Effect of wetting conditions and flow rate on bubble formation at orifices submerged in water

Abstract

An experimental investigation has been carried out on the generation of bubbles due to the injection of a constant flow rate of air through an orifice submerged in water. Orifices of different radii drilled in horizontal plates of different materials, both hydrophilic and hydrophobic, have been used to cover a range of static contact angles (68° ≤ θ 0 ≤ 123°), and a wide range of volumetric gas flow rates (0.5 mm 3/s ≤ Q ≤ 1.33 × 10 4 mm 3/s) has been investigated. It is shown that data for different static contact angles and orifice radii can be approximately reduced to a single bubble volume/flow rate relationship when a properly scaled bubble volume at detachment is plotted versus a properly scaled volumetric gas flow rate. This data reduction permits an easy estimation of the bubble volume for any constant volumetric gas flow rate.