A MOVING OPTICAL FIBER TECHNIQUE FOR STRUCTURE-ANALYSIS OF HETEROGENEOUS PRODUCTS - APPLICATION TO THE DETERMINATION OF THE BUBBLE-SIZE DISTRIBUTION IN LIQUID FOAMS

The bubble-size distribution in liquid foams measured as a function of time can be used to distinguish between the physical processes that determine the breakdown of foams. A new method based on an optical fibre technique was developed to measure various foam characteristics e.g. the rate of drainage, the rate of foam collapse, the change in gas fraction, interbubble gas diffusion (disproportionation) and the evolution of the bubble-size distribution during the ageing of the foam. The method consists of an optical sensor that can distinguish between phases with distinct refractive indexes as are found in liquid foams.