Experimental Study of Flow Structure in Vertical Slug Flow
1995; Elsevier BV; Linguagem: Inglês
10.1016/b978-0-444-81811-9.50014-7
AutoresJ.D. DeJesus, W. Ahmad, Masahiro Kawaji,
Tópico(s)Fluid Dynamics and Heat Transfer
ResumoNon-intrusive flow visualization using photochromic dye activation has been conducted to obtain twodimensional velocity profiles around Taylor bubbles rising in stagnant kerosene in a vertical 2.54 cm I.D. pipe. The results show that flow reversal in the liquid occurs at the nose of the Taylor bubble. From the nose, the liquid film accelerates downwards as the velocity profile becomes characteristic of developing falling film flow. At the tail, the liquid film penetrates into the wake creating vortices of different sizes, which produce a substantially greater range of velocities. However, within one to two tube diameters below the tail of the Taylor bubble, these vortices rapidly decay and the liquid near the wall returns to essentially a stagnant initial state. Contrary to intuition, the film penetration distance in the wake region is not proportional to film velocity, and therefore, bubble length. Although the flow of the liquid film surrounding the cylindrical portion of the Taylor bubble is one-dimensional, a two-dimensional flow analysis reveals that the liquid flow near the nose and in the wake is highly two-dimensional and the assumption of one-dimensional flow neglecting a radial velocity component does not hold in these regions. Furthermore, the velocity in the wake region is qualitatively similar for different runs. The comparison between the radially-average axial velocity profiles and a Bernoulli profile suggests that the flow in the liquid film can be treated as nearly inviscid .
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