E−ǫ turbulence model predictions of the neutral atmospheric boundary layer (NABL) are reinvestigated to determine the cause for turbulence overpredictions found in previous applications. Analytical solutions to the coupled E and ǫ equations for the case of steady balance between transport and dissipation terms, the dominant balance just below the NABL top, are derived. It is found that analytic...

E− turbulence model predictions of the neutral atmospheric boundary layer (NABL) are reinvestigated to determine the cause for turbulence overpredictions found in previous applications. Analytical solutions to the coupled E and equations for the case of steady balance between transport and dissipation terms, the dominant balance just below the NABL top, are derived. It is found that analytical ...

A two dimensional model is introduced to study pattern formation, secondary instabilities and the transition to spatiotemporal chaos (weak turbulence) in parametric surface waves. The stability of a periodic standing wave state above onset is studied against Eckhaus, zig-zag and transverse amplitude modulations (TAM) as a function of the control parameter ε and the detuning. A mechanism leading...

The results are reported of an experimental investigation of turbulent flow through a plane sudden expansion of expansion ratio R=D/d=4 and aspect ratio A= w/h=5.33. It is well known that plane sudden expansions with R greater than 1.5 produce asymmetric flows and this was again seen in this study. The literature for the asymmetric situation (R>1.5) is surprisingly limited and only axial veloci...

We derive closure relations for a plasma fluid model, issued from the BGK equation for electrons in a strong magnetic-field. Our scaling of the BGK equation leads in the asymptotic limit ε → 0 towards the adiabatic electron regime, where ε embodies the scaled Larmor radius as well as a low Mach number. In this regime the electron density adjusts instantaneously to perturbations of the electric ...

Cooling heat transfer of supercritical CO2 in horizontal straight tubes with wall is numerically investigated by using FLUENT. The results show that almost all models are able to present the trend of heat transfer qualitatively, and the stand k-ε with enhanced wall treatment model shows the best agreement with the experimental data, followed by LB low Re turbulence model. Then further studies a...

The probability density function (PDF) approach has been shown to be a useful tool in turbulence research. The systematic approach for determining PDFs is by means of solving the transport equations for PDFs. In the PDF equations for turbulent scalar fields, conditional dissipation rate (CDR) appears as the only unclosed term (Pope (1985)). Recently developed large-eddy simulation schemes for t...