Turbulent mixing of water masses of different temperatures and salinities is an important process for both coastal and large-scale ocean circulation. It is, however, difficult to capture computationally. One of the reasons is that mixing in the ocean occurs at a wide range of complexity, with the Reynolds number reaching
, or even higher.In this study, we continue to investigate whether large eddy simulation (
LES) can be a reliable computational tool for stratified mixing in turbulent oceanic flows.
LES is attractive because it can be
times faster than a direct numerical simulation (
DNS) of stratified mixing in turbulent flows. Before using the
LES methodology to compute mixing in realistic oceanic flows, however, a careful assessment of the
LES sensitivity with respect to
Re needs to be performed first. The main objectives of this study are: (i) to investigate the performance of different
LES models at high
Re, such as those encountered in oceanic flows; and (ii) to study how mixing varies as a function of
Re. To this end, as a benchmark we use the lock-exchange problem, which is described by unambigous and simple initial and boundary conditions. The background potential energy, which accurately quantifies irreversible mixing in an enclosed system, is used as the main criterion in
a posteriori testing of
LES.This study has two main achievements. The first is that we investigate the accuracy of six combinations of two different classes of
LES models, namely eddy-viscosity and approximate deconvolution types, for 3×10
3Re3×10
4, for which
DNS data is computed. We find that all
LES models almost always provide significantly more accurate results than cases without
LES models. Nevertheless, no single
LES model that is persistently superior to others over this
Re range could be identified. Then, an ensemble of the four best performing
LES models is selected in order to estimate mixing taking place in this system at
Re=10
5 and 10
6, for which
DNS is presently not feasible. Thus the second achievement of this study is to quantify mixing taking place in this system over an
Re range that changes by three orders of magnitude. We find that the background potential energy increases by about 67% when
Re is increased from
Re=10
3 to
Re=10
6, within the computation period, with the most significant increase taking place from
Re=3×10
3 to
Re=10
5.
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