Investigation of the capability of RANSE CFD for propeller calculation in practical use

Abstract

Nowadays, Reynolds-averaged Navier–Stokes equations (RANSE) is a viable approach to effectively analyze the performance of ships on a large range of different operating conditions. In DNVGL - Futureship Potsdam, by using commercial full RANSE code ISIS - CFD (integrated in Numeca Fine/Marine software), a high degree of accuracy and relatively short computation times can be achieved for pure resistance calculations. However, propulsion computations - taking into account interaction of a working propeller and the hull - are still subjected to large restrictions. Currently, they are using the simple propeller model (the method called: body force approach) to predict the performance of a hull in self-propulsion condition. It provides capable to assess the effects of the propeller on the hull, while maintaining a low computational effort. However, the propeller thrust, torque and relative rotative efficiency are not accessible. It influences on the total power consumption of a vessel in a certain operation conditions. For that reason, the main work of this thesis is to investigate the capability of different propeller modeling approaches in RANSE CFD for practical application or daily using. Therefore, the balance between the computational time and level of accuracy need to be taken into account. The ISIS - CFD code - the “daily use” code in DNVGL Potsdam - is used. Two steps need to be included in the investigation as follows: - Setup of a simulation with rotating propeller for an open water test and then evaluation of the results. Some methods are available to do open water test; therefore this step also include the selection of most efficient method. Besides, different turbulence model are also tested. - Setup of an integrated run with fully rotating propeller behind a ship for a self-propulsion test and evaluation of the results (comparing with experiment data, assessment of the feasibility and practical application). At first, the simulation is carried out for a ship without rudder; then a dummy rudder is added to the hull form to perform simulation and evaluate the influence of rudder to the result.