Hi,
I am using the Richards Equation interface and there is an equation relating kappa (permeability) to k (hydraulic conductivity) which is written in the documentation but I have calculated by hand what I should be getting and it seems COMSOL is making a mistake. (I have also googled my equation and found that my hand calculations are confirmed elsewhere.) The equation states that:
kappa = k*mu/(rho*g)
where mu is the fluid dynamic viscosity (in my case 1E-3 Pa*s) and rho is the fluid density (in my case 1000 kg/m^3) and g is the gravitational acceleration (~9.8 m/s^2). My ks (k at saturation) is 6.94E-7 m/s, so my kappa at saturation should be 7.07E-14 m^2. I set my kappa as such, and sure enough it is showing me that "kappas" (saturated permeability) is 7.07E-14, and then when I check the saturated hydraulic conductivity it says that "ks" = 2.94E-4, which is off by several orders of magnitude.
Does anyone know why COMSOL might be using a different equation than it should be? I am sure that my math is right and all of the units are as they should be - I have no idea what the problem is!
Thanks,
Shoshana
I am using the Richards Equation interface and there is an equation relating kappa (permeability) to k (hydraulic conductivity) which is written in the documentation but I have calculated by hand what I should be getting and it seems COMSOL is making a mistake. (I have also googled my equation and found that my hand calculations are confirmed elsewhere.) The equation states that:
kappa = k*mu/(rho*g)
where mu is the fluid dynamic viscosity (in my case 1E-3 Pa*s) and rho is the fluid density (in my case 1000 kg/m^3) and g is the gravitational acceleration (~9.8 m/s^2). My ks (k at saturation) is 6.94E-7 m/s, so my kappa at saturation should be 7.07E-14 m^2. I set my kappa as such, and sure enough it is showing me that "kappas" (saturated permeability) is 7.07E-14, and then when I check the saturated hydraulic conductivity it says that "ks" = 2.94E-4, which is off by several orders of magnitude.
Does anyone know why COMSOL might be using a different equation than it should be? I am sure that my math is right and all of the units are as they should be - I have no idea what the problem is!
Thanks,
Shoshana