Abstract
Gas-liquid two-phase fluctuation flow in vertical sudden expansion pipe is investigated. Visualization results and pressure measurements show the effect of Reynolds number and volumetric flow rate ratio, within the range of bubbly flow, on fluctuation phenomena that are considered and studied conducting FFT analysis. From visualized flow pattern the existence of two vortices is made apparent. One, the primary large vortex that occupies the main part of the circulation zone and secondly, small vortex appear in the bottom step and flows along the surface of the pipe. An annular ring shaped small obstacle is mounted downstream the expansion at different positions and the prospect of flow control is investigated for it expands the primary vortex region of which intensity is reduced. In addition, a step is mounted and its effect studied. Visualization and FFT analyses of the fluctuating phenomena are conducted and the comparative results with the normal expansion case are examined.
