Engineering Commons^™

Dances And Escape Of The Vortex Quartet, Brandon Behring

Dissertations

This dissertation considers the linear stability of a one-parameter family of periodic solutions of the four-vortex problem known as 'leapfrogging' orbits. These solutions, which consist of two pairs of identical yet oppositely-signed vortices, were known to W. Gröbli (1877) and A. E. H. Love (1883) and can be parameterized by a dimensionless parameter related to the geometry of the initial configuration. Simulations by Acheson and numerical Floquet analysis by Tophøj and Aref both indicate, to many digits, that the bifurcation occurs at a value related to the inverse square of the golen ratio. Acheson observed that, after an initial period …

Design And Control Techniques Of The Open-Circuit Subsonic Wind Tunnel With Closed Testing Section, Jamshid Yakhshilikov, Jamshid Inoyatkhodjaev

Acta of Turin Polytechnic University in Tashkent

This paper will describe the design and control techniques of the open-circuit subsonic wind tunnel with closed testing section (WT) for study purpose. The goal is to design a WT that can be tested at a wind speed of 30 m/s, where the desired cross-sectional area of the test chamber is 0.5x0.5 m. The pressure drop inside the WT has been calculated in order to select one of the available axial fans from the manufacturer’s catalog, and computational fluid dynamics (CFD) was performed to check the result. In order to obtain a smooth airflow in the test section, a proportional …

Considerations For The Design Optimization Of Floating Offshore Wind Turbine Blades, Evan M. Gaertner

Doctoral Dissertations

Floating offshore wind turbines are an immature technology with relatively high costs and risk associated with deployment. Of the few floating wind turbine prototypes and demonstration projects deployed in real metocean conditions, all have used standard turbines design for onshore or offshore fixed bottom conditions. This neglects the unique unsteady aerodynamics brought on by floating support structure motion. While the floating platform has been designed and optimized for a given rotor, the global system is suboptimal due to the rotor operating in conditions outside of which it was design for. If the potential offered by floating wind turbines is to …

Entrainment Processes For A Jet In Cross-Flow: The Quantification Of Turbulent Contributions And Their Importance On Accurate Modeling, Graham Asher Freedland

Dissertations and Theses

A jet in cross flow (JICF) is examined experimentally by injecting a stream of air into crossing fluid with an aim into quantifying entrainment process and downstream evolution. The behavior of JICF is important to fields ranging from turbine-blade cooling to smokestack pollution and volcanic eruption dynamics. Existing simplified volcanic plume models are tested; most importantly, the near-field contributions of complex interconnected vortex systems, which present significant uncertainties because they assume negligible turbulence. While jets in irrotational cross-flow have been investigated, this analysis has focused on the interaction between a turbulent jet in low and highly turbulent cross-flow created by …

Experimental And Numerical Study Of Drag Reduction On Elliptical Cylinders Using Surface Grooves, Michael T. Brocker, David J. Mcdonell, Drake L. Pensworth, Joshua J. Swimm

Channels: Where Disciplines Meet

Drag reduction on an object subject to external flow remains a topic of interest due to a wide range of applications. Previous studies showed that grooves on the surface of a circular cylinder lead to drag reduction, which had thus been applied to save energy in various implementations. In the present study, the effects of longitudinal surface grooves with respect to drag reduction on circular and elliptical cylinders were experimentally explored through resin additive manufacturing and a wind tunnel. Significant drag reduction originated by surface grooves was observed. In conjunction with experimental investigations, numerical analyses were performed with computational fluid …

The Varied Thermal Response Of Magnetic Iron-Oxide Nanoparticles During Induction Heating In Liquid And Solid-Liquid Phase Change Mediums, Joshua Tompkins

Graduate Theses and Dissertations

This study investigates the induction heating response of uncapped iron oxide nanoparticles sonically dispersed as a nanofluid and mechanically distributed in solid phase change materials. The nanoparticles examined have a mean diameter of 14.42 nm and are magnetically heated in an alternating magnetic field at an amplitude of 72.6 kA/m at frequencies of 217, 303, and 397 kHz. Nanoparticle characterization was undertaken through transition electron microscopy, x-ray diffraction, and dynamic light scattering when in suspension. Carrier fluids were characterized through viscosity, heat capacity, and density measurements which were used in the calorimetric calculation of the specific absorption rate (SAR) of …

Optical Measurements Of Viscous Interactions On A Hollow-Cylinder / Flare In A Mach 4 Freestream, Jack William Cobourn

Masters Theses

Despite decades of research, shock-wave/boundary-layer interactions and laminar-turbulent transition remain uncertainties in the design of hypersonic vehicles. Due to the significant demand for hypersonic capabilities and the relevance of these flow physics to air-breathing, high-lift, hypersonic vehicles, continued study is necessary. In order to support such study at the University of Tennessee Space Institute, two optical diagnostics were investigated for use in the Mach 4 Ludwig tube at the Tennessee Aerothermal Laboratory, focused laser differential interferometry and schlieren. Significant attention was given to the theory behind and application of focused laser differential interferometry to support future work at the University …

Investigation Of Predicted Helicopter Rotorhub Drag And Wake Flow With Reduced Order Modeling, Tristan David Wall

Masters Theses

The rotor hub is one of the most important components of the modern helicopter. This complex collection of linkages and plates has numerous responsibilities, including the translation of pilot input to system response, anchoring the blades to the rotor mast, and sustaining the various forces transmitted by the blades. Due its intricate design and relatively small sized components the rotor hub interacts with the incoming flow to create a highly chaotic, turbulent wake which impinges on the fuselage and empennage. This assembly has also been found to be one of the primary contributors to the total vehicle parasite drag. Unfortunately …

An Experimental Investigation Of High-Speed Air-Breathing Vehicle Performance Metrics, Katherine M. Stamper

Masters Theses

High-speed air-breathing vehicles are one of the main hypersonic vehicles currently being developed. There is a current push by major world powers to develop these vehicles and one of the major limiting factors is engine design. The high-speed air-breathing vehicles necessitate an engine that can perform at higher speeds and higher temperatures, such as a scramjet. This engine is broken into three main parts: the inlet, isolator, and combustor. One of the primary concerns for these vehicles is engine unstart, which is when there is no longer supersonic flow through the engine and the engine can no longer perform. This …

Field Testing The Effects Of Low Reynolds Number On The Power Performance Of The Cal Poly Wind Power Research Center Small Wind Turbine, John B. Cunningham

Master's Theses

This thesis report investigates the effects of low Reynolds number on the power performance of a 3.74 m diameter horizontal axis wind turbine. The small wind turbine was field tested at the Cal Poly Wind Power Research Center to acquire its coefficient of performance, C­_p, vs. tip speed ratio, λ, characteristics. A description of both the wind turbine and test setup are provided. Data filtration and processing techniques were developed to ensure a valid method to analyze and characterize wind power measurements taken in a highly variable environment. The test results demonstrated a significant drop in the …

Hypersonic Heat Transfer Load Analysis In Star-Ccm+, Robert Comstock

Master's Theses

This thesis investigates the capabilities of STAR-CCM+, a Computational Fluid Dynamics (CFD) software owned by Siemens, in predicting hypersonic heat transfer loads on forward-facing surfaces. Results show that STAR-CCM+ predicted peak heat transfer loads within +/- 20% of experimental data on the leading edge of a delta wing design from the X-20 Dyna-Soar program with 73^o of sweep. Steady-state laminar simulations were run as replications of wind tunnel tests documented in NASA CR-535, a NASA technical report that measured and studied the hypersonic pressure and heat transfer loads on preliminary X- 20 wing designs across a wide range of …

Numerical Analysis Of A Circulation Control Wing, Luke W. Bodkin

Master's Theses

The objective of this thesis was to develop an experimental method to research circulation control wings using numerical analysis. Specifically, it is of interest to perform 3D wind tunnel testing on a circulation control wing in the Cal Poly Low Speed Wind Tunnel (CPLSWT). A circulation control wing was designed and analyzed to determine the feasibility of this testing.

This study relied on computational fluid dynamics (CFD) simulations as a method to predict the flow conditions that would be seen in a wind tunnel test. A CFD simulation was created of a wing model in a wind tunnel domain. Due …

Simulation Of Operational Extreme Wind Conditions For Horizontal Axis Wind Turbines Based On Iec Standard, Kamran Shirzadeh Ajirlo

Electronic Thesis and Dissertation Repository

The possibility of simulating deterministic extreme operational conditions for horizontal axis wind turbines based on the IEC 61400-1 standard in the WindEEE Dome at Western University was investigated. WindEEE has 60 fans (a matrix of 4 by 15 with 0.8m diameter each) on one of the walls to generate straight and sheared flows. These fans were controlled by their power set-points and by their adjustable Inlet Guiding Vanes (IGV) to generate the Extreme Operational Gust (EOG), positive and negative Extreme Vertical Shear (EVS), and Extreme Horizontal Shear (EHS) cases as per IEC 61400-1 standard to be further applied for testing …

Joint Wind And Ice Effects On Transmission Lines In Mountainous Terrain, Daniel Davalos Arriaga

Electronic Thesis and Dissertation Repository

Atmospheric icing on mountainous terrain can produce catastrophic damages to transmission lines when incoming particles impinge and accrete on the cable surface of the system. The first challenge in wind-ice loading is determining joint statistics of wind and ice accretion on transmission lines. This study analyzes the weather characteristics for a specific site of study using 15 years of historical data to use as inputs for ice accretion modeling. The joint wind and ice hazard is characterized by simulating 500 years of icing events from the fitted probability distributions of ice accretion and wind on ice velocities. The second challenge …

Characterization For Spray Droplet Behaviour In Afterburner-Like Flow Conditions, Matthew D. Mahaffy

Electronic Thesis and Dissertation Repository

Fuel injection processes can contribute to combustion instability in highly energetic combustion systems. In gas turbine engine afterburners, jet-in-crossflow (JIX) injection is used. Part one of the thesis study investigates the interaction between spray droplets and turbulent flow properties of a JIX. Jet-in-counterflow (JIC) configuration was also investigated. Part two of the investigation examined the behaviour of JIX droplets around a bluff body. Droplet size and flow turbulence was characterized simultaneously using particle image velocimetry and image processing techniques. Turbulence and droplet size were correlated, particularly at momentum flux ratios ≥ 60. High speed imaging was used to identify droplet …

Celebrating 90-Orbits Around The Sun, Stafford Air & Space Museum

Programs

In celebration of the 90th birthday of Oklahoma astronaut and aerospace legend, Gen. Thomas P. Stafford, the Stafford Air & Space Museum in Weatherford, Oklahoma is offering free admission on September 17th, 2020.

Unless stated otherwise within this repository collection, all materials are shared under the following Creative Commons license: [Creative Commons Attribution-NonCommercial 4.0 International License].

Resonant Triad Interactions In One And Two-Layer Systems, Malik Chabane

Dissertations

This dissertation is a study of the weakly nonlinear resonant interactions of a triad of gravity-capillary waves in systems of one and two fluid layers of arbitrary depth, in one and two-dimentions. For one-layer systems, resonant triad interactions of gravity-capillary waves are considered and a region where resonant triads can be always found is identified, in the two-dimensional wavevector angles-space. Then a description of the variations of resonant wavenumbers and wave frequencies over the resonance region is given. The amplitude equations correct to second order in wave slope are used to investigate special resonant triads that, providing their initial amplitude …

Studies Of Two-Phase Flow With Soluble Surfactant, Ryan Peter Atwater

Dissertations

Numerical methods are developed for accurate solution of two-phase flow in the zero Reynolds number limit of Stokes flow, when surfactant is present on a drop interface and in its bulk phase interior. The methods are designed to achieve high accuracy when the bulk Péclet number is large, or equivalently when the bulk phase surfactant has small diffusivity

In the limit of infinite bulk Péclet number the advection-diffusion equation that governs evolution of surfactant concentration in the bulk is singularly perturbed, indicating a separation of spatial scales. A hybrid numerical method based on a leading order asymptotic reduction in this …

Characterizing The Unsteady Dynamics Of Cylinder-Induced Shock Wave/Transitional Boundary Layer Interactions Using Non-Intrusive Diagnostics, Elizabeth Lara Lash

Doctoral Dissertations

The objectives of this study were to provide time-resolved (1) characterizations of shock wave/transitional boundary layer interactions using schlieren flow visualization, and (2) correlations of unsteady shock motion to boundary layer features. The characteristics of cylinder-induced shock wave/transitional boundary layer interactions in a Mach 2 freestream flowfield were studied experimentally. The Reynolds number in the Mach 2 facility was 30,000,000 m-1. Incoming boundary layers were in transitional and fully turbulent states. Characterizing the shock wave motion was based on tracking the position of the shock wave on the model surface in schlieren images. The motion of the shock waves revealed …

Aeroacoustics Of Supersonic Jet Interacting With Solid Surfaces And Its Suppression, Seyyed Saman Salehian

Doctoral Dissertations and Master's Theses

The noise generated by supersonic jet is of primary interest in the high-speed flight. In several flight conditions jet exhaust of the propulsion system interacts with solid surfaces. For example, jet impingement on ground for a rocket lift-off, or interactions influenced by the integration of the engine with the airframe. Such complex applications require consideration of the role of acoustic-surface interactions on the noise generation of the jet and its radiation. Numerical analysis of supersonic jet noise involved in these scenarios is investigated by employing Hybrid Large Eddy Simulation – Unsteady Reynolds Averaged Simulation approach to model turbulence.

First, the …

Dynamic Effects Of Inertial Particles On The Wake Recovery Of A Model Wind Turbine, Sarah E. Smith

Dissertations and Theses

Impacting particles such as rain, dust, and other debris can have devastating structural effects on wind turbines, but little is known about the interaction of such debris within turbine wakes. This study aims to characterize behavior of inertial particles within the turbulent wake of a wind turbine and relative effects on wake recovery. Here a model wind turbine is subjected to varied two-phase inflow conditions, with wind as the carrier fluid (Re_λ = 49 - 88) and polydisperse water droplets (26 to 45µm in diameter) at varied concentrations (Φ_v=0.24 x 10^-5 - 1.3 …

Droplet Ejections During Wet Lab Operations Aboard Spacecraft, Caleb Cushman Turner

Dissertations and Theses

The breakup and rupture of liquid bridges, thin films, bubbles, droplets, rivulets, and jets can produce satellite droplets that are subsequently ejected into their surrounding environment. For example, when any solid object is withdrawn from a liquid bath, the formation of an ever-thinning columnar liquid bridge eventually ruptures along the axis of the bridge. When rupture occurs under typical pipetting conditions the dynamics governing the rupture almost always produce at a minimum a satellite droplet. When these droplets occur they are often too small and too fast to be observed by the human eye. In a terrestrial environment they are …

Rotor-On-Rotor Aeroacoustic Interactions Of Multirotor In Hover, Eduardo Alvarez, Austin Schenk, Tyler Critchfield, Andrew Ning

Faculty Publications

Multirotor configurations introduce complicated aerodynamic and aeroacoustic interactions that must be considered during aircraft design. In this paper we explore two numerical methods to model the acoustic noise caused by aerodynamic rotor-on-rotor interactions of rotors in hover. The first method uses a conventional mesh-based unsteady Reynolds-average Navier-Stokes (URANS) solver, while the second consists of a meshless Lagrangian solver based on the viscous vortex particle method (VPM). Both methods are coupled with an aeroacoustics solver for tonal and broadband noise predictions. Noise predictions are validated for single and multi-rotor configurations, obtaining with the VPM a similar accuracy than URANS while being …

Narmax Identification Based Closed-Loop Control Of Flow Separation Over Naca 0015 Airfoil, Sohaib Obeid, Goodarz Ahmadi, Ratneshwar Jha

Henry M. Rowan College of Engineering Faculty Scholarship

A closed-loop control algorithm for the reduction of turbulent flow separation over NACA 0015 airfoil equipped with leading-edge synthetic jet actuators (SJAs) is presented. A system identification approach based on Nonlinear Auto-Regressive Moving Average with eXogenous inputs (NARMAX) technique was used to predict nonlinear dynamics of the fluid flow and for the design of the controller system. Numerical simulations based on URANS equations are performed at Reynolds number of 106 for various airfoil incidences with and without closed-loop control. The NARMAX model for flow over an airfoil is based on the static pressure data, and the synthetic jet actuator is …

Derivation And Exploration Of Analytical Aircraft Stability Analysis, Roderick Landreth

Honors Theses

A comprehensive measure of the in-flight stability of an aircraft is essential, though it can take a large amount of resources to do accurately and usefully. Small companies and colleges often don't have the resources to attain accurate experimental or analytical data to describe stable flight before potential failure. This composition investigates methods of completing a static and dynamic stability analysis for an aircraft feasible for a college, small business or hobbyist to complete, with the goal to eliminate the 'barrier of entry' concerning a lack of information and resources. A sample analytical calculation for static stability of Union College's …

A Study Of The Utilization Of Panel Method For Low Aspect Ratio Wing Analysis, William Barton D. Newey

Master's Theses

This study demonstrates the applicability of using a modified application strategy of panel method to analyze low aspect ratio wings at preliminary design phases. Conventional panel methods fail to capture the leading edge vortex (LEV) that is shed by wings with low aspect ratios, typically below 2 depending on planform. This aerodynamic phenomenon contributes to a significant amount of the lift of these wings and the result is a drastic underestimation of the lift characteristics when analyzed by conventional panel method. To capture the effect of the leading edge vortex, a panel method code was used with an extended definition …

A Parametric Study Of Formation Flight Of A Wing Based On Prandtl's Bell-Shaped Lift Distribution, Kyle S. Lukacovic

Master's Theses

The bell-shaped lift distribution (BSLD) wing design methodology advanced by Ludwig Prandtl in 1932 was proposed as providing the minimum induced drag. This study used this method as the basis to analyze its characteristics in two wing formation flight. Of specific interest are the potential efficiency savings and the optimal positioning for formation flight. Additional comparison is made between BSLD wings and bird flight in formation.

This study utilized Computational Flow Dynamics (CFD) simulations on a geometric modeling of a BSLD wing, the Prandtl-D glider. The results were validated by modified equations published by Prandtl, by CFD modeling published by …

Conceptual Design Of A South Pole Carrier Pigeon Uav, Kendrick M. Dlima

Master's Theses

Currently, the South Pole has a large data problem. It is estimated that 1.2 TB of data is being produced every day, but less than 500 GB of that data is being uploaded via aging satellites to researchers in other parts of the world. This requires those at the South Pole to analyze the data and carefully select the parts to send, possibly missing out on vital scientific information. The South Pole Carrier Pigeon will look to bridge this data gap.

The Carrier Pigeon will be a small unmanned aerial vehicle that will carry a 30 TB solid-state hard drive …

A Study Of The Design Of Adaptive Camber Winglets, Justin J. Rosescu

Master's Theses

A numerical study was conducted to determine the effect of changing the camber of a winglet on the efficiency of a wing in two distinct flight conditions. Camber was altered via a simple plain flap deflection in the winglet, which produced a constant camber change over the winglet span. Hinge points were located at 20%, 50% and 80% of the chord and the trailing edge was deflected between -5° and +5°. Analysis was performed using a combination of three-dimensional vortex lattice method and two-dimensional panel method to obtain aerodynamic forces for the entire wing, based on different winglet camber configurations. …

A Study Of The Standard Cirrus Wing Lift Distribution Versus Bell Shaped Lift Distribution, William H. Bergman

Master's Theses

This thesis discusses a comparison of the differences in aerodynamic performance of wings designed with elliptical and bell-shaped lift distributions. The method uses a Standard Cirrus sailplane wing with a lift distribution associated with the induced drag benefits of an elliptical distribution (span efficiency = 0.96) as the basis of comparison. The Standard Cirrus is a standard class sailplane with 15-meter wingspan that was designed by Schempp-Hirth in 1969. This sailplane wing was modeled and analyzed in XFLR5, then validated against existing wind tunnel airfoil data, and Standard Cirrus flight test data. The root bending moment of the baseline wing …