A CFD-based compositional methodology of unsteady aerodynamic modeling for turbomachinery

Direct CFD method was used in the analysis of flutter characteristics for blades of turbomachinery, and its main trouble was the relative computational effort. The present paper introduces a CFD-based compositional modeling methodology of unsteady aerodynamics for turbomachinery that can compute the aerodamping coefficients of vibrating turbine blades with equal Inter-Blade-Phase-Angle. Several unsteady CFD computations with different number of blade passages are needed for the construction of the Reduce-Order-Model (ROM). Following the superposition principle of small disturbance flow and the periodicity of the flow field of turbomachinery, a series of unsteady aerodynamic ROMs with more blade passages are acquired by solving mirror equations. The aeroelastic characteristics of Standard Test Configuration-4 (STCF-4) are analyzed by using this method. The results are compared with that attained by direct CFD method and ROM with single CFD computation. They agree well with each other. By applying this new ROM, the computational efficiency is improved by ten times, compared with direct CFD method while remaining the precision.