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Old   January 17, 2011, 20:33
Exclamation Reynolds Number Calculation
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Ashkan Javadzadegan
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Hi all

I am confused about value of Reynolds Number shown in CFX-Solver Output file.

I simulated a laminar flow in a constricted pipe which diameter of the non-constricted section is 20 mm. At Inlet of pipe, streamwise and spiral velocity profiles are applied as Inlet boundary condition as below:

Streamwise Velocity Profile: 2*0.0875 [m/s]*(1-(r/R)^2)
Spiral Velocity Profile: 1.46 [1/s]*r

Density and Viscosity are 1060 [kg/m^3]and 0.00371 [pa.s].

When I calculate Reynolds number at Inlet, it becomes 500 while in CFX-Solver Output text file, Reynolds number is mentioned as 1900.

Does anybody know how CFX calculate Reynolds number?

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Ashtonj
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Old   January 18, 2011, 03:52
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Lance
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See Calculation of Reynolds Number In CFX
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Old   February 16, 2011, 06:36
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hi,
i want to calculate the Reynolds number of exhaust gas with a given temperature(c) and massflow(g/s).
What is the fastest way?
thanks in advance
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Old   February 16, 2011, 06:44
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um... the fastest way? Why not use the definition of Reynolds number?
Re = density scale*length scale*velocity scale/viscosity scale
Or are you comparing against some other definition of Re?
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Old   February 16, 2011, 06:53
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thanks for the reply man.

isn't it density * velocity * diameter of the pipe / viscosity ?

but then the next problem is that i don't know how to calculate the density of the exhaust gas and the viscosity ?
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Old   February 16, 2011, 12:08
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So you are modeling pipe flow? Then the length scale is usually the diameter of the (circular) pipe.

To get the density and viscosity you could use areaAve(density)@outlet and areaAve(viscosity)@outlet, but again, it depends on what you are comparing with.
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Old   October 14, 2013, 10:50
Default Calculatin Re number in complex Geometries
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Ali
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Hi Foamer

do you know if it is possible to calculate the Re number in different parts of a complex geometry using openFoam?
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Old   October 14, 2013, 17:26
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Try the openfoam forum.
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