Dynamical Subgrid-Scale Parameterizations from Direct Numerical Simulations

Dynamical Subgrid-scale Parameterizations for Quasigeostrophic Flows using Direct Numerical Simulations

In this thesis, parameterizations of non-linear interactions in quasigeostrophic (QG) flows for severely truncated models (STM) and Large Eddy Simulations (LES) are studied. Firstly, using Direct Numerical Simulations (DNS), atmospheric barotropic flows over topography are examined, and it is established that such flows exhibit multiple equilibrium states for a wide range of parameters. A STM i...

A localised subgrid scale model for fluid dynamical simulations in astrophysics I: Theory and numerical tests

We present a one-equation subgrid scale model that evolves the turbulence energy corresponding to unresolved velocity fluctuations in large eddy simulations. The model is derived in the context of the Germano consistent decomposition of the hydrodynamical equations. The eddy-viscosity closure for the rate of energy transfer from resolved toward subgrid scales is localised by means of a dynamica...

Numerical modeling of subgrid heterogeneity in two phase flow simulations

[1] A coarse-scale model governing two-phase viscous dominated flow in heterogeneous porous media is presented. The coarse-scale water transport equation (or saturation equation) is derived from a volume average of the underlying fine-scale saturation equation. A key component of the coarse-scale description is the subgrid model, which appears in the formulation as a nonlinear, nonlocal term in...

A Discrete Dynamical System Subgrid-Scale Model of Turbulent Convection

Verification of Reynolds stress parameterizations from simulations

Key words hydrodynamics – methods: numerical – turbulence We determine the timescales associated with turbulent decay and isotropization in closure models using anisotropically forced and freely decaying turbulence simulations and study the applicability of these models. We compare the results from anisotropically forced three-dimensional numerical simulations with the predictions of the closur...