Experimental investigation of the effect of a step and wedge on the performance of a high-speed craft in calm water and statistical analysis of its seakeeping in irregular waves

Abstract

Analysis of the hydrodynamic performance of a high-speed craft in calm water and seakeeping in irregular waves have attracted the attention of many researchers. In the current paper, experimental tests have been conducted on three mono-hull high-speed crafts in calm water and in the presence of irregular waves. The overall geometry of the tested vessels is the same with a length of 2.64 m and a beam of 0.551 m. They only differ in the presence of a wedge or transverse step. These vessels are stepped vessels and bare vessels with no appendage. Different parameters of trim, rise-up, and resistance are measured in calm water. In addition, heave and pitch motions, fore acceleration, and the center of gravity are extracted as time series. The irregular wave, which is modeled in sea force of 3, has a height of 12 cm and a peak to peak time period of 1.66 s. The tests are conducted for five different speeds ranging from 4 m/s to 8 m/s (equivalent of longitudinal Froude numbers between 0.857 and 1.71). Comprehensive comparisons have been presented between the stepped, wedged, and bare hulls. Based on the obtained results, it is concluded that the stepped vessel has less resistance in calm water compared to the two other models. The trim and resistance of the stepped model are 20% and 3% less than those of the models with no appendage, respectively. In terms of stability, the bare hull is longitudinally unstable at 8 m/s speed. However, the other two models are stable at this speed. On the other hand, the wedge mounted vessel exhibits less motion and acceleration than the other two models in irregular waves. Furthermore, the bow acceleration of the stepped and wedged models is 9% and 18% lower than that of the model with no appendage, respectively.