FLOW STRUCTURE AND HEAT TRANSFER IN MULTIPLE IMPINGING JETS

Large eddy simulation of flow and heat transfer of multiple turbulent round jets in an in-line array impinging on a flat plate is conducted. To capture the interactions between the jets, the full geometry is meshed and used in the simulation of nine jets. The single jet Reynolds number based on the nozzle diameter of 13 mm, jet initial average velocity of 23.88 m/s, and the properties of air at room temperature is equal to 20,000. The computations of the mean vertical and horizontal components of the velocity vector, in selected planes, show very good agreement with experiments. The flow behavior of the jets agrees with experimental findings in terms of vortices surrounding the jets and the appearance of the asymmetry on, and close to, the flat impingement plane. The predicted mean surface Nusselt number on the flat heated plate shows also excellent agreement with experiments and a relative maximum between the jets in the region of the upwash fountain flow where the wall jets collide, not seen in the experiments, but captured by the numerics. It is believed that the present contribution provides an additional insight into the physics of important flow characteristics such as the individual paths of the central, side, and the corner jet streams. In particular, their effect on the nonhomogeneous cooling of the target wall, efficient in the corner regions and degraded in the central region, is also addressed.