[MITgcm-support] Variable biharmonic viscosity and energy conservation

[Christopher L. P. Wolfe]

Hi all,

Griffies and Hallberg (2000) note that biharmonic viscosity with a variable coefficient doesn’t conserve energy unless the coefficient is “split” into its square roots and appears in front of both gradient parts of the biharmonic operator; that is, operators of the form

Gu = div(sqrt(A4) grad( div( sqrt(A4) grad u)))

conserve energy (and angular momentum), whereas operators of the form

Gu = div(A4 grad( div( grad u)))

do not. According to both the manual and what I’ve found in the code, the MITgcm implements the second, non-conservative method rather than the first. Does anyone (perhaps Jean-Michel?) know if biharmonic viscosity is still implemented this way for a reason, or is it just due to inertia? At the first glance, it doesn’t seem like a very difficult change to make, though perhaps I am mistaken.

Thanks in advance for the info.
Christopher

-----------------------------------------------------------
Christopher L. P. Wolfe
Assistant Professor
School of Marine and Atmospheric Sciences
Stony Brook University
christopher.wolfe at stonybrook.edu             631-632-3152
-----------------------------------------------------------





-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mitgcm.org/pipermail/mitgcm-support/attachments/20140626/c106b688/attachment-0001.htm>