Date of Award

Spring 2022

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

J. Gordon Leishman

First Committee Member

Ebenezer P. Gnanamanickam

Second Committee Member

John A. Ekaterinaris

Abstract

The unsteady, three-dimensional, turbulent airwake over the Simple Frigate Ship No. 2 (SFS2) with quartering wind flow directions was studied in a low-speed wind tunnel facility. Surface oil flow visualization and time-resolved stereoscopic and planar particle image velocimetry (PIV) measurements were made for three crosswise planes and a single centerline streamwise plane. Measurements included various configurations with the bow of the ship model at two different quartering wind conditions of 10 and 20 degrees, as well as cases with and without the effects of a simulated atmospheric boundary layer (ABL). A comparative analysis of the time-averaged flow structures between the quartering wind cases and the pure headwind measurements showed significant differences in the development of the airwake. For both quartering wind cases, the funnel wake had a trailing vortex on the windward side and large cross-sectional velocity magnitudes. The flight deck recirculation region decreased in size and became asymmetric for both quartering wind cases. Different flight deck vortical structures were found, indicating a difference within the flow field based on the yaw angle. A spectral analysis showed the streamwise fluctuations contained more energy for the quartering wind cases in the funnel wake region, which was also seen in the turbulent fluctuations. Two-point velocity correlations revealed large-scale coherent motion in the streamwise direction. The coherent behavior was further related to the observed time-averaged flow field structures through proper orthogonal decomposition (POD). The POD analysis highlighted the nontrivial behavior that was inherent to the airwake. These findings further emphasize the complexity of the airwake and necessity of understanding the development of the airwake under a broad range of conditions.

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