Abstract
In the present work, the flow topologies of a generalized torpedo-like geometry were investigated experimentally via Particle Image Velocimetry (PIV) and dye visualization. The study was conducted at length based on the Reynolds number of Re = 20 × 103 and 40 × 103. The torpedo-like geometry was positioned at ratios of immersion between 0.50 ≤ h/D ≤ 3.50 to investigate the free-surface effect on the present results, comparatively. PIV measurements provided ensemble-averaged velocity fluctuations, turbulent kinetic energy and Reynolds stress correlation with spectral analysis of the vortex-shedding mechanism. It is observed that different vortex shedding mechanism occurs depending on the immersion ratio. At h/D = 0.5, wake flow is characterized by the lower shear layer while upper shear layer dominates it at h/D = 0.75 and 1.00. The influence of the free-surface on flow characteristics is found to be negligible at h/D > 2.00 for both Reynolds numbers. Alternating vortex shedding occurs and the wake regions at h/D = 3.5 became nearly symmetrical. The size of the wake zone is moved closer to the stern of the torpedo-like geometry at Re = 40 × 103 and causes a smaller recirculating region. Spectral analysis of the streamwise velocity revealed a decreasing trend of Strouhal number with increasing immersion ratios. The changing of the Strouhal number showed a significant increase at h/D = 0.75 for Re = 20 × 103 an ever-decreasing trend for Re = 40 × 103.
Original language | English |
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Pages (from-to) | 1130-1147 |
Number of pages | 18 |
Journal | Journal of Marine Science and Technology |
Volume | 27 |
Issue number | 3 |
DOIs | |
Publication status | Published - Sept 2022 |
Bibliographical note
Publisher Copyright:© 2022, The Japan Society of Naval Architects and Ocean Engineers (JASNAOE).
Keywords
- AUV
- Free-surface
- PIV
- Torpedo-like geometry
- Turbulent flow