Speaker
Description
Solute mixing often occurs in multiphase flows within the vadose zone, where drainage and imbibition alternately saturate and desaturate the porous substrate. While our understanding of mixing in porous media has rapidly advanced to encompass steady multiphase flows, our knowledge remains incomplete in dynamic multiphase flows such as drainage and imbibition, where the bursty movements of fluid interfaces can potentially modify mixing. Using 3D imaging, refractive-index matching, and laser-induced fluorescence, we have comprehensively studied the mixing of a solute plume in proximity to a drainage front moving through a glass beadpack. From the time-resolved 3D images, we have identified a substantial enhancement of mixing rates by moving drainage fronts which depends on the significance of bursts to the interface motion as characterized by the capillary number. The pore-scale images reveal that interfacial bursts in the individual pores produce transverse motions that are otherwise absent in steady flows, and these motions enhance the alternate stretching and folding of solute distributions to increase mixing rates. These experimental findings offer perspectives for predicting and controlling the diversity of chemical transport and reaction processes in the subsurface.
| Country | Norway |
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