Date of Award

5-2017

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Graduate Studies

Committee Chair

Dr. J. Gordon Leishman

First Committee Member

Dr. John Ekaterinaris

Second Committee Member

Dr. William Engblom

Third Committee Member

Dr. Tasos Lyrintzis

Abstract

Numerical simulations using the Reynolds-Averaged Navier-Stokes (RANS) equations were conducted to study the development and turbulent decay of the tip vortices in the wake produced by a hovering rotor. The computational results were compared to detailed, dual plane Particle Image Velocimetry (PIV) measurements of a turbulent tip vortex trailed from a single-bladed rotor. The work investigated both the required mesh resolution and most suitable turbulence closure models with rotational/curvature corrections by assessing their predictions of the tip vortex properties and the overall physical nature of the rotor wake. It was found that even when using a higher-order accurate central differencing scheme, a minimum off-body grid spacing equal to 0.625% of the chord length was required to accurately predict the core dimension, peak swirl velocity and strength of the tip vortex. The rotational/curvature corrections applied to the Spalart-Allmaras turbulence model better preserved the vortex characteristics to longer wake ages than the same corrections applied to the k-ω SST model. In both cases, the correction proposed by Spalart and Shur outperformed the simplified correction proposed by Dacles-Mariani et al., with the latter providing little impact on the k-ωSST model. Lastly, Detached Eddy Simulation (DES) of the wake was studied in addition to the various RANS models with corrections to assess the effect of modeling anisotropic turbulence in the tip vortex.

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