The use of RANS viscous CFD simulations to evaluate the resistance of ships is well established. These methods,
however, often require a high number of calculation cells with consequent substantial hardware requirements.
BEM analysis can be performed in a short time and with modest hardware resources, but returned more qualitative
results without the viscous part, even if proven and reliable. The objective is to achieve good RANS simulations
in a short time so as to make them competitive with panel methods especially in the evaluation phase of different
design alternatives. The aim of this work is to study and standardize the operating modes to do viscous simulations
with low number of cells, for carrying out more rapidly the calculations, without any necessity of super-computers.
The foregoing methods are applied to study high speed trimaran hulls. For the RANS method a system of localized
mesh-sizing of the computational grid is evaluated to get a good simulation in the shortest time possible. Results
for resistance and trim from RANS 3-DOF simulations are compared with experimental towing tank tests and with
BEM analysis also using transverse and longitudinal wave-cuts.
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