# adapt viscous resistance based on velocity / UDF

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 April 17, 2009, 11:30 adapt viscous resistance based on velocity / UDF #1 New Member   Join Date: Apr 2009 Location: KA, Germany Posts: 20 Rep Power: 10 Sponsored Links I am new here, so hi everyone! I am currently simulating the (laminar) flow through a filter medium / porous zone. After an initial state (viscous resistance of filter is homogeneous) I want to adapt (increase) the viscous resistance of the filter based on the magnitude of the velocity (~ flow) in each cell of the porous zone. This will lead to a new solution of the problem. Now the viscous resistance can be again adjusted etc. Now I have some questions related to my work: a) Can I access (meaning read/write) the viscous resistance of a cell somehow OUTSIDE of the DEFINE_PROFILE macro hooked to the viscous resistance of the porous zone? b) If I use the unsteady state solver, I can set the iteration intervals at which the UDFs shall be updated. Is there any way to tell FLUENT only to update the UDFs every time step (regardless of the iterations)? c) In general: How could I approach the "stepwise" nature of the problem best? Meaning: calculate a solution -> adjust the boundary conditions in this case viscous resistance) using the solution -> calculate the new solution -> adjust again etc. Any help will be greatly appreciated!

 April 20, 2009, 07:12 #2 New Member   Join Date: Apr 2009 Location: KA, Germany Posts: 20 Rep Power: 10 a) Still not sure if / how that works b) One can use the variable first_iteration, which is true only at the first iteration of every time step But I have another question: How can I display the cell values of the viscous resistance? I not only want to look at the velocities inside my porous zone, but also at the viscous resistances of the cells.

 April 20, 2009, 10:08 #3 New Member   Join Date: Apr 2009 Location: KA, Germany Posts: 20 Rep Power: 10 Ok, just write it to UDM and FLUENT will be able to display it. Question remaining: a).

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