Evaluation of Nonlinear Rotor Wake/Stator Interaction by using Time Domain Chorochronic Solver

Konferensbidrag (offentliggjort, men ej förlagsutgivet), 2007

Rotor wake interactions with stators is an important aspect in turbomachinery noise generation. This paper deals with the time lagged periodic boundary condition (chorochronic periodicity) used in time domain Navier-Stokes equations solvers and its advantages/drawbacks over frequency domain linearized N-S equations solvers. The time lag periodic b.c. is used to solve the nonlinear three dimensional N-S equations using realizable k-epsilon turbulence model and time dependent wake defined at the inlet, with only a limited number of blade passages discretized. The time lag periodic b.c. has been validated through a number of 3D test cases. The acoustic response from a stator vane with wakes defined at the inlet is calculated using both a frequency domain linearized N-S equations solver and unsteady RANS equations solver with chorochronic periodicity, and the results are compared. Convergence time for the unsteady nonlinear calculation expressed in number of periods needed to reach a periodic solution depend on time lag size. This motivates a possible use of a few blades in the computational domain to minimize time lag/period ratio. Making the time lag periodic b.c. absorbing was shown to be a robust solution to handle instabilities that appeared in some of the test cases.