Theses and Dissertations at Montana State University (MSU)
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Item High-fidelity simulations of a rotary bell atomizer with electrohydrodynamic effects(Montana State University - Bozeman, College of Engineering, 2023) Pydakula Narayanan, Venkata Krisshna; Chairperson, Graduate Committee: Mark OwkesAtomizing flows involve the breakup of a liquid into a spray of droplets. These flows play a vital role in various industrial applications such as spray painting and fuel injection. In particular, these processes can have severe impacts especially in automotive paint shops - which can account for up to 50% of the total costs and 80% of the environmental concerns in an automobile manufacturing facility. A device commonly used for painting vehicles is called an electrostatic rotary bell atomizer (ERBA). ERBAs rotate at high speeds while electrically charging the liquid and operating in a background electric field to direct atomized charged droplets towards the target surface. The atomization process directly influences the transfer efficiency (TE) and surface finish quality. Optimal spray parameters used in industry are often obtained from expensive trial-and-error methods. To overcome these limitations, a computational tool has been developed to simulate three-dimensional near-bell ERBA atomization using a high-fidelity volume-of-fluid transport scheme. Additionally, the solver is equipped with physics modules including centrifugal, Coriolis, electrohydrodynamic (EHD), and shear-thinning viscous force models. The primary objective of this research is to investigate the influence of EHD parameters on near-bell atomization of paint and subsequently improve TE in ERBAs in a cost-effective manner. Using the tools developed, numerical simulations are performed to understand the physics of electrically assisted atomization. The influence of various operating parameters, such as liquid flow rate, bell rotation rate, liquid charge density, and bell electric potential, on atomization is examined. Results from a comparative study indicate that the electric field accelerates breakup processes and enhances secondary atomization. The droplet velocity, local Weber number and charge density statistics are also analyzed to understand the complex physics in electrically assisted breakup. Additionally, the effect of shear-thinning behavior of the liquid on atomization is also explored. High-fidelity simulations allow for the extraction of breakup statistics which are otherwise challenging to obtain experimentally. These findings have the potential to drive improvements in the design and operation of ERBAs, leading to enhanced TE and surface finish quality while reducing costs and environmental concerns in automotive paint shops.Item Computationally modeling the aeroelastic physics of flapping-wing flight(Montana State University - Bozeman, College of Engineering, 2023) Schwab, Ryan Keith; Chairperson, Graduate Committee: Mark Jankauski; This is a manuscript style paper that includes co-authored chapters.Flying insects use flapping wings to achieve flight at minuscule sizes. These flapping wings deform elastically under both inertial and aerodynamic loading. While conventional aircraft are often designed to reduce flexibility in their wings, insects harness the benefits of wing flexibility through elastic potential energy storage and enhancement of flapping wing- specific aerodynamic phenomena. Aircraft at insect size scales could have an inexhaustible number of uses ranging from monitoring of congested piping networks in oil refineries, to extraterrestrial land surveyance in thin atmospheres. If these micro air vehicles are to be realized, however, they will need to harness the aerodynamic benefits of flapping wings in order to overcome unfavorable ratios of lift to drag forces and inefficiencies of DC motors at such small sizes. Study of flapping wing aeroelastics is complicated due to the large-amplitude rotations of the wings, unsteady dynamics of the fluid regime, and small size and weight scales of the wings. While some experimental work focuses on techniques like measuring kinematics through motion tracking with high-speed videography, and partial flow field measurements through particle image velocimetry, it is difficult to conduct experiments that paint a full picture of the fluid-structure interaction of these wings. Instead, this research focuses on high-fidelity computational modeling through bilaterally coupled computational fluid dynamics and finite element analysis software to understand the fluid-structure interaction of flapping wings. In this work, a reduced order modeling technique capable of calculating the bulk aeroelastic physics of flapping wings at computational efficiencies suitable for parameter optimization studies was also validated. Finally, the influence of tapered wing thickness on aeroelastics and energetic efficiency was studied. While wing tapering reduced mean thrust, it had a greater reduction on the energetic requirement to produce flapping kinematics and was therefore more energetically efficient.Item Optimizing operating room scheduling considering instrument sterilization processing(Montana State University - Bozeman, College of Engineering, 2019) Harris, Sean Paul; Chairperson, Graduate Committee: David ClaudioThe United States healthcare system represents approximately 18% of the nation's GDP and its numerous challenges continue to receive significant attention from researchers. Within healthcare, operating rooms (ORs) often represent the largest source of revenue and costs in a hospital. Consequently, OR surgical scheduling strategies have been thoroughly examined from a wide variety of performance measures such as overtime, patient waiting time, and utilization rates. ORs are a complex system, and researchers have begun to consider the upstream and downstream resources involved in the surgical process such as the Post Anesthesia Care Unit, Intensive Care Unit, and bed availability. However, two factors that have only begun to be examined are the sterilization process of OR instrumentation and the assignment of instruments into trays and preference cards, either by surgical procedure or individual surgeon preference. Using both collected and historical data, this research 1) examined and improved how the block schedule of an OR suite affected the Sterilization Processing Department (SPD) and 2) examined and improved preference cards for surgical cases. A series of mathematical models optimized surgical block schedules while considering the impact on the SPD and a goal programming model was developed for the tray optimization problem. A comprehensive simulation model of the OR suite and SPD tested the output of the mathematical models. The simulation results confirmed block scheduling does affect SPD performance. A linear goal programming formulation that smoothed SPD workload across block times was the most effective type of model to optimize block scheduling. A goal programming tray optimization model improved expected instrument utilization rates. For practical applications, this research suggests reducing SPD staff turnover is a more effective method for improving SPD performance than rearranging the OR block schedule. This research is among the first of its kind to consider SPD workload as an objective in OR block scheduling models, to consider expected instrument non-usage rates in the tray optimization problem, and to develop a comprehensive simulation model of an OR suite and its SPD to test the results of mathematical models.Item Accurate conservative simulations of multiphase flows applying the height function method to Rudman dual grids(Montana State University - Bozeman, College of Engineering, 2019) Olshefski, Kristopher Thomas; Chairperson, Graduate Committee: Mark OwkesGas-liquid flows can be significantly influenced by the surface tension force, which controls the shape of the interface. The surface tension force is directly proportional to the interface curvature and an accurate calculation of curvature is essential for predictive simulations of these flow types. Furthermore, methods that consistently and conservatively transport momentum, which is discontinuous at the gas-liquid interface, are necessary for robust and accurate simulations. Using a Rudman dual mesh, which discretizes density on a twice as fine mesh, provides consistent and conservative discretization of mass and momentum. The height function method is a common technique to compute an accurate curvature as it is straightforward to implement and provides a second-order calculation. When a dual grid is used, the standard height function method fails to capture fine grid interface perturbations and these perturbations can grow. When these growing perturbations are left uncorrected, they can result in nonphysical dynamics and eventual simulation failure. This work extends the standard height function method to include information from the Rudman dual mesh. The proposed method leverages a fine-grid height function method to compute the fine-gird interface perturbations and uses a fine-grid velocity field to oppose the fine-grid perturbations. This approach maintains consistent mass and momentum transport while also providing accurate interface transport that avoids non-physical dynamics. The method is tested using an oscillating droplet test case and compared to a standard height function. Various iterations of the fine grid method are presented and strengths and shortcomings of each are discussed.Item Extraction of droplet genealogies from high-fidelity atomization simulations(Montana State University - Bozeman, College of Engineering, 2019) Rubel, Roland Francis Clark, IV; Chairperson, Graduate Committee: Mark OwkesMany research groups are performing high-fidelity simulations of atomizing jets that are taking advantage of the continually increasing computational resources and advances in numerical methods. These high-fidelity simulations produce extremely large data-sets characterizing the flow and giving the ability to gather a better understanding of atomization. One of the main challenges with these data sets is their large size, which requires developing tools to extract relevant physics from them. The main goal of this project is to create a physics extraction technique to compute the genealogy of atomization. This information will characterize the process of the coherent liquid core breaking into droplets and ligaments which may proceed to break up further. This event information will be combined with detailed information such as droplet size, shape, flow field characteristics, etc. The extracted information will be stored in a database, allowing the information to be readily and quickly queried to assist in the development and testing of low-fidelity atomization models that agree with the physics predicted by high-fidelity simulations.Item Influence of orifice plate shape on condenser unit effectiveness(Montana State University - Bozeman, College of Engineering, 2018) Kuluris, Stephen Patrick; Chairperson, Graduate Committee: Erick JohnsonIn both residential and commercial buildings, heating, ventilation and air-conditioning (HVAC) is the largest consumer of energy. The HVAC industry works to consistently reduce their energy consumption in order to lower consumer costs and to stay competitive in the field. Therefore, improving fan efficiency of any component in an HVAC system is beneficial. A major part of the industry is to use the vapor-compression refrigeration cycle to cool buildings and an essential component of the cycle is the condenser unit. Axial fans are commonly used to move air through and cool the heated refrigerant coil. Improving axial fan performance by redesigning the casing that surrounds the fan, known as an orifice plate, is suspected to lead to a more productive condenser unit. Changing the geometry can increase performance by reducing turbulence generation both upstream and downstream of the fan, which is thought to be a major contributor to loss in fan fan efficiency. Manufacturing many different geometries in a design process to find an improved orifice plate is time-consuming and expensive. With advances in computer technologies, computational fluid dynamics (CFD) has become a low-cost alternative to iterative, physical prototyping. This work uses CFD in the design process of an orifice plate, to characterize and analyze the effects of different geometries. Fan fan efficiency and volume ow rate characterize the performance of the design, and turbulence, vorticity, and pressure visualization provides further information about the effects of design changes. The orifice geometry upstream and downstream of the fan were changed independently, and then both regions were combined into a single design. Results show that the flow upstream and downstream are affected in different ways, and contribute to overall fan efficiency through different mechanics. An improvement to the inlet region produced an fan efficiency increase of 4.8%, and the addition of an outlet region increases fan efficiency by 9.8%. The combined change in the orifice resulted in an overall increase in fan efficiency by 15.85% over the original design.Item Characterization of the primary instability on atomizing jets using dynamic mode decomposition(Montana State University - Bozeman, College of Engineering, 2018) Krolick, William Christopher; Chairperson, Graduate Committee: Mark OwkesNumerical methods have advanced to the point that many groups can perform detailed numerical simulations of atomizing liquid jets and replicate experimental measurements. However, the simulation results have not lead to a substantial advancement to our understanding of these flows due to the massive amount of data produced. In this work, a tool is developed to extract the physics that destabilize the jets liquid core by leveraging dynamic mode decomposition (DMD). DMD takes ideas from the Arnoldi method as well as the Koopman method to evaluate a non-linear system with a low-rank linear operator. The method reduces the order of the simulation results from all the original data through time to a few key pieces of information. Most important of these are the dynamic modes, their time dynamics, and the DMD spectra. In this case, DMD is applied to the jets liquid core outer radius, which is computed at streamwise and azimuthal locations, i.e., R(theta; x). With the DMD data, we obtain the dominant spatial and temporal modes of the system and their characteristics. The dominant modes provide a useful way to collapse the large data set produced by the simulation into a length and timescale that can be used to initiate reduced-order models and numerically categorize the instabilities on the jets liquid core.Item Evaluation of pitch control techniques for a cross-flow water turbine(Montana State University - Bozeman, College of Engineering, 2017) Gauthier, Timothy Andrew; Chairperson, Graduate Committee: Erick JohnsonCross-flow water turbines are complex devices that have yet to see large-scale implementation relative to conventional horizontal-axis wind turbines. While wind energy was the primary target of past investigations, water energy follows most of the same dynamic principles. However, water currents tend to be much more stable than their wind current counterparts, and many water currents exist in channels that favor the compact shape of the cross-flow turbine. These advantages have rejuvenated interest in cross-flow turbine design for marine energy generation. Computational models give engineers the ability to accurately estimate what designs work best to avoid costly field maintenance and downtime. Specifically, computational fluid dynamics uses the Navier-Stokes equations, a set of differential equations that describe the pressure and velocity fields in a fluid domain. The Reynold-Averaged Navier-Stokes turbulence model described in this work examines how controlling the pitch of water turbine blades can improve system performance and reliability. Pitch means that the blade noses up or down about the chord line which runs from leading edge to trailing edge relative to the inflow. Pitch control was originally developed for helicopter blades and is commonly used by conventional wind turbines, but pitch control for water turbines is a relatively new research area. Initial results suggest significant incremental gain in power output with pitch control up to 149%, as compared to a no-pitch case, based on a to-scale representation of the cross-flow water turbine in the Fluids and Computations Laboratory at Montana State University. Simultaneous reliability gain is observed as the force transmitted by the water to the blades is reduced by 135%; this may allow for lower cost turbine structures and streamlined hydrofoil design. Additionally, turbine wake profile visualization and blade pressure coefficient curves describe the viscous interaction both quantitatively and qualitatively. Cross-flow water turbines have the potential to become a significant worldwide energy source, with performance optimization studies such as these a necessary prerequisite.Item Damage characterization of fiber reinforced composite materials by means of multiaxial testing and digital image correlation(Montana State University - Bozeman, College of Engineering, 2017) Jette, Joseph Terrance; Chairperson, Graduate Committee: Douglas S. CairnsComposite materials offer a unique quality to improve structural designs. Now, not only can a structure's geometry be designed, composite materials offer the engineer the ability to design the layup of the material and, in turn, control some of its structural properties. While this feature of composite materials is appealing, it also poses issues for all processes involved in its design. One of the primary issues is that characterization of these materials in different orientations is often difficult and expensive. Due to composite materials' anisotropy, heterogeneity, and variability, their constitutive and damage behavior remain poorly understood. Often due to this misunderstanding, designs that use composite materials undergo a lengthy, difficult, and expensive procedures to produce the final product. Part of these procedures is the finite element modeling and simulation of designed components which requires accurate material response data. As modeling capabilities improve, provided the proper material damage response modeling data, damage models offer the ability to predict the damage response of designs. The ability to accurately predict damage responses in structures is a primary contributor to a design's development time and its overall success. In this study, multiaxial testing via the Montana State University In-Plane Loader was performed on two carbon fiber epoxy prepreg material systems. This testing was performed to determine the usefulness of digital image correlation and multiaxial testing as a means of characterizing composite materials' damage responses and to produce data capable of informing and validating damage models. The combination of digital image correlation and multiaxial testing provided dense experimental results that may prove useful to qualitatively and quantitatively inform, validate, and enhance computer finite element modeling and analysis.Item Efficient energy modeling : a low carbon source energy assessment of proposed building interconnections based on emerging market modeling tools(Montana State University - Bozeman, College of Engineering, 2014) Talbert, Joshua William; Chairperson, Graduate Committee: Kevin AmendeBuilding energy consumption studies based on whole building energy consumption modeling (Energy Modeling) are not widely applied for performance planning and assessment. The origins of energy modeling as a design resource extend back almost 50 years, but recent developments in computing power and international attention to green house gas emission reduction has brought the benefits of energy modeling to the forefront of building designers, managers, and policy makers. The research herein provides a two-fold benefit to the Montana State University and energy modeling communities by providing energy assessment information and proving the efficacy of modern energy modeling tools currently under development. The procedure followed in this research proves that effective energy modeling can be completed with a significant reduction in the time resource required by harnessing the new energy modeling tools and methods. The University also gains ownership of valuable assessment tools for future application towards energy upgrades, building maintenance, and capital expenditure decisions. Features employed in this research include photographic based model development, model calibration, and proposed system component assessment. The University, based on its need for information about the carbon footprint of campus buildings, commissioned this research through Facilities Services. Modeling results support an overall reduction of campus building related green house gas emissions and prove that emerging energy modeling tools can significantly reduce the time spent on accurate model development.