Using an acoustic technique profile analysis we have studied the growth of viscous fingers inside 3D porous media. The experimental data support the definition of an instability parameter which captures the essential features of the viscous fingering; its dependence on the viscosity ratio, on the flow rate, and on the nature of the porous medium is compared to available theory. Our data demonstrate the predicted crossover between diffusive and linear growth and the growth enhancement due to coupling between large viscosity ratio and velocity-dependent hydrodynamic dispersion.

• Received 17 June 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.2005