UNSTEADY AERODYNAMIC FORCING FUNCTIONS - A COMPARISON BETWEEN LINEAR-THEORY AND EXPERIMENT

The unsteady flow field generated by rotating rows of perforated plate s and airfoil cascades is mathematically split into vortical and poten tial components using two methods, one relying entirely on velocity da ta and the other utilizing both velocity and unsteady static pressure data. The propagation and decay of these split flow perturbations are then examined and compared to linear theory predictions. The perforate d plate gusts closely resemble linear theory vortical gusts. Both spli tting methods indicate that they are dominantly vortical gusts with in significant unsteady static pressure perturbations. The airfoil gusts resemble linear theory combined vortical and potential gusts. The reco mbined airfoil gusts using the vortical and potential components calcu lated by the method using only unsteady velocity data do not necessari ly resemble the measured gusts, nor do they behave axially as predicte d by linear theory. The recombined airfoil gusts using the linear theo ry components calculated by the method using both unsteady velocity an d unsteady static pressure data do resemble the measured gusts and beh ave axially as predicted by linear theory, with the vortical component propagating unattenuated and the potential component decaying at the rare predicted by linear theory.