High-order large eddy simulation and immersed boundary method on dynamic meshes: Application to rotorcraft aerodynamics

A novel Large Eddy Simulation (LES) solver using an Immersed Boundary Method (IBM) is presented. The compressible Navier-Stokes equations are solved using eighth order accurate Summation By Parts (SBP) finite difference schemes. A curvilinear formulation is used and the solver is coupled with a novel dynamic mesh formulation allowing local grid refinement by clustering the grid points in regions of high vorticity. The stretched vortex subgrid scale model is used. This formulation is compared to the state-of-the-art HPCMP CREATE^{T M} -AV Helios with NASA OVERFLOW and NASA FUN3D as near-body solvers using unsteady RANS. Both solvers are applied for two main rotorcraft applications: the 2-bladed Knight and Hefner (1938) rotor hover case is used for both validation and to study the physics of the rotor wake. In addition, the Penn State University (PSU) hub drag case is used to demonstrate the capabilities of each solver to simulate complex rotating geometry, and to accurately predict flow and global quantities such as drag forces. Accuracy and efficiency of each solver are compared. Predictions for the 2-bladed Knight and Hefner rotor hover case are in excellent agreement with the measured data. Detailed comparisons of the rotor wake are performed between the two solvers. Similar comparisons are performed for the rotor hub case. Good agreement with experimental measurements can be seen for the drag forces, as well for the velocity predictions downstream of the rotating hub.