Marcel Moura

Research Interests

Flow and pattern formation in porous media

Viscous fingering in a porous mediumWe perform experiments on the displacement of one fluid phase by another inside a porous network. The use of artificial micromodels allows us to access details of the fluid dynamics that are completely unnatainable in real porous media, such as rocks and soils. This system presents a rich variety of invasion patterns, from compact invasion to stunning fractal structures, such as the viscous fingering pattern shown here. The topic is of wide interest to the industry as well, due to its immediate relevance to the environment sector (remediation of soils, plants irrigation) and energy sector (recovery of hydrocarbons from natural reservoirs, efficient solar cells).

Burst dynamics in slow porous media flows

invasion burstsWhen air invades a porous network previously filled with a wetting liquid, an interesting series of invasion bursts are observed, extending over many time and lenght scales. This process occurs in an intermittent stick-slip manner, in which long intervals of apparent stagnation are interrupted by the fast invasion bursts. In the image on the right the different bursts are colored randomly to help their visualization.

Fracture dynamics in brittle solids

Fracture propagationThe understanding of how fractures propagate is crucial for several aspects of human activity. Typically we don't want things to break, so we should better understand well why and how they break, such that we can better avoid it from happening. We perform experiments of the nucleation and growth of in-plane fractures in a transparent PMMA block. By using high-speed imaging and microscopy techniques we can access the occurrence of fast phenomena at the fracture tip which play an important role in the development of the fractures. On the image on the right, the fracture propagates upwards, the darker region corresponding to the fractured zone.

Vortex dynamics in classical fluids

Foeppl vorticesFrom fast tornados that can make a house fly to calm whirlpools that only make the bathtub more fun, vortex phenomena is all around us. They are important for the lift of an airplane but can also induce dangerous vibrations in the cables of a suspension bridge. We employ analytical models to describe the dynamics of vortices in ideal fluids in the presence of solid obstacles. On the right we show the pair of counter-rotating vortices (Föppl pair) that apears in the wake of a cylinder that is placed in a fluid stream.