Turbulent transition modification in dispersed two-phase pipe flow

In a pipe flow, transition to turbulence occurs at some critical Reynolds number, $Re_c$, and transition is associated with intermittent swirling structures extending over the pipe cross section. Depending on the magnitude of $Re_c$, these structures are known either as puffs or slugs. When a dispersed second liquid phase is added to a liquid pipe flow, $Re_c$ can be modified. To explore the mechanism for this modification, an experiment was designed to track and measure these transitional structures. The facility is a pump-driven circuit with a 9m development and test section of diameter 44mm. Static mixers are placed upstream to generate an even dispersion of silicone oil in a water-glycerine flow. Pressure signals were used to identify transitional structures and trigger a high repetition rate stereo-PIV system downstream. Stereo-PIV measurements were obtained in planes normal to the flow, and Taylor's Hypothesis was employed to infer details of the volumetric flow structure. The presentation will describe the sensing and imaging methods along with preliminary results for the single and two-phase flows.