In this chapter we will consider laminar flow through porous material beds. Throughout history, flows through porous media have been studied both experimentally and theoretically. The dependent variables that have to be determined are the pressure drop ΔP (N m⁻²) through the porous material bed and the fluid volume flow rate Q (m³ s⁻¹) as functions of porous material void fraction, characteristic void diameter, porous material bed length and area, and fluid viscosity. Henri Darcy performed sand column experiments in the nineteenth century in order to determine the ΔP versus Q relationship for...