Author |
Message |
Rony Melo (rgmmelo)
New member Username: rgmmelo
Post Number: 1 Registered: 08-2007
| Posted on Thursday, September 06, 2007 - 07:02 pm: | |
hi... I'm a new flexpde's user and don't know how I set danckwerts boundary conditions. I've this boundary: c1*dc/dz(z=0)=c2*(c(0+)-c0), when I use finite difference method I approximate of that way: c(0+)= ( c(j+1)+ c(j))/2 can anybody help me? in this website explains better my boundary conditions : http://www.engin.umich.edu/~CRE/course/lectures/fourteen/index.htm |
Robert G. Nelson (rgnelson)
Moderator Username: rgnelson
Post Number: 949 Registered: 06-2003
| Posted on Saturday, September 08, 2007 - 01:00 pm: | |
IF the second-order part of your PDE is "Div(-C1*grad(C))", and IF z=0 is the planar bottom boundary, THEN c1*dc/dz looks like the Natural BC for your equation. IN THAT CASE, NATURAL(C)= c2*(c-c0) implements the BC you mention. I have no idea what your statement c(0+)=(c(j+1)+c(j))/2 means. It's just an average, and j is undefined.
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Robert G. Nelson (rgnelson)
Moderator Username: rgnelson
Post Number: 950 Registered: 06-2003
| Posted on Saturday, September 08, 2007 - 01:01 pm: | |
PS See NATURAL in the Help Index.
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Rony Melo (rgmmelo)
New member Username: rgmmelo
Post Number: 2 Registered: 08-2007
| Posted on Sunday, September 23, 2007 - 11:48 am: | |
thanks nelson, i'll read help again |