Displacement flow in an Elastic Fracture

We revisit the classical displacement flow problem in a growing fracture. We report an experimental study of water injection in an oil-filled fracture in an elastic brittle matrix. The initial oil-filled crack is penny-shaped, and its growth dynamics is controlled by the stress intensity factor, in what is known as the toughness regime of propagation. Upon injection of water, the crack further expands. We investigate the propagation of the fracture and the displacement of the oil/water interface. Our experiments show that the propagation dynamics in this displacement configuration differs from the single-fluid injection. Scaling arguments are provided to explain the experimental results and provide insights into the underlying physics.