[pilafa]

Hi,

I have the coefficients u (viscosity), K (permeability) and C_E (Ergun constant) that describe my porous material (see 16.png).

I don't know how to relate them with the coefficients D and F that the Darcy-Forchheimer equation in the form of 17.png that OF uses.

Any help would be appreciated.

Thanks.
Pierre

[TobiF]

Hi Pierre,
did you check
Darcy-Forchheimer law for specifying Porous Zones

I guess post 23 should give the answer...

When dp = a*v² + b*v

Following the equation (2) page 2

a = 1/2 * rho * F => F = 2a/rho [no unit]
b = visc * D => D = b /visc [1/m]

with

a = -Ce*rho/sqrt(K)
b = -µ/K

[pilafa]

Hi TobiF,

Great! it is exactly what I wanted.

I small precision: I understand that I have to divide by the length of the porous zone to fit OF units:

When we compare the units, the missing 1/m comes from dp/dx where dx is the size of the porous medium in the x direction (considering an anisotrop medium).

Finally :
Code:
F = 2 * a / (rho * dx)

D = b / (visc * dx)

Thanks!