Towards DES of flow around a rotorcraft fuselage using an immersed boundary method

In this research, an immersed boundary method (IBM) 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 IBM since it is a non-body-conformal mesh approach which incorporates geometrical complexities using momentum forcing to enforce its boundary condition onto the flow field. Detached Eddy Simulation (DES) 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 (TVD) reconstruction must be used to give physically reasonable results. Finally, an actuator surface model (ASM) 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, turbulent flat plate, and high Reynolds number cylinder. Lastly, the integrated IBM-ASM solver is validated against experimental measurements for the flow around a simplified airframe developed by Georgia Institute of Technology (GIT). Unsteady rotor-wake/fuselage interactions in a forward flight condition are analyzed. Results are competitive with existing best methods using a fraction of the setup and computational effort of the body-conforming method.