Persona: Español Garrigos, José
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Español Garrigos
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Publicación Microscopic Slip Boundary Conditions in Unsteady Fluid Flows(American Physical Society, 2019-12-31) Torre, J. A. de la; Duque Zumajo, Diego; Camargo-Trillos, Diego; Español Garrigos, JoséAn algebraic tail in the Green-Kubo integral for the solid-fluid friction coefficient hampers its use in the determination of the slip length. A simple theory for discrete nonlocal hydrodynamics near parallel solid walls with extended friction forces is given. We explain the origin of the algebraic tail and give a solution of the plateau problem in the Green-Kubo expressions. We derive the slip boundary condition with a microscopic expression for the slip length and the hydrodynamic wall position, and assess it through simulations of an unsteady plug flow.Publicación Statistical mechanics of the GENERIC framework under external forcing(American Institute of Physics, 2023-07-10) Español Garrigos, JoséThe General Equation for Non-Equilibrium Reversible Irreversible Coupling (GENERIC) framework provides a thermodynamically consistent approach to describe the evolution of coarse-grained variables. This ramework states that Markovian dynamic equations governing the evolution of coarse-grained variables have a universal structure that ensures energy conservation (first law) and entropy increase (second law). However, the presence of external time-dependent forces can break the energy conservation law, requiring modifications to the framework’s structure. To address this issue, we start from a rigorous and exact transport equation for the average of a set of coarse-grained variables derived from a projection operator technique in the presence of external forces. Under the Markovian approximation, this approach provides the statistical mechanics underpinning of the GENERIC framework under external forcing conditions. By doing so, we can account for the effects of external forcing on the system’s evolution while ensuring thermodynamic consistency.Publicación Solution to the plateau problem in the Green-Kubo formula(American Physical Society, 2019-02-19) Torre, J. A. de la; Duque Zumajo, Diego; Español Garrigos, JoséTransport coefficients appearing in Markovian dynamic equations for coarse-grained variables have microscopic expressions given by Green-Kubo formulas. These formulas may suffer from the well-known plateau problem. The problem arises because the Green-Kubo running integrals decay as the correlation of the coarse-grained variables themselves. The usual solution is to resort to an extreme timescale separation, for which the plateau problem is minor. Within the context of Mori projection operator formulation, we offer an alternative expression for the transport coefficients that is given by a corrected Green-Kubo expression that has no plateau problem by construction. The only assumption is that the Markovian approximation is valid in such a way that transport coefficients can be defined, even in the case that the separation of timescales is not extreme.Publicación Microscopic Slip Boundary Conditions in Unsteady Fluid Flows(American Physical Society, 2019-12-31) Torre, J. A. de la; Duque Zumajo, Diego; Camargo-Trillos, Diego; Español Garrigos, JoséAn algebraic tail in the Green-Kubo integral for the solid-fluid friction coefficient hampers its use in the determination of the slip length. A simple theory for discrete nonlocal hydrodynamics near parallel solid walls with extended friction forces is given. We explain the origin of the algebraic tail and give a solution of the plateau problem in the Green-Kubo expressions. We derive the slip boundary condition with a microscopic expression for the slip length and the hydrodynamic wall position, and assess it through simulations of an unsteady plug flow.Publicación Boundary conditions derived from a microscopic theory of hydrodynamics near solids(American Institute of Physics, 2019-04-08) Camargo-Trillos, Diego; Torre, J. A. de la; Delgado Buscalioni, Rafael; Chejne, Farid; Español Garrigos, JoséThe theory of nonlocal isothermal hydrodynamics near a solid object derived microscopically in the study by Camargo et al. [J. Chem. Phys. 148, 064107 (2018)] is considered under the conditions that the flow fields are of macroscopic character. We show that in the limit of macroscopic flows, a simple pillbox argument implies that the reversible and irreversible forces that the solid exerts on the fluid can be represented in terms of boundary conditions. In this way, boundary conditions are derived from the underlying microscopic dynamics of the fluid-solid system. These boundary conditions are the impenetrability condition and the Navier slip boundary condition. The Green-Kubo transport coefficients associated with the irreversible forces that the solid exert on the fluid appear naturally in the slip length. The microscopic expression for the slip length thus obtained is shown to coincide with the one provided originally by Bocquet and Barrat [Phys. Rev. E 49, 3079 (1994)].Publicación Solution to the plateau problem in the Green-Kubo formula(American Physical Society, 2019-02-19) Torre, J. A. de la; Duque Zumajo, Diego; Español Garrigos, JoséTransport coefficients appearing in Markovian dynamic equations for coarse-grained variables have microscopic expressions given by Green-Kubo formulas. These formulas may suffer from the well-known plateau problem. The problem arises because the Green-Kubo running integrals decay as the correlation of the coarse-grained variables themselves. The usual solution is to resort to an extreme timescale separation, for which the plateau problem is minor. Within the context of Mori projection operator formulation, we offer an alternative expression for the transport coefficients that is given by a corrected Green-Kubo expression that has no plateau problem by construction. The only assumption is that the Markovian approximation is valid in such a way that transport coefficients can be defined, even in the case that the separation of timescales is not extreme.Publicación Statistical mechanics of the GENERIC framework under external forcing(American Institute of Physics, 2023-07-10) Español Garrigos, JoséThe General Equation for Non-Equilibrium Reversible Irreversible Coupling (GENERIC) framework provides a thermodynamically consistent approach to describe the evolution of coarse-grained variables. This ramework states that Markovian dynamic equations governing the evolution of coarse-grained variables have a universal structure that ensures energy conservation (first law) and entropy increase (second law). However, the presence of external time-dependent forces can break the energy conservation law, requiring modifications to the framework’s structure. To address this issue, we start from a rigorous and exact transport equation for the average of a set of coarse-grained variables derived from a projection operator technique in the presence of external forces. Under the Markovian approximation, this approach provides the statistical mechanics underpinning of the GENERIC framework under external forcing conditions. By doing so, we can account for the effects of external forcing on the system’s evolution while ensuring thermodynamic consistency.Publicación Boundary conditions derived from a microscopic theory of hydrodynamics near solids(American Institute of Physics, 2019-04-08) Camargo-Trillos, Diego; Torre, J. A. de la; Delgado Buscalioni, Rafael; Chejne, Farid; Español Garrigos, JoséThe theory of nonlocal isothermal hydrodynamics near a solid object derived microscopically in the study by Camargo et al. [J. Chem. Phys. 148, 064107 (2018)] is considered under the conditions that the flow fields are of macroscopic character. We show that in the limit of macroscopic flows, a simple pillbox argument implies that the reversible and irreversible forces that the solid exerts on the fluid can be represented in terms of boundary conditions. In this way, boundary conditions are derived from the underlying microscopic dynamics of the fluid-solid system. These boundary conditions are the impenetrability condition and the Navier slip boundary condition. The Green-Kubo transport coefficients associated with the irreversible forces that the solid exert on the fluid appear naturally in the slip length. The microscopic expression for the slip length thus obtained is shown to coincide with the one provided originally by Bocquet and Barrat [Phys. Rev. E 49, 3079 (1994)].