Coupled flight dynamics and CFD simulations of the helicopter/ship dynamic interface

The objective of this study is the development of a virtual dynamic interface simulation using fully coupled Navier-Stokes CFD with a helicopter flight dynamics model. The results show the initial coupling of the codes and development of baseline cases. The long-term goal is to develop more efficient numeric techniques and integrate the simulation on advanced computing hardware with the objective of achieving real-time computations. The unsteady flow over the generic simple frigate shape (SFS2) was calculated using the CRAFT Tech computational fluid dynamics solver, CRUNCH CFD®. The GENHEL-PSU simulation code was integrated with the flow solution, and simulations were performed with a non-linear dynamic inversion control law to hold hover or follow a prescribed trajectory. An Actuator Disk Model with Gaussian distribution of source terms stacked vertically around the rotor disk is developed and sensitivity studies were performed for cases with the vehicle fuselage dynamics frozen. Free flight simulations were then performed, with full rotorcraft flight dynamics regulated by the NLDI controller and coupled with the CFD flow solutions. The time history results include: the helicopter hovering in an open domain both in and out of ground effect, the helicopter hovering over the SFS2 ship deck, and the helicopter performing an approach to the SFS2 ship deck. Results compare responses with no CFD coupling, using a one-way coupled CFD airwake, and using folly coupled simulations. Fully coupled simulations are shown to be feasible, to exhibit reasonable physical behavior, and to capture expected aerodynamic coupling effects.