March 17, 2020 at 1:52 pmmaggakahnSubscriber
I am currently struggling to figure out how to model the classic Taylor-Couette problem in 2D using Fluent.
I want to simulate the problem in 2D using a crossection in the z-r plane (see bottom image for ref). Using the axissymetric option i thought i could set up a case as shown in the image below. Where the bottom line is the axis in the middle of the cylinders and the green square is the crossection of the cylinders (i.e fluid domain). Therefore by adding a azimuthal velocity (normal to the screen) to the bottom wall of the square, it would be similar to the taylor couette case.
However i cannot find a way to set a rotating velocity on the inner cylinder in the azimuthal velocity. Fluent only shows x and y as available options for rotational velocity on a wall.
Any suggestion on how to set up this case is greatly appreciated. Thank you very much for reading,
March 17, 2020 at 2:17 pmRobAnsys Employee
You'll need 2d axi-symmetric with swirl. Does that give you any other options? If not you'll need a 3d (possibly periodic) model.
March 17, 2020 at 2:32 pmmaggakahnSubscriber
Hmm i will try that. Any suggestions on how to properly include the axis line? Not sure if i have done something wrong, but i cant seem to mesh the geometry with the single line (axis) as shown in the first image I posted.
Thank you very much for the quick respond.
March 18, 2020 at 9:05 ammaggakahnSubscriber
Is there a way for a wall to be defined as both a moving wall and a axis? If I create a square as in the picture and then define the lower line of the square as both a moving wall and a axis, i think that would work.
March 18, 2020 at 10:09 amRobAnsys Employee
Axis is defined (hard coded) as y=0. The axis bc is there in case you model a cylinder and need something defined at the centreline. In your case you'll have walls at y=R1 and y=R2.
March 18, 2020 at 10:59 amRobAnsys Employee
For rotation, once 2d axi-swirl is set you should be able to give the wall an angular velocity.
March 19, 2020 at 8:50 ammaggakahnSubscriber
Yes indeed. When i turn on 2D axi-swirl i can indeed set a rotating angular velocity for the wall. In addition, I moved the axis to y=0, which helped Thank you!
The image above is the geometry i have created with SpaceClaim. Where i have detatched the two surfaces and called the bottom square "solid" (which is essentially just included to create the "axis" boundary condition for the lowest line of the square" ) and top square "fluid". This creates quite a few different bounderies when imported to Fluent.
Do you have some tips on how to properly define these surfaces?
Thank you very much for the help! Much appreciated
March 19, 2020 at 9:47 amRobAnsys Employee
Just remove the lower square: it's not needed unless you want to include heat transfer. As for the labels: read up on Named Selections in Workbench (Ansys) Meshing.
March 19, 2020 at 10:37 ammaggakahnSubscriber
Okey. But how do i then include the axis of rotation? I tried to draw a line at y=0 and named (named selection) it as "axis" at one radii apart from the inner cylinder, but the mesher did not seem to like that and simply removed it. Is there a better way of defined this axis without needing to draw it?
Thanks for the quick reply.
March 19, 2020 at 4:38 pmRobAnsys Employee
You don't need to worry about it : the axis is y=0 that's hard coded into the solver. Just mesh the fluid part at R1 distance from the y=0 and try it.
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