Visualization and Velocity Measurements of the Buoyancy-Driven Exchange Flow between Helium and Air through a Vertical Pipe

2nd Report; Visualization of 3-D structure of exchange flow

Abstract

This paper presents the experimental results of visualization into the buoyancy-driven exchange flows between helium and air through a vertical pipe. This type flow might be caused by a pipe rupture accident in a high temperature gas cooled reactor. The exchange flows induced by density difference are complicated by Kelvin-Helm-holtz instability arising on internal contact surface.
The exchange flows formed in the vertical pipe connecting between the helium vessel and ambient air are visualized by means of the laaer-light-sheet illumination technique. The results obtained show the transient process of flow development in the pipe, and unsteady, three dimensional structure of the flows.