| A novel scheme has been proposed in which the behaviour of forebody vortices at high angles of attack is dynamically manipulated to generate side forces and yawing moments which provide suitable directional control of a fighter aircraft as a conventional rudder loses its effectiveness. Exploiting the bi-stable nature of the vortices, the method involves deliberately switching the vortices, between the two stable states, at high frequency with two forward-blowing nozzles located near the apex of the forebody nose. A previous water-tunnel experiment has demonstrated that the side force can be reliably switched by the efflux from the nozzles with a small blowing coefficient and at a certain alternating frequency. To continue the research on this control scheme, a wind-tunnel experiment has been conducted to determine the variation of time-average side force and yawing moment with blowing duty cycle at various alternating frequencies, and to determine whether the method will perform at high Reynolds number.; Results from force and moment measurements have shown that in a non-sideslip condition, time-average side force and yawing moment vary linearly with the duty cycle of the valves, and symmetrically about a zero-axis. This signifies the potential of this technique as an alternate form of side force control. Control was demonstrated at a Reynolds number of 1.76 x 10{dollar}sp5{dollar} with a minimum blowing coefficient of 0.00066 and a maximum reduced frequency of 0.32, both of which are improvements over the water-tunnel findings. In sideslip, the linear variation is retained to a large extent but the symmetry of the side force and yawing moment response is about non-zero values. Unfortunately a desirable side force response due to blowing could not be demonstrated at a Reynolds numbers above {dollar}1.76times10sp5.{dollar} Unsuitable nozzle location is suspected as the cause. |
