arXiv subjects

Jordi Ortín

Publications and source records attributed to Jordi Ortín.

3 recordsLinked to original sources

arXiv2018

Laning, Thinning and Thickening of Sheared Colloids in a Two-dimensional Taylor-Couette Geometry

We investigate the dynamics and rheological properties of a circular colloidal cluster that is continuously sheared by magnetic and optical torques in a two-dimensional (2D) Taylor-Couette geometry. By varying the two driving fields, we obtain the system flow diagram and report the velocity profiles along the colloidal structure. We then use the inner magnetic trimer as a microrheometer, and observe continuous thinning of all particle layers followed by thickening of the third one above a threshold field. Experimental data are supported by Brownian dynamics simulations. Our approach gives a unique microscopic view on how the structure of strongly confined colloidal matter weakens or strengthens upon shear, envisioning the engineering of rheological devices at the microscales.

cond-mat.soft↗

arXiv2010

Reply to the comment on "Avalanches and Non-Gaussian Fluctuations of the Global Velocity of Imbibition Fronts"

In [R. Planet, S. Santucci and J. Ortin, Phys. Rev. Lett. 102, 094502 (2009)], we reported that both the size and duration of the global avalanches observed during a forced imbibition process follow power law distributions with cut-offs. Following a comment by G. Pruessner, we discuss here the right procedure to perfom, in order to extract reliable exponents characterising those pdf's.

cond-mat.stat-mech↗

arXiv2002

Anomalous Roughening in Experiments of Interfaces in Hele-Shaw Flows with Strong Quenched Disorder

We report experimental evidences of anomalous kinetic roughening in the stable displacement of an oil-air interface in a Hele-Shaw cell with strong quenched disorder. The disorder consists on a random modulation of the gap spacing transverse to the growth direction (tracks). We have performed experiments varying average interface velocity and gap spacing, and measured the scaling exponents. We have obtained beta=0.50, beta*=0.25, alpha=1.0, alpha_l=0.5, and z=2. When there is no fluid injection, the interface is driven solely by capillary forces, and a higher value of beta around beta=0.65 is measured. The presence of multiscaling and the particular morphology of the interfaces, characterized by high slopes that follow a Lévy distribution, confirms the existence of anomalous scaling. From a detailed study of the motion of the oil--air interface we show that the anomaly is a consequence of different local velocities over tracks plus the coupling in the motion between neighboring tracks. The anomaly disappears at high interface velocities, weak capillary forces, or when the disorder is not sufficiently persistent in the growth direction. We have also observed the absence of scaling when the disorder is very strong or when a regular modulation of the gap spacing is introduced.

cond-mat.dis-nn↗