Investigation of open-Source CFD software on shipyards - Analysis of combustion outlets on large yachts using openFoam®
Abstract: AbstractModern engineering requires detailed knowledge of forces, flow directions and velocities, when designing the vehicles of the future. In the ship building industry this is traditionally done in towing tank and wind tunnel experiments or by the long experience of skilled engineers. In the last years computational fluid dynamic (CFD) methods developed to a stage, where they become interesting, not only from a financial but also from a performance point of view, for larger ship yards as an extra input and in long term thinking as a full alternative to the experiments.The special branch of luxury yacht building yards is like every business in strong competition and needs to work economical. It can be very expensive to carry out both methods on the one hand. Since on the other hand these high technology yards have special requirements to fulfill that might change more frequently than for commercial ships, CFD is often a desirable method for the yards to master. The open source software (OSS) openFoam® offers here a possibility to include a modern CFD method without extensive investment costs into the design process and to gain "free" experience with a technology of the future.The present thesis shows the strength and weaknesses of openFoam® in the ship building industry for and in close collaboration with the Friedrich Lürssen shipyard in Bremen. The yard has specialized in the construction of luxury yachts over 60m and naval vessels over 30m.Due to openFoam®´s classical case folder structure, several tutorials were created to investigate this purpose. They reflect typical flow situations needed by the yard for future analysis, i.e. a wind tunnel setup, a towing tank setup, a sinkage and trim tutorial, a heat analysis tool and a particle injector. Besides the important resistance calculations the main focus lay on the analysis of the exhaust gas behavior. Mega yacht customers demand lowest possible air pollution on deck, so that extensive wind tunnel experiments are done during the early design stages. The aerodynamic tutorial was created as an alternative to these experiments. Satisfying results were achieved with openFoam® when compared to tests conducted by the Hamburgische Schiffbau- Versuchsanstalt (HSVA). To show the differences in performance to commercial software the hydrodynamic results of openFoam® solver were compared to StarCCM+ by CD-adapco.The investigation now clearly showed that openFoam® has competitive performance abilities to experiments and commercial CFD software. When no expensive openFoam® training is paid for the time it takes to gather experience in openFoam® handling is long, but can be shortened immensely by the usage of formerly prepared tutorials. In ship design the most important simulations do not change very often, so that this structure can be a help for the yard. But the unusual structure and the unsatisfying product documentation set the limits quite high for the time restricted ship building business to risk the use of the academically developed tool.
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