This article describes the evaluation of the wave profile of submarine at surface condition and deck flooding which occurred by the wave making pattern at the bow. Movement of ships and submarines on the free surface of calm water creates the surface wave. Because of the difference in the bow shape and freeboard height, the wave making system in ships and submarines is different. Rounded or elliptical bow shape of submarines generates a high bow wave which causes deck and bow wetness. This is because of the fact that in submarines, this situation arises a small freeboard. In submarines, Deck wetness (because of deck flooding) is a very important subject that has some remarkable consequences, such as increase in resistance and added weigh. The focus of this article is on the added frictional resistance in the deck wetness condition. The bow wave profile, deck wetness and added resistance are studied in several Froude numbers by computational fluid dynamics method. This analysis is performed for a bare hull model at two different drafts by Flow Vision (V.2.3) software based on computational fluid dynamics method and solving the Reynolds-averaged Navier-Stokes equations.

This article discusses the optimum hydrodynamic shape of the submarine stern based on the minimum resistance. Submarines consist of two major categories of hydrodynamic shape: the teardrop shape and the cylindrical middle-body shape. Due to the parallel middle-body shape in most of the naval submarines, those with cylindrical middle-body are studied here. The bare hull has three main parts: bow, cylinder and stern. This article proposes an optimum stern shape by the computational fluid dynamics method via Flow Vision software. In the hydrodynamic design point of view, the major parameters of the stern included the wake field (variation in fluid velocity) and resistance. The focus of this article is on the resistance at fully submerged mode without any regard for free surface effects. First, all the available equations for the stern shape of submarine are presented. Second, a computational fluid dynamics analysis has been performed according to the shape equations. For all the status, the following parameters are assumed to be constant: velocity, dimensions of domain, diameter, bow shape and total length (bow, middle and stern length).

This paper evaluates the effective depth of waves on the submarine at the depth of water. At the depth called the "Wave Base" which equals to λ/2 the wave effects become so small that motions are negligible. This paper aimed to recommend a minimum safe depth for calm and stable motions of a submarine. This paper concludes the depth of 0.1λ could be recommended as an operational safe and approximately calm depth for submarines. For this study, a torpedo shaped submersible is analyzed in some depths accompanying by regular surface wave. By increasing the depth, the reduction of submarine motions is evaluated. The results of this research can be used for AUVs, research submersibles and naval submarines. This analysis is performed by CFD tools of Flow-3D (V.10) software based on solving the RANS equations and VOF method.

Abstract:The research intends to evaluate the variation in the resistance and the lift of a torpedo shaped AUV brought about by the wall effect inside the pipe as it moves out of the axis inside a water pipeline. Movement of an AUV at the axis of a pipe causes minimum resistance and lift forces, but when the AUV moves at a position parallel with the axis of the pipe (out of axis of the pipe), the hydrodynamic forces especially the lift force changes. The AUV must be able to move a float inside the pipe and perform non-contact inspection. In water pipes having limited diameters, there is the wall effect. The added resistance and the lift have to be calculated accurately, which is a necessary requirement for the determination of the vehicle speed, power demand, control, range and duration of the operation. According to the findings of this paper, when moving at the center of pipe the ratio of AUV diameter to pipe diameter is equal to 12. This value can be considered for the determination of "the critical pipe diameter" which gives zero resistance. The results of this study can be applied for torpedo movement inside the torpedo tube. The analysis is performed by the Flow Vision (V.2.3) software based on the CFD method and solving the RANS equations.Key world: AUV, pipeline, hydrodynamic, resistance, lift, wall effect.

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