Amina Mataoui - Academia.edu (original) (raw)

Papers by Amina Mataoui

Journal of Applied Fluid Mechanics, Nov 1, 2019

This paper investigates the influence of a weak-jet on the development of a turbulent axisymmetri... more This paper investigates the influence of a weak-jet on the development of a turbulent axisymmetric strong jet. A parametric study is carried out to evaluate simultaneously the effect to the jets-spacing (S/D=3 and S/D=7.5) and their velocity ratios in range 0≤λ≤1. The mixing phenomenon is studied numerically by the finite volume method using the 3D-RANS second-order model, which gives a good agreement with the available data. Three distinct regions of this type of jets interaction are evidenced. This study confirms that the jets spacing affects strongly the converging region and has a minor effect on the combining region. It is found that the weak jet attracts the strong jet and the combining region extends from 30D to 40D where the self-similarity of a single jet is obtained. The jet width decreases when velocity ratio and jets spacing augment. In the combining region, in comparison with the free jet, it is found that the addition of a weak-jet increases the decay rate of the centerline velocity.

WIT transactions on engineering sciences, May 28, 2002

Engineering Analysis with Boundary Elements

Chemical Engineering Research & Design, 2017

Applied Thermal Engineering, 2017

FDMP: Fluid Dynamics & Materials Processing, Jun 1, 2014

The present work is devoted to the numerical study of the interaction of an inclined plane turbul... more The present work is devoted to the numerical study of the interaction of an inclined plane turbulent jet with a moving horizontal isothermal hot wall. The inclination of the jet allows the control of the stagnation point location. Numerical predictions based on statistical modeling are obtained using a second order Reynolds stress turbulence model coupled to an enhanced wall treatment. For a given impinging distance H (H =8e), the considered problem parameters are: (a) jet exit Reynolds number (Re, based on the thickness "e" of the nozzle) in the range from 10000 to 25000, (b) surface-to-jet velocity ratio Rsj from left to right; ranging between 0 and1.75 and (c) optimal inclination angle of the jet between 0 ̊ to 25 ̊. The calculations are in good agreement with the available data. The numerical results show that the heat transfer is greatly influenced by the velocities of the jet and the moving wall. In particular, the local Nusselt number decreases with increasing surface-to-jet velocity ratios (until Rsj=1). Optimal inclination of the jet can be used to enhance heat transfer and modify the stagnation point location. The distribution of average Nusselt number is correlated with typical problem parameters.

Thermal Science, 2015

Convective heat transfer from an isothermal hot cylindrical cavity due to a turbulent round jet i... more Convective heat transfer from an isothermal hot cylindrical cavity due to a turbulent round jet impingement is investigated numerically. Three-dimensional turbulent flow is considered in this work. The Reynolds stress second order turbulence model with wall standard treatment is used for the turbulence predictions the problem parameters are the jet exit Reynolds number, ranging from 2•10 4 to 10 5 and the normalized impinging distance to the cavity bottom and the jet exit L f , ranging from 4 to 35. The computed flow patterns and isotherms for various combinations of these parameters are analyzed in order to understand the effect of the cavity confinement on the heat transfer phenomena. The flow in the cavity is divided into three parts, the area of free jet, and the area of the jet interaction with the reverse flow and the semi-quiescent flow in the region of the cavity bottom. The distribution of the local and mean Nusselt numbers along the cavity walls for above combinations of the flow parameters are detailed. Results are compared against to corresponding cases for impinging jet on a plate for the case of the bottom wall. The analysis reveals that the average Nusselt number increases considerably with the jet exit Reynolds number. Finally, it was found that the average Nusselt number at the stagnation point could be correlated by a relationship in the form Nu = f(L f , Re).

Progress in Computational Fluid Dynamics, 2016

L'Ecran marocain, Oct 29, 2008

Dans ce travail, on s\'interesse a l\'etude du transfert de chaleur d\'une plaque pla... more Dans ce travail, on s\'interesse a l\'etude du transfert de chaleur d\'une plaque plane soumise a l\'action d\'un jet d\'air perpendiculaire. L\'etude de la possibilite d\'ameliorer le transfert de chaleur est effectuee en fonction des parametres caracteristiques de l\'interaction jet - paroi. Le probleme du jet rond turbulent frappant perpendiculairement une paroi verticale est analyse numeriquement a l'aide du modele de turbulence a deux equations du type energie-dissipation (k-e). La zone proche paroi solide a necessite un traitement particulier par une methode economique dite « fonctions de paroi ». La resolution numerique des equations aux variables primitives est realisee a l'aide de la methode des volumes finis. Un bon accord est obtenu avec les resultats experimentaux. L'influence de la distance entre jet et parois est analysee. A computational study of the impingement of a thermally turbulent jet on a solid plate, using k - e model, is reported. The possibility of improving the heat transfer is carried out according to the characteristic parameters of the interaction jet-wall. The close zone solid wall required a particular treatment using an economic method known as \"wall functions\". The numerical resolution of the equations is carried out using the finite volume method. For a fixed nozzle–plate distance, the influence of the Reynolds number on the stagnation point heat transfer is investigated. Good agreement with experimental results is observed. The influence of the nozzle–plate distance on the stagnation point Nusselt number is also discussed. Keywords : Jets, axisymetrie, modele k - e, champ de vitesse, transfert de chaleur; Iimpinging jets; axisymmetric; two-dimensional; k - e turbulent model; velocity field, heat transfer. Journal des Sciences Pour l\'Ingenieur. Vol. 9 2008: pp. 47-54

Journal of Nanofluids, Mar 1, 2015

ABSTRACT This work presents a numerical investigation of turbulent forced convection of a nanoflu... more ABSTRACT This work presents a numerical investigation of turbulent forced convection of a nanofluid over a heated cavity in a horizontal duct. Heat transfers in separated flows are frequently encountered in engineering applications, such as: heat exchangers, axial and centrifugal compressor blades, gas turbines blades, and microelectronic circuit boards. Thus, it is very essential to understand the mechanisms of heat transfer in such regions in order to enhance heat transfer. Different volumes fractions of nanoparticles are presented in the base fluid besides of different types of nanoparticles are used. The objective of this study is to check the effect of nanofluid on heat transfer in such configuration. Numerical simulations are performed for pure water and four nanofluids (Cu, CuO, Ag and Al2O3). The results are analyzed through the thermal and dynamical fields with a particular interest to the skin friction coefficient and Nusselt number evolutions. The average Nusselt number increases with the volume fraction of nanoparticles for the whole tested range of Reynolds number. A correlation of average Nusselt number versus Reynolds number and volume fraction of each type of nanoparticles over the cavity wall is proposed in this paper.

International Journal of Flow Control, Sep 1, 2014

This work is about the interaction of three parallel non-ventilated turbulent slot jets. The cent... more This work is about the interaction of three parallel non-ventilated turbulent slot jets. The central jet is set symmetrically between two identical lateral heated jets. There are so many applications of this flow configuration in engineering such as gas turbine airfoils, heating or cooling surfaces, combustion and mixing flow. Computations are achieved by finite volume method. The numerical predictions confirm the three types of flow patterns given by the available flow visualization. Furthermore, a fourth type of flow pattern is found in this paper. For a given distance between two neighboring jets of 11 times the nozzle thickness (D 0 = 11a), the effects of the velocity ratio on the dynamical and thermal flow fields are examined. Therefore, the contours of the streamlines, vorticity, pressure, kenetic turbulence energy and isotherms for several velocity ratios (0.3 ≤ λ ≤ 15), are discussed in this paper. Several temperature gaps (10°C ≤ ΔT≤ 50°C) between the two neighboring jets are considered. Both centerline and crosswise profiles of the averaged velocity and temperature are found similar for several temperature gaps at each velocity ratio. In the developed region, a comparison between the available data of the single free jet and those of the three jets is carried out in order to evidence the effect of the presence of the two side jets on the mixing phenomenon and heat transfer. It was found that the addition of the side jets increases the rate of decrease of the average velocity along the central jet axis for the flow of type A and decreases the rate of decrease for the other types of flow. The effect of various types of flow on the spreading decrease of the velocity and the temperature in the fully developed flow region is also investigated. The diffusion of temperature depends strongly on velocity ratio (λ).

Thermophysics and Aeromechanics, 2020

This work investigates the turbulent flow in a channel roughened by seven ribs of rectangular cro... more This work investigates the turbulent flow in a channel roughened by seven ribs of rectangular cross section disposed transversely. The flow configurations of identical ribs from the first one generate a large eddy spreading along the top of the two first ribs, trapping the flow of the first cavity. The widening of the first rib may solve this problem. Therefore, this flow configuration might be required in building structure applications necessitating regular structures from the first cavity. Streamlines contours indicates that the first rib behaves as a forward facing step when L 1 > 5h (L 1 is the first rib width), regular structures of the flow occurs from the first cavity. The effect of wider first rib is highlighted by friction and pressure coefficients profiles and those of the turbulent kinetic energy. Its effect also appears in the Darcy friction factor. The viscous and pressure forces applied on the first rib and the 5th pitch roughness indicate that the pressure force is dominant. Darcy friction factor characterizing the flow and pressure drag coefficient evaluated at the 5th pitch roughness remains independent of Reynolds number, while the drag force applied on the first rib increases when Reynolds number augments.

Journal of Applied Fluid Mechanics, 2018

A plunging liquid jet is defined as a moving column of liquid passing through a gaseous headspace... more A plunging liquid jet is defined as a moving column of liquid passing through a gaseous headspace, air in our case, before impinging a free surface of receiving liquid pool. The mechanism of air entrainment due to plunging liquid jets is very complex and the complete mechanism of air entrainment is not fully understood so far. The present paper is an unsteady numerical simulation of air entrainment by water jet plunging, using the Volume Of Fluid (VOF) model. The piece wise linear interface construction algorithm (PLIC) for interface tracking is used, to describe the phase distributions of entirely immiscible air and liquid phases. The aim of this work is to investigate the performance and accuracy of the VOF method in predicting the initial impact between the descending jet and water free surface, air entrainment and the developing flow region under free surface. Three scale models based on geometric similarities (Froude number and dimensionless free jet length) are used for validation according to Chanson (2004) experience. The simulations show with accuracy, the air cavity formation steps, caused by the initial jet impact, its deep stretching under the pool free surface, until breakdown due to the shear created by a toroidal vortex. In terms of, air entrainment estimation, bubble dispersion and radial distribution of air volume fraction, large-scale models present a good agreement with the experience. However, for the smallest scale model, the results lead to suggest that air entrainment is governed by more parameters than the geometric similarities.

Heat and Mass Transfer, Jan 30, 2013

Large-Eddy-Simulation of turbulent heat transfer for water flow in rotating pipe is performed, fo... more Large-Eddy-Simulation of turbulent heat transfer for water flow in rotating pipe is performed, for various rotation ratios (0 B N B 14). The value of the Reynolds number, based on the bulk velocity and pipe diameter, is Re = 5,500. The aim of this study is to examine the effect of the rotating pipe on the turbulent heat transfer for water flow, as well as the reliability of the LES approach for predicting turbulent heat transfer in water flow. Some predictions for the case of non-rotating pipe are compared to the available results of literature for validation. To depict the influence of the rotation ratio on turbulent heat transfer, many statistical quantities are analyzed (distributions of mean temperature, rms of fluctuating temperature, turbulent heat fluxes, higher-order statistics). Some contours of instantaneous temperature fluctuations are examined. Keywords Large eddy simulation (LES) Á Rotating pipe flow Á Turbulent heat transfer Á Fully developed water flow Superscripts ð:Þ Statistically averaged (.) ? Normalized by u s , m and T s (.) 0 Fluctuation component

Advanced Powder Technology, Jul 1, 2015

The viscosity of nanofluid is one of the most critical parameter in nanofluids, which should be c... more The viscosity of nanofluid is one of the most critical parameter in nanofluids, which should be considered 30 by researches and need to be investigated thoroughly. This paper compares the several models of the 31 viscosity of turbulent forced convection of Al 2 O 3 nanofluid over a heated cavity in a horizontal duct. It 32 extends the previous work by the same authors by considering several viscosity models on 33 water-Al 2 O 3 nanofluids at small volume particle fraction. The governing equations are discretized by 34 the finite volume method based one point closure of a first order turbulence model. The effects of various 35 parameters such as Reynolds number (1 Á 10 4 6 Re 6 1 Á 10 5) and nanoparticles concentration (0 6 / 36 6 4%) on the heat transfer and flow characteristics are investigated and discussed. Five different viscosity 37 models (Pack and Cho, Maiga, Einstein, Brinkman and Batchlor) are tested. The results are analyzed 38 through the thermal and dynamical fields with a special interest to the skin friction coefficient and 39 Nusselt number evolutions. It was found average Nusselt number increases with the volume fraction 40 of nanoparticles for the whole range of Reynolds number. As a result, The Einstein, Brinkman and 41 Batchlor viscosity models show similar results and lesser friction and heat transfer. Pack and Cho viscos-42 ity model gives maximum friction and heat transfer. 43

Thermal Science, 2014

This study examines the performance of one point closure turbulence models in predicting of heat ... more This study examines the performance of one point closure turbulence models in predicting of heat and momentum transfer of impinging flows. The scope of this paper is limited to impinging jet on a moving wall and heat transfer. The impinging distance is fixed to 8 thickness of the nozzle (8e) for this study. Two parameters are considered: the jet exit Reynolds number (10000 £ Re £ 25000) and the jet-surface velocity ratio (0 £ R sj £ 4). The flow field structure at a given surface-to-jet velocity ratio is independent of the jet Reynolds number, a slight modification of the flow field is observed for low surface-to-jet velocity ratio (R sj < 0.25) whereas at higher ratios R sj > 0.25, the flow field is significantly modified. Good agreement with experimental results is obtained for surface-to-jet velocity ratio 0 £ R sj £ 2. The purpose of this paper is to consider the case of higher of surface-to-jet velocity R sj > 2. A further study of heat transfer shows that at the stagnation points the local heat transfer coefficient have a maximum value. The local Nusselt number at the impinging region tends to decrease significantly when R sj £ 1.5. The evolution of average Nusselt number is correlated according to the surface-to-jet velocity ratios for each Reynolds number.

Applied Thermal Engineering, Feb 1, 2017

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of heat transfer, Aug 19, 2013

The flow field and heat transfer of a plane impinging jet on a hot moving wall were investigated ... more The flow field and heat transfer of a plane impinging jet on a hot moving wall were investigated using one point closure turbulence model. Computations were carried out by means of a finite volume method. The evolutions of mean velocity components, vorticity, skin friction coefficient, Nusselt number and pressure coefficient are examined in this paper. Two parameters of this type of interaction are considered for a given impinging distance of 8 times the nozzle thickness (H/e ¼ 8): the jet-surface velocity ratio and the jet exit Reynolds number. The flow field structure at a given surface-to-jet velocity ratio is practically independent to the jet exit Reynolds number. A slight modification of the flow field is observed for weak surface-to-jet velocity ratios while the jet is strongly driven for higher velocity ratio. The present results satisfactorily compare to the experimental data available in the literature for R sj 1.The purpose of this paper is to investigate this phenomenon for higher R sj values (0 R sj 4). It follows that the variation of the mean skin friction and the Nusselt number can be correlated according to the surface-to-jet velocity ratios and the Reynolds numbers.

Renewable & Sustainable Energy Reviews, Sep 1, 2012

Nanofluids are considered to have great potential for heat transfer enhancement and are highly su... more Nanofluids are considered to have great potential for heat transfer enhancement and are highly suited to application in practical heat transfer processes. Recently, several important studies were carried out to understand and explain the causes of the enhancement or control of heat transfer using nanofluids. The main aim upon which the present work is based is to give a comprehensive review on the research progress on the natural convective heat transfer characteristics of nanofluids for both single-and twophase models. Both experimental and theoretical studies are reviewed for natural convection of nanofluids in different types of enclosures.

Chemical engineering research & design, Dec 1, 2017

This paper presents unsteady numerical simulation of air entrainment by water plunging jet using ... more This paper presents unsteady numerical simulation of air entrainment by water plunging jet using Volume of fluid model coupled to PLIC algorithm for phase interface reconstruction and Euler-Euler model considering continuous water phase and dispersed air phase. Plunging jet simulations aim to find out the ability of each model to reproduce air entrainment phenomenon. The investigation tackled the air plume depth, air entrainment rate and velocity profiles. Further simulations were performed to highlight the influence of the free jet length on the entrainment rate and plume development below the free surface. The results show good agreement with the available experimental data particularly velocity profiles in both radial and axial directions, plume shape and development along transient intervals. The initial impact is well reproduced referring to literature and bubbles penetration depth is comparable to the empirical correlations. It is noticed that further improvements are required for interfacial forces modeling in volume of fluid model to ensure good control of bubbles migration in the plume region. Entrainment rate discrepancies in Euler-Euler model are related to the lack of information about interface location due to averaging process; hence, an appropriate interface detection function is needed.