Nextmuse - Deliverable D3.1 Intermediate report on Fluid-Solid coupling for rigid body motions, and solid mechanics modelling

The principal and largest effort in the development of this task is dedicated to coupling of SPH solutions of fluid dynamics with rigid body motion. This topic is of great interest in several engineering application, including naval hydrodynamics problems, and represents a challenging task because the fluid and the structures are strongly coupled. For what concern the development of the coupling algorithm a model was studied by INSEAN and NUIG. The core procedure of the algorithm was designed both for SPH models with boundary particle method (see deliverable D1.1 for details) as well as for the FVPM variant (see deliverable D1.1).The latter was implemented at NUIG in the period M6-M12. This model has been tested on a cylinder constrained with springs in a channel flow for which no free-surface occurs For such a problem experimental data are available in literature. A good accordance between the numerical solver and the experiments was obtained. For what concern the SPH model the coupling algorithm will be implemented by INSEAN during the period M12-M18 in order to deal with free-surface flow interacting with rigid bodies. Specifically the method will be validated with the problem of a freely floating 2D ship section subjected to gravity wave system. Before dealing with the problems of gravity waves interacting with freely floating bodies great care has been given to the study of wave propagation. Indeed, a correct and accurate modeling of gravity waves is a crucial point for such simulations. In order to evaluate the accuracy of the SPH models in reproducing gravity wave propagations, 2D regular waves have been generated through a wave maker (both piston and flap have been considered) and a large number of simulations have been performed for steepness and height-to-depth ratio spreading from deep to shallow water. INSEAN took care of such study starting from the δ-SPH model described in deliverable D1.1. The SPH results have been compared with both experimental and numerical data. In the latter case, a BEM-MEL solver has been used. In fact, such a solver is one of the most appropriate scheme to describe the propagation of gravity waves since it is based on the potential theory. Specifically, we used the BEM-MEL code developed at INSEAN and experimental data performed at the INSEAN tanks. Beyond the test on regular waves, we also performed simulations with wave-packets. This is a quite stiff problem which involves high non-linear phenomena including breaking waves. For such a study, experimental data are available in literature. INSEAN during the period M12-M18 will continue the work simulating the dynamics of freely-moving rigid bodies in regular waves where the coupling algorithm will be implemented and validated through comparison with experimental data. Following the purpose given at TASK 3.1, a bibliography research has been performed in order to find experiments suitable for testing the SPH model in dealing with interactions between fluids and rigid bodies. Unfortunately this research did not provide sufficient detailed experimental data. Therefore the INSEAN database was examined and an experimental campaign regarding this topic was found. This campaign consisted in the analysis of a ship model excited by regular beam waves. Firstly the ship model was constrained and exiting forces, wave elevation and velocity field through PIV technique were measured. Then the same experiments were repeated leaving the ship model free to move in heave and roll motion. In this case the ship motion evolution was recorded. The experimental results are discussed in section 1.4 of the present report