tube bank inertial resistance coefficients

Brian

Hello, Can anyone suggest how to correctly calculate the inertial resistance coefficients for a bank of tubes?

I'm attempting to apply the fluent porous media model to simulate flow through a bank of tubes. I'm using only the inertial resistance coefficient, as advised by the fluent help files (6.19.2 Momentum Equations for Porous Media).

I have no experimental data with which to calculate the intertial resistance factor - I used the equations provided by fluent for estimating the inertial resistance coefficient for packed beds in fluent help section 6.19.6 (equation number 6.19-17). I estimated the particle diameter that would give a similar void fraction as my bank of tubes.

I am using C2=1.15e+05 in the x direction and C2=1.15e+07 in the y&z directions (to constrain flow in the direction of my tube bank). My solutions will not converge. I realize that using the packed bed equation mentioned above may result in an overestimate for C2. When i scale these coefficients down (C2x=1.15e+03 and C2y=C2z=1.15e+05) the solution seems more likely to converge.

I'm wondering if i'm grossly overestimating the C2 coefficient... so can anyone suggest how to correctly calculate the inertial resistance coefficients for a bank of tubes?

Thank you, Brian