Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Numerical simulation of rock ramp fishway for small-bodied Great Plains fishes(Montana State University - Bozeman, College of Engineering, 2023) Ufelle, Cindy Chidumebi; Chairperson, Graduate Committee: Kathryn PlymesserThe preservation and restoration of fish populations and their habitats have become significant aspects of environmental conservation efforts. Effectiveness of fish passage structures plays a crucial role in facilitating the successful migration of various fish species. This research focused on utilizing Computational Fluid Dynamics (CFD) models to assess the hydraulic conditions within a rock ramp fishway with varying slopes and flow rates for small-bodied Great Plains fishes. This work built upon a previous study conducted by Swarr (2018) to investigate the passage success rates of three small-bodied fish of the Great Plains of North America: Flathead Chub (Platygobio gracilis), Arkansas Darter (Etheostoma cragini), and Stonecat (Noturus flavus) within a full-scale laboratory rock ramp fishway. Using commercial software, Flow-3D Hydro, CFD models were developed to simulate and predict hydraulic parameters such as flow depths, velocities, and turbulence kinetic energies (TKEs) within the fishway. To validate the accuracy of the CFD models, predicted flow depths and velocities were compared with observed data for two slopes: 2% and 10%. The CFD model results indicated that increasing slopes and flow rates led to corresponding increases in the mean values of the studied parameters. The mean depth varied from 0.051 m on the 2% slope to 0.068 m on the 10% slope. The mean velocity increased from 0.272 m/s on the mildest slope to 1.003 m/s on the steepest slope. Additionally, the average TKE ranged from 0.003 J/kg on the 2% slope to 0.014 J/kg on the 10% slope. The study highlighted that higher velocity and TKE values at steeper slopes may have contributed to the poor upstream passage rate, particularly for weaker swimmer species, like the Arkansas Darter, at slopes greater than 4%, as observed in the physical model study. Findings demonstrated that the presence of rocks in the fishway created diverse flow conditions. Low-velocity zones observed behind rocks within the fishway may provide favorable conditions for successful fish ascent. This research showcases the capabilities of CFD in providing quantitative data for optimizing fish passage structure design and contributing to conservation efforts.Item Controlling the area expansion of a backwards centrifugal fan blade passage using the principles of a diffuser and computational fluid dynamics(Montana State University - Bozeman, College of Engineering, 2021) Michalson, Adam Jeffrey; Chairperson, Graduate Committee: Erick JohnsonCentrifugal Fans are widespread in today's modern built environment. While a few variations of these fans exist, backward centrifugal fans are an efficient economical option capable of producing the pressure and airflow required for many modern building systems. Even though fans have become necessary piece of building engineering to facilitate occupant health and comfort, fan design almost exclusively relies on approximations to equations that have not changed since the 1950s and can consume, on average, 15% of a building's electrical consumption. Additionally, the approximations made support the ease and low cost of manufacturability. The traditional centrifugal fan design is made from stamped metal parts creating a fan blade sandwich with the blades held between an inlet shroud and a backplate. This rectangular blade passage is where the fluid flows through and picks up tangential acceleration. However, since the 1950s, nearly all advancements in fan design have been through incremental changes that are made by individual companies, and these resulting designs and performance data remain proprietary. This research revisits the foundations of centrifugal fan design with more modern tools and utilizes the concept of the diffuser to strictly control the expansion of the blade passage to improve centrifugal fan efficiency. Computational fluid dynamics was used to evaluate the performance of the new design against a traditionally manufactured fan. Combining the diffuser concept with an elliptical profile for the blade passage better controls the uniformity of the velocity field and pressure gradients through the passageway, while also reducing turbulence. Simulations of the new design against the traditional approach to fan design show an increase of nearly 10% in total efficiency.Item Analysis of transport in the brain(Montana State University - Bozeman, College of Engineering, 2021) Ray, Lori Ann; Chairperson, Graduate Committee: Jeffrey Heys; Jeffrey J. Heys was a co-author of the article, 'Fluid flow and mass transport in brain tissue: a literature review' in the journal 'Fluids' which is contained within this dissertation.; Jeffrey J. Iliff and Jeffrey J. Heys were co-authors of the article, 'Analysis of convective and diffusive transport in the brain interstitium' in the journal 'Fluids and barriers of the CNS' which is contained within this dissertation.; Martin Pike, Jeffrey J. Iliff and Jeffrey J. Heys were co-authors of the article, 'Quantification of transport in the whole mouse brain' which is contained within this dissertation.Neurodegeneration is one of the most significant medical challenges facing our time, yet the gap between therapies and understanding of the inner workings of the brain is great. Impairment of waste clearance has been identified as one key underlying factor in the vulnerability of the brain to neurodegeneration, stimulating research towards understanding transport of molecules in the brain. Based on experimental findings, a unique-to-the-brain circulation has been proposed, the glymphatic system, where cerebrospinal fluid surrounding the brain moves into the brain along the periarterial space that surrounds cerebral arteries, flows through the interstitial space between brain cells, where cellular wastes reside, and carries waste out of the brain tissue along perivenous routes. However, current gaps in knowledge about the driving force for fluid flow have generated scientific skepticism, and an independent method for quantifying transport and demonstrating the presence or absence of convection is desirable. In this work, computational transport models are developed and used to analyze published experimental data to determine fundamental transport parameters for different aspects of the glymphatic circulation. Calculated transport parameters are compared to the known diffusivity of tracers through brain tissue to draw conclusions about the presence and significance of bulk flow, or convection. Based on these analyses, transport in the periarterial spaces surrounding major arteries is over 10,000 times faster than diffusion and in brain tissue, containing both periarterial and interstitial space, transport is around 10 times faster than diffusion alone (for characteristic transport lengths around 1 mm). Interstitial velocity is determined to be on the order of 0.01 mm/min, making convection in the interstitial spaces of the brain critical to the transport of large, slow-to-diffuse molecules implicated in neurodegeneration. Convection is demonstrated to be a significant mechanism of transport throughout the brain. Observations and analyses from this work contribute further evidence to a circulatory-like system in the brain with relatively rapid convection along periarterial space, branching throughout the brain tissue and slower convection across that tissue, in the interstitial spaces of the brain. Transport models developed in this work are demonstrated to be useful tools for gleaning further information from experimental data.Item The design and testing of an axial condenser fan(Montana State University - Bozeman, College of Engineering, 2021) Kirk, David Michael; Chairperson, Graduate Committee: Kevin AmendeAxial or propeller fans are a subset of turbomachinery whose application is prevalent in everyday life. In the case of heating, ventilation, air conditioning, and refrigeration (HVAC&R), fans can be a large source of inefficient energy consumption due to their physical operating nature. With the global push for more efficient systems, components of HVAC&R equipment such as fans have become a focal point for researchers in academia and industry alike. Technological improvements in research equipment such as computational fluid dynamics (CFD) and additive manufacturing play a large role in achieving these improved efficiencies. The goal of this research is to improve the efficiency of an axial fan intended for cooling a micro-channel heat exchanger that is used in rooftop condenser units. A higher efficiency retrofit fan was iteratively designed using a commercial CFD software package, Star CCM+, which constitutes much of the research conducted in this project. The iterative models show that significant efficiency gains can be achieved through incremental alterations of classical fan blade geometry elements such as pitch, camber, skew, cross section loft path, chord length, thickness, etc. A physical model of the fan design thought to be the optimal choice for experimental analysis was 3D printed and tested using an AMCA Standard 210 setup. Upon analysis of the physical test results, several discrepancies between simulated and actual results were discovered, highlighting the importance of CFD model validation in the design process. Despite the efficiency gains and advancements in user-friendly packaged software, the simulation underpredicted the power demand and incorrectly depicted the fan's performance at critical operating points showing that improper usage of these experts' tools can inadvertently lead to developed solutions with significant error. While the designed fan achieves an improved peak static efficiency and volumetric flow rate of 53.9% and 4334 CFM respectively, it ultimately did not meet the operating parameters of the specific unit it was designed for and further improvements to the CFD model are needed.Item Characterization of airflow through an air handling unit using computational fluid dynamics(Montana State University - Bozeman, College of Engineering, 2015) Byl, Andrew Evan; Chairperson, Graduate Committee: Erick JohnsonHVAC equipment manufacturers spend a considerable amount of time and effort updating existing product lines in order to meet the ever-increasing demand for energy efficient systems. As a major part of HVAC systems, an air handling unit (AHU) controls the airflow through the system and regulates the indoor air quality. Plenum fans used in AHUs inherently produce a rotational airflow, which can create highly unstructured airflow as it enters a heat exchanger located downstream. This in turn leads to lower heat transfer rates and premature heat exchanger failure. As such, airflow uniformity is presently regarded as an important consideration in designing these systems. Through advancements in computer technologies within the last decade, computational fluid dynamics (CFD) has become an economical solution allowing HVAC equipment designers to numerically model prototypes and reduce the time required to optimize a given design and identify potential failure points. While CFD analysis also offers the ability to visualize and characterize the airflow through an AHU system, it has often been used to model individual components such as fans or heat exchangers without analyzing them as a single unit. This work presents the CFD models used to characterize the airflow within an AHU in order to aid in understanding the effects that flow uniformity has on heat exchanger performance. The airflow uniformity was analyzed over a range of volumetric flow rates, and experiments were used to validate the baseline simulations. Different baffle designs were then added into the validated simulations to observe their influence on both airflow uniformity and heat transfer performance. Results indicate that airflow uniformity is, by itself, an insufficient metric to predict heat transfer performance. Additionally, steady-state CFD analyses performed on simplified geometries are shown to provide a sufficient model to be used for further optimization, when the inlet conditions are well specified.Item Weighted least-squares finite element methods for PIV data assimilation(Montana State University - Bozeman, College of Engineering, 2011) Wei, Fei; Chairperson, Graduate Committee: Jeffrey HeysThe ability to diagnose irregular flow patterns clinically in the left ventricle (LV) is currently very challenging. One potential approach for non-invasively measuring blood flow dynamics in the LV is particle image velocimetry (PIV) using microbubbles. To obtain local flow velocity vectors and velocity maps, PIV software calculates displacements of microbubbles over a given time interval, which is typically determined by the actual frame rate. In addition to the PIV, ultrasound images of the left ventricle can be used to determine the wall position as a function of time, and the inflow and outflow fluid velocity during the cardiac cycle. Despite the abundance of data, ultrasound and PIV alone are insufficient for calculating the flow properties of interest to clinicians. Specifically, the pressure gradient and total energy loss are of primary importance, but their calculation requires a full three-dimensional velocity field. Echo-PIV only provides 2D velocity data along a single plane within the LV. Further, numerous technical hurdles prevent three-dimensional ultrasound from having a sufficiently high frame rate (currently approximately 10 frames per second) for 3D PIV analysis. Beyond microbubble imaging in the left ventricle, there are a number of other settings where 2D velocity data is available using PIV, but a full 3D velocity field is desired. This thesis develops a novel methodology to assimilate two-dimensional PIV data into a three-dimensional Computational Fluid Dynamics simulation with moving domains. To illustrate and validate our approach, we tested the approach on three different problems: a flap displaced by a fluid jut; an expanding hemisphere; and an expanding half ellipsoid representing the left ventricle of the heart. To account for the changing shape of the domain in each problem, the CFD mesh was deformed using a pseudo-solid domain mapping technique at each time step. The incorporation of experimental PIV data can help to identify when the imposed boundary conditions are incorrect. This approach can also help to capture effects that are not modeled directly like the impacts of heart valves on the flow of blood into the left ventricle.