Turbulence intensity, atmospheric

FIGURE 10.9. The ratio of the turbulent burning velocity to the laminar burning velocity as a function of the ratio of the integral scale to the laminar-flame thickness, for various turbulence intensities, for stoichiometric propane-air flames at atmospheric pressure, and initially at room temperature [137],... 

However, considering the atmospheric boundary layer profiles as discussed above, the local velocity at the rack may be considerably lower, especially for test sites in either forested or urban areas. This result emphasizes the need to measure local wind speeds at atmospheric corrosion test sites, at the test rack height. Turbulence intensity measurements might be useful as well. 

The present model experiments are concerned with an important category of industrial hazards, i.e., with the problem of flame acceleration in atmospheric gas/air explosions due to obstacles in the flame path. As a system simulation of industrial structures, planar grids consisting of cylindrical parallel rods inserted in a square, cross-sectional channel were chosen for the experiments. The variation of the rod diameter and the number of rods allowed investigation of the influence of the turbulence properties (turbulence intensities and macro length scales) on flame acceleration. 

Fig. 3.14 The turbulence intensity effect on the turbulent flame velocity in H2 + air + water steam mixture at 393M00 K temperature at atmospheric pressure...

Direct measurements of the intensity of atmospheric turbulence also can be used to estimate cTy and Cz, both of which are increasing functions of the variability of air velocity in the y and z directions, respectively (Fig. 4.29). Pasquill (1961) proposed the following measures of turbulent intensity in the lateral and vertical directions. 

Equation (4.16) can be rearranged to calculate source strength (Q) of an atmospheric plume from an observed environmental concentration (C). In the absence of measurements of turbulent intensity, the formulae of Table 4.6 can be used to estimate values for Oy and (Note that Fig. 4.28 could... 

Pasquill defined six stabihty classes ranging from highly stable, low-turbulence Class F, to unstable, highly turbulent Class A, and he identified the surfece wind speed, intensity of solar radiation, and nighttime sky cover as being the prime factors controlling atmospheric stabihty. PasquiU then correlated observations of the behavior of plumes in terms of their dispersion with the... 

The above discussion holds for dispersion by atmospheric turbulence. In addition, a momentum release of fuel sometimes generates its own turbulence, e.g., when a fuel is released at high pressure in the form of a high-intensity turbulent jet. Fuel mixes rapidly with air within the jet. Large-scale eddy structures near the edges of the jet entrain surrounding air. Compositional homogeneity, in such cases, can be expected only downstream toward the jet s centerline. 

Wind vectors (speed and direction), and Dispersive effects (intensity of atmospheric turbulence). 

Normally the wort is boiled vigorously for 1.5—2 h at atmospheric pressure. This vigorous boiling causes a strong turbulence whereby an even, intensive flow of bubbles rises from the heating area at the bottom of the kettle up through the wort. To attain a fine precipitation, the wort pH must be around the isoelectric point of the proteins, ca 5.0—5.2. 

The role of the World Ocean in the global cycle of C02 is mainly manifested through the process of its exchange at the atmosphere-ocean boundary. The intensity of ocean-atmosphere gas exchange is determined by the dynamic and diffusive behavior of the turbulent layers of water and air near the interface. Here numerous physical schemes appear which reflect the situations of wave formation, their collapse, and the... 

As described above, wet and dry particle-bound deposition are likely important for the accumulation of the higher chlorinated PCDD/Fs in aerial vegetation. The accumulation of particle-bound PCDD/Fs in plants is a function of a myriad of factors. The deposition rate itself is influenced by the particle size spectrum in the atmosphere and the distribution of the PCDD/Fs on the different particle size fractions, and further by the atmospheric turbulence, the canopy and plant properties, and the frequency and intensity of precipitation. The retention of the contaminants on the plant surface depends on the degree to which the particles are permanently retained on the plant and, for those particles which are not retained, the degree of transfer of PCDD/Fs from the particles to the plant cuticle. This is a very complex system that is not yet well understood. One approach that... 

Typical measured values of (8 /v) 2 are on the order of 10 s-1, so turbulent shear coagulation is significantly slower than Brownian for submicrometer particles, and the two rates become approximately equal for particles of about 5 pm in diameter (Figure 13.A.2). The calculations indicate that coagulation by Brownian motion dominates the collisions of submicrometer particles in the atmosphere. Turbulent shear contributes to the coagulation of large particles under conditions characterized by intense turbulence. 

Measurements of wind velocity components, such as depicted in Figure 16.1, are important in characterizing atmospheric turbulence. Certain statistical properties of the tur-bulence can be extracted from such records. The intensity of turbulence is related to u[ or (Ty (no summation), the variance of the velocity distribution of the /th component about its mean value. The values bear a direct relation to the diffusing power of the atmosphere. Two other useful properties are the standard deviations of the fluctuations in the horizontal direction of the wind, 00, and the vertical direction of the wind a. It is important to realize that Ou, (7(51, and depend on the sampling and averaging times inherent to a velocity record such as that shown in Figure 16.1. 

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