The 3D numerical simulation was carried out for an idealized Rankine vortex using nonlinear k-e model (one kind of RANS\r\nmodel) and large eddy simulation (LES) techniques. In this 3D simulation, the vortex flow field was given to rotate with the\r\nvertical axis in a free surface rectangular domain. In order to investigate the predictability of standard (linear) and non-linear k-e\r\nmodels, the decay of a trailing vortex was simulated and compared with previous DNS data. The governing equations for mean\r\nvelocities and turbulent flows were discretized with the finite volume method based on a staggered grid system. It was observed\r\nthat in the growth phase as well as in stabilized phase of turbulence, the decay rate of tangential velocity by RANS model was well\r\ncomparable with LES simulation as well as previous DNS data. However, in the decay phase of turbulence, RANS model showed\r\nslightly faster decay of tangential velocity due to its slower decay of turbulence compared to LES or DNS. The patterns as well as\r\nmagnitudes of secondary currents predicted by RANS and LES models were well comparable to each other.
Loading....