Changing the cross-sectional geom- etry of a bow tunnel thruster Effects on the performance of the thruster at slow forward motion using Computa- tional Fluid Dynamics

In this master thesis the flow behavior and the performance of a bow tunnel thruster at slow forward vessel motion is studied using Computational Fluid Dynamics (CFD). In this Definition Study a literature study is made, fundamental theory is explained and a roadmap for the master thesis is developed. At Royal IHC it is noticed that trailing suction hopper dredgers experience a significant decrease in turning ability, using the bow tunnel thrusters, when sailing at speeds of 5 [kts] in comparison to zero forward speed. Dredgers are often operating at those speeds, using the bow tunnel thruster to keep course and therefore often experience this effect in practice. Theory of different fields that can be used to describe the behavior of the flow through the tunnel and the interaction with the ship flow is given. The literature review focus on the parameters that influence the behavior of a bow tunnel thruster at slow forward vessel motion and indicates possible solutions. Based on the literature review a hypothesis is derived that is tested using CFD computation with the commercial solver Numeca FineMarine. The details and planning of those numerical tests are developed in a roadmap. The literature review revealed a potential improvement of the turning ability of a vessel, when the cross-section of the bow tunnel thruster is changed towards a streamlined cross-section. Next to that model tests of Nienhuis using a simplified ship hull (Nienhuis wedge) are available and will be used as validation case for the CFD computations. The roadmap consists of two stages: a validation study of the Nienhuis wedge and a systematic variation of the tunnel cross section using a simplified trailing suction hopper dredger (Hopper wedge). The results of the CFD study are reported in an additional document.