Papers by Mohamed BRAIKIA
Numerical study of turbulent flows around a cubic obstacle blown from a variable geometry jets diffuser
Applied and Computational Mechanics, 2024
Journal of thermal engineering, Mar 22, 2024
This paper proposed to use the impinging jets mixing process to improve the quality of residentia... more This paper proposed to use the impinging jets mixing process to improve the quality of residential heating and air conditioning. The main objective is to meet the requirements of occupants in terms of thermal comfort and air quality by proposing an optimal solution for the thermal homogenization improvement in the rooms by changing of the diffusers geometry and their arrangement in the ventilation and airconditioning devices in blowing systems. This study involves both experimental and numerical studies of a three diffusers configurations composed of four peripheral jet with similar geometries and a central jet with a different geometry. All the configurations consist of four equidistant peripheral swirling jets, only the central jet that makes the difference between them. The configuration 1 includes a swirling central jet, on the other hand a circular central jet for the configuration 2 and finally a lobed central jet for configuration 3. The velocity and temperature distributions of the three configurations are investigated experimentally and numerically. Experimentally, the multifunction thermo-anemometer have been used to measure flow temperature and velocity. The dynamic and temperature features are more radially spread and get better homogeneity in configuration 3 and this is due to the energy distribution on the radial plane, which is relatively better than configuration 1 and configuration 2. The second part deals with numerical predictions of the dynamics and thermal fields of the three configurations considered. The study was realized using a RANS-based turbulence model. The numerical results are in reasonable agreement with our experiments for the three configurations. With this study, detailed information on the structure of the resulting flow is very useful to deepen the understanding of the physics of jet interaction and to validate turbulence models. The turbulence simulation is realized by the k-ω-SST model. This model gives a satisfactorily predicts the axial drop in velocity and temperature over the entire study range, demonstrating its ability to handle the interaction between swirling and lobe jets. Our results show that the geometry of the central diffuser is essential. This allows the axial velocity to decrease faster than configurations 1 and 2. This increases lateral diffusion, resulting in better homogenization.
HAL (Le Centre pour la Communication Scientifique Directe), Aug 24, 2015
The operation of cooling equipment and air ventilation can induce certain nuisances as usual blow... more The operation of cooling equipment and air ventilation can induce certain nuisances as usual blowing air conditioners, which can be so rude, that beyond a blowing speed threshold, the occupant can have headaches and would therefore be in a position to say the least "uncomfortable." to reduce blowing effects in diffusers, we seek to reduce the axial velocity of the air using attenuators devices implementing air nets deflection means to transform the axial component of those above radial component in the context of a building, the goal is both to reduce the size of the air treatment systems to achieve energy savings and to improve the thermal comfort of users, solving the problem of poor distribution of temperature and fresh air in a room. A series of experimental studies were conducted to determine the influence of various factors on the characteristics and multiple jet vortex structure to obtain a good mix and a net homogenization atmosphere in the premises and even in the...
Journal of Applied Fluid Mechanics, Sep 1, 2020
A large eddy simulation study was conducted to investigate the turbulent dynamic structure of a f... more A large eddy simulation study was conducted to investigate the turbulent dynamic structure of a fluid flow in two staggered tube configurations, one is composed of all circular cylinders and the second is composed of circular and square cylinders. The present LES, based on the wall-adapting local eddy viscosity model, has been conducted for ReD = 12,858, which match available experiments. The appropriate grid has been selected using the grid convergence index method so that the wall-normal coordinate y value is relevant for walls. Streamlines, turbulence kinetic energy contours, instantaneous vorticity contours computed indicate that wake patterns are more chaotic. In addition, flow coherent eddies within both configurations are identified via the Q-criterion. Based on the obtained findings, it can be stated that the model considered, in addition to being physically sound, demonstrated to be suitable for simulating the turbulent flow over circular and mixed staggered tube bundles with higher resolution.
Revue Nature et Technologie, Jun 1, 2015
Dans ce travail, nous présentons une étude expérimentale d'un jet turbulent à diffuseur muni de l... more Dans ce travail, nous présentons une étude expérimentale d'un jet turbulent à diffuseur muni de lobes, appliqué au confort d'hiver dans les locaux à usage d'habitation. L'objectif visé est l'amélioration de l'efficacité de la diffusion de l'air dans la zone d'occupation à moindre coût, par un moyen passif de contrôle de l'écoulement moteur de la ventilation. Les expériences ont été réalisées dans un local de dimensions 3,0m de longueur, 2,5m de largeur et 2,5m de hauteur. Ces dimensions permettent de réaliser au mieux des essais dans des conditions de jet vertical libre et chaud à forces de poussées défavorables. Le local a été isolé du milieu extérieur lors des expériences. En l'absence de contrôle des conditions thermiques au niveau des parois du local, la température ambiante n'est pas maintenue constante. L'écart de température jet/ambiance est néanmoins contrôlé par réajustement de la température de soufflage du jet. Il s'en suit la conservation du nombre d'Archimède du jet lors des essais. L'installation réalisée est composée d'un châssis sur lequel est fixé le dispositif de soufflage. Ce dernier comporte des diffuseurs de soufflage d'air chaud dirigés du haut vers le bas. Les températures et les vitesses de l'écoulement sont mesurées par un thermo-anémomètre multifonctionnel. La sonde est supportée par des tiges guidées verticalement et horizontalement pour balayer le maximum d'espace. Une étude comparative de la performance de différentes géométries de buses a été menée. Par l'analyse des profils de température axiale du jet pour 20 diamètres équivalent, la comparaison entre le diffuseur lobé à ouverture plus évasée et à faible hauteur et le diffuseur avec et sans tourbillonnement montre que le jet lobé dans des conditions de soufflage similaires assure mieux la stabilité des températures radiales tandis-que le jet tourbillonnaire à angle d'inclinaison 60° assure mieux l'épanouissement des températures radiales.
Numerical simulation of the interactions among multiple turbulent swirling jets mounted in unbalanced positions
Applied Mathematical Modelling, Mar 1, 2016
Abstract In this study, we numerically examined the interactions among multiple swirling jets mou... more Abstract In this study, we numerically examined the interactions among multiple swirling jets mounted in unbalanced positions. The formulation was based on the Reynolds average Navier–Stokes equations. In this study, turbulence was modeled using different turbulence models, i.e., k − ɛ standard, renormalization group, and Reynolds stress model (RSM) to make comparisons. This study was conducted under uniform thermal conditions for each configuration. The working fluid was the air, the Reynolds number was fixed at Re 0 = 3.1 0 4 , and the swirl number calculated from the measured velocity data was 1.33. We performed this study using the finite-volume FLUENT computational fluid dynamics solver. For most of the configurations analyzed, the results obtained using the RSM model agreed better with the experimental data compared with the standard turbulence model. The analysis of the flow features with moderate mesh refinement showed that the interactions between the swirling jets redistributed the temperature in the mixing zone as well as promoting the radial spread of the resultant jet. As expected, the development of the central jet improved thermal homogenization. More importantly, our results showed that changing the position between the central and peripheral jets greatly affected the quality of the thermal homogenization of the atmosphere.
Journal of Applied Fluid Mechanics, May 1, 2019
A combined experimental and computational study of a turbulent multiple jet from lobed diffusers ... more A combined experimental and computational study of a turbulent multiple jet from lobed diffusers is performed. The main interest of these multiple lobed jets is to come up with the best configuration that improves the thermal and dynamic homogenization in air diffusion units that can be used for ventilation, heating and air conditioning of residential premises. Herein, the configuration of a central lobed jet surrounded by six equidistant peripheral lobed jets has been investigated. On the experimental level, flow velocities and temperatures were measured by a multifunctional thermo-anemometer. In terms of numerical simulation, the conservation equations of mass, momentum and energy are solved while involving four turbulence models, viz., the k-ϵ model, the k-ω, the shear stress transport (SST) k-ω model and the Reynolds Stress Model (RSM). The findings are compared with thermo-anemometer measurements. It turns out that the SST k-ω model is most appropriate for predicting the average flow characteristics.
Revue Nature et Technologie, Jun 1, 2015
The aim of this paper is to study a bioclimatic house using solar energy which must guarantee the... more The aim of this paper is to study a bioclimatic house using solar energy which must guarantee the feeling of comfort for its occupants. It is located at Souidani west of Algiers (Algeria). This prototype is tested in order to obtain good energy efficiency to enable energy savings. The work presented in the Algerian climatic conditions, is a heating and cooling system of a house by reversible underfloor. The technique is used in order to ensure a comfortable climate throughout the year. We proceed to the numerical simulation of the thermal behavior of the indoor environments of the house considered, using the Fluent software. The results show that the reversible underfloor heaters all the rooms of the habitat, homogeneously, and also contributes to its cooling in summer. This system provides thermal comfort superior to other conventional systems.
HAL (Le Centre pour la Communication Scientifique Directe), Aug 27, 2007
Le conditionnement d'air des locaux de grands volumes ou grande hauteur pose le problème de l'hom... more Le conditionnement d'air des locaux de grands volumes ou grande hauteur pose le problème de l'homogénéité de températures et des masses d'air. Plusieurs expériences mettant en jeu la fusion de plusieurs jets sont étudiées pour répondre à ce type de problème. Ces jets sont nettement mieux homogénéises sous l'influence du tourbillonnement. L'objet de ce travail est la caractérisation dynamique du jet hélicoïdal confiné avec ou sans obstacle. Pour mener cette étude nous avons conçu et réalisé une installation expérimentale devant assurer de bonnes conditions de fonctionnement dans laquelle nous avons placé un souffleur comportant des ailettes orientables un fort taux de tourbillonnement. Le jet tourbillonnaire présente l'avantage de s'épanouir plus rapidement qu'un jet libre axisymétrique et permet une meilleure distribution d'air dans les locaux en assurant des conditions de confort appropriées. Une modélisation type (k-) est proposée pour mieux approcher cette caractérisation dynamique.
Le conditionnement d'air des locaux de grands volumes ou grande hauteur pose le problème de l'hom... more Le conditionnement d'air des locaux de grands volumes ou grande hauteur pose le problème de l'homogénéité de températures et des masses d'air. Plusieurs expériences mettant en jeu la fusion de plusieurs jets sont étudiées pour répondre à ce type de problème. Ces jets sont nettement mieux homogénéises sous l'influence du tourbillonnement. L'objet de ce travail est la caractérisation dynamique du jet hélicoïdal confiné avec ou sans obstacle. Pour mener cette étude nous avons conçu et réalisé une installation expérimentale devant assurer de bonnes conditions de fonctionnement dans laquelle nous avons placé un souffleur comportant des ailettes orientables un fort taux de tourbillonnement. Le jet tourbillonnaire présente l'avantage de s'épanouir plus rapidement qu'un jet libre axisymétrique et permet une meilleure distribution d'air dans les locaux en assurant des conditions de confort appropriées. Une modélisation type (k-) est proposée pour mieux approcher cette caractérisation dynamique.
Thermal Science, 2018
This article deals with the experimental investigation of multiple interacting jets, which may be... more This article deals with the experimental investigation of multiple interacting jets, which may be interested in many engineering applications such as design of a ventilation supply device. The main objective of this study is to achieve the best configuration for use in ventilation applications. To achieve this, several parameters have been considered and discussed such as the imbalance in temperature and diffuser orifices position with relative imbalance in flow rate between central and peripheral jets. Flow rate has been adjusted at Reynolds numbers, ranging from 104 to 3?104. The present study is carried out under uniform heat flux condition for each diffuser, and air is used as a working fluid. Experiences concerning the fusion of several jets show that the resulting jet is clearly more homogenized under the influence of the central swirling jet. Highlights of such an investigation show that, if the relative position of the central jet is higher, the radial spreading of the resul...
Journal of Applied Fluid Mechanics, 2016
In the present work, we are interested to the experimental and numerical study of the free turbul... more In the present work, we are interested to the experimental and numerical study of the free turbulent lobed jet, used in residential heating and air conditioning. The objective of our study is the improvement of the diffusion performance of the ventilation driving air flow, in the occupancy zone. The experiments have been conducted in a room where the dimensions enables a better execution in the conditions of free and hot vertical jet at unfavorable pushing forces. The installation contains a hot air blowing diffuser oriented from top to bottom. The velocities of the flow were measured by a multi-functional thermo-anemometer. The probe is supported by a stem guided vertically and horizontally in order to sweep a maximum space. Experimentally, we measured the axial and radial velocity field. The dynamics field analysis, show that in the potential core region, the dynamic profiles are more spread at the principal plane and this is due to the widening of the lobes' opening. While, in the transition zone and in the region where the flow is fully developed, these profiles are not influenced by the type of plane and then the jet will be similar to the circular one. Numerically, we used the commercial software Fluent. The obtained numerical results with turbulence method, (RNG k-ε), were in good accordance with the experimental one.
Numerical Study of the Influence of Combustion Models and Kinetic Schemes When Predicting the Diffusion Flames
Journal of Mechanics, 2012
ABSTRACTThis article aims to study numerically three-dimensional (3D) reactive turbulent flow in ... more ABSTRACTThis article aims to study numerically three-dimensional (3D) reactive turbulent flow in a combustion chamber of a gas turbine by solving a steady Reynolds-Averaged Navier-Stokes (RANS) )and energy equations. The Reynolds stress model (RSM) is coupled with the probability density function (PDF), laminar flamelet and Chemistry models to describe the turbulent flow and turbulence–chemistry interaction. Numerical computations are conducted to exhibit thermal and concentration behaviour under a quite number of factors, which influence the combustion process. Their influence are examined and compared favourably with available experimental results. Concentration of some radicals as O and OH are obtained assuming the partial-equilibrium assumption and using a PDF in terms of temperature. The 3D simulations demonstrate that the use of RSM, PDF and flamelet model allow simulating velocity and thermochemical fields.
Experimental and CFD-based study of the interaction of lobed multi-jet diffusers in unbalanced positions
Journal of the Brazilian Society of Mechanical Sciences and Engineering
Le mélange de jets a motivé de nombreuses études depuis plusieurs années en raison de son intérêt... more Le mélange de jets a motivé de nombreuses études depuis plusieurs années en raison de son intérêt théorique et de ses nombreuses applications industrielles. Les jets tourbillonnaires et turbulents interviennent dans une large variété de dispositifs industriels pour leur capacité à procurer de forts taux de mélange dans de multiples configurations : moteurs de fusées, moteurs diesel, torches à plasmas, brûleurs, dispersion de polluants, refroidissement, systèmes de ventilation et de climatisation. Différentes campagnes expérimentales ont conduit à l'optimisation de la géométrie des diffuseurs ce qui a permis de bien saisir l'importance des paramètres de contrôle comme l'inclinaison des ailettes, la présence du jet central, le nombre de jets adjacents, le nombre de tourbillonnement, le sens de rotation du jet central par rapport aux jets périphériques. Le but de cette étude est d'examiner l'influence du déséquilibre en position et en température du jet central par rapport aux jets adjacents, afin d'identifier la configuration la plus efficace en termes d'amélioration du mélange en sortie de l'écoulement résultant.
Thermal Science, 2012
The aim of this study is to examine different blowing configurations of multiple swirling jets fo... more The aim of this study is to examine different blowing configurations of multiple swirling jets for use it in terminal units of ventilation applications. The influence of several parameters such as the inclined vanes of diffuser and the sense of rotation of the single or multiple swirling jets, their number and their arrangement on the flow resulting dynamically and thermally is experimentally investigated. Flow rate was adjusted at Reynolds numbers, Re0, ranging from 104 to 30.103. The current study is carried out under uniform heat flux condition for each diffuser at Reynolds number of 30.103, the air being the working fluid. Experiences concerning the fusion of several jets show that the resulting jet is clearly more homogenized under swirling influence. The findings of this study show that the gap between the jets and their sense of rotation relative to the central jet, affects the quality of the homogenization of ambiance. Among the studied different configuration, the one which...
Assessment of energy and environmental performances of a bioclimatic dwelling in Algeria's North
Building Services Engineering Research and Technology
Bioclimatic architecture strategies and solar active systems contribute strongly to the reduction... more Bioclimatic architecture strategies and solar active systems contribute strongly to the reduction of building energy demand and achieving thermal comfort for its occupants over the whole year. This paper deals with the study of the energy performance improvement of a pilot bioclimatic house located in Algiers (Algeria). First, a series of experimental measures are conducted during cold period to show the effect of passive and active solar gains on the improvement of the indoor air temperature of the house. Then, a dynamic model of a solar heating system coupled with a bioclimatic house has been developed using TRNSYS software and validated with experimental data. The validated model has been used to establish the energy balance of the pilot bioclimatic house without solar heating system and to compare them to those of a conventional house. Finally, the improvement of the energy balance of the pilot bioclimatic house has been done by passive and active ways. The passive one includes ...
16th International Congress of Metrology, 2013
La compréhension des effets du confinement d'un multi jet tourbillonnaire, sur le taux d'entraîne... more La compréhension des effets du confinement d'un multi jet tourbillonnaire, sur le taux d'entraînement de l'air et sur la stratification de la température est très importante pour l'efficacité du processus de conditionnement d'air. Les jets impactant sont un moyen efficace d'optimisation des transferts thermiques entre un fluide et une structure solide. Ils sont, à ce titre, utilisés dans diverses applications industrielles telles que les processus de rafraichissement, de réchauffement ou de séchage. Une série d'études expérimentales a été menée pour déterminer l'influence de différents facteurs sur les caractéristiques et la structure du jet tourbillonnaire multiple permettant d'obtenir le mélange permettant l'homogénéisation de l'ambiance dans les locaux et de même dans les chambres de combustion.
Experimental and numerical investigation of thin liquid layers at curved solid edges
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Papers by Mohamed BRAIKIA