In this paper, we derive a general relationship for the turbulent Prandtl number Pr t for homogeneous stably stratified turbulence from the turbulent kinetic energy and scalar variance equations. A formulation for the turbulent Prandtl number, Pr t , is developed in terms of a mixing length scale LM and an overturning length scale LE , the ratio of the mechanical (turbulent kinetic energy) deca...

The aim of this Letter is to characterize the flow regimes of suspensions of finite-size rigid particles in a viscous fluid at finite inertia. We explore the system behavior as a function of the particle volume fraction and the Reynolds number (the ratio of flow and particle inertia to viscous forces). Unlike single-phase flows, where a clear distinction exists between the laminar and the turbu...

Accurate predictions of the sea state–dependent air–sea momentum flux require a thorough understanding of the wave boundary layer turbulence over surface waves. A set of momentum and energy equations is derived to formulate and analyze wave boundary layer turbulence. The equations are written in wavefollowing coordinates, and all variables are decomposed into horizontalmean, wave fluctuation, a...

Turbulent combustion is three-dimensional. Turbulence in a Type Ia supernova is driven on large scales by the buoyancy of burning products. The turbulent cascade penetrates down to very small scales, and makes the rate of deflagration independent of the microphysics. The competition between the turbulent cascade and the freeze-out of turbulent motions due to stellar expansion determines the lar...

Turbulent cascades at high Reynolds numbers are explained briefly in terms of multipliers and multiplier distributions. Two properties of the multipliers ensure the existence of power laws for locally averaged energy dissipation rate: (a) the existence of a multiplier probability density function that is independent of the level of the cascade, and (b) the statistical independence of multiplier...

Over the last decade there has been a renewed interest in understanding the entrainment process in turbulent shear flows [5]. Even though there are differences between the way different shear flows (such as jets, wakes, boundary layers and shearfree flows) develop [14], the origin of these differences is not clear. Here, employing experimental data from an axisymmetric turbulent jet and a turbu...

To evaluate eddy structures of a plane turbulent jet in the dimension of time and scale, the velocity signals were analyzed using the continuous and discrete wavelet transforms in this paper. From the distribution of coefficients of continuous wavelet transform, localized nearly periodic eddy motions with a=64ms, 100ms and 180ms were respectively observed in the shear layer of x/d=8.5 in the ti...

Introduction MicroChannel Fabrication Experimental Apparatus and Methodology Results and Discussion Summary and Conclusions CHAPTER 4 MICROPIV MEASUREMENT OF TURBULENT FLOW IN RECTANGULAR MICROCHANNELS WITH VARYING AS­ PECT RATIOS Abstract Introduction MicroChannel Fabrication Experimental Methodology Experimental Setup Measurement Error Results and Discussion Summary and Conclusions CHAPTER 5 ...

Probably the first experimental evidence of an important role of the subharmonic resonance in the process of the laminar-turbulent transition in adverse pressure gradient (APG) boundary layers was obtained in [1]. Until recently, the only available direct experimental study of the subharmonic resonant interactions in the APG boundary layer was performed in [2] for rather small values of the Har...

The purpose of this contribution is to present some examples for the use of recent data processing and visualization techniques for the study of unsteady vortical flows. The basic idea is to extract vortices, shear layers and data defining their current state from DNS data and to track their evolution in time. Some apparent signatures which help to get additional insight into the flow dynamics ...