A computational study of shallow-water effects on ship viscous resistance

Double-body viscous flow computations have been made for 4 ships of very different proportions, for model and full scale, each in several water depths. The effect of shallow water on the flow around the hull and the viscous resistance is discussed and compared with existing empirical methods. It is found that the best-known methods, of Schlichting and Lackenby, perform poorly for the cases considered. Millward‟s formula is in better agreement. An alternative form is tentatively proposed, yielding the relative increase of viscous resistance dependent on T/H. Scale effects are considered, and it is indicated that different model-toship extrapolation methods for shallow water tests yield substantially different results. For the cases considered, a form factor method with a water-depth dependent form factor appears to be the right choice, but for T/H > 0.6, using computed scale effects in the extrapolation is the preferred method.