A novel flow visualization method called photochromic dye activation (
PDA) technique has been used to investigate flow structures and mechan
isms in various two-phase flow regimes. This non-intrusive flow visual
ization technique utilizes light activation of a photochromic dye mate
rial dissolved in a clear liquid and is a molecular tagging technique,
requiring no seed particles. It has been used to yield both quantitat
ive and qualitative flow data in the liquid phase in annular flow, slu
g flow and stratified-wavy flows. (C) 1998 Elsevier Science S.A. All r
ights reserved.