Experimental flow in various porous media and reconciliation of Forchheimer and Ergun relations

- Same porous medium exhibits different permeabilities in different flow regimes.
- The appropriate characteristic length is square root of Darcy-regime permeability.
- Apparent difference between Ergun and Forchheimer equations is explained.
- Ergun and Forchheimer equations are reconciled using the hydraulic radius theory.
- Correlations are given in terms of friction factor and Reynolds number.