Real-Time Simulation of Dynamic Inflow Using Rotorcraft Flight Dynamics Coupled With a Lattice-Boltzmann Based Fluid Simulation

摘要

Rotorcraft flight in the vicinity of objects or in the objects' wake is one of the most challenging situations for pilots. In order to provide safe and realistic training of such situations in flight simulators, a real-time capable model is proposed. This dynamic inflow model extracts the inflow velocities from a real-time Lattice-Boltzmann fluid simulation and passes them to a blade element based flight dynamics code to capture the rotorcraft motion. The resulting thrust of the rotor is passed back to the fluid simulation and imposed on the rotor disk. To model the influence of arbitrary objects in the vicinity of the rotorcraft on the fluid mechanics and flight dynamics, the objects are represented by wall boundary conditions and realized at simulation run-time using ray-tracing algorithms. The shape and position of the objects relative to the rotorcraft are updated from a topographical database in every step of the simulation. This two-way coupled approach enables the real-time calculation of the dynamic inflow into the rotors without prior knowledge of the flow field. To assess the validity of the proposed model, a convergent behavior at increased resolution of the fluid simulation is shown. To validate the effect of objects on the inflow, the power required in hover and forward flight in ground effect is evaluated. Furthermore, the dynamic behavior of the inflow is discussed using the reaction of the inflow of a fixed rotor to step inputs in the controls. The results from the coupled fluid dynamics/flight dynamics inflow model show good agreement when compared to a more established reference model, namely the Pitt-Peters inflow model.