Numerical Simulations of Unsteady Cascade Flows

[+] Author and Article Information
D. J. Dorney

Computational & Design Methods, United Technologies Research Center, East Hartford, CT 06108

J. M. Verdon

Theoretical & Computational Fluid Dynamics, United Technologies Research Center, East Hartford, CT 06108

J. Turbomach 116(4), 665-675 (Oct 01, 1994) (11 pages) doi:10.1115/1.2929459 History: Received February 19, 1993; Online June 09, 2008


A time-accurate Navier–Stokes analysis is needed for understanding the relative importance of nonlinear and viscous effects on the unsteady flows associated with turbomachinery blade vibration and blade-row noise generation. For this purpose an existing multi-blade-row Navier–Stokes analysis has been modified and applied to predict unsteady flows excited by entropic, vortical, and acoustic disturbances through isolated, two-dimensional blade rows. In particular, time-accurate, non-reflecting inflow and outflow conditions have been implemented to allow specification of vortical, entropic, and acoustic excitations at the inlet, and acoustic excitations at the exit, of a cascade. To evaluate the nonlinear analysis, inviscid and viscous numerical simulations were performed for benchmark unsteady flows and the predicted results were compared with analytical and numerical results based on linearized inviscid flow theory. For small-amplitude unsteady excitations, the unsteady pressure responses predicted with the nonlinear analysis show very good agreement, both in the field and along the blade surfaces, with linearized inviscid solutions. Based on a limited range of parametric studies, it was also found that the unsteady responses to inlet vortical and acoustic excitations are linear over a surprisingly wide range of excitation amplitudes, but acoustic excitations from downstream produce responses with significant nonlinear content.

Copyright © 1994 by The American Society of Mechanical Engineers
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