Validation of a Linearized Navier-Stokes Based Flutter Prediction Tool Part1: Numerical Methods

Abstract

This is the first of two papers describing the validation o a tool chain for flutter prediction. This first paper provides an overview of the numerical methods and their verification. The second paper presents the detailed validation of the tool chain on the basis of experimental data obtained from measurements of an annular cascade sector comprising slightly twisted turbine blades. The tool chain consists of commercial programs for grid generation, structural analysis and the computation of the stead flow, and software developed at DLR for data conversion, aeroe- lastic preprocessing, and solving the time-linearized RANS equations. The time-linearized solver computes the unsteady flow in the frequency domain based on the linearization of the RANS equations about a steady solution which, in the process chain presented here, is provided by the commercial solver. We inves- tigate the issues that arise from using different spatial discretizatiom schemes and turbulence models for the computation of the steady and the time-linearized solutions. Results are presented for Standard Configurations 4, 10 and 11, and a freestanding tur- bine blade from a rear stage of a stationary gas turbine. It is shown that with an appropriate choice of the spatial discretiza- tion parameters good agreement with reference data can be ob- tained.