REAL-GAS EFFECTS ON THE NORMAL SHOCK BEHAVIOR NEAR CURVED WALLS

The influence of dense gases on the curvature and the strength of a normal shock near curved walls is discussed. In classical gasdynamics there is a postshock expansion and the shock is curved upstream if the wall is convex. The transonic small disturbance theory for the problem has been derived, including the fundamental gasdynamic derivative GAMMA and the second nonlinearity parameter LAMBDA. Special attention is drawn on flows where GAMMA becomes either zero or negative. According to the similarity laws, change of the sign of GAMMA changes the sign of the velocity disturbances phi(x) and phi(y) and of the wall curvature. Thus an expansion shock is followed by a compression if r < 0 and the wall is concave. Again the shock is curved upstream. A variation of the second nonlinearity parameter LAMBDA influences the strength of the shock, its curvature, and of the postshock expansion. Considering a GAMMA > 0 flow at a convex wall, the postshock expansion and the shock curvature are weakened if LAMBDA > 0. Comparing the real gas flow with the perfect gas flow (e. g., r = 1.2 and LAMBDA = 0), both the expansion behind the shock and the shock curvature increase if A becomes negative.