Learning Forum

[ALEXANDRE COSTA]

Hi,

Does anybody know the sintax error in the following fluent expression :

mu_infinity + (mu_zero - mu_infinity)/((1 + (lambda * StrainRate)^2)^(1/3))

I previously defined succefully :

lambda = -0.2783 [s]
mu_infinity = 2.7459e-3 [kg/(m*s)] 
mu_zero = 3.5832e-3 [kg/(m*s)]

[Federico]

Hello Alexandre, 

please use a different name for lambda and this should work.

[ALEXANDRE COSTA]

Hi,

Even  changing lambda to lamb_da, it says Expression Does Not Evaluate to a Single Value. 

I already initialized the flow.

[Federico]

The expression does not evaluate to a single value because of StrainRate, which is a tensor field. Your expression will depend on the value of StrainRate at a given location.

The message you are seeing is not an error, you should still be able to create this expression and visualize it in contour plots for example. 

[ALEXANDRE COSTA]

Hi

Returning to the old udf property definition.

[Federico]

Not sure what you mean by that.

The expression you shared works as intended. Like I said, StrainRate does not have a single value, so the message you see is to be expected on the expression definition page.