Article révisé par les pairs
Résumé : Miscible viscous fingering is studied experimentally in the presence of a nonmonotonic viscosity profile due to nonideal mixing properties in a porous medium consisting in a micropillar array column used for chromatographic applications. In this setup, a mobile phase composed of an aqueous solution of methanol displaces a miscible finite-size sample containing mainly water. Due to a local buildup by nonideal mixing of maxima in the viscosity profile, fingering is observed at both the frontal and rear miscible interfaces of the sample phase, however with different spatial extents. The influence on the fingering dynamics of the pressure in the column and of the viscosity of the mobile or sample phases is analyzed.