Open Access. Powered by Scholars. Published by Universities.®

Transport Phenomena Commons

Open Access. Powered by Scholars. Published by Universities.®

Mechanical Engineering

Institution
Keyword
Publication Year
Publication
Publication Type

Articles 61 - 81 of 81

Full-Text Articles in Transport Phenomena

Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev Jan 2010

Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev

Mathematics Faculty Publications

We study long-wave Marangoni convection in a layer heated from below. Using the scaling k=O Bi, where k is the wave number and Bi is the Biot number, we derive a set of amplitude equations. Analysis of this set shows presence of monotonic and oscillatory modes of instability. Oscillatory mode has not been previously found for such direction of heating. Studies of weakly nonlinear dynamics demonstrate that stable steady and oscillatory patterns can be found near the stability threshold.


Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev Jan 2010

Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev

Mathematics Faculty Publications

We study long-wave Marangoni convection in a layer heated from below. Using the scaling k=O Bi, where k is the wave number and Bi is the Biot number, we derive a set of amplitude equations. Analysis of this set shows presence of monotonic and oscillatory modes of instability. Oscillatory mode has not been previously found for such direction of heating. Studies of weakly nonlinear dynamics demonstrate that stable steady and oscillatory patterns can be found near the stability threshold.


Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …


Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …


Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …


Thermodynamically Coupled Heat And Mass Flows In A Reaction-Transport System With External Resistances, Yaşar Demirel Mar 2009

Thermodynamically Coupled Heat And Mass Flows In A Reaction-Transport System With External Resistances, Yaşar Demirel

Yaşar Demirel Publications

Considerable work has been published on mathematically coupled nonlinear differential equations by neglecting thermodynamic coupling between heat and mass flows in reaction-transport systems. The thermodynamic coupling refers that a flow occurs without or against its primary thermodynamic driving force, which may be a gradient of temperature, or chemical potential, or reaction affinity. This study presents the modeling of thermodynamically coupled heat and mass flows of two components in a reaction-transport system with external heat and mass transfer resistances. The modeling equations are based on the linear nonequilibrium thermodynamics approach by assuming that the system is in the vicinity of global …


Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Agegnehu Atena, Mikhail Khenner Jan 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Agegnehu Atena, Mikhail Khenner

Mathematics Faculty Publications

In this paper the lubrication-type dynamical model is developed of a molten, pulsed laser-irradiated metallic film. The heat transfer problem that incorporates the absorbed heat from a single beam or interfering beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the peak laser beam intensity, the film optical thickness, the Biot and …


Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Agegnehu Atena, Mikhail Khenner Jan 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Agegnehu Atena, Mikhail Khenner

Mathematics Faculty Publications

In this paper the lubrication-type dynamical model is developed of a molten, pulsed laser-irradiated metallic film. The heat transfer problem that incorporates the absorbed heat from a single beam or interfering beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the peak laser beam intensity, the film optical thickness, the Biot and …


Modeling Of Thermodynamically Coupled Reaction-Transport Systems, Yaşar Demirel May 2008

Modeling Of Thermodynamically Coupled Reaction-Transport Systems, Yaşar Demirel

Yaşar Demirel Publications

Nonisothermal reaction-diffusion systems control the behavior of many transport and rate processes in physical, chemical and biological systems, such as pattern formation and chemical pumps. Considerable work has been published on mathematically coupled nonlinear differential equations by neglecting thermodynamic coupling between a chemical reaction and transport processes of mass and heat. This study presents the modeling of thermodynamically coupled system of a simple elementary chemical reaction with molecular heat and mass transport. The thermodynamic coupling refers that a flow occurs without or against its primary thermodynamic driving force, which may be a gradient of temperature or chemical potential or reaction …


Morphologies And Kinetics Of A Dewetting Ultrathin Solid Film, Mikhail Khenner Jan 2008

Morphologies And Kinetics Of A Dewetting Ultrathin Solid Film, Mikhail Khenner

Mathematics Faculty Publications

The surface evolution model based on geometric partial differential equation is used to numerically study the kinetics of dewetting and dynamic morphologies for the localized pinhole defect in the surface of the ultrathin solid film with the strongly anisotropic surface energy. Depending on parameters such as the initial depth and width of the pinole, the strength of the attractive substrate potential and the strength of the surface energy anisotropy, the pinhole may either extend to the substrate and thus rupture the film, or evolve to the quasiequilibrium shape while the rest of the film surface undergoes phase separation into a …


Enhanced Stability Of A Dewetting Thin Liquid Film In A Single-Frequency Vibration Field, Mikhail Khenner Jan 2008

Enhanced Stability Of A Dewetting Thin Liquid Film In A Single-Frequency Vibration Field, Mikhail Khenner

Mathematics Faculty Publications

Dynamics of a thin dewetting liquid film on a vertically oscillating substrate is considered. We assume moderate vibration frequency and large (compared to the mean film thickness) vibration amplitude. Using the lubrication approximation and the averaging method, we formulate the coupled sets of equations governing the pulsatile and the averaged fluid flows in the film, and then derive the nonlinear amplitude equation for the averaged film thickness. We show that there exists a window in the frequency-amplitude domain where the parametric and shear-flow instabilities of the pulsatile flow do not emerge. As a consequence, in this window the averaged description …


Enhanced Stability Of A Dewetting Thin Liquid Film In A Single-Frequency Vibration Field, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev Jan 2008

Enhanced Stability Of A Dewetting Thin Liquid Film In A Single-Frequency Vibration Field, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev

Mathematics Faculty Publications

Dynamics of a thin dewetting liquid film on a vertically oscillating substrate is considered. We assume moderate vibration frequency and large (compared to the mean film thickness) vibration amplitude. Using the lubrication approximation and the averaging method, we formulate the coupled sets of equations governing the pulsatile and the averaged fluid flows in the film, and then derive the nonlinear amplitude equation for the averaged film thickness. We show that there exists a window in the frequency-amplitude domain where the parametric and shear-flow instabilities of the pulsatile flow do not emerge. As a consequence, in this window the averaged description …


Enhanced Stability Of A Dewetting Thin Liquid Film In A Single-Frequency Vibration Field, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev Jan 2008

Enhanced Stability Of A Dewetting Thin Liquid Film In A Single-Frequency Vibration Field, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev

Mathematics Faculty Publications

Dynamics of a thin dewetting liquid film on a vertically oscillating substrate is considered. We assume moderate vibration frequency and large (compared to the mean film thickness) vibration amplitude. Using the lubrication approximation and the averaging method, we formulate the coupled sets of equations governing the pulsatile and the averaged fluid flows in the film, and then derive the nonlinear amplitude equation for the averaged film thickness. We show that there exists a window in the frequency-amplitude domain where the parametric and shear-flow instabilities of the pulsatile flow do not emerge. As a consequence, in this window the averaged description …


Morphologies And Kinetics Of A Dewetting Ultrathin Solid Film, Mikhail Khenner Jan 2008

Morphologies And Kinetics Of A Dewetting Ultrathin Solid Film, Mikhail Khenner

Mathematics Faculty Publications

The surface evolution model based on geometric partial differential equation is used to numerically study the kinetics of dewetting and dynamic morphologies for the localized pinhole defect in the surface of the ultrathin solid film with the strongly anisotropic surface energy. Depending on parameters such as the initial depth and width of the pinole, the strength of the attractive substrate potential and the strength of the surface energy anisotropy, the pinhole may either extend to the substrate and thus rupture the film, or evolve to the quasiequilibrium shape while the rest of the film surface undergoes phase separation into a …


Stability Of Transport And Rate Processes [Review], Yaşar Demirel Jun 2005

Stability Of Transport And Rate Processes [Review], Yaşar Demirel

Papers in Thermal Mechanics

About fifty years ago, the Turing instability demonstrated that even simple reaction-diffusion systems might lead to spatial order and differentiation, while the Rayleigh-Bénard instability showed that the maintenance of nonequilibrium might be the source of order in fluids subjected to a thermodynamic force above a critical value. Therefore, distance from global equilibrium in the form of magnitude of a thermodynamic force emerges as another constraint of stability; some systems may enhance perturbations, and evolve to highly organized states called the dissipative structures after a critical distance on the thermodynamic branch. Although the kinetics and transport coefficients represent short-range interactions, chemical …


Design And Simulation Of An Induction Skull Melting System, Taide Tan May 2004

Design And Simulation Of An Induction Skull Melting System, Taide Tan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Incorporating volatile actinides, mainly americium into a metallic fuel pin (MFP) has been a serious problem due to americium’s high vapor pressure. An Induction Skull Melting (ISM) system was identified by Argonne National Laboratory (ANL) as a potential furnace design to cast MFPs. Through the development of the ISM system, the nuclear waste feedstock can be melted and injected into the mold for fabricating MFPs in the advanced nuclear fuel cycles. The main phenomena in this system include: induction melting process, casting process and mass transfer process of americium. Issues related to ISM system design for casting MFPs are discussed …


Design And Analysis For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Xiaolong Wu Aug 2002

Design And Analysis For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Xiaolong Wu

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fundamental issues related to the selection of a metallic fuel casting furnace design are presented and discussed including heating mechanisms, casting issues, crucible design, and issues related to the mass transport of americium. The process of evaluating all of these different criteria is undertaken to select a concept that would have the greatest chance of success for casting americium in a metallic fuel rod. Based on this evaluation process, a concept for the casting of metallic fuel pins containing high vapor pressure materials is selected and discussed. The important physics of this concept include mass transport of americium from the …


Effects Of Concentration And Temperature On The Coupled Heat And Mass Transport In Liquid Mixtures, Yaşar Demirel, Stanley I. Sandler Mar 2001

Effects Of Concentration And Temperature On The Coupled Heat And Mass Transport In Liquid Mixtures, Yaşar Demirel, Stanley I. Sandler

Papers in Thermal Mechanics

Using published experimental data on the thermal conductivity, mutual diffusivity, and heats of transport, the degree of coupling between heat and mass flows has been calculated for binary and ternary nonideal liquid mixtures. The binary mixtures consist of two types: the first is six systems of six-to-eight-carbon straight and branched chain alkanes in chloroform and in carbon tetrachloride; and the second is mixtures of carbon tetrachloride with benzene, toluene, 2-propanone, n-hexane, and 11-octane. The ternary mixture considered is toluene-chlorobenzene-bromobenzene. The published data are available at 35°C, 30°C, and 35°C and ambient pressure. Using the linear nonequilibi-ium thermodynainics (LNET) and the …


Droplet Evaporation And Deformations In An Amplitude Modulated Ultrasonic Field, Nihad E. Daidzic, Rene Stadler, Adrian Melling Apr 1996

Droplet Evaporation And Deformations In An Amplitude Modulated Ultrasonic Field, Nihad E. Daidzic, Rene Stadler, Adrian Melling

Aviation Department Publications

The aim of the report presented is the measurements of droplet oscillations.


A New Spray Evaporation Model Based On Droplet Interface Phenomena, Nihad E. Daidzic, Gangolf Kohnen, Martin Sommerfeld Apr 1995

A New Spray Evaporation Model Based On Droplet Interface Phenomena, Nihad E. Daidzic, Gangolf Kohnen, Martin Sommerfeld

Aviation Department Publications

In this work the influence of droplet shape oscillations on droplet evaporation is shown. Through nonlinear mode interactions, turbulence and aerodynamic triggering of vibrations cause by vortex shedding, droplets always oscillates in spray flows. Droplet shape oscillation cause higher evaporation rates through several physical phenomena such as an average increase of the superficial surface area, periodic micro-convection and boundary layer destruction, and local saturation pressure changes due to local curvature effects. The inviscid theory of small-amplitude droplet oscillations was used which resulted in better agreement with the measurement data of droplet size distributions in sprays for different axial coordinates.


A Mathematical Model And Simulation Of Natural Circulation Loop Thermalhydraulics, Nihad E. Daidzic Mar 1992

A Mathematical Model And Simulation Of Natural Circulation Loop Thermalhydraulics, Nihad E. Daidzic

Aviation Department Publications

In this work, a simple, nonlinear, seventh-order mathematical model with lumped parameter analysis of the thermalhydraulic processes in a natural circulation steam boiler loop is presented. Digital simulation has been performed in order to predict open loop transients in severe accidental situations. Parts of the circulation loop such as the steam drum, downcomer, and riser were modelled separately on the basis of the integral balance equations. The two-phase flow in the steam drum and in the riser was modelled with the aid of a homogeneous-equilibrium, two-phase flow model. Special care was taken to ensure the stability of the numerical scheme, …