Evaluation of URANS Solvers for Cylindrical Structures in Tidal Flow

摘要

In tidal conditions Reynolds numbers (Re) around cylindrical structuresrncan range from zero up to supercritical values, with vortex sheddingrncausing significant vibration and undesirable forces throughout. Twornrealistic options for investigating these phenomena in an engineeringrnenvironment include the Navier-Stokes solvers ANSYS? CFX-13.0rnand OpenFOAM?. In this study both are considered at Reynoldsrnnumbers ranging from 40 to 10~6, representing a full range of tidalrnconditions. A 2D Unsteady Reynolds Averaged Naver-Stokesrn(URANS) approach is developed in an attempt to balance the speed andrnaccuracy of the solutions. To eliminate mesh dependency, low-Rernboundary layer meshing is employed along with Courant controlledrntime stepping.rnNumerical results obtained from both solvers are presentedrnfor lift coefficient, drag coefficient and Strouhal number. Values fromrnboth solvers are compared to literary sources and examined forrnaccuracy. Given that the turbulence for much of the Reynolds numberrnregion explored is known to be highly three dimensional, both codesrnoffer a mix of good and poor results depending on parameters. Overallrnlow and subcritical Re values are modelled with success byrnOpenFOAM, while force terms in upper critical and supercritical flowsrnare better predicted by CFX.