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Description
Intelligent engineering designs require an accurate understanding of material behavior, since any uncertainties or gaps in knowledge must be counterbalanced with heightened factors of safety, leading to overdesign. Therefore, building better structures and pushing the performance of new components requires an improved understanding of the thermomechanical response of advanced materials under service conditions. This dissertation provides fundamental investigations of several advanced materials: thermoset polymers, a common matrix material for fiber-reinforced composites and nanocomposites; aluminum alloy 7075-T6 (AA7075-T6), a high-performance aerospace material; and ceramic matrix composites (CMCs), an advanced composite for extreme-temperature applications. To understand matrix interactions with various interfaces and nanoinclusions at their fundamental scale, the properties of thermoset polymers are studied at the atomistic scale. An improved proximity-based molecular dynamics (MD) technique for modeling the crosslinking of thermoset polymers is carefully established, enabling realistic curing simulations through its ability to dynamically and probabilistically perform complex topology transformations. The proximity-based MD curing methodology is then used to explore damage initiation and the local anisotropic evolution of mechanical properties in thermoset polymers under uniaxial tension with an emphasis on changes in stiffness through a series of tensile loading, unloading, and reloading experiments. Aluminum alloys in aerospace applications often require a fatigue life of over 109 cycles, which is well over the number of cycles that can be practically tested using conventional fatigue testing equipment. In order to study these high-life regimes, a detailed ultrasonic cycle fatigue study is presented for AA7075-T6 under fully reversed tension-compression loading. The geometric sensitivity, frequency effects, size effects, surface roughness effects, and the corresponding failure mechanisms for ultrasonic fatigue across different fatigue regimes are investigated. Finally, because CMCs are utilized in extreme environments, oxidation plays an important role in their degradation. A multiphysics modeling methodology is thus developed to address the complex coupling between oxidation, mechanical stress, and oxygen diffusion in heterogeneous carbon fiber-reinforced CMC microstructures.
ContributorsSchichtel, Jacob (Author) / Chattopadhyay, Aditi (Thesis advisor) / Dai, Lenore (Committee member) / Ghoshal, Anindya (Committee member) / Huang, Huei-Ping (Committee member) / Jiao, Yang (Committee member) / Oswald, Jay (Committee member) / Arizona State University (Publisher)
Created2022
Description
In this dissertation, two types of passive air freshener products from Henkel, the wick-based air freshener and gel-based air freshener, are studied for their wicking mechanisms and evaporation performances.The fibrous pad of the wick-based air freshener is a porous medium that absorbs fragrance by capillary force and releases the fragrance into the ambient air. To investigate the wicking process, a two-dimensional multiphase flow numerical model using COMSOL Multiphysics is built. Saturation and liquid pressure inside the pad are solved. Comparison between the simulation results and experiments shows that evaporation occurs simultaneously with the wicking process. The evaporation performance on the surface of the wicking pad is analyzed based on the kinetic theory, from which the mass flow rate of molecules passing the interface of each pore of the porous medium is obtained. A 3D model coupling the evaporation model and dynamic wicking on the evaporation pad is built to simulate the entire performance of the air freshener to the environment for a long period of time. Diffusion and natural convection effects are included in the simulation. The simulation results match well with the experiments for both the air fresheners placed in a chamber and in the absent of a chamber, the latter of which is subject to indoor airflow.
The gel-based air freshener can be constructed as a porous medium in which the solid network of particles spans the volume of the fragrance liquid. To predict the evaporation performance of the gel, two approaches are tested for gel samples in hemispheric shape. The first approach is the sessile drop model commonly used for the drying process of a pure liquid droplet. It can be used to estimate the weight loss rate and time duration of the evaporation. Another approach is to simulate the concentration profile outside the gel and estimate the evaporation rate from the surface of the gel using the kinetic theory. The evaporation area is updated based on the change of pore size. A 3D simulation using the same analysis is further applied to the cylindrical gel sample. The simulation results match the experimental data well.
ContributorsYuan, Jing (Author) / Chen, Kangping (Thesis advisor) / Herrmann, Marcus (Committee member) / Huang, Huei-Ping (Committee member) / Wang, Liping (Committee member) / Jiao, Yang (Committee member) / Arizona State University (Publisher)
Created2021
Description
Stiffness and flexibility are essential in many fields, including robotics, aerospace, bioengineering, etc. In recent years, origami-based mechanical metamaterials were designed for better mechanical properties including tunable stiffness and tunable collapsibility. However, in existing studies, the tunable stiffness is only with limited range and limited controllability. To overcome these challenges, two objectives were proposed and achieved in this dissertation: first, to design mechanical metamaterials with metamaterials with selective stiffness and collapsibility; second, to design mechanical metamaterials with in-situ tunable stiffness among positive, zero, and negative.In the first part, triangulated cylinder origami was employed to build deployable mechanical metamaterials through folding and unfolding along the crease lines. These deployable structures are flexible in the deploy direction so that it can be easily collapsed along the same way as it was deployed. An origami-inspired mechanical metamaterial was designed for on-demand deployability and selective collapsibility: autonomous deployability from the collapsed state and selective collapsibility along two different paths, with low stiffness for one path and substantially high stiffness for another path. The created mechanical metamaterial yields unprecedented load bearing capability in the deploy direction while possessing great deployability and collapsibility. The principle in this prospectus can be utilized to design and create versatile origami-inspired mechanical metamaterials that can find many applications.
In the second part, curved origami patterns were designed to accomplish in situ stiffness manipulation covering positive, zero, and negative stiffness by activating predefined creases on one curved origami pattern. This elegant design enables in situ stiffness switching in lightweight and space-saving applications, as demonstrated through three robotic-related components. Under a uniform load, the curved origami can provide universal gripping, controlled force transmissibility, and multistage stiffness response. This work illustrates an unexplored and unprecedented capability of curved origami, which opens new applications in robotics for this particular family of origami patterns.
ContributorsZhai, Zirui (Author) / Nian, Qiong (Thesis advisor) / Zhuang, Houlong (Committee member) / Huang, Huei-Ping (Committee member) / Zhang, Wenlong (Committee member) / Liu, Yongming (Committee member) / Arizona State University (Publisher)
Created2021
Description
The fast pace of global urbanization makes cities the hotspots of population density and anthropogenic activities, leading to intensive emissions of heat and carbon dioxide (CO2), a primary greenhouse gas. Urban climate scientists have been actively seeking effective mitigation strategies over the past decades, aiming to improve the environmental quality for urban dwellers. Prior studies have identified the role of urban green spaces in the relief of urban heat stress. Yet little effort was devoted to quantify their contribution to local and regional CO2 budget. In fact, urban biogenic CO2 fluxes from photosynthesis and respiration are influenced by the microclimate in the built environment and are sensitive to anthropogenic disturbance. The high complexity of the urban ecosystem leads to an outstanding challenge for numerical urban models to disentangling and quantifying the interplay between heat and carbon dynamics.This dissertation aims to advance the simulation of thermal and carbon dynamics in urban land surface models, and to investigate the role of urban greening practices and urban system design in mitigating heat and CO2 emissions. The biogenic CO2 exchange in cities is parameterized by incorporating plant physiological functions into an advanced single-layer urban canopy model in the built environment. The simulation result replicates the microclimate and CO2 flux patterns measured from an eddy covariance system over a residential neighborhood in Phoenix, Arizona with satisfactory accuracy. Moreover, the model decomposes the total CO2 flux from observation and identifies the significant CO2 efflux from soil respiration. The model is then applied to quantify the impact of urban greening practices on heat and biogenic CO2 exchange over designed scenarios. The result shows the use of urban greenery is effective in mitigating both urban heat and carbon emissions, providing environmental co-benefit in cities. Furthermore, to seek the optimal urban system design in terms of thermal comfort and CO2 reduction, a multi-objective optimization algorithm is applied to the machine learning surrogates of the physical urban land surface model. There are manifest trade-offs among ameliorating diverse urban environmental indicators despite the co-benefit from urban greening. The findings of this dissertation, along with its implications on urban planning and landscaping management, would promote sustainable urban development strategies for achieving optimal environmental quality for policy makers, urban residents, and practitioners.
ContributorsLi, Peiyuan (Author) / Wang, Zhihua (Thesis advisor) / Vivoni, Enrique (Committee member) / Huang, Huei-Ping (Committee member) / Myint, Soe (Committee member) / Xu, Tianfang (Committee member) / Arizona State University (Publisher)
Created2021
Description
Advancements to a dual scale Large Eddy Simulation (LES) modeling approach for immiscible turbulent phase interfaces are presented. In the dual scale LES approach, a high resolution auxiliary grid, used to capture a fully resolved interface geometry realization, is linked to an LES grid that solves the filtered Navier-Stokes equations. Exact closure of the sub-filter interface terms is provided by explicitly filtering the fully resolved quantities from the auxiliary grid. Reconstructing a fully resolved velocity field to advance the phase interface requires modeling several sub-filter effects, including shear and accelerational instabilities and phase change. Two sub-filter models were developed to generate these sub-filter hydrodynamic instabilities: an Orr-Sommerfeld model and a Volume-of-Fluid (VoF) vortex sheet method. The Orr-Sommerfeld sub-filter model was found to be incompatible with the dual scale approach, since it is unable to generate interface rollup and a process to separate filtered and sub-filter scales could not be established. A novel VoF vortex sheet method was therefore proposed, since prior vortex methods have demonstrated interface rollup and following the LES methodology, the vortex sheet strength could be decomposed into its filtered and sub-filter components. In the development of the VoF vortex sheet method, it was tested with a variety of classical hydrodynamic instability problems, compared against prior work and linear theory, and verified using Direct Numerical Simulations (DNS). An LES consistent approach to coupling the VoF vortex sheet with the LES filtered equations is presented and compared against DNS. Finally, a sub-filter phase change model is proposed and assessed in the dual scale LES framework with an evaporating interface subjected to decaying homogeneous isotropic turbulence. Results are compared against DNS and the interplay between surface tension forces and evaporation are discussed.
ContributorsGoodrich, Austin Chase (Author) / Herrmann, Marcus (Thesis advisor) / Dahm, Werner (Committee member) / Kim, Jeonglae (Committee member) / Huang, Huei-Ping (Committee member) / Kostelich, Eric (Committee member) / Arizona State University (Publisher)
Created2023
Description
En la zona metropolitana de Phoenix, el calor urbano está afectando la salud, la seguridad y la economía y se espera que estos impactos empeoren con el tiempo. Se prevé que el número de días por encima de 110˚F aumentará más del doble para el 2060. En mayo de 2017, The Nature Conservancy, el Departamento de Salud Pública del condado de Maricopa, Central Arizona Conservation Alliance, la Red de Investigación en Sostenibilidad sobre la Resiliencia Urbana a Eventos Extremos, el Centro de Investigación del Clima Urbano de Arizona State University y el Center for Whole Communities lanzaron un proceso participativo de planificación de acciones contra el calor para identificar tanto estrategias de mitigación como de adaptación a fin de reducir directamente el calor y mejorar la capacidad de los residentes para lidiar con el calor. Las organizaciones comunitarias con relaciones existentes en tres vecindarios seleccionados para la planificación de acciones contra el calor se unieron más tarde al equipo del proyecto: Phoenix Revitalization Corporation, RAILMesa y Puente Movement. Más allá de construir un plan de acción comunitario contra el calor y completar proyectos de demostración, este proceso participativo fue diseñado para desarrollar conciencia, iniciativa y cohesión social en las comunidades subrepresentadas. Asimismo el proceso de planificación de acciones contra el calor fue diseñado para servir como modelo para esfuerzos futuros de resiliencia al calor y crear una visión local, contextual y culturalmente apropiada de un futuro más seguro y saludable. El método iterativo de planificación y participación utilizado por el equipo del proyecto fortaleció las relaciones dentro y entre los vecindarios, las organizaciones comunitarias, los responsables de la toma de decisiones y el equipo núcleo, y combinó la sabiduría de la narración de historias y la evidencia científica para comprender mejor los desafíos actuales y futuros que enfrentan los residentes durante eventos de calor extremo. Como resultado de tres talleres en cada comunidad, los residentes presentaron ideas que quieren ver implementadas para aumentar su comodidad y seguridad térmica durante los días de calor extremo.
Como se muestra a continuación, las ideas de los residentes se interceptaron en torno a conceptos similares, pero las soluciones específicas variaron entre los vecindarios. Por ejemplo, a todos los vecindarios les gustaría agregar sombra a sus corredores peatonales, pero variaron las preferencias para la ubicación de las mejoras para dar sombra. Algunos vecindarios priorizaron las rutas de transporte público, otros priorizaron las rutas utilizadas por los niños en su camino a la escuela y otros quieren paradas de descanso con sombra en lugares clave. Surgieron cuatro temas estratégicos generales en los tres vecindarios: promover y educar; mejorar la comodidad/capacidad de afrontamiento; mejorar la seguridad; fortalecer la capacidad. Estos temas señalan que existen serios desafíos de seguridad contra el calor en la vida diaria de los residentes y que la comunidad, los negocios y los sectores responsables de la toma de decisión deben abordar esos desafíos.
Los elementos del plan de acción contra el calor están diseñados para incorporarse a otros esfuerzos para aliviar el calor, crear ciudades resilientes al clima y brindar salud y seguridad pública. Los socios de implementación del plan de acción contra el calor provienen de la región de la zona metropolitana de Phoenix, y se brindan recomendaciones para apoyar la transformación a una ciudad más fresca.
Para ampliar la escala de este enfoque, los miembros del equipo del proyecto recomiendan a) compromiso continuo e inversiones en estos vecindarios para implementar el cambio señalado como vital por los residentes, b) repetir el proceso de planificación de acción contra el calor con líderes comunitarios en otros vecindarios, y c) trabajar con las ciudades, los planificadores urbanos y otras partes interesadas para institucionalizar este proceso, apoyando las políticas y el uso de las métricas propuestas para crear comunidades más frescas.
ContributorsMesserschmidt, Maggie (Contributor) / Guardaro, Melissa (Contributor) / White, Jessica R. (Contributor) / Berisha, Vjollca (Contributor) / Hondula, David M. (Contributor) / Feagan, Mathieu (Contributor) / Grimm, Nancy (Contributor) / Beule, Stacie (Contributor) / Perea, Masavi (Contributor) / Ramirez, Maricruz (Contributor) / Olivas, Eva (Contributor) / Bueno, Jessica (Contributor) / Crummey, David (Contributor) / Winkle, Ryan (Contributor) / Rothballer, Kristin (Contributor) / Mocine-McQueen, Julian (Contributor) / Maurer, Maria (Artist) / Coseo, Paul (Artist) / Crank, Peter J (Designer) / Broadbent, Ashley (Designer) / McCauley, Lisa (Designer) / Nature's Cooling Systems Project (Contributor) / Nature Conservancy (U.S.) (Contributor) / Phoenix Revitalization Corporation (Contributor) / Puente Movement (Contributor) / Maricopa County (Ariz.). Department of Public Health (Contributor) / Central Arizona Conservation Alliance (Contributor) / Arizona State University. Urban Climate Research Center (Contributor) / Arizona State University. Urban Resilience to Extremes Sustainability Research Network (Contributor) / Center for Whole Communities (Contributor) / RAILmesa (Contributor) / Vitalyst Health Foundation (Funder)
Created2022
Description
The hydrologic cycle in drylands is complex with large spatiotemporal variationsacross scales and is particularly vulnerable to changes in climate and land cover. To
address the challenges posed by hydrologic changes, a synergistic approach that
combines numerical models, ground and remotely sensed observations, and data analysis
is crucial. This dissertation uses innovative detection and modeling techniques to assess
key hydrologic variables in drylands, including irrigated water use, streamflow, and
snowpack conditions, answering following research questions that also have broad
societal implications: (1) What are the individual and combined effects of future climate
and land use change on irrigation water use (IWU) in the Phoenix Metropolitan Area
(PMA)?; (2) How can temporal changes in streamflow and the impacts of flash flooding
be detected in dryland rivers?; and (3) What are the impacts of rainfall-snow partitioning
on future snowpack and streamflow in the Colorado River Basin (CRB)?
Firstly, I conducted a scenario modeling using the Variable Infiltration Capacity
(VIC) model under future climate and land use change scenarios. Results showed that
future IWU will change from -0.5% to +6.8% in the far future (2071-2100) relative to the
historical period (1981-2010). Secondly, I employed CubeSat imagery to map streamflow
presence in the Hassayampa River of Arizona, finding that the imaging capacity of
CubeSats enabled the detection of ephemeral flow events using the surface reflectance of
the near-infrared (NIR) band. Results showed that 12% of reaches were classified as
intermittent, with the remaining as ephemeral. Finally, I implemented a physically-based
rainfall-snow partitioning scheme in the VIC model that estimates snowfall fraction from
the wet-bulb temperature using a sigmoid function. The new scheme predicts more
significant declines in snowfall (-8 to -11%) and streamflow (-14 to -27%) by the end of
the 21st century over the CRB, relative to historical conditions.
Overall, this dissertation demonstrates how innovative technologies can enhance
the understanding of dryland hydrologic changes and inform decision-making of water
resources management. The findings offer important insights for policymakers, water
managers, and researchers who seek to ensure water resources sustainability under the
effects of climate and land use change.
ContributorsWang, Zhaocheng (Author) / Vivoni, Enrique R (Thesis advisor) / White, Dave D (Committee member) / Mascaro, Giuseppe (Committee member) / Huang, Huei-Ping (Committee member) / Wang, Zhihua (Committee member) / Arizona State University (Publisher)
Created2023
Description
This research aims to identify optimal pin fin shapes that minimize flow pressuredrop and maximize heat transfer performance while investigating the influence of genetic
algorithm (GA) parameters on these shapes. The primary goal is to discover innovative
pin fin configurations through the use of a GA, moving away from traditional circular
cylindrical designs. The study also examines GA parameters, including population size,
generation size, selection methods, crossover rates, tournament size, and elite counts. A
physical condition considered in this study is a rectangular channel with a square
cross-section integrated with 10 pin fins, operating at a Reynolds number of 2316, and
subjected to a heat flux of 5 W/cm2 at the bottom surface. Overall, the research seeks to
enhance the energy efficiency of a liquid cooling system, with potential applications in
the thermal management of computing devices. By enabling operating at significantly
lower power, the optimized cooling system promises to reduce energy consumption and
operational costs.
ContributorsKim, Ji Yeon (Author) / Kwon, Beomjin (Thesis advisor) / Wang, Robert (Committee member) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2024
Description
This dissertation investigates the complex dynamics of semi-dilute inertial particles suspended in vortices using the Eulerian-Lagrangian method. The study explores the modulation of flow induced by inertial particles, focusing on the characteristics of a single vortex, instability analysis within particle-laden flows, and the merging process of co-rotating vortices. Simulations reveal a preferential concentration mechanism, where inertial particles cluster around a void fraction bubble, accelerating the decay of the vortex tube. Small-scale clusters, arising from particle-trajectory crossings, induce significant gradients in the fluid vorticity field, contributing to rapid vortex breakdown. Within a specific Stokes number range, increased particle inertia results in faster vortex decay and stronger inhomogeneity in the particle phase. The instability mechanism in particle-laden flows is explored using a Rankine vortex model. Two-way coupling triggers azimuthal perturbations, leading to the breakdown of the vortex structure. Linear Stability Analysis and Two-Fluid modeling demonstrate that the dusty vortex flow exhibits unstable modes, with growth rates increasing with wavenumber. Eulerian-Lagrangian simulations validate these results, showing excellent agreement between computed and predicted growth rates. The dissertation also delves into the co-rotating vortex merger in a semi-dilute dusty flow. For weak inertial effects, merger experiences a delay compared to particle-free vortices. Under moderate inertial conditions, the merger process exhibits repulsion, increased separation, and eventual convective merger stages. Highly inertial particles stretch the vortex core, initiating a merger with an outcome of a particle-free vortex core surrounded by a halo of concentrated particles. In conclusion, the feedback force from the dispersed phase induces instability and significantly influences the dynamics of vortices in particle-laden flows. The findings contribute to a deeper understanding of the intricate interactions between inertial particles and vortical structures.
ContributorsShuai, Shuai (Author) / Kasbaoui, Mohamed Houssem (Thesis advisor) / Herrmann, Marcus (Committee member) / Peet, Yulia (Committee member) / Huang, Huei-Ping (Committee member) / Wang, Zhihua (Committee member) / Arizona State University (Publisher)
Created2024
Description
This thesis aims to determine how finite wing aerodynamic loads change in proximity to the ground. In this study, the primary design tool is an inviscid panel method code, VORLAX.
The validation tool is a commercial volume grid CFD package, ANSYS FLUENT. I use VORLAX
to simulate wings with different incidences and aspect ratios to look at how ground effect
impacts spanwise loading and incipient flow separation. Then the results were compared to
widely published equations such as McCormick, Torenbeek, and Hoerner & Borst. Because I
found that these “famous” equations function best only for specific conditions, I propose a
new empirical equation to estimate ground effect lift as a function of aspect ratio and
incidence. Using Stratford’s method to predict signs of flow separation in the inviscid
solutions, I found that variations in the height above the ground were not significant enough
to change the stall angle of low aspect ratio wings. I did find early signs of flow separation
with increasing aspect ratio. I observe significant changes in spanwise loading when in
ground effect; as I narrow the gap, the transverse loading builds higher near the center of the
wing. These effects were more apparent in wings with smaller aspect ratio; higher aspect
ratio wings experience a higher loading gradient near the tips in proximity to the ground. I
found that high aspect ratio wings have a smaller stall angle compared to that of lower
aspect ratio wings; these trends are consistent between the potential flow solution and the
volume grid CFD viscous solution.
ContributorsValenzuela, Jose Vanir (Author) / Takahashi, Timothy (Thesis advisor) / Dahm, Werner (Committee member) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2024