Correlation of frictional drag and roughness length scale for transitionally and fully rough turbulent boundary layers

Unal U. O.

OCEAN ENGINEERING, vol.107, pp.283-298, 2015 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 107
  • Publication Date: 2015
  • Doi Number: 10.1016/j.oceaneng.2015.07.048
  • Journal Name: OCEAN ENGINEERING
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.283-298
  • Keywords: Turbulent boundary layer, Roughness effect, Roughness function correlation, Roughness length scale, Marine antifoulings, ZERO-PRESSURE-GRADIENT, FREE-STREAM TURBULENCE, ANTIFOULING COATINGS, MARINE ANTIFOULINGS, SURFACE-ROUGHNESS, REYNOLDS-NUMBER, WALL, RESISTANCE, SMOOTH, FLOW
  • Istanbul Technical University Affiliated: No

Abstract

This study investigates zero-pressure-gradient turbulent boundary layers for several rough surfaces in the transitionally rough and fully rough flow regimes. The tested surfaces include, but are not limited to marine antifoulings as irregularly rough engineering surfaces. The boundary layer profiles were measured by using a two-dimensional Laser Doppler Velocimetry system. The coatings were applied with different procedures to simulate the effect of different application types. An attempt was made to find a new roughness length scale which provides a good correlation to represent the roughness functions for both transitionally and fully rough flow regimes. Surface roughness measurements with a laser profilometer device were carried out to determine several roughness parameters to be used in the calculation of the roughness length scale. Different roughness calculation methods, with varying low-pass filter window lengths and sampling lengths, were applied to determine their effect on the roughness parameters and hence the roughness function correlations.