Turbulent zone

One simplified method for determining stack height is a geometric method described in ASHRAE. The geometric method assumes an exhaust plume shape with a lower boundary having a 1 5 slope relative to the horizontal. The stack and plume are raised until the lower plume boundary is above rooftop penthouses, separation zones, and zones of high turbulence. ASHRAE provides equations for the sizes and locations of the separation and turbulence zones. A stack height reduction credit is provided to account for the vertical exhaust momentum. 

The effective height of an emission rarely corresponds to tlie physical height of tlie source or the stack. If tlie plume is caught in tlie turbulent wake of tlie stack or of buildings in the vicinity of tlie source or stack, tlie effluent will be mixed rapidl) downward toward the ground. If the plume is emitted free of these turbulent zones, a number of emission factors and meteorological factors influence tlie rise of the plume. 

Between the laminar and turbulent zones, there exists a transition region in which the viscous arid inertial forces are of comparable magnitudes. No simple mathematical relationship exists between Np and Re in this flow region and, at a given value of Re, N p must be obtained from the appropriate power curve. 

At what value of y+ does the transition from the laminar sub-layer to the turbulent zone occur ... 

In the Universal Velocity Profile , the laminar sub-iayer extends to values of y+ = 5 and the turbulent zone starts at y+ = 30 and the range 5 < y+ < 30, the buffer layer, is covered by a second linear relation between and In, y+. What is the maximum difference between the values of u+, in the range 5 < y4 < 30, using the two methods of representation of the velocity profile ... 

As the wall becomes rougher, the velocity profile in the turbulent zone changes as shown in Figure 2.5, and the viscous sublayer and generation zone eventually disappear. 

Eq. 7.2, where is then the eddy diffusion coefficient (Taylor and Spencer 1990). The height of the turbulent zone, within the atmospheric boundary layer, is orders of magnitude greater than that of the laminar flow layer, and dispersion of contaminant vapors in the turbulent zone is relatively rapid. 

D) The vapor of the turbulent zone then condensing and back-reacting with the water surface... 

Despite the observational identification of a possible site of dust formation, however, the dust-driven wind could not be applied to stars without dust envelope, as noted in Sect.II. Then, a more interesting possibility is a turbulence-driven wind,in which the high turbulent pressure of the transition layer(or cool corona) pushes the gas out of star,just as the high thermal pressure in corona does in solar-type stars. In fact, if the turbulent zone is extended to about 10 stellar radii, the local escape velocity there may already be small enough to be comparable with the observed flow velocities. Thus, the Maxwellian tail of the turbulent motion in the quasi-static molecular formation zone can directly lead to stellar mass-loss in all... 

In the turbulent zone the experimental values of Nr fell above the Nusselt line. 

Belkin et al. (B4), 1959 Experimental studies of water films flowing outside tubes observations of film thicknesses, onset of rippling. Nr, = 50-7500 (mostly turbulent zone). 

The gas velocity at the interface of the laminar sub-layer and the turbulent zone, u, may also be estimated from ... 

The LT 201 (ASR/Komatsugawa/Biolafitte) instrument (Fig. 15) attempts to keep gas bubbles out of the optical path by mounting a cylindrical stainless steel screen around this region and positioning the sensor at a certain angle into a less turbulent zone in the reactor. Hibino et al. [168] and Yamane et al. [471,472]... 

Fig. 23. Schematic design of a biosensor that can be mounted in situ. The biosensor itself sits in a housing and consists of a biocomponent such as one or more immobilized enzymes or cells on top of and in close contact with a suitable type of transducer. A buffer or diluent stream can help to extend the useful dynamic range of the biosensor. The analyte arrives at the biosensor by passing a suitable membrane which enhances selectivity and protects the biosensor. An additional mechanical shield in the form of a mesh, grid or frit may be necessary to assure mechanical stability in the highly turbulent zone...

Rotating cage Used for evaluating inhibitors in oil and gas operations. There are four zones of flow pattern such as homogeneous zone, side-wall-affected zone, turbulent zone and top-cover-affected zone [6,7]... 

---