Prediction of a Prolate Spheroid Undergoing a Pitchup Maneuver

Prediction of the timedependent flow around a 6 : 1 prolate spheroid undergoing a pitchup maneuver were obtained using Detached-Eddy Simulation (DES). The spheroid pitches about its cantroid from O0 to 30° angle of attack at a dimensionless rate of 0.047 (based on the freestream speed and model length). Flowfleld predictions are evaluated using experimental measurements and also contrasted against predictions of the flows at static angles of attack (a) of 10, 20, and 30°. Flowfleld parameters are the same as in the experiments, the Reynolds number based on freestream velocity and the model length is 4.2 x Id, the boundary layers on the spheroid surface are tripped at z / L = 0.2. Solutions of the compressible Navier-Stokes equations are obtained on unstructured grids, rigidbody motion of the spheroid is accomplished using an Arbitrary Lagrangian Eulerian formulation. Compared to solutions at flxed angle of attack, the flow structure for the pitchup case lags that of the static-a flows. Surface flows for the statia and maneuveringgeometry solutions show marked differences at the conclusion of the pitchup. At 20' angle of attack the pitchup solution does not possegs a secondary separation as in the static-a case. Skin friction predictions exhibit similar variation as the experimental measurements of Wetgel and Simpson 111, though are shifted below the measured values. Predictions of the azimuthal pressure distribution exhibits good agreement with the measurements of Hoang et al. 121. Development of the normal force and pitching moment for the maneuvering geometry also show reasonable agreement with measured values.

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