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Ocean Systems Engineering
  Volume 11, Number 2, June 2021 , pages 161-184

RANS CFD simulation for slender floating bodies with forward speed and comparison to BEM with uniform-flow approximation
Farid P. Bakti and MooHyun Kim

    The nonlinear wave-uniform current interaction for a slender floating body is investigated by using the commercial CFD (computational fluid dynamics) tool STAR-CCM+ and author-developed simplified BEM (boundary element method) based on potential theory and perturbation approach. The STAR-CCM+ solves the fully non-linear Reynold Averaged Navier Stoke's (RANS) equation for real fluid in the finite volume framework. The viscous effect is accounted for by mesh refinement and the k-w turbulence closure model. Meanwhile, the fully non-linear body motion and free surface elevation are considered by the overset mesh and volume of fluid method, respectively. Two different input waves with different order of non-linearity are compared to see their effects on ship's motion and added resistance. A detailed step-by-step simulation setup is explained to ensure the reproducibility of the results. Several preliminary simulations such as static tank test, wave calibration, and towing tank case are also conducted for quality assurance. The CFD results show good agreements with both the BEM with Uniform Flow approximation (UF-BEM) and the experimental data by other researchers when the /L is large. The CFD simulation also shows that it can properly capture the second-order force (added resistance) and highly non-linear motion with breaking waves close to the pitch resonance frequency. However, the CFD simulation requires substantially higher computational cost than the UF-BEM. The comparison study shows that the UF-BEM can produce reasonably good results for practical applications with significantly less computational time and human effort. On the other hand, the CFD program can be used for proof computations for special cases.
Key Words
    CFD; BEM; Navier-Stokes equation; fluid-structure interaction; fully non-linear; wave-current interaction; forward speed; added resistance
Farid P. Bakti and MooHyun Kim: Department of Ocean Engineering, Texas A&M University, College Station, Texas, USA

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