Calculation of the Unsteady Transonic 2D Cascade Flow for Aeroelastic Applications.

Abstract

The numerical results of a code for computing the unsteady transonic flow in a 2D cascade of harmonically oscillating blades are presented. The calculation of the flow field is based on an Euler code using flux vector splitting. After a description of the basic equations and the special numerical techniques applied in the code, results are presented for the first harmonics of pressure, lift and moment coefficients. For the present investigations two basic oscillation modes have been chosen: tuned modes where all blades perform oscillations with the same frequency, same amplitude and a constant interblade phase angle, and mistuned modes, where all blades are oscillating with the same amplitude, but with varying frequency from one blade to another. In the case of tuned bending modes, the computed results are compared with the experimental data from a standard configuration given by the IUTAM "Workshop on Aeroelasticity in Turbomachine Cascades". Special attention is directed to the occurence of aerodynamic instability in the oscillating cascade. The Mach numbers and interblade phase angles at which the above-mentioned experimental test case shows unstable behaviour are generally well-reproduced by the computational results.