Experimental investigation of free-surface effects on flow characteristics of a torpedo-like geometry having a cambered nose


Sarigiguzel F., Kilavuz A., Ozgoren M., Durhasan T., Sahin B., Kavurmacioglu L. A. , ...More

OCEAN ENGINEERING, vol.253, 2022 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 253
  • Publication Date: 2022
  • Doi Number: 10.1016/j.oceaneng.2022.111174
  • Title of Journal : OCEAN ENGINEERING
  • Keywords: Free-surface, PIV, Torpedo-like geometry, Turbulent flow, Vorticity, UNDERWATER VEHICLE, HYDRODYNAMIC CHARACTERISTICS, CIRCULAR-CYLINDER, OPTIMIZATION, DOWNSTREAM, SUBMARINE, WAKE

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 Re = 2 x 10(4) and 4 x 10(4) while keeping the angle of attack (alpha = 0 degrees). 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.