Abstract
There has been an increasing attention to the effect of hull roughness on ship resistance and powering. In conventional studies, the hull surfaces have been treated as uniform rough surfaces while the real ships' hulls are exposed heterogeneous fouling accumulation. The work described here presents an experimental investigation into the effect of heterogeneous hull roughness on ship resistance. A series of towing tests were conducted using a ship model of the Wigley hull with various hull roughness conditions, including homogeneous conditions (i.e. smooth and full-rough conditions) and heterogeneous conditions (i.e. ¼-bow-rough, ¼-aft-rough, ½-bow-rough and ½-aft-rough conditions). The bow-rough conditions (e.g. ¼-bow-rough and ½-bow-rough) showed larger added resistance than aft-rough conditions (e.g. ¼-aft-rough and ½-aft-rough) with the same wetted surface area of the rough region. This finding suggests that the hull roughness of the forward part of the hull is more significant than the others in terms of the added resistance. Finally, a new method was proposed to predict the added resistance due to the heterogeneous hull roughness based on Granville's similarity law scaling and the predictions were compared with the experimental result.
Highlights
One of the main reasons for the performance degradation of ships is increased hull roughness
There has been extensive research carried out in order to predict the effect of hull roughness on ship resistance and powering, either using the similarity law scaling or Computational Fluid Dynamics (CFD)
A series of towing tests of the Wigley hull model were conducted with different hull conditions including the heterogeneous hull conditions (i. e. 1⁄4-bow-rough, 1⁄4-aft-rough, 1⁄2-bow-rough and 1⁄2-aft-rough conditions) as well as the homogeneous hull conditions
Summary
One of the main reasons for the performance degradation of ships is increased hull roughness. There has been extensive research carried out in order to predict the effect of hull roughness on ship resistance and powering, either using the similarity law scaling or Computational Fluid Dynamics (CFD). The advantages of using the Granville’s method include that it can predict the roughness effect on the skin friction of a flat plate of arbitrary length and speeds, once the roughness function of the surface is known. This flat plate assumption is generally considered as reasonable and it shows good agreement with other high-fidelity methods (Demirel et al, 2017b; Song et al, 2019a) while it requires much less computational cost. Song et al (2020a) validated this method by comparing the predicted result with the experimental data involving a towed ship model with a rough surface
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