Influence of free-surface on wake flow characteristics of a torpedo-like geometry

A. Kilavuz, T. Durhasan*, M. Ozgoren, F. Sarigiguzel, B. Sahin, L. A. Kavurmacioglu, H. Akilli, E. Sekeroglu, B. Yaniktepe

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

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 languageEnglish
Pages (from-to)1130-1147
Number of pages18
JournalJournal of Marine Science and Technology
Volume27
Issue number3
DOIs
Publication statusPublished - 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

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