Impact of POD modes energy redistribution on flow reconstruction for unsteady flows of impulsively started airfoils and wings

摘要

Obtaining accurate solutions of unsteady flows during the design process of an aircraft can be a highly demanding task. Reduced basis methods (RBM) are commonly used to reduce the number of degrees of freedom while preserving high accuracy. RBM based on Proper Othogonal Decomposition (POD) have been extensively used but limitations exist with unsteady problems, where the temporal nonlinear dynamics of the flow needs to be addressed carefully. The accuracy in reconstructing nonlinear unsteady flows by means of RBM for a specific class of impulsively started lifting bodies is addressed. The snapshot POD approach and the recent Spectral POD will be comparatively studied to assess their capacity to reconstruct unsteady flows. The periodic motion past a cylinder will be considered as a benchmark test while the impulsive start of a 2D three-element airfoil and a 3D wing in high-lift configurations will be considered as use cases.