Flow structures around different torpedo-like geometries having a hemispherical nose and fins in a uniform flow

The particle image velocimetry method is used to experimentally investigate the flow features around three torpedo-like geometry configurations for four different angles of attack α=0°, 4°, 8°, and 12° at Re = 2 × 104 and Re = 4 × 104 in a uniform flow. These configurations had a hemispherical nose form with three different tail designs: a finless tail, three-finned tail, and four-finned tail. During the experiment, several crucial parameters characterizing the flow field are examined, including the distributions of instantaneous velocity vectors, normalized instantaneous vorticity patterns, time-averaged velocity vectors, streamlines, vorticity contours, streamwise and cross-streamwise velocity components, root mean square of streamwise and cross-streamwise velocity components, Reynolds stress correlations, and turbulent kinetic energy. These flow characteristics illustrate the considerable influence of turbulence on wake dynamics, fluctuations, and coherent rotational structures that are especially pronounced with increasing angles of attack and variations in tail-fin configurations. The critical points in the flow patterns approach closer to the trailing-edge of the body when the Reynolds number is doubled. Moreover, the velocity data obtained from various points in the wake region for four angles of attack were used to determine the dominant vortex shedding frequency (VSF) and the corresponding Strouhal number for all examined torpedo-like geometries and both Reynolds numbers. The integration of fin to the tail models, providing a passive flow control, has been demonstrated to dramatically reduce both the VSF and the intensity of the turbulence quantities in the wake of the torpedo-like geometry at ultra-low Reynolds numbers.