Ali El shrif | Almergueb (original) (raw)

Papers by Ali El shrif

مجلة الجامعة الأسمرية: العلوم التطبيقية

To enhance thermal management for micro-electric devices, nanofluids become promising working flu... more To enhance thermal management for micro-electric devices, nanofluids become promising working fluids for many thermo-fluid applications. Thermal characteristics of the working fluids can be improved by nano particles additives dispersed in the working fluid such as Cu-nanoparticles in water. The nanoparticle additives manage to alter thermal and dynamic properties of the working fluids such as the dynamic viscosity which plays an important role in specifying thermal and dynamic behaviour of the working media. In order to understand the effect of modifying the dynamic viscosity of the working media, the effective value of this property must be determined. The molecular dynamic (MD) simulation has been used to estimate the Cu/water nanofluid dynamic viscosity at partial volume fractions of φ=0.0125 % and φ= 0.02478 %, and at working temperatures 293 K, 303 K, 313 K, 323 K and 333 K. The used spherical shape nanoparticles are made up of numbers of 0.3-nm-diameter Cu-atoms. The MD simu...

Deux strategies de controle ont ete successivement mises en oeuvre pour reduire la trainee et l&#... more Deux strategies de controle ont ete successivement mises en oeuvre pour reduire la trainee et l'energie cinetique turbulente d'un canal plan en regime turbulent (Re[tau]=180) par soufflage/aspiration aux parois. L'objectif principal etait de prouver qu'une simulation aux grandes echelles (LES) pouvait etre utilisee de maniere pertinente comme modele reduit des equations de Navier-Stokes et ainsi diminuer fortement les couts numeriques. Une approche heuristique dite de controle par opposition a d'abord ete employee. Les resultats montrent que l'efficacite energetique est maximale pour une position du plan de detection differente de celle qui correspond au maximum de reduction de trainee. Par ailleurs, nos resultats confirment que la reduction de trainee diminue avec l'augmentation du nombre de Reynolds. Par la suite, une procedure de controle optimal a ete utilisee en considerant differentes fonctionnelles objectif (trainee, energie cinetique au temps term...

aaafasso.fr

Abstract: In this study, we are interested in reducing the drag force on the upper and lower wall... more Abstract: In this study, we are interested in reducing the drag force on the upper and lower walls of a plane turbulent channel flow, using an active flow control scheme. Large eddy simulations (LES) and optimal control theory are used to determine control laws that ...

18ème Congrès Français de Mécanique …, 2007

18 ?me Congr?s Fran?ais de M?canique Grenoble, 27-31 ao?t 2007 Contr?le actif par Simulation aux ... more 18 ?me Congr?s Fran?ais de M?canique Grenoble, 27-31 ao?t 2007 Contr?le actif par Simulation aux Grandes Echelles d?un ?coulement de canal turbulent Ali El Shrif?,Laurent Cordier? & Salaheddine Skali Lami? ? LEMTA ...

univ-ubs.fr, 2011

Dans cette étude, la théorie du contrôle optimal est utilisée pour minimiser la traınée totale mo... more Dans cette étude, la théorie du contrôle optimal est utilisée pour minimiser la traınée totale moyenne sur les parois supérieure et inférieure d'un écoulement de canal turbulent `a Reτ = 100 et Reτ = 180. Le contrôle est réalisé par une procédure de soufflage/aspiration `a débit nul. Une ...

Proceeding of Seventh International Symposium on Turbulence and Shear Flow Phenomena

An optimal control approach is implemented using Large Eddy Simulations as a reduced-order model.... more An optimal control approach is implemented using Large Eddy Simulations as a reduced-order model. The application of optimal control is targeting the drag reduction on the channel upper and lower walls. Three different cost functional (drag, terminal turbulent kinetic energy, mean turbulent kinetic energy) have been tested and the strategy was applied to flows going from = 100 to = 360. Wall transpiration (unsteady blowing/suction) with zero net mass flux is used as control. At = 100, control managed to fully relaminarize the flow (drag reduction of about 57 %) by considering as cost functional the terminal kinetic energy. For this same cost functional, an important drag reduction of about 50 % is still obtained at = 180 but without reaching the relaminarization. Our results show that to minimize the flow drag, it is more efficient to consider the kinetic energy as cost functional than directly the drag. Lastly, it is essential for the convergence of the minimization that the optimality system is solved on a sufficiently long time horizon.

In this study the instability problem of a modified<br> Taylor-Couette flow between two ver... more In this study the instability problem of a modified<br> Taylor-Couette flow between two vertical coaxial cylinders of radius<br> R1, R2 is considered. The modification is based on the wavy shape of<br> the inner cylinder surface, where inner cylinders with different<br> surface amplitude and wavelength are used. The study aims to<br> discover the effect of the inner surface geometry on the instability<br> phenomenon that undergoes Taylor-Couette flow. The study reveals<br> that the transition processes depends strongly on the amplitude and<br> wavelength of the inner cylinder surface and resulting in flow<br> instabilities that are strongly different from that encountered in the<br> case of the classical Taylor-Couette flow.

مجلة الجامعة الأسمرية: العلوم التطبيقية

To enhance thermal management for micro-electric devices, nanofluids become promising working flu... more To enhance thermal management for micro-electric devices, nanofluids become promising working fluids for many thermo-fluid applications. Thermal characteristics of the working fluids can be improved by nano particles additives dispersed in the working fluid such as Cu-nanoparticles in water. The nanoparticle additives manage to alter thermal and dynamic properties of the working fluids such as the dynamic viscosity which plays an important role in specifying thermal and dynamic behaviour of the working media. In order to understand the effect of modifying the dynamic viscosity of the working media, the effective value of this property must be determined. The molecular dynamic (MD) simulation has been used to estimate the Cu/water nanofluid dynamic viscosity at partial volume fractions of φ=0.0125 % and φ= 0.02478 %, and at working temperatures 293 K, 303 K, 313 K, 323 K and 333 K. The used spherical shape nanoparticles are made up of numbers of 0.3-nm-diameter Cu-atoms. The MD simu...

Deux strategies de controle ont ete successivement mises en oeuvre pour reduire la trainee et l&#... more Deux strategies de controle ont ete successivement mises en oeuvre pour reduire la trainee et l'energie cinetique turbulente d'un canal plan en regime turbulent (Re[tau]=180) par soufflage/aspiration aux parois. L'objectif principal etait de prouver qu'une simulation aux grandes echelles (LES) pouvait etre utilisee de maniere pertinente comme modele reduit des equations de Navier-Stokes et ainsi diminuer fortement les couts numeriques. Une approche heuristique dite de controle par opposition a d'abord ete employee. Les resultats montrent que l'efficacite energetique est maximale pour une position du plan de detection differente de celle qui correspond au maximum de reduction de trainee. Par ailleurs, nos resultats confirment que la reduction de trainee diminue avec l'augmentation du nombre de Reynolds. Par la suite, une procedure de controle optimal a ete utilisee en considerant differentes fonctionnelles objectif (trainee, energie cinetique au temps term...

aaafasso.fr

Abstract: In this study, we are interested in reducing the drag force on the upper and lower wall... more Abstract: In this study, we are interested in reducing the drag force on the upper and lower walls of a plane turbulent channel flow, using an active flow control scheme. Large eddy simulations (LES) and optimal control theory are used to determine control laws that ...

18ème Congrès Français de Mécanique …, 2007

18 ?me Congr?s Fran?ais de M?canique Grenoble, 27-31 ao?t 2007 Contr?le actif par Simulation aux ... more 18 ?me Congr?s Fran?ais de M?canique Grenoble, 27-31 ao?t 2007 Contr?le actif par Simulation aux Grandes Echelles d?un ?coulement de canal turbulent Ali El Shrif?,Laurent Cordier? & Salaheddine Skali Lami? ? LEMTA ...

univ-ubs.fr, 2011

Dans cette étude, la théorie du contrôle optimal est utilisée pour minimiser la traınée totale mo... more Dans cette étude, la théorie du contrôle optimal est utilisée pour minimiser la traınée totale moyenne sur les parois supérieure et inférieure d'un écoulement de canal turbulent `a Reτ = 100 et Reτ = 180. Le contrôle est réalisé par une procédure de soufflage/aspiration `a débit nul. Une ...

Proceeding of Seventh International Symposium on Turbulence and Shear Flow Phenomena

An optimal control approach is implemented using Large Eddy Simulations as a reduced-order model.... more An optimal control approach is implemented using Large Eddy Simulations as a reduced-order model. The application of optimal control is targeting the drag reduction on the channel upper and lower walls. Three different cost functional (drag, terminal turbulent kinetic energy, mean turbulent kinetic energy) have been tested and the strategy was applied to flows going from = 100 to = 360. Wall transpiration (unsteady blowing/suction) with zero net mass flux is used as control. At = 100, control managed to fully relaminarize the flow (drag reduction of about 57 %) by considering as cost functional the terminal kinetic energy. For this same cost functional, an important drag reduction of about 50 % is still obtained at = 180 but without reaching the relaminarization. Our results show that to minimize the flow drag, it is more efficient to consider the kinetic energy as cost functional than directly the drag. Lastly, it is essential for the convergence of the minimization that the optimality system is solved on a sufficiently long time horizon.

In this study the instability problem of a modified<br> Taylor-Couette flow between two ver... more In this study the instability problem of a modified<br> Taylor-Couette flow between two vertical coaxial cylinders of radius<br> R1, R2 is considered. The modification is based on the wavy shape of<br> the inner cylinder surface, where inner cylinders with different<br> surface amplitude and wavelength are used. The study aims to<br> discover the effect of the inner surface geometry on the instability<br> phenomenon that undergoes Taylor-Couette flow. The study reveals<br> that the transition processes depends strongly on the amplitude and<br> wavelength of the inner cylinder surface and resulting in flow<br> instabilities that are strongly different from that encountered in the<br> case of the classical Taylor-Couette flow.