Master of Science, The Ohio State University, 2024, Aerospace Engineering

Various trailing-edge (TE) Coanda active flow control (AFC) actuator configurations were experimentally investigated in a propeller slipstream flow to simulate hover flight. This thesis will provide a comprehensive evaluation of the configuration factors—in terms of spanwise position and geometric parameters—which impact the aerodynamic and control authority performance of TE Coanda AFC actuators in propeller-driven flow with no freestream velocity. Two main types of TE Coanda AFC configuration experiments were conducted. The first type of testing involved varying the spanwise placement and size of TE AFC while maintaining constant internal geometry and circular Coanda profile shape with continuous slot blowing. The spanwise location testing's objectives were to determine the optimal Coanda AFC actuator location relative to the propeller slipstream and compare Coanda flow control effectiveness to that of a traditional deflection control surface. Two trailing-edge Coanda actuator sections of fixed spanwise length were designed, fabricated, and evaluated in terms of lift force and pitching moment generation at varying spanwise locations. Velocity profile measurements for this study for the case of no freestream flow indicated that the propeller slipstream is asymmetric over the NACA 0012 wing and contracts toward the side of the wing on which the propeller blade descends during rotation, where propeller downwash is experienced. This asymmetry indicated that there may be an optimum location for Coanda AFC actuators at the wing trailing edge which couple with momentum from the propeller in regions of peak slipstream velocity. The second type of testing involved varying TE AFC nozzle and surface profiles while maintaining constant spanwise location. These nozzles included both continuous and discrete slot blowing as well as sweeping jets. Surfaces investigated included circular, elliptical, and biconvex profiles. Each configuration was mounted to the trailing edge of (open full item for complete abstract)

Committee: Matthew McCrink (Committee Member); Jeffrey Bons (Advisor) Subjects: Aerospace Engineering

Doctor of Philosophy, University of Akron, 2021, Mechanical Engineering

A numerical tool chain for wake ingesting propeller applications was developed, validated and applied. The tool evaluates the propulsive properties of a propeller operating in the wake of an axisymmetric body at zero incidence. Two levels of numerical fidelity are compared; a high-fidelity, pseudo-transient model which includes modeling of the body with the full propeller geometry and a lower fidelity model which simplifies the propeller geometry into an infinitely thin actuator disk coupled with a full geometry of the upstream body. The open-source blade element code XROTOR has been used to calculate the radial distribution of circulation, induced velocities, thrust and power along a given propeller blade geometry applied to the actuator disk model. The code applies a lifting line solution modified for use with rotors and propellers. Aerodynamic characteristics required in computing radial thrust and drag for each blade airfoil section were estimated using the open-source panel method code XFOIL. The resulting values were applied as a discontinuous jump across a two-dimensional disk in a three-dimensional computation domain. The computational fluid dynamics code FLUENT was used to compute resulting flow field solutions of the three-dimensional domain for both models by solving the Reynolds-averaged Navier-Stokes (RANS) equations. The k-ω SST turbulence models were used and compared with the Transition SST, Intermittency and Three-Equation models which incorporate estimations for laminar to turbulent boundary layers. The analytical tool was validated by application to previously conducted wind tunnel testing of a scale airship operating with a stern mounted propeller. Boundary and operating conditions including turbulence intensities were considered and matched in both analytical approaches. Resulting propulsive, aerodynamic and flow field quantities were compared. The subsequent studies and design tool were applied to a design study for increasing propulsive e (open full item for complete abstract)

Committee: Nicholas Garafolo (Advisor); Minel Barun (Committee Member); Alex Hoover (Committee Member); Scott Sawyer (Committee Member); Alex Povitsky (Committee Member) Subjects: Aerospace Engineering; Fluid Dynamics; Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2024, Engineering

With the increasing interest in electric vertical takeoff and landing air vehicles and small-scale Unmanned Air Vehicles, many novel design concepts favor the fixed-pitch-propeller as the primary propulsion system due to its simplicity and reliability. This expands the application scenario of the fixed-pitch propeller from axial forward flight to edgewise flight conditions. The current study investigated the changes in its performance when operating at higher incidence angle conditions as well as the proximity effects of the propellers in these conditions. It is hypothesized that the propeller performance under various conditions and proximities can be reasonably predicted by modeling the changes in the inflow angle of the propeller. This hypothesis was tested using three major steps. First, a relationship between inflow angle, propeller inclination angle, and advance ratio was established using a series of experimental investigations. Second, this relationship was used to predict the performance of two propellers in tandem configuration with various horizontal and vertical offset distances. Third, the same model was used to predict the ceiling effect of the propeller at different incidence angles and advance ratios. All experiments were conducted at the University of Dayton Low-Speed Wind Tunnel (UD-LSWT) Laboratory under its open jet configuration. Force-based experiments, flow visualization as well as phase-locked Particle Image Velocimetry (PIV) experiments were conducted for all investigations. The changes in propeller performance at various flight conditions were quantified and several normalization methods were successfully employed indicating the predictability of various propeller forces and moments. A novel propeller axial thrust prediction model was proposed considering the propeller performance as a summation of propeller-like components and wing-like component, with an overall error of less than 8.3%. Flow visualization and PIV results confirmed the (open full item for complete abstract)

Committee: Sidaard Gunasekaran (Committee Chair); Michael OL (Committee Member); Markus Rumpfkeil (Committee Member); Aaron Altman (Committee Member) Subjects: Aerospace Engineering

Master of Science (M.S.), University of Dayton, 2024, Aerospace Engineering

Recent advancements in battery technology have led to an increase in the development of electric Vertical Takeoff and Landing (eVTOL) vehicles, typically using electrically-powered propellers to generate both lift and thrust. These vehicles typically operate in low-altitude, and limited-space conditions in urban environments. Unsteady flows from building wakes or atmospheric boundary layer effects raise concern to the stability of eVTOL-capable aircraft under normal operating conditions and during transition from vertical to forward flight and vice-versa in population dense areas. Although all types of unsteady flows have been studied for decades, little has been published on the influence of unsteady flow on a propeller-wing system. Understanding of this system is crucial to ensuring the safety of not only the passengers of these VTOL aircraft, but also the safety of the public. Investigation into powered wing response to streamwise gust encounters was conducted through various propeller locations, angles of attack, reduced frequencies, and thrust levels. All experiments were run at the University of Dayton Low Speed Wind Tunnel (UD-LSWT) in its open-jet configuration. The shuttering system downstream of the test section consists of a set of rotating louvers that change angle to effectively change the blockage ratio of the wind tunnel. Different louver angles and actuation frequencies provide different velocities and reduced frequencies. Particle Image Velocimetry (PIV) was conducted on the freestream flow during actuation of the louvers to spatially characterize the angle of attack variation throughout the test section. The results from PIV were used to determine the optimal testing location and wing size for the test article. The wing was designed to be modular, accepting a number of different propeller Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2024-2083 4 locations. Four total configurations were considered – (open full item for complete abstract)

Committee: Sidaard Gunasekaran (Committee Chair); Michael Mongin (Committee Member); Albert Medina (Committee Member); Markus Rumpfkeil (Committee Member) Subjects: Aerospace Engineering

Master of Engineering, Case Western Reserve University, 2022, EECS - System and Control Engineering

Quadcopter, also known as a drone, rotorcraft, or quadrotor, is a small-scale UAV used for various applications like photography, inspection, etc. Its composition contains two parts: reliable hardware and an effective control algorithm. To maximize its performance, developing a reliable control algorithm is essential. Also, while the quadcopter is facing the propellers failure, a proper solution for maintaining its stability is necessary. In this thesis, the proposed controller is designed based on Lyapunov analysis using a nested saturation algorithm. First, the dynamic model of the four-rotor quadcopter is obtained via a Lagrange approach. Then the proposed controller is designed, and a global stability analysis of the closed-loop system is presented. Next, the MATLAB simulations show that the controller can autonomously perform flying experiments of taking off and hovering. In the second part, the periodic solutions and equilibria for the situations that quadcopter lost one and two (opposing) propellers are introduced.

Committee: Wei Lin (Advisor); Kenneth Loparo (Committee Member); Vira Chankong (Committee Member) Subjects: Aerospace Engineering; Electrical Engineering; Experiments; Robotics; Systems Design; Systems Science

Master of Science (M.S.), University of Dayton, 2020, Aerospace Engineering

With the increased usage of propeller-driven unmanned-aerial-vehicles (UAV) in closed spaces such as caves, buildings, pipelines, etc. for photography, surveillance, and inspection, understanding the influence of the ground and ceiling on a remote-controlled (R/C) propeller is of the utmost importance. The flying characteristics of drones changes when an object or a ground plane is in its close proximity due to changes in its propeller performance. The changes in performance are due to the changes in the flow field around the propeller that occur due to ground proximity, which is also known as ground effect. Ground effect on lifting rotor performance has been studied theoretically and experimentally for decades. Historically, most investigations focus on helicopter rotors, which have high aspect ratio, lower pitch and rarely have spanwise twist. This research focuses on smaller size rotors, in particular, the thin-electric propeller which is used widely on small UAVs. The research considers parameter variations not broadly available in the literature such as propeller pitch, diameter, solidity, and blockage. In particular, extreme ground effect is considered, where the ratio of ground plane stand-off distance to propeller diameter is 0.1 or less. Moreover, the propeller is reversed, to examine the ceiling effect. Typically, the ground effect investigation is done with a ground plane that is big enough to be considered an infinite plane. In this research, both infinite plane and circular plates of similar diameter (or less) of the propeller are used as ground planes. Various circular plates with different diameter to propeller diameter ratios are used in the research representing different `blockage ratios'. The investigation gives insight into changes in propeller performance in proximity to fuselages of a given diameter in propeller-driven airplanes under pusher and puller configurations. All experiments were conducted on a thrust-stand built in-house (open full item for complete abstract)

Committee: Sidaard Gunasekaran (Advisor); Aaron Altman (Committee Member); Markus Rumpfkeil (Committee Member) Subjects: Aerospace Engineering

Doctor of Philosophy (PhD), Ohio University, 2019, Physics and Astronomy (Arts and Sciences)

In this dissertation, we study magnetic properties for systems on multiple dimensionalities, in the form of a bulk crystalline structure, a magnetic monolayer and a magnetic molecular propeller. We also study energy storage related topics by focusing on three co-solvents of Li-S battery electrolytes. First, we study low-temperature antiferromagnetic phases of chromium nitride, a magnetic semiconductor for which different experiments seem to disagree on fundamental features like room-temperature resistivity. Calculations regarding strain, elastic constants, and electronic and magnetic properties of defects are presented with the intent to clarify the disagrement in measurements. We also explore the characteristics of MnSe 2 , a two-dimensional monolayer ferromagnet recently reported to exhibit room temperature ferromagnetism and potential for tunability. We present calculations of magnetic and electronic structure with the inclusion of strain and point defects, as well as modelling the magnetic structure using a Heisenberg model to estimate changes in the Curie temperature under these perturbations. We also report calculations on an interface with the α-MnSe phase, which experiments report to enhance the magnetization of the system. First principles calculations are also utilized to study a magnetic molecular propeller, in order to analyze the possible mechanisms taking place during its rotation, as well as explaining the origin of the chiral rotation seen in experiments. Finally, density functional theory is also used to analyze the interactions between three fluorinated ethers and a Li anode when forming part of a Li-S battery electrolyte.

Committee: Sergio E. Ulloa (Advisor); Hugh Richardson (Committee Chair); Nancy Sandler (Committee Member); Arthur Smith (Committee Member); Walter Lambrecht (Committee Member) Subjects: Physics

MS, University of Cincinnati, 2014, Engineering and Applied Science: Aerospace Engineering

The aerospace industry is experiencing an ever increasing demand for cheaper, quieter, and more efficient propulsion systems. This demand has placed much pressure on engineers to further explore the uses of existing technology to levels that in times past did not seem possible, due to limited technology capabilities. One form of research that has re-gained much attention in the past couple decades is the use of propeller driven systems. Propellers are unique in the sense that they can be manipulated in many ways to fit the needs of a certain demand. The intention of this thesis is to use an experimental approach to expand on this line of thinking in the form of a single shaft, axially stack propeller system. This experimentation is intended to explore the propulsion effects of this said system. The experiment itself was run using two common R/C aircraft propellers mounted on a single shaft that was attached to an electric motor. The axial distance between the propellers was increased at each new stage of the experiment, during which downward force was monitored and recorded at designated RPM's of the motor. At each axial distance, as well as each RPM setting, the propellers were also adjusted to designated relative angles to one another. Overall, the experiment was broken down into three phases. The first phase used two propellers of equal diameter and pitch. The second phase used a smaller diameter propeller stacked on top of a larger diameter propeller, with each propeller having the same pitch. The third phase used a larger diameter propeller stacked on top of a smaller diameter propeller, once again with each propeller having the same pitch. For all three configurations, the relative angle between the propellers was varied from 0° to 135°, at increments of 45°. For the most part, the results of the experiment can most effectively be explained by the Actuator Disc Theory, seeing that the before mention third phase of the experiment per (open full item for complete abstract)

Committee: Shaaban Abdallah Ph.D. (Committee Chair); Ephraim Gutmark Ph.D. D.Sc. (Committee Member); Mark Turner Sc.D. (Committee Member) Subjects: Aerospace Materials

Master of Science in Engineering (MSEgr), Wright State University, 2012, Mechanical Engineering

Today's unmanned aerial vehicles are being utilized by numerous groups around the world for various missions. Most of the smaller vehicles that have been developed use commercially-off-the-shelf parts, and little information about the performance characteristics of the propulsion systems is available in the archival literature. In light of this, the aim of the present research was to determine the performance of various small-scale propellers in the 4.0 to 6.0 inch diameter range driven by an electric motor. An experimental test stand was designed and constructed in which the propeller/electric motor was mounted in a wind tunnel for both static and dynamic testing. Both static and dynamic results from the present experiment were compared to those from previous studies. For static testing, the coefficient of thrust, the coefficient of propeller power, and the overall efficiency, defined as the ratio of the propeller output power to the electrical input power, were plotted versus the propeller rotational speed. For dynamic testing, the rotational speed of the propeller was held constant at regular intervals while the freestream airspeed was increased from zero to the windmill state. The coefficient of thrust, the coefficient of power, the propeller efficiency and the overall efficiency were plotted versus the advance ratio for various rotational speeds. The thrust and torque were found to increase with rotational speed, propeller pitch and diameter, and decrease with airspeed. Using the present data and data from the archival and non-archival sources, it was found that the coefficient of thrust increases with propeller diameter for square propellers where D = P. The coefficient of thrust for a family of propellers (same manufacturer and application) was found to have a good correlation from static conditions to the windmill state. While the propeller efficiency was well correlated for this family of propellers, the goodness of fit parameter was improved by modifying t (open full item for complete abstract)

Committee: Scott K. Thomas PhD (Committee Chair); Haibo Dong PhD (Committee Member); Zifeng Yang PhD (Committee Member); Mitch Wolff PhD (Committee Member) Subjects: Aerospace Engineering; Engineering; Mechanical Engineering

Master of Science (MS), Ohio University, 2007, Electrical Engineering & Computer Science (Engineering and Technology)

This thesis presents an improvement in the performance of a three degrees of freedom differential thrust control testbed by considering the actuator dynamics. The testbed consists of three propellers that are used to produce thrust as well as attitude control for vertical takeoff and landing flight. Actuator dynamics consist of the motor-propeller dynamics and the nonlinear mapping relating the aerodynamic torques to the propeller speed. A previous controller was designed by neglecting the motor-propeller dynamics and the control allocation was done assuming a linear static relationship between aerodynamic torques and motor voltages. This work will determine the nonlinear control allocation mapping and model the motor-propeller dynamics as a first-order linear system. Simulation and real-time results showing an improvement in the performance of the testbed are presented by replacing the linear control allocation with nonlinear control allocation and by compensating for the motor-propeller dynamics. Further, the existing controller is redesigned considering the gyroscopic effects produced due to the spinning propellers.

Committee: Jianchao Zhu (Advisor) Subjects: