Re: trouble with NDSolve
- To: mathgroup at smc.vnet.net
- Subject: [mg63612] Re: [mg63590] trouble with NDSolve
- From: Pratik Desai <pdesai1 at umbc.edu>
- Date: Sat, 7 Jan 2006 02:29:39 -0500 (EST)
- References: <200601061024.FAA14623@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
lahm wrote: >i have trouble with solving a diffusion problem with NDSolve. I would like to get a 2D concentration profile using second Fick's law dc/dt=d2c/dx2 + d2c/dy2. c is concentration and is function of t,x and y. The initial condition is concentration=1 everywhere. The boundary conditions are c=1 for x=1, y=1 and y=-1. On x=0, however, the concentration is 0, but only for -0.01<y<0.01, the other part of x=0 acts neutral, is neither a sink nor an inlet, concentration therefore is determined by the sink and the boundaries. Now when I try to imput that c=0 only at a part of x=0, I get the message that boundary condition is not specified on a single edge of the boundary of the computational domain. NDSolve::bcedge: I tried several different approaches, but all of them have failed. There's always something wrong so mathematica always encounters some problem. I can't make only one part of the boundary work as a sink an the other to be neutral. Please help! > > > One of the reasons, if I am not mistaken, the 2- D laplacian term in your PDE is notoriously problemetic for a finite difference schema (NDsolve uses quite a bit of FD schemes). There was a thread regarding a similar issue a heat equation for a square plate...last year. Here is the link anyway http://groups.google.com/group/comp.soft-sys.math.mathematica/browse_frm/thread/5fc408a259b51a90/4138f70b28bf6a78?lnk=st&q=Heat+equation%2C+NDSolve%2C+Nasser&rnum=1#4138f70b28bf6a78 Hope this helps Pratik
- References:
- trouble with NDSolve
- From: lahm <mifdavid@yahoo.com>
- trouble with NDSolve