# Cel expressions Time dependent

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 December 4, 2007, 12:28 Cel expressions Time dependent #1 Juan Maria Campos Guest   Posts: n/a Sponsored Links Hi everybody, I want to create a variable through a CEL Expression dependent of the value of this variable at the former timestep. How can I make it? thanks in advance

 December 6, 2007, 10:30 Re: Cel expressions Time dependent #2 mac Guest   Posts: n/a Hi You've fixed or variable timestep

 December 7, 2007, 04:24 Re: Cel expressions Time dependent #3 Juan Maria Campos Guest   Posts: n/a I have fixed timestep

 December 7, 2007, 10:12 Re: Cel expressions Time dependent #4 mac Guest   Posts: n/a It's seem to be simple but I don't know what do you want to do with this variable. Can u explain more thx

 December 10, 2007, 09:20 Re: Cel expressions Time dependent #5 Rogerio Fernandes Brito Guest   Posts: n/a I have the same problem. I wanna put a heat flux, in [W/m^2] as a boundary condition (BC) that varying with the time "t", in [s], using the CEL expressions. At the CFX v5.6, the BC of heat flux must have the same unity, as [W/m^2]. If my heat flux varies with the time as, for example: q(t)=t^2+3*t-4 with q in [W/m^2] and t (time, not T of temperature) in [s]. My doubt: How to transform the expression 't^2+3*t-4' from [s] to [W/m^2]? I can´t use a heat flux as a BC in [s]. Only in [W/m^2]. Rogerio.

 December 12, 2007, 03:16 Re: Cel expressions Time dependent #6 mac Guest   Posts: n/a Hello Rogerio to do these operation you've to use fortran subroutine best regards

 December 12, 2007, 09:13 Re: Cel expressions Time dependent #7 Rogerio Fernandes Brito Guest   Posts: n/a How?

 December 27, 2007, 06:54 Re: Cel expressions Time dependent #8 Rafael Brandao Guest   Posts: n/a Rogerio, I think you may try to divide t by the unit (1 [s]) and turn it into an adimensional expression. Then you multiply the result by the new unit. Your expression then becomes q(t)=((t/1 [s])^2+3*(t/1 [s])-4)*1 [W/m^-2] Hope it helped.

 December 27, 2007, 19:16 Re: Cel expressions Time dependent #9 Rogerio Fernandes Brito Guest   Posts: n/a This way, I think it´s better (on CFX-v5.6 version): Expression Editor Expressions Name Definition AA 1.0 s BB 1.0 W m^-2 HeatFlu BB*(t/AA)^2+3*(t/AA)^4 Please, see page 123 from CFX-5 Tutorials. I´d like to thank for helping me. Rogério Fernandes Brito.

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