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Old   November 12, 2007, 00:34
Default Continuity equation
  #1
selim
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Hi all

I have a problem in satisfying the continuity locally. I took values for velocities (u and v) from CFX and using gradients (in matlab I am sure this is right , I tested with simple cases) then look at the delta U divided by delta X + delta V divided by delta Y) but results seems not to be 0 \

Thanks
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Old   November 20, 2007, 12:04
Default Re: Continuity equation
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Jim
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I'm not going to check you maths, but assuming you're working it out right, then the obvious answer is that your solution is not sufficiently converged. Try a little experiment. Check out the values you get from the same simulation with varying levels of convergence. Maybe set the RMS residual convergence target to 1e-1, 1e-2, 1e-3, 1e-4 etc etc, and see by how much you calculation is out for the different convergence levels.

You haven't mentioned whether there is anything else going on like sources, BCs or whatever that might effect the local continuity.
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