Drag Coefficients of Bubbles (1st Report, Drag Coefficients of a Single Bubble in a Stagnant Liquid

Abstract

A drag coefficient, CD, of a single bubble in an infinite stagnant liquid is the basis for developing a constitutive equation of interfacial drag force. Up to the present, the interfacial drag force has been, however, often evaluated using CD of a rigid particle, which is valid only for a spherical bubble in a contaminated liquid. Hence, a simple but reliable constitutive equation of CD was proposed in the present study. The proposed CD consists of three equations, each of which corresponds to pure, slightly contaminated and contaminated systems. Terminal rising velocities of bubbles were calculated using the proposed CD, and compared with the measured data under the conditions of 10-2 < Eo < 103, 10-14 < M< 107 and 10-3 < Re < 105 where Eo, M and Re are Eütvüs, Morton and Reynolds numbers. As a result, it was confirmed that the proposed CD gives better predictions than available constitutive equations. © 1995, The Japan Society of Mechanical Engineers. All rights reserved.