The Experts below are selected from a list of 1671 Experts worldwide ranked by ideXlab platform
Ishwar K. Puri - One of the best experts on this subject based on the ideXlab platform.
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Molecular simulations of thermal transport across interfaces: solid–vapour and solid–solid
Molecular Simulation, 2012Co-Authors: Sohail Murad, Ishwar K. PuriAbstract:Using molecular simulations, we have investigated heat transfer across the solid–fluid interface between water and silicon and silica wafers, and solid–solid interfaces in superlattices and thin solid films. The system set-up has allowed us to focus on the resistance associated with both the fluid and solid interfaces. For instance, by maintaining the solid phase at a constant temperature we can focus solely on the fluid-side resistance. Our results show that the thermal or Kapitza resistance at fluid side of the solid–fluid decreases significantly as the surface is made more hydrophilic. This is primarily due to increases in fluid adsorption and absorption at the surface, which enhance the Intermolecular Collision frequency at the interface. Increasing this frequency also reduces the dependence of thermal transport on variations in the interfacial temperature and pressure. Hence, decreasing the density diminishes the Intermolecular Collision frequency, which increases the thermal resistance. By maintaini...
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Molecular simulation of thermal transport across hydrophilic interfaces
Chemical Physics Letters, 2008Co-Authors: Sohail Murad, Ishwar K. PuriAbstract:Abstract Using molecular simulations, we have investigated heat transfer across the solid–fluid interface of a silica wafer in contact with water vapor. Our results show that the thermal or Kapitza resistance decreases significantly, as the surface becomes more hydrophilic. This is primarily due to increases in adsorption and absorption at the surface, which enhances the Intermolecular Collision frequency at the interface. Increasing this frequency also reduces the dependence of thermal transport on variations in the interfacial temperature and pressure. Decreasing the density diminishes the Intermolecular Collision frequency thus increasing the thermal resistance.
Sohail Murad - One of the best experts on this subject based on the ideXlab platform.
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Molecular simulations of thermal transport across interfaces: solid–vapour and solid–solid
Molecular Simulation, 2012Co-Authors: Sohail Murad, Ishwar K. PuriAbstract:Using molecular simulations, we have investigated heat transfer across the solid–fluid interface between water and silicon and silica wafers, and solid–solid interfaces in superlattices and thin solid films. The system set-up has allowed us to focus on the resistance associated with both the fluid and solid interfaces. For instance, by maintaining the solid phase at a constant temperature we can focus solely on the fluid-side resistance. Our results show that the thermal or Kapitza resistance at fluid side of the solid–fluid decreases significantly as the surface is made more hydrophilic. This is primarily due to increases in fluid adsorption and absorption at the surface, which enhance the Intermolecular Collision frequency at the interface. Increasing this frequency also reduces the dependence of thermal transport on variations in the interfacial temperature and pressure. Hence, decreasing the density diminishes the Intermolecular Collision frequency, which increases the thermal resistance. By maintaini...
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Molecular simulation of thermal transport across hydrophilic interfaces
Chemical Physics Letters, 2008Co-Authors: Sohail Murad, Ishwar K. PuriAbstract:Abstract Using molecular simulations, we have investigated heat transfer across the solid–fluid interface of a silica wafer in contact with water vapor. Our results show that the thermal or Kapitza resistance decreases significantly, as the surface becomes more hydrophilic. This is primarily due to increases in adsorption and absorption at the surface, which enhances the Intermolecular Collision frequency at the interface. Increasing this frequency also reduces the dependence of thermal transport on variations in the interfacial temperature and pressure. Decreasing the density diminishes the Intermolecular Collision frequency thus increasing the thermal resistance.
Denize Kalempa - One of the best experts on this subject based on the ideXlab platform.
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sound waves in gaseous mixtures induced by vibro thermal excitation at arbitrary rarefaction and sound frequency
Vacuum, 2019Co-Authors: Denize Kalempa, Felix Sharipov, Julio Conti SilvaAbstract:Abstract Sound waves due to vibro-thermal excitation propagating through a binary mixture of rarefied gases in a gap between source and receptor are investigated by applying the McCormack model to the Boltzmann equation. The sound waves are induced by mechanical vibration and temperature variation of one plate, while the other plate being fixed at a constant temperature, acts as a receptor of sound waves. The oscillatory gas mixture flow is considered as fully established and all its macroscopic quantities depend on time harmonically. The discrete velocity method is used to solve the coupled kinetic equations in wide ranges of both rarefaction and oscillation parameters. The former is defined as the ratio of the distance between the plates to the equivalent free path, while the latter is the ratio of the Intermolecular Collision frequency to sound frequency. Analytical solutions in the free molecular and hydrodynamic regimes have been obtained too. Two mixtures, namely, Helium Argon and Helium Xenon, are considered with a molar fraction equal to 0.1, 0.5 and 0.9. The amplitudes and phases of all macroscopic characteristics of the gas mixture flow are calculated as functions of the rarefaction and oscillation parameters so that the free molecular, transitional and hydrodynamic regimes are covered. The results are compared to those obtained in the limit of a single gas in order to investigate the influence of the molar fraction and molecular masses of species on the problem solution. The reciprocal relations between cross phenomena are obtained and verified numerically.
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gas flow near a plate oscillating longitudinally with an arbitrary frequency
Physics of Fluids, 2007Co-Authors: Felix Sharipov, Denize KalempaAbstract:A gas flow near a longitudinally oscillating plate is considered on the basis of the kinetic equation. It is assumed that the oscillation is fully established and the dependence of the solution on the time is harmonic, while its dependence on the spatial coordinate is obtained numerically. The main parameter determining the problem solution is the ratio of Intermolecular Collision frequency to the oscillation frequency. Moreover, the solution depends on the gas-surface interaction law. To take into account a nondiffuse scattering of particles on the surface the Cercignani-Lampis scattering kernel is applied in the boundary conditions. The numerical calculations were carried out for a wide range of the frequency ratio and for several values of the accommodation coefficients. Two numerical methods were employed to solve the kinetic equation: the integro-moment method and the discrete velocity one. The results obtained by both methods are in a good agreement with each other.
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Gas flow around a longitudinally oscillating plate at arbitrary ratio of Collision frequency to oscillation frequency
2007Co-Authors: Felix Sharipov, Denize KalempaAbstract:A gas flow around a longitudinally oscillating plate is considered on the basis of the kinetic equation. The main parameter determining the problem solution is the ratio of Intermolecular Collision frequency to the oscillation frequency. Two methods of computation were used: the integro-moment method and the discrete velocity one. Diffuse gas-surface interaction law was assumed. The numerical calculations were carried out for a wide range of the ratio of Collision frequency to oscillation frequency.
Robert R Gamache - One of the best experts on this subject based on the ideXlab platform.
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a pure h2o isolated line shape model based on classical molecular dynamics simulations of velocity changes and semi classical calculations of speed dependent Collisional parameters
Journal of Chemical Physics, 2012Co-Authors: N H Ngo, H Tran, Robert R GamacheAbstract:It is well known that the Voigt profile does not well describe the (measured) shapes of isolated lines. This is due to the neglect of the Intermolecular Collision-induced velocity changes and of the speed dependence of the Collisional parameters. In this paper, we present a new line profile model for pure H2O which takes both of these effects into account. The speed dependence of the Collisional parameters has been calculated by a semi-classical method. The velocity changes have been modeled by using the Keilson-Storer Collision kernel with two characteristic parameters. The latter have been deduced from classical molecular dynamics simulations which also indicate that, for pure H2O, the correlation between velocity-changing and state-changing Collisions is not negligible, a result confirmed by the analysis of measured spectra. A partially correlated speed-dependent Keilson-Storer model has thus been adopted to describe the line-shape. Comparisons between simulated spectra and measurements for four self-b...
Felix Sharipov - One of the best experts on this subject based on the ideXlab platform.
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sound waves in gaseous mixtures induced by vibro thermal excitation at arbitrary rarefaction and sound frequency
Vacuum, 2019Co-Authors: Denize Kalempa, Felix Sharipov, Julio Conti SilvaAbstract:Abstract Sound waves due to vibro-thermal excitation propagating through a binary mixture of rarefied gases in a gap between source and receptor are investigated by applying the McCormack model to the Boltzmann equation. The sound waves are induced by mechanical vibration and temperature variation of one plate, while the other plate being fixed at a constant temperature, acts as a receptor of sound waves. The oscillatory gas mixture flow is considered as fully established and all its macroscopic quantities depend on time harmonically. The discrete velocity method is used to solve the coupled kinetic equations in wide ranges of both rarefaction and oscillation parameters. The former is defined as the ratio of the distance between the plates to the equivalent free path, while the latter is the ratio of the Intermolecular Collision frequency to sound frequency. Analytical solutions in the free molecular and hydrodynamic regimes have been obtained too. Two mixtures, namely, Helium Argon and Helium Xenon, are considered with a molar fraction equal to 0.1, 0.5 and 0.9. The amplitudes and phases of all macroscopic characteristics of the gas mixture flow are calculated as functions of the rarefaction and oscillation parameters so that the free molecular, transitional and hydrodynamic regimes are covered. The results are compared to those obtained in the limit of a single gas in order to investigate the influence of the molar fraction and molecular masses of species on the problem solution. The reciprocal relations between cross phenomena are obtained and verified numerically.
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gas flow near a plate oscillating longitudinally with an arbitrary frequency
Physics of Fluids, 2007Co-Authors: Felix Sharipov, Denize KalempaAbstract:A gas flow near a longitudinally oscillating plate is considered on the basis of the kinetic equation. It is assumed that the oscillation is fully established and the dependence of the solution on the time is harmonic, while its dependence on the spatial coordinate is obtained numerically. The main parameter determining the problem solution is the ratio of Intermolecular Collision frequency to the oscillation frequency. Moreover, the solution depends on the gas-surface interaction law. To take into account a nondiffuse scattering of particles on the surface the Cercignani-Lampis scattering kernel is applied in the boundary conditions. The numerical calculations were carried out for a wide range of the frequency ratio and for several values of the accommodation coefficients. Two numerical methods were employed to solve the kinetic equation: the integro-moment method and the discrete velocity one. The results obtained by both methods are in a good agreement with each other.
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Gas flow around a longitudinally oscillating plate at arbitrary ratio of Collision frequency to oscillation frequency
2007Co-Authors: Felix Sharipov, Denize KalempaAbstract:A gas flow around a longitudinally oscillating plate is considered on the basis of the kinetic equation. The main parameter determining the problem solution is the ratio of Intermolecular Collision frequency to the oscillation frequency. Two methods of computation were used: the integro-moment method and the discrete velocity one. Diffuse gas-surface interaction law was assumed. The numerical calculations were carried out for a wide range of the ratio of Collision frequency to oscillation frequency.