Micron-scale liquid jets have applications in a number of technical areas
including combustion, coating, drug delivery, high resolution printing, microelectronics
cooling and particle deposition. The present investigation focuses on the evolution of
these jets with specific emphasis on the effects of surface tension, ambient pressure, and
jet Reynolds number on their formation and break up. In terms of dimensionless
parameters, the present work explores the effects of Reynolds number, Pressure Ratio,
and Ohnesorge number on instabilities of microscale [O(10 μm)] liquid jets.
The stability of the jet column appears to be influenced by the liquid properties,
the flow evolution within the nozzle, and the ambient conditions in the medium into
which the jet is injected. Varying these parameters can lead to transitions between
several instabilities that radically change the characteristics and evolution of the jet.
This thesis includes five chapters. Chapter 2 reviews earlier works that are
relevant to the present jet configurations. Particular attention is paid to five column
instabilities. Chapter 3 describes the experimental apparatus and includes details of the
fluidic system, optical imaging system, and fabrication and implementation of the
micronozzles. Chapter 4 describes the present findings regarding five primary and
distinct instabilities of the jet column, including Rayleigh instability, sinuous instability,
sinuous instability with jet atomization, jet flashing, and non flashing evaporative jets.
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The transitions between these instabilities occur by changing ambient pressure, liquid
properties, and jet velocity. Finally, the main conclusions are discussed in Chapter 5.