Coanda Effect on Bubble Characteristics in a Bubbling Jet Rising Near the Side Wall of a Cylindrical Vessel.

Experimental investigation was carried out on the behavior of an air–water bubbling jet generated vertically upward by air injection through a single-hole nozzle placed near the side wall of a cylindrical vessel. The bubbling jet was pulled towards the side wall, attached to it at a certain vertical distance from the nozzle top, and afterwards rose along it. Such a phenomenon was caused through the Coanda effect. The vertical distance from the nozzle top to the attachment position was defined as the attachment length. This length was closely associated with the gas flow rate and the horizontal distance between the nozzle top and the side wall. The inner diameter of the nozzle, however, exerted a negligibly small effect on the attachment length. Bubble characteristics represented by bubble frequency, gas holdup, mean bubble rising velocity and mean bubble chord length were measured with a two-needle electroresistivity probe. The horizontal distributions of the bubble frequency and gas holdup were similar in the vertical region above the attachment position.