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High-Resolution Computational and Experimental Study of Rotary-Wing Tip Vortex Formation

Summary: High-Resolution Computational and Experimental Study
of Rotary-Wing Tip Vortex Formation
Karthikeyan Duraisamy,
Manikandan Ramasamy,
James D. Baeder,
and J. Gordon Leishman
University of Maryland, College Park, Maryland 20742
DOI: 10.2514/1.26575
The formation and rollup of a tip vortex trailed from a hovering helicopter rotor blade is studied in detail using
both computations and measurements. The compressible Reynolds-averaged Navier­Stokes equations are
computationally solved on an overset mesh system. The flow measurements are made using stereoscopic particle
image velocimetry. The high resolution of both the numerics and the measurements reveal multiple coherent
structures in the evolving rotor tip vortex flowfield. Secondary and tertiary vortices that result from crossflow
separations near the blade tip are identified. These vortices, along with a part of the trailed wake, are ultimately
entrained into the tip vortex that is formed downstream of the blade's trailing edge. The simulations clearly
demonstrate the resolution required to accurately represent the complex three-dimensional flowfield. The advantage
of particle image velocimetry, which has the ability to make planar measurements at a given instant of time, has been
fully used to validate the computational fluid dynamics predictions. Even though linear eddy viscosity models are
expected to inadequately represent the details of the turbulent quantities, good agreement is seen to be achieved with
the particle image velocimetry measurements of the mean flowfield. The various sources of computational and


Source: Alonso, Juan J. - Department of Aeronautics and Astronautics, Stanford University


Collections: Engineering