Effects of Building Height on Wind Speed

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Anonymous Poster	Effects of Building Height on Wind Speed 12/15/2010 8:41 AM
	A square building is 5 metres tall, the wind is blowing west - east at 5.0 metres per second. Directly 'behind' the building (i.e. on the east side) the wind speed will be very low. At what distance behind the building will the wind speed be back to 5.0 metres per second? Is there a physics law that calculates this?
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Effects of building height on wind speed 12/15/2010 8:50 AM
	The physics is called aerodynamics. The answer to how far depends upon whether the 5m-high building is a flagpole or a huge square-plan office block, and where in the slipstream the velocity is measured perpendicular to the wind direction. The thing is best visulaised by carrying out smoke tests on a model in a wind tunnel. The thing to do is to make sure that the Reynolds numbers are the same for the model and for the intended full-size building; the flows on the model will then be equivalent to the real thing. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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kramarat Guru Join Date: Jun 2008 Location: Raleigh, NC USA Posts: 13529 Good Answers: 468	#2 In reply to #1 Re: Effects of building height on wind speed 12/15/2010 9:01 AM
	Just passing through, GA. __________________ Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. Ben Franklin
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MoronicBumble Guru Join Date: May 2010 Posts: 570 Good Answers: 55	#3 Re: Effects of building height on wind speed 12/15/2010 11:07 AM
	Is there a physics law that calculates this? No, there are several physics laws involved in aerodynamics. PW's answer is very good. In sailing, the rule of thumb is that the wind shadow of a sail extends 4-5 mast heights downwind. If you search on wind shadow, you will find more info as it affects windmills, etc. __________________ Si hoc signum legere potes, operis boni in rebus Latinis alacribus et fructuosis potiri potes!
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