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2D and 2D axis difference

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Old   January 27, 2012, 01:07
Default 2D and 2D axis difference
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Qi Guan
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I have a euler-solver code, structured grid. It works for 2D. I want to change it to 2d axisymmetric. I've changed the associated volume and face area and source term coming along with axisymmetric.

But there's still problem in it. Is there anything else I should do?

Thank you.
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Old   January 27, 2012, 02:59
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Martin Hegedus
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Source term?

You'll need to change the fluxes (RHS) in the j (theta direction) along with the required implicit stuff on the LHS (if you are doing implicit).

For the RHS you have a flux term (which does not exist in 2D) in the theta direction along the lines of p*A(j+1)-p*A(j-1) but A(j+1)-A(j-1) can be reformulated as -(A(i+1)-A(i-1)+A(k+1)-A(k-1)). Or something along those lines. That was for central differencing.

That, along with changes in area and volume, should be enough. I believe...
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Old   January 27, 2012, 03:02
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Oh, one more very important thing. Unlike 2D, your CFL number MUST take into account the theta direction. I usually use a 5 degree wedge to calculate CFL.
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