Analysis of Attack Angle Effect on Flow Characteristics Around Torpedo-Like Geometry Placed Near the Free-Surface via CFD

Authors : Muammer ÖZGÖREN, Alpaslan KILAVUZ, Tahir DURHASAN, Beşir ŞAHİN, Levent KAVURMACIOĞLU, Hüseyin AKILLI, Fuad SARIĞIGÜZEL

Pages : 1579-1592

Doi:10.2339/politeknik.675632

View : 37 | Download : 13

Publication Date : 2021-12-01

Article Type : Research Paper

Abstract :In this study, the flow characteristics of torpedo-like geometry placed near the free-surface at various angles of attack were investigated numerically. The study was carried out at the Reynolds number of Re=4x104 between immersion ratios of 0.75≤h/D≤3.5 and angles of attack α=0°,4°, 8°, and 12°. Large Eddy Simulation insert ignore into journalissuearticles values(LES); turbulence model was used along with the Volume of Fluid insert ignore into journalissuearticles values(VOF); multiphase model to investigate the effects of free-surface. Wake region had an asymmetrical structure near the free-surface as a result of the interaction. A jet-like flow region was observed between the geometry and the free-surface at lower immersion ratios due to the restriction of the flow area. This flow region had a downward movement towards the lower pressure wake region. The drag coefficient, CD, values were increased with the decrease of immersion ratio. At angles of attack α=8° and 12°, the flow separation occurring near the nose caused an additional restriction in the flow area and directed the jet-like flow toward free-surface. Variation of Froude numbers insert ignore into journalissuearticles values(Fr); depending on the immersion ratio is examined, and it is found that Fr number and corresponding drag coefficient have higher values for the lower immersion ratio. The free-surface effect was found negligible at h/D≥2.5 for all cases.
Keywords : Computational fluid dynamics, drag coefficient, free surface, LES, torpedo like geometry

ORIGINAL ARTICLE URL