Graduation Semester and Year
Summer 2025
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Mechanical Engineering
Department
Mechanical and Aerospace Engineering
First Advisor
Ashfaq Adnan
Abstract
Abstract
CAVITATION DYNAMICS IN HETEROGENEOUS SOFT GEL
Sachan Johny, PhD
The University of Texas at Arlington, 2025
The Supervising Professor: Dr. Ashfaq Adnan
The increasing utilization of cavitation in medical treatments and the recognition of cavitation- induced brain injuries underscore the necessity for precise characterization and understanding of dynamic cavitation in heterogeneous soft materials. Despite its significance, current understanding is limited, primarily due to challenges in reliable experimental methodologies for delicate tissue simulants like gelatin under high rate loading. This study employs a recently developed drop tower integrated system, featuring a unique sample holder with effective springs and dampers, to investigate soft materials under such conditions. This system uniquely allows for the adjustment of the input acceleration profile, critical for accurately replicating blunt force injury patterns and examining biological responses. This methodology facilitates observation of cavitation's temporal progression and quantitative measurement of critical acceleration for nucleation. The integrated drop tests combine a conventional drop tower, high-speed camera, accelerometers, and a specialized cuvette holder.
While recent studies report critical acceleration for homogeneous gelatin, we first introduce heterogeneity by layering 7.5% w/v gelatin, prepared via a precise temperature-controlled protocol, to form interfaces. We analyze the effects of interface number and location on cavitation thresholds, revealing a slight reduction in critical acceleration as layer count increases. Further investigations on bi-material samples (gelatin base, water layer) with horizontal, vertical, and inclined interfaces indicate that cavitation nucleation in gelatin is delayed, often until a secondary cavitation wave initiates in the water region. Moreover, cavitation duration in gelatin is significantly shorter than in water.
To elucidate these bi-material dynamics, a computational study based on the Rayleigh-Plesset equation is proposed. This model will incorporate the viscoelastic properties of gelatin and Newtonian fluid properties of water to analyze the experimentally observed delayed cavitation onset and shorter bubble lifetime in the gel phase compared to water. By simulating bubble dynamics under impact-derived pressure loading, this computational approach aims to provide mechanistic insights into how material property differences govern these distinct behaviors.
These combined experimental and computational insights suggest that biological tissues may exhibit similar behaviors, directly impacting ultrasound therapy and protective equipment design. By providing quantitative assessments and mechanistic understanding of cavitation in heterogeneous hydrogels, this study contributes to improved safety margins in medical treatments and the development of more accurate predictive models for traumatic brain injury risk assessment.
Keywords
Cavitation, Heterogeneous soft materials, Gelatin hydrogel, Drop tower experiment, Critical acceleration, Interfacial effects
Disciplines
Mechanical Engineering
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Johny, Sachan, "CAVITATION DYNAMICS IN HETEROGENEOUS SOFT GEL" (2025). Mechanical and Aerospace Engineering Dissertations. 436.
https://mavmatrix.uta.edu/mechaerospace_dissertations/436