The effect of flow stratification on ship performance: a numerical study

If a layer of low-density water settles on top of higher density water, such as fresh water melting from a glacier and settling on top of colder seawater, a body of water can stratify into stable, distinct layers. A vessel advancing in such a stratified fluid can generate internal waves between these layers. The generation of internal waves requires energy and thus increases the resistance experienced by the vessel, a phenomenon known as the dead water effect which can result in a severe reduction in speed and loss of steering power. This study uses Computational Fluid Dynamics (CFD) to investigate the increase in ship resistance caused by the dead water effect. The results show that the presence of a stratified flow can increase total resistance approximately sixfold in extreme conditions. At standard operating conditions, total resistance may increase by approximately 6% as a result of flow stratification.