Drag coefficients for a settling sphere with microbubble drag reduction effects

Experiments are conducted to study the microbubble effects on drag reduction of settling particles in liquid. In this study, microbubbles are generated from Alka-Seltzer® powder coated on the surface of the particle. The particle Reynolds number range examined varies from 20,000 to 70,000. The reduction of drag force in terms of drag coefficient is found to decrease to about 15% with microbubble generation compared to that without microbubble generation.