## Question on hCritA

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ikipkemoi
Posts: 4
Joined: Fri Jun 15, 2018 2:44 pm
Location: United Kingdom

### Question on hCritA

Hello Team Hydrus,

I am using the formula Hr = exp[h*M*g/RT] to calculate hCritA. It is given that Hr is the relative humidity, h is the pressure head, M is the molecular weight of water [M/mol] (=0.018015 kg/mol), R is the universal gas constant [ML^2/T^2/K/M] (= 8.314 kg m^2/s^2/K/mol, J/mol/K), and T is the absolute temperature [K].

who knows what is ''g'' in this equation?

Thanks,
Isaac

Jirka
Posts: 4726
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

### Re: Question on hCritA

"g" is gravitational acceleration. This information is in both Help (Variable Boundary Condition) and Manual (eq. 2.74). J.

ikipkemoi
Posts: 4
Joined: Fri Jun 15, 2018 2:44 pm
Location: United Kingdom

### Re: Question on hCritA

Thank you prof.

I have calculated hCritA and the values are within the recommended 150 m to -1000 m, eq. 2.74 helped, but help is missing the 'g'. Thanks a lot.
IK

Jirka
Posts: 4726
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

### Re: Question on hCritA

It certainly is not (see the snapshot below). J.
Attachments
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