Papers by Mariano López deHaro
Physics of Fluids A: Fluid Dynamics, 1993
The P urpose of this Brief Communications section is to present important research results of mor... more The P urpose of this Brief Communications section is to present important research results of more limited scope than regular artic es appearing in Physics of Fluids A. Submission of material of a peripheral or cursory nature is strongly discouraged. Brief Communications cannot exceed three printed pages in length, including space allowed for title, Jigures, tables, references, and an abstract litnited to about 100 words.
Physics of Fluids A: Fluid Dynamics, 1992
The kinetic models proposed by Garz6 et al. [ Phys. Fluids A 1,380 (1989) ] and Gross and Krook [... more The kinetic models proposed by Garz6 et al. [ Phys. Fluids A 1,380 (1989) ] and Gross and Krook [ Phys. Rev. 102,593 (1956) ] are used to study diffusion in uniform shear flow. The kinetic equations are solved by means of a generalized Chapman-Enskog expansion for Maxwell molecules. The main peculiarity of the method is that the successive approximations to the velocity distribution functions retain all orders in the shear rate. Two cases are considered, namely the self-diffusion and the tracer diffusion in a system under shear flow. The relevant transport properties and the distribution functions are explicitly obtained. A comparison with previous results derived from the Boltzmann equation and between both models is carried out.
Revista Mexicana de Fisica
The postulates and methodology bf the version of extended irreversible thermodynamics developed i... more The postulates and methodology bf the version of extended irreversible thermodynamics developed in Mexico are presented. Mention is made of the main features which make it dilferent from other existing versions. The ionized gas modeled as a binary mixture is discussed to illustrate the approach. Sorne limitations and perspectives are also pointed out. RESUMEN. Se presentan los postulados y la metodología de la versión de la Termodinámica Irreversible Extendida desarrollada en México. Se hace mención de las principales características que la hacen diferente de otras versiones. Para ilustrar el enfoque se discute brevemente el 0050 de un gas ionizado modelado como una mezcla binaria. Finalmente, se señalan las limitaciones y perspectivas de esta versión. PACS: 05.70.Ln; 47.65.+a; 51.50.+v
Physical Review A, 1985
The thermodynamic implications of the first deviations with respect to the classical hydrodynamic... more The thermodynamic implications of the first deviations with respect to the classical hydrodynamic behavior in high-frequency, short-wavelength phenomena are examined. The constitutive equations arising from an extended irreversible-thermodynamic formalism taking into account spatial inhomogeneities in the space of state variables are compared with those used in generalized hydrodynamics. The so-called exponential model for the memory function of the transverse-velocity correlation function is derived under the assumptions of extended irreversible thermodynamics only. Furthermore, it is also shown how more complicated memory functions can be derived. The results are carefully analyzed and compared with some microscopic derivations.
Festschrift in Honor of Leopoldo García-Colín's 80th Birthday, 2010
ABSTRACT The problem of a zero-mean oscillatory flow of a Newtonian fluid between infinite parall... more ABSTRACT The problem of a zero-mean oscillatory flow of a Newtonian fluid between infinite parallel plates with thermal boundary conditions of the third kind is considered. With the analytic solutions for the velocity and temperature fields at hand, the local and global time-averaged entropy production are computed. The consequences of having different convective heat transfer coefficients in each plate are assessed for this problem and some conditions that lead to entropy generation minimization are determined.
The Journal of chemical physics, Jan 7, 2015
The problem of demixing in the Asakura-Oosawa colloid-polymer model is considered. The critical c... more The problem of demixing in the Asakura-Oosawa colloid-polymer model is considered. The critical constants are computed using truncated virial expansions up to fifth order. While the exact analytical results for the second and third virial coefficients are known for any size ratio, analytical results for the fourth virial coefficient are provided here, and fifth virial coefficients are obtained numerically for particular size ratios using standard Monte Carlo techniques. We have computed the critical constants by successively considering the truncated virial series up to the second, third, fourth, and fifth virial coefficients. The results for the critical colloid and (reservoir) polymer packing fractions are compared with those that follow from available Monte Carlo simulations in the grand canonical ensemble. Limitations and perspectives of this approach are pointed out.
Physics of Fluids, 1995
ABSTRACT Tracer diffusion in a steady shear flow state is analyzed. A kinetic model incorporating... more ABSTRACT Tracer diffusion in a steady shear flow state is analyzed. A kinetic model incorporating a temperature dependence in the collision frequencies is used. This allows for the consideration of a general repulsive intermolecular interaction. A perturbative scheme is applied to get the shear rate dependence of the tracer diffusion tensor in terms of the mass ratio, the force constants ratio, and a parameter characterizing the interaction potential considered. In addition, the heat flux arising from the concentration gradient of the tracer species is also evaluated. The results are illustrated for the two extreme cases of Maxwell molecules and hard spheres.
Physics of Fluids, 1997
Transport properties of a dilute gas subjected to arbitrarily large velocity and temperature grad... more Transport properties of a dilute gas subjected to arbitrarily large velocity and temperature gradients (steady planar Couette flow) are determined. The results are obtained from the so-called ellipsoidal statistical (ES) kinetic model, which is an extension of the well-known BGK kinetic model to account for the correct Prandtl number. At a hydrodynamic level, the solution is characterized by constant pressure, and linear velocity and parabolic temperature profiles with respect to a scaled variable. The transport coefficients are explicitly evaluated as nonlinear functions of the shear rate. A comparison with previous results derived from a perturbative solution of the Boltzmann equation as well as from other kinetic models is carried out. Such a comparison shows that the ES predictions are in better agreement with the Boltzmann results than those of the other approximations. In addition, the velocity distribution function is also computed. Although the shear rates required for observing non-Newtonian effects are experimentally unrealizable, the conclusions obtained here may be relevant for analyzing computer results.
Physics of Fluids, 1994
Expressions for the heat and momentum transport are obtained for a dilute gas in a steady state w... more Expressions for the heat and momentum transport are obtained for a dilute gas in a steady state with both temperature and velocity gradients. The results are derived from a kinetic model recently proposed: the Liu model [Phys. Fluids A 2, 277 (1990)]. This model improves the well-known Bhatnagar–Gross–Krook (BGK) model equation. At a hydrodynamic level, the solution is characterized by a constant pressure, a linear profile of the flow velocity with respect to a space variable scaled with the local collision frequency, and a parabolic profile of the temperature with respect to the same variable. The shear viscosity and thermal conductivity coefficients are explicitly obtained. They are nonlinear functions of the shear rate and their only dependence on the temperature gradient is through their zero shear-rate values. In addition, the shear-rate dependence of the viscometric functions is also analyzed. A comparison with previous results derived from the BGK equation is carried out.
Physics of Fluids, 2000
Mass and heat transport in a dilute binary mixture of Maxwell molecules under steady shear flow a... more Mass and heat transport in a dilute binary mixture of Maxwell molecules under steady shear flow are studied in the limit of small concentration gradients. The analysis is made from the Gross-Krook kinetic model of the Boltzmann equation. This model is solved by means of a perturbation solution around the steady shear flow solution ͓Phys. Fluids 8, 2756 ͑1996͔͒, which applies for arbitrary values of the shear rate. In the first order of the expansion the results show that the mass and heat fluxes are proportional to the concentration gradient but, due to the anisotropy of the problem, mutual diffusion and Dufour tensors can be identified, respectively. Both tensors are explicitly determined in terms of the shear rate and the parameters of the mixture ͑particle masses, concentrations, and force constants͒. A comparison with the results derived from the exact Boltzmann equation at the level of the diffusion tensor shows a good agreement for a wide range of values of the shear rate.
Physical Review E, 2014
A recent proposal in which the equation of state of a polydisperse hard-sphere mixture is mapped ... more A recent proposal in which the equation of state of a polydisperse hard-sphere mixture is mapped onto that of the one-component fluid is extrapolated beyond the freezing point to estimate the jamming packing fraction φJ of the polydisperse system as a simple function of M1M3/M 2 2 , where M k is the kth moment of the size distribution. An analysis of experimental and simulation data of φJ for a large number of different mixtures shows a remarkable general agreement with the theoretical estimate. To give extra support to the procedure, simulation data for seventeen mixtures in the highdensity region are used to infer the equation of state of the pure hard-sphere system in the metastable region. An excellent collapse of the inferred curves up to the glass transition and a significant narrowing of the different out-of-equilibrium glass branches all the way to jamming are observed. Thus, the present approach provides an extremely simple criterion to unify in a common framework and to give coherence to data coming from very different polydisperse hard-sphere mixtures.
Physica A: Statistical Mechanics and its Applications, 1986
ABSTRACT A study is performed on the time correlation function for the equilibrium fluctuations o... more ABSTRACT A study is performed on the time correlation function for the equilibrium fluctuations of the longitudinal velocity in a compressible, heat insulating fluid, within the context of extended irreversible thermodynamics. The memory function is explicitly computed and shown to obey a double exponential decay. Also at El Colegio Nacional and Physics Department of UAM-Iztapalapa.
Physica A: Statistical Mechanics and its Applications, 2006
Using the liquid state thermodynamic perturbation theory and the hard-sphere fluid as the referen... more Using the liquid state thermodynamic perturbation theory and the hard-sphere fluid as the reference system, the liquid-glass transition line of Lennard-Jones and hard-core Yukawa fluids is computed. The results are presented both in the reduced density vs. reduced temperature and in the reduced pressure vs. reduced temperature planes. A comparison with available simulation data and a discussion of the merits and limitations of this approach are also provided.
Molecular Physics, 2007
ABSTRACT Two analytic approximations for the direct correlation function of a hard-sphere fluid a... more ABSTRACT Two analytic approximations for the direct correlation function of a hard-sphere fluid are considered. The first follows from a generalization of the Percus-Yevick result in d dimensions, whereas the second arises in the Rational Function Approximation (RFA) method. Both approximations require the equation of state of the hard-sphere fluid as input. The results, derived after use of the Carnahan-Starling and the Padé 4,3 equations of state in both approaches, are compared with simulation data. The comparison shows that the first approximation is rather accurate in the region inside the core, but inherits the limitation of the Percus-Yevick theory for distances beyond the hard-sphere diameter. On the other hand, the results of the RFA method are also accurate inside the core and capture well the initial part of the tail beyond the hard-sphere diameter, but fail to account for the subsequent oscillations observed in the simulations. Other merits and limitations of the two approaches are reported.
Journal of Physics D: Applied Physics, 1999
The consequences for magnetic transport of a generalized Ohm's law that includes the inertia ... more The consequences for magnetic transport of a generalized Ohm's law that includes the inertia of electrons are explored. For metals, this law coincides with the Drude model for electronic conduction. A formula for the absorption coefficient in a rigid conductor is ...
The Journal of Chemical Physics, 1985
The equilibrium concentration autocorrelation function for an inert binary mixture is calculated ... more The equilibrium concentration autocorrelation function for an inert binary mixture is calculated by means of extended irreversible thermodynamics. The ensuing generalized transport coefficient is explicitly evaluated and the corresponding k-dependent relaxation time is also obtained. The connection with neutron scattering experiments is suggested and expressions for the dynamic structure factor and the half-width dispersion relation are given.
The Journal of Chemical Physics, 1998
The Journal of Chemical Physics, 2013
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Papers by Mariano López deHaro