Numerical Determination of Indicial Lift and Moment Functions for a Two-Dimensional Sinking and Pitching Airfoil at Mach Numbers 0.5 and 0.6

The indicial lift and moment functions are determined approximately for sinking and pitching motion at Mach numbers M of 0.3 and 0.6. These functions are determined from a knowledge of the existing oscillatory coefficients at the low reduced frequencies and from approximate expressions of these coefficients at the high reduced frequencies. The beginning portion of the indicial lift function associated with an airfoil penetrating a sharp-edge gust in subsonic flow is evaluated by use of an exact method. By use of an approximate method for determining the remaining portion, the complete indicial gust function is determined for M 0.3, M 0.6, and M 0.7. All the indicial lift and moment functions are approximated by an exponential series the coefficients which appear in the exponential approximations for each indicial function are tabulated for M 0.5, M 0.6, and M 0.7.