Book Description

Computer programs are described which implement a small disturbance potential flow theory for the two-dimensional unsteady transonic flow about thin airfoils undergoing low reduced frequency harmonic oscillations. The theory is based upon the treatment of the unsteady flow as a small perturbation to the steady transonic flow. Separating the perturbation potential into a steady and unsteady component results in a pair of coupled boundary value problems for the components. The governing equation for the steady perturbation potential is the usual nonlinear transonic potential equation and it is solved in computer program STRANS using the mixed differencing relaxation procedure of Murman and Cole. The governing equation for the unsteady perturbation potential is linear and, for the harmonic boundary disturbance considered, of mixed elliptic hyperbolic type depending on the local nature of the steady potential. Using a steady solution previously generated by STRANS, computer program UTRANS solves the unsteady potential equation by the same relaxation procedure. The solution procedures are found to be quite efficient, permitting the calculation of unsteady aerodynamic forces to engineering accuracy in a few minutes on a CDC 6600 computer.