Comparison of the k-ε and k-ω turbulence models in a laboratory and a river modelling context

Michael Tritthart, Arno Mayrhofer, Martin Glas, Kurt Glock, Helmut Habersack

Tuesday 30 june 2015

14:35 - 14:50h at Europe 1 & 2 (level 0)

Themes: (T) Water engineering, (ST) Computational methods

Parallel session: 6E. Engineering - Computational

In this contribution the performance of the standard k-ε turbulent closure is compared with the k-ω model in two simulation settings: (i) a racetrack flume with a semi-trapezoidal cross-section in a hydraulic laboratory; (ii) a reach of 2.5 km length at the Danube River in Austria, characterized by several groyne fields and a relatively complex morphological setting. From the simulation results of the laboratory flume it was found that the k-ω model predicts steeper velocity gradients and more elliptically shaped recirculation zones, as compared to the k-ε model. These results of the k-ω turbulent closure locally indeed correspond more closely to measurements, though there exist regions of the flow domain in which the k-ε model yields superior results. In a simulation of a reach of the Danube River, the differences between the models were substantially smaller but nonetheless visible in the flow field. In this setting, the k-ω model exhibited a tendency to smoothen extremes in flow velocities, while differences in the gyres developing in the groyne fields could not be detected. This finding is credited to the complex boundary conditions in nature influencing the flow field to a larger extent than the plain effect of turbulence.