Turbulence modeling for large eddy simulations
This special issue focuses on turbulence and large eddy simulation (LES). The papers were contributed by authors who were invited to participate in the minisymposium titled ''Turbulence Modeling for Large Eddy Simulations" that took place at the 9th US National Congress on Computational Mechanics, San Francisco, CA, July 22-26, 2007. LES is a promising turbulence modeling technology in which the most energetic components of the velocity field are represented, while the effects of the smallest, dissipative scales are modeled. Although several novel approaches have been developed to model these nonlinear interactions, limitations of current modeling approaches need to be addressed, particularly in the context of engineering design and analysis. With this as motivation, the contributing authors discuss several open issues in LES. Scale separation and scale interactions are fundamental aspects of LES modeling. Half of the articles use a priori scale separation within the variational multiscale framework, while three other articles present new modeling techniques for the evolution of the small-scales: a regularization technique to model the Navier-Stokes equations, a time averaging technique to model the small-scale dynamics, and an embedded system of three mutually orthogonal one-dimensional transport equations that are dynamically coupled. Three articles discuss wall-modeling issues, two of these discuss new modeling procedures, while the third assesses the effect of wallmodeling on simulations used for engineering design. Four articles discuss the effect of the temporal discretization on the simulation results, while five of them address the interaction between numerical dissipation (introduced to stabilize the discrete dynamical system) and the eddy viscosity (introduced on physical grounds). These issues need to be better understood to develop more reliable simulation technologies. A noteworthy aspect of the contributed articles is that the numerical methods utilized span stabilized and discontinuous finite elements, finite volume, spectral, and NURBS (non-uniform rational B-splines) based isogeometric methods, demonstrating the diversity in numerical methods presently used in LES.