Numerical Investigation of the Effect of Changes in the Height of the Transverse Step at the Zero-step Angle on the Hydrodynamic Performance of the Single Body Planning Vessel

Most of the researches on the effect of the step on the hydrodynamics of the stepped vessels have considered uniform step height across the width. This gap prompted the researchers to investigate the effect of the variable height of the step in the width on the hydrodynamic performance of the planing vessels. For this purpose, three Frisma models have been selected, including one model without steps and two models with steps that have variable step height in width. The basis for choosing the triangular change is the uniform change of the height of the step in the width. Comparing the results of the float without steps with other vessels with steps has led to obtaining useful information about the hydrodynamic characteristics of the variable height of the step in width compared to the fixed height of the vessels. In this research, two models with transverse steps and a simple vessel (without steps) were compared in terms of hydrodynamic characteristics such as trim angle value, drag-to-lift ratio, wet surface value and total resistance force, and the most optimal model was determined. Is. The results show that the step with fixed height reduces the resistance force about 30 percent and has a greater drag reduction than the step with variable height. But in the step with variable height, the trim is less than the step with the same height. In the designs, attention should be paid to both.