A Laboratory Study of Penetration Depth and Distribution of Bubbles Formed by a Translating Vertical Fluid Jet

Air entrainment in liquids via a fluid jet, is a complex phenomenon that has important applications in industry and the environment. The impact of a vertical laminar water jet translating over the quiescent pool of water at constant velocity was studied empirically, and the penetration depth as well as distribution of the bubbles formed by this jet was measured for both fresh and sea water with two different optical methods. This experiment was conducted at different flow rates (corresponding to different vertical velocities). In each case, the jet was moved at different horizontal velocities relative to the pool surface. As the jet started its horizontal translation, air began entering the pool from the bottom of the point of impact. Bubbles penetration depth was measured through a high-speed imaging technique, and pulse shadowgraphy was used for measuring the bubbles distribution. Increasing the vertical velocity of the jet while simultaneously decreasing the horizontal velocity of the same led to increased bubble penetration depths, and similar results were obtained for fresh water and sea water. This result was obtained in spite of the fact that the number and size of the bubbles formed in sea water were dramatically different from those formed in fresh water. Moreover, the significant role of buoyant forces in the distribution of the bubbles was obvious. The penetration depth and distribution of the bubbles were measured and reported for various jets with different diameters at different vertical and horizontal velocities.