Optimisation of Resistance and Towed Stability of an Offshore Going Barge With CFD

For the transport of large structures over sea, offshore going barges are one of the preferred means of transportation. The resistance and towed stability of these vessels are of prime importance with respect to the economic feasibility of transport. To ensure acceptable towed stability behaviour, side skegs are generally placed under the aft ship of the barge. However, these skegs give additional resistance and thus undesired fuel consumption.
SMIT and MARIN joined forces with the intention of designing a new ocean going barge with sufficient towed stability and superior resistance characteristics compared to the already low drag Giant 4 barge. The Giant 4, for which favourable tow characteristics were observed during its service, was used as a reference vessel. The first step was to modify the hull form in order to fulfil SMIT's design requirements. Subsequently, a detailed CFD study into the flow around the barge and the size, shape and positioning of the side skegs was performed leading to a significant resistance reduction. However, this reduction in resistance led to a degradation of the towed stability of the vessel, which was compensated for by adding a centreline skeg. The final design has a 14% reduction in resistance compared to the existing barge, with comparable towed stability.
A model testing program was performed in order to validate the CFD computations. The agreement between the CFD and experimental results was found to be very good, demonstrating that CFD tools can be used to optimise the resistance and towed stability of barges.