Wind force estimating

Beaufort scale The scale used for estimating and reporting wind forces, in which 0 is calm (velocity less than 0.5 m s" ) and 12 is a hurricane. 

Soil-derived particle fluxes are too much dependent on local conditions and the prevailing wind force to provide reliable estimates. Peterson and Junge (1971) adopted an estimate by Wadleigh (1968) for the emission of... 

In the absence of hydraulic or wind forces, the water becomes quiescenf but natural or free convection processes remains operative. Driven by bottom residing thermal or concentration gradients. Equations 12.14 and 12.15 may be used for estimating these low-end MTCs. The chemical diffusion coefficient in the porewaters of the upper sediment layer is the key to quantifying the sediment-side MTC. Use Archie s law. Equation 12.18, to correct the aqueous chemical molecular diffusivity for the presence of the bed material. Bed porosity is the key independent variable that determines the magnitude of the correction factor. See Table 12.7 for typical porosity values in sedimentary materials. Eor colloids in porewaters. Equation 12.18 applies as well. The Stokes-Einstein equation (Equation 12.19) is recommended and some reported particle Brownian diffusion coefficients appear in Tables 12.9 and 12.10. Under quasisteady-state conditions, Equation 12.23 is appropriate for estimating the bed-side MTCs. 

By forced convection The factors that can influence the temperature of the enclosure, installed outdoors are wind and snow, other than forced cooling. But their effect on actual cooling may be small. Sometimes this happens and sometimes not. It is better to ignore this effect when estimating various thermal effects. Natural convection and radiation will take account of this. 

The drag coefficient for an antomohile body is typically estimated from wind-tunnel tests. In the wind tunnel, the drag force acting on a stationaiy model of the vehicle, or the vehicle itself, is measured as a stream of air is blown over it at the simulated vehicle speed. Drag coefficient depends primarily on the shape of the body, but in an actual vehicle is also influenced by other factors not always simulated in a test model. 

Under some wind conditions, a portion of the warm moist air leaving the tower may recirculate back through tire tower inlet and thus degrade performance. Forced-draft towers have recirculation rates that are about double those of induced-draft towers. Both water loading and tower height play the dominant role in- recirculation. Correlations exist in the literature for defining the effects of these parameters, and corrections can be applied to the wet-bulb temperature [2,3], Cooling tower fabricators can supply data to estimate the severity of the problem. 

There are two types of convection, free and forced (Holman, 2009 Incropera et al., 2007 Kreith and Bohn, 2007). Free (natural) convection occurs when the heat transferred from a leaf causes the air outside the unstirred layer to warm, expand, and thus to decrease in density this more buoyant warmer air then moves upward and thereby moves heat away from the leaf. Forced convection, caused by wind, can also remove the heated air outside the boundary layer. As the wind speed increases, more and more heat is dissipated by forced convection relative to free convection. However, even at a very low wind speed of 0.10 m s-1, forced convection dominates free convection as a means of heat loss from most leaves (0.10 m s-1 = 0.36 km hour-1 = 0.22 mile hour-1). We can therefore generally assume that heat is conducted across the boundary layer adjacent to a leaf and then is removed by forced convection in the surrounding turbulent air. In this section, we examine some general characteristics of wind, paying particular attention to the air boundary layers adjacent to plant parts, and introduce certain dimensionless numbers that can help indicate whether forced or free convection should dominate. We conclude with an estimate of the heat conduction/convection for a leaf. 

The resistance rdc is determined by the effects of mixing forced by buoyant convection (as a result of surface heating of the ground and/or lower canopy) and by penetration of winds into canopies on the sides of hills. The resistance (insm-1) is estimated from... 

For live loads, consideration must be given to the added force from wind and snow. Simplified data for estimating these live loads appear in Table 8-4. Additional data on weather can be obtained from the U.S. Weather Bureau. A useful summary of temperature range and wind characteristics for 88 cities in the United States is given in Perry s "Chemical Engineers Handbook, 3d ed., p. 46. 

Many chemicals escape quite rapidly from the aqueous phase, with half-lives on the order of minutes to hours, whereas others may remain for such long periods that other chemical and physical mechanisms govern their ultimate fates. The factors that affect the rate of volatilization of a chemical from aqueous solution (or its uptake from the gas phase by water) are complex, including the concentration of the compound and its profile with depth, Henry s law constant and diffusion coefficient for the compound, mass transport coefficients for the chemical both in air and water, wind speed, turbulence of the water body, the presence of modifying substrates such as adsorbents in the solution, and the temperature of the water. Many of these data can be estimated by laboratory measurements (Thomas, 1990), but extrapolation to a natural situation is often less than fully successful. Equations for computing rate constants for volatilization have been developed by Liss and Slater (1974) and Mackay and Leinonen (1975), whereas the effects of natural and forced aeration on the volatilization of chemicals from ponds, lakes, and streams have been discussed by Thibodeaux (1979). 

---