Retrofitting integrated wedge-flap for improvement of resistance of high-speed displacement vessel

This paper reports the design for retrofitting of a high-speed displacement vessel for improving the speed because of deficiency in installed power for a 250-passenger ferry craft. The methodology is based on the evaluation of the integrated wedge-flap at the stern. High-speed displacement vessels operate at a steep region of the speed–resistance curve, and therefore, conservation of energy by drag reduction plays a major role in cost-effective operation of the vessel. The performance of the integrated wedge-flap at the stern is examined to recommend an appropriate design instead of an intuitive approach for the same. In a high-speed displacement vessel, various factors that lead to energy consumption are increased drag due to adverse dynamic trim, bow waves and unfavourable flow patterns in the stern region. The above-mentioned factors may also increase the wetted surface area of the hull, thereby increasing the overall drag and additional demand of power. The integrated wedge-flap is a combination of two appendages, namely wedge and stern flaps. The results from the study demonstrate that the integrated wedge-flap modifies the stern waves to flatter form, with reduction of the flow velocity below, resulting in increased dynamic pressure, improved trim and lift force with corresponding drag reduction. The numerical simulation of drag using commercial RANS code (Star-CCM+) shows the local influence of the energy saving appendage reinforced by validation with experiments. The study establishes a systematic method of introduction of the appendage to achieve significant drag reduction for the high-speed displacement hull form.