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Poiseuille flow

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The flow of a homogeneous viscous incompressible fluid in a long tube of circular cross section. For a steady flow in the direction the flow equation is

\frac{\partial^2u}{\partial y^2}+\frac{\partial^2u}{\partial z^2}=-\mu^{-1}G,

where G is the pressure gradient and \mu is the viscosity. For Poiseuille flow the flow is assumed to have the same axial symmetry as the boundary conditions, hence u is a function of the distance from the axis of the tube only. The solution with boundary value 0 at the boundary of the tube and no singularity at the axis is

u(r)=\frac{G}{4\mu}(a^2-r^2),

where a is the radius of the tube. This flow was studied by G. Hagen in 1839 and by J.L.M. Poiseuille in 1940.

The Poiseuille flow is stable for a small Reynolds number, and becomes unstable at higher Reynolds numbers. This was established experimentally by O. Reynolds in 1883. For Poiseuille flow the critical Reynolds number is around 2\cdot10^3. For a discussion of hydrodynamic instability and bifurcation of Poiseuille flow and other laminar flows, such as Couette flow (the steady circular flow of a liquid between two rotating co-axial cylinders) see [a1], [a2]. See also Orr–Sommerfeld equation.

References

[a1] S. Chandrasekhar, "Hydrodynamics and hydrodynamic stability" , Dover, reprint (1981) pp. Chapt. VII
[a2] Th.J.R. Hughes, J.E. Marsden, "A short course on fluid mechanics" , Publish or Perish (1976) pp. §18
[a3] G.K. Batchelor, "An introduction to fluid dynamics" , Cambridge Univ. Press (1974) pp. 180ff
How to Cite This Entry:
Poiseuille flow. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Poiseuille_flow&oldid=32849