Submarine Motions in Confined Waters INSEAN Technical Report No. 2

This technical report concerns the work elements WE-4.1a and WE-4.1b within the WEAO EUCLID RTP 10.17 project "Submarine Motions in Confined Waters". The theoretical model adopted by INSEAN is described and related assumptions and limits are discussed. The solution algorithm is outlined and the main features of the developed solver are described. The latter involve grid generation, influence of numerical parameters, convergence properties and uncertainty. The CFD code is applied to study the problem of a submarine advancing with constant speed and straight path, in open-water, close-to-bottom and close-to-free surface conditions. The cases analysed are taken from the INSEAN experimental test matrix (see report EUCLID/RTP 10.17/INSEAN/WE-2.3,3.1/TR/1/1) and contain the simulations prescribed by the INSEAN numerical test matrix approved by the Management Group at the third progress meeting. Additional un-propelled simulations have been performed and used to help the physical investigations. The features of the flow around the submarine are described in terms of velocity and pressure fields, and the influence of body geometry and configuration is investigated with and without solid/deformable boundaries. The force and moment coefficients are presented as tables and as graphs and compared with the corresponding INSEAN measurements. The numerical uncertainty and the order of convergence are also reported. Differences with the model tests and numerical properties are discussed and the global loads results are investigated in terms of body configuration and presence of the boundaries. Globally the INSEAN CFD tool proved to be able to properly simulate the flow features around the submarine, to capture correctly the influence of the body and boundary effects and to give valuable predictions of the submarine loads.