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Feature 3 | CFD & HYDRODYNAMICS Setting the trends for CFD for Maritime Flows


Increased hardware power and progress in various aspects of the flow solvers allow more sophisticated applications and wider scope of applications. Milovan Peric, CD-adapco and Volker Bertram, Dept. Mech. Eng., University of Stellenbosch explore the trends in CFD applications for maritime flows.


C


omputational fluid dynamics (CFD) projects today are oſten noticeably shorter


than they


• Te ability to handle complex geometry with all relevant details, including


• Efficient simulation process moving parts (from


• Adequate modelling of turbulence, free-surface effects and cavitation


geometry to solution, parametric studies, optimisation studies, user interface...)


• Coupled simulation of flow and flow-induced motion (and in some


cases deformation) of bodies. Tese are discussed in more detail in


Peric and Bertram (2011).


Key aspects in CFD for maritime flows Grid generation has improved, making it easier to generate high-quality grids for accurate CFD simulations. A key aspect for complex geometries consisting of many components (such as offshore


The Naval Architect July/August 2011


Re-meshed surface of a complete oil rig after surface-wrapping (left) and simulated air flow field around the oil rig (right).


platforms in the maritime context) is geometry recognition. The software then recognises automatically cylinders (with extrusion along centreline, using prismatic cells) and thin solids or gaps, with projection from one side to another, using prismatic cells. More sophisticated analyses for ships


• The ability to handle moving parts using morphing, sliding interfaces


and offshore platforms employ a variety of techniques that have become widely available (through commercial and open-source soſtware).


• Te ability to model complete systems rather than single parts (e.g. ship with


or overlapping grids (e.g. propellers, rudders etc.)


• Te ability to easily replace geometry and


perform a


all appendages, complete oil platforms, etc.)


new simulation


(automation of simulation process; e.g. ship with and without a wake equalising nozzle).


Turbulence modelling For most applications in industry, the


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were two decades ago. This is due to considerably improved pre-processing and post-processing. The progress in user-friendliness is perhaps best illustrated in the case of integrated design environments, which have lowered the thresholds in using CFD for designers. For example the Friendship Framework combines freeform hull description using parametric modelling, interfaces to most modern CFD solvers including STAR-CCM+, several optimisation algorithms, and software to handle process management and user interface. Te design engineer can then work on simulation driven designs (e.g. of hulls, appendages or propellers) with one integrated user interface from model generation to post-processing. Many more aspects have advanced the wide acceptance of CFD in industry:


Integrated design environments allow simulation driven designs (Friendship Framework).


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