Corneliu Balan

Polytechnic Institute Bucharest Romania, Fac. Electro Energetica, Faculty Member

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Corneliu Balan

Diana Broboana

A. Pantet

José María Franco Gómez

Huelva University

Daniela Nistoran

University Politehnica of Bucharest

M. Kozubková

VSB - Technical University of Ostrava

O. Štěpánek

VSB - Technical University of Ostrava

P. Bitala

Jakub Dlabka

VSB - Technical University of Ostrava

Wensu Chen

Curtin University

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Papers by Corneliu Balan

Pure Material Instability and the Concept of Yield Stress

Applied Rheology, Apr 1, 1999

Complex viscoelastic materials generic called "gels", concentrated dispersed systems in viscous f... more Complex viscoelastic materials generic called "gels", concentrated dispersed systems in viscous fluids, develop a stable entanglement or crosslinked network structure at rest, structure which is destroyed during the shearing beyond a critical value of the applied shear stress. This value is associated with the yield stress τ 0 , respectively with the plateau behaviour of the steady flow curve and the sharp decreasing of the viscosity function in viscometric motions, see Fig. 1. In this category of materials we can include: colloidal and flocculated suspensions (Coussot et al.

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Thermodynamically consistent model for electro-rheological materials based on extended thermodynamics

Se basant sur la thermodynamique des phenomenes irreversibles dite elargie, une equation de trans... more Se basant sur la thermodynamique des phenomenes irreversibles dite elargie, une equation de transport du tenseur de Cauchy pour les fluides electrorheologiques est presentee. Contrairement aux travaux recents utilisant les methodes standards de la thermodynamique classique des phenomenes irreversibles, cette nouvelle approche permet de mieux tenir compte des effets plasto-viscoelastiques et du couplage mouvement/champs electriques. De l'examen des cas speciaux, il ressort que les modeles nonlineaires obtenus englobe une grande variete de modeles de type differentiel existant dans la literature. La validite du modele develope est testee dans l'analyse d'un ecoulement cisaille stationnaire soumis a un champ electrique perpendiculaire a la direction de l'ecoulement. Des solutions analytiques sont presentees et discutees sur base de variations de divers parametres.

Rate-type Model for electro-rheological Material Behaviour consistent with Extended Thermodynamics: Application to a steady viscometric flow

Proceedings in applied mathematics & mechanics, Mar 1, 2003

Based on extended thermodynamics, a class of rate-type constitutive equations for electrorheologi... more Based on extended thermodynamics, a class of rate-type constitutive equations for electrorheological materials is presented. It is shown unlike many recent works using standard methods of continuum mechanics, that this approach, which consists in postulating expressions which relate the time derivative of the Cauchy stress to the motion, takes well account of the viscoelastic-plastic effects as well as the coupling between the motion and the electric field. By considering special cases it turns out that the derived nonlinear algebraic model embeds a variety of existing differential models in the literature. The accuracy of the model is illustrated by considering a steady shear flow in which the electric field is applied perpendicularly to the flow direction. Analytical solutions with various parameter variations are obtained and discussed. The model predicts well the behaviour associated with material instabilities observed in viscometric flows for which the existence of the yield stress is required as confirmed by many experiments.

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Experimental and numerical investigations of the jetting regime

IOP conference series, 2023

In this paper we highlight the first stages of liquid injection through a capillary nozzle prior ... more In this paper we highlight the first stages of liquid injection through a capillary nozzle prior to the jet formation regime. We emphasize the asymmetry of water-air interface at the beginning of the injection of liquid and the axial symmetry which follows when the jet is fully formed. Numerical simulations are performed in order to estimate the relaxation of the velocity distribution of the liquid as it leaves the capillary nozzle. The plug flow condition for low-viscosity liquid jets is investigated in relation with the parabolic velocity distribution in the nozzle. The numerical data is also used to characterize the flow during the drop formation and pinch-off, both driven by the action of surface tension.

CFD Study on Convective Heat Exchange between Impinging Gas Jets and Solid Surfaces

Energy Procedia, 2016

The paper is concerned with a CFD numerical investigation using the Fluent code of the convective... more The paper is concerned with a CFD numerical investigation using the Fluent code of the convective heat exchange between an impinging gas jet at room temperature and a structured solid surface with square-shaped grooves which is maintained at constant temperature of 80°C. Reynolds averaged Navier-Stokes simulations coupled with the energy equation are performed for a planar jet on a 3D domain with periodic boundary conditions. The range of jet Reynolds numbers used for the simulations is in the interval from 2000 to 10000, while the jet standoff distance can take different values, ranging from 2 to 10 times the jet width b=2 mm. The detailed distribution of the convective heat transfer coefficient and the mean Nusselt number at the impingement of the air jet on the impacted plate will be inferred. Finally, a comparison between the numerical results, a set of experiments performed and relevant cases from literature is made and conclusions are drawn. One main result of the study is the confirmation of the numerical procedure for the domain used.

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Motion of Magnetic Spheres inside Cylindrical Tubes filled with Newtonian and Viscoelastic Fluids

The paper is dedicated to the experimental study of the motion of magnetized spheres in tubes fil... more The paper is dedicated to the experimental study of the motion of magnetized spheres in tubes filled with pure viscous and viscoelastic fluids. The main goal of the study is to investigate the spheres motion with variable velocities in confined geometries. Due to the influence of the attractive magnetic force the spheres are accelerated, therefore a non-stationary fluid flow is generated in the tubes. The experiments put in evidence the fluctuation frequency and the rotational speed of the sphere during its displacement within the tube. The influence of the fluids rheology on the spheres motion is also determined.

Non-Stationary Simple Couette Flow of the Oldroyd’s 3- Constants Model at Small Reynolds Numbers

In the last decade, the experimental and theoretical investigations on the instabilities of visco... more In the last decade, the experimental and theoretical investigations on the instabilities of viscoelastic fluids put in evidence possible connections between the time oscillations of the flow parameters (in the limit of zero Reynolds numbers), their non-monotone steady flow curves and phenomena as spurt or wall depletion, Larson (1992) and Schowaiter (1988). In this context the study of the non-stationary regime in simple shear motions becomes of great scientifical interest. The aim of this study is to model the onset of the motion in the start-up of Couette flow between parallel planes of the Oldroyd’s 3 constant model with non-monotone flow curve, respectively to investigate the non-stationary material behaviour in the stressing rheological test. In this case it is important to establish: (i) to what extend the assumption that a unique constant steady strain rate is installed in the gap remains valid for constitutive relations with non-monotone steady flow curve, (ii) to compare the time scale of the equation of motion (i. e. the duration up the velocity distribution becomes steady) with the proper time of the constitutive relation (i. e. the duration of the non-stationary regime under a constant velocity distribution). In this paper are presented the first results of our investigations.

Numerical and Experimental Study of the Airflow in a Square Section Bifurcation

Experimental and numerical investigations on the pure material instability of an Oldroyd's 3-constant model

Continuum Mechanics and Thermodynamics, Dec 1, 2001

Displacement and Rupture of Viscous Interface in the Vicinity of the Wall under an Air Current

Numerical modelling of the shear banding flow in the proximity of micro-structures

2017 10th International Symposium on Advanced Topics in Electrical Engineering (ATEE)

The paper is concerned with the numerical modelling of the viscous steady flows in the vicinity o... more The paper is concerned with the numerical modelling of the viscous steady flows in the vicinity of 3D micro-structures. The solutions are obtained for the Carreau generalized Newtonian model with negative flow index n. The main goal of the study is to investigate the shear banding formation between two rotating plates, in the presence of micro-pillars and micro-channels. The phenomenon is generated by the material instability of non-homogeneous complex fluids subjected to different shear rates under a constant shear stress. Simulations are performed in 3D configurations with the Ansys Fluent code.

CT Image-Based Segmentation, 3D Reconstruction and SLA Printing of Human Trachea

2023 13th International Symposium on Advanced Topics in Electrical Engineering (ATEE)

Interface Dynamics and the Influence of Gravity on Droplet Generation in a Y-microchannel

Micromachines, Nov 10, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more

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Material Functions to Characterize the Rheometry of Complex Fluids

2021 12th International Symposium on Advanced Topics in Electrical Engineering (ATEE)

The work reports the experimental investigations of complex fluids rheometry in the presence of p... more The work reports the experimental investigations of complex fluids rheometry in the presence of patterned surfaces. The goal of the study is to explore a novel procedure to detect the shear rates domain where possible wall depletion might be present. The measurements are performed in simple shear with the Anton-Paar MC301 rotational rheometer, the samples (xantan solution and grease) being located between a smooth plate and a special manufactured lower plate patterned with pillars. The rheological behavior of the samples in the tested configurations are characterized by two material functions: (i) the flow curve $\sigma(\dot{\gamma})$ and (ii) the differential viscosity $\boldsymbol{\eta}_{d}=\boldsymbol{d} \sigma / \boldsymbol{d} \dot{\gamma}$, where $\sigma$ is the shear stress and $\dot{\gamma}$ is the shear rate. The experimental data put in evidence an instability region, which is related to the plateau of the flow curve and possible apparent slip at the walls. The existence of the yield stress is also discussed.

Drop Dispensing From Non-Circular Nozzles

2019 International Conference on ENERGY and ENVIRONMENT (CIEM), 2019

The paper investigates the drop formation process in the case of nozzles having non-circular cros... more The paper investigates the drop formation process in the case of nozzles having non-circular cross-sections. The drops are created in a viscous Newtonian immiscible outer liquid, the injected fluids being either Newtonian or viscoelastic. We investigate the influence of nozzle geometry on the frequency of drop generation. We find no alteration of the frequency of drop generation when cross-sections have the same hydraulic diameter and when Newtonian fluids are injected. We also propose a simple model of the advance velocity of the apex of the drop based on experimental observations regarding the final stages of drop formation.

Influence of Viscosity on Radial Diffusion of Fluids in Paper Substrates

2021 12th International Symposium on Advanced Topics in Electrical Engineering (ATEE), 2021

The current increasing interest in portable biosensing platforms led to their development on flex... more The current increasing interest in portable biosensing platforms led to their development on flexible porous substrates, such as filter paper. As these devices rely on fluid transport under capillary action, without the use of an external force, studies of the diffusion process can provide useful data for optimizing their working capabilities. We present here the results obtained by experimentally studying the radial diffusion of various fluids. The diffusion in filter paper has been recorded for six fluids with different viscosity. For each of them, the displacement of the fluid front has been measured along eight radial directions and then we investigated the possibility of describing this diffusion process using Gillespie’s model.

Drop dispensing in a viscous outer liquid

INCAS BULLETIN, 2017

The formation and detachment of Newtonian drops in viscous external liquids is investigated. A gl... more The formation and detachment of Newtonian drops in viscous external liquids is investigated. A global analysis of two necking processes is presented in order to highlight the behavior of such thinning phenomena, when controlled either by inertia or by viscous effects. Moving detached droplets in an immiscible outer liquid were studied in terms of velocity and drop-travel distance. Theoretical predictions are proposed and compared with experimental data for the volume of the drop and for the subsequent dynamics that follow after detachment. Our investigations point out that the drop rapidly achieves constant velocity, the value of it being in a satisfactory agreement with the model. Both the influence of the flow rate and that of the material properties on drop volume are pursued.

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A peculiar behaviour of liquid jet impact

E3S Web of Conferences, 2019

Coalescent masses of fluid, formed upon liquid jet impact, should exhibit either dripping or jett... more Coalescent masses of fluid, formed upon liquid jet impact, should exhibit either dripping or jetting regardless of the distance between the nozzles. The study reveals that above a certain flow rate, by increasing this distance, the coalescent mass enters a dripping state, when only a jetting regime is previously present. This is followed again by a jetting regime before breakup which occurs at a critical distance. The upper limit of this dripping state is achieved when Bond number is equal to unity, this result being valid below a certain critical Reynolds number.

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Time evolution of dimethyl carbinol in water vortex rings

Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies VII, 2015

The paper is concerned with the experimental study of the time evolution of a single laminar vort... more The paper is concerned with the experimental study of the time evolution of a single laminar vortex ring generated at the interface between water and dimethyl carbinol. The experiments were performed by the submerged injection with a constant rate of dimethyl carbinol (isopropyl alcohol) in a water tank. The dynamics of the vortex formation was recorded at 1000 fps with a Photron Fastcam SA1 camera, equipped with a microscopic Edmund Optics objective. A symmetrical buoyant vortex ring with an elongated topology was observed at the interface between the two immiscible liquids. The analyses of the time dependence of the vortex rings disclosed three regions for the evolution of the interface: one dominated by inertia force, a transition region and a third region, dominated by buoyancy force.

HISOLD 4P Q&R, COST project for solder material innovations and solder joint properties assessment

2009 15th International Symposium for Design and Technology of Electronics Packages (SIITME), 2009

The solder joints properties are in connection with their microstructure, which is the result of ... more The solder joints properties are in connection with their microstructure, which is the result of the soldering process temperature gradient action over the trinomial solder alloy/paste, electronic components terminals/pin and PCBs pads characteristics (4P soldering model). The temperature gradient was determinated by the specific thermal profile of the soldering process. As part of COST Action MP0602, Working Group 2 (The

Pure Material Instability and the Concept of Yield Stress

Applied Rheology, Apr 1, 1999

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Thermodynamically consistent model for electro-rheological materials based on extended thermodynamics

Rate-type Model for electro-rheological Material Behaviour consistent with Extended Thermodynamics: Application to a steady viscometric flow

Proceedings in applied mathematics & mechanics, Mar 1, 2003

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Experimental and numerical investigations of the jetting regime

IOP conference series, 2023

CFD Study on Convective Heat Exchange between Impinging Gas Jets and Solid Surfaces

Energy Procedia, 2016

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Motion of Magnetic Spheres inside Cylindrical Tubes filled with Newtonian and Viscoelastic Fluids

Non-Stationary Simple Couette Flow of the Oldroyd’s 3- Constants Model at Small Reynolds Numbers

Numerical and Experimental Study of the Airflow in a Square Section Bifurcation

Experimental and numerical investigations on the pure material instability of an Oldroyd's 3-constant model

Continuum Mechanics and Thermodynamics, Dec 1, 2001

Displacement and Rupture of Viscous Interface in the Vicinity of the Wall under an Air Current

Numerical modelling of the shear banding flow in the proximity of micro-structures

2017 10th International Symposium on Advanced Topics in Electrical Engineering (ATEE)

CT Image-Based Segmentation, 3D Reconstruction and SLA Printing of Human Trachea

2023 13th International Symposium on Advanced Topics in Electrical Engineering (ATEE)

Interface Dynamics and the Influence of Gravity on Droplet Generation in a Y-microchannel

Micromachines, Nov 10, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more

Download

Material Functions to Characterize the Rheometry of Complex Fluids

2021 12th International Symposium on Advanced Topics in Electrical Engineering (ATEE)

Drop Dispensing From Non-Circular Nozzles

2019 International Conference on ENERGY and ENVIRONMENT (CIEM), 2019

Influence of Viscosity on Radial Diffusion of Fluids in Paper Substrates

2021 12th International Symposium on Advanced Topics in Electrical Engineering (ATEE), 2021

Drop dispensing in a viscous outer liquid

INCAS BULLETIN, 2017

Download

A peculiar behaviour of liquid jet impact

E3S Web of Conferences, 2019

Download

Time evolution of dimethyl carbinol in water vortex rings

Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies VII, 2015

HISOLD 4P Q&R, COST project for solder material innovations and solder joint properties assessment

2009 15th International Symposium for Design and Technology of Electronics Packages (SIITME), 2009

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