Experiments have been carried out in a wind tunnel in order to study the formation of fuselage afterbody vortex flows. The tests were performed on a generic cylindrical body with a slanted base, and the upsweep angle Φ was varied between 24° and 32°. Drag measurements, crossflow 2D Particle Image Velocimetry (PIV) and pressure measurements were the main experimental tools utilized in this investigation. The growth in vortex circulation due to the vorticity roll-up mechanism was seen to slow down significantly towards the trailing-edge. The final strength of the vortices increased with increasing upsweep angle, and was proportional to the mean drag coefficient. The time-averaged vortex was observed to be more axisymmetric, more coherent with reduced meandering, furthermore with a smaller core radius towards the trailing-edge. This tightening of the vortex core in die streamwise direction has not been documented with other external vortex flows in aerodynamics. Proper Orthogonal Decomposition analysis revealed that the helical displacement mode with azimuthal wavenumber m = 1 develops to be the dominant mode towards the trailing-edge, suggesting that the afterbody vortices bear much similarity with the more widely studied wing tip vortices.
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