Reynolds Number Calculation
 

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?

Regards
Ashtonj

See http://www.cfd-online.com/Forums/cfx...umber-cfx.html

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

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?

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 ?

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.

Calculatin Re number in complex Geometries
 

Hi Foamer

do you know if it is possible to calculate the Re number in different parts of a complex geometry using openFoam?

Try the openfoam forum.