Lateral turbulent mixing

Between 1999 and 2005, a negative trend of -8.6%/year (-0.01 nmol/(kg year)) was calculated for Cddiss in waters Above Halocline. It was assumed that this phenomenon was due to the stabilization of anoxic conditions in the deep water, which led to the increase in the export of Cddiss from surface waters by time lag. To support this idea, the exchange of dissolved metals by vertical turbulent mixing at the oxic-anoxic interface has been calculated, as described later. 

Evaluation of p and Km2 requires determination of the void fraction and the two-phase pressure drop. Crossflow is determined from the appropriate lateral momentum balance equation. The interchange due to mixing, represented by w is determined by the turbulent transverse fluctuating flow rate per foot of axial length (lb/hr ft), where... 

In Chapter 11, we indicated that deviations from plug flow behavior could be quantified in terms of a dispersion parameter that lumped together the effects of molecular diffusion and eddy dif-fusivity. A similar dispersion parameter is usefl to characterize transport in the radial direction, and these two parameters can be used to describe radial and axial transport of matter in packed bed reactors. In packed beds, the dispersion results not only from ordinary molecular diffusion and the turbulence that exists in the absence of packing, but also from lateral deflections and mixing arising from the presence of the catalyst pellets. These effects are the dominant contributors to radial transport at the Reynolds numbers normally employed in commercial reactors. 

Diffusion flames can best be described as the combustion state controlled by mixing phenomena—that is, the diffusion of fuel into oxidizer, or vice versa—until some flammable mixture ratio is reached. According to the flow state of the individual diffusing species, the situation may be either laminar or turbulent. It will be shown later that gaseous diffusion flames exist, that liquid burning proceeds by a diffusion mechanism, and that the combustion of solids and some solid propellants falls in this category as well. 

Hydrothermal venting injects fluids into seawater as buoyant, jetlike pliunes. These turbulent flows mix rapidly with seawater becoming diluted by factors of lO" to 10. This mixing eventually makes the plumes neutrally buoyant, after which they are transported laterally through the ocean basins as part of the intermediate and deepwater currents. Hydrothermal plumes have the potential to greatly affect seawater chemistry. From global estimates of hydrothermal fluid emissions and dilution ratios, a volume of seawater equivalent to the entire ocean can be entrained in the hydrothermal plumes every few thousand years. 

Vertical Mixing by Turbulence Lateral Mixing by Turbulence Longitudinal Mixing by Dispersion... 

Figure 24.4 Mixing processes in a river. Ey and E, are the turbulent diffusion coefficients in the lateral and vertical direction, respectively h0 is the maximum depth. Longitudinal dispersion, djs, results from the variation of velocity in a given cross section of the river. A pollutant added to the river in cross section A-B mixes vertically and laterally into the whole river cross-section.

---