When the Wind Blows

Even when the building as a whole is maintained under positive pressure, there is always some location (for example, the outdoor air intake) that is under negative pressure relative to the outdoors. Entry of contaminants may be intermittent, occurring only when the wind blows from the direction of the pollutant source. The interaction between pollutant pathways and intermittent or variable driving forces can lead to a single source causing lAQ complaints in areas of the building that are distant from each other and from the source. 

When the wind blows past an obstacle, the streamlines of air flow diverge to pass round it. Particles carried in the wind tend to carry straight on and may impact on the obstacle. The efficiency of impaction C, is defined as the ratio of the number of impacts to the number of particles which would have passed through the space occupied by the obstacle if it had not been there. If vg is the velocity of deposition relative to the profile area of the obstacle, then C = vglux where ux is the free stream air velocity. C, is thus analogous to Cd, the drag coefficient of the obstacle. 

Okay, let s give this equation a test drive. What is the pressure differential across a flat roof having an area of 240 m2 when the wind blows at 25.0 m/s The density of air is 1.29 kg/m3. 

Although, as we have already stressed, analogies between the macroscopic and the molecular world often lead to misunderstandings and must be used carefully, it is tempting to compare the relationship between chirality and motion in Feringa s systems with that seen in a macroscopic example the windmill. When the wind blows at the vanes of a windmill, its rotor immediately knows which direction to rotate in. When blown at by the same wind, two enantiomeric windmills will rotate in opposite directions, and if the vanes were symmetric with respect to the axis of rotation, the windmill just... 

The technique of gazing should to be practiced before hand. An easy way is to sit on a lawn and relax your vision till you can see all the leaves of grass at the same time. When the wind blows even a little, you will immediately see the very few leaves of grass move. It is the same vision used in mushroom picking. 

The maximum pull on the guy wire occurs when the wind blows along that wire. Each wire must be designed to take care of the entire wind reaction at the collar. 

Stake the upright twig in the ground, perhaps in a garden, about a few inches deep. The ends of the husks should not touch the ground. When the wind blows, the little cornhusks of your Natural Wind Sock will twirl, wiggle, and float in the same direction. 

Swine have a fenfe of touch as well as of fmeil at the end of their nofe, which they ufe as a hand, both to root up the foil, -and to turn over and examine objects of food, fomewhat like the probofeis of an elephant. As they require fiielter from the cold in this climate, they have learnt to collefl ftraw in their mouths to make their neft, when the wind blows cold and to call their companions by repeated cries to affift in the work, and add to their warmth by their numerous bed-fellows. Hence... 

Reviewers lavished praise on When the Wind Blows. British TV pro-... 

Raymond Briggs, When the Wind Blows (London Penguin 1982), back cover. 

Although a flow in the down-wind direction is easy to understand, density structure and rotation of the earth make it more complicated. To simplify our discussion, let us consider the rectangle bay which is very small and has a uniform depth. It is assumed that Coriohs force and stratification effect can be neglected. When the wind blows over this bay, it generates a shear stress at the sea surface. The surface water moves in response to the wind-shear stress the water surface of the leeward side becomes higher and the windward side becomes lower (see Fig. 32.7). If the water pressiues at the seabed are compared at this time, the water pressure of the leeward will become high because of the effect of wind stress. As a result, a flow which returns to the upwind direction occurs at the seabed. Consequently, a vertical circulation, for which the direction of the flow are opposite at the surface and bottom, occurs. In this mechanism, the water near the seabed as well as the surface responds to a wind in comparatively short time, and moves to the upwind direction. 

Walsh, N. (2002). When the wind blows. In S. Balmukhanov, G. Raissova, T. Balmukhanov (Eds.), Three generations of the Semipalatinsk affected to the radiation. Almaty Saskhy. 

Structures other than bridges are often subjects for potential Strouhal-Karman difficulties. These include high smokestacks and tall buildings. The St. Louis Arch (the Gateway to the West) was questioned from this point of view. Model tests and calculations performed by den Hartog at MIT revealed that the arch would be in trouble at wind velocities of 60 10 mph when the wind blows from due north or south 5°. As a matter of safety, the arch has been instrumented to monitor its vibration and people are not allowed to go up into the arch if the wind velocity exceeds 40 mph. 

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