Physics Commons^™

Numerical Study Of Owls’ Leading-Edge Serrations, Asif Shahriar Nafi

Electronic Theses and Dissertations

The silent flight ability of owls is often attributed to their unique wing morphology and its interaction with their wingbeat kinematics. Among these distinctive morphological features, leading-edge serrations stand out – these are rigid, miniature, hook-like patterns located at the leading edge of the primary feathers of their wings. It had been hypothesized that these leading-edge serrations serve as a passive flow control mechanism, influencing the aerodynamic performance and potentially affecting the boundary layer development over the wing, subsequently influencing wake flow dynamics. Despite being the subject of research spanning multiple decades, a consensus regarding the aerodynamic mechanisms underpinning owls’ …

Fabrication And Investigation Of Microfluidic Devices That Produce Non-Linear Chemical Gradients, Elijah L. Waters

Electronic Theses and Dissertations

Investigation of cell chemotaxis requires controlled chemical gradients. We investigated microfluidic devices that could enhance small populations' cell assays because of their ability to generate various chemical gradients. Our five designs generate different chemical concentration landscapes that we can easily convert into tools to study cell response to growth factors. Gradient landscapes occurred by splitting and mixing two input fluid concentrations using bifurcations, trifurcations, and Y-mixing junctions in three consecutive steps. Such fluid flow manipulations resulted in nine concentration streams entering a 0.54-mm-wide gradient chamber. The first design used a 1:1 ratio Y-mixer (unbiased) when blending two concentrations, resulting in …

Turbulent Transport Of Dissolved Oxygen In Natural Channels, Alanna Bachtlin

Electronic Theses and Dissertations

The transport and mixing of dissolved oxygen (DO) is important to replenish the oxygen depleted by natural processes; gas transfer in general has implications for ecosystem metabolism and greenhouse gas transfer. Currently, reaeration coefficients can be found through gas tracer methods, which estimates one-way gas transfer. For this project, a net oxygen consumption rate, , was developed using the similarity equations, which provides a value from DO and velocity profiles specific to a stream site. Additionally, three models to calculate friction velocity, which is required for oxygen consumption rate, were compared. Reynolds stresses, mathematically developed in the Reynolds-Averaged Navier-Stokes Equations, …

Towards Long Term Colloid Suspension In A Vertically Rotated System., Md Mahmudur Rahman

Electronic Theses and Dissertations

Within a colloidal suspension gravity may compromise the observation of governing physical interactions, especially those that are weak and/or take significant time to develop. Conducting the experiment in a long-term microgravity environment is a viable option to negate gravitational effects, though significant resources are required to do so. While it may not be possible to simulate long-term microgravity terrestrially, particles can resist quick sedimentation in a confined suspension system rotating vertically with appropriate rotation speed. The goal of the investigation is to demonstrate the existence of long-term particle suspension regime for a certain colloidal suspension while characterizing colloidal behavior due …

Hydrodynamic Impacts Of Expanding Aquaculture, Zhilong Liu

Electronic Theses and Dissertations

Climate change may potentially change aquatic systems and bring certain risks for aquaculture development. Understanding interactions between aquaculture and the environment helps to ensure aquaculture expansion is sustainable in the future. It is critical to determine how farms influence tidal flow patterns, turbulence, mixing and material transport in estuaries. This research aims to determine the flow response of an oyster farm, predict how expanding farms and farm placement will alter estuarine dynamics, and understand how the design of a farm influences material transport.

The hydrodynamic response of a floating oyster aquaculture farm in a low inflow estuary (the Damariscotta River …

Compressible Hydrodynamics Of Few Body Optical Vortices, Jasmine M. Andersen

Electronic Theses and Dissertations

The ubiquity of vortices nearly rivals that of the innumerable fluids and spaces in which they live. Not only do they exist in systems such as superfluids, superconductors, optical fields, or cold atomic gases, for example, but they also exist in our atmospheres, oceans, and even in our veins. This makes understanding and accurately predicting the dynamics of vortices in various systems a relevant and meaningful endeavor.

From a typical hydrodynamic perspective, vortices move within a given fluid because of the background fluid density and phase gradients at the vortex location. However, we find that these gradients alone are insufficient …

A Study Of Several Applications Of Parallel Computing In The Sciences Using Petsc, Nicholas Stegmeier

Electronic Theses and Dissertations

The importance of computing in the natural sciences continues to grow as scientists strive to analyze complex phenomena. The dynamics of turbulence, astrophysics simulations, and climate change are just a few examples where computing is critical. These problems are computationally intractable on all computing platforms except supercomputers, necessitating the continued development of efficient algorithms and methodologies in parallel computing. This thesis investigates the use of parallel computing and mathematical modeling in the natural sciences through several applications, namely computational fluid dynamics for impinging jets in mechanical engineering, simulation of biofilms in an aqueous environment in mathematical biology, and the solution …

Three-Dimensional Bedrock Channel Evolution With Smoothed Particle Hydrodynamics, Nick Richmond

Electronic Theses and Dissertations

Bedrock channels are responsible for balancing and communicating tectonic and climatic signals across landscapes, but it is difficult and dangerous to observe and measure the flows responsible for removing weakly-attached blocks of bedrock from the channel boundary. Consequently, quantitative descriptions of the dynamics of bedrock removal are scarce. Detailed numerical simulation of violent flows in three dimensions has been historically challenging due to technological limitations, but advances in computational fluid dynamics aided by high-performance computing have made it practical to generate approximate solutions to the governing equations of fluid dynamics. From these numerical solutions we gain detailed knowledge of the …

Automated Cfd Optimization To Maximize Wind Farms Performance And Land Use, Rafael Valotta Rodrigues

Electronic Theses and Dissertations

In this research, a computational system was designed to analyze and optimize the layout of wind farms under variable operational conditions. At first, a wind turbine computational fluid dynamic (CFD) model was developed covering the near wake. The near wake flow field was validated against near wake velocity data from the MEXICO experiment. The CFD simulation demonstrated that the tip speed ratio and the pitch angle greatly influence the near wake behavior, affecting the velocity deficit and the turbulence intensity profile in this region. The CFD model was extended to cover the far wake, aiming to become a computational tool …

Numerical Investigation Of Drop Impingement On Dry And Wet Surfaces., Yisen Guo

Electronic Theses and Dissertations

In-flight icing due to supercooled large droplets (SLDs) imposes great danger on aviation safety. Because of the large size, SLDs have different characteristics than typical cloud droplets that most icing encounters involve. As a result, SLDs more likely hit the wing surface and move into areas not protected by de-icing devices to form ice, which can lead to loss of lift, increase in drag, altered controllability, and eventually stall and loss of control of the aircraft. The phenomenon of droplet splashing is considered as the most important aspect of the SLD icing accretion problem. Although previous studies have established splashing …

Transformation Of Nonlinear Waves In The Presence Of Wind, Current, And Vegetation, Haifei Chen

Electronic Theses and Dissertations

Accurate prediction of extreme wave events is crucial for the safe maritime activities and offshore operations. Improved knowledge of wave dissipation mechanisms due to breaking and vegetation leads to accurate wave forecast, protecting life and property along the coast. The scope of the thesis is to examine the wave transformations in the presence of wind, current, and vegetation, using a two-phase flow solver based on the open-source platform OpenFOAM. The Reynolds-Averaged Navier-Stokes (RANS) equations are coupled with a Volume of Fluid (VOF) surface capturing scheme and a turbulence closure model. This RANS-VOF model is adapted to develop a numerical wind-wave-current …

Roles Of Siphon Flows In Suspension Feeding, Kevin Du Clos

Electronic Theses and Dissertations

Benthic marine suspension feeders provide an important link between benthic and pelagic ecosystems. The strength of this link is determined by suspension-feeding rates. Many studies have measured suspension-feeding rates using indirect clearance-rate methods, which are based on the depletion of suspended particles. Direct methods that measure the flow of water itself are less common, but they can be more broadly applied because clearance-rate measurements are affected by properties of the cleared particles. We present pumping rates for three species of suspension feeders, the clams Mya arenaria and Mercenaria mercenaria and the tunicate Ciona intestinalis, calculated using a direct method …

Topographic Signatures Of Geodynamics, Samuel G. Roy

Electronic Theses and Dissertations

The surface of the Earth retains an imperfect memory of the diverse geodynamic, climatic, and surface transport processes that cooperatively drive the evolution of Earth. In this thesis I explore the potential of using topographic analysis and landscape evolution models to unlock past and/or present evidence for geodynamic activity. I explore the potential isolated effects of geodynamics on landscape evolution, particularly focusing on two byproducts of tectonic strain: rock displacement and damage. Field evidence supports a strong correlation between rock damage and erodibility, and a numerical sensitivity analysis supports the hypothesis that an order of magnitude weakening in rock, well …

Computational Fluid Dynamics (Cfd) Modeling Of A Laboratory Scale Coal Gasifier, Kiel S. Schultheiss

Electronic Theses and Dissertations

Furthering gasification technology is an essential part of advancing clean coal technologies. In order to seek insight into the appropriate operations for the formation of synthetic gas (syngas) a numerical simulation was performed to predict the phenomena of coal gasification in a laboratory scale entrained-flow coal gasifier. The mesh for the model was developed with ICEM CFD software and the chemical and physical phenomena were modeled using the fluid flow solver ANSYS FLUENT. Mesh independence was verified. The model was validated with experimental data from several studies performed on a laboratory scale gasifier.

Systematic examination of the model was performed …

Higher-Order Physic For Modeling Ice Streams In Ice Sheets, Debra A. Kenneway

Electronic Theses and Dissertations

Ice streams are transitional between inland glaciers and ice shelves. Hence no stresses can be neglected. Ice streams are important dynamic features of a glacier; it is well known that ice streams drain up to 90% of the ice from an ice sheet. Herein I model ice streams as a multiphysics system of coupled components. This includes treating ice as a non-Newtonian fluid since empirical measurements show a power law relation between stress and strain rate. Sliding is a physical feature that must be included. This is done with a novel approach to sliding by way of a slippery layer. …