Advanced Numerical Methods for the Prediction of Tonal Noise in Turbomachinery—Part II: Time Linearized Methods

Abstract

This is the second part of a series of two papers on unsteady computational fluid dynamics (CFD) methods for the numerical simulation of aerodynamic noise generation and propagation. It focuses on the application of linearized RANS methods to turbomachinery noise problems. The convective and viscous fluxes of an existing URANS solver are linearized and the resulting unsteady linear equations are transferred into the frequency domain, thereby simplifying the solution problem from unsteady timeintegration to a complex linear system. The linear system is solved using a parallel, preconditioned general minimized residual (GMRES) method with restarts. In order to prescribe disturbances due to rotor stator interaction, a socalled gust boundary condition is implemented. Using this inhomogeneous boundary condition, one can compute the generation of the acoustic modes and their near field propagation. The application of the timelinearized methods to a modern highbypass ratio fan is investigated. The tonal fan noise predicted by the timelinearized solver is compared to numerical results presented in the first part and to measurements.