Scholarship & Research
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Item Reduced-order aeroelastic modeling of a torsionally compliant UAV rotor blade(Montana State University - Bozeman, College of Engineering, 2021) Marks, Montana William; Chairperson, Graduate Committee: Mark JankauskiSmall-scale quadrotor helicopters, or quadcopters, have increased in popularity significantly in the past decade. These unmanned aerial vehicles (UAVs) have a wide range of applications - from aerial photography and cinematography to agriculture. Increasing flight time and payload capacity are of the utmost importance when designing these systems, and reducing vehicle weight is the simplest method for improving these performance metrics. However, lighter components and structures are often more flexible and may deform during operation. This is especially the case for flexible UAV blade rotor behavior during flight. Modeling rotor blade deformations is non-trivial due to the coupling between the structure and the surrounding flow, which is called Fluid-Structure Interaction (FSI). Several methods exist for FSI modeling where the most common involves integrating Finite Element and Computational Fluid Dynamics solvers. However, these higher-fidelity models are computationally expensive and are not ideal for parametric studies that consider variable rotor geometry, material properties or other physical characteristics. This research develops low-order modeling techniques that can be leveraged by UAV rotor designers. Here, a reduced-order FSI model of a small-scale UAV rotor blade is developed using Lagrangian mechanics paired with a blade element model. The rotor blade is discretized into rectangular elements along the span. Each blade element is constrained to uni-axial rotation about the span-wise axis and is treated as a torsional stiffness element. The quasi-static equilibrium state of the structure due to aerodynamic forces at user-defined operational conditions is then determined. The model presented is capable of producing a converged solution in as little as 0.016 seconds, as opposed to higher-order FSI models, which can take up to several orders of magnitude longer to solve. It is determined that the deflection of a flexible blade can reduce the total aerodynamic lift from 18-25% when compared to a rigid blade with the same initial geometry. It is shown that the model allows a user to tailor the initial pre-twist of the flexible rotor blade such that losses in lift are reduced to 0.68-5.7%.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 Cessna 182b windscreen material model development and full scale UAS to aircraft impact testing facility(Montana State University - Bozeman, College of Engineering, 2020) Arnold, Forrest Jacob; Chairperson, Graduate Committee: Douglas S. CairnsUnmanned Aircraft Systems (UAS) have become popular in the last decade. More than 1.5 million have been registered by the Federal Aviation Administration (FAA) since 2015. In order to understand the risk UAS pose to manned aircraft and make informed regulation decisions, the FAA has created air to air collision studies. As a part of the FAA general aviation air to air collision research, a Cessna 182 windscreen material model and a full scale impact testing facility were required. A Finite Element Crash Model of a Cessna 182 is in development as a part of the general aviation air to air collision research. The National Institute for Aviation Research at Wichita State University is managing development of the model. In support of that work, an LS-DYNA material model of the Poly(Methyl methacrylate) windscreen was developed. Results from tensile testing at multiple strain rates were used to develop material models using MAT_124 and MAT_187. A model of an impact tower was created to compare the material models to test results. The material models were tuned to better fit the impact tower test results. MAT_187 has more flexible material inputs, which allowed it to outperform MAT_124. A full scale impact testing facility was developed to support Finite Element model validation and direct testing of UAS to aircraft impact. A slingshot style launcher was designed and built to launch common quadcopter style UAS. Testing has shown that the launcher is capable of 120 knots with the accuracy required to repeatably hit the leading edge of a wing. Additionally, the launch site required a system for instrumented testing to compare experimental results with finite element results. A system was developed to allow flexible fixturing, impact speed and orientation measurement, and inclusion of load cells and strain gauges.Item Acoustic propagation modeling for marine hydrokinetic applications(Montana State University - Bozeman, College of Engineering, 2016) Johnson, Charles Nathan; Chairperson, Graduate Committee: Erick JohnsonThe combination of riverine, tidal, and wave energy have the potential to supply over one third of the United States' annual electricity demand [1]. However, in order to deploy and test prototypes and commercial installations, marine hydrokinetic (MHK) devices must meet strict regulatory guidelines. These regulations mandate the maximum amount of noise that can be generated and sets particular thresholds for determining disturbance and injury caused by noise. In the absence of measured levels from in-situ deployments, a model for predicting the propagation of a MHK source in a real hydroacoustic environment needs to be established. An accurate model for predicting the propagation of a MHK source(s) in a real-life hydro-acoustic environment has been established. This model will help promote the growth and viability of marine, water, and hydrokinetic energy by confidently assuring federal regulations are meet and harmful impacts to marine fish and wildlife are minimal. A 3D finite-difference solution to the governing velocity-pressure equations is presented and offers advantages over other acoustic propagation techniques for MHK applications as spatially varying sound speeds, bathymetry, and bed composition that form complex 3D interactions can be modeled. This solution method also allows for the inclusion of complex MHK sound spectra from turbines and/or arrays of turbines. A number of different cases for hydro-acoustic environments have been validated by both analytical and numerical results from canonical and benchmark problems. Several of these key validation cases are presented in order to show the applicability and viability of a finite difference numerical implementation code for predicting acoustic propagation in a hydro environment. With the model successfully validated for hydro-acoustic environments, more complex and realistic MHK sources from turbines and/or arrays can be modeled. A systematic investigation of MHK relevant scenarios is presented with increasing complexity including a single- and multi- source investigation, a random phase change study, and a hydro-acoustic model integrationItem Analysis of the metal cutting process using the shear plane model(Montana State University - Bozeman, College of Engineering, 2010) Chen, Cameron Kai-Ming; Chairperson, Graduate Committee: David A. MillerThe objective of the metal cutting process is to reshape a piece of metal, or workpiece, of initial geometry into a new geometry of desired shape. Although there are a variety of ways to cut metal, this study focuses on the type of cutting where metal is sheared away from the workpiece as is commonly done with machine tools such as the lathe or mill. Typically, the correct machine settings can be found from reference guides that summarize a great amount of empirical data on metal cutting. Trial and error when combined with experience, often suffices to select the proper process parameters. The aim of this study is to predict the outcome of a metal cutting process given the properties of the workpiece, feed and cutting speed in order to understand the cutting process and predict optimum conditions. The shear plane model is well known, having been developed in the early and mid-20th century. However the empirical nature of the model and approximations made in making predictions of the metal cutting process serve to limit the usefulness of this model. A calculation routine devised by P.L.B Oxley to predict how to cut steel was created with modifications allowing predictions of the metal cutting process with any metal. A comparative study was done with 1006 steel, 6Al-4V titanium, 2024-T3 aluminum and OFE copper regarding the differences in tool forces and temperatures that would result if each metal was cut with the same process. A quantitative prediction of the metal cutting process was made for the four metals under study. Although there is no experimental data with which to evaluate these predictions, a number of case studies were performed. These case studies involved the prediction of experimental data presented in literature from other laboratories. The metal cutting model presented here has great promise as a guide to predict the best machine tool parameters.