Solution and domain decomposition model for marine hydrodynamics: rans and potential flow coupling

This paper presents a CFD decomposition model for free surface, viscous, in- compressible flows related to marine hydrodynamics. The solution decomposition is based on Spectral Wave Explicit Navier Stokes Equations (SWENSE), where the primitive vari- ables are written as the combination of incident and diffracted fields. This allows efficient coupling of the discretised Navier–Stokes free surface flow equations with arbitrary poten- tial flow theories. The domain decomposition is achieved with implicit relaxation zones in order to prevent undesirable wave reflection in unbounded domains. Interface captur- ing is obtained with implicitly redistanced Level Set (LS) method derived from Phase Field equation. This approach removes the need to redistance the LS field using conven- tional redistancing procedures and reduces mass conservation issues fundamental to the LS method. The numerical model is based on a polyhedral, second-order accurate, col- located finite volume method (FVM). The coupling of primitive variables is obtained via segregated solution algorithm based on SIMPLE and PISO. The model is implemented in OpenFOAM. The verification of the model is performed by a number of two–dimensional (2–D) test cases. The reflection analysis is carried out by changing the relaxation zone length. Mass conservation and preservation of the signed distance LS function is demon- strated with a simulation lasting 50 incident wave periods. A long domain simulation is also carried out to show that the damping of the wave does not occur. Finally, a wave steepness study has been carried out by changing wave height while the wave period was kept fixed. Three–dimensional (3–D) test cases regarding higher order forces on circular cylinder have also been carried out. However, the results will be presented in future work

Development of a CFD Solver for Primary Diesel Jet Atomization in FOAM-Extend

Ongoing development of a CFD framework for the simulation of primary atomization of a high pressure diesel jet is presented in this work. The numerical model is based on a second order accurate, polyhedral Finite Volume (FV) method implemented in foam-extend-4.1, a community driven fork of the OpenFOAM software. A geometric Volume-of-Fluid (VOF) method isoAdvector is used for interface advection, while the Ghost Fluid Method (GFM) is used to handle the discontinuity of the pressure and the pressure gradient at the interface between the two phases: n-dodecane and air in the combustion chamber. In order to obtain highly resolved interface while minimizing computational time, an Adaptive Grid Refinement (AGR) strategy for arbitrary polyhedral cells is employed in order to refine the parts of the grid near the interface. Dynamic Load Balancing (DLB) is used in order to preserve parallel efficiency during AGR. The combination of isoAdvector-GFM-AGR-DLB presents a unique framework for diesel jet atomization. The developed numerical framework is preliminarily tested on the Engine Combustion Network (ECN) Spray D geometry and conditions. The unstructured, mostly hexahedral grid is used with the base cell size of 40 micrometres. Four refinement levels are used in the close proximity of the interface in order to attempt to resolve break-up of droplets. The finest cells near the interface have the size of 2.5 micrometres. Part of the nozzle is also considered in the simulation in order to capture the developed jet profile at the entry into the combustion chamber. The temporal evolution of the jet is presented, along with the preliminary comparison of droplet statistics with available results.</p