LDG Method with P-Adaptivity Applied to LES of Blade-Vortex Interaction

Abstract

In the present work the Local Discontinuous Galerkin (LDG) method with polynomial adaptivity is applied to the Large Eddy Simulation (LES) of the parallel blade-vortex interaction (BVI). The BVI phenomenon occurs on helicopter and drone rotors in manoeuvring conditions and it produces impulsive changes in the pressure distributions, vibrations and noise. To deeply understand the mechanism of load generation related to the pressure field and three dimensional perturbations growth, to focus on the interaction between the vortex and the three dimensional structures in boundary layer and wake, accurate 3D unsteady numerical simulations of turbulent flows are necessary. For this reason, it is very important the use of a numerical code based on high order schemes such as LDG. Moreover, in the LDG approach, the numerical resolution can be varied on each element and in time, adapting to the requirement of the simulated flow and saving a large amount of computing resources. In the used numerical code the criterion for variation of the polynomial order is based on a refinement indicator especially suited for LES and based on the structure function. The local polynomial representation directly provides a means to separate large from small scale modes, thus providing the starting point for the definition of the subgrid scale models. In the present simulations, the subgrid scales contribution is represented with a sophisticated dynamic anisotropic subgrid model, suitable and well tested for wall resolved LES and complex separated turbulent flows. The BVI is simulated highlighting the effect of the vortex on the pressure distributions, on the boundary layer separation and on the resulting forces.