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McLachlan dissipation error
A kind person tells me:
I wanted to mention what appears to be a mistake in your dissipation calculation. If you refer to Kreiss-Oliger, or equivalently to Dissipation/src/apply_dissipation.F77, you find that there is a sign flip at certain orders. For example, 3rd order dissipation to be used with 2nd order differencing, and 7th order dissipation to be used with 6th order differencing, both need a negative coefficient. But you don't appear to have such a minus sign (unless I missed it), and your parameter epsdiss is constrained to be positive. It looks to me like PDdissipationNth needs to be multiplied by something like (-1)^(fdOrder/2).
Keyword: backport
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Please apply.
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I propose that this fix be backported to the release. Agree?
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Yes. I agree.
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I have backported the fix to the Oersted release.
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That person is right. The above patch provides this correction. This only has an effect when fdOrder is set to 2 or 6.