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Old   September 19, 2007, 23:45
Default CEL help!
  #1
CC
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Hi All,

I'm trying to define a powerlaw model dynamic viscosity in my material for my transient simulation: μ = μ0*γ^n'1, μ0=0.35, n=0.6.

I created CEL function using the strain rate system variable for γ but CFX-Pre is giving my an error saying some variables should be dimensionless.

Can anyone tell me the correct syntax in creating this CEL expression?

Many Thanks, CC.

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Old   September 20, 2007, 09:05
Default Re: CEL help!
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opaque
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Dear CC,

Your expression does not have units; therefore the complain.

mu0 = 0.35 [units of viscosity]

n = 0.36

mu = mu0 * (sstrnr/(1[s]))^(n-1)

Notice that the shear strain rate is divided by 1[s] scale to prevent the units of mu0 to be a function of "n".. Besides that, there are some bounding issues with power law viscosity models you must deal with.

What happens when the shear strain rate is 0. A divide by zero will occur.

Have you looked at tutorial 11: Non-Newtonian Fluid Flow in an Annulus.. All the correct details are in there.

Opaque.

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Old   September 23, 2007, 22:00
Default Re: CEL help!
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CC
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Hi Opaque,

Where can I find the tutorial 11?

Thanks, CC.
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Old   September 24, 2007, 08:56
Default Re: CEL help!
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opaque
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Dear CC,

It is part of the main documentation.. Select Help in any of CFX-Pre/Solver/Post and search for non Newtonian..

Opaque
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