Models convective mixing

In what follows, both macromixing and micromixing models will be introduced and a compartmental mixing model, the segregated feed model (SFM), will be discussed in detail. It will be used in Chapter 8 to model the influence of the hydrodynamics on a meso- and microscale on continuous and semibatch precipitation where using CFD, diffusive and convective mixing parameters in the reactor are determined. 

The difference in the Li abundances in the G-stars of the Pleiades and the Sun, combined with the probable similarities in their overall chemical composition tell us that PMS Li depletion cannot be the whole story. Another mechanism, additional to convective mixing, must be responsible for Li depletion whilst solar-type stars are on the main-sequence. Recent PMS models that have their convective treatments tuned to match the structure of the Sun reproduce the mass dependence of Li depletion, but deplete too much Li compared with the Pleiades, and can even explain the solar A (Li) in the case of full spectrum turbulence models [9]. The over-depletion with respect to the Pleiades gets worse at lower masses. Better fits to the Pleiades data are achieved with PMS models that feature relatively inefficient convection with smaller mixing lengths. 

Bakd et al. theoretically analyzed simultaneous gas flow and diffusion in Weibel s symmetric model. Th applied a time-varying flow with simultaneous longitudinal diffusion and concluded that convective mixing is much less important than mixing induced by molecular diffusion. 

Two scenarios for the crystallization of the lunar magma ocean, involving different amounts of melt. In both models, olivine and orthopyroxene cumulates sink and plagiodase floats, but the thickness of the plagiodase-rich crust is greater for a completely melted Moon. Ilmenite crystallizes late in both models, but mixing of dense, ilmenite-rich rocks with early magnesium-rich cumulates could result from convection. After Ryder (1991). 

If the parameters a j have constant values, then the model described by system (4.71) corresponds to a Markov connection linking the process components. In this case, as in general, the process components represent the individual displacements which can be characterized globally through the convective mixing of their spectra of speeds ( v, k= 1,N). 

Several PEACE-B flights were carried out in May 2002 when convective CO transport was active. Figure 17.4 shows the vertical profiles of the observed and modeled CO mixing ratios on 14 May 2002 (flight 10, PEACE-B). CO increased at levels between 300 00 hPa. The model typically underestimated background CO... 

The details of the helium hash are still poorly understood. It is clear that very short timescales are involved, and that nuclear-driven convection mixes some layers of the star. Realistic 3D models of the helium-hash are now becoming possible [34]. It is not clear how much of the star is mixed,... 

A measurement of CN-cycle neutrino flux (with an expected total flux of about 5 x 108 cm 2 s-1) would test an assumption of the Standard Solar Model that during the early pre-main-sequence Hayashi phase the Sun became homogeneous due to convective mixing and that subsequent evolution has not appreciably altered the distribution of metals [38]. 

Hydrogen-air-steam combustion experiments have been conducted to simulate local detonations in a nuclear containment and to validate the respective numerical detonation codes. Experimental facilities used were the Battelle model containment and the containment of the decommissioned HDR in Germany as well as one-compartment vessels at Hanford and Nevada Test Site in the USA or the RUT facility in Russia. Many codes have been developed to simulate the transport, convective mixing, and combustion of hydrogen in a containment building. State-of-the-art are CFD models or lumped parameter models with successful reproduction of, e.g., thermal stratification phenomena. 

It will be convenient here to use the terms diffusive mixing for stage (c) and convective mixing for stages (a) and (b). It has not yet proved possible to develop a complete physical description of mixing in turbulent fluids. The present review will confine itself to simple models, which are supported by experimental work and which are (or could be) used industrially. 

Rosenthal FS, Blanchard ID, Anderson PJ. Aerosol bolus dispersion and convective mixing in human and dog lungs and physical models. J Appl Physiol 1992 73 862-873. 

Distributive or simple mixing is induced by plug or bulk convection. Bulk convection can be random or ordered. Ordered bulk convection rearranges constant volumina in a well defined way, and the progress of mixing action can be predicted mathematically. In random bulk convection, chunks of material are randomly redistributed, and modeling the mixing action is for most cases not possible. 

Consider the unit square domain of the sine flow, where the right side is filled with reactant A and the left side contains only B. The initial interface between the two components is a vertical line along the center and one edge of the box. At t = 0 convective mixing is turned on in the model simultaneously with diffusion and reaction. The species balance equation in a dimensionless form for the flow with reaction, diffusion, and convection is... 

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