What unit to use in APDL for permeability PERM command (m^4/Ns) or (m/s)

- September 13, 2021 at 3:10 pm
  
  arianeparisien
  Subscriber
  
  Why in the porous media ansys guide, it is saying that TBDATA for TB, PM,,,PERM (permeability) is related to length/time units? I am using element CPT217 and I inserted my permeability in m^4/Ns for my simulation, following previous research code examples, would that be correct? Previous researcher that publicated their code also used permeability in m^4/Ns for their PERM porous material property command. Can I get clarification on what is the proper unit to insert for the permeability?
- September 15, 2021 at 3:26 pm
  
  mrife
  Ansys Employee
  
  please see the following MAPDL help section:
  Help 2021 R2 -> Mechanical APDL -> Material Reference -> Chapter 4.11 Porous Media -> section 4.11.1 Fluid Flow and Permeability
  Then review equation 4-82. By unit analysis the units of permeability are length/time. Perhaps the other research code examples were not solving for flow flux? Or perhaps had a different form of the equation?
  Mike
- September 15, 2021 at 3:35 pm
  
  arianeparisien
  Subscriber
  
  Thank you, I figured out what they did. The other research paper were evaluating water and did not specify the weight. Then ANSYS assumed a weight of 1 instead of 10000, making their permeability in m^4/Ns give the same answer as if they would have assign the weight of 10000 plus inserting their permeability in m/s.