engleski

Assessment of Higher–Order Forces on a Vertical Cylinder with Decomposition Model Based on SWENSE Method

Off–shore structure design often relies on accurate assessment of higher–order forces because of ringing phenomena. In this work, calculation of higher–order forces on a vertical surface piercing cylinder is carried out by a decomposition CFD model. The model is based on Spectral Wave Explicit Navier–Stokes Equations (SWENSE) [1], allowing efficient coupling of arbitrary potential flow solutions with fully non–linear, viscous, two–phase CFD model. The domain is decomposed with implicit relaxation zones [2], preventing wave reflection. Implicitly redistanced Level Set method [3] is used for interface capturing, where additional explicit redistancing is not necessary. The validation of the method is performed on two sets of test cases. First, mesh and time refinement studies are carried out for a case with intermediately steep (ka = 0.12) incoming wave train. Second, a set of waves with different frequencies are simulated, keeping the wave steepness constant, ka = 0.06. Higher–order forces up to fourth order are compared with fully non–linear potential flow results [4]. A discussion on strong second order behaviour of vorticity effects in the vicinity of the cylinder is presented.

Decompositon model; SWENSE; Higher-order forces; Vertical Cylinder

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