Flutter computation of turbomachinery cascades using a parallel unsteady Navier-Stokes code

A quasi-three-dimensional multigrid Navier-Stokes solver on single- and mul tiple-passage domains is presented for solving unsteady flows around oscill ating turbine and compressor blades. The conventional direct store method i s used for applying the phase-shifted periodic boundary condition over a si ngle blade passage. A parallel version of the solver using the message pass ing interface standard is developed for multiple-passage computations. In p arallel multiple-passage computations, the phase-shifted periodic boundary condition is converted to a simple in-phase periodic condition. Euler and N avier-Stokes solutions are obtained for unsteady flows through an oscillati ng turbine cascade blade row with both the sequential and the parallel code s. It is found that the parallel code offers almost linear speedup with a s lope close to 1 on multiple CPUs. In addition, significant improvement is a chieved in convergence of the computation to a periodic unsteady state in t he parallel multiple-passage computations due to the use of the in-phase pe riodic boundary conditions compared with that in the single-passage computa tions with phase shifted periodic boundary conditions via the direct store method. The parallel Navier-Stokes code is also used to calculate the flow through an oscillating compressor cascade. Results are compared with experi mental data and computations by other authors.