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Natural convection in an infinite vertical cavity
3 Attachment(s)
I need to simulate natural convection flow between two differentially heated, infinite vertical walls. The problem is two-dimentional, Rayleigh number is 1.01E+5.
Attachment 8989 The simulation file (created in CCM+ 4.04) can be downloaded from http://www.sendspace.com/file/bwkssb Analitical solution is stated in Benjamin Gebhart - Buoyancy-Induced Flows And Transport. Look at temperature and velocity plots Attachment 8988 Reference density is located on the left side in the middle between top and bottom sides. It's calculated according to ideal gas law. Attachment 8991 Physics http://img3.imageshack.us/img3/9256/pic04i.png I wonder if it's correct to model infinite walls applying outlet pressure boundary conditions on the top and bottom sides. Is in OK? The point is that I can't make in converged (the residuals are: Attachment 8987 |
buoyant flow is naturally quite unstable and you might never achieve a steady solution. You need to set some monitoring points and dump some scenes to see what is changing every few iterations. Then try the unsteady solver with a reasonable dt - start with .01s maybe.
Also depending on you density range, you probably don't need ideal gas - try gravity + Boussinesq |
4 Attachment(s)
Quote:
Velocity vector scene Attachment 9055 Velocity plot Attachment 9056 Temperature plot Attachment 9058 Values are distributed relative to the center axis symmetrically so that they correspond with analytical solution. Bringing Ra back to 1E+5 results in solution to diverge. :confused: Quote:
Why "Reference Altitude" don't seem to affect the results? Attachment 9057 |
there is a similar problem in fluent tutorial, about natural convection. there is something that i didn't understand. the amount of Rayleigh number is 5e05. then it is suggested that due to this Rayleigh number, put 6.94e05 for gravity.
hoe is it possible? |
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