Numerical Investigation of Unsteady Tangential Blowing at the Rudder of a Vertical Tailplane Airfoil

A numerical 2D investigation of a vertical tailplane airfoil using active flow control with tangential blowing over the rudder shoulder is conducted. The aim of the flow control application is to increase the maximum lift or side force, which can be created by the vertical tailplane, at critical flight conditions like the one-engine-inoperative failure case. In this case the rudder is highly deflected, leading to a large separation on the rudder without blowing. With constant tangential blowing at the rudder shoulder it was shown that fully attached flow can be achieved. To increase the efficiency, pulsed blowing is applied in the present study, leading to a similar increase in the lift coefficient at a reduced actuation mass flow rate requirement. Parameters like the blowing momentum coefficient and the dimensionless frequency are varied and the results are compared to those of the flow calculations with constant blowing. It is observed that pulsed blowing with a small momentum coefficient leads to a strong increase in the lift coefficient compared to constant blowing. The resulting lift increment depends on the dimensionless frequency selected.