Experimental study on non-Darcian flow in two kinds of media with different diameters

The linear relationship between the hydraulic gradient and specific discharge for Darcy s law is no longer valid when the specific discharge is large enough. This means that non-Darcian flow occurs. An experiment was conducted by using 1-D sand columns with various hydraulic gradients to establish the relationship between the hydraulic gradient and specific discharge passing through two kinds of porous media with diameters of 0.5 mm-0.63 mm and 0.63 mm-1.25 mm respectively. The hydraulic resistivity and Reynolds number were used to identify the occurrence of non-Darcian flow. The results indicate that both the Forcheimer and lzbash equations can well describe the flow. Both the linear term and nonlinear term of hydraulic gradient representing the energy dissipation due to inertia force and viscous force respectively are increasing with the increase of specific discharge. At the same time, the portion of nonlinear term in hydraulic gradient increases continuously. The nonlinear term of hydraulic gradient is 40% and 50%, and the critical Reynolds number is 22-27 and 52-104 for two kinds of media respectively. The critical Reynolds number for occurring of non-Darcian flow increases with grain diameter.

Experimental study on non-Darcian flow in two kinds of media with different diameters Academic Article