The aim of this paper is to present a model for the rheological behavior of simple liquids as a f... more The aim of this paper is to present a model for the rheological behavior of simple liquids as a function of the amplitude of the imposed shear stress or strain. The elastic mode theory is first generalized to take into account the fact that, during a flow experiment, mechanical energy is injected in a system initially at thermodynamic equilibrium. This generalized theory can be seen as a particular aspect of the general problem of perturbation by the measurement, associated with that of the coupling between fluctuation and dissipation. This generalization leads to a “finitary” character of the model. It is then combined with the inertial mode theory. The formalism thus obtained allows us to model the rheological behavior of liquids over a wide range of velocity gradients, including the intermediate narrow range corresponding to the Newtonian regime. As experimental tests, viscosity measurements with two kinds of moving rotor rheometers were performed. Only data obtained with liquid ...
Electron mobility in superfluid helium is modeled between 0.1 and 2.2 K by a van der Waals-type t... more Electron mobility in superfluid helium is modeled between 0.1 and 2.2 K by a van der Waals-type thermodynamic equation of state, which relates the free volume of solvated electrons to temperature, density, and phase dependent internal pressure.
Today, a large number of industrial processes involve the liquid state, very often at high pressu... more Today, a large number of industrial processes involve the liquid state, very often at high pressures. Among these, we can mention: (a) chemical preparations at high pressures; (b) determination of the efficiency and response time of servomechanisms (e.g. hydraulic press); (c) flows in porous rocks; (d) water hammer in pipelines; (e) evolution of viscosity as a function of pressure in lubrication processes
All these processes require a precise knowledge of the equation of state of liquids and consequently an experimental determination of the pressure isotherms; these can be deduced from the variation of volume with pressure. But when one wants to study the compressibility of fluids, one generally comes up against two major problems: on the one hand, the realization and the implementation of a measuring cell that resists the pressure that one wishes to apply, and on the other hand, the measurement of the pressure that one applies. It is the history of this evolution that we are going to present, by reproducing as often as possible the writings of the scientists who participated in it.
Positively charged helium clusters, also called ‘snowballs’, have been investigated within normal... more Positively charged helium clusters, also called ‘snowballs’, have been investigated within normal liquid helium.
The Orsay-Trento bosonic density functional theory model is extended to include dissipation due t... more The Orsay-Trento bosonic density functional theory model is extended to include dissipation due to the viscous response of superfluid (4)He present at finite temperatures. The viscous functional is derived from the Navier-Stokes equation by using the Madelung transformation and includes the contribution of interfacial viscous response present at the gas-liquid boundaries. This contribution was obtained by calibrating the model against the experimentally determined electron mobilities from 1.2 K to 2.1 K along the saturated vapor pressure line, where the viscous response is dominated by thermal rotons. The temperature dependence of ion mobility was calculated for several different solvation cavity sizes and the data are rationalized in the context of roton scattering and Stokes limited mobility models. Results are compared to the experimentally observed "exotic ion" data, which provides estimates for the corresponding bubble sizes in the liquid. Possible sources of such ion...
The journal of physical chemistry letters, Jan 17, 2016
Evidence for helium excimers (He2(*)) in the lowest allowed rotational quantum state in liquid he... more Evidence for helium excimers (He2(*)) in the lowest allowed rotational quantum state in liquid helium is presented. He2(*) was generated by a corona discharge in the gas and normal liquid phases. Fluorescence spectra recorded in the visible region between 3.8 and 5.0 K and 0.2 and 5.6 bar showed the rotationally resolved d(3)Σu(+) → b(3)Πg transition of He2(*). Analysis of the pressure and temperature dependence of lineshifts and line intensities showed features of solvated He2(*) superimposed on its gas-phase spectrum and, in the liquid phase only, pressure-induced rotational cooling. These findings suggest that He2(*) can be used to investigate bulk helium in different phases at the nanoscale.
IEEE Transactions on Dielectrics and Electrical Insulation, 2020
We report data of the O2− ion mobility in neon gas over broad density and temperature ranges alon... more We report data of the O2− ion mobility in neon gas over broad density and temperature ranges along with its theoretical description in terms of the thermodynamic, free volume model that has successfully been adopted for the interpretation of electron and ion mobility in superfluid and normal helium. The free volume model, which is aimed at computing the free volume accessible for the ion motion, along with the Millikan-Cunningham slip factor correction, is able to describe the ion mobility in the crossover region connecting the dilute gas regime described by the classical kinetic theory to the high density region ruled by the laws of hydrodynamic transport.
A new equation of state for argon has been developed in view to extend the range of validity of t... more A new equation of state for argon has been developed in view to extend the range of validity of the equation of state previously proposed by Tegeler et al. (1999) and to obtain a better physical description of the experimental thermodynamic data for the whole fluid region (single-phase and coexistence states). As proposed by Tegeler et al., this equation is also based on a functional form of the residual part of the reduced Helmholtz free energy. However in this work, the fundamental equation for the Helmholtz free energy has been derived from the measured quantities CV(rho,T) and P(rho,T). The empirical description of the isochoric heat capacity CV is based on an original empirical description containing explicitly the metastable states. The new formulation is valid for the whole fluid region from the melting line to 2300 K and for pressures up to 50 000 MPa. It also predicts existence of a maximum of the isochoric heat capacity CV along isochors as experimentally observed in sever...
New Molecular Dynamics simulations have been carried out in order to get an insight on the physic... more New Molecular Dynamics simulations have been carried out in order to get an insight on the physical mechanisms that determine the drift mobility of negative Oxygen ions in very dense Neon gas in the supercritical phase close to the critical point. Two ion-neutral interaction potentials have been used that differ by their repulsive part. We have observed that the potential with a harder repulsive part gives much better agreement with the experimental data. The differences with the softer repulsive potential previously used are discussed. We propose that the behavior of the ion mobility as a function of the gas density is related to the number of neutral atoms loosely bound in the first solvation shell around the ion.
The aim of this paper is to present a model for the rheological behavior of simple liquids as a f... more The aim of this paper is to present a model for the rheological behavior of simple liquids as a function of the amplitude of the imposed shear stress or strain. The elastic mode theory is first generalized to take into account the fact that, during a flow experiment, mechanical energy is injected in a system initially at thermodynamic equilibrium. This generalized theory can be seen as a particular aspect of the general problem of perturbation by the measurement, associated with that of the coupling between fluctuation and dissipation. This generalization leads to a “finitary” character of the model. It is then combined with the inertial mode theory. The formalism thus obtained allows us to model the rheological behavior of liquids over a wide range of velocity gradients, including the intermediate narrow range corresponding to the Newtonian regime. As experimental tests, viscosity measurements with two kinds of moving rotor rheometers were performed. Only data obtained with liquid ...
Electron mobility in superfluid helium is modeled between 0.1 and 2.2 K by a van der Waals-type t... more Electron mobility in superfluid helium is modeled between 0.1 and 2.2 K by a van der Waals-type thermodynamic equation of state, which relates the free volume of solvated electrons to temperature, density, and phase dependent internal pressure.
Today, a large number of industrial processes involve the liquid state, very often at high pressu... more Today, a large number of industrial processes involve the liquid state, very often at high pressures. Among these, we can mention: (a) chemical preparations at high pressures; (b) determination of the efficiency and response time of servomechanisms (e.g. hydraulic press); (c) flows in porous rocks; (d) water hammer in pipelines; (e) evolution of viscosity as a function of pressure in lubrication processes
All these processes require a precise knowledge of the equation of state of liquids and consequently an experimental determination of the pressure isotherms; these can be deduced from the variation of volume with pressure. But when one wants to study the compressibility of fluids, one generally comes up against two major problems: on the one hand, the realization and the implementation of a measuring cell that resists the pressure that one wishes to apply, and on the other hand, the measurement of the pressure that one applies. It is the history of this evolution that we are going to present, by reproducing as often as possible the writings of the scientists who participated in it.
Positively charged helium clusters, also called ‘snowballs’, have been investigated within normal... more Positively charged helium clusters, also called ‘snowballs’, have been investigated within normal liquid helium.
The Orsay-Trento bosonic density functional theory model is extended to include dissipation due t... more The Orsay-Trento bosonic density functional theory model is extended to include dissipation due to the viscous response of superfluid (4)He present at finite temperatures. The viscous functional is derived from the Navier-Stokes equation by using the Madelung transformation and includes the contribution of interfacial viscous response present at the gas-liquid boundaries. This contribution was obtained by calibrating the model against the experimentally determined electron mobilities from 1.2 K to 2.1 K along the saturated vapor pressure line, where the viscous response is dominated by thermal rotons. The temperature dependence of ion mobility was calculated for several different solvation cavity sizes and the data are rationalized in the context of roton scattering and Stokes limited mobility models. Results are compared to the experimentally observed "exotic ion" data, which provides estimates for the corresponding bubble sizes in the liquid. Possible sources of such ion...
The journal of physical chemistry letters, Jan 17, 2016
Evidence for helium excimers (He2(*)) in the lowest allowed rotational quantum state in liquid he... more Evidence for helium excimers (He2(*)) in the lowest allowed rotational quantum state in liquid helium is presented. He2(*) was generated by a corona discharge in the gas and normal liquid phases. Fluorescence spectra recorded in the visible region between 3.8 and 5.0 K and 0.2 and 5.6 bar showed the rotationally resolved d(3)Σu(+) → b(3)Πg transition of He2(*). Analysis of the pressure and temperature dependence of lineshifts and line intensities showed features of solvated He2(*) superimposed on its gas-phase spectrum and, in the liquid phase only, pressure-induced rotational cooling. These findings suggest that He2(*) can be used to investigate bulk helium in different phases at the nanoscale.
IEEE Transactions on Dielectrics and Electrical Insulation, 2020
We report data of the O2− ion mobility in neon gas over broad density and temperature ranges alon... more We report data of the O2− ion mobility in neon gas over broad density and temperature ranges along with its theoretical description in terms of the thermodynamic, free volume model that has successfully been adopted for the interpretation of electron and ion mobility in superfluid and normal helium. The free volume model, which is aimed at computing the free volume accessible for the ion motion, along with the Millikan-Cunningham slip factor correction, is able to describe the ion mobility in the crossover region connecting the dilute gas regime described by the classical kinetic theory to the high density region ruled by the laws of hydrodynamic transport.
A new equation of state for argon has been developed in view to extend the range of validity of t... more A new equation of state for argon has been developed in view to extend the range of validity of the equation of state previously proposed by Tegeler et al. (1999) and to obtain a better physical description of the experimental thermodynamic data for the whole fluid region (single-phase and coexistence states). As proposed by Tegeler et al., this equation is also based on a functional form of the residual part of the reduced Helmholtz free energy. However in this work, the fundamental equation for the Helmholtz free energy has been derived from the measured quantities CV(rho,T) and P(rho,T). The empirical description of the isochoric heat capacity CV is based on an original empirical description containing explicitly the metastable states. The new formulation is valid for the whole fluid region from the melting line to 2300 K and for pressures up to 50 000 MPa. It also predicts existence of a maximum of the isochoric heat capacity CV along isochors as experimentally observed in sever...
New Molecular Dynamics simulations have been carried out in order to get an insight on the physic... more New Molecular Dynamics simulations have been carried out in order to get an insight on the physical mechanisms that determine the drift mobility of negative Oxygen ions in very dense Neon gas in the supercritical phase close to the critical point. Two ion-neutral interaction potentials have been used that differ by their repulsive part. We have observed that the potential with a harder repulsive part gives much better agreement with the experimental data. The differences with the softer repulsive potential previously used are discussed. We propose that the behavior of the ion mobility as a function of the gas density is related to the number of neutral atoms loosely bound in the first solvation shell around the ion.
Uploads
Papers by F Aitken
All these processes require a precise knowledge of the equation of state of liquids and consequently an experimental determination of the pressure isotherms; these can be deduced from the variation of volume with pressure. But when one wants to study the compressibility of fluids, one generally comes up against two major problems: on the one hand, the realization and the implementation of a measuring cell that resists the pressure that one wishes to apply, and on the other hand, the measurement of the pressure that one applies. It is the history of this evolution that we are going to present, by reproducing as often as possible the writings of the scientists who participated in it.
All these processes require a precise knowledge of the equation of state of liquids and consequently an experimental determination of the pressure isotherms; these can be deduced from the variation of volume with pressure. But when one wants to study the compressibility of fluids, one generally comes up against two major problems: on the one hand, the realization and the implementation of a measuring cell that resists the pressure that one wishes to apply, and on the other hand, the measurement of the pressure that one applies. It is the history of this evolution that we are going to present, by reproducing as often as possible the writings of the scientists who participated in it.