New advances in the study hydrodynamic turbulence in disordered medium

The scientific paper is authored by Jordi Ortín and Xavier Clotet, from the Department of Structure and Constituents of Matter of the University of Barcelona (UB), and Stephane Santucci, from the Physics Laboratory of the Ecole Normale Supérieure de Lyon (France), affiliated centre with the French National Centre for Scientific Research (CNRS).

An intermittent dynamics characterises turbulence. This property has recently been observed in numerical simulations in porous media flows. The new study published in the Physical Review Letters is the first experimental evidence and detailed characterization of intermittency in fluid invasion of confined heterogeneous media.

Professor Jordi Ortín, coordinator of the Consolidated Research Group on Nonlinear Physics of UB and expert on dynamical systems in disordered medium, affirms that “intermittency is a key concept in fluid dynamics because it reveals that the occurrence of anomalous and complex time correlations in very short periods of time. Thus, understanding the physical mechanism that affects turbulence remains a challenge in statistical physics”.

Turbulence: complex and disordered movements in a fluid

To study the nature of intermittency is essential to continue investigating the phenomenon of turbulence. Recent studies suggest that intermittency could be related to the properties of the fluctuations of the energy flux shared by different systems displaying an energy cascade. This is the case, for instance, of the changes in energy rates that occur in the phenomenon of hydrodynamic turbulence.

In the new study, the UB research group used a laboratory model of an open fracture that enables to control the statistical properties of the disorder medium accurately. Moreover, the study expanded the number of experimental parameters by using five silicone oils of different viscosities and a wider range of imposed flow rates. This experimental methodology has enabled to have many statistical data which are necessary to analyse intermittence.

Particularly, the research group observed how a series of silicone oils of different viscosities (from 10 to 350 cP) behave. These fluids are stable and difficult to pollute; although they have a wide range of viscosities, their surface tension hardly varies. According to authors, a multiscale analysis in space and time revealed all the distinguishing features of an intermittent dynamics in the systems studied.

The experimental evidence first described by the research group will contribute to the development of new theoretical and experimental approaches of intermittency. The new study suggests that some characteristics of intermittency observed in the system indicate the existence of an inverse cascade resulting from fluid incompressibility. This research line on the dynamical properties of fluid fronts has a wide range of applications in the field of the secondary recovery of hydrocarbons, irrigation and soil pollution, filtration to remove pollutants and other highly topical issues in engineering.