# CEL Position Dependent Variables in CFX-Pre

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 November 19, 2011, 10:33 CEL Position Dependent Variables in CFX-Pre #1 New Member   Neal Wannell Join Date: Nov 2011 Posts: 5 Rep Power: 13 Hi there, I am trying to model the evaporation of water from a surface. I am modelling the liuid surface as a free-slip wall and am using a continuity source over the wall to represent the evaporated water. I am writing expressions to calculate this mass flux, and they require the wall heat flux for the boundary in question. The wall is an x-y plane and I need to have a heat flux that is dependent on the x and z coordinate over the wall surface. I only know how to use locator based functions that calculate an average of the variable over the surface, and this is not suitable. How would I go about writing a CEL expression to include this position dependence over the wall? Thanks

 November 19, 2011, 18:16 #2 Member   sajad Join Date: Nov 2010 Posts: 51 Rep Power: 14 hi there is a command in name of "position x" or "position y" and so "position z"...are this helpful for you? can you say what is your problem and whiat is the CEL too?

 November 20, 2011, 05:11 #3 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,327 Rep Power: 138 You can use x, y and z variables in the CEL expression to define the boundary condition. For instance in the boundary condition definition "heat flux = 10*x +100*y - 5*z" would give you a varying heat flux over the boundary surface.

 Tags cel expression, cel functions, user defined expressions