arXiv subjects

M. F. Carusela

Publications and source records attributed to M. F. Carusela.

9 recordsLinked to original sources

arXiv2026

Swirl flow in microchannels: patterned slip walls enhance heat transport

Microchannel heat sinks (MCHS) are widely used for thermal management in high-power electronics due to their ability to dissipate large heat fluxes with minimal coolant consumption. While numerous strategies - such as geometric modifications, surface disruptions, and enhanced coolant formulations - have been explored to improve heat transfer, many of these approaches increase hydraulic resistance and pumping power requirements. Recent studies have shown that slip/no-slip wall patterns can enhance flow rates and convective heat removal without additional energy input, and that patterned microstructures can induce secondary swirling motions known to promote mixing and heat transfer. Motivated by these findings, we investigate a slip/no-slip pattern specifically designed to generate swirl flow inside a straight microchannel. Building upon prior work on passive chaotic advection and boundary-condition engineering, we assess the hydrodynamic and thermal performance of this patterned configuration under conditions relevant to laminar microchannel cooling. Our results demonstrate that appropriately arranged slip/no-slip regions can induce swirl without geometric perturbations or increased pumping power, ultimately improving heat transfer efficiency at fixed volumetric flow rate. This study highlights the potential of boundary-condition patterning as a simple, energy-neutral strategy for enhancing the performance of microfluidic heat-transfer devices.

physics.flu-dyn↗

arXiv2024

Modeling considerations about a microchannel heat sink

Many computational studies on hotspot microfluidic cooling devices found in the literature rely on simplified assumptions and conventions that do not capture the full complexity of the conjugate thermal problem, such as constant thermophysical fluid properties, radiation and free air convection on the external walls. These assumptions are generally applied to typical microfluidic devices with a large number of microchannels and operating at Reynolds numbers between 100-1000. A one microchannel chip is a suitable starting point to analyze more systematically the implications of these assumptions, in particular at lower Reynolds numbers. Although it is a simpler system, it has been studied experimentally and numerically as a basic block of a thermal microfluidic device. In this work we analyze the modeling of the overall heat transfer from a hotspot to a microfluidic heat sink, focusing on the effect of the different thermal transfer mechanisms (conduction, convection and radiation), temperature-dependent thermophysical properties of the fluid and the chip material. The study is developed as a function of the pressure difference applied to the system based on simulations performed using a Finite Volume Method. Analyzing and comparing the different contributions to the energy losses, this work provides a critical discussion of the usually considered approximations, in order to make a reliable modeling of the overall thermal performance of a single rectangular straight channel embedded in a PDMS microfluidic chip.

physics.flu-dyn↗

arXiv2019

Evolution of instabilities in filament buckling processes

In this work we study the dynamical buckling process of a thin filament immersed in a high viscous medium. We perform an experimental study to track the shape evolution of the filament during a constant velocity compression. Numerical simulations reproduce the dynamical features observed for the experimental data and allow quantifying the filament's load. We observe that both the filament's load and the wavenumber evolve in a step-wise manner. To achieve a physical insight of the process we apply a theoretical model to describe the buckling of a filament in a viscous medium. We solve a hydrodynamic equation in terms of normal modes for clamped-clamped boundary conditions and applied constant load. We find a good agreement with experimental data and simulations, suggesting that the proposed mechanistic model captures the essential features underlying the dynamical buckling process.

cond-mat.soft↗

arXiv2016

Frequency thermal response and cooling performance in a microscopic system with a time-dependent perturbation

Following the nonequilibrium Green's function formalism we study the thermal transport in a composite chain subject to a time-dependent perturbation. The system is formed by two finite linear asymmetric harmonic chains subject to an on-site potential connected together by a time-modulated coupling. The ends of the chains are coupled to two phononic reservoirs at different temperatures. We present the relevant equations used to calculate the heat current along each segment. We find that the system presents different transport regimes according the driving frequency and temperature gradients. One of the regimes corresponds to a heat pump against thermal gradient, thus a characterization of the cooling performance of the device is presented.

cond-mat.mes-hall↗

arXiv2015

Thermal transport in a 2D stressed nanostructure with mass gradient

Inspired by some recent molecular dynamics (MD) simulations and experiments on suspended graphene nanoribbons, we study a simplified model where the atoms are disposed in a rectangular lattice coupled by nearest neighbor interactions which are quadratic in the interatomic distance. The system has a mechanical strain, and the border atoms are coupled to Langevin thermal baths. Atom masses vary linearly in the longitudinal direction, modeling an isotope or doping distribution. This asymmetry and tension modify thermal properties. Although the atomic interaction is quadratic, the potential is anharmonic in the coordinates. By direct MD simulations and solving Fokker--Planck equations at low temperatures, we can better understand the role of anharmonicities in thermal rectification. We observe an increasing thermal current with an increasing applied mechanical tension. The temperatures and thermal currents vary along the transverse direction. This effect can be useful to establish which parts of the system are more sensitive to thermal damage. We also study thermal rectification as a function of strain and system size.

cond-mat.mes-hall↗

arXiv2010

Work-Energy theorem in rotational reference frames

In standard textbooks of college physics, the Work Energy Theorem is usually presented for inertial frames of references and it is clear that energy is conserved when there is not net work of interaction forces. But what happens when energy and work are calculated in a non inertial frame of reference? This important issue is frequently avoided. Recently an extension of the theorem was derived for reference systems in traslational motion. Here we address the theorem for two observers in relative rotation showing explicitly the differences for them. We illustrate the problem with practical examples.

physics.class-ph↗

arXiv2010

Modeling Rectification Effects in Mesoscopic Superconducting Devices

We study thermal fluctuations and capacitive effects on small Josephson Junction Rings (JJR) that mimics the rectification phenomena recently observed in triangle shaped mesoscopic superconductors, due to the superposition of the field induced persistent current with the bias current. At finite temperature we predicted that the amplitude of the rectified signal depends strongly on the current contacts configuration on the JJR, in coincidence with experiments. In addition we analize the range of parameters where a closed loop of capacitive junctions is an appropriate model to explain the experimental observations. We conclude that the closed loop of weak links, a JJR, is a simple, robust and good enough model to explain the observed voltage rectification effects on mesoscopic superconducting samples for a wide range of temperature.

cond-mat.supr-con↗

arXiv2008

Transport and dynamical properties of inertial ratchets

In this paper we discuss the dynamics and transport properties of a massive particle, in a time dependent periodic potential of the ratchet type, with a dissipative environment. The directional currents and characteristics of the motion are studied as the specific frictional coefficient varies, finding that the stationary regime is strongly dependent on this parameter. The maximal Lyapunov exponent and the current show large fluctuations and inversions, therefore for some range of the control parameter, this inertial ratchet could originate a mass separation device. Also an exploration of the effect of a random force on the system is performed.

cond-mat.other↗

arXiv1999

Large Global Coupled Maps with Multiple Attractors

A system of N unidimensional global coupled maps (GCM), which support multiattractors is studied. We analize the phase diagram and some special features of the transitions (volume ratios and characteristic exponents), by controlling the number of elements of the initial partition that are in each basin of attraction. It was found important difference with widely known coupled systems with a single attractor.

chao-dyn↗