This Master Thesis discusses a ships propeller wash and velocities that this wash inflicts on the seabed. As increased maritime traffic is expected in the Gulf of Koper, the impact of ships navigating on the seabed is also expected to increase. The propeller wash can cause the resuspension and transport of sediments. A review of literature has been made and a list of equations describing a turbulent jet of propeller has been put together. For the comparison of these equations, a new model in MATLAB computing environment has been developed, which enables the calculation of velocity field for any bathymetry or horizontal plane, several types of ships and any manoeuvre during navigation. The calculated velocity field could be used as an input for the sedimentation module of PCFLOW3D model. The calculations show that different equations give significantly different results. The differences of nearly 100% are possible at efflux velocity calculation. Different equations for the prediction of maximum velocity decay give jet reaches from only some 10 meters to some kilometres. An investigation of two methods that account for rudder effects in the propeller wash has been done, from which only one has been proved to be useable. The three tested methods for the correction of efflux velocity due to advancing of the ship have given comparable results. The analysis of three test manoeuvres in the Gulf of Koper has also been carried out. The calculated velocity fields are comparable with the results from previously performed studies.
|
