So exactly what non-linear waves are we talking about here?

Additionaly, would using Forchheimer instead prinicpaly change the pressure diffreence magnitudes required to generate a given speed?

Because I gave a hard time imagining 10 Pa pressure fluctuations cause a 10 cm/s speed in a packed bed. I am modelling combustion in porous media and it is very sensitive to velocity: $u=0.05$ m/s and $u=0.25$ m/s can yeild quite different results. And accoring to Darcy's law it seems that velocities would fluctate randomly in those value ranges because it is a matter of a few Pa fluctuations in pressure.

In that case, when is Darcy's law ever applicible for gas flow anyway? I mean, if even with a perssure difference of 10 Pa it is already unreasonable..

Everything in SI.

I think it does, it gives a reference too look up the BCs setup, fluent's theory guide is incredibly thorough.