Numerical investigation of thermal and aerodynamic behavior in annular jet impingement on a curved surface

Numerical simulations were performed to investigate the thermal and aerodynamic characteristics of an annular jet impinging on a concave surface using the Realizable k-ε model. The study examined the significance of the blockage ratio (BR) from 0.3 to 0.7 and the jet exit Reynolds number (Re) from 5000 to 35000. The investigation uses an annular jet with a 10 mm outer diameter impinging on a concave surface with 150 mm radii. Three specific dimensionless distances from the nozzle exit to the target surface (z/do) were considered: z/do = 0.5 (initial merging zone), z/do = 3 (intermediate merging zone), and z/do = 6 (fully merged zone). Furthermore, the annular jet’s performance was compared to that of a conventional circular jet under analogous conditions. At small separation distances, a pair of counter-rotating vortices formed downstream of the jet outlet, inducing a reverse flow that extended to the heated surface. Vortices and flow reversals were also identified at intermediate separation distances. At large separation distances, the flow reattached to the domain axis, resembling a circular jet. The local Nusselt number (Nu) increases as the Reynolds number increases and the blockage ratio decreases. With increasing BR, the difference between the primary and secondary Nu peaks reduces. Additionally, the average Nu and turbulent kinetic energy increase with an increase in Re.