A Review of Rotor Wake Physics and Modeling

This paper presents an overview of developments in rotorcraft wake modeling, particularly in the past decade, from the experimental, theoretical, and computational viewpoints. Current understanding of wake physics and limitations in wake modeling are summarized and juxtaposed with trends experimental and numerical research. Advances in flow imaging and velocimetry have provided evidence that supports simplified models of rotor wake behavior. Persistence of tip vortices to long ages, deterministic rollup phenomena leading to the transition to the far wake, and entrainment of a part of the nascent tip vortex (TV) vorticity into the counterrotating inboard wake have been shown through experiments. Advances in computational fluid dynamics have improved near- and mid-wake modeling capabilities. Hybrid methods that employ vortex element, vorticity transport, or vorticity confinement methods will be necessary for long-age (far-wake) modeling in the near future. A new hover experiment with high-accuracy measurements that tie the blade loading, rotor performance, and wake characteristics is one suggestion to facilitate numerical model correlation and development.