Accurate and efficient prediction of blade aerodynamic damping is critical for the design of turbomachines such as gas and steam turbines. Traditional unsteady time-marching CFD methods used in aerodynamic damping calculations are expensive because they require simulation of many or all blade passages in a given blade-row. In order to reduce computational cost, one can use a pitch-change method and reduce the problem to a small sector of the geometry (one or two blades). Even still, the time-marching method is expensive as many vibration cycles must be simulated to reach a quasi-steady periodic state. To further reduce computational cost, a time/frequency solution method is required.
This paper uses an implicit pressure-based time/frequency solution method in combination with a Fourier transformation (FT) pitch-change method and validates its implementation in ANSYS CFX solver. Three cases are investigated, including Standard Configuration 11 (subsonic and transonic), and NASA Rotor 67 transonic fan. Predictions of unsteady pressure coefficient are compared against the experimental data and reference full wheel simulations, over a range of nodal diameters. Computational resources (CPU time) required by the time/frequency method are compared to time transient simulations and discussed in detail.