Evaluation of RANS turbulence models for the hydrodynamic analysis of an axisymmetric streamlined body with special consideration of the velocity distribution in the stern region

Sammanfattning: This is a master’s thesis provided by the Swedish Defence Research Agency FOI and is written for the Center for Naval Architecture at the Royal Institute of Technology KTH. The objective is to perform a systematic simulation campaign of the flow around an axisymmetric streamlined body in order to evaluate several RANS-based turbulence models implemented in the open source CFD software package OpenFOAM. Of most interest is the low velocity zone at the stern and the wake behind the body. The results are compared with experimental flow measurements and with data obtained by LES, in order to evaluate how accurately the flow is predicted by each turbulence model. The study leads to method recommendations for this type of flows. Simulation results for two different bodies are also compared in order to investigate how the different shapes affect the flow. Also included is an overview of the turbulence modeling theory behind the RANS-methods which are employed. The results demonstrate that the turbulence models k−!,RNGk−!,k−"andk−"SST are suitable for simulation of this class of flows and provide a good prediction of the mean flow around and behind the body.