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unexpected unit of input, derivative of analytic function
Posted Nov 28, 2014, 12:45 p.m. EST Modeling Tools & Definitions, Parameters, Variables, & Functions 1 Reply
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I am very new to Comsol. I use Comsol 4.4.
I have created an analytic function Temp = (deltaT)/(1+(r/w)^2) <-- it defines a temperature gradient.
Argument -> r, argument unit -> m;
Function unit -> K;
I then define a conservative flux in the PDE:
-r[1/m]*(DS*cSr+DTS*cS*grad(Temp(r))*step2(t[1/s])*step1(t[1/s])) <-- expected unit mol/(m^2*s)
where
[DS]=m^2/s;
[cS]=mol/m^3;
[DTS]=m^2/(s*K);
step function is used to turn Temp(r) on and off.
But I need a derivative of Temp(r) in the PDE. And when I use grad(Temp(r)) or Temp(r)r, I get an error "unexpected unit of input".
Could you suggest what is wrong?
Thank you in advance!
Evgeniia
Hello Evgeniia Edeleva
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using the version 5.2, in the variable expression i try to use sinh(phi) or cosh(phi) and give them a name , the unit of (phi) is the volt wich is the variable of electrostatic module, but the color is orange and show ''unexpected unit of input'' so i can't used it in boundary condition ad i can't solve my problem
Appreciate much for your help!!