%0 Journal Article %A Zhang , Nengli %A Chao, David F. %D 2001 %I Begell House %N 2-3 %P 10 %R 10.1615/JFlowVisImageProc.v8.i2-3.170 %T FLOW VISUALIZATION IN EVAPORATING LIQUID DROPS AND MEASUREMENT OF DYNAMIC CONTACT ANGLES AND SPREADING RATE %U https://www.dl.begellhouse.com/journals/52b74bd3689ab10b,56351a531f4aff35,353e06545ed51ab5.html %V 8 %X A new hybrid optical system, consisting of reflection-refracted shadowgraphy and top-view photography, is used to visualize flow phenomena in a volatile-liquid drop on a nontransparent substrate and measure the spreading and instant dynamic contact angle of the drop simultaneously. Thermocapillary convection in the drop induced by evaporation and the real-time profile data of the drop are synchronously recorded by video recording systems. Experimental results obtained by using this unique technique clearly reveal that thermocapillary convection strongly affects the spreading process and characteristics of the dynamic contact angle of the drop. The comprehensive information of a sessile drop, including the local contact angle along the periphery of the drop, the instability of the three-phase contact line, and the deformation of the drop shape, can be obtained and analyzed. %8 2001-09-01