Wind engineering

Wind engineering analyzes effects of wind in the natural and the built environment and studies the possible damage, inconvenience or benefits which may result from wind. In the field of structural engineering it includes strong winds, which may cause discomfort, as well as extreme winds, such as in a tornado, hurricane or heavy storm, which may cause widespread destruction. In the fields of wind energy and air pollution it also includes low and moderate winds as these are relevant to electricity production resp. dispersion of contaminants.

Wind engineering draws upon meteorology, fluid dynamics, mechanics, Geographic Information Systems and a number of specialist engineering disciplines including aerodynamics, and structural dynamics. The tools used include atmospheric models, atmospheric boundary layer wind tunnels and computational fluid dynamics models.

Wind engineering involves, among other topics:

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

Contents

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 (United Kingdom)|[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:[1][2]

\ v_z = v_g \cdot \left( \frac {z} {z_g} \right)^ \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.[3] The wind gradient can create a large bending moment in the shaft of a two bladed turbine when the blades are vertical.[4] The reduced wind gradient over water means shorter and less expensive wind turbine towers can be used in shallow seas.[5]

For wind turbine engineering, wind speed variation with height is often approximated using a power law:[3]

\ v_w(h) = v_{ref} \cdot \left( \frac {h} {h_{ref}} \right)^ a

where:

\ v_w(h) = velocity of the wind at height h [m/s]
\ v_{ref} = velocity of the wind at some reference height h_{ref} [m]
\ a = Hellman exponent (aka power law exponent or shear exponent) (~= 1/7 in neutral flow, but can be >1)

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 a dominant load in the analysis and design of all long-span cable bridges.

See also

References

  1. ^ Crawley, Stanley (1993). Steel Buildings. New York: Wiley. pp. 272. ISBN 0471842982. 
  2. ^ Gupta, Ajaya (1993). Guidelines for Design of Low-Rise Buildings Subjected to Lateral Forces. Boca Raton: CRC Press. pp. 49. ISBN 0849389690. 
  3. ^ a b Heier, Siegfried (2005). Grid Integration of Wind Energy Conversion Systems. Chichester: John Wiley & Sons. pp. 45. ISBN 0470868996. 
  4. ^ Harrison, Robert (2001). Large Wind Turbines. Chichester: John Wiley & Sons. pp. 30. ISBN 0471494569. 
  5. ^ Lubosny, Zbigniew (2003). Wind Turbine Operation in Electric Power Systems: Advanced Modeling. Berlin: Springer. pp. 17. ISBN 354040340X. 

External links