Added mass analysis of submersible using computational fluid dynamics

Abstract

An estimation of the resistance acting on a manned submersible can be performed using computational fluid dynamics (CFD). The resistance force acting on a vehicle can be steady state or transient state drag. Steady state drag comes when a vehicle moves at a constant velocity but drag value increases or decreases when the vehicle accelerates or decelerates. Transient state drag acts on a vehicle when velocity changes. The addition or reduction in drag value is due to the added mass. This paper discusses two CFD approaches to calculate longitudinal added mass. The second CFD method is preferred due to the inaccuracy and assumptions involved in the first method. The preferred CFD method can be used to obtain the added mass for both standard shapes, as well as for complicated geometries like manned submersibles. The drag and added mass of the ellipsoid are calculated using CFD and compared with analytical and experimental results for validation. Additionally, an acceleration sensitivity study indicates that added mass is independent of acceleration. CFD methods proposed here are simple and time-efficient. By using this method, a submersible’s added mass can be calculated without employing expensive experimental methods or other CFD methods. Highlights A vehicle’s steady-state drag develops when moving at constant velocity, but the amount of drag increases or decreases when accelerating or decelerating The CFD method can be used to obtain the added mass of more complicated geometries like manned submersibles and standard shapes like spheres and cylinders An acceleration sensitivity study indicates that added mass is independent of acceleration