A metering work methodology and apparatus for determining water velocity in two-phase air/ water flow under slug flow conditions at low mixture velocities are provided. The metering method proposed utilises a non-invasive clamp-on transit time ultrasonic flowmeter and nonintrusive conductance sensors distributed along 2-inch Perspex pipe. The metering method comprises the steps of:
establishing slug parameters using statistical and signal analysis of the conductance sensors measurements;
measuring the local slug body velocity VSL (Estimated) using the non-invasive ultrasonic technique;
calculate the total liquid velocity for the slug unit based on predictive stable slug model, and
validate the total liquid velocity by using upstream electromagnetic reference flow meter.