Modified near-wakes of axisymmetric cylinders with slanted base

Near-wakes of axisymmetric cylinders with slanted base were investigated in wind tunnel experiments for an upsweep angle of 28°. Effects of splitter-plate, cavity, and flaps on the afterbody vortices and separated flow were studied by means of surface pressure and Particle Image Velocimetry measurements. The splitter plate causes more diffused afterbody vortices due to the turbulence ingestion from the separation region. When the slanted base is replaced with a deep cavity, there is weaker roll-up of vorticity due to the lack of streamwise flow and a solid surface. Varying the splitter plate length in the range tested did not have significant influence on the flowfield, apart from affecting the strength of the splitter-plate vortex. With the splitter plate and cavity, unsteadiness is dominated by the flow separation region, as opposed to the afterbody vortices in the baseline case. A pair of vertical flaps attached to the side-edges of the splitter plate can reduce the unsteadiness at the measurement plane immediately downstream of the splitter plate.