Experimental investigation on the wake structure of teardrop-shape slender body.

Flows around the different head length diameter ratio (L E / D = 0.5, 1, and 2, where L E and D refer to the head length and mid-body diameter, respectively) of the teardrop-shaped slender body of revolution with a constant Reynolds number (Re D = 4.1 × 103) were studied using particle image velocimetry. The aim was to explore how the flow geometry affects the hydrodynamic characteristics. Through the time-averaged statistical characteristics of the wall and wake of slender body determined the dynamics performance. Using the power spectral density (PSD) function, proper orthogonal decomposition (POD), and the phase-averaged method, we explored the wake vortex structure, distribution, and strength. The wake of the teardrop-shaped slender body obeys the classical −2/3 decay law at 6 < x / D < 9 and evolves into a self-similar manner. The PSD and POD analyses imply that the POD Modes 1 and 2 are closely related to the large-scale vortex shedding, and the important frequencies of the POD Modes 1 and 2 coincide with the vortex shedding frequency. At the reconstructed flow field of the POD Modes 1 and 2, the analysis of the phase average indicates that the evolution process of a large-scale vortex should involve a periodic three-dimensional helical vortex structure. • We discuss the wake decay law and self-similar manner of the teardrop-shape slender body. • We introduce the evolution process of large-scale vortex of wake is a periodic three-dimensional helical vortex structure. • We identify a head length diameter ratio of teardrop-shape of slender body with good hydrodynamic properties. [ABSTRACT FROM AUTHOR]