Effects of periodic spanwise blowing on delta-wing configuration characteristics

Abstract

Periodic leading-edge spanwise blowing was tested on a 60-deg swept delta-wing fighter aircraft model in a low-speed wind tunnel, up to an angle-of attack of a = 60 deg. At low frequencies, lift and drag coefficients correspond to the pulsating blowing pressure: when the valve is open, they reach the same values as with continuous blowing, and when it is closed, they agree with the no-blowing values. A lag in the response time is observed, which is equal at low incidences to the freestream convective time, but increases to 30 convective times at a = 3040 deg. This response time is much longer when the valve closes than when the valve opens at a = 20-30 deg. These features are similar to those of delta wings in unsteady flows, such as in pitching or plunging motions. They are insensitive to the flow parameters and are valid at low blowing frequencies. At high frequencies, lift and drag coefficients do not correspond to the pulsating pressure, but remain at an intermediate value between those of continuous and no blowing. In both cases, the mean lift and drag coefficients are equal to the values obtained by continuous blowing at the same mean momentum coefficient.