Mean velocity and turbulence measurements of flow around a 6:1 prolate spheroid

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Virginia Tech

Investigations of the three-dimensional flow around a 6:1 prolate spheroid model 1.37 m long were conducted in the separation and near wake regions along the leeward side. Mean velocity flow field measurements, at α = 10∘ and 15∘ , and at Re = 1.3 x 10⁶ (Ure= 15.2 mls) and 4.0x 10⁶ (Ure=45.7 m/s), were obtained at four axial locations along the afterbody. Boundary layer profiles and Reynolds shear stress measurements were obtained at two axial locations, with a = 100 and Re=4.0 X 10⁶. Results of the flow field measurements indicate vortical flow along the surface of the body, growing in strength with increasing Reynolds number and increasing angle of attack. Skewing of the three-dimensional boundary layer is seen in the boundary layer profiles, with the surface shear stress direction lagging the local free-stream velocity direction. Growth of the boundary layer is evident circumferentially and axially along the body. Results of the turbulence measurements show that the distribution of Reynolds stress quantities is different from that of a two-dimensional flow over a flat plate, due to the three-dimensional flow and separation that is present. Estimates of x and z eddy viscosities show that the eddy viscosity is not isotropic. Estimates of the mixing length compared to values for a two-dimensional flow model indicate that the model predicts high values for the mixing length. Comparisons made with results obtained at DFVLR in West Germany show good agreement for the mean velocity and Reynolds normal stress values; however, the agreement of the Reynolds shear stresses is not as good.