Experimental study of finger behavior due to miscible viscous and gravity contrast in a porous model

ABSTRACT

Miscible viscous fingering instability in a rectangular flow cell with engraved porous matrix was examined through experimental measurements and finger patterns were discussed in details to find out how fingers were generated or coalesced. Effects of injection rate, viscosity contrast, and gravitational field on instabilities were investigated based on Péclet number (Pe), viscosity ratio (VR), and Rayleigh number (Ra). Image processing techniques were performed to measure quantitative parameters including breakthrough time, sweep efficiency, fractal dimension, and perimeter of the interface. It was revealed that as the Péclet number and viscosity ratio increase, more complex fingers were produced and less sweep efficiency was reported. In this respect, when gravitational field was exerted by rotating the cell, new instability known as Rayleigh–Taylor amplified the former fingers.

KEYWORDS:

• Viscous fingering instability
• Rayleigh–Taylor instability
• porous media
• miscible flow displacement
• experiment apparatus