Experimental study of Dumitrescu–Taylor bubble wall shear stress in stagnant and counter-current vertical flow

Abstract

From the literature, there is few experimental data on the Dumitrescu–Taylor bubble wall shear stress in stagnant and flowing liquid in vertical tube Thus, in this study, experimental results are presented on the wall shear stress recorded around an individual Dumitrescu–Taylor bubble. The experiments were carried out in a counter-current laminar downward flow in vertical tube with an inner diameter of 0.0102 m. With the experimental device, the bubble can have two extreme travel velocities; from a low bubble velocity in counter-current flow to a maximum velocity in stagnant flow. The real picture recording signals of wall shear stress are presented over a wide range of an axial position below the nose of the bubble and for the two extreme bubble velocity. The results show clearly the sensitivity of the velocity effect on the wall shear stress profiles. The wall shear stress appears to decrease as the bubble velocity increases in counter-current flow. According to the shear stress profiles results, valuable information on the liquid film flow regime is provided with a reverse flow behind the bubble’s bottom. The change of the flow direction, the length of the parietal vortices and the distance of the flow stabilization behind the bottom of the bubble has been characterized.