Difference between revisions of "Biharmonic"
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| − | The biharmonic coefficient is an extra term that is added to the horizontal turbulent viscous flux, '''J''': | + | The biharmonic coefficient is an extra term that is added to the horizontal turbulent viscous flux, '''J''', that filters high frequency oscillations in a numerical model of advection-diffusion (i.e. oscillations with a wave-length equal to one or two widths of the horizontal resolution): |
<math>\mathrm{J} = -\mathrm{K}\cdot \nabla C + \nabla_{h}\left( \kappa_4 \nabla_{h}^2 C \right) </math> | <math>\mathrm{J} = -\mathrm{K}\cdot \nabla C + \nabla_{h}\left( \kappa_4 \nabla_{h}^2 C \right) </math> | ||
Revision as of 14:26, 28 June 2011
The biharmonic coefficient is an extra term that is added to the horizontal turbulent viscous flux, J, that filters high frequency oscillations in a numerical model of advection-diffusion (i.e. oscillations with a wave-length equal to one or two widths of the horizontal resolution):
A ready made formula that would estimate the order of magnitude of the 
coefficient would be
where U is a typical flow velocity and 
is the numerical model horizontal resolution.
MOHID
In mohid, you need to add in the Hydrodynamic_x.dat the following keywords:
BIHARMONIC : [0/1] <-- Activates de biharmonic viscous flux BIHARMONIC_COEF : [Real] <-- Sets the value of
References
Delhez, E., & Deleersnijder, E. (2007). Overshootings and spurious oscillations caused by biharmonic mixing. Ocean Modelling, 17(3), 183-198. doi: 10.1016/j.ocemod.2007.01.002.
