气体注入位置对于液体交叉流中气泡形成的影响
Liquid flows incorporating small-size bubbles play a vital role in many industrial applications. Inthis work, an experimental investigation is conducted on bubble formation during gas injection froma microtube into the channel of a downward liquid cross flow. The tip of the air injector has beenlocated at the wall wall orifice and also at several locations from the wall to channel centerlinenozzle injection. The size, shape, and velocity of the bubbles along with liquid velocity field aremeasured using a shadow-particle image velocimetry/particle tracking velocimetry system. Theprocess of bubble formation for the wall orifice and the nozzle injection configurations is physicallyexplained. The effect of variation in water and air flow rates on the observed phenomena is alsoinvestigated by considering water average velocities of 0.46, 0.65, and 0.83 m/s and also air averagevelocities of 1.32, 1.97, 2.63, and 3.29 m/s. It was observed that shifting the air injector tip towardthe center of the channel resulted in the coalescence of some of the preliminary bubbles and theformation of larger bubbles termed secondary and multiple bubbles. Increase in air flow rate andreduction in water flow rate also intensify the rate of bubble coalescence. A correlation-based modelis also suggested to overcome the shortcoming of the available models in the literature which aredeveloped to only estimate the size of the preliminary bubbles. The model predicts the percent of thepreliminary, secondary, and multiple bubbles along with the average size of secondary and multiplebubbles as a function of nozzle position within a cross flow.