PRESSURE LOSS

Dear LB Researchers,

I am simulating the flow through a porous medium in a 2-D channel with below simulation parameters

ro_lb=1: initial value
lattice velocity=c=1

dx_lb=1/100
dt_lb=dx_lb/c=1/100
u_lb=0.003=u_ph

Channel Length=10m
Channel width=1m
Re=5
Nx=1000
NY=100

After simulation we have ro_lb=1.17 before porous zone and ro_lb=1.073 after porous zone. How can I calculate the physical pressure loss due to the presence of the porous zone?

Thanks in advance