1,720,975 research outputs found
Nonlinear fluctuating hydrodynamics with many conserved fields: The case of a three-dimensional anharmonic chain
Full text linkWe propose a model for a chain vibrating in three dimensions, with first neighbors anharmonic interatomic potential, which depends on their distance, and subjected to an external tension. In the framework of the nonlinear fluctuating hydrodynamic theory, which was successfully applied to one-dimensional chains, we obtain a heat mode, two longitudinal, and four transverse sound modes. We compute their spatiotemporal correlations comparing the theoretical results with molecular dynamics simulations, finding a good agreement for high temperatures. We find that the transverse sound modes behave diffusively, meanwhile the heat and longitudinal sound modes behave superdiffusively, exploring their possible scaling functions and characteristic exponents.Fil: Barreto, Roberto Antonio. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Carusela, María Florencia. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Monastra, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentin
Thermal diode assisted by geometry under cycling temperature
No full textTechnological progress in electronics usually requires their use in increasingly aggressive environments, such as rapid thermal cycling and high power density. Thermal diodes appear as excellent candidates to thermally protect critical electronic components and ensure durability and reliability. We model the heat transport across a square plate with a hole subjected to an oscillating external temperature, such spatial and temporal symmetries are broken. We find rectification of the heat current that strongly depends on the frequency and the geometry of the hole. This system behaves as a thermal diode that could be used as part of a thermal architecture to dissipate heat under cycling temperature conditions.Fil: Zurdo, Luis Luciano. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Chej, Lucas Gabriel. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Monastra, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Carusela, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentin
Thermal transport across a vacuum gap between two reconstructed Si-nanomembranes
No full textRevista con referatoFil: Carusela, María Florencia. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina.Fil: Carusela, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Mancardo Viotti, Agustin Matías. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina.Fil: Mancardo Viotti, Agustin Matías. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Bea, Edgar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Monastra, Alejandro Gabriel. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina.Fil: Monastra, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.En este trabajo, examinamos la energía de interacción entre dos nanomembranas de silicio reconstruidas mediante un enfoque de enlace fuerte basado en la densidad funcional (DFTB), centrándonos en su impacto en la conductancia térmica a través de un nanogap. Al combinar el método DFTB con un modelo atomístico armónico, calculamos los modos vibracionales (fonones) y los tiempos de equilibrio, que están directamente relacionados con la conductancia térmica. Nuestros hallazgos muestran que la reconstrucción de la superficie y la alineación relativa de las estructuras diméricas enfrentadas influyen significativamente en la contribución fonónica a la conductancia térmica. Si bien el modelo armónico simplifica las interacciones del sistema real, nuestros resultados concuerdan con estudios previos, lo que demuestra que este modelo captura aspectos clave de la transferencia de calor mediada por fonones. En resumen, nuestro enfoque proporciona un método computacionalmente eficiente para comprender la transferencia de calor fonónica a través de nanogaps, con implicaciones para el diseño de sistemas de gestión térmica a nanoescala.In this work we examine the interaction energy between two reconstructed silicon nanomembranes using a density-functional-based tight-binding (DFTB) approach, focusing on its impact on thermal conductance across a nanogap. By coupling the DFTB method with a harmonic atomistic model, we calculate the vibrational modes (phonons) and the equilibration times, which are directly related to the thermal conductance. Our findings show that surface reconstruction and the relative alignment of facing dimer structures significantly influence the phononic contribution to thermal conductance. Although the harmonic model simplifies the interactions of the real system,our results agree well with previous studies, demonstrating that this model captures key aspects of phonon-mediated heat transfer. Overall, our approach provides a computationally efficient method for understanding phononic heat transfer across nanogaps, with implications for designing nanoscale thermal management systems
Modeling considerations about a microchannel heat sink
No full textMany 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 and 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), and 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, to make a reliable modeling of the overall thermal performance of a single rectangular straight channel embedded in a polydimethylsiloxane microfluidic chip.Fil: Chej, Lucas Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Monastra, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Carusela, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentin
Thermal expansion in nanoresonators
Full text linkInspired by some recent experiments and numerical works related to nanoresonators, we perform classical molecular dynamics simulations to investigate the thermal expansion and the ability of the device to act as a strain sensor assisted by thermally-induced vibrations. The proposed model consists in a chain of atoms interacting anharmonically with both ends clamped to thermal reservoirs. We analyze the thermal expansion and resonant frequency shifts as a function of temperature and the applied strain. For the transversal modes the shift is approximately linear with strain. We also present analytical results from canonical calculations in the harmonic approximation showing that thermal expansion is uniform along the device. This prediction also works when the system operates in a nonlinear oscillation regime at moderate and high temperatures.Fil: Mancardo Viotti, Agustin Matias. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Monastra, Alejandro Gabriel. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Moreno, Mariano F.. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Carusela, María Florencia. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Assessment, improvement and comparison of different computational tools used for the simulation of heat transport in nanostructures
No full textIn this work we compare different implementations of two interatomic potential models, one empirical Tersoff-Brenner and another semi-empirical Tight-Binding, to be used in the thermal transport study of silicon nanosystems. The calculations are based on molecular dynamics simulations. In the case of Tersoff-Brenner potential, two free software packages were used, while for Tight-Binding potential, an in-house code was developed. Both approaches require an enormous amount of computing effort, so the use of acceleration tools for adequate performance is crucial. We present a detailed study of each computational tool used: efficiency, advantages and disadvantages, as well as results of application to the calculation of thermal conductance of structured silicon nanocrystals subjected to a temperature gradient.Fil: Bea, Edgar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; ArgentinaFil: Mancardo Viotti, Agustin Matias. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Carusela, María Florencia. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Monastra, Alejandro Gabriel. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Soba, Alejandro. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Thermal conductance of structured silicon nanocrystals
Full text linkWe calculate the thermal conductance of a structured silicon nanocrystal with a hole of different sizes. The numerical study is based on non-equilibrium molecular dynamics simulations using two potential models for the interatomic interactions: (i) an empirical Tersoff-Brenner (Tersoff) potential; (ii) a semi-empirical tight binding (TB) potential. TB potential model predicts a similar thermal conductance for the nanocrystal with no hole and with a small size hole, which contrasts with the monotonic decrease predicted by Tersoff potential model. In addition, thermal conductance decreasing is higher for TB potential model when the surface-to-volume ratio increases. This points out that to study thermal properties of nanostructures with high surface-to-volume ratio is mandatory the use of potential models with high transferability to take adequately into account the relevant quantum physical effects due to boundaries and surfaces.Fil: Bea, Edgar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; ArgentinaFil: Carusela, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Soba, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; ArgentinaFil: Monastra, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Mancardo Viotti, Agustin Matias. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentin
Inference of the force pattern acting on a semiflexible filament from shape analysis
No full textThe study of the active forces acting on semiflexible filaments networks such as the cytoskeleton requires noninvasive tools able to explore the deformation of single filaments in their natural environment. We propose here a practical method based on the solution of the hydrodynamic beam equation in the presence of transverse forces. We found that the derivative of the local curvature presents discontinuities that match the location of the applied forces, in contrast to the smooth curvature function obtained for the case of compressing longitudinal forces. These patterns can be easily appreciated in a kymograph of the curvature, which also reflects the temporal behavior of the forces. We assessed the method performance with numerical simulations describing the deformation of single microtubules provoked by the action of intracellular active forces.Fil: Wenger, Julieta. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Brigante, Azul María. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Fernández Casafuz, Agustina Belén. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Calculo. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Calculo; ArgentinaFil: Bruno, Luciana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Calculo. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Calculo; ArgentinaFil: Monastra, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentin
Thermal conductance of suspended nanoribbons: interplay between strain and interatomic potential nonlinearity
Full text linkWe investigate the role that nonlinearity in the interatomic potential has on the thermal conductance of a suspended nanoribbon when it is subjected to a longitudinal strain. To focus on the first cubic and quartic nonlinear terms of a general potential, we propose an atomic system based on an α–β Fermi–Pasta–Ulam nearest neighbor interaction. We perform classical molecular dynamics simulations to investigate the contribution of longitudinal, transversal and flexural modes to the thermal conductance as a function of the α–β parameters and the applied strain. We compare the cases where atoms are allowed to vibrate only in plane (2D) with the case of vibrations in and out of plane (3D). We find that the dependence of conductance on α and β relies on a crossover phenomenon between linear/nonlinear delocalized/localized flexural and transversal modes, driven by an on/off switch of the strain.Fil: Barreto, Roberto Antonio. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Carusela, María Florencia. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Monastra, Alejandro Gabriel. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
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