Ship Drag Reduction

Drag reduction on fast moving ocean vehicles is achieved by reducing the wet surface area and by controlling the boundary layer over the wetted part of the ship hull. The developed concept of wet area reduction is to use underwater wings. Friction reduction over the wings  is achieved by means of partial cavitation hydrofoil design and polymer injection into the boundary layer on the  pressure side of the wings. For a ship speed of about 75 knots, the cavity will cover about 70-75% of the suction side. The combined employment of the new design and of drag-free partial cavities will provide drag reduction of up to 74% for the wings, which are the main elements of hydrofoil ships. Because of the necessity to maintain low drag of partially cavitating hydrofoils under eventual sea impact, the fundamental basis of an active flow control system for partially cavitating wing is developed. Preliminary estimations showed that such a system allows a drag reduction of about 65% even in a wavy sea. Polymer injection was selected as the most promising modern method of friction reduction. For the developed hydrofoil, it is possible to reduce a substantial part of the pressure side friction. Therefore as a result of advanced design including the employment of drag-free cavities and polymer injection, the total wing drag reduction will be up to 80%.

Fast ship hydrofoil

Fast sea-lift ship (design concept)