Drag Optimisation of Ship Shapes (DROPSS)
International shipping is responsible for the transport of around 90% of the global trade. The dominant role of shipping is attributable to the low fuel consumption per tonne*km of transported cargo. However, the mere magnitude of around 45-50 thousand operating merchant vessels puts environmental and economic aspects of shipping into the focus of many optimisation efforts. The seaborne pollution as well as approximately 50% of the direct operating costs for shipping are related to fuel consumption, which in turn is governed by the resistance of the vessel. The latter is largely controlled (75% at a guess) by steady hydrodynamic contributions, i.e. the wave drag in calm water and the friction drag along the wetted surface. Means to reduce these drag contributions, even by a few per mille, are highly appreciated from commercial and environmental perspectives.The present proposal is concerned with the development of a computational framework for the hydrodynamic shape optimisation of free-floating ship hulls exposed to immiscible two-phase flows. Attention is confined to gradient-based adjoint methods in a parameter-free optimisation environment. Emphasis is given to wave and friction drag at Froude- and Reynolds-numbers of practical interest. Specific interest refers to (i) accurate and robust adjoint two-phase flow models including (ii) the inclusion of dynamic floatation aspects, (iii) a novel reduced adjoint turbulence treatment and (iv) an improved CAD-free shape parameterization for partially wetted shapes subjected to manufacturing constraints. Applications will focus on a frequently investigated container vessel and a blunt offshore supply vessel. Results will be transferable to the optimisation of other marine engineering applications, e.g. the design of near-shore operating renewable energy devices harvesting ocean waves in the surge zone close to a free surface.