Aerospace Engineering Commons^™

Effects Of Pressure Side Film Cooling Hole Placement And Condition On Surface Heat Transfer Characteristics Of A Transonic Turbine Blade Tip, Hallie Collopy, Phillip M. Ligrani, Hongzhou Xu, Michael Fox

PRC-Affiliated Research

The effects of film cooling hole placement location along the upper pressure side of a transonic squealer are considered. The thermal performance of four different film cooling configurations; B1, B2, B3 and B4, are considered using the University of Alabama in Huntsville's SS/TS/WT (supersonic/transonic/wind tunnel) experimental facility and a simulated turbine blade row using a linear cascade. Surface-varying results are provided for both the squealer blade tip surface, and for the upper pressure side of the squealer blade. These results are given for blowing ratios ranging from 0.42 to 3.20 in the form of spatially-resolved and spatially-averaged adiabatic film cooling …

Noise And Propulsive Efficiency Interactions For Rotors And Propellers At Constant Thrust, Riccardo Roiati Mr.

Doctoral Dissertations and Master's Theses

In the emerging market of Advanced Air Mobility (AAM), aerospace companies have been designing and prototyping electric and hybrid vehicles to revolutionize travel. These vehicles must have low noise and particulate emissions while also having enough propulsive efficiency to complete the mission. This thesis aims to study the relationship between noise and propulsive efficiency as related to any aircraft equipped with an electric motor and a variable pitch rotor/propeller. The combination of the electric motor with the variable pitch propeller/rotor allows for a decoupled rotational speed and torque generation, meaning that the electric motor can generate the same amount of …

Quasi 1d Modelling Of A Scramjet Engine Cycle Using Heiser-Pratt Approach, Asmaa Chakir

Theses and Dissertations

Scramjet engines are key for sustained hypersonic flights. Analytic models play a critical role in the preliminary design of a scramjet engine configuration. The objective of this research is to develop and validate a quasi-1D model for the scramjet engine encompassing inlet, isolator and combustor, to evaluate the impact of flight conditions and design parameters on the engine functionality. The model is developed assuming isentropic flow in the inlet with a single turn; modified Fanno-flow equations in the isolator that account for the area change of the core flow; and the combustor is modeled using Heiser-Pratt equations accounting for the …

Development And Deployment Of A Dynamic Soaring Capable Uav Using Reinforcement Learning, Jacob Adamski

Doctoral Dissertations and Master's Theses

Dynamic soaring (DS) is a bio-inspired flight maneuver in which energy can be gained by flying through regions of vertical wind gradient such as the wind shear layer. With reinforcement learning (RL), a fixed wing unmanned aerial vehicle (UAV) can be trained to perform DS maneuvers optimally for a variety of wind shear conditions. To accomplish this task, a 6-degreesof- freedom (6DoF) flight simulation environment in MATLAB and Simulink has been developed which is based upon an off-the-shelf unmanned aerobatic glider. A combination of high-fidelity Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) in ANSYS Fluent and low-fidelity vortex lattice (VLM) …

Commercial Airliner Winglet Design Optimization – A Case Study, Anthony Gutierrez

Symposium of Student Scholars

The objective of this research is to determine the effect on aerodynamic performance due to changes of winglets design variables found of the Boeing 737-700 aircraft. The various winglet types studied in this research include the blended, canted, wingtip fence and split scimitar. The variables include height, sweep angle, taper ratio, and the inclination angle. These variables are altered in 5% increments from -15% to +15% of their original baseline values. Each altered winglet design only changes one variable at a time while keeping all other variables constant. The altered models are compared to the original by finding the aerodynamic …

Towards Reduced-Order Model Accelerated Optimization For Aerodynamic Design, Andrew L. Kaminsky

Doctoral Dissertations

The adoption of mathematically formal simulation-based optimization approaches within aerodynamic design depends upon a delicate balance of affordability and accessibility. Techniques are needed to accelerate the simulation-based optimization process, but they must remain approachable enough for the implementation time to not eliminate the cost savings or act as a barrier to adoption.

This dissertation introduces a reduced-order model technique for accelerating fixed-point iterative solvers (e.g. such as those employed to solve primal equations, sensitivity equations, design equations, and their combination). The reduced-order model-based acceleration technique collects snapshots of early iteration (pre-convergent) solutions and residuals and then uses them to project …

Feasibility Study Of Slotted, Natural-Laminar-Flow Airfoils For High-Lift Applications, Hector David Ortiz Melendez

Doctoral Dissertations

A computational fluid dynamics approach to evaluate the feasibility of a slotted, natural-laminar-flow airfoil designed for transonic applications, to perform as a high-lift system was developed. Reynolds-Averaged Navier-Stokes equations with a laminar-turbulent transition model for subsonic flow at representative flight conditions were used for this analysis. Baseline high-lift simulations were performed to understand the stall characteristics of the slotted, natural-laminar-flow airfoil. Maximum aerodynamic efficiency was observed with a constant slot-width. In addition, the effectiveness of the aft-element as a high-lift device was explored. Results indicate that a micro-flap is a viable option as a lift effector. These are most effective …

Computational Fluid Dynamics Modeling Of Hemodialysis In Patients With An Arteriovenous Fistula, Maximilian Roth

McKelvey School of Engineering Theses & Dissertations

With the advent of arteriovenous fistula (AVF) for use in hemodialysis, the anastomosis built for such use has become a central point of the study to understand the flow and wall shear stresses in such a system since very large wall shear stresses can lead to arterial/vein rupture. Considering the commonly used creation site of an anastomosis as connecting the radial artery to the cephalic vein, a model is created to calculate the wall shear stresses across various components of the system. The model depicts a connection of the specified vein and artery bridged together allowing the increase in blood …

Validation And Verification Of The Wray-Agarwal Turbulence And Algebraic Transition Models For 2d External Airfoil Flows, Dean Ryan-Simmons

McKelvey School of Engineering Theses & Dissertations

Validation and verification benchmark test cases are employed in computational fluid dynamics (CFD) to determine the best practices in application of various CFD tools. These cases focus on the geometry modeling, mesh generation, numerical algorithms, and turbulence models to ensure consistent and accurate numerical simulation of physical phenomena. Assessing model accuracy is essential to identify areas of improvement in various turbulence models. Flow past several symmetric NACA airfoils, namely NACA 0012, NACA 0015 and NACA 0018 are standard test cases for validating and evaluating turbulence models’ accuracy since the experimental data is available for these airfoils. Available wind tunnel data …

Machine Learning In Aerodynamic Shape Optimization, Jichao Li, Xiaosong Du, Joaquim R.R.A. Martins

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Machine learning (ML) has been increasingly used to aid aerodynamic shape optimization (ASO), thanks to the availability of aerodynamic data and continued developments in deep learning. We review the applications of ML in ASO to date and provide a perspective on the state-of-the-art and future directions. We first introduce conventional ASO and current challenges. Next, we introduce ML fundamentals and detail ML algorithms that have been successful in ASO. Then, we review ML applications to ASO addressing three aspects: compact geometric design space, fast aerodynamic analysis, and efficient optimization architecture. In addition to providing a comprehensive summary of the research, …

Understanding Unsteady Corner Separation Within Wing-Body Junction Flows, Paul G. Winner

Doctoral Dissertations and Master's Theses

Wing-body junction flows, formed at the interface between a wing and fuselage surface, are a complex, coupled, three-dimensional, turbulent flow field. This thesis focused on the unsteady corner separation that develops at the trailing edge of this wing-body junction under certain conditions. A NACA 0015 wing mounted on a flat plate at an angle of attack of 13°was used as the model junction flow field. The wing had an aspect ratio of 8 with a linear washout twist of 15°. The Reynolds number based on the wing chord was Re_c = 4.5 × 10⁵. Time-dependent stereoscopic particle …

A Data Driven Modeling Approach For Store Distributed Load And Trajectory Prediction, Nicholas Peters

Doctoral Dissertations and Master's Theses

The task of achieving successful store separation from aircraft and spacecraft has historically been and continues to be, a critical issue for the aerospace industry. Whether it be from store-on-store wake interactions, store-parent body interactions or free stream turbulence, a failed case of store separation poses a serious risk to aircraft operators. Cases of failed store separation do not simply imply missing an intended target, but also bring the risk of collision with, and destruction of, the parent body vehicle. Given this risk, numerous well-tested procedures have been developed to help analyze store separation within the safe confines of wind …

A Study Of Ship Airwakes Using Dual Plane Stereoscopic Piv, Guillermo Mazzilli

Doctoral Dissertations and Master's Theses

The airwake of a model Simple Frigate Shape 2 (SFS2) was studied in a low-speed wind tunnel. This airwake was measured using a novel time-dependent, dual plane, stereoscopic particle image velocimetry approach. Two flow planes over the flight deck, one parallel and one perpendicular to the free-stream were simultaneously measured. Measurements were carried out over four such pairs of streamwise-spanwise plane combinations. Additionally, the airwake with and without a simulated atmospheric boundary layer (sABL) was studied. The synchronicity of the measurements were taken advantage of to carry out conditional averages of the flow field to isolate and study certain flow …

Development Of A Trailing Edge Flap Using A Compliant Mechanism, Matthew Maybee

Summer Community of Scholars Posters (RCEU and HCR Combined Programs)

No abstract provided.

Low-Reynolds-Number Locomotion Via Reinforcement Learning, Yuexin Liu

Dissertations

This dissertation summarizes computational results from applying reinforcement learning and deep neural network to the designs of artificial microswimmers in the inertialess regime, where the viscous dissipation in the surrounding fluid environment dominates and the swimmer’s inertia is completely negligible. In particular, works in this dissertation consist of four interrelated studies of the design of microswimmers for different tasks: (1) a one-dimensional microswimmer in free-space that moves towards the target via translation, (2) a one-dimensional microswimmer in a periodic domain that rotates to reach the target, (3) a two-dimensional microswimmer that switches gaits to navigate to the designated targets in …

Comprehensive Review Of Heat Transfer Correlations Of Supercritical Co2 In Straight Tubes Near The Critical Point: A Historical Perspective, Nicholas C. Lopes, Yang Chao, Vinusha Dasarla, Neil P. Sullivan, Mark Ricklick, Sandra Boetcher

Publications

An exhaustive review was undertaken to assemble all available correlations for supercritical CO2 in straight, round tubes of any orientation with special attention paid to how the wildly varying fluid properties near the critical point are handled. The assemblage of correlations, and subsequent discussion, is presented from a historical perspective, starting from pioneering work on the topic in the 1950s to the modern day. Despite the growing sophistication of sCO2 heat transfer correlations, modern correlations are still only generally applicable over a relatively small range of operating conditions, and there has not been a substantial increase in predictive capabilities. Recently, …

Application Of Tensile Testing Machine For Measurement Of Skin Friction Coefficient, Jeremy Silver-Mahr

Undergraduate Student Research Internships Conference

Traditionally fluid drag associated with skin friction is conducted by the measurement of constrained fluid flow across a textured surface. This works well for easy-to-handle fluids such as water and oil, however it is less feasible for fluids such as liquid metals. A device that measures the drag force on a surface through a static fluid would allow for different fluid types and sample geometries to be tested. A fish scale pattern consisted of overlapping repeating circular planes 3mm in diameter angled to achieve 0.14mm of depth was embossed onto a PMMA sheet. A control sample of smooth PMMA was …

Experiments To Mitigate Flow Recirculation In A Closed Anechoic Chamber Using Mesh Screens As Turbulence Suppressors, Tori Kay Wolverton

Theses and Dissertations

The desire to gather acoustic data of a propeller in simulated hover without environmental effects is met with the challenge of recirculating flow in a closed anechoic chamber. Flow recirculation in an anechoic chamber is not ideal because the effects of it being ingested by the rotor cause unsteady loadings on the propeller. This unsteady loading causes vortex noise from the turbulence introduced by the recirculation of the flow. The aim is to study the acoustic signature of a propeller separate from external factors and engine noise. Two different propellers with three different screen combinations were tested in a closed …

Predictive Capabilities Of Laminar-Turbulent Transition Models For Aerodynamics Applications, Jared Alexander Carnes

Doctoral Dissertations

Laminar-turbulent boundary-layer transition has a demonstrable impact on the performance of aerospace vehicles. The ability to accurately predict transition is integral to properly capturing relevant flow physics. Traditionally, computational fluid dynamics simulations are performed fully turbulent, meaning that laminar flow is neglected. This, however, can result in errant predictions of vehicle performance as quantities such as skin-friction drag may be overpredicted. Resultingly, development of Reynolds-averaged Navier-Stokes transition models has seen significant attention over the last decades in order to model transition and realize the performance improvements of laminar flow.

In this work, the behaviors of several different transition-prediction methods are …

Aerodynamics And Vibrations Of A Helicopter Rotor Blade, Mohammad Khairul Habib Pulok

University of New Orleans Theses and Dissertations

The nature of the aerodynamic environment surrounding a helicopter causes a significant amount of vibration to its whole body. Among different sources of vibrations, the aerodynamic loading on the main rotor blade is the major contributor. Therefore, analyzing a rotor blade's vibration characteristics and aerodynamic behavior becomes essential. The vortex characteristics and the wake surrounding a helicopter rotor blade play an important role because they affect the aerodynamic behavior of the rotor blade. An advanced mathematical and computational model of rotor wake and blade vortex gives a better understanding of the helicopter rotor dynamics. This study develops computational models of …

Controller Platform Design And Demonstration For An Electric Aircraft Propulsion Driv, Rosten Sweeting

Graduate Theses and Dissertations

With the growth in the aerospace industry there has been a trend to optimize the performance of an aircraft by reducing fuel consumption and operational cost. Recent advancements in the field of power electronics have pushed towards the concepts of hybrid electric aircraft also known as more electrical aircrafts. In this work, a custom controller board for an electric aircraft propulsion drive was designed to drive a permanent magnet synchronous motor. Design of the controller board required knowledge of the topology selection and power module selections. Simulations of the system were performed using MATLAB/Simulink to analyze the overall performance of …

Foundations For Finite-State Modelling Of A Two-Dimensional Airfoil That Reverses Direction, Jake Michael Oscar Welsh

McKelvey School of Engineering Theses & Dissertations

Current 3-D finite-state wake models are incapable of simulating a maneuver in which the sign of the free-stream velocity changes direction and the rotor enters its own wake -- as might occur in the case of a helicopter which ascends and then descends. It is the purpose of this work to create a 2-D finite-state wake model which is capable of handling changes in free-stream direction as a precursor to development of a 3-D model that can do the same.

The 2-D finite-state model used for reentry modifications is an existing model created by Peters, Johnson, and Karunamoorthy. By the …

Upscaling And Development Of Linear Array Focused Laser Differential Interferometry For Simultaneous 1d Velocimetry And Spectral Profiling In High-Speed Flows, Kirk Davenport

Masters Theses

In this research a new configuration of linear array-focused laser differential interferometry (LA-FLDI) is described. This measurement expands on previous implementations of LA-FLDI through the use of an additional Wollaston prism. This additional prism expands the typical single LA-FLDI column into two columns of FLDI point pairs. The additional column of probed locations allows for increased spatial sampling of frequency spectra as well as the addition of simultaneous wall normal velocimetry measurements. The new configuration is used to measure the velocity profile and frequency content across a Mach 2 turbulent boundary layer at six wall normal locations simultaneously. Features of …

Studies Of Multiphase Distribution And Flow In Bubble/ Slurry Bubble Columns With /Without Internals And Advanced Sustainable Construction Materials Using Sophisticated Measurement Techniques, Omar Farid

Doctoral Dissertations

"Bubble/slurry bubble columns have been widely studied and employed as multiphase flow reactors with and without vertical heat-exchanging tubes. In order to understand more deeply the effect of the dense internals on the hydrodynamics of bubble/slurry bubble column, systematic experiments were performed to visualize and quantify using the radioactive particle tracking (RPT) technique. A new methodology for implementing the radioactive particle tracking (RPT) technique has been developed to investigate the effect of the dense internals on the hydrodynamics of the bubble/slurry column reactor. Monte Carlo N-Particle (MCNP) simulation has been implemented to simulate the system to generate a large number …

Analysis Of Turbulent Flow Behavior In Helicopter Rotor Hub Wakes, Forrest Mobley

Masters Theses

The rotor hub is one of the most important features of all helicopters, as it provides the pilot a means for controlling the vehicle by changing the characteristics of the main and tail rotors. The hub also provides a structural foundation for the rotors and allows for the rotor blades to respond to aerodynamic forces while maintaining controllability and stability. Due to the inherent geometry and high rate of rotation, the rotor hub in its current form acts a large bluff body and is the primary source of parasite drag on the helicopter, despite its relatively small size. The rotor …

Proper Orthogonal Decomposition Of Reynolds And Dispersive Stresses In Turbulent Boundary Layers Over Multi-Scale Rough Patches, Catherine Virginia Spivey

Dissertations and Theses

Multi-scale rough patches are present in topologies such as urban canopies (cities) and natural landscapes (forests, ocean floors). The flow over such canopies is three-dimensional, with turbulent structures known as secondary flows present in the boundary layer due to the difference in rough surface heterogeneities. Three dimensional instantaneous velocities are analyzed within the roughness sublayer over three generations of multi-scale rough patches at nine vertical planes using particle image velocimetry obtained experimentally. The secondary structures present in the flow are identified in the form of Reynolds and dispersive fluctuations. Proper orthogonal decomposition is employed to characterize the imprint of the …

Exploring Passive Flow Control Techniques Applied To A Supersonic Multistream Rectangular Nozzle, Emma Dawn Gist

Dissertations - ALL

Passive control techniques are applied experimentally to examine different aspects of a supersonic multistream rectangular nozzle representing a modern airframe-integrated variable cycle engine. The flow is comprised of a core stream (M = 1.6) and bypass (M = 1.0) that merge behind a splitter plate and exit through a Single Expansion Ramp Nozzle (SERN) onto an aft-deck. Previous efforts for the nominal nozzle configuration have shown that an instability initiated at the splitter plate trailing edge (SPTE) influences the effectiveness of the third stream as a barrier for the aft-deck and persists through the entire do- main due to its …

Experimental Characterization Of Additively Manufactured Multi-Feather Wingtip Devices, Patricio Garzon

Doctoral Dissertations and Master's Theses

Soaring birds have evolved to fly for long periods of time without flapping their wings. Inspired by the flight of these birds, the proposed thesis presents an experimental investigation focused on wingtip devices designed based on biomimicry. The overarching engineering objective was to reduce the induced drag as a means to improve the fuel efficiency via these experimental wingtips. An associated secondary objective was to establish a method for manufacturing complex structures suitable for wing tunnel testing. A manufacturing technique that involved using composite weaves to reinforce additively manufactured structures was developed. This technique has the potential to reduce manufacturing …

Sources Of Resonant Vortices In Aero-Acoustics Resonance From Tandem Flat Plates, Atef El Khatib, Ahmad Al Miaari, Ali Hammoud

BAU Journal - Science and Technology

Aero-acoustic resonance in flows around flat plates is a major design concern in various practical applications, especially turbomachinery and heat exchangers, due to its significant effects on fatigue rates and radiated noises intensity. Although research has been intensive on the topic, there is still a lot to be understood for effective resonance prediction and control. Resonance in tandem plate systems is characterized by a double response. This study, investigates for the first time, the flow mechanisms responsible for the generation of low-velocity and high-velocity resonances of the double resonance response. Experimental testing and numerical simulation showed that low-velocity resonance vortices …

Structural Dynamics Of Awt-27 Wind Turbine Blade, Amr Ismaiel

Future Engineering Journal

Wind energy is one of the world’s current leading renewable energy resources. One of the major aspects of studying wind turbines is the structural dynamics for the turbine structure including blades and support structure. In the current work, the blades of the Advanced Wind Turbine (AWT-27) are investigated in a dynamic approach. Different wind fields have been generated for the study to provide different Design Load Conditions (DLCs). Three laminar wind velocities of 5 m/s, 12 m/s, and 17 m/s were simulated. Turbulent wind flow fields have also been generated at the three standard classes A, B and C of …