Models of turbulence in the marine environment - a comparative study of two-equation turbulence models

This study compares the performance of the most widely used two-equation tu rbulence closures for marine and atmospheric applications, the k-epsilon an d the Mellor-Yamada level 2.5 (MY) model. For a better understanding, the p hysical equations are given in a joint notation. Stability functions origin ally suggested by Galperin et al. (1988) are used here with slight modifica tions in order to allow for numerically stable computations of free convect ion. Far the k-epsilon models, a flux boundary condition for the dissipatio n rate is tested. In contrast to the classical Dirichlet condition, its str aightforward discretization allows for sufficient accuracy also in three-di mensional models with coarse vertical resolution. The models are then appli ed to idealized situations including free convection, wind mixing and strat ified steady-state boundary layer flow. Finally, the spring development of thermal surface stratification as measured during the FLEX'76 experiment is simulated. For all these different, partially complex situations, the k-ep silon and the MY model proved to perform similarly. (C) 1999 Elsevier Scien ce B.V. All rights reserved.