Date of Award

May 2020

Document Type


Degree Name

Master of Science (MS)


Mechanical Engineering

Committee Member

Joshua B Bostwick

Committee Member

John R Saylor

Committee Member

Gregory Mocko


The flow of a thin film down a vertical fiber is valuable for many industrial applications, such as fiber coating, microfluidics, heat exchangers, and desalination processes. It is well known that such flows give rise to a number of instabilities that define the bead-on-fiber morphology including Plateau-Rayleigh breakup, isolated bead formation, and convective instabilities, all of which leave the interface shape axisymmetric. A new asymmetric instability in the flow of liquid on a fiber is observed and its dependence upon liquid properties, flow rate, and fiber diameter is documented. The transition between symmetric and asymmetric morphology depends critically upon the fiber diameter and surface tension. The instability dynamics are described by the bead spacing and bead velocity/frequency and are used to contrast the behavior of the symmetric and asymmetric morphologies. The asymmetric morphology displays more regular dynamics than the symmetric morphology. For example, in the asymmetric morphology the transition from the Plateau-Rayleigh to convective regime occurs when the nozzle velocity is equal to the bead velocity and this dimensionless velocity scales with the capillary number. This prediction, in addition to a full description of the instability dynamics of thin film flows down fibers, can be used as a design tool for novel desalination processes.



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