Papers Published

  1. Dowell, E.H. and Ueda, T. and Goorjian, P.M., Transient decay times and mean values of unsteady oscillations in transonic flow, AIAA J. (USA), vol. 21 no. 12 (1983), pp. 1762 - 4 .
    (last updated on 2007/04/10)

    Kerlick and Nixon (ibid., vol 19, p.1496, 1981) have made the important point that, when using a finite difference, time-marching computer code to investigate the lift on an oscillating airfoil in transonic flow, it is necessary to carry the solution sufficiently far forward in time that an essentially steady-state solution is obtained. Moreover, they offer a method for estimating the transient time before the steady state is reached. They note that, if one stops the time-marching solution before the transient is complete and the steady state is reached, then one may reach the incorrect conclusion that a change in the mean lift has occurred due to the oscillating motion of the airfoil when in fact no such change has occurred. The authors comment that for a narrow Mach number range the time for the transient to decay and a steady state to be reached is extraordinarily long. Moreover, for a very narrow range of Mach number a nonzero mean value of lift can occur for an airfoil of symmetrical profile oscillating about a zero angle of attack

    flow instability;oscillations;transonic flow;