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Item Small scale stimuli and the cricket cercal system(Montana State University - Bozeman, College of Agriculture, 2022) Mulder-Rosi, Jonas L.; Co-chairs, Graduate Committee: Charles M. Gray and R. Steven Stowers; This is a manuscript style paper that includes co-authored chapters.The cricket cercal system has been a model system in neuroscience for over 30 years. Anatomy, physiology, and theory have all come together to produce a picture of a system with a clear purpose: encoding air direction around the animal. However, certain features of the system have suggested that these cells may be sensitive to additional stimulus dimensions. To address this limited stimulus space I designed new experiments to test these neurons' responses to previously untested stimuli. I used a novel extracellular recording mechanism able to record and sort several neurons' responses at the same time. I built and tested several stimulators to provide small-scale puffs to specific parts of the sensory array at specific times. With these, I was able to test this model neural system against a complex stimulus space. I show here that these neurons respond to several additional stimulus dimensions. They are tuned to the timing of stimuli across the array. They show differential responses to even more complex stimuli with varying stimulus directions in different locations across the array. This implies that the previous understanding of the system was likely limited by how it was tested. While these cells accurately encode the direction of large-scale airflow, they also encode other aspects of stimuli, such stimulus timing and small-scale variations in stimulus direction. Thus the "function" of these neurons may be far more complex than previously understood.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 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 Toward the design and characterization of a dynamically similar artificial insect wing(Montana State University - Bozeman, College of Engineering, 2019) Reid, Heidi Elita; Chairperson, Graduate Committee: Mark JankauskiMicro air vehicles (MAVs) are a useful tool for numerous tasks, such as environmental mapping, search and rescue, and military reconnaissance. As MAV applications require them to operate at smaller and smaller length scales, traditional propulsion mechanisms (e.g. fixed wings, rotating propellers) cannot meet these demands. Conversely, flapping wing micro air vehicles (FWMAVs) can to realize flight at sub centimeter-lengths. However, FWMAVs face design challenges that preclude autonomous flight, including inefficient energetics and reliable on-board sensing. A comprehensive understanding of flying insect biomechanics may provide valuable design insights to help overcome the challenges experienced by FWMAVs. Insect wings have biological sensors that provide feedback to control attitude and wing deformation improves both inertial and aerodynamic power economy. Consequently, the insect wing can guide the design FWMAV-employed artificial insect wings. The present work aims to (1) dynamically characterize real insect wings via experimental modal analysis, and (2) develop dynamically similar artificial wings to be used on FWMAVs or in controlled studies. To our knowledge, no existing artificial insect wing models are isospectral and isomodal with respect to their biological counterparts. Isomodality and isospectrality imply they have identical frequency response functions and vibration mode shapes, and thus will deform similarly under realistic flapping conditions. We measured the frequency response function and vibration modes of fresh Manduca sexta forewings using an electrodynamic shaker and planar scanning vibrometer and estimated the wings' mass distribution via a cut-and-weigh procedure. Based upon our results, we designed and constructed the artificial wings using fused filament fabrication to print a polylactic acid vein structure, based upon the actual vein size and arrangement present in biological wings. Thin polymer films were manually layered over the vein structure and trimmed to fit the wing boundaries to produce a flat wing structure. We determined that the biological and artificial wings have nearly identical natural frequencies, damping ratios, gain, and shape for the first vibration mode. The second mode exhibited complex modal behavior previously unreported in literature, which likely has significant implications to flapping wing aerodynamics. We demonstrate the feasibility of fabricating economical, realistic artificial wings for robotic applications moving forward.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 Experiments on the relationship between shape and effectiveness for three-dimensional boundary layer trips at supersonic speeds(Montana State University - Bozeman, College of Engineering, 1988) Berger, Stephen Edward