Master's Dissertation

Droplet Impact on Supercooled Surfaces

http://hdl.handle.net/10027/22211

The goal of this work is to understand the underlying physics of fluid droplet interaction with sublimating substrates. The fluids chosen for experiments have similar freezing point, surface tension and densities. However, the heat transfer parameters like latent heat capacity, sensible heat and heat transfer coefficients differ. The investigation involves deep study of fluid interaction physics and dynamics on substrates upon impact and the inverse-Leidenfrost Effect. The main problem addressed in this work are the petal formation, retraction (curling) phenomenon and the different liquid bounce regimes for different fluids on a supercooled substrate that is sublimating in nature. From the experimental study and comparison with literature, it is clear that the petal formation and retraction phenomenon were attributed to the Rayleigh-Taylor instability and the multi-phase heat transfer at the boundary of the sublimating substrate and the droplet expressed in terms of Stefan Number. The novel discovery of this work is the unravelling of the unique bouncing and adhesion regimes of the droplet which were never reported and documented in the literature (Details saved for publication). Various graphs were plotted based on the obtained experimental datasets and trends in the pattern are reported in this work. A great deviation in trends for liquids with higher melting temperatures when compared to conventional fluid (water) is a breakthrough of this research work.

(Experimental Images are saved for publication and will be updated here soon.)

A schematic of one of the underlying physics in the work.

Technologies Used:

Imaging - Photon Fastcam Mini AX100, InfiniProbe^TM TS-160 Universal Micro/Macro Imaging Lens, Nila Zaila lighting unit.

Drop Dispenser - BD 60ml syringe with a BDPrecision Glide Needle (0.9mm dia * 40mm length ) mounted on Dispenser.

Software Used - Photron PFV64bit suite, Image J Image Processing, SolidWorks, Adobe Premier, Origin PRO Graphs.