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Dispersion coefficient in FEMWATER


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I am running a contaminant transport model in FEMWATER.

I am wondering if I have set up the dispersion coefficient parameters correctly.

In the FEMWATER manual it gives the equation for the D tensor as

theta D = aT |V| delta + (aL-aT) V^2 / |V| + am theta tau delta


theta is the moisture content (not the porosity)

delta is the Kronecker delta function (basically an identity matrix)

am * tau is the molecular diffusivity D*

V is the fluid velocity

aL is the longitudianl dispersivity

aT is the transverse dispersivity

My problem is the first theta. In all the other references I have seen it is not there, for example Zheng & Bennett 2002. I am wondering if it is a typo. If it is not a typo then the parameters in this equation are different the usual form such as given in Zheng & Bennett and it would make a big difference.

Would appreciate your help. Thanks.

Edit: Update: Actually V in the above equation is the Darcy velocity = theta * Fluid (seepage) velocity. So theta appears in every term. It seems this equation is the correct form for unsaturated conditions. My mistake.

Edited by woodward
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