Plume airflow turbulence

The plume airflows (q ) are determined as described in Section 7.5. The turbulent mixing iqi,) between zones and the penetration of the plume airflows iq, h,n) through the supply airflow patterns must be determined specially for the air distribution method and devices used as well as the locations of plumes and supply air devices. 

The effect of the plume airflow rate and the turbulent mixing airflow rate through the zone boundary is presented in Fig. 8.35. The heat removal effectiveness and contaminant removal effectiveness are presented as functions of the relative airllow rate. 

The key flow elements in the zoning strategy arc the supply air jets, plumes of the buoyancy sources, buoyant airflows along the surfaces, and turbulent mixing between the controlled and the uncontrolled zones, as in Fig. 8.32. These flow elements have significant influence on the effectiveness of the system. 

The dominant transport mechanism for both aerosol and gaseous agents in the atmosphere is advection associated with the bulk motion of the atmosphere. Since airflows in the planetary boundary layer exhibit signihcant turbulence under most conditions (though turbulence may be suppressed under conditions of temperature inversion), this will cause aerosol releases to disperse into a plume or puff that expands... 

Still air can be viewed in two ways. One somewhat catholic definition would include air velocity below a level detectable by the optomotor reaction, thus embracing discrete plume structmes similar to those generated in air speeds which can be monitored by the optomotor reaction. A second and more obvious definition would encompass chemical stimuli generated in still air. Dispersion in completely still air would be dominated by molecular diffusion, rather that turbulent diffusion in an airflow, but Mankin et al. (1980) has pointed out that in most still air situations turbulent diffusion will overwhelm molecular diffusion (see Chapter 3). The spatial distributions of chemical stimulus in these two cases will obviously be quite different. 

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