Difference between revisions of "Biharmonic"
From MohidWiki
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where <math>\mathrm{K}</math> is Fick's law diffusivity. | where <math>\mathrm{K}</math> is Fick's law diffusivity. | ||
| − | A ready made formula that would estimate the order of magnitude of the <math>\kappa_4</math> coefficient would be | + | A ready made formula that would estimate the order of magnitude of the <math>\kappa_4</math> coefficient for momentum would be |
<math>\kappa_4 \sim \frac{U}{16} \Delta x^3</math> | <math>\kappa_4 \sim \frac{U}{16} \Delta x^3</math> | ||
Latest revision as of 14:30, 28 June 2011
The biharmonic filter is an extra term that is added in the horizontal turbulent viscous flux, J, that filters high frequency oscillations in a numerical model of advection-diffusion of a property 
(i.e. oscillations with a wave-length equal to one or two widths of the horizontal resolution):
where 
is Fick's law diffusivity.
A ready made formula that would estimate the order of magnitude of the 
coefficient for momentum 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.
