Contribution à l'étude de l'interaction d'un jet axisymétrique avec une cavité cylindrique chauffée

111 p. : ill. ; 30 cmLe présent travail est une contribution à l'étude d'une interaction symétrique d'un jet axisymétrique turbulent, issu d'une longue conduite à l'intérieur d'une cavité cylindrique chauffée à fond fermé. L'interaction jet-cavité est analysée numériquement à l'aide de deux modèles statistiques de turbulence de fermeture en un point RANS: - Le modèle k- réalisable du premier ordre - Le modèle des tensions de Reynolds (Reynolds Stress Model-RSM) du second ordre. La résolution numérique des équations du mouvement et celle de l'énergie sont effectuées par le code CFD ANSYS (Fluent14) basé sur une méthode des volumes finis et qui nécessite l'usage du code Gambit 6.3 pour générer la géométrie, le maillage et les conditions aux limites du problème. Les champs dynamique et thermique ont été investigués pour différent distances d'impact du jet avec le fond de la cavité, de 2d à 12d (d étant le diamètre du jet) et pour une gamme du nombre de Reynolds Re variant de 2 104 à 5 104 correspondant à une turbulence pleinement développée. Une validation a été effectuée avec des travaux expérimentaux disponibles dans la littérature. Les résultats obtenus ont permis de confirmer les observations suivantes : " L'écoulement dans la cavité se compose de trois zones principales : a. Une zone de jet libre. b. Une zone d'interaction du jet principale avec l'écoulement de retour. c. Une zone stagnante située au fond de la cavité qui forme un tourbillon toroïdale. " L'interaction d'un jet rond avec une cavité cylindrique génère un écoulement stable (non oscillatoire) parfaitement symétrique. " Le chauffage n'a pas une influence sur la structure globale d'écoulement (Problème de convection forcée). " Cette étude nous a permis de proposer des corrélations en fonction du nombre de Reynolds Re et de la distance d'impact Lf, pour nombre du Nusselt au point d'arrêté Nu0 (Nu0=f(Re,Lf)) et le nombre de Nusselt moyen Nuavr (Nuavr=f(Re,Lf

Steady interaction of a turbulent plane jet with a rectangular heated cavity

Turbulent heat transfer between a confined jet flowing in a hot rectangular cavity is studied numerically by finite volume method using the k-w SST one point closure turbulence model. The location of the jet inside the cavity is chosen so that the flow is in the non-oscillation regime. The flow structure is described for different jet-to-bottom-wall distances. A parametrical study was conducted to identify the influence of the jet exit location and the Reynolds number on the heat transfer coefficient. The parameters of this study are: the jet exit Reynolds number (Re, 1560< Re <33333), the temperature difference between the cavity heated wall and the jet exit (DT=60°C) and the jet location inside the cavity (Lf, 2≤ Lf≤ 10 and Lh 2.5<Lh≤10). The Nusselt number increased and attained its maximum value at the stagnation points and then decreased. The flow structure is found in good agreement with the available experimental data. The maximum local heat transfer between the cavity walls and the flow occurs at the potential core end. The ratio between the stagnation point Nusselt numbers of the cavity bottom (NuB0) to the maximum Nusselt number on the lateral cavity wall (NuLmax) decreased with the Reynolds number for all considered impinging distances. For a given lateral confinement, the stagnation Nusselt number of the asymmetrical interaction Lh≠10 is almost equal to that of the symmetrical interaction Lh=10

Turbulent heat transfer for impinging jet flowing inside a cylindrical hot cavity

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 2·104 to 105 and the normalized impinging distance to the cavity bottom and the jet exit Lf, 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(Lf, Re

Turbulent heat transfer for impinging jet flowing inside a cylindrical hot cavity

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 2x104 to 105and the normalized impinging distance to the cavity bottom and the jet exit Lf, 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(Lf,Re)