Question about constant rate

Hi, everyone,

I am trying to add the constant mass injection case in my model. Based on the manual, I uses the "mass" to represent the injector by using the dummy element. The flow input and output files shows the tough2 could read the mass injection command, but the pore pressure contour map does not show the pressure build up at injection well. I am wondering whether the dummy element could be used for the mass injection? Or anyone could give me a  hint about what is possible problem? Thanks.

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  • Hi Quan,

    Not sure what you mean by "dummy element". If this element has a zero or negative volume, it is by definition inactive (i.e., represents a boundary element with a Dirichlet boundary condition) - in that case, you do not expect any pressure build up. It does not make sense to specify inks/sources for inactive elements.


  • Hi, Stefan, Thank you for your reply. The dummy element here defines a source line and how it connects with surrounding elements. I use a very large value in defining the volume. In terms of the type of boundary condition, I used $mass as the input for the tough. The constant injection pressure module could work, the pressure could build up, but when I change the dirichlet  into mass injection condition, the model could run, but no injectivity appears. So confused. 

  • Hi Quan,

    Again, if you have a very large volume for these "dummy" elements, they act as a Dirichlet boundary condition. Whatever you inject into these elements "disappears" into the large volume, so no pressure build-up occurs. While this may not be the behavior you intended, it is the expected behavior. Give these elements regular volumes consistent with the geometry of your mesh.

    I hope this explanation resolves the issue.


  • It works!!! Stefan, Thank you so much! I really really appreciate it. I stuck in this issue for two weeks. That's amazing for your suggestion. Again, thanks.

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