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Using a specific global variable for boundary expression
Posted Jun 28, 2010, 5:26 p.m. EDT 0 Replies
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I'm modeling a gas flow over a flat substrate in a tube furnace in 2D. I need to define a boundary condition on the substrate surface by using "boundary expression".
Could you shed some light on how to write correctly a global variable, such as a concentration with specific coordinates in the boundary condition?
My boundary is a line from (87, -2.69) to (91, -2.69), c_Zn is the concentration, and "length" is defined as "x-87". Here is what I wrote for the boundary condition:
-0.332*Re_x^0.5*D_Zn_Ar*(c_Zn(length,0)-c_Zn(length,-2.69))/length
It looks like "(c_Zn(length,0)-c_Zn(length,-2.69))" is not accepted by COMSOL.
Many thanks,
Carlos
Hello Carlos Fernandes
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