Experimental study of bubble column hydrodynamics

This paper is devoted to the experimental study of bubble column hydrodynamics. A bubble column flow was performed in a vertical rectangular channel, at liquid velocities of approximately 0.10 m/ s and high void fractions. First, void fraction, bubble size and bubble velocity were measured with a dual optical probe. Liquid velocities were obtained using hot film velocimetry. Some characteristics of homogeneous bubbly flow were clearly highlighted. Secondly, mean and fluctuating wall shear stress measurements were made using the electrochemical method. The presence of bubbles is known to increase wall-friction. This increase was found to be much more important than that at the higher values of liquid velocity usually investigated in fluid mechanics. Space–time analysis was used to calculate integral length scale, coherence time and convection velocity. With these techniques, wall-turbulence features were investigated, namely the non-validity of the logarithmic law, very high turbulent kinetic energy and very intense turbulent dissipation.