Heat Transfer—Asian Research, 00 (00), 2014 Numerical Study of Heat Transfer and Separated Flow Over Rectangular Obstacle in Jet Kabache Malika and Mataoui Amina 1 Department of Physics, Faculty of science, University M’Hamed Bouguerra Boumerdes, Algeria 2 Theoretical and Applied Laboratory of Fluid Mechanics, University of science and Technology Houari Boumedienne - USTHB, Algiers, Algeria This paper is about a separated reattaching fow over a hot rectangular ob- stacle. Two types of incoming fow are examined in order to show the infuence of the external zone of the fow on the reattachment process. It comes about due to a wall jet and a boundary layer. The inner region of these two fows is similar, but their external regions are extremely different. The separating and reattaching fow phenomena are of particular interest in engineering felds such as for an aeronautical application. Wall jet fow over an obstacle occurs in many engineering applications such as environmental discharges, heat exchangers, fuid injection systems, cooling of combustion chamber wall in a gas turbine, automobile design, and others. In elec- tronics cooling, the prediction of the Nusselt number distribution along the obstacles is necessary before the design of the apparatus. For a heated obstacle at a constant temperature, T = 350 K and an aspect ratio of 10 (L = 10 H), the problem parame- ters are: (a) jet exit Reynolds number (Re) ranged from 1000 to 50000, (b) incoming fow confguration (boundary layer and wall jet). The ratio between the thickness of the nozzle (b) to the obstacle height (H) are examined simultaneously. The formula- tion is based on the SST k– turbulence model. The results show that the increasing of nozzle thickness; enhances the heat transfer and considerably modifes the stag- nation point location. The highest incoming fow momentum provides the greatest values of average Nusselt number. Such as the boundary layer case in comparison with the wall jet cases. The average Nusselt number is correlated according to prob- lem parameters ( Nu obstacle = f (Re, b)). C⃝ 2014 Wiley Periodicals, Inc. Heat Trans Asian Res, 00(00): 1–21, 2014; Published online in Wiley Online Library (wileyon- linelibrary.com/journal/htj). DOI 10.1002/htj.21174 Key words: wall jet, heat transfer, turbulence, obstacle, boundary layer, shear fow. 1. Introduction Separated and reattaching phenomenon in a turbulent fow over a rectangular obstacle is in- vestigated numerically in this study. However, the elongated obstacle behaves as a forward-backward facing step pair (Addad and colleagues [1]). Separating and reattaching fow phenomena are of par- ticular interest in engineering felds. Turbulent fow over a surface-mounted obstacle is an important C⃝ 2014 Wiley Periodicals, Inc. 1