Abstract
The shape, rise velocity and drag coefficient of a single drop with a diameter from 1.9 to 10.5 mm rising in Newtonian fluids are discussed, where the drops Reynolds numbers are from 0.002 to 1,000. The deformation of drops and its effect on the terminal velocities and drag coefficients are considered. The results for terminal velocity and drag coefficient are compared with the previous correlations of both bubble and drop motions in Newtonian system. We obtained the frequency spectrums on the lateral oscillation of the drops with different diameters by using Fourier analysis to investigate the effect of the resonance frequency and the vortex trail on the oscillation of the drops. The results show that the maximal response frequencies of the drops are shifted to the low-frequency part when the drop diameter increases. Particle image velocimetry was used to quantify the liquid velocity flow field around the drops, and the effect of the wake behind the drop may cause pulsating–pressure distribution over the surface of the drop, which leads to the change of the maximal frequencies on the response oscillation.
