A NOVEL APPROACH TO TURBULENT MULTIPHASE FLOW IMAGING: FLOW IN 3D PRINTED KARSTIC CONDUITS

Flow and contaminant transport in karstic aquifers differ drastically from porous media, but little work has been done to quantify the transport of non-aqueous phase liquids (NAPLs) in karst. 3D printing of fractures has been performed in the past to evaluate multiphase transport at the core scale, but examination of flow in larger conduits using this technique is lacking in the literature. We printed cylindrical cores with karstic conduits out of acrylonitrile butadiene styrene (ABS) plastic to facilitate imaging of turbulent flow in conduits carrying water and NAPLs. Conduit apertures are elliptical to mimic common phreatic tube shape and measure more than 1cm to promote turbulent flow. Fused filament fabrication, the process used during construction, produces permeable prints. To minimize permeability in the conduit, we moderately dissolved cores using acetone vapor; this allowed dissolved plastic to fill and harden in pore spaces making the walls impermeable.

Flow of water and NAPL under different gradients is imaged with a modified X-Ray Computed Tomography (CT) scanner. Radiologic agents added during experimentation increase the contrast between water and non-aqueous fluids and clarify flow paths. X-ray CT stitches together still images to allow for temporal analysis of flow.

As a novel technique in karst modeling, this approach requires further validation. To that end, this experimental setup is reproducible and can be modified to accurately reflect more complex cave geometry, conduit roughness, and in-conduit sediment piles. All of these variables potentially influence NAPL transport and storage in conduits.