Hi all,

I am doing a soot cake combustion transient simulation with fluent. I can get everything including temperature magnitude, soot concentration and oxygen concentration right except velocity contour.

I found the velocity contour is very sensitive to permeability namely viscous resistance of soot cake. I tried to draw the plot of resistance coefficient varying with consumption of soot and found almost linear relationship. However, I am expecting exponential decrease of resistance with the consumption of soot. 

I read a lot of papers. Those authors just assume spherical particle composition for the porous soot cake. Can anybody give me some suggestions on how to calculate porous soot cake permeability?