Flow Properties of Microbubble/Polyethylene Glycol Mixtures Passing through Orifices and Slits

Flows of microbubble/liquid mixtures have been extensively studied in both theoretical and applied research, and important results, such as drag reduction effects, have been reported. However, the majority of researchers have focused on only mixtures of microbubbles and water. Studies on microbubble mixtures in complex liquids, for example, for surfactant solutions and polymer solutions, are limited. The present study considers the flow of microbubble mixtures in a dilute polymer solution. In the present research, microbubbles (particle size: 20 mu m) are suspended in either water or a dilute solution of polyethylene glycol. The liquids and suspensions were passed through various sizes of orifices (200 mu m to 1.0 mm) and slits (397 mu m and 596 mu m), pressure drops were measured, and elongational stresses were estimated. Pressure drops of the polyethylene glycol solution were less than those of water, and the measured pressure drops of both microbubble mixtures were greater than those of the polyethylene glycol solution. As a result, polymer chains in the polyethylene glycol solution are considered to be laden with microbubbles, and this effect is seen in the corresponding elongational stress estimates.