VLES modelling of geophysical fluids with nonoscillatory forward‐in‐time schemes

Abstract

AbstractAtmospheres and oceans are mostly incompressible and turbulent. The experience of the meteorological community with modelling such flows is based primarily on centred in time and space (CTS) methods. Our experience applying non‐oscillatory forward in time methods (NFT) to a range of flows has revealed some unexpected benefits specifically in the area of modelling geophysical turbulence where broad span of scales, density stratification, planetary rotation, inhomogeneity of the lower boundary, etc., make explicit modelling of subgrid‐scale motions particularly challenging. It turns out that in the absence or insufficiency of a proper subgrid‐scale model, NFT methods supply their own, implicit, turbulence models that are quite effective in assuring quality simulations of high‐Reynolds number flows. Since such simulations abandon rigorous notion of the large‐eddy simulation approach, and merely aim at computing explicitly large coherent eddies resolvable on the grid, they are referred to as very‐large‐eddy simulations (VLES). In this paper we will describe advantages of the NFT approach and illustrate them with an example of gravity‐wave‐breaking induced turbulence in a deep atmosphere. On the philosophical side, we challenge a common misconception that NFT methods are overly diffusive and therefore inadequate for high Reynolds number flow simulations. Copyright © 2002 John Wiley & Sons, Ltd.