On dynamical and thermal behavior of an impinging jet involving a chevron nozzle

A three-dimensional turbulent round jet impinging on a heated flat plate is investigated numerically. The effects of the nozzle geometry and nozzle-to-plate distance on the dynamical and thermal behavior are explored. A round nozzle and nozzles fitted with either 4 or 6 chevrons are considered. Three nozzle-to-plate distances are studied: H/D = 2, 4, and 6. The Reynolds number equals 5000. The results show that the chevrons improve the heat transfer near the area of stagnation. This improvement can reach up to 110 % in specific regions. It is also found that the wall heat flux is appreciably non-uniform for the small distance H/D = 2. Degraded heat transfer is recorded between the plate and the fluid in narrow radial passages of fluid downstream of the stagnation point for the small value of H/D. They turn out to be quasi-potential flow streams, along the target wall and facing the chevron apices, characterized by high convective velocities and nearly no turbulence. Increasing the distance to H/D = 6 yields a somewhat axisymmetric thermal behavior. Effects on Nusselt number values averaged over circular surfaces centered on the stagnation point and of variable radius on the target wall are highlighted.