The Effect of Orifice Geometry on Bubble Size

The Effect of Orifice Geometry on Bubble Size 

Krishnamurthi, Kumar, and Datta (K7) employed a circular orifice of arbitrarily chosen dimensions as the standard, and constructed two sets of noncircular orifices having either the perimeter or the area equal to that of the standard orifice. The configurations chosen were an equilateral triangle, a square, and a rectangle. The system used by these authors was air-water, and their studies were confined to extremely small flow rates ( 0.5 cm3/sec). Their results indicate that noncircular orifices do not utilize their entire perimeter for bubble formation, and, for equi-sided orifices at low frequencies of formation, the bubble is formed as if from a circle inscribed in the noncircular orifice. In this range, the perimeter and the area are important in determining the final bubble size. 

Further investigations by the above authors (K5), using an air-glycerine solution system (density = 1.22 g/ml, viscosity = 76.2cp and surface tension = 61.8 dyn/cm) confirmed the above conclusions for highly viscous liquids also. The authors have further correlated their results by the empirical relation (K8)  

R = the ratio of the area of the noncircular orifice to that of the inscribed circle. 

Ramakrishnan, Kumar, and Kuloor (Rl) have extended the investigations of Krishnamurthi et al. (K5, K7, K8) to more geometries, much higher flow rates (up to 100 cm3/sec), liquids of still higher viscosity, and to completely constant flow conditions. 

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VIII. The Effect of Orifice Geometry on Bubble Size. 321... 

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