Investigation of Blade Cascade Torsional Flutter Using the Discontinuous Galerkin Approach in Correlation with Experimental Measurements

Abstract

In this paper, the conditions under which low subsonic torsional flutter in rotor blades occurs are studied experimentally and numerically using the energy method with the assumption of travelling wave modes. As the test geometry, a blade cascade of five blades is considered. The three middle blades have a rotational degree of freedom, and the two outer blades are stationary. The experiments were performed in a wind tunnel at the Institute of Thermomechanics of the Czech Academy of Sciences. The numerical investigation was carried out using the developed CFD solver based on the discretization of the Favre-averaged Navier-Stokes equations by the discontinuous Galerkin method. A novel mesh-deformation algorithm suitable for fluid flow problems with multiple independently moving bodies is proposed. The CFD solver is benchmarked on test problems of flow around stationary and moving aerofoils. Following the energy method, the middle blades are forced to perform a harmonic pitching motion with various interblade phase angles. The total work per cycle of aerodynamic forces acting on the middle blade is evaluated. This analysis is performed both experimentally and numerically. The experiment measurement and the CFD solver predicted the formation of flutter for the same interblade phase angle. Moreover, qualitative agreement is evident between the experiment and simulation on the evaluated work per cycle for various interblade phase angles.