Entrainment turbulent region

GASFLOW models geometrically complex containments, buildings, and ventilation systems with multiple compartments and internal structures. It calculates gas and aerosol behavior of low-speed buoyancy driven flows, diffusion-dominated flows, and turbulent flows dunng deflagrations. It models condensation in the bulk fluid regions heat transfer to wall and internal stmetures by convection, radiation, and condensation chemical kinetics of combustion of hydrogen or hydrocarbon.s fluid turbulence and the transport, deposition, and entrainment of discrete particles. 

Pulsation in a spray is generated by hydrodynamic instabilities and waves on liquid surfaces, even for continuous supply of liquid and air to the atomizer. Dense clusters of droplets are projected into spray chamber at frequencies very similar to those of the liquid surface waves. The clusters interact with small-scale turbulent structures of the air in the core of the spray, and with large-scale structures of the air in the shear and entrainment layers of outer regions of the spray. The phenomenon of cluster formation accounts for the observation of many flame surfaces rather than a single flame in spray combustion. Each flame surrounds a cluster of droplets, and ignition and combustion appear to occur in configurations of flames surrounding droplet clusters rather than individual droplets. 

The modelling of aerodynamic entrainment is based on the close link between particles take-off and turbulent coherent structures above the surface. In fact, some authors [6,7] have experimentally observed that a particle take-off can be associated to the ejection of fluid from the wall region due to the presence of streamwise counter rotating vortices. If it is assumed that the presence of two streamwise counter rotating vortices produces only one ejection, each pair of streamwise vortices is considered as a possibility that a particle takes-off. Thus, for each of these possibilities, a take-olf criterion is tested. 

While it is tempting, it would be premature to apply these equations and findings directly to more complex spray combustor situations. Apart from obvious differences in overall geometry, in practical sprays three effects are superimposed transients associated with oxidizer entrained in the fuel injector region, droplet-size-dependent relative motion between the fuel droplets and the surrounding gas, and oxidizer and product transport by turbulence and convection. Rather, our present QS and future transient studies of the behavior of quiescent fuel droplet clouds should be viewed as necessary first steps in the qualitative and quantitative theoretical understanding of fuel droplet sprays. Future work should be concerned not only with the conditions under which theoretical group combustion occurs in fuel sprays but also with the implications of such cooperative phenomena for combustion eflBciency in volume-limited systems, and pollutant emissions. 

Over the remainder of the region, concentrations of methane ranged from 300-500 nL/L. The small surface maximum observed near Unimak Pass arises from vertical turbulence in Unimak Pass. Near-bottom waters south of the Alaska Peninsula are enriched in methane, which becomes entrained in the northerly flow through the pass. Again, the surface concentrations of methane indicate the mean surface current drift as water moves into the Bering Sea. 

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