Viscous fingering of miscible fluids in an anisotropic radial Hele-Shaw cell: Coexistence of kinetic and surface-tension dendrite morphology types and an exploration of small-scale influences

The evolution of viscous fingering morphology is examined for the case of a system of miscible fluids in an anisotropic radial Hele-Shaw cell. It is s hown that dendritic morphologies similar to the kinetic and surface-tension morphology types coexist for this case. The critical role of the means of introducing anisotropy in the Hele-Shaw cell is established, and an explana tion of the pattern behavior is offered on the basis of shape discontinuiti es of the individual elements of the lattice used to induce anisotropy. The ramifications of such an explanation are experimentally verified by demons trating a clear difference in the morphology evolution in two halves of a s ingle Hele-Shaw cell, one half of which contains square lattice elements, a nd the other half of which contains circular lattice elements. [S1063-651X( 99)14202-8].