Experimental Study on Aero Conductivity of Porous Media

To study the variation pattern of aero conductivity of different porous media under low pressure conditions, three kinds of media are selected. These include sandy clay loam, fine sand, and medium sand, and air as fluid to conduct soil column ventilation tests. Pressure at both ends of the columns is measured under different ventilation flow rates during testing. The test results show that the aero conductivity, solved by Darcy's law, is not a constant. It is a variable, which increases first when air flow velocity is less than 0.258 7 cm/s for sandy clay loam, 0.637 3 cm/s for fine sand and then decreases when air flow velocity is bigger than that with the increase of the ventilation flow rate when the medium is determined. By analyzing various factors that influence the flow resistance, the reasons for variation in aero conductivity are found as follows: first, the change of pore structure results in better ventilation; second, the relationship between pressure head loss and air flow velocity is nonlinear, and it is beyond the condition of the laminar flow domain to which Darcy's law can be applied, when the air flow rate increases to a certain value and the flow velocity is in the transition range to turbulent flow.