Multi-phase-fluid discrimination with local fibre-optical probes. Pt.1: liquid/liquid flows

Demonstrates the use of a novel design of fibre optical sensor (or "local probe") for immiscible fluid discrimination in multiphase flows. These probes are made from standard silica fibres with plane oblique facets polished at the fibre tip and with various surface treatments, including a crucial one for wettability control. Total internal reflection is used to distinguish drops, bubbles or other regions of fluid in multiphase flows on the basis of refractive index contrast. Part 1 demonstrates the use of the probe for distinguishing water from oil (kerosene) in oil/water two phase flows and compares the results with those obtained from a simple cleaved fibre relying on the difference in Fresnel reflectivity for discrimination. Quantitative accuracy is demonstrated by comparison of profiles across a pipe diameter of local, time-averaged volume fractions ("hold-ups") with pipe-averaged hold-ups determined from a carefully calibrated gradiomanometer in a fully developed region of the flow. (Original abstract - amended)