Date of Award
8-2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Mechanical Engineering
Committee Chair/Advisor
Joshua B. Bostwick
Committee Member
Zhen Li
Committee Member
Rodrigo Martinez–Duarte
Committee Member
John R. Saylor
Committee Member
Xiangchun Xuan
Abstract
Capillary phenomena are ubiquitous in everyday life with surface tension responsible for shaping liquids and deforming slender structures on length scales smaller than the capillary length, as seen in the formation of drops from a leaky faucet and in the coalescence of wet hair, respectively. Recently, thin film flow down fibers have received significant attention for their ability to produce bead-on-fiber patterns with associated high surface area-to-volume ratios that optimize retention times in heat and mass transfer applications. The presence of a base flow gives rise to complex dynamics including absolute and convective instabilities. The parallelization of these processes through flow down fiber arrays introduces additional complexities including fiber arrangement and flow application technique. This dissertation documents a number of canonical studies of unique flow morphologies seen in thin film flow down fiber arrays, which are analyzed using novel experimental techniques and scaling analysis to better understand the flow physics. The studies are organized into two parts that are focused on flow down a single fiber and flow down two parallel fibers.
The first part concerns two studies of flow down a single fiber focusing on the dynamics near a critical transition point. The first study concerns the flow of a shear-thinning polymer solution and focuses on the transition from symmetric to asymmetric bead morphology and associated bead frequency. The bead frequency is shown to be independent of bead morphology and collapses upon a single curve determined from scaling analysis. The second study concerns the transition from dripping to jetting in flow down a fiber focusing on the role of (i) hysteresis, (ii) near-nozzle bound states, and (iii) intermittency near the critical point. Here bound states are formed over a small range of experimental parameters.
The second part of this thesis concerns gravity-driven flow down parallel fibers. The first study in this part concerns liquid bridges formed through the interactions of liquid applied to a single fiber with the neighboring fiber. The shape of the liquid bridge conforms to a scaling law predicted for static bridges, whereas the bridge dynamics are described by a model which accounts for gravitational effects and viscous dissipation. The second study concerns the formation of a stable liquid sheet which persists indefinitely above a critical flow rate Qc. Dyed liquid sheets are imaged and their profile is constructed from the luminance using the Beer-Lambert law. The sheet stability exhibits hysteresis, which is quantified as it depends upon the dynamic fiber spacing. Finally, we present a method to stabilize falling liquid threads from capillary instability by internally distorting the cross-sectional shape into an elongated cross-section which helps maintain axial uniformity of the thread. A simple stability threshold that primarily depends upon the system geometry is identified and agrees well with experimental observations.
Recommended Citation
Gabbard, Chase Tyler, "Capillary Phenomena in Flow Down Fibers: Beads, Bridges, Sheets, and Threads" (2024). All Dissertations. 3737.
https://open.clemson.edu/all_dissertations/3737
Author ORCID Identifier
0009-0006-4412-4066