Eventos Anais de eventos
ENCIT 2018
Brazilian Congress of Thermal Sciences and Engineering
EXPERIMENTAL OBSERVATIONS OF THE BEHAVIOR OF SINGLE BUBBLES RISING IN CONFINED GEOMETRIES
Submission Author:
Fabio Ernesto Mancilla Ramos , PR
Co-Authors:
Thiago Sirino, Fabio Ernesto Mancilla Ramos, Rigoberto Morales
Presenter: Thiago Sirino
doi://10.26678/ABCM.ENCIT2018.CIT18-0654
Abstract
In this work, the effect of confinement on the dynamics of single bubbles rising in Newtonian fluids was investigated. A large column with a small gap was employed to perform the study for a gas–liquid system. The confinement parameter s was defined as the ratio of the bubble diameter (db = 2.5 mm) to the gap width (w = 3mm). Hence, the confinement ratio (s) was constant for all the measurements. Bubble size, shape and velocity were measured for different viscosities by means of a high-speed camera. It was found, that for the bubbles size, the bubbles are not distorted and prevails a spherical shape. In addition, the bubble vertical velocity was found to be constant for the different tested liquids. On the other hand, the vertical slip velocity was found to be approximately 50% less in comparison to single bubbles with the same equivalent diameter rising in non-confined geometries. Also, it was noted a decrement in the fluctuating velocities and increasing the viscosity the bubbles paths were modified. Therefore, their trajectories correspond to two different regimes: zigzag and rectilinear.
Keywords
bubbly flow, terminal velocity, bubble path
