Towards Detached-Eddy Simulation of Flow Around Rotorcraft Using Immersed Boundary Method

Abstract

A coupled immersed boundary method and unsteady actuator surface model (IBM–ASM) is developed and implemented into a finite-volume-based incompressible Navier–Stokes solver within OpenFOAM for efficient full rotorcraft simulations. Given a geometry definition, a simple Cartesian mesh generated through a fully automated process can be used for an immersed boundary method (IBM) since it is a non-body-conformal mesh approach that incorporates geometrical complexities using momentum forcing to enforce its boundary condition onto the flowfield. Detached-eddy simulation is employed for the turbulence modeling, and an appropriate wall function is defined and implemented as needed for efficient high-Reynolds-number computations. Also, it is demonstrated that a total-variation-diminishing reconstruction must be used to produce physically reasonable results. Finally, an actuator surface model is integrated with the IBM solver, concluding the overall IBM–ASM methodology to address rotorcraft problems. Detailed verification and validation of the IBM solver are demonstrated for a low-Reynolds-number cylinder, a turbulent flat plate, and a high-Reynolds-number cylinder. Lastly, the IBM–ASM solver is validated against experimental measurements for the flow around a simplified airframe developed by the Georgia Institute of Technology. Unsteady rotor-wake/fuselage interactions in a forward flight condition are qualitatively and quantitatively analyzed. Results are competitive with existing best methods using a fraction of the setup and computational effort of the body-conforming method.