Electrical capacitance tomography can be used as a research tool as well as an industrial flowmeter. We have Tomoflow research systems available for sale and hire. In horizontal gas-liquid flows, a customer has used our ECT systems to measure the structure of ‘slug’ flow. One particular type of bubbly slug is known colloquially in Norwegian as a ‘ghost’ because it drifts past in the working section with a particular soft whispering sound. From the outside of the pipe these ghosts appear as frothy slugs with no particular structure visible. Seen from ECT measurements however it is apparent that they are bubbly waves which have thrown ‘wings’ up around the pipe circumference leaving an air core.
The video shows a visualisation from the ECT images using a Tomoflow R100. The images show liquid (oil) as red, air as blue and concentrations of air in the oil as green shading in between.
Such structural visualizations are limited by the fact that the 50% contour is not actually an interface, but they give an unusually good insight into the way the flows are built. It should also be remembered that the pictures are a way of presenting quantitative data, and not just qualitative indications. Within each pixel we have a numerical measurement of concentration at every point in time and within each zone a good estimate of axial velocity.