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February 7, 2010, 09:18 
Dimensional Analysis question

#1 
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Hi there,
Flow over a weir in an open rectangular channel is given by the relationship:[latex]Q=\phi(H,V,g,B)[/latex] where: Q is the flowrate (m^3/s), B width of the weir (m), Hthe height of the water above the weir(m), V the mean velocity of water (m/s), g gravity (m/s^2) Would you help me find a relationship between Q and these variables please? I keep getting really stuck because I know the equation is actually: [latex]Q=KB\sqrt{\dfrac{2}{3g}}(H+\dfrac{v^2}{2})^{3/2}[/latex] 

February 7, 2010, 17:28 

#2 
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Glenn Horrocks
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The forum cannot render latex. You will have to insert images of the equations.
But I can't see your point. You just stated the equation so why do you need to find the relationship? Is there something wrong with the equation you stated? These questions are best answered by you in your work anyway as they are specific to your work. 

February 8, 2010, 09:19 

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February 8, 2010, 18:15 

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February 9, 2010, 06:59 

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Best regards, kingjewel1 

February 9, 2010, 07:41 

#6 
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Glenn Horrocks
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So your question is about dimensional analysis, not CFD.
Here's how I would do it: http://en.wikipedia.org/wiki/Buckingham_%CF%80_theorem 

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