Hydrodynamic Analysis of a Suspended Cylinder Under Regular Wave Loading Based on Computational Fluid Dynamics: Preprint

An investigation into the computation of hydrodynamic loads on a suspended cylinder in regular waves is presented. The primary goal was to perform a three-way-validation of the loads between experimental measurements and simulations from two computational methods. Experimental measurements of the longitudinal inline force on a cylinder suspended at a fixed po- sition were available from the Offshore Code Comparison Col- laboration, Continued, with Correlation (OC5) project, Phase Ia. These measurements were compared to Computational Fluid Dynamics (CFD) simulations based on the solution of Reynolds- averaged Navier-Stokes (RANS) equations, as implemented in STAR-CCM plus. The study encompassed a sensitivity analysis of the loads computed in STAR-CCM plus based on wave modeling, boundary conditions, turbulence modeling, and spatial and tem- poral discretization. The analysis was supplemented by results generated with the offshore wind turbine engineering software OpenFAST, based on a hybrid combination of second-order po- tential flow and viscous drag fromMorison's equation. The focus of the investigation was on the assessment of the accuracy of the computation of first- and higher-order hydrodynamic loads. Sub- stantial differences were observed in the numerical prediction of the second and third harmonic force contribution. Local flow field analysis with CFD was applied to study the physics of wave run-up and diffraction dynamics to identify the causes.