity, the pattern of the turbulent flow over the airfoil is transformed, and, at an optimum suction rate of 0.75, the lift coefficient of the airfoil reaches a maximum value of the order of 1.7 at an aerodynamic efficiency of 10.