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Windy Cities

Windy Cities. http://www.youtube.com/watch?v=8NSW9R1IVAk http://www.youtube.com/watch?v=SEBLt6Kd9EY http://www.youtube.com/watch?v=porZ2jOaYew. London Smog. … and now. Then …. What is wind?. Turbulence. Unstable eddies in the wind which disrupt the flow of air.

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Windy Cities

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  1. Windy Cities http://www.youtube.com/watch?v=8NSW9R1IVAk http://www.youtube.com/watch?v=SEBLt6Kd9EY http://www.youtube.com/watch?v=porZ2jOaYew

  2. London Smog … and now Then …

  3. What is wind?

  4. Turbulence Unstable eddies in the wind which disrupt the flow of air http://www.youtube.com/watch?v=1jge03Qls6s http://www.youtube.com/watch?v=HTOl0lTet9A Turbulence is rotational, three dimensional air flow Turbulence quickly turns the energy from moving air into heat

  5. Flow around a single building How does air flow around a building?

  6. Flow around a single building Strong surface winds

  7. Streets far apart Streets close together Flow down Parallel Streets

  8. How does air Flow around Buildings? http://www.youtube.com/watch?v=5lSvDKv7sTg http://www.youtube.com/watch?v=7HUUENCQFto

  9. Wind direction Source of Dye Source www.dapple.org.uk Flow down Parallel Streets

  10. Wind Tunnel Experiments Model scale ~1:400  ~400 times faster than in nature!!! flat roof H/W=1.0 flat roof H/W=0.6 high pitch H/W=0.6 high pitch H/W=1.0

  11. BT Tower NE wind direction

  12. Probability of Wind Nuisance at Eindhoven University Hall to be replaced B. Blocken et al. / Environmental Modelling & Software 30 (2012) 15e34

  13. Computer simulation of whole city air flow • http://www.youtube.com/watch?v=x3w6w0B6pf8

  14. Summary • Urban air flow is complicated! • Swirling flow is generated by buildings • At street level, the flow can even be in the opposite direction to the wind higher up • There can be large gusts at street level which can be annoying or even dangerous • Pollution can be concentrated in areas of low wind speed. • Architects and urban planners try to design buildings to maximise their natural ventilation, and to prevent dangerous air flow around them.

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