Interference phenomenon in design of trimaran ship

10th International Conference on Fast Sea Transportation – FAST 2009, Athens, Greece, October 2009

The hydrodynamic flow interference effect between the main and side hulls of Trimaran ships have a major influence on the total power and on the positioning of the side hulls. The main objective herein is to understand the physical reasons that explain the interference phenomenon. The hydrodynamic research and model testing of the large Trimaran ship – Heavy Air Lift Support Ship (HALSS) showed a large change in resistance ( 70%) due to a moderate (15% from length of center hull) shift in the longitudinal side hull position. Another observation is to the influence of the skegs on the stern flow. In order to fully understand the factors leading to the interference effects, several Computational Fluid Dynamics calculations were performed with various computational codes and compared to model test data. The paper contains the results of HALSS model testing at NSWCCD. Tests were performed on the center hull to select different bow sections and on Trimaran with three longitudinal and three transverse positions of the Small Waterplane Area HALSS side hulls. These experimental results are compared to CFD calculations by the following CFD codes: FINE™/Marine, FLUENT, SWIFT (Ship Wave Inviscid Flow Theory) and MQLT (Modified Quasi Linear Theory). For all these test cases, comprehensive comparisons between computations and experimental data are presented to support the physical analysis in order to assist future design methodologies for multihull ships.

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