Application of Control Volume Energy Balance for Analysing Propeller-Hull Interaction in Presence of Free-surface

Paper in proceedings, 2019

Reynolds-Transport Theorem can be employed for analysing the conservation of energy equation over a control volume. Through this approach we can decompose the propeller delivered power into mechanical and thermal energy components. This approach not only enables us to qualitatively describe the flow but also makes it possible to quantify different energy flux components and understand the energy loss mechanisms within the studied system. Employing this method, the effect of free-surface on propeller-hull interaction is studied for an axisymmetric body in the vicinity of free-surface relative to a deeply submerged body. The required flow quantities for the control volume analysis are obtained from a Reynolds- Averaged Navier-Stokes approach together with a Volume-of-Fluid method for capturing the free-surface. The mechanical and thermal energy flux components have been computed for control volumes of different sizes, even including the free-surface. These results deviate less than 0.5% from the propeller delivered power which verifies the applicability of the method for further analysis of the interaction effects. The self-propelled hull is studied in two different depths and thus the propeller loadings and efficiencies are different. The analysis of energy flux components quantitatively explains the reasons for the differences.