Aerodynamics and Fluid Mechanics Commons^™

On The Local Heat Transfer Behavior Of Supercritical Carbon Dioxide, Neil Sullivan

Doctoral Dissertations and Master's Theses

A detailed study of the local heat transfer behavior of supercritical carbon dioxide (sCO2) is performed. Flows relevant to heat transfer devices, such as sCO2 heaters, recuperators, and internally cooled turbine blades are studied, with particular attention paid to data reduction methodology, and the use of appropriate reference quantities, nondimensionalizations, and correlations. Additionally, a semi-intrusive temperature measurement technique capable of obtaining highly spatially resolved temperature distributions is adapted for use in the challenging conditions of supercritical (SC) flow. SC fluids have proven difficult to study both experimentally and numerically due to dramatically changing thermodynamic and transport properties near the critical …

Analysis Of A Non-Equilibrium Vortex Pair As Aircraft Trailing Vortices, Manuel Ayala

Mechanical & Aerospace Engineering Theses & Dissertations

Shortly after the roll-up evolution of the vortex sheet behind the wings of an aircraft, a coherent counter-rotating vortex pair emerges. Presence of this vortex pair in the downstream of an aircraft, creates unsafe conditions for other aircraft, especially near airport runways. Fundamental knowledge of the physics that govern the formation, duration and dissipation of aircraft wake vortices is desirable in order to improve aircraft operational safety. This study uses non-equilibrium pressure theory to develop an accurate model describing the physical behavior of the vortex pair created by an aircraft in the early to mid-field vortex regime. An isolated aircraft …

Fluid-Structure Interaction Of Nrel 5-Mw Wind Turbine, Mohamed Sayed Elkady Abd-Elhay

Theses and Dissertations

Wind energy is considered one of the major sources of renewable energy. Nowadays, wind turbine blades could exceed 100 m to maximize the generated power and minimize produced energy cost. Due to the enormous size of the wind turbines, the blades are subjected to failure by aerodynamics loads or instability issues. Also, the gravitational and centrifugal loads affect the wind turbine design because of the huge mass of the blades. Accordingly, wind turbine simulation became efficient in blade design to reduce the cost of its manufacturing. The fluid-structure interaction (FSI) is considered an effective way to study the turbine's behavior …

Bibliometric Analysis On Artificial Compressibility Method Based Cfd Simulations, Bhavna Hemraj Joshi Miss, Chandrakant R. Sonawane Dr, Priyambada Bada Praharaj Mrs, Anand Kumar Pandey Dr

Library Philosophy and Practice (e-journal)

This bibliometric analysis in this paper aims to study the quantitative progress done in the artificial compressibility (AC) method-based CFD simulation and analyze its potential in solving incompressible flow simulations in computational fluid dynamics smoothly. The sector of CFD is enhancing more and more maturely due to advancements in computing architecture, numerical methods, and simulation tools. There have been various attempts to solve the pressure-velocity coupling issue in the Navier-Stokes equation. The artificial compressibility method (ACM), as opposed to pressure-correction methods, solves the incompressible equation in a non-segregated manner. With the introduction of the ACM, the system of the equation …

A Flat Plate Skin Friction Correlation Including Transition, Jaret M. Wedow

Master's Theses

Many existing boundary layer models treat transition as a rapid switch from laminar to turbulent flow, with correlations defining properties in each respective region. Natural transition, however, is not always a very spanwise uniform process, with the onset of transition varying somewhat between different streamwise paths of fluid flow. Thus, a spanwise average of natural transition can result in a more gradual, extended transition region than many existing models predict. Modern applications, such as aircraft wings and fuselages, are extremely streamlined and smooth, allowing for natural transition to occur rather than flow tripping to turbulent near the leading edge. Under …

Analytical, Numerical, And Computational Methods To Analyze The Time To Empty Open, Closed, And Variable-Topped Inverted Bottles, Callen Schwefler

Master's Theses

Recent unexpected experimental observations of the emptying of inverted bottles with perforations has generated interest in modeling and simulation of this phenomenon. It was observed that as a perforation, i.e., a small hole at the "top" of the inverted bottle, is added and enlarged, the overall emptying time first increases to a maximum value and then decreases until it reaches a lower limit. The change in emptying time is associated with a transition from jetting, where only water exits the neck, to glugging, a competition between air and water flows at the neck of the bottle.

This paper develops analytical …

The Effect Of Fuel Injector Spacing, Angle, And Blowing Ratio On The Fuel Air Mixing Performance Of A Scramjet Engine, Jonathan R. Copeland

Honors College Theses

In the operation of a Scramjet engine, which operates at hypersonic velocities, one of the most important factors is mixing the fuel and air before the high velocity air stream through the engine blows the mixture out of the engine before it could burn. Because of the importance of rapidly mixing fuel and air within a Scramjet engine, there are multiple design elements used to increase mixing. One of which is called a flame holder cavity, which is usually located behind fuel injectors, and designed with an open (length to depth ratio is less than 10) geometry to promote recirculation …

Perfromance Improvement Of High Bypass Turbofan Engine Through Optimization Of High-Pressure Compressor Blade – A Case Study, Vlad Mandzyuk

Symposium of Student Scholars

This research determines the relation between the High-Pressure Compressor (HPC) blade characteristics, compressor pressure ratio, and lift-to-drag ratio of a high bypass turbofan engine. Alterations in the HPC blades airfoil, span, chord, taper ratio, twist, aspect ratio, sweep, and angle of incidence are performed and their effect on the engine’s performance is observed. The metrics used to compare engine performance include thrust, specific thrust, exit velocity, fuel/air ratio, power, and efficiency. Parametric cycle analysis and computational fluid dynamics are performed to compare and validate findings. The goal of this study is to optimize the design of HPC to maximize the …

Numerical Simulation Of Flow Past An Airfoil With Ice Accretion On Leading Edge, Boyu Wang

McKelvey School of Engineering Graduate Student Theses & Dissertations

The focus of this research is on aerodynamic simulation of flow past NACA 23012 airfoil with clean surface and with ice accretion on its leading edge by using the commercial CFD solver ANSYS Fluent. Reynolds-Averaged Navier-Stokes (RANS) computations are performed using Spalart-Allmaras (SA) and Wray-Agarwal (WA) turbulence models. ANSYS mesh package ICEM is used to model the geometry and generate the mesh. The computations are performed at 0, 2, 4, 6, 8, 10, and 12 degrees angle of attack which are compared with experimental data. For the case of ice accretion at the leading edge, the physical geometry becomes more …

Rehology And Electrical Conductivity Of Particulate Composites In Additive Manufacturing, Bin Xia

Mechanical Engineering Research Theses and Dissertations

Extrusion-based multi-functional additive manufacturing (AM) has been a rapidly developing area in AM recently. Particulate composites are widely used in this area to provide different functionalities with different types of particulate additives. However, there is no systematic understanding of the behavior of particulate composites during extrusion (especially in small nozzles) or of their properties once deposited in the build. This work investigates the properties of the type of particulate composites usually used in additive manufacturing, composed of a polymer matrix material and particulate additives within the micrometer scale. The focus is on the material rheology in the nozzle/capillary (for the …

Spatial Coherence Of Low-Frequency Unsteadiness Associated With A Normal Shock Wave, Matthew Cox, Phillip M. Ligrani, Kyle Goethals

PRC-Affiliated Research

The present data illustrate a unique analysis approach to explore the physics of shock-wave-flow interactions, based upon correlation and spectral analysis of digitized shadowgraph visualization time-sequence data. As such, demonstration is provided of the use of high resolution, flow visualization data for quantitative correlation and spectral analysis. A shadowgraph system is employed to visualize time-varying, shock wave flow features within the test section of one leg of the transonic/supersonic wind tunnel (which is also referred to as the SS/TS/WT or SuperSonic/TranSonic/WindTunnel), located within the Propulsion Research Center of the University of Alabama in Huntsville. Of interest is a flow field …

Spatial Coherence Of Low-Frequency Unsteadiness Associated With A Normal Shock Wave, Matthew Cox, Phillip M. Ligrani, Kyle Goethals

PRC-Affiliated Research

The present data illustrate a unique analysis approach to explore the physics of shock-wave-flow interactions, based upon correlation and spectral analysis of digitized shadowgraph visualization time-sequence data. As such, demonstration is provided of the use of high resolution, flow visualization data for quantitative correlation and spectral analysis. A shadowgraph system is employed to visualize time-varying, shock wave flow features within the test section of one leg of the transonic/supersonic wind tunnel (which is also referred to as the SS/TS/WT or SuperSonic/TranSonic/WindTunnel), located within the Propulsion Research Center of the University of Alabama in Huntsville. Of interest is a flow field …

On The Computational Efficiency Of Les And Hybrid Rans-Les Models In Building Aerodynamics, Aly Mousaad Aly, Faiaz Khaled

Faculty Publications

Large-eddy simulation (LES) has proven to offer superior accuracy in regards to predicting surface pressures compared to the Reynolds-averaged Navier Stokes (RANS) models. However, the primary impediment is the high computational cost associated with LES. The authors attempt to investigate the computational cost and accuracy by employing different sub-grid scale (SGS) models in LES and hybrid RANS-LES models. One of the prerequisites of accurate pressure estimations is to ensure a horizontally homogeneous empty computational domain. This study aims to compare the computational competence qualitatively and quantitatively using an empty domain in regards to the ability to maintain horizontal homogeneity. The …

Computational Investigation Of Perforated Plate Film Cooling Utilizing Conjugate Heat Transfer, Jonathan Sippel

Doctoral Dissertations and Master's Theses

The accuracy of modern state-of-practice computational fluid dynamics approaches in predicting the cooling effectiveness of a perforated plate film-cooling arrangement is evaluated in ANSYS Fluent. A numerical investigation is performed using the Reynolds Averaged Navier Stokes equations and compared to NASA Glenn’s available Turbulent Heat Flux 4 experimental measurements collected as a part of the Transformational Tools and Technologies Project. A multiphysics approach to model heat conduction through the solid geometry is shown to offer significant improvements in wall temperature and film effectiveness prediction accuracy over the standard adiabatic wall approach. Additionally, localized gradient-based grid adaption is analyzed using the …

Analysis Of Ship Airwakes Using Modal Decomposition, Nicholas Zhu

Doctoral Dissertations and Master's Theses

The three-dimensional, unsteady, and turbulent airwake produced by a scaled model of a generic Navy ship (Simple Frigate Shape No. 2) was investigated in a low-speed wind tunnel. Stereoscopic, time-resolved particle image velocimetry (TR-PIV) measurements were made at six different crosswise planes over the flight deck region of the ship model, with and without the effect of a simulated atmospheric boundary layer (ABL).

Spatiotemporal analyses of the TR-PIV measurements were performed using modal decomposition, and the modes were decomposed further based on the frequency contents of their time dynamics. This approach allowed an inspection of the individual scales of the …

On The Computational Efficiency Of Les And Hybrid Rans-Les Models In Building Aerodynamics, Faiaz Khaled, Aly Mousaad Aly

Faculty Publications

No abstract provided.

Analysis On Fuel Options For Scramjet Engines With The Study To Lower The Starting Mach Number, Sumantra Luitel, Gagan Dangi

Honors Theses

The main objectives of this report were to perform analysis of an ideal scramjet engine, to assess the influence of fuel on endurance factor, and the possibility of lowering the starting Mach Number of the scramjet. In the first part, an ideal cycle parametric analysis was conducted on three different fuels i.e. Liquid Hydrogen (LH2), Jet Propellant 7 (JP-7), and Rocket Propellant (RP-1), taking into account their availability, physical properties, current uses, and potential uses. The detailed analysis is done largely relying on a 9 step Parametric Cycle Analysis technique to study how fuel properties influence the variation of seven …

Foundations For The Coupled Inflow And Structural Dynamics Of Multi-Rotor Helicopters, Ethan Genter

McKelvey School of Engineering Graduate Student Theses & Dissertations

In this work, the Peters-Seidel finite-state model is expanded to calculate the coupled inflow and rotor dynamics of tandem rotor configurations. This establishes the foundation for a more complete multi-rotor, dynamic inflow model with finite-state methods. The derivation presented in this work is for the general case of two rotors in the same plane, overlapping and separated to varying degrees. It is the purpose of this work to study the unique and interesting dynamics and characteristics of various tandem systems heretofore not studied in a dynamic system. Moreover, it is the goal of this work to investigate how these systems …

Sensitivity And Estimation Of Aerodynamic, Propulsion, And Inertial Parameters For Rudderless Aircraft Using Simulation, Jaden W. Thurgood

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A technique known as system identification is often used in aircraft design and testing to understand and validate the mathematical parameters that describe the aircrafts stability and handling characteristics. System identification can be thought of as the inverse of simulation. In the world of system identification, we have a physical system that we seek to understand in more detail by monitoring the system with an array of sensors. In short, we conduct tests of an aircraft while recording the inputs and response outputs. Then we take the input and output data and run it through an algorithm that seeks to …

Mastering Uncoordinated Flight: Slips And Skids, Nihad E. Daidzic

Aviation Department Publications

FAA Safety Webinar (GL15103784) held online at 9:00 CST on Saturday, April 10, 2021.