New Viscous Fingering Mechanisms at High Viscosity Ratio and Peclet Number Miscible Displacements

Full nonlinear simulation of the viscous fingering instability of miscible flow displacements in a rectilinear Hele-Shaw cell are conducted using a hybrid numerical algorithm. The algorithm allowed the modeling of the flow at relatively high values of the mobility ratio and Peclet number, representing the ratio of convective and dispersive forces. New finger structures, some reminiscent of fractal patterns observed in previous experimental studies, are reported. An explanation of the mechanisms responsible for the new finger structures is presented based on the development of the flow velocity field. The flow is also characterized qualitatively through a spectral analysis of the average concentration and an analysis of the variations of the relative finger width and relative contact area. General observations regarding the conditions for the development of complex finger structures are presented.