DES of a Slingsby Firefly Aircraft: Unsteady Flow Feature Extraction Using POD and HODMD

Abstract

In this paper, higher-order dynamic mode decomposition (HODMD) was applied to find the main patterns and frequencies of a transient aerodynamic flow field when an aircraft wing experiences stall. This method was applied to a computational flow simulation with a turbulence model based on a hybrid Reynolds-averaged Navier-Stokes large-eddy simulation (RANS/LES) [commonly known as detached-eddy simulation (DES)], where a combination of two-dimensional (2D) and three-dimensional (3D) flow visualization techniques are used to understand the vortex shedding from the main wing and its interaction with the tailplane. Simulation results were compared to the experimental ones and the results with proper orthogonal decomposition (POD) were compared with the HODMD analysis. The main advantage of HODMD resides in its identification of the main physical phenomena and the most relevant instabilities that lead the fluid dynamics. New flow control strategies can be defined when the underlying physics and the flow dynamics are known. Moreover, HODMD is robust in noisy and turbulent databases using less data than fast Fourier transform (FFT), which gives potential for future flow control applications, focused on improving the aircraft’s efficiency.