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Journal of Flow Visualization and Image Processing
SJR: 0.161 SNIP: 0.312 CiteScore™: 0.1

ISSN Druckformat: 1065-3090
ISSN Online: 1940-4336

Journal of Flow Visualization and Image Processing

DOI: 10.1615/JFlowVisImageProc.v12.i3.50
pages 285-300

OPTICAL CATASTROPHE APPLIED IN STUDY OF SPREADING OF EVAPORATING LIQUID DROPS ON A SOLID SURFACE

Nengli Zhang
Pearlica Technologies, Inc.
David F. Chao
Fluid Physics and Transport Branch, Ohio Aerospace Institute at NASA Glenn Research Center, Cleveland, OH 44135, USA

ABSTRAKT

Optical catastrophe occurring in a far field of waves of a drop-refracted laser beam implies a wealth of information about drop spreading. The present paper reveals, based on catastrophe optics, that the far-field caustic images can successfully detect the interface instability of sessile drops, measure the contact angles of the drops, estimate the drop-foot height, visualize capillary flows in the drops, and investigate the spreading characteristics of evaporating liquid drops, such as the drop profile at the three-phase line, the effects of evaporation and capillary flows on the spreading, etc. All of these obviously are very important for the study of spreading of evaporating liquid drops. As an example of the applications, three typical volatile liquid drops were tested using the far-field caustic images of the drop-refracted laser beam. The effects of evaporation and thermocapillary convection on the spreading are revealed and discussed.