Abstract

Although the hull of a recently dry-docked large ship is expected to be relatively smooth, surface scanning and experimentation reveal that it can exhibit an “orange-peel” roughness pattern with an equivalent sand-grain roughness height $k_s$ = 0. 101 mm. Using the known $k_s\mathrm{}$ value and integral boundary layer evolution, a recently cleaned and coated full-scale ship was predicted to experience a significant increase in the average coefficient of friction $\mathrm{\%}\mathrm{\Delta }{\overline{C}}_f$ and total hydrodynamic resistance $\mathrm{\%}\mathrm{\Delta }{\overline{R}}_T$ during operation. Here the report also discusses two recently reported empirical estimations that can estimate k_s directly from measured surface topographical parameters, by-passing the need for experiments on replicated surfaces. The empirical estimations are found to have an accuracy of 4.5 − 5 percentage points in $\mathrm{\%}\mathrm{\Delta }{\overline{C}}_f.$

摘要

尽管预计最近干坞的大型船舶的船体相对光滑，但表面扫描和实验表明，它可以表现出具有等效沙粒粗糙度高度的“橘皮”粗糙度图案 ${克}_{秒}$= 0. 101 毫米。使用已知的${克}_{秒}\mathrm{}$ 值和整体边界层演变，预计最近清洁和涂层的全尺寸船舶的平均摩擦系数将显着增加 $\mathrm{\%}\mathrm{\Delta }{\overline{C}}_F$ 和总水动力阻力 $\mathrm{\%}\mathrm{\Delta }{\overline{\mathrm{电阻}}}_{吨}$操作过程中。在这里，报告还讨论了最近报道的两个经验估计，它们可以直接从测量的表面地形参数估计k _s，绕过对复制表面进行实验的需要。发现经验估计的准确度为 4.5 - 5 个百分点$\mathrm{\%}\mathrm{\Delta }{\overline{C}}_F.$