arXiv subjects

Franco Tapia

Publications and source records attributed to Franco Tapia.

5 recordsLinked to original sources

arXiv2025

Tangential Forces Govern the Viscous-Inertial Transition in Dense Frictional Suspensions

We present particle-resolved simulations of dense frictional suspensions undergoing the viscous-inertial transition using pressure-imposed rheology. By varying the fluid viscosity, shear rate, and granular pressure, we find that the transition is independent of the packing fraction and occurs at a Stokes number of 10. Our results reveal that the shear stress exhibits a slower transition than the particle pressure, attributed to the combined effect of tangential contact and lubrication forces, as the frictional particles concurrently shift from rolling to sliding contacts. This shift is controlled by the Stokes number but also by the distance from jamming. Additionally, we examine the role of increasing inter-particle friction on the viscous-inertial transition.

cond-mat.soft↗

arXiv2023

Rheology of suspensions of non-Brownian soft spheres across the jamming and viscous-to-inertial transitions

The rheology of suspensions of non-Brownian soft spheres is studied across jamming but also across the viscous and inertial regimes using a custom pressure- and volume-imposed rheometer. The study shows that the granular rheology found for suspensions of hard spheres can be extended to a soft granular rheology (SGranR) by renormalizing the critical volume fraction and friction coefficient to pressure-dependent values and using the addition of the viscous and inertial stress scales. This SGranR encompasses rheological behaviors on both sides of the jamming transition, resulting in an approximate collapse of the rheological data into two branches when scaled with the distance to jamming, as observed for soft colloids. This research suggests that suspensions of soft particles across flow regimes can be described by a unified SGranR framework around the jamming transition.

cond-mat.soft↗

arXiv2022

Viscous-inertial transition in dense granular suspension

Granular suspensions present a transition from a Newtonian rheology in the Stokes limit to a Bagnoldian rheology when inertia is increased. A custom rheometer which can be run in a pressure or a volume-imposed mode is used to examine this transition in the dense regime close to jamming. By varying systematically the interstitial fluid, shear rate, and packing fraction in volume-imposed measurements, we show that the transition takes place at a Stokes number of 10 independent of the packing fraction. Using pressure-imposed rheometry, we investigate whether the inertial and viscous regimes can be unified as a function of a single dimensionless number based on stress additivity.

cond-mat.soft↗

arXiv2019

The influence of surface roughness on the rheology of immersed and dry frictional spheres

Pressure-imposed rheometry is used to examine the influence of surface roughness on the rheology of immersed and dry frictional spheres in the dense regime. The quasi-static value of the effective friction coefficient is not significantly affected by particle roughness while the critical volume fraction at jamming decreases with increasing roughness. These values are found to be similar in immersed and dry conditions. Rescaling the volume fraction by the maximum volume fraction leads to collapses of rheological data on master curves. The asymptotic behaviors are examined close to the jamming transition.

cond-mat.soft↗

arXiv2006

Experimental evidence of shock mitigation in a Hertzian tapered chain

We present an experimental study of the mechanical impulse propagation through a horizontal alignment of elastic spheres of progressively decreasing diameter $ϕ_n$, namely a tapered chain. Experimentally, the diameters of spheres which interact via the Hertz potential are selected to keep as close as possible to an exponential decrease, $ϕ_{n+1}=(1-q)ϕ_n$, where the experimental tapering factor is either $q_1\simeq5.60$~% or $q_2\simeq8.27$~%. In agreement with recent numerical results, an impulse initiated in a monodisperse chain (a chain of identical beads) propagates without shape changes, and progressively transfer its energy and momentum to a propagating tail when it further travels in a tapered chain. As a result, the front pulse of this wave decreases in amplitude and accelerates. Both effects are satisfactorily described by the hard spheres approximation, and basically, the shock mitigation is due to partial transmissions, from one bead to the next, of momentum and energy of the front pulse. In addition when small dissipation is included, a better agreement with experiments is found. A close analysis of the loading part of the experimental pulses demonstrates that the front wave adopts itself a self similar solution as it propagates in the tapered chain. Finally, our results corroborate the capability of these chains to thermalize propagating impulses and thereby act as shock absorbing devices.

cond-mat.soft↗