Large eddy simulations involving dynamic subgrid-scale stress models reveal questions regarding the formulation of dynamic stress models. The dynamic Smagorinsky model, for example, yields large fluctuations and can easily become unstable. An analysis explains the reasons for these problems: it is shown that the dynamic Smagorinsky model involves an incorrect scale dependence which may produce ...

In this note we prove the existence of an inertial manifold, i.e., a global invariant, exponentially attracting, finite-dimensional smooth manifold, for two different sub-grid scale α-models of turbulence: the simplified Bardina model and the modified Leray-α model, in two-dimensional space. That is, we show the existence of an exact rule that parameterizes the dynamics of small spatial scales ...

LES models using dynamically computed coefficient values have been extensively used since the pioneering work of Germano (Germano et al. 1991). Starting from the Smagorinsky subgrid-scale model, the common idea to all these models is to extrapolate the information on the resolved fields at two scale levels to compute optimal coefficient values. A simple solution to the integral equations which ...

The implementation and the combination of advanced boundary conditions and subgrid scale models for Large Eddy Simulations are presented. The goal is to perform reliable cold flow LES simulations in complex geometries, such as cylinder engines. In the paper, an inlet boundary condition for synthetic turbulence generation is combined with a fully non reflecting Navier Stokes Characteristic Bound...

Natural ventilation in buildings can create a comfortable and healthy indoor environment, and can save energy used in the mechanical ventilation systems. Two subgrid-scale models of large eddy simulation (LES), a Smagorinsky subgrid-scale (SS) model and a Filtered dynamic subgrid-scale (FDS) model, have been used to study airflow in buildings with natural ventilation. It was found that, for ful...

The aim of the current work is to investigate a series of new subgrid models by employing the Kolmogorov equation of ltered quantities (KEF), which is an exact relation of turbulence in physical space. Di erent formulations of KEF are derived, including the forms in velocity eld (homogeneous isotropic turbulence, inhomogeneous anisotropic turbulence, homogeneous shear turbulence, homogeneous ro...