Experimental Investigations on pressure pulses through different porous media

Abstract

Fluid mechanics traditionally and significantly investigate transient flows, which find applications ranging from flows in pipelines to porous media flows linked to water extraction and hydrocarbons. However, the nature of transient flows in closed pipes and porous media differs significantly due to the magnitude of energy losses in these two flows. Pipe systems experience relatively low energy dissipation rates, and one can describe them using partial differential equations (PDEs), such as the classic wave equation, which exhibit a hyperbolic nature. On the other hand, porous media flows are dominated by energy losses, and sudden changes associated with transient flows propagate gradually, exhibiting behavior similar to diffusion, characterized by parabolic-type PDEs. Although experiments have extensively investigated each of these flow conditions, they have yet to consider the transition between these two conditions, and there is a scarcity of transient flow datasets for highly conductive porous media. The Water Resources Laboratory at Auburn University constructed an experimental apparatus to evaluate transient flow characteristics for six distinct porous media, each having unique diameters and materials. Each porous medium underwent evaluation for three different types of unsteady flows created by varying boundary conditions. The experimental findings revealed that transient signals gradually exhibited parabolic-type behavior as hydraulic conductivity decreased. In contrast, large porous media exhibited behavior consistent with closed pipe flows. The results indicate that the transition between these two regimes should be observed for porous media near or under a characteristic dimension of 2 mm.