Implementation of a free-vortex wake model in real-time simulation of rotorcraft

Free-vortex wake models are capable of providing an accurate and physically detailed representation of the main rotor wake for flight dynamics simulation. Recent advances in computing power and efficient algorithms have made it feasible to use free wakes for real-time simulation. The CHARM free-vortex wake model was integrated with the GENHEL flight dynamics simulation of the UH-60A helicopter. A high fidelity wake model was defined by increasing the spatial and temporal resolution of the wake until a converged response was observed, but this baseline model could not execute in real-time. A parametric study was performed to find the best combination of wake parameters to achieve real-time execution with minimal deviation from the baseline model. Multiple variations in the wake properties were tested for execution framerate and their frequency and time responses in the pitch and roll axes were compared to those of the baseline model. A real-time model was selected and showed reasonable agreement with the baseline model as compared to a finite-state inflow model. The free wake models resulted in significantly different off-axis response and large amplitude response than the finite-state inflow model. A parallel implementation of the free wake model was also investigated. An increase in computational efficiency could be achieved using a distributed processing approach with asynchronous communications.