Towards computational modeling of propeller-wing-fuselage interactions for Urban Air Mobility
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Engineering topics
Steven Seokkwan Yoon
Publications and source records attributed to Steven Seokkwan Yoon.
Computational Analysis of a Quiet Single-Main Rotor Helicopter for Air Taxi Operations
A computational study has been done on NASA’s quiet single-main rotor helicopter concept for urban air mobility using high-fidelity computational fluid dynamics, rotorcraft comprehensive analysis tools, and computational aeroacoustics. High-order accurate schemes, dual-time stepping, and the delayed detached-eddy simulation model have been employed. A loose-coupling approach between the flow solver and the rotorcraft comprehensive code is implemented to include vehicle trim and blade motions. Acoustic simulations based on the Ffowcs-Williams and Hawkings equations have been performed to compute the rotor noise. Different blade geometries and tip speeds are analyzed, and performance and acoustics results are compared. The vehicle has been simulated in hover and cruise, with flight conditions representative of an air taxi mission. The quiet single-main rotor helicopter is one of the conceptual designs intended to focus and guide NASA’s research activities in support of aircraft development for vertical take-off and landing air taxi operations.
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Tiltwing Transition Flight Analysis Using High-Fidelity CFD
Transition from hover to forward flight and vice versa represents the most critical flight phase of tiltwing aircraft. Despite its importance to ensure a safe operation, the aerodynamics of this maneuver are not sufficiently understood. This paper focuses on the study of transition flight for NASA’s six-passenger tiltwing air taxi by means of high-fidelity computational fluid dynamics simulations. On the basis of a static trim solution, four points within the transition corridor are analyzed: transition mode at wing tilt angles of60and44, and airplane mode at airspeeds of110 ktand155 kt. We investigate the balance of forces and moments for rotor-borne and wing-borne regimes, and how rotor-on-rotor and rotor-on-wing interactions affect performance. The simulations indicate that during the early stages of transition, the vortices remain in close proximity to the proprotors, inducing large fluctuations on the order of the mean blade loading. Additionally, the blowing and swirling effects of the proprotor wakes delay flow separation over a portion of the wing. The mid-transition conditions appear to be critical, with extensive regions of separated flow over the wing. In airplane mode, proprotor-wing slipstream effects can be exploited to enhance lift generation. The results of this paper contribute to a deeper understanding of the complex aerodynamic interactions during transition flight to enable a safer and more efficient operation of tiltwing aircraft.
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