Wind effects

Indoors, indicative of a total flooding system outdoors requiring assessment of exposure of nearby hazards, involvement of other combustibles, wind effects and difficulty of extinguishment. 

FIGURE 7.101 Pressure distribution doe to wind effect o) uniform wind velocity profile (6) non-uniform wind velocity profile. 

Static pressure difference between two zones resulting from the wind effect on the building envelope (Fig. 7.108fe). 

Zhoy Y ., and T. Staphopoulos. 1996. Application of two-layer methods for the evaluation of wind effects on a cubic building. ASHRAE Transactions, vol. 102, no. 1. 

This merhod ot ventilation uses extractor fans. A fan will create a negative pressure within the space. With this method, a set flow rate can be achieved, as the fan will overcome the stack and wind effects hence, the system is not at the mercy of the weather. This system causes the inside of the building to be held at a negative pressure, so air will be drawn in from outside or from surrounding spaces that are at a high pressure. 

As outlined earlier, in multizone models, perfect mixing is assumed in the individual zone. The spatial distribution of velocities, contaminant concentrations, and air temperatures in a zone can be determined only by using CFD. On the other hand, wind effects are easily accounted for in multizone models, and unsteady-state simulation is normally performed. On the combined use of the two methods, see Schaelin et al.--... 

T. V. Lawson. Wind Effect on Buildings. Applied Science Publishers, London, 1980. 

This appendix is a summary of the woiit published in the so-called Green Book (1989). Possible effects of explosions on humans include blast-wave overpressure effects, explosion-wind effects, impact from fragments and debris, collapse of buildings, and heat-radiation effects. Heat-radiation effects ate not treated here see Chapter 6, Figure 6.10 and Table 6.6. 

Termination A suitable design and location of the flue terminal is essential for optimum performance. This is primarily to counter adverse wind effects. 

The wind effect may assist or oppose the natural-draft flue, causing increased draft up the flue, or downdraft. For this reason, it is important to minimize their effects... 

If the products of combustion can be diluted so that the carbon dioxide content is not greater than 1 per cent it is permissible to discharge them at ground level. This is the principle of the system shown in Figure 19.7, in which fresh air is drawn in to dilute the flue products which are discharged preferably on the same wall as the inlet to balance against wind effects. It is essential to interlock the airflow switch with the burner controls. 

When both wind and temperature difference act on ventilation openings, the result is very complex, but a reasonable approximation of flow rate is made by taking the higher of the two individual flow rates. This means that we can, for ventilation design purposes, generally ignore wind effects and design on temperature difference only, since wind effects can be assumed only to increase the ventilation rate. 

Abnormal wind effects can be anticipated due to surrounding higher buildings ... 

For simplicity of the model, it is assumed that the natural convection, radiation, and ionic wind effect are ignored. The ignorance of the radiation loss from the spark channel during the discharge may be reasonable, because the radiation heat loss is found to be negligibly small in the previous studies [5,6]. The amount of heat transfer from the flame kernel to the spark electrodes, whose temperature is 300 K, is estimated by Fourier s law between the electrode surface and an adjacent cell. 

A passive system is much the same as an active system with the exception of the fan. A passive system relies only on stack and wind effects to produce the pressure field. As can be seen in Table 31.1, passive systems do not always reduce radon concentrations to acceptable levels, but careful design and installation may improve the effectiveness of a passive system. 

Because of the importance of the dynamic pressure q in drag or wind effects and target tumbling, it is often reported as a blast wave property. In some instances drag specific impulse i, defined as... 

All hydrocarbon fire mechanisms and estimates will be affected by to some extent of flame stability features such as varying fuel composition as lighter constituents are consumed, available ambient oxygen supplies, ventilation patterns, and wind effects. Studies into these effects have generally not progressed to the level where precise estimations can be made without scale model tests or on site measurements. 

Oncoming or cross wind effects may reduce the performance of water monitors. When winds of 8 km/hr (5 mph) are present they may reduce the range of water spray by as much as 50%. Consideration should be given to the placement of monitors when the normal wind speed is such to cause performance effects. 

Deacon s intention was to separate the viscosity effect from the wind effect, so that the new model would be able to describe the change of via due to a change of water or air temperature (i.e., of viscosity) at constant wind speed. Deacon concluded that mass transfer at the interface must be controlled by the simultaneous influence of two related processes, that is, by the transport of chemicals (described by molecular diffusivity Dia), and by the transport of turbulence (described by the coefficient of kinematic viscosity va). Note that v has the same dimension as Dia. Thus, the ratio between the two quantities is nondimensional. It is called the Schmidt Number, Scia ... 

Two principal mechanisms that may be responsible for mass loss from red giants are considered shock wave-driven winds and radiatively (dust)-dr iven winds. Effect of the periodic shocks accompanying nonlinear oscillations of red giants is most prominent in the outer layers of the stellar atmosphere where shocks are able not only to expel gas but also increase gas density so that some molecular components become supersaturated. In 0-rich stars the most abundant condensible species are silicon monoxide and iron, whereas in C-rich stars these are carbon, silicon carbide and iron. 

M0 is a numerical factor that is specific for the crystal structure. The second term in brackets stems from what is called the vacancy wind effect. We note that D for AO-BO (oxide) interdiffusion under the condition d i0 = 0 is analogous to D for A-B (alloy) interdiffusion when djuv = 0 and vacancy equilibrium prevails throughout the alloy. 

The authors in association with Oxford University, undertook research, to determine how the arrangement of heat exchanger bundles at the base of a tower affects the tower s internal flow and its sensitivity to cross winds. To learn more about these effects, experiments were conducted with model towers in which heat exchanger bundles were represented by gauze screens. Two types of tests were conducted The first study involved a tower flow in the absence of cross winds which was made at high Reynolds numbers. The second was a study of cross-wind effects made at much reduced Reynolds numbers in a 4m by 2m wind tunnel. 8 refs, cited. 

Wind Effects on the Operation of Natural-Draft Cooling Towers Zembaty, W. 

Wong, K.C., and Moses-Hall, J.E. (1998) On the relative importance of the remote and local wind effects on the subtidal variability in a coastal plain estuary. J. Geophys. Res. 103, 18393-18404. 

Because the spheres used for the cover are light weight, they can easily be blown by the wind into one comer of the liquid pool they are supposed to cover. The larger the pool to be covered by ping-pong balls the more necessary it is to consider wind effects in designing the system. 

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