An investigation of the influence of shock motion on flutter of rotors and cascades is presented. The present paper illustrates how a perturbation scheme can be used to calculate the nonlinear effects due to thickness, camber, and incidence to second order in a perturbation parameter. An approximate theory is also given, that accounts for the first-order quasisteady effects of shock motion and also allows experimentally determined shock structures and parameters to be used. The unsteady aerodynamic forces resulting from shock movements are shown to have a pronounced effect on the flutter boundaries of cascades representative of large fan rotors. Both stabilizing and destabilizing effects are observed, depending on interblade phase angle and shock structure. At low reduced frequencies, the shock-induced loads can destabilize bending oscillations sufficiently to cause single-degree-of-freedom bending flutter. It is also possible to explain the stabilizing effect of the back pressure on supersonic rotor flutter, as observed experimentally. a c CLV> CMV h k k L m M M 2 N P u,v t/oo S x,y;x',y' Xr 7 6 6 2 P a v Nomenclature = speed of sound; also location of pitching axis, Eq. (8) = 2b = blade chord = force and moment coefficients, Eqs. (26), (27) = bending deflection, positive down = ub/U= reduced frequency --kM//3 2 -lift per unit span, positive up = mass per unit span of blade = moment per unit span, about midchord, positive clockwise; also Mach number = cascade exit Mach number = (7+ l)M 2 /(2]8 2 ); also number of blades in rotor = static pressure =/? 3 -/?! = pressure jump at shock reflection, Fig. 3 = V$ = velocity vector = perturbation velocities in x y y directions = freestream velocity at upstream infinity = blade spacing (Fig. 1) = total potential = phase angle of shock motion = circular frequency = SCOS0 = time = cascade coordinate systems (Fig. 1) = mean location of shock reflection point = instantaneous shock reflection point and oscillation amplitude, respectively = angle of attack; also torsional deflection its = ratio of specific heats of air = stagger angle = flow deflection at trailing edge = m/irpb 2 = mass ratio of blade = air density = interblade phase angle = steady (mean) perturbation potential = unsteady perturbation potential about mean flow Superscripts and Subscripts( " ) = nondimensional quantity: lengths with respect to semichord b, velocities with respect to £/",, pressure with respect to p^ U0 = amplitude of harmonic quantity oo = conditions at upstream infinity (freestream) s = quantity associated with shock wave