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Old   December 20, 2010, 01:43
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Pavelistyj
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Hello All,

I want to use the following expression in inlet boundary condition:

Pmax*((sin(omega*t))^2)*(step(t)-step(t-0.02))+Pmax*step(t-0.02)

where omega,Pmax are defined.
But I get the following error:

Bad expression value 'Pin' detected in parameter 'Relative Pressure' in object '/FLOW:Flow Analysis 1/DOMAINefault Domain/BOUNDARY:Inlet/BOUNDARY CONDITIONS/MASS AND MOMENTUM'.
CEL error:
The dimensions of the argument to function 'step' are inconsistent with expected dimensions.
Argument dimensions resolve to 's'; expected '<dimensionless>'.


Please help.
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Old   December 20, 2010, 03:20
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Lance
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Your step functions need to be dimensionless, just as the error says.

Change step(t-0.02) to step((t-0.02[s])/1[s]) for example.
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Old   December 20, 2010, 03:41
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Fabio
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Yes, Lance is right! Wherever you have something that has a dimension in your expression, you need to divide it for its dimension unit. So, wherever you have time, you need to divide by 1 [s].
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Old   December 22, 2010, 06:26
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Pavelistyj
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Ok, it works!

Thank you very much!
P.K.
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