VALIDATION OF A NONLINEAR UNSTEADY AERODYNAMIC SIMULATOR FOR VIBRATING BLADE ROWS

A time-accurate Euler/Navier-Stokes analysis is applied to predict uns teady subsonic and transonic flows through a vibrating cascade. The in tent is to validate this nonlinear analysis along with an existing lin earized inviscid analysis via result comparisons for unsteady flows th at are representative of those associated with blade putter. The time- accurate analysis has also been applied To determine the relative impo rtance of nonlinear and viscous effects on blade response. The subsoni c results reveal a close agreement between inviscid and viscous unstea dy blade loadings. Also, the unsteady surface pressure responses are e ssentially linear and predicted quite accurately using a linearized in viscid analysis. For unsteady transonic flows, shocks and their motion s cause significant nonlinear contributions to the local unsteady resp onse. Viscous displacement effects tend to diminish shock strength and impulsive unsteady shock lends. For both subsonic and transonic flows , the energy transfer between the fluid and the structure is essential ly captured by the first-harmonic component of the nonlinear unsteady solutions, but in transonic flows, the nonlinear first-harmonic and th e linearized inviscid responses differ significantly in the vicinity o f shocks.