In normal life of people practically does not meet such concept as aerodynamic shadow. But all people meet this phenomenon daily, one may say, that we live with this concept. If to speak simple language, the aerodynamic shadow is the zone of stagnation of air arising in the environment of vortex perturbations, obrazovyvayushchikhsya cart of big buildings and other objects as a result of differences on height. Practically this phenomenon is connected with the device of mechanical ventilation.
Drafts always walk on the street with skyscrapers, it also is aerodynamics phenomenon. And in this vortex environment there are sites where air costs motionless, some kind of "air pockets". This phenomenon is called aerodynamic shadow.
Theoretical justification of aerodynamic shadow
There are certain borders of distribution of aerodynamic shadow for the separate building with narrow facade, with wide facade and for group of buildings (objects) located consistently. It is very important to know it for calculation of stack height of mechanical ventilation or even fireplace.
In stagnant zone air does not mix up, according to draft in pipe will not be, and there can be boomerang effect when smoke and street air go on ventilation system in the building.
Rules of creation of aerodynamic shadow
Except building height, force and the direction of wind is of great importance. As the aerodynamic shadow arises only near zavetrenny wall of the building. There are formulas the calculating points of highest concentration of shadow and separately from the zavetrenny party, for one pipe or ventilating exit.
In certain cases if there is creation of aerodynamic shadow for heights 4 and 8 meters, then for height of 6 meters it is possible to obtain necessary data and to construct aerodynamic shadow by interpolation method (calculation of intermediate values on known).
Using the developed techniques, it is possible to understand how to build and find borders of aerodynamic shadow. It gives the chance to find completely shaded sites of roof on which placement of flues and ventkanal is inexpedient. There are sources in which the dependence of concentration of hazardous substances in air from stay in borders of aerodynamic shadow is considered.
The format of this popular article does not allow to provide scientific calculations.
Influence of aerodynamic shadow on irritants in the atmosphere
On height, even at various speeds of the running air flow, borders of aerodynamic shadow do not exceed object, and here on extent behind the building there are essential distinctions depending on building configuration.
At the wrong creation of borders of zone of shadow the emission of hazardous substances in pritenevy space can exceed allowable limits of pollution considerably.
In case the smoke pipe is removed out of limits of borders of shadow aerodynamic zone, concentration of polluting substances in the surrounding atmosphere decreases in 6 and more times.
For private construction at conclusion of smoke pipes to roof it is necessary to consider differences of height of own building (roof at the different levels) and also height of the neighboring buildings and distance from them.