Report on hybrid RANS/BEM model interfaces

A major objective of the STREAMLINE project is the development of advanced CFD tools which can be used in this design studies. While full RANS computations for rotating grids are possible, they are still too much time consuming for optimization studies. Hybrid RANS/BEM models have been applied in recent years and have proved themselves to be a cost-effective simulation approach. Complex configurations of rotating propellers and static parts can be investigated by simulating the moving part with inviscid flow methods while the non-rotating part is studied with viscous flow solvers. The aim of the work described in the deliverable is to develop efficient RANS/BEM coupling methods and to further improve existing solutions. The deliverable describes the RANS and BEM codes used by HSVA, INSEAN and CNRS and the methodology to couple them into a joint solution procedure. While the work of HSVA is focused on the coupling interface for the steady and fully transient flow simulation on unstructured grids, INSEAN worked on extending the RANS/BEM interface for the analysis of the unsteady interaction between the propeller and the background flow where the latter is analysed via an unsteady RANS model for structured overlapping grids. CNRS implemented the RANS/BEM coupling for their in-house code ISIS. The implementations of the methods are evaluated using a range of test cases from the open water test to a transient numerical propulsion test.