Investigation of Computational Modeling Approaches to Prediction of Tiltrotor / Obstacle Interactions at Model-Scale

Computational modeling of aerodynamic interactions between a rotorcraft and obstacle with high-fidelity computational fluid dynamics (CFD) is resource-intensive endeavor due to the large region of circulating flow where flow gradients must be resolved. Modeling approaches that reduce the computational cost of modeling the rotor, airframe, and ground obstacle are therefore highly desirable. Helios permits the application of a wide range of models to rotors, fuselages, and other bodies in a high-fidelity rotorcraft aeromechanical simulation environment. This work investigated the application of these models to the different components of the rotor wake / ground obstacle interaction problem to establish the cost/fidelity trade-off space for engineering analysis. Comparisons with model-scale experimental data indicate utilizing an actuator line rotor model is a cost-effective method for predicting aircraft performance in recirculating flows, though some differences in both power and download were observed when the rotors are within two rotor radii of the ground plane. Immersed boundary modeling of the ground obstacle was observed to be effective when the rotor tips are at least two rotor radii away from the ground obstacle, but significant errors were observed during operations with only one rotor radius of tip clearance.