Sabra Habli

Étude numérique des conditions d'émission sur un écoulement de type jet axisymétrique turbulent

Resume Une methode aux differences finies est utilisee pour resoudre les equations regissant un ecoulement de type jet axisymetrique en regime turbulent. La discussion porte essentiellement sur la validite des deux modeles de turbulence les plus utilises (le modele k – e et le modele k – e – T ′2 ) pour decrire lecoulement dans les trois regions du jet, le modele algebrique est ensuite adopte pour determiner leffet des conditions dinjection sur les parametres de lecoulement. Nous montrons que linfluence des conditions a la sortie de la buse est importante seulement dans la region du jet. Dans la region de regime etabli, les conditions demission nont plus dinfluence sur lecoulement. Les deux modeles de turbulence utilises sont valables et donnent des resultats identiques dans la region du regime etabli en convection forcee, alors quen convection mixte, les resultats obtenus sont tres differents meme dans la zone auto-similaire, la fermeture de second ordre saverant plus efficace pour decrire les caracteristiques dun jet axisymetrique.

Étude numérique des conditions d'émission sur un écoulement de type jet plan turbulent isotherme ou chauffé

Abstract We intend to solve equations governing turbulent plane-vertical isotherm and non isotherm jets by taking into account inflow conditions at the exit of the nozzle. The analysis is focused on the influence of these conditions on this type of flow. Two cases are considered (uniform and parabolic velocity and temperature profiles). A finite difference scheme is developed to solve the governing equations. This numeric model allows us to show that the region of fully developed regime begins much nearer the nozzle for the turbulent case than for the laminar flow case. Indeed, the turbulence increases the mixing between the incoming gas from the nozzle and the ambient fluid, and consequently the size of the potential core zone decreases. The results are compared to other works introducing mathematical variables based on the energy conservation for the case of the mixed convection and the momentum conservation for the forced convection, which allows the validation of our results.

Flow Field Measurement in a Crossflowing Elevated Jet

Structural features resulting from the interaction of a turbulent round jet issuing transversely into a uniform stream are described with the help of flow visualization and the PIV technique. The jet exits from a rigidly mounted pipe projecting at a distance from the floor of a tunnel. The aim of the present work is to investigate the flow structure in the near-field jet-pipe exit. Jet-to-crossflow velocity ratios from 0.375 to 3 were revealed at Reynolds numbers from 1660 to 6330. Flows in the vertical symmetry plane and horizontal plane across the jet-wake, jet-exit, and pipe-wake regions are investigated. The measured velocity fields present quantitative characteristics of the streamlines, vortices, and topological features of the flow structures. In particular, the origin and formation of the vortices in the wake are described and shown to be fundamentally different from the well-known phenomenon of vortex shedding from solid bluff bodies.