On the Relationship Between Unsteady Forces and Shock Angles on a Pitching Airplane Model


Department of Aerospace Engineering,Sharif University of Technology


series of supersonic visualization tests were performed on an airplane model in both
static and dynamic pitching cases. After image processing, the wave angles originating from di erent
parts of the model were carefully measured and averaged over several oscillation cycles. These ndings
were then compared with the corresponding normal force under similar conditions. The results reveal a
hysteresis loop in variations of the model shock angles with instantaneous angles of attack during up-stroke
and down-stroke motions. In comparison with the normal force hysteresis loop, it has been found that
there is an interesting relationship between the shape of the hysteresis loop of the shock angle and the
corresponding loop observed in the normal force data. Further, the oscillation frequency has been shown
to have similar e ects on both shock angle and aerodynamic force variations with the instantaneous angle
of attack.