Vortex flow affected by disk rotation in an air jet impinging onto a confined heated horizontal disk

Abstract

An experiment combining flow visualization and temperature measurement is carried out to explore the effects of disk rotation on the vortex flows induced in a round jet of air impinging onto a heated horizontal disk confined in a vertical cylindrical chamber. The experiment is conducted for the jet-disk separation distance at 20.0 mm and 40.0 mm. The jet flow rate is varied from 0 to 5.4 slpm (standard liter per minute) for the jet Reynolds number Rej ranging from 0 to 730. The disk rotation speed varies from 0 to 35.0 rpm for the rotational Reynolds number ranging from 0 to 2725. The temperature difference between the disk and the air injected into the chamber is varied from 0 to 25.0°C for the Rayleigh number ranging from 0 to 150,325. The data from the present study for the ratio of jet disk-disk separation distance to the jet diameter (denoted as HDj) are compared. The results indicate that at the disk rotation rate Ω ≥ 10.0 rpm the secondary inertia-driven roll is completely wiped out for HDj = 4. For HDj = 2 at a higher disk rotation rate of Ω ≥ 20.0 rpm, the buoyancy-driven roll can be substantially squeezed by the disk rotation to become smaller and weaker. Meanwhile, the primary inertia-driven roll is stretched out to become slender and weaker. But for HDj = 4, due to a stronger buoyancy-driven vortex flow at a higher jet-disk separation distance, a higher Ω is needed to stabilize the buoyancy-driven roll.