An Experimental Study of Porous Medium Flow in Converging Boundary

Objectives: Since 1856, Darcy's equation is used to analyse the ground water flow. This equation can be applied only in laminar regime of flow. No suitable equation is available to analyse other regimes of flow. During the pumping the water from well, the water around well flows in converging pattern towards well. The analysis of flow of water around wells is a problem in converging boundary through porous soils or sands. Generally, Dupuit's equation is used to analyse the flow around the well. One of the drawback in Dupuit's equation is it can be used only in laminar flow, since, this equation used Darcy's concept. No equation is available to analyse other than laminar flow in converging pattern towards well. Therefore, this situation motivated to think to design a sector of well model to conduct experiments on porous medium flow in converging boundary for all regimes of flow to estimate the discharge of a well. Methodology: In order to achieve the objective, a converging permeameter (a sector of a well model) is planned, designed and experimented. In this study, experiments have been conducted on porous medium in converging flow permeameter for all regimes of flow. From the experimentation of converging boundary, data like discharge, hydraulic gradient and velocity are calculated. Further, a new non-dimensional form of equation is also derived relating hydraulic gradient with Reynolds number. Findings: A set of graphs are drawn between hydraulic gradient and velocity, using Darcy's range of velocities and corresponding hydraulic gradient. These graphs are compared with Darcy's graph and the validity of Darcy's equation is verified. The trends of the present graph is coinciding with that of Darcy's graph such that the validation of this experimentation is checked. Another set of graphs are also drawn with hydraulic gradient versus velocity for all regimes of flow. A polynomial second degree equation (i=a1 Vb 2 +k'Vb) has been proposed relating hydraulic gradient with bulk velocity in laminar and turbulent regimes. Hence this project result proves that, using this equation and corresponding constants discharge of a well can be estimated even if the flow is laminar and turbulent. Applications: The relation between hydraulic gradient and Reynolds number is obtained as i=0.0004 Re0.5. Substituting hydraulic gradient in this equation from field observations, Reynolds number can be find out. From the Reynolds number seepage velocity can be find out and corresponding discharge may be calculated in a well for any regime of flow which superfluous Dupuit's equation.