Experiment on bubble characteristics of turbulent bubbly jets in pipe crossflow

Air-water bubbly jets in crossflow are commonly encountered in various practical applications such as artificial aeration in oceans and submarine pipelines. This study reveals the bubble characteristics for bubbly jets in pipe crossflow by conducting a series of physical experiments. It was found that the horizontal distance from nozzle exit to where bubble centerline touches the top pipe wall can be expressed as a function of the Reynolds and Weber numbers of the ambient pipe flow, and the Reynolds numbers of both the air and water phases of bubbly jets. The centerline gas void fraction and bubble size increase with distances after bubbles touch the top wall, mainly because bubbles are prone to gathering to the centerline to form larger bubbles. Afterwards, the (hori-zontal) bubble velocity decreases mainly due to the resistance force from the top wall. Good agreement has been achieved between horizontal bubble velocity and the 1/7th power law for water velocity in the pipe, and a correlation was proposed for predicting bubble rise velocity. Furthermore, turbulence characteristics of bubbles (e.g., root-mean-square of bubble fluctuating velocity, bubble turbulence intensity) were investigated for the bubbly jets.