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Hi,

I am trying to develop a RT3D user defined module. Following the instructions given in the tutorials, I developed a dll file and, batchrxn ran successfully. After that, when running the  new RT3D simulation, it gives an error message "Number of Transport steps exceeds specified maximum (MXSTRN) = 1000", and the program terminated. But I defined only 1 stress period (75 days long)   with only 75 time steps (Images attached). 

Could anyone please help me with this?

Many Thanks

Subhani

Error MSG.png

Output control.png

Stress Periods.png

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Hi Kanchana, on the stress period dialog, try to increase the Max. trans. steps variable. It is the maximum number of transport steps allowed during each time step of a flow solution. Give it a high value like 1e6 and see what happens.  While performing transport simulation with MT3D based model, time steps are further divided into transport steps. When you leave 0.0 as transport step size, the model calculates transport steps size itself according to certain criteria based on the flow solution. These stability criteria relates among others to the Courant number, you can find more about these in the MT3DMS manual (Zheng, Wang, 1999).

Edited by Michal

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Hi Michal,

Many Thanks for the comment.

I tried increasing Max.Trans.steps as you mentioned, but still the same error pops up. 

Can this be a problem related to the edited source code in user defined modules?

 

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I guess it can. For instance if the reaction module causes abrupt changes in concentration of some specie. Does it run ok with MT3DMS? I mean without the reactions only as conservative transport?

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Hi Kanchana,

its realy hard to tell what may be causing the troubles. I guess it will be something in the reaction module related to the reaction rate. Try to run the simulation for lets say a minute with time steps in the order of seconds or fractions of a second. Also increasing grid resolution may improve the solution.

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