احمدرضا کهنسال

Transverse Steps as a chine at the bottom of planing hull created. the interaction fluid with this step one separated current exist at bottom of vessel that cause reducing wetted surface of vessel and therefore reduces the friction drag. The drag reduction in reducing power requirement and fuel consumption are effective. Also stepping generates additional lift at the aft of vessel. In this study, we investigated the effect of single-stepping across the calm water to numerical methods and numerical analysis and validation testing, the effect of two transverse step is numerically analyzed. This analysis software for two dimensional Ansys CFX V15 are done. In the first part of numerical analysis as a plate Planning in fixed trim and draft are model in calm water. The frictional drag and lift floating extracted, then vessel with single - transverse step model and numerical results are compared. Also, variations in the amount of frictional drag and length of wetted surface during the step of moving the longitudinal position and the change in step height have been studied. These results were then compared with the numerical results. In the second part, numerical analysis, another step in the distance from the first step at the aft of vessel was added in geometry of vessel. For this vessel the effects of second step of changing the longitudinal position and height of the steps is studied. Finally, the numerical results obtained from the effects of the one step and two step model were compared.