# Area weighted or mass weighted average

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 January 31, 2011, 07:13 area weighted or mass weighted average #21 New Member   Amit Chauhan Join Date: May 2010 Location: Chennai, India Posts: 13 Rep Power: 8 thank you sir... thank you very much.

May 3, 2013, 16:10
#22
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Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,209
Rep Power: 19
Quote:
 Originally Posted by jola Area-averaging and mass-averaging will give different results and what you should use depends on what variable you are interested in. For conserved variables like total-pressure you should use mass-averaging, whereas for other variables, like static-pressure, you should use area-averaging. Check out some of the refences mentioned. To make things even more complex another type of averaging often used is flux-averaging. With flux-averaging all gradients are mixed out and a flux-averaged value is the value you would get if you measure at the outlet of an infinently long friction-free pipe put at the boundary. In turbomachinery applications flux-averaging is common, and sometimes you do not flux-average everything, you do flux-averaging circumferentially to mix-out wakes, but you do not do flux-averaging radially because you do not want to mix-out the end-wall boundary layers.
hello
what do you mean by a conserved variable exactly?
is a scalar transport variable conserved?I have mixed up with a conserved variable and a conserved equation.
thank you.
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March 4, 2014, 06:19
#23
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Join Date: Nov 2013
Location: Germany
Posts: 6
Rep Power: 4
Quote:
 Originally Posted by jola Area-averaging and mass-averaging will give different results and what you should use depends on what variable you are interested in. For conserved variables like total-pressure you should use mass-averaging, whereas for other variables, like static-pressure, you should use area-averaging. Check out some of the refences mentioned. To make things even more complex another type of averaging often used is flux-averaging. With flux-averaging all gradients are mixed out and a flux-averaged value is the value you would get if you measure at the outlet of an infinently long friction-free pipe put at the boundary. In turbomachinery applications flux-averaging is common, and sometimes you do not flux-average everything, you do flux-averaging circumferentially to mix-out wakes, but you do not do flux-averaging radially because you do not want to mix-out the end-wall boundary layers.
Dear Sir, I have in my project mixing chamber CO2 with air (with different temperature ) but mass fraction for CO2 very small when try to find static temperature or total temp. by mass - averaging different if I find it by area - averaging, and my project incompressible flow
I interested to find temperature.

 March 4, 2014, 13:37 #24 New Member   adnan Join Date: Nov 2013 Location: Germany Posts: 6 Rep Power: 4 Dear friends, I have in my project mixing chamber CO2 with air (with different temperature ) but mass fraction for CO2 very small when try to find static temperature or total temp. by mass - averaging different if I find it by area - averaging, and my project incompressible flow I interested to find temperature. Thanks in advance

July 8, 2015, 06:15
#25
Member

Shane
Join Date: Oct 2009
Posts: 52
Rep Power: 9
Quote:
 Originally Posted by Jan Rusås ;31045 Regarding the average methode for pressure, you can find that from the energy equation. It should actually be volume flow averaged, but if the density is constant you can use mass flow average. Only if the velocity is near constant, same mass flow at each position, will result in same value for mass flow and area average.
The energy equation is a function of Velocity across the surface area. Should one calculated the Pressure and velocity average over the Surface Area for energy & heat transfer calculations ?

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