A reduced order model for uncoupled and coupled cascade flutter analysis. (February 2016)

• Record Type: Journal Article
• Authors: Su, Dan; Zhang, Weiwei; Ye, Zhengyin
• Is Part Of: Journal of fluids and structures. Volume 61(2016:Feb.)
• Page Start: 410
• Page End: 430
• Publication Date: 2016-02
• Subjects: Cascade flutter -- Reduced-order model -- Computational fluid dynamic -- Uncoupled method -- Fluid–structure coupling; Fluid-structure interaction -- Periodicals; Fluid mechanics -- Periodicals; Structural dynamics -- Periodicals; Structural analysis (Engineering) -- Periodicals; 620.106
• DOI: 10.1016/j.jfluidstructs.2015.11.013
• Languages: English
• ISSNs: 0889-9746

Abstract

Abstract: It is computation-intensive and time-consuming to conduct the direct numerical simulation of the fluid and structure interaction of an entire blade row. This paper presents a reduced-order model (ROM) that significantly improves the efficiency of turbomachinery flutter analysis. This ROM is constructed with the system identification technique and under the modal theory through a single implementation of unsteady flow computation of several blade passages. The ROM for uncoupled flutter analysis can obtain the aerodynamic damping coefficients of all the Inter-Blade Phase Angles (IBPA) and structural nature frequencies. The ROM for coupled flutter analysis is to solve the eigenvalues of aeroelastic equations established by coupling the ROM with the structural dynamic equations of the whole annular blade row in state-space form. This ROM method is validated by its application to two test cases—an axial-flow cascade (Standand Test Configuration 4, STCF4) and a transonic axial-flow fan rotor (NASA Rotor 67). The results verify the capability of the proposed ROM method to compute the flutter characteristics of turbomachinery blades accurately and efficiently. Compared with the direct unsteady computational fluid dynamic (CFD) method (the direct unsteady Navier–Stokes method and fluid–structure coupling method), the computational efficiency of the ROM method is improved by more than 10 times. The comparison shows that the damping coefficients and vibration frequencies of coupled flutter calculation are close to uncoupled results when mass ratio increases. This ROM approach is highly suitable for the parametric, mistuning, and multi-mode coupling analysis at the early stage of turbomachinery blade design. Highlights: A reduced-order model is constructed with the identification of CFD training computation. The ROM method is validated by comparing with the direct CFD method. The ROM significantly improves the efficiency of cascade flutter analysis. The coupled results are close to the uncoupled results when mass ratio increases. The cascade flutter is the resultant effect of all the unstable responses.