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2nd order schemes only 1st order accurate?

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Old   September 10, 2012, 05:44
Default 2nd order schemes only 1st order accurate?
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Hi all,

I am running a volume of fluid simulation with highly turbulent (k-epsilon model) water flowing in a 2D domain. I am using the Non-iterative time advancement option with a fractional step. I have set all discretisation schemes to second order (Momentum, Turbulent Kinetic energy and transient formulation) using PRESTO! for pressure and Modified HRIC for VF.

When I check for grid convergence I only get first order convergence. I am unable to check for finer meshes due to computation time. I understand there is inaccuracies associated with both the VOF method and k-epsilon model however there still should be 2nd order convergence.. right??

Any recommendations? I am about to progress and just talk about how 2nd order accuracy could not be obtained due to the complexities of the flow.. is that bad practice?

Thanks for any advice!!!
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Old   September 11, 2012, 03:10
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Hi
Did you have an orthogonal mesh? I think orthogonality can reduce the order of accuracy. Or may be your mesh is not so fine.
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Old   September 11, 2012, 04:22
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Quote:
Originally Posted by ata View Post
Hi
Did you have an orthogonal mesh? I think orthogonality can reduce the order of accuracy. Or may be your mesh is not so fine.
Thanks for your reply,

Yes I am using a orthogonal mesh. What mesh should I be using?

Unfortunately due to time constraints and lack of resources I am unable to reduce my mesh size any further. It could potentially be the issue, but I feel my mesh is fine enough.
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Old   September 11, 2012, 05:16
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And what is the maximum aspect ratio in your mesh?
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