Analogue modelisation of flow through a double porosity media with discrete conduits

In this study we describe a three dimensional meter scale experimental system used to investigate flow through a double porosity media that includes discrete flow conduits. This hybrid discrete-continuum approach is used to simulate water flow in karstic carbonate aquifers. A rectangular tank is filled with stacked ceramic foam blocks laterally separated with a constant aperture. The tank outlet is connected to a drilled conduit network that follows the overlying aperture scheme at the lower base of the system. Above the system, an artificial rain is set with a sprinkler. Working with an analogue model seems interesting as materials, initial and boundary conditions are fully known. Ceramic foam provides a uniform matrix material allowing different porosities and hydraulic conductivities. The modulability of the aperture pattern and size let different experiment setting possibilities. A variation in the drilled number of holes in the conduit network will change its draining capacity. And, finally the artificial rain rate and location are well characterized. The system is adequately instrumented in order to 1) observe hydraulic head distributions in both matrix and fracture medium and 2) record spring flow fluctuations. Moreover, any experience is very reproducible. This analogue modeling approach allows an observation of both fracture and matrix flow contribution to a spring with a drained double porosity media with discrete conduits. Comparison of in situ measured data with a finite element numerical model and an analytical solution are shown.