Airbrake controls of pitching moment and pressure fluctuation for an oblique tail fighter model

The pitching moments of a fighter model at an incidence of 32° without and with nine airbrakes are simulated by solving the unsteady Reynolds-averaged Navier-Stokes equations. The maximum reduction (60.22%) of the total pitching moment is obtained by the airbrake with deflection angle of 60° and length of 0.115 times the wing span. Furthermore, the unsteady flowfields are predicted by the improved delayed detached-eddy-simulation model. The breakdowns of the forebody and strake vortices are advanced, and the flow is blocked by the airbrake, jointly leading to a reduction of the pitching moment. Surprisingly, the pressure fluctuations on the oblique vertical tail are also attenuated due to the existence of the airbrake. A maximum reduction of overall sound pressure level by 11.8 dB is found near the leading-edge on the outer surface of the vertical tail due to the use of the 60T1 airbrake. The bursting vortices from the forebody and strake move towards the symmetry plane owing to the low-pressure region after the airbrake, weakening the unsteady interactions between the bursting vortices and oblique vertical tail.