Flow Over a Six-to-One Prolate Spheroid at High Reynolds number

The flow over a six-to-one prolate spheroid at non-zero angle of attack involves three-dimensional boundary-layer development, transition, and separation; and steady and unsteady near-wake dynamics. Thus, experimental studies of this flow provide a canonical benchmark for computational fluid dynamics (CFD) model development and validation due to its geometric simplicity and complex flow behavior. While measurements of detailed flow structures are invaluable for high-resolution validation, integral quantities such as force and moment coefficients, and surface pressure distributions provide essential first-order validation metrics. The study reported here involved direct measurements of normal force and pitching moment for a nominally-3-meter long six-to-one prolate spheroid that was towed at speeds from 0.15 to 5.0 m/s (length-based Reynolds numbers from 0.4 to 15 million) and angles of attack from 0° to 20° in the David Taylor Model Basin of the Naval Surface Warfare Center – Carderock Division. Surface pressure distributions were also obtained at a Reynolds number of 4.2 million. The model included a trip composed of 36 evenly spaced slender pegs at an axial distance 300 mm downstream of the model's nose. The results show agreement with prior investigations and extend the measured Reynolds number range for this flow. Comprehensive documentation of experimental methods is provided to facilitate future CFD validation efforts.