Wind engineering

Wind engineering is a field of structural engineering devoted to the analysis of wind effects on the natural or built environment to protect it from possible damage. It includes strong winds which may cause discomfort as well as extreme winds such as tornadoes, hurricanes and storms which may cause widespread destruction [ [http://www.ecs.csun.edu/~shustov/Wind_Engineering_Directory.html Wind Engineering Directory] ] .

Wind engineering draws upon meteorology, aerodynamics,Geographic Information System, Wind energy, Air Pollution and a number of specialist engineering disciplines. The tools used include climate models, atmospheric boundary layer wind tunnels and numerical models. It involves, among other topics, how wind impacting buildings must be accounted for in engineering.

Wind engineering may be considered closely related to earthquake engineering and explosion protection.

History

Wind Engineering as a separate discipline can be traced to the UK in the 1960s, when informal meetings were held at the National Physical Laboratory, the Building Research Establishment and elsewhere.

Wind loads on buildings

The design of buildings must account for wind loads, and these are affected by wind shear. For engineering purposes, a power law wind speed profile may be defined as follows:cite book | last = Crawley | first = Stanley | title = Steel Buildings | publisher = Wiley | location = New York | year = 1993 | isbn = 0471842982 | pages = p. 272 ] cite book | last = Gupta | first = Ajaya | title = Guidelines for Design of Low-Rise Buildings Subjected to Lateral Forces | publisher = CRC Press | location = Boca Raton | year = 1993 | isbn = 0849389690 | pages = p. 49]

: v_z = v_g cdot left( frac {z} {z_g} ight)^ frac {1} {alpha}, 0 < z < z_g

where:

: v_z = speed of the wind at height z : v_g = gradient wind at gradient height z_g : alpha = exponential coefficient
Typically, buildings are designed to resist a strong wind with a very long return period, such as 50 years or more. The design wind speed is determined from historical records using Extreme_value_theory to predict future extreme wind speeds.

Wind turbines

Wind turbines are affected by wind shear. Vertical wind-speed profiles result in different wind speeds at the blades nearest to the ground level compared to those at the top of blade travel, and this in turn affects the turbine operation.cite book | last = Heier | first = Siegfried | title = Grid Integration of Wind Energy Conversion Systems | publisher = John Wiley & Sons | location = Chichester | year = 2005 | isbn = 0470868996 | pages = p. 45] The wind gradient can create a large bending moment in the shaft of a two bladed turbine when the blades are vertical. [cite book | last = Harrison | first = Robert | title = Large Wind Turbines | publisher = John Wiley & Sons | location = Chichester | year = 2001 | isbn = 0471494569 | pages = p. 30] The reduced wind gradient over water means shorter and less expensive wind turbine towers can be used in shallow seas.cite book | last = Lubosny | first = Zbigniew | title = Wind Turbine Operation in Electric Power Systems: Advanced Modeling | publisher = Springer | location = Berlin | year = 2003 | isbn = 354040340X | pages = p. 17]

For wind turbine engineering, an exponential variation in wind speed with height can be defined relative to wind measured at a reference height of 10 meters as:

: v_w(h) = v_{10} cdot left( frac {h} {h_{10 ight)^ a

where:

: v_w(h) = velocity of the wind at height, h [m/s] : v_{10} = velocity of the wind at height, h_{10} = 10 meters [m/s] : a = Hellman exponent

Significance

The knowledge of wind engineering is used to analyze and design all high rise buildings, cable suspension bridges and cable-stayed bridges, electricity transmission towers and telecommunication towers and all other types of towers and chimneys. The wind load is the dominant load in the analysis of many tall buildings. So wind engineering is essential for the analysis and design of tall buildings. Again, wind load is the dominant load in the analysis and design of all cable bridges, especially the cable bridges which contain rail lines.

Specializations

*Hurricane engineering
*Wind tunnel testing
*Vibration control

References

External links

* [http://www.iawe.org/ International Association of Wind Engineering]
* [http://www.aawe.org/ American Association of Wind Engineering]
* [http://www.ukwes.bham.ac.uk/ UK Wind Engineering Society]


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