CXTFIT - Input Concentration

A discussion forum for STANMOD users. STudio of ANalytical MODels is a software package for evaluating solute transport in porous media using analytical solutions of the convection-dispersion solute transport equation.

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Joined: Fri Jun 22, 2012 10:49 am
Location: Germany

CXTFIT - Input Concentration

Post by MaMa » Fri Jun 22, 2012 11:08 am

Hi everyone!

I've got a question and I hope it's not a stupid one! ;-)
I'm not quite sure which of the following is relevant, but these are my choices:
STANMOD - CXTFIT - deterministic noneq. - time and position dimensional (m - d - mg/l)- resident conc. - <u>Pulse input at application time T</u>

My question: What do I have to put in the field "Input concentration"? I've been told that I have to put the mass of tracer (Bromid: 300g) in mg in there. Which is in this case "300.000" but I can't believe it, because this is not a <u>concentration</u>, of course. And also when I read the manual I get the impression that it is wrong. But I don't really understand the manual in that point. That's why I have to ask.

I would really appreciate an answer since I spent many hours trying to figure this out...
All the examples that come with the program seem to use dimensionless.

Have a nice weekend!

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Joined: Fri May 21, 2004 12:50 pm
Location: Japan

Post by ntoride » Fri Jun 22, 2012 3:26 pm

If you apply 300 g of Bromide at once uniformly on the surface, use the dirac delta input ( see the CXTFIT manual, p.7 &70). m_b is the amount of solute per unit surface area (cm^2). Since the input parameter is m_b/v, you need to know v in advance (you cannot estimate v).

Alternatively, you can use the pulse input. In this case,
Input mass = c_o*application time * v = m_b.
As long as the input mass is same, the results subject to the pulse input is almost same as for the delta input if the application time is small. You can use hypothetical values for c_o and application time based on the m_b and v values. Hence you also need to know v in advance for the pulse input.

If any further questions, please do not hesitate to ask me.


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