This study focuses on water-structure interaction of submerged floating tube in homogeneous and stratified flows, as well as gravity current development. The latter was done in order to set up and validate numerical model that treats water stratification properly and in a computationally efficient manner. First part of the study is dedicated to gravity current development. Grid convergence study was performed for simulation of two-dimensional gravity current, which showed that optimal cell sizes for the problem in question are 5 mm and 2.5 mm. In addition, Large-Eddy Simulation (LES) model of turbulence was tested, and its performance in simulation was compared to performance of simulation without any turbulence modelling. It was established that the latter represents gravity current development in two dimensions more accurately. After that, gravity current development in three dimensions was performed with LES modelling of turbulence and without any turbulence model. Both simulations were in good agreement with results of physical experiments, therefore LES model is a preferable choice as it is less computationally demanding. In second part of the project, rigidly fixed horizontal cylinder in flow was considered in order to investigate in-line forces, acting upon the cylinder. At first, model with homogeneous flow was set up and validated. It was established that two-dimensional model with cell size of 2.5 mm and CFL criterion of 0.3 is a good choice in terms of balance between accuracy and computational efficiency. After that, system of two cylinders with varying distance between them was tested. It was established that in-line forces for both cylinders are affected, with influence on the second cylinder being more stark. Third part of the study is dedicated to horizontal cylinder in stratified flow. Parameters of produced internal waves were in agreement with results of physical experiments.

The submerged floating crossing (SFC) considered in this study has demonstrated significant sustainability based on provided assumptions. the SFC has appeared to be a sheltered and sound idea appropriate to satisfy its expected capacities and to tackle given environmental conditions. The structure of the proposed SFC is intended to withstand all functional and environmental loads. The results of worst-case scenarios showed the base SFC design have a sufficient robustness to withstand the presumed significant loads. Some major uncertainties were faced throughout the study, which are manageable by means of modern technologies in civil engineering or some organizational arrangements.