Experimental study of air entrainment by inclined plunging liquid jets within the transition entrainment regime utilizing microalgal slurry

A fundamental understanding of air entrainment is critical for the design and optimization of systems that rely on aeration induced by plunging jets. This study investigates the air entrainment arising from inclined plunging liquid jets, focusing on the transition entrainment regime for which limited research and data are available. Experiments conducted involved varying the jet angle, fall height, velocity, and liquid surface tension. Algal slurry was utilized and cetyltrimethylammonium bromide surfactant was added to adjust the liquid surface tension. Air entrainment was measured via the replacement method with low overall measurement uncertainty. Results revealed that the entrainment ratio in the transition entrainment regime can be expressed as a power law function of the jet angle, the dimensionless fall height, and the Weber number. A multiple linear regression model was developed with ± 10.4 % accuracy and verified against experimental data from the literature, demonstrating satisfactory performance.