LOCAL VOID FRACTION AND FLUID VELOCITY MEASUREMENTS IN A CAPILLARY CHANNEL WITH A SINGLE OPTICAL PROBE

The present work investigates the capability of a single optical probe in terms of simultaneous local void fraction and velocity measurement of a two-phase slug flow in a capillary pipe. The optical fiber probe is mounted on a 2-mm internal diameter transparent tube where a water-air flow is recirculated. Tests are performed by varying both the probe position and the liquid mass flow rate. A high-speed camera is also used to check the accuracy of the optical signal and to perform a qualitative analysis on the intrusiveness of the optic probe. Results prove that accurate velocity measurements of two-phase confined flows can be performed by means of a single fiber mounted perpendicular to the flow direction. The peculiarities of the presented measurement method with respect to the one used for macroscale pipes are discussed together with a novel definition of latency length.