Philipp Forchheimer
Philipp Forchheimer (7 August 1852 in Vienna – 2 October 1933 in Dürnstein, Lower Austria) was an Austrian engineer, a pioneer in the field of civil engineering and practical hydraulics. He was professor in Istanbul, Aachen and Graz. He introduced mathematical methodology to the study of hydraulics, thus establishing a scientific basis for the field. He was director of the Graz University of Technology until 1897. In addition to his teaching, he worked as a consultant for construction projects. He made proposals for the construction of a tunnel under the English Channel. Modification to Darcy's Law. Forchheimer proposed  a modification to Darcy's Law, describing fluid flow through packed beds in 1901. This also had a significant influence on the development of the Ergun equation. formula_1 where: formula_2 is the pressure drop across the bed, formula_3 is the viscosity of the fluid, formula_4 permeability (const.), formula_5 is the (area-averaged) velocity of the fluid, formula_6 is an empirical constant, formula_7 is the density of the fluid. A more general expression of the friction factor follows from Forchheimers modification: formula_8 where formula_9 is the Reynold's number and C is a constant.