MathGroup Archive 1997

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Finite Boundary Conditions

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


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

	A,m - constant
	r- radius
	v - velocity

	v'[0]=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[1] when r=0 - which I can understand.

		v'[r]==-A r/ (2m) + C[1] / 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?



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