We consider vertical heat transport in Keplerian accretion disks, including the effects of radiation, convection, and turbulent mixing driven by the Balbus-Hawley instability, in astronomical systems ranging from dwarf novae (DNe), and soft X-ray transients (SXTs), to active galactic nuclei (AGN). In order to account for the interplay between convective and turbulent energy transport in a shear...

Turbulent combustion is an important process in many technical applications, e.g. industrial gas furnaces used for heating water, production of steam and combustion in jet and diesel engines. To control the turbulent combustion, simulation tools with predictive power are required. The basic equations for turbulent combustion are well known, but their application to the complex flows appearing i...

Computational modeling is an important tool to understand and stabilize transient turbulent fluid flow in the continuous casting of steel to minimize defects. The current work combines the predictions of two steady Reynolds-averaged Navier–Stokes (RANS) models, a ‘‘filtered’’ unsteady RANS model, and two large eddy simulation (LES) models with ultrasonic Doppler velocimetry (UDV) measurements i...

A deterministic multiscale dynamical system is introduced and discussed as a prototype model for relative dispersion in stationary, homogeneous, and isotropic turbulence. Unlike stochastic diffusion models, here trajectory transport and mixing properties are entirely controlled by Lagrangian chaos. The anomalous "sweeping effect," a known drawback common to kinematic simulations, is removed thr...

Real-time capture of the relevant features of the unresolved turbulent dynamics of complex natural systems from sparse noisy observations and imperfect models is a notoriously difficult problem. The resulting lack of resolution and statistical accuracy in estimating the important turbulent processes which intermittently send significant energy to the large-scale fluctuations hinders efficient p...

Modeling the primary atomization of turbulent liquid jets and sheets still remains an unsolved problem. Considering numerical grid resolutions typical for Large Eddy Simulations, the large scale liquid structures during primary breakup are well resolved, whereas all small scale structures are unresolved and thus require modeling. To help in the derivation of such subgrid models, DNS of the turb...

The deflagration mode of flame propagation in Type Ia supernova (SN Ia) models requires a correct description of the interaction of the flame with turbulent motions. It is well-known that turbulent combustion proceeds in different regimes. For most parts of the deflagration in SNe Ia the flamelet regime applies. This has been modeled in previous multi-dimensional simulations. However, at late s...

A detailed review of recent developments in Reynolds stress modeling for incompressible turbulent shear ows is provided. The mathematical foundations of both two-equation models and full second-order closures are explored in depth. It is shown how these models can be systematically derived for two-dimensional mean turbulent ows that are close to equilibrium. A variety of examples are provided t...

in this paper, the accuracy of k- and k- turbulence models in super sonic boundary layer capturing of smooth/rough flat plates have been comprehensively investigated. among these investigations, some sorts of sensitivity analysis, including change in turbulence model, generated-grid density, near wall affects, c magnitude (for boundary layers generated on smooth flat plates), and change in c...