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CEL expression in CFX-pre

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Old   June 29, 2013, 14:17
Question CEL expression in CFX-pre
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Meimei Wang
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I'd like to define a position dependent variable by:

length = 0.0033 [m]
a = 0.1-x/length*(0.1-0.07) [m s^-1]

But the error message is

Units ([m s^-1]) are associated with a term that is not dimensionless.

It is quite strange because the unit of 'x' is [m], right? So 'x/length' should be already dimensionless. Why it is still reported as 'not dimensionless'? I'm really confused. Could anyone help?
Best regards,
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Old   June 29, 2013, 15:02
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Chris DeGroot
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You need to put dimensions on the first 0.1 as well. I would also put the units on the second 0.1 and the 0.07 separately. I've never tried factoring out the units like you did there but I'm not so sure it is valid. I would write as

a = 0.1 [m s^-1] -x/length*(0.1 [m s^-1]-0.07 [m s^-1])

Or better yet, factor the 0.1 and 0.07 into their own variables.
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