On the Practical Advantages of the Quasi-equilibrium Version of the Mellor and Yamada Level-2.5 Turbulence Closure Applied To Marine Modeling

Deleersnijder, Eric [UCL] Luyten, Patrick [UCL]

The Mellor and Yamada level 2.5 turbulence closure model is briefly presented. It is argued that it might achieve an excellent compromise between accuracy and computer efficiency. It is, however, suggested that the stability functions are ill defined, leading to a marked lack of robustness, which manifests itself through the appearance of almost steady regions of exceedingly high shear. Theoretical reasoning shows that the seemingly less known quasi-equilibrium version of the level 2.5 model has more appropriate stability functions, rendering it more robust for marine modelling, where many different flow configurations are to be handled. This is strikingly illustrated by numerical experiments pertaining to the stress-driven penetration of a turbulent layer into a stratified fluid.