# Taylor Couette Instability

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 February 18, 2004, 00:11 Taylor Couette Instability #1 CFD Guest   Posts: n/a I have been trying to get my canned finite volume code simulate the Taylor Couette Instability. This occurs when the flow between 2 rotating cylinders goes unstable after a certain value of the Taylor number is reached. Basically if the outer cylinder is rotating slower than the inner one by a certain ratio, the flow should go unstable. This is often cited as the best validation of a code. Does anyone have experience doing this? At what Taylor numbers could they achieve the instability? How long did it persist? What were the sizes of the cells?

 February 18, 2004, 05:20 Re: Taylor Couette Instability #2 Tom Guest   Posts: n/a Have a look in the book by Drazin & Reid on Hydrodynamic stability it contains the marginal stability curves and everything else you need to know. The instability persists as long as you keep the cylinders rotating - when you are above the neutral curve there exists more than one steady state (in the simplest instance) solution. One of these solutions is Couette flow which is the base state which goes unstable and the other is the Taylor flow which is a periodic set of vortices which bifurcates from the base state at the critical Taylor number, Tom.

 February 18, 2004, 06:41 Re: Taylor Couette Instability #3 daniel Guest   Posts: n/a Hi, Can I ask you if you are using cylindrical coordinate code? And how do you work with the boudary?( The Taylor instability has a linear solution for an infinity long cylinder). Thanks

 February 18, 2004, 11:09 Re: Taylor Couette Instability #4 Jarmo Monttinen Guest   Posts: n/a Another excellent source for information: Chossat & Iooss: The Couette-Taylor problem. -- Jarmo

 February 18, 2004, 13:49 Re: Taylor Couette Instability #5 CFD Guest   Posts: n/a Thanks all for yr comments. I have been reading Drazin and Reid for the problem, and am well aware of what should happen theoretically. Unfortunately, this does not happen in the simulation. I do not see any major 3D structures in the flow. I am imposing periodic boundary conditions in the axial direction. The size of my domain is 10* the separation between the cylinders.

 February 19, 2004, 03:02 Re: Taylor Couette Instability #6 versi Guest   Posts: n/a As the first instability of circular Couette flow, toroidal Taylor vortex cell will appear side by side in the axial direction, which is roughly square in shape crossing the gap. Simulation of Taylor vortex needs proper form of artificial perturbation imposed for some time in most cases, and with proper grid numbers. Also, be sure your Taylor number ( or equivalent Reynolds number ) be greater than (not nearby) the critical one.

 February 19, 2004, 05:47 Re: Taylor Couette Instability #7 Tom Guest   Posts: n/a Actually being able to pick up the neutral stability curve is a good test of a computer code (providing the bifurcations are supercritical of course). You can also test the code against weakly nonlinear theory which it should agree with.

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