James Anthony Ruud

Temperature dependent droplet impact dynamics on flat and textured surfaces

Droplet impact dynamics determines the performance of surfaces used in many applications such as anti-icing, condensation, boiling, and heat transfer. We study impact dynamics of water droplets on surfaces with chemistry/texture ranging from hydrophilic to superhydrophobic and across a temperature range spanning below freezing to near boiling conditions. Droplet retraction shows very strong temperature dependence especially on hydrophilic surfaces; it is seen that lower substrate temperatures lead to lesser retraction. Physics-based analyses show that the increased viscosity associated with lower temperatures combined with an increased work of adhesion can explain the decreased retraction. The present findings serve as a starting point to guide further studies of dynamic fluid-surface interaction at various temperatures.

Surface Temperature Measurement of Thermal Barrier Coatings Using Infrared Pyrometry

A method for measuring surface temperature of semitransparent materials was developed and used to measure temperature gradients through a yttria-stabilized zirconia thermal barrier coating (TBC) heated on the front surface with a natural gas flame. A Pt stripe was deposited on the TBC surface, and its temperature was measured using infrared pyrometry at 10.6 μm. A model was developed to determine the radiant intensity emitted from a TBC on a metal substrate with a thermal gradient. The radiant intensity from TBCs was measured as a function of thermal gradient and compared with results of the model.Copyright