Experimental investigation of free-surface effects on flow characteristics of a torpedo-like geometry having a cambered nose. (1st June 2022)

• Record Type: Journal Article
• Authors: Sarigiguzel, F.; Kilavuz, A.; Ozgoren, M.; Durhasan, T.; Sahin, B.; Kavurmacioglu, L.A.; Akilli, H.; Sekeroglu, E.; Yaniktepe, B.
• Is Part Of: Ocean engineering. Volume 253(2022)
• Publication Date: 2022-06-01
• Subjects: Free-surface -- PIV -- Torpedo-like geometry -- Turbulent flow -- Vorticity; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2022.111174
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: In this study, the free-surface effect in the wake region of a torpedo-like geometry having a cambered nose was investigated experimentally via Particle Image Velocimetry (PIV) and dye flow visualization methods. The Reynolds number was taken as R e = 2 × 10 4 and 4 × 10 4 while keeping the angle of attack ( α =0 ° ). The torpedo-like geometry is submerged at various positions from the free-surface in the range of 0.50 ≤ h / D ≤3.50 in which (h) is the distance from the water free-surface to the central plane of the geometry, and D is the diameter of the midsection of the torpedo-like geometry. The effect of the free-surface of water on the flow properties is also measured and presented comparatively in terms of normalized contours of instantaneous vorticity, time-averaged streamwise velocity, vorticity contours, Reynolds stress correlation, turbulent kinetic energy, velocity fluctuations in streamwise and cross-streamwise, vortex shedding frequency, spectral density distribution as well as pointwise variation. It is observed that the flow structures become asymmetric when the body is located near the free-surface for the submersion ratio of h / D ≤1.0. With the largest submersion ratio of h / D = 3.50, the flow characteristics are almost identical and symmetrical on both sides of the geometry. Highlights: A cambered nose of a torpedo-like geometry affects the flow separation and reattachment intensively. Depending on the immersion ratio, the free-surface has a significant impact on the vortex shedding frequency due to surface wave deformation. Spectral analysis of flow field using PIV data for free-surface flow condition was performed. Asymmetrical chaotic flow structures occur in the wake due to the free-surface effect. Asymmetrical wake distributions diminish when the submersion ratio increases beyond h/D ≥ 1.5.