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Trident Scholar Program
Trident Scholar Program

MIDN 1/C Jonathan P. Peck - 13th Company

Characterization of the Far-Wake of a 6:1 Prolate Spheroid

Adviser: LCDR Ethan Lust, USN, Mechanical Engineering Department
External Collaborator: Dr. Matthew Jemison, Naval Surface Warfare Center, Carderock
Major: Mechanical and Nuclear Engineering Department

Even with the dramatic advances in computational power seen in the last decades, Computational Fluid Dynamics (CFD) models are as yet unable to predict transition, separation, and wake development for fluid flow over three-dimensional bodies to the desired level of accuracy in an acceptable amount of time. Without the ability to predict forces and moments experienced by the body, critical parameters such as drag and loads on control surfaces for air- and water-borne vehicles cannot be predicted. The prolate spheroid has long been a popular body upon which to verify CFD models because of its simple geometry and three-dimensional flow field. Advances in computational speed and experimental capabilities have prompted a renewed interest in related research.

An experiment was conducted in the large towing tank facility of the U.S. Naval Academy, using a 6:1 prolate spheroid, measuring 54 in. (1.4 m) in length and 9 in. (0.23 m) in diameter. The spheroid model was inclined by 15° and 20° relative to the undisturbed free surface, and towed at speeds yielding length-based Reynolds numbers from 0.5 to 4.2. A stationary stereo particle image velocimetry (SPIV) system was designed for the experiment and used to provide three-dimensional velocity maps in two spatial-dimensions (3C2D). These time histories show the trajectory of the wake as it leaves the tail of the model, the expansion of the wake width, the size, strength, and position of the primary vortical structures shed into the wake. These results will inform follow-on studies focused on measuring turbulent quantities in the far wake.

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