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CC September 19, 2007 23:45

CEL help!
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.

opaque September 20, 2007 09:05

Re: CEL help!
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.


CC September 23, 2007 22:00

Re: CEL help!
Hi Opaque,

Where can I find the tutorial 11?

Thanks, CC.

opaque September 24, 2007 08:56

Re: CEL help!
Dear CC,

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


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