We re-examine the Boussinesq hypothesis of an effective turbulent viscosity within the context of simple closure considerations for models of strong magnetohydrodynamic turbulence. Reynolds-stress and turbulent Maxwell-stress closure models will necessarily introduce a suite of transport coefficients, all of which are to some degree model-dependent. One of the most important coefficients is the...

We investigate the time evolution of mixing in turbulent overturns, using a combination of direct numerical simulations (DNS) and microstructure profiles obtained during two field experiments. Our focus is on the flux coefficient , the ratio of the turbulent buoyancy flux to the turbulent kinetic energy dissipation rate . In observational oceanography, a constant value = 0:2 is often used to in...

Early in 1989, the late Marcel Golay derived a theory for turbulent flow capillary gas chromatography. He assumed that the flow pattern under turbulent conditions consists of a turbulent core separated from the tube wall by a very thin laminar flow layer. Further, it was assumed that the viscosity and the diffusion constant are uniform within the turbulent core. The core radius is a fraction p ...

Characteristics of external intermittency in the outer region of turbulent boundary layers are presented based on single-point hotwire measurements. The distinction between the turbulent and non-turbulent state of the flow is marked by applying a threshold on instantaneous kinetic-energy, and this criteria is found to be adequate for this study. Mean intermittency profiles are in consistent agr...

This research started on May, 1999 at the committee of turbulent combustion in the Open and Integrated Research Program (OIRP), The Science and Technology Agency (STA). The purpose of the research is to pursue a possibility on smart control of turbulent combustion and to achieve the improvement of combustion efficiency, that on environment and so on. The present feasibility study shows the foll...

Fully developed stationary premixed flames are obtained by DNS in an incoming homogeneous isotropic turbulent flow. Analysis based on the Favre-averaged transport equation of turbulent kinetic energy shows that pressure gradient term and pressure work term increase turbulent kinetic energy in the flame region, and these terms produce anisotropic turbulence. The counter-gradient diffusion domina...

We present a combined Direct Numerical Simulation and Hot Wire Anemometry study of an axisymmetric turbulent wake. The data lead to a revised theory of axisymmetric turbulent wakes which relies on the mean streamwise momentum and turbulent kinetic energy equations, self-similarity of the mean flow, turbulent kinetic energy, Reynolds shear stress and turbulent dissipation profiles, non-equilibri...

Calculating the statistical linear response of turbulent dynamical systems to the change in external forcing is a problem of wide contemporary interest. Here the authors apply linear regression models with memory, AR(p) models, to approximate this statistical linear response by directly fitting the autocorrelations of the underlying turbulent dynamical system without further computational exper...

Occurrence of laminar separation bubbles on solid walls of an elliptic cylinder has been simulated using a recently developed transitional model for boundary layer flows. Computational method is based on the solution of the Reynolds averaged Navier-Stokes (RANS) equations and the eddy-viscosity concept. Transitional model tries to simulate streamwise fluctuations, induced by freestream turbulen...