       Finite Boundary Conditions

• To: mathgroup at smc.vnet.net
• Subject: [mg6956] Finite Boundary Conditions
• From: "Rick A. Sprague" <sprague at egr.msu.edu>
• Date: Wed, 30 Apr 1997 22:25:08 -0400 (EDT)
• Organization: Michigan State University College of Chemical Engineering
• Sender: owner-wri-mathgroup at wolfram.com

```Hello,

I was trying to solve this differential equation for viscous flow through a
circular pipe:

D/Dr (-r m D/Dr v[r]) = A r

where
A,m - constant
v - velocity

BC:
v'=0		Symmetry
v[R]=0		No Slip

I get the following message and {} as a solution:

"Power::infy: Infinite expression 1/0 encountered."

MMA is having a problem solving for C when r=0 - which I can understand.

v'[r]==-A r/ (2m) + C / r

I could solve this equation by hand, but I was wondering how to make MMA
force a finite boundary condition.  Actually, how does one generally submit
the BC "finite" to MMA?

Thanks,

Rick

```

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