development of a computational fluid dynamic numerical model for the hydrodynamic forces evaluation on subsea structures.

The aim of this master thesis is to simulate, in a multiphase environment (air and water), a free surface wave by making use of the computational fluid dynamics software “OpenFoam” and evaluate the hydrodynamic forces and physical parameters acting on subsea structures. It will be discussed how the hydrodynamic load and other physical parameters vary, according to water depth, when the action of waves and current act together and impact structures of different cross-sections and geometry that lie on the seabed. A comparison between the obtained software results and the analytical solutions will be presented to assess the reliability of “OpenFoam” and the model created for such a problem, trying to give an explanation of the fluid dynamics around the elements when running the simulations. In particular, starting from the multiphase solver “InterFoam”, will be shown how the “wave” tutorial case, available in “OpenFoam V5.0”, has been modified and adapted in order to implement objects on the seabed and eventually determine the hydrodynamic load on submerged structures. For the implemented elements, it will be examined the horizontal and the lift force, trying to verify and validate the model, making a comparison between the theoretical hydrodynamic load, available from the literature and the model post-processed outcomes, extrapolated by OpenFoam object functions. The evaluation of the force coefficients (Drag, Lift, Added Mass) will be also made on the same structures to see which level of influence certain parameters have to respect with others. It will also be presented the Morison’s theory for the evaluation of waves induced load that represents not only the theoretical load with which the model results have been compared to testify the project but it also plays the key role concept of all the following aspects.