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Experimental investigation and mathematical modeling of triode PEM fuel cells

Authors E. Martino, G. Koilias, M. Athanasiou, A. Katsaounis, Y. Dimakopoulos, J. Tsamopoulos, C.G. Vayenas Abstract The triode operation of ...
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Discretization of three-dimensional free surface flows and moving boundary problems via elliptic grid methods based on variational principles

Authors D.Fraggedakis, J.Papaioannou, Y.Dimakopoulos, J.Tsamopoulos Abstract A new boundary-fitted technique to describe free surface and moving boundary problems is presented ...
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On the order of accuracy of the divergence theorem(Green-Gauss) method for calculating the gradient infinite volume methods

Authors A. Syrakos, S. Varchanis, Y. Dimakopoulos, A. Goulas, J. Tsamopoulos Abstract The divergence theorem (or Green-Gauss) gradient scheme is ...
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On the degree of wetting of a slit by a liquid filmflowing along an inclined plane

Authors D.Pettas, G.Karapetsas, Y.Dimakopoulos, J.Tsamopoulos Abstract Liquid film flow along an inclined plane featuring a slit, normal to the main ...
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Numerical simulations of complex yield-stress fluid flows

Authors Evan Mitsoulis, John Tsamopoulos Abstract Viscoplasticity is characterized by a yield stress, below which the materials will not deform ...
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Transient flow of gravity-driven viscous films over 3D patterned substrates: conditions leading to Wenzel, Cassie and intermediate states

Authors G. Karapetsas, N. K. Lampropoulos, Y. Dimakopoulos, J. Tsamopoulos Abstract We examine the transient film flow under the action ...
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Yielding the yield-stress analysis: A study focused on the effects of elasticity on the settling of a single spherical particle in simple yield-stress fluids

Authors Fraggedakis D., Dimakopoulos Y., Tsamopoulos J. Abstract The sedimentation of a single particle in materials that exhibit simultaneously elastic, ...
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On the velocity discontinuity at a critical volume of a bubble rising in a viscoelastic fluid

Authors Fraggedakis D., Pavlidis M., Dimakopoulos Y., Tsamopoulos J. Abstract We examine the abrupt increase in the rise velocity of ...
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Stress-gradient induced migration of polymers in thin films flowing over smoothly corrugated surfaces

Authors Tsouka S., Dimakopoulos Y., Tsamopoulos J. Abstract We consider the two dimensional, steady flow of a dilute polymer solution ...
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Transient flow of gravity-driven viscous films over substrates with rectangular topographical features

Authors Lampropoulos N.K., Dimakopoulos Y., Tsamopoulos J. Abstract We study the transient, two-dimensional film flow over solid substrates with variable ...
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Viscoplastic flow in an extrusion damper

Authors Syrakos A., Dimakopoulos Y., Georgiou G.C., Tsamopoulos J. Abstract Numerical simulations of the flow in an extrusion damper are ...
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Steady viscoelastic film flow over 2D Topography: II. The effect of capillarity, inertia and substrate geometry

Authors Pavlidis M., Karapetsas G., Dimakopoulos Y., Tsamopoulos J. Abstract We examine and compare five constitutive models, which have been ...
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Yielding the yield stress analysis: A thorough comparison of recently proposed elasto-visco-plastic (EVP) fluid models

Authors Fraggedakis D., Dimakopoulos Y., Tsamopoulos J. Abstract We examine and compare five constitutive models, which have been recently proposed ...
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Hemodynamics in stenotic vessels of small diameter under steady state conditions: Effect of viscoelasticity and migration of red blood cells

Authors Dimakopoulos Y., Kelesidis G., Tsouka S., Georgiou G.C., Tsamopoulos J. Abstract BACKGROUND: In microcirculation, the non-Newtonian behavior of blood ...
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Flow of two immiscible fluids in a periodically constricted tube: Transitions to stratified, segmented, churn, spray, or segregated flow

Authors Fraggedakis D., Kouris C., Dimakopoulos Y., Tsamopoulos J. Abstract We study the flow of two immiscible, Newtonian fluids in ...
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On the origin of extrusion instabilities: Linear stability analysis of the viscoelastic die swell

Authors Pettas D., Karapetsas G., Dimakopoulos Y., Tsamopoulos J. Abstract It is well-known that by increasing the flow rate in ...
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Bubble deformation and growth inside viscoelastic filaments undergoing very large extensions

Authors Papaioannou J., Giannousakis A., Dimakopoulos Y., Tsamopoulos J. Abstract Motivated by the probe experiment for characterizing the adhesion strength ...
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On the flow characteristics of the conical Minoan pipes used in water supply systems, via computational fluid dynamics simulations

Authors Tseropoulos G., Dimakopoulos Y., Tsamopoulos J., Lyberatos G. Abstract The Minoan Terracotta pipes with their conical shape were widely ...
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On the stick-slip flow from slit and cylindrical dies of a Phan-Thien and Tanner fluid model. II. Linear stability analysis

Authors Karapetsas G., Tsamopoulos J. Abstract During extrusion of viscoelastic fluids various flow instabilities may arise resulting in a distorted ...
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Steady bubble rise in Herschel-Bulkley fluids and comparison of predictions via the Augmented Lagrangian Method with those via the Papanastasiou model

Authors Dimakopoulos Y., Pavlidis M., Tsamopoulos J. Abstract The steady, buoyancy-driven rise of a bubble in a Herschel-Bulkley fluid is ...
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A fully implicit 3D elliptic mesh generator for moving boundary flow problems with large arbitrary deformations

Authors Papaioannou J.G., Dimakopoulos Y., Tsamopoulos J.A. Abstract Because of the three dimensional nature of many physical problems encountered in ...
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Viscous effects on the oscillations of two equal and deformable bubbles under a step change in pressure

Authors Chatzidai N., Dimakopoulos Y., Tsamopoulos J. Abstract According to linear theory and assuming the liquids to be inviscid and ...
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Steady viscoelastic film flow over 2D topography: I. The effect of viscoelastic properties under creeping flow

Authors Pavlidis M., Dimakopoulos Y., Tsamopoulos J. Abstract Two-dimensional, steady flow of a viscoelastic film over a periodic topography under ...
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On the elliptic mesh generation in domains containing multiple inclusions and undergoing large deformations

Authors Chatzidai N., Giannousakis A., Dimakopoulos Y., Tsamopoulos J. Abstract We present an improved method to generate a sequence of ...
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On the transient coating of a straight tube with a viscoelastic material

Authors Dimakopoulos Y., Tsamopoulos J. Abstract We examine the pressure-driven coating of a straight, long tube with a finite amount ...
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Fully developed flow of a viscoelastic film down a vertical cylindrical or planar wall

Authors Pavlidis M., Dimakopoulos Y., Tsamopoulos J. Abstract The one-dimensional, gravity-driven film flow of a linear (l) or exponential (e) ...
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Injection of a viscoplastic material inside a tube or between two parallel disks: Conditions for wall detachment of the advancing front

Authors Papaioannou J., Karapetsas G., Dimakopoulos Y., Tsamopoulos J. Abstract The injection of a viscoplastic material, driven by a constant ...
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On the stick-slip flow from slit and cylindrical dies of a Phan-Thien and Tanner fluid model. I. steady state

Authors Karapetsas G., Tsamopoulos J. Abstract The steady planar and cylindrical stick-slip flows for a viscoelastic fluid are computed using ...
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Steady bubble rise and deformation in Newtonian and viscoplastic fluids and conditions for bubble entrapment

Authors Tsamopoulos J., Dimakopoulos Y., Chatzidai N., Karapetsas G., Pavlidis M. Abstract We examine the buoyancy-driven rise of a bubble ...
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On the interaction of an air jet with a viscoelastic tubular film produced during the film blowing process

Authors Housiadas K., Tsamopoulos J. Abstract The effect of the air jet, which is used to increase the process stability ...
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Transient coating of the inner wall of a straight tube with a viscoelastic material

Authors Dimakopoulos Y., Pavlidis M., Tsamopoulos J. Abstract We examine the pressure-driven coating of a straight tube with a viscoelastic ...
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Steady extrusion of viscoelastic materials from an annular die

Authors Karapetsas G., Tsamopoulos J. Abstract The steady extrusion of viscoelastic materials from a straight, annular die is studied theoretically ...
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Two- and three-dimensional instabilities in the film blowing process

Authors Housiadas K.D., Klidis G., Tsamopoulos J. Abstract We examine the film blowing process (FBP), which is widely used for ...
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Transient displacement of Newtonian and viscoplastic liquids by air in complex tubes

Authors Dimakopoulos Y., Tsamopoulos J. Abstract We study the transient displacement of Newtonian and viscoplastic liquids by highly pressurized air ...
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A direct comparison between volume and surface tracking methods with a boundary-fitted coordinate transformation and third-order upwinding

Authors Zacharioudaki M., Kouris C., Dimakopoulos Y., Tsamopoulos J. Abstract A Volume Tracking (VT) and a Front Tracking (FT) algorithm ...
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Spherical capsules in three-dimensional unbounded Stokes flows: Effect of the membrane constitutive law and onset of buckling

Authors Lac E., Barthès-Biesel D., Pelekasis N.A., Tsamopoulos J. Abstract The dynamic response of an initially spherical capsule subject to ...
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Gas-assisted injection molding with fluids partially occupying straight or complex tubes

Authors Dimakopoulos Y., Tsamopoulos J. Abstract We examine the displacement by pressurized air of a liquid, which only partially occupies ...
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Transient squeeze flow of viscoplastic materials

Authors Karapetsas G., Tsamopoulos J. Abstract The transient, axisymmetric squeezing of viscoplastic materials under creeping flow conditions is examined. The ...
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Numerical simulation of multiple bubbles growing in a Newtonian liquid filament undergoing stretching

Authors Foteinopoulou K., Mavrantzas V.G., Dimakopoulos Y., Tsamopoulos J. Abstract Our recent finite element-based study of the deformation of a ...
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Transient displacement of Newtonian liquids by gas in periodically constricted tubes

Authors Dimakopoulos Y., Tsamopoulos J. Abstract The displacement of viscous liquids by pressurized gas from harmonically undulated tubes of finite ...
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Secondary Bjerknes forces between two bubbles and the phenomenon of acoustic streamers

Authors Pelekasis N.A., Gaki A., Doinikov A., Tsamopoulos J.A. Abstract The translational velocities of two spherical gas bubbles oscillating in ...
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Risk analysis of industrial structures under extreme transient loads

Authors Talaslidis D.G., Manolis G.D., Paraskevopoulos E., Panagiotopoulos C., Pelekasis N., Tsamopoulos J.A. Abstract A modular analysis package is assembled ...
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On the gas-penetration in straight tubes completely filled with a viscoelastic fluid

Authors Dimakopoulos Y., Tsamopoulos J. Abstract We examine the transient displacement of viscoelastic fluids by a gas in straight cylindrical ...
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Numerical simulation of bubble growth in Newtonian and viscoelastic filaments undergoing stretching

Authors Foteinopoulou K., Mavrantzas V.G., Tsamopoulos J. Abstract Numerical results are presented concerning bubble growth in Newtonian and viscoelastic filaments ...
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Dynamics of the axisymmetric core-annular flow. II. The less viscous fluid in the core, saw tooth waves

Authors Kouris C., Tsamopoulos J. Abstract The nonlinear dynamics of the concentric, two-phase flow of two immiscible fluids in a ...
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Transient displacement of a viscoplastic material by air in straight and suddenly constricted tubes

Authors Dimakopoulos Y., Tsamopoulos J. Abstract We examine the transient displacement of a viscoplastic material from straight or suddenly constricted ...
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Transient displacement of a Newtonian fluid by air in straight or suddenly constricted tubes

Authors Dimakopoulos Y., Tsamopoulos J. Abstract We study the displacement of a viscous fluid by highly pressurized air in a ...
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Comparison of spectral and finite element methods applied to the study of the core-annular flow in an undulating tube

Authors Kouris C., Dimakopoulos Y., Georgiou G., Tsamopoulos J. Abstract A Galerkin/finite element and a pseudo-spectral method, in conjunction with ...
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A quasi-elliptic transformation for moving boundary problems with large anisotropic deformations

Authors Dimakopoulos Y., Tsamopoulos J. Abstract We have developed a quasi-elliptic set of equations for generating a discretization mesh that ...
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Laminar boundary layer flow of saturated vapor and its condensate over a horizontal tube

Authors Smyrnaios D.N., Pelekasis N.A., Tsamopoulos J.A. Abstract The steady two-dimensional laminar flow of a stream of saturated vapor flowing ...
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Core-annular flow in a periodically constricted circular tube. Part 2. Nonlinear dynamics

Authors Kouris C., Tsamopoulos J. Abstract Nonlinear dynamics of the concentric, two-phase flow of two immiscible fluids in a circular ...
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Dynamics of axisymmetric core-annular flow in a straight tube. I. The more viscous fluid in the core, bamboo waves

Authors Kouris C., Tsamopoulos J. Abstract Nonlinear dynamics of the concentric, two-phase flow of two immiscible fluids in a circular ...
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Core-annular flow in a periodically constricted circular tube. Part 1. Steady-state, linear stability and energy analysis

Authors Kouris C., Tsamopoulos J. Abstract The concentric, two-phase flow of two immiscible fluids in a tube of sinusoidally varying ...
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Linear stability of a gas boundary layer flowing past a thin liquid film over a flat plate

Authors Pelekasis N.A., Tsamopoulos J.A. Abstract The flow of a gas stream past a flat plate under the influence of ...
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Squeeze flow of Bingham plastics

Authors Smyrnaios D.N., Tsamopoulos J.A. Abstract The axisymmetric squeeze flow of viscoplastic materials is examined using either the original Bingham ...
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Linear oscillations and stability of a liquid bridge in an axial electric field

Authors Pelekasis N.A., Economou K., Tsamopoulos J.A. Abstract Small amplitude oscillations of viscous, capillary bridges are studied in the presence ...
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Unsteady extrusion of a viscoelastic annular film I. General model and its numerical solution

Authors Housiadas K., Tsamopoulos J. Abstract The unsteady extrusion of a viscoelastic film from an annular and axisymmetric die is ...
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Unsteady extrusion of a viscoelastic annular film II. Linearized model and its analytical solution

Authors Housiadas K., Tsamopoulos J. Abstract The unsteady extrusion of a viscoelastic film from an annular and axisymmetric die is ...
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Cooling of a viscoelastic film during unsteady extrusion from an annular die

Authors Housiadas K., Tsamopoulos J. Abstract The unsteady extrusion of a viscoelastic film from an annular and axisymmetric die is ...
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The steady annular extrusion of a Newtonian liquid under gravity and surface tension

Authors Housiadas K., Georgiou G., Tsamopoulos J. Abstract The steady extrusion of a Newtonian liquid through an annular die and ...
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Concentric core-annular flow in a circular tube of slowly varying cross-section

Authors Kouris C., Tsamopoulos J. Abstract The concentric, two-phase flow of two immiscible fluids in a tube of sinusoidally varying ...
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Boundary layer flow of air past solid surfaces in the presence of rainfall

Authors Smyrnaios D.N., Pelekasis N.A., Tsamopoulos J.A. Abstract The steady two-dimensional laminar flow of an air stream, flowing past a ...
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Steady flow of a two-dimensional film under pressure

Authors Georgiou G.C., Tsamopoulos J., Schultz W.W. Abstract We use finite elements and the full Newton iteration method to solve ...
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Unsteady state operation of catalytic particles with constant and periodically changing degree of external wetting

Authors Kouris Ch., Neophytides St., Vayenas C.G., Tsamopoulos J. Abstract A dynamic model is developed to described two parallel reactions ...
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On the spin coating of viscoplastic fluids

Authors Tsamopoulos J.A., Chen M.F., Borkar A.V. Abstract The spin coating of a viscoplastic material is studied using a continuous ...
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Unsteady flow of an axisymmetric annular film under gravity

Authors Housiadas K., Tsamopoulos J. Abstract The unsteady flow of an annular and axisymmetric film under gravity is examined. This ...
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Dynamics of charged and conducting drops via the hybrid finite-boundary element method

Authors Pelekasis N.A., Tsamopoulos J.A. Abstract A numerical study on the dynamic behaviour of a charged and conducting drop, with ...
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Start-up flow of an upper convected maxwell fluid over a rotating disk

Authors Borkar A.V., Tsamopoulos J.A. Abstract Start-up flow of an Upper Convected Maxwell (UCM) fluid over a disk set in ...
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Spin coating of viscoelastic and nonvolatile fluids over a planar disk

Authors Borkar A.V., Tsamopoulos J.A., Gupta S.A., Gupta R.K. Abstract Spin coating of two commercially used polymer solutions is studied ...
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Transient rotational flow of an Oldroyd-B fluid over a disk

Authors Tsamopoulos J., Borkar A. Abstract The transient flow of an Oldroyd-B fluid over an infinite disk set in rotation ...
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Nonlinear dynamics of capillary bridges: Experiments

Authors Mollot D.J., Ashgriz N., Tsamopoulos J., Chen T.-Y. Abstract An experimental investigation of forced and free oscillations of liquid ...
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Bjerknes forces between two bubbles. Part 1. Response to a step change in pressure

Authors Pelekasis N.A., Tsamopoulos J.A. Abstract It is well known from experiments in acoustic cavitation that two bubbles pulsating in ...
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Nonlinear dynamics of capillary bridges: Theory

Authors Chen T.-Y., Tsamopoulos J. Abstract Finite-amplitude, forced and free oscillations of capillary bridges are studied. They are characterized by ...
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Bjerknes forces between two bubbles. Part 2. Response to an oscillatory pressure field

Authors Pelekasis N.A., Tsamopoulos J.A. Abstract The motion of two gas bubbles in response to an oscillatory disturbance in the ...
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A model for the catalytic growth of carbon filaments

Authors Chitrapu P., Lund C.R.F., Tsamopoulos J.A. Abstract A two-dimensional model of the growth of filamentous carbon using an iron ...
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A hybrid finite-boundary element method for inviscid flows with free surface

Authors Pelekasis N.A., Tsamopoulos J.A., Manolis G.D. Abstract Different formulations of free-surface inviscid flows lead to Fredholm integral equations of ...
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Capillary bridges between parallel and non-parallel surfaces and their stability

Authors Chen T.-Y., Tsamopoulos J.A., Good R.J. Abstract Equilibrium shapes and the stability of capillary bridges between parallel and nonparallel ...
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Viscous oscillations of capillary bridges

Authors Tsamopoulos J., Chen T.-Y., Borkar A. Abstract Small-amplitude oscillations of viscous, capillary bridges are characterized by their frequency and ...
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Inflation dynamnics of fluid annular menisci inside a mold cavity-II. Deformation driven by large gas pressures

Authors Poslinski A.J., Orlicki D., Tsamopoulos J.A. Abstract Inflation of an annular meniscus within a mold cavity is an important ...
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Nonlinear oscillations of liquid shells in zero gravity

Authors Pelekasis N.A., Tsamopoulos J.A., Manolis G.D. Abstract It has been shown experimentally (Lee et al. 1982) that water drops ...
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Inflation dynamics of fluid annular menisci inside a mold cavity-I. Deformation driven by small gas pressures

Authors Poslinski A.J., Tsamopoulos J.A. Abstract Axisymmetric inflation of fluid annular menisci under an imposed pressure gradient is analyzed by ...
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Boundary-layer analysis of the dynamics of axisymmetric capillary bridges

Authors Borkar A., Tsamopoulos J. Abstract Small-amplitude oscillations of capillary bridges are examined in the limit of large modified Reynolds ...
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Carbon gasification by group VIII metal catalysts

Authors Vincett M.E., Tsamopoulos J.A., Lund C.R.F. Abstract A mathematical model for the steam gasification of carbon using group VIII ...
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Nonisothermal parison inflation in blow molding

Authors Poslinski A.J., Tsamopoulos J.A. Abstract Nonisothermal inflation of a viscous annular parison and its cooling and solidification before and ...
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An Effective Medium Approach for Modeling Chemical Vapor Infiltration of Porous Ceramic Materials

Authors Gupte S.M., Tsamopoulos J.A. Abstract The process of chemical vapor infiltration for densification of porous ceramic preforms consists of ...
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Forced-Flow Chemical Vapor Infiltration of Porous Ceramic Materials

Authors Gupte S.M., Tsamopoulos J.A. Abstract A mathematical model for forced-flow chemical vapor infiltration (CVI) for densification of porous ceramic ...
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Equilibrium shapes and stability of charged and conducting drops

Authors Pelekasis N.A., Tsamopoulos J.A., Manolis G.D. Abstract It was shown by Rayleigh [Philos. Mag. 14, 184 (1882)] that a ...
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Gasification of graphite by the channeling action of metal catalysts

Authors Tsamopoulos J.A., Dandekar H.W., Scholtz J.H. Abstract The channeling action of metal catalysts during graphite gasification is studied. A ...
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Densification of Porous Materials by Chemical Vapor Infiltration

Authors Gupte S.M., Tsamopoulos J.A. Abstract A mathematical model that describes the combined diffusion and reaction of trichloromethylsilane in a ...
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Equilibrium shapes and stability of captive annular menisci

Authors Tsamopoulos J.A., Poslinski A.J., Ryan M.E. Abstract Equilibrium shapes and stability of annular fluid menisci held together by surface ...
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Creeping motion of a sphere through a Bingham plastic

Authors Beris A.N., Tsamopoulos J.A., Armstrong R.C., Brown R.A. Abstract A solid sphere falling through a Bingham plastic moves in ...
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Nonlinear Dynamics and Break Up of Charged Drops.

Authors Tsamopoulos John A., Brown Robert A. Abstract The objective of this paper is to develop a rigorous framework for ...
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Resonant oscillations of inviscid charged drops

Authors Tsamopoulos J.A., Brown R.A. Abstract Moderate-amplitude axisymmetric oscillations of charged inviscid drops held together by surface tension are calculated ...
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Creeping motion of a sphere through a Bingham plastic.

Authors Beris A.N., Tsamopoulos J.A., Armstrong R.C., Brown R.A. Abstract A solid sphere falling through a Bingham plastic moves in ...
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Nonlinear oscillations of inviscid drops and bubbles

Authors Tsamopoulos J.A., Brown R.A. Abstract Moderate-amplitude axisymmetric oscillations of incompressible inviscid drops and bubbles are studied using a Poincaré-Lindstedt ...
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