Vortex Breakdown

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April 3, 2015, 13:52
Vortex Breakdown
#1
New Member

Thomas Milin
Join Date: Aug 2014
Posts: 7
Rep Power: 5
Respected Users,

I am doing a simulation of the vortex breakdown phenomena in an open cylinder(top) with rotating bottom wall. I am using water as the fluid and the bottom is rotated at Re=2600 as per the journal. The top is open to the atmosphere. At Re=2600 I am getting the exact replica of the vector plot but as the Reynolds number is increased I am not able to obtain the vortex breakdown phenomena. Breakdown was obtained in the journal at Re=3000. Following are the input parameters i am giving in fluent.

Solver- Pressure based ,steady, relative

Models- Laminar(all others off)

Materials- water (from database)

Cell zone condition- interior volume is made fluid and material is made water.The rotation axis origin is given as (0,0,0) and rotation axis direction as (0,0,1)(all other boxes are left unchecked)

Boundary conditions-
top is made pressure inlet
bottom is made rotating by imparting angular velocity(by selecting moving,rotational,absolute) of .104667rad/s.
radius is 15.23cm and height is 63.19cm
side is made a no slip wall

Reference values- compute from bottom is given and reference values are left as such, reference zone is selected as interior volume

Solution methods- simple, least square cell based, second order, second order upwind

Solution controls- under relaxation factors are retained as such(i.e pressure .3, body forces 1, density 1, momentum .7)

Standard absolute initialization is given

These are the various input parameters I am giving yet i am not able to obtain the breakdown phenomena.

Any comments will be really valuable.

Thanking you for your patience and help.

P.S] I am also enclosing the velocity contour plot of my simulation at Re=2600
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 April 6, 2015, 00:36 #2 New Member   Thomas Milin Join Date: Aug 2014 Posts: 7 Rep Power: 5 Thank you very much for your suggestions . Let me make a simulation with your suggestions and ill post the result. Yes i think so. Consider the case of shock waves generated when the valve of a penstock pipe is closed.

 April 16, 2015, 04:55 #3 New Member   Thomas Milin Join Date: Aug 2014 Posts: 7 Rep Power: 5 The transient mode you specified is also not yielding any vortex breakdown phenomenon. It is also giving the exact same result as i used to get with previous cases. Do you have any other alternatives for the problem. Thank You

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