Velocity distribution, atmospheric

Collisional ionization can play an important role in plasmas, flames and atmospheric and interstellar physics and chemistry. Models of these phenomena depend critically on the accurate detennination of absolute cross sections and rate coefficients. The rate coefficient is the quantity closest to what an experiment actually measures and can be regarded as the cross section averaged over the collision velocity distribution. 

In any liquid flowing down a surface, a velocity profile is established with the velocity increasing from zero at the surface itself to a maximum where it is in contact with the surrounding atmosphere. The velocity distribution may be obtained in a manner similar to that used in connection with pipe flow, but noting that the driving force is that due to gravity rather than a pressure gradient. 

Muller, J.-F. Geographical Distribution and Seasonal Variation of Surface Emissions and Deposition Velocities of Atmospheric Trace Gases, J. Geophys. Res., 97, 3787-3804 (1992). 

For this purpose, a new type of "unified model atmospheres" has been developed at the Munich Observatory by R. Gabler (1986) and A. Wagner (1986) in cooperation with J. Puls, A. Pauldrach and R.P. Kudritzki. These NLTE model atmospheres are spherically extended, in radiative equilibrium, and include the density and velocity distribution of radiation driven winds. The spectra of H and He lines are then calcu-... 

Dusty winds over deserted territories carry air-born particles that influence the wind profile. A similar situation can be observed over the storming ocean when air-born droplets sized from 0.1 to 1 mm are lifted to some elevations thus distorting the wind velocity distribution [655], Accounting for the wind and droplet motion, and finally for their evaporation, provides an important estimate of the ocean heat flux to the Earth atmosphere [70],... 

If all uncertainties like initial spatial distribution of NSs, their kick velocity distribution, characteristics of emission (atmospheric effects etc.), mass spectrum of NSs are fixed, then Log N - Log S distribution of close-by NSs can be a powerful tool to put constraints on models of thermal evolution of NSs. 

One can expect (see fine print further) that the greater diffusivity of the counter-ion layer as compared to that established in Helmholtz model, would only affect the velocity distribution profile of the displacement of individual fluid layers in the direct vicinity of the solid surface. The experimentally observed velocity of the mutual motion of the phases with respect to each other, v0, determined, as in Helmholtz model, by the potential change significantly (curve 2 approaches the same limiting value as curve 7 ). This is also confirmed by the fact that the distance between the capacitor plates, 8, which is the only parameter defining the geometry of the system in the Helmholtz model, is not present in the final expression.4 The thickness of the ionic atmosphere, k 1, may be used as the parameter closest to the distance 8, i.e. 8=1/k. 

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. 

Electrons are the origin of most of the chemical reactions happening at atmospheric pressure plasma based processes hence, their energy distribution plays an important role in plasma chemical reactions. The electron velocity distribution function (EVDF) in our system is determined on the basis of the emission of nitrogen molecule (equations 1-13). For this... 

Mtiller JF (1992) Geographical-distribution and seasonal-variation of surface emissions and deposition velocities of atmospheric trace gases. J Geophys Res Atmos 97 3787-3804... 

Physical (scale) models employing wind tunnels or water channels have been used for dense gas dispersion simulation, especially for situations with obstructions or irregular terrain. Exact similarity in all scales and the re-creation of atmospheric stability and velocity distributions are not possible— very low air velocities are required to match large scale results. Havens et al (1995) attempted to use a 100-1 scale approach in conjunction with a finite element model. They found that measurements from such flows cannot be scaled to field conditions accurately because of the relative importance of the molecular difiusion contribution at model scale. The use of scale models is not a common risk assessment tool in CPQRA and readers are direaed to additional reviews by Mcroncy (1982), and Duijm et al. (1985). 

A vector field i x,y, z) denotes a volume in space in which any point (x,y, z) can be given a vector value f x,y,z). A vector field can be illustrated by the wind velocity distribution v(x,y, z) in the atmosphere at a given time. 

A particularly difficult aspect of the problem of diffusion of atmospheric pollution is the determination of the height to which a buoyant plume with an initial exit velocity will rise. Plume rise, which is defined as the distance between the top of the stack and the axis of the centroid of the pollutant distribution, has been found to depend on ... 

The deposition velocities depend on the size distribution of the particulate matter, on the frequency of occurrence and intensity of precipitation, the chemical composition of the particles, the wind speed, nature of the surface, etc. Typical values of and dj for particles below about 1 average residence time in the atmosphere for such particles is a few days. 

Figure 4-4 shows a typical system under positive pressure. It differs from the vacuum system in that the material enters from one source and is distributed directly to several tanks. In this case no cyclone separator is used the air laden with solids enters the process bins directly. The decrease in velocity of the stream and its change in direction will cause most of the solids to drop out. For this system each receiver must have a filter to remove the remaining solids. Note that the blower is placed at the air entrance, instead of after the filter as in the vacuum system. Should a bag in the fiber filter break, no dust will get into the blower or its motor. Another advantage is that no contaminants from the atmosphere can enter the system when it is under positive pressure, except through the air inlet system. 

---