Development and Analysis of Finite State Multi-Rotor Dynamic Inflow Models
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An analytical finite state multi-rotor dynamic inflow model known as Velocity Potential Superposition Inflow Model (VPSIM) is formulated from first principles. VPSIM superimposes the velocity potentials of each rotor to account for aerodynamic interactions among the rotors. Along with the recently developed Pressure Potential Superposition Inflow Model (PPSIM), inflow predictions of the VPSIM and PPSIM are compared against a high-fidelity numerical model known as Viscous Vortex Particle Method (VVPM) for various multi-rotor configurations. Inflow predictions show that VPSIM and PPSIM can capture fundamental interference effects with some differences. A new system identification methodology is developed to improve VPSIM predictions using the changes in the steady-state inflow components. The developed methodology effectively improves the correlation between VPSIM and VVPM for all flight conditions. Lastly, a convolution integral solution and two quasi-steady solutions are proposed to remove the backward time marching solution of the costates. With these alternative solutions, interference inflow predictions become much more efficient and straightforward to acquire. Finite state multi-rotor dynamic inflow models, VPSIM and PPSIM, capture fundamental rotor-on-rotor inflow interference effects for different configurations. Based on the model fidelity requirement, both models can be enhanced using either a higher-order wake model or experimental data. These models can be used in vehicle sizing and performance predictions, aeromechanics analyses, control law development, flight simulations, and handling quality analyses of multi-rotor configurations.