fluxes along a meshline

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erwin
Posts: 14
Joined: Mon Aug 12, 2019 7:43 am
Location: Germany

fluxes along a meshline

Post by erwin » Sat Feb 06, 2021 7:37 pm

Hi everyone,

I want to check the fluxes along a meshline and I did that by multiplying the velocity with length (please check picture), but it appears to be wrong when I take the sum of these fluxes and compare it with the meshline flux generated in the results.

Also, why is the meshline velocity so different than the velocity vectors? the difference appears to be two orders of magnitude.

Thanks,
Erwin
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meshline of peat body.PNG
meshline of peat body.PNG (513.7 KiB) Viewed 425 times

Jirka
Posts: 5268
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: fluxes along a meshline

Post by Jirka » Sat Feb 06, 2021 8:13 pm

The fluxes are calculated differently than the velocity vectors. While the velocity vectors are calculated simply using Darcy’s law (i.e., the nodal conductivity multiplied by the arithmetic average of gradients in all neighboring elements (see eq. 5.28 in the Technical Manual), the fluxes across the meshline are calculated as the sum of nodal (on the meshline) fluxes directly from eq. 5.17. The latter approach is much more precise. J.

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