Real-Time Dynamic Inflow Model for a Coaxial Helicopter Configuration Using the Lattice–Boltzmann Method

A real-time two-way fully-coupled Lattice-Boltzmann Method (LBM) flow field simulation model was applied as a dynamic inflow model for the full-scale coaxial CoAx 600 helicopter configuration. The LBM was coupled with a flight dynamics model of the CoAx 600 vehicle. To couple the LBM with the flight dynamics model, a linear/harmonic actuator disk approach was used in the LBM simulation, which was previously applied and validated for a single main rotor helicopter; this model was extended for use with the coaxial rotor configuration. The coupled LBM inflow model was compared against a simpler static inflow computation and to CoAx 600 flight test data obtained by the Technical University of Munich. The LBM inflow model showed excellent agreement with both the static inflow results and the flight test data, while offering far greater modeling flexibilities, such that complicated flight conditions, ground/wall effects and rapidly changing external flow perturbations can be accounted for in a two-way coupled fashion. In particular, because the LBM model resolved coaxial rotor interactional effects, it predicted the yaw dynamics of the helicopter without additional empirical gain terms, which were necessary for the simpler static inflow computation. For the resolution used in the present study, the LBM inflow model was real-time capable using a single NVIDIA A100 GPU. The LBM model showed promise for future work involving coaxial rotor interactions with external gusts, unsteady bluff body airwakes, or unsteady ground effect operations.