Engineering Commons^™

Identification Of Hydrodynamic Forces Developed By Flapping Fins In A Watercraft Propulsion Flow Field, Erdem Aktosun

University of New Orleans Theses and Dissertations

In this work, the data analysis of oscillating flapping fins is conducted for mathematical model. Data points of heave and surge force obtained by the CFD (Computational Fluid Dynamics) for different geometrical kinds of flapping fins. The fin undergoes a combination of vertical and angular oscillatory motion, while travelling at constant forward speed. The surge thrust and heave lift are generated by the combined motion of the flapping fins, especially due to the carrier vehicle’s heave and pitch motion will be investigated to acquire system identification with CFD data available while the fin pitching motion is selected as a function …

Wind And Thermal Effects On Ground Mounted Photovoltaic (Pv) Panels, Chowdhury Mohammad Jubayer

Electronic Thesis and Dissertation Repository

A combination of Computational Fluid Dynamics (CFD) simulations and wind tunnel experiments are carried out to investigate the effects of wind on the aerodynamic loading and heat transfer of a ground mounted stand-alone photovoltaic (PV) panel with tilt angle of 25^o in open country atmospheric boundary layer. Several azimuthal wind directions are considered: Southern 0^o, Southwest 45^o, Northwest 135^o and Northern 180^o. Three dimensional Reynolds-Averaged Navier-Stokes (RANS) approaches with an unsteady solver using Shear Stress Transport (SST) k-ω turbulence closure are employed for the CFD simulations, whereas Particle Image Velocimetry (PIV) and …

Helical Models Of The Bidirectional Vortex In A Conical Geometry, Timothy Andrew Barber

Doctoral Dissertations

This dissertation represents the descriptive and analytical breakdown of two new fluid dynamics solutions for vortex motion. Both solutions model the bidirectional vortex within a conical geometry. The first explored solution satisfies a simple Beltramian characteristic, where the Lamb vector is identically zero. The second solution is of the generalized Beltramian type, which fulfills the condition that the curl of the Lamb vector is equal to zero. The two Beltramian solutions describe the axisymmetric, double helical motion often found in industrial cyclone separators. Other applications include cone-shaped, vortex-driven combustion chambers and the swirling flow through conical devices. Both solutions are …

Stability Of Particle-Mean Flow Interactions In Solid And Hybrid Rockets, Trevor Sterling Elliott

Doctoral Dissertations

Combustion instabilities associated with rocket motors as a result of unsteady components in the combustion chamber flow have been known to cause pressure oscillations. These pressure oscillations can result in changes to flight characteristics and vibrations translated to the rocket or payload. The unsteady components are comprised of two subcomponents, the vortico-acoustic fluctuations and the hydrodynamic fluctuations. As the vortico-acoustic fluctuations have been investigated in an exhaustive manner this work will focus on the hydrodynamic fluctuations. It has been known that the addition of particles increases specific impulse due to the resulting increase in combustion temperature and mass flow. They …

Design And Dynamic Analysis Of A Variable-Sweep, Variable-Span Morphing Uav, Nirmit Prabhakar

Doctoral Dissertations and Master's Theses

Morphing wings have the potential to optimize UAV performance for a variety of flight conditions and maneuvers. The ability to vary both the wing sweep and span can enable maximum performance for a diverse range of flight regimes. For example, low-speed missions can be optimized using a wing with high aspect ratio and no wing sweep whereas high-speed missions are optimized with low aspect ratio wings and large wing sweep. Different static morphing wing configurations clearly result in varying aerodynamics and, as a result, varying dynamic modes. Another important consideration, however, is the transient dynamics that occur when transitioning between …

Mitigation Of Moving Shocks In An Expanding Duct, Veraun Chipman

UNLV Theses, Dissertations, Professional Papers, and Capstones

Inviscid flow theory governs the bulk motion of a gas at some distance away from the walls (i.e. outside the boundary layer). That is to say, there are no viscous forces in the bulk flow, which is modeled using the Euler equations. The Euler equations are simply the Navier-Stokes equations with zero viscosity terms. An ideal inviscid fluid, when brought into contact with a surface or wall, would naturally slip right past it since the fluid has no viscosity. In real life, however, a thin boundary layer forms between the wall or surface and the bulk flow. Shock wave boundary …

Cold Flow Performance Of A Ramjet Engine, Harrison G. Sykes

Master's Theses

The design process and construction of the initial modular ramjet attachment to the Cal Poly supersonic wind tunnel is presented. The design of a modular inlet, combustor, and nozzle are studied in depth with the intentions of testing in the modular ramjet. The efforts undertaken to characterize the Cal Poly supersonic wind tunnel and the individual component testing of this attachment are also discussed. The data gathered will be used as a base model for future expansion of the ramjet facility and eventual hot fire testing of the initial components. Modularity of the inlet, combustion chamber, and nozzle will allow …

Achieving Global Range In Future Subsonic And Supersonic Airplanes, Nihad E. Daidzic Ph.D., Sc.D.

International Journal of Aviation, Aeronautics, and Aerospace

No commercial airplane in service today is able to fly half great-circle distances over the globe and achieve the non-stop or the global range to any antipodal location on Earth. A subsonic jetliner has the optimum cruising speed at Mach numbers approaching the drag divergence Mach number while still preserving relatively high aerodynamic efficiency. Various fuel-flow laws were used to investigate the cruise performance of subsonic and supersonic aircraft. The effect of wind and aircraft weight and how it affects the optimal cruising airspeed was investigated. Of all different operational cruising techniques, the cruise-climb at high Mach numbers is the …

Modeling Dynamic Stall For A Free Vortex Wake Model Of A Floating Offshore Wind Turbine, Evan M. Gaertner

Masters Theses

Floating offshore wind turbines in deep waters offer significant advantages to onshore and near-shore wind turbines. However, due to the motion of floating platforms in response to wind and wave loading, the aerodynamics are substantially more complex. Traditional aerodynamic models and design codes do not adequately account for the floating platform dynamics to assess its effect on turbine loads and performance. Turbines must therefore be over designed due to loading uncertainty and are not fully optimized for their operating conditions. Previous research at the University of Massachusetts, Amherst developed the Wake Induced Dynamics Simulator, or WInDS, a free vortex wake …

New Generator Control Algorithms For Smart-Bladed Wind Turbines To Improve Power Capture In Below Rated Conditions, Bryce B. Aquino

Masters Theses

With wind turbines growing in size, operation and maintenance has become a more important area of research with the goal of making wind energy more profitable. Wind turbine blades are subjected to intense fluctuating loads that can cause significant damage over time. The need for advanced methods of alleviating blade loads to extend the lifespan of wind turbines has become more important as worldwide initiatives have called for a push in renewable energy. An area of research whose goal is to reduce the fatigue damage is smart rotor control. Smart bladed wind turbines have the ability to sense aerodynamic loads …

Aerodynamic Optimization Of Box Wing – A Case Study, Adeel Khalid, Parth Kumar

International Journal of Aviation, Aeronautics, and Aerospace

The optimization of a possible medium range box wing commercial airliner is presented in three stages. Preliminary research is used to determine various parameters for a potential box wing model, and a baseline model is designed in Autodesk Inventor, based upon the cantilever Airbus A330-200, an aircraft of a similar role. The Computational Fluid Dynamics (CFD) software used in this project is Dassault Systèmes SolidWorks, which is validated through comparing the NACA 0009 airfoil lift and drag polars with published results. The first stage of optimization is performed on the airfoil shape, with 8 different designs being tested against the …

Exploration Of A Computational Fluid Dynamics Integrated Design Methodology For Potential Application To A Wind Turbine Blade, Gaurav Kapoor

Doctoral Dissertations and Master's Theses

The main purpose of this thesis is to conduct a parametric sensitivity study on the blade design of AOC 15/50 wind turbine based on a CFD approach and optimize the blade design for maximizing the power output. The ANSYS® Fluent® flow solver using the k-ω SST turbulence model was validated by simulating the flow over two dimensional airfoils comprising the AOC 15/50 wind turbine blade. The CFD results have shown a considerable agreement with the experimental data for the airfoils. Parametric correlation study and sensitivity analysis were conducted by performing actual flow simulations over the turbine blade using ANSYS® Fluent®. …

Investigation Of Conjugate Heat Transfer In Fluid-Structure Interaction Modeling Using Openfoam, Andrew Brown

Aerospace Engineering

No abstract provided.

Crossflow Instability And Transition On A Circular Cone At Angle Of Attack In A Mach-6 Quiet Tunnel, Christopher A. C Ward

Open Access Dissertations

To investigate the effect of roughness on the stationary crossflow vortices, roughness elements 2 inches from the nosetip were created in a Torlon insert section of a 7-deg half-angle cone at 6-deg angle of attack in the Boeing/AFOSR Mach-6 Quiet Tunnel. Roughness elements with depths and diameters on the order of 500 microns were found to have a significant effect on the generation of the stationary vortices and the location of crossflow-induced transition under quiet flow. Crossflow-induced transition was measured under fully quiet flow. The controlled roughness elements also appeared to dominate the generation of the vortices, overwhelming the effect …

Characterization And Low-Dimensional Modeling Of Urban Fluid Flow, Dietmar Rempfer, Candace Wark, Bruno Monnier, Sriharsha Kandala

Publications

This report describes work that was done under AFOSR Contract Number FA9550-11-1-0056, studying the structure of a model urban boundary layer flow. The model geometry consisted of a set of plexiglass blocks, and the flow around this geometry was studied both experimentally as well as computationally. For the experiment, a Stereoscopic Particle Image Velocimetry (SPIV) method was developed that allows for a three-dimensional description of this urban flow, and helps gain insight into the characteristic flow structures in the streets and canyons of our model urban geometry. On the computational side, a new spectral-element code was developed that was demonstrated …

An Experimental Study Of The Implementation Of A Fluid Diode Inside A Sano Shunt, Patrick Austin Lane

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Fluid diodes are fluidic devices that enhance fluid flow in a particular direction while inhibiting it in the opposite direction without the use of moving parts. This is accomplished through the use of nozzle shaped geometry on one side of the diode, and cusp shaped geometry on the opposing side. Fluid meets very little resistance as is travels though the nozzle side of the diode. The cusps on the other side of the diode reduce the effective flow area, thereby inhibiting flow. The objective of this study is to determine the effectiveness of a fluid diode installed in a reconstructed …

Turbulent Transition In Electromagnetically Levitated Liquid Metal Droplets, Jie Zhao

Masters Theses

The condition of fluid flow has been proven to have a significant influence on a wide variety of material processes. In electromagnetic levitation (EML) experiments, the internal flow is driven primarily by electromagnetic forces. In 1-g, the positioning forces are very strong and the internal flows are turbulent. To reduce the flows driven by the levitation field, experiments may be performed in reduced gravity and parabolic flights experiments have been adopted as the support in advance. Tracer particles on the surface of levitated droplets in EML experiment performed by SUPOS have been used to investigate the transition from laminar to …

Response Of Transmission Line Conductors Under Downburst Wind, Haitham Aboshosha

Electronic Thesis and Dissertation Repository

Electricity is transmitted by Transmission Lines (TLs) from the source of production to the distribution system and then to the end consumers. Failure of a TL can lead to significant economic losses and to negative social consequences resulting from the interruption of power. High Intensity Winds (HIW), in the form of downbursts and tornadoes, are believed to be responsible for more than 80% of the weather-related failure of TLs around the world. The studies reported in this thesis are part of an ongoing extensive research program at Western University focusing on the response of TLs under HIW. Previous investigations conducted …

Microthruster Fabrication And Characterization: In Search Of The Optimal Nozzle Geometry For Microscale Rocket Engines, Katherine L. Fowee, Alina Alexeenko

The Summer Undergraduate Research Fellowship (SURF) Symposium

A major consideration in microsatellite design is the engineering of micropropulsion systems that can deliver the required thrust efficiently with tight restrictions on space, weight, and power. Cold gas thrusters are one solution to the demand for smaller propulsion systems to accommodate the advancements in technology that have allowed for a reduction in the size and thus the cost of satellites. While much research has been done in understanding the flow regimes within these microthrusters, there is a need to understand how different nozzle designs affect microthruster performance. This requires that experimental data be collected on varying nozzles shapes (orifices, …

Noise Source Analysis For Simulated Turbulent Jets, Robert W. Skidmore, Nitin S Dhamankar, Kurt M. Aikens, Gregory Blaisdell

The Summer Undergraduate Research Fellowship (SURF) Symposium

Large Eddy Simulation (LES) is an efficient computational approach to study turbulent flows and has seen increasing application to the study of jet noise. The main challenge of LES has been the realistic simulation of experiments at reasonable cost. Recent LES studies have been realistic enough to gain important insight into jet noise from the large amount of data generated. This study attempts to characterize the sources of noise from a turbulent jet via analysis of the LES results. Three different analysis tools are implemented. The first two are comparable to analyses used on experimental data: two-point cross-correlations between far-field …

Particle Image Velocimetry Of Transverse Jets In Crossflow, Jesse K. Tsai, Kayla Kuzmich, David Forliti, Kriss Vanderhyde, Nils Sedano

STAR Program Research Presentations

The jet in crossflow (JICF) has been an ongoing study for the past several decades with applications in the field of fluid mechanics. This particular flow field produces vortical structures tied to the entrainment and mixing of two separate fluids. Research of the JICF seeks to determine a model and trajectory scaling law for future designs. This will help future designers to optimize the mixing and homogeneity of the two fluids to decrease emissions from pollutants, make ignition easier, and improve combustion efficiency of rockets.

Our experiment will employ Particle Image Velocimetry (PIV) to determine the fluid motion of the …

Effect Of Adaptive Tabs On Drag Of A Square-Base Bluff Body, Brian W. Barker

Master's Theses

This thesis involves the experimental wind tunnel testing of a 0.127m by 0.127m square-base bluff body to test the effectiveness of trailing edge tabulations to reduce drag in the Cal Poly 0.912m by 1.219 m low-speed wind tunnel. To accomplish this, the boundary layer was first measured on the trailing edge of the model for the three speeds at 10, 20, and 30 m/s, with Re = 8.3e4, 1.6e5 and 2.5e5 respectively, without the tabs. Three different tests were performed to determine the effectiveness of the tabs. These tests included base pressure measurements, total drag force measurements and hotwire velocity …

Experimental Investigation Of Active Wingtip Vortex Control Using Synthetic Jet Actuators, Peter J. Sudak

Master's Theses

An experiment was performed in the Cal Poly Mechanical Engineering 2x2 ft wind tunnel to quantify the effect of spanwise synthetic jet actuation (SJA) on the drag of a NACA 0015 semispan wing. The wing, which was designed and manufactured for this experiment, has an aspect ratio of 4.20, a span of 0.427 m (16.813”), and is built around an internal array of piezoelectric actuators, which work in series to create a synthetic jet that emanates from the wingtip in the spanwise direction. Direct lift and drag measurements were taken at a Reynolds Number of 100,000 and 200,000 using a …

Hybrid Rocket Design Study Utilizing Nozzle Cooling And Aft-End Vortex Oxidizer Injection, John Nicholas Quigley

Masters Theses

The current study focused on two innovations intended to reduce the cost and enhance the performance of hybrid rockets. The majority of the emphasis was placed on the design, fabrication and testing of a 3-D printed, water cooled nozzle. This work was done as proof of concept to show that complex, high temperature components could be manufactured using these new techniques, thereby substantially bringing down fabrication costs and allowing configurations that are not feasible using traditional machining. A water-cooled calorimeter nozzle was made and used in thrust stand tests to verify analytic and numerical heating models used in the design …

Numerical Investigation Of Pyrolysis Gas Blowing Pattern And Thermal Response Using Orthotropic Charring Ablative Material, Haoyue Weng, Alexandre Martin

Mechanical Engineering Faculty Publications

An orthotropic material model is implemented in a three-dimensional material response code, and numerically studied for charring ablative material. Model comparison is performed using an iso-Q sample geometry. The comparison is presented using pyrolysis gas streamlines and time series of temperature at selected virtual thermocouples. Results show that orthotropic permeability affects both pyrolysis gas flow and thermal response, but orthotropic thermal conductivity essentially changes the thermal performance of the material. The effect of orthotropic properties may have practical use such that the material performance can be manipulated by altering the angle of orthotropic orientation.

Numerical Study Of Spallation Phenomenon In An Arc-Jet Environment, Raghava Davuluri, Alexandre Martin

Mechanical Engineering Faculty Publications

The spallation phenomenon might affect the aerodynamic heating rates of re-entry vehicles. To investigate spallation effects, a code is developed to compute the dynamics of spalled particles. The code uses a finite-rate chemistry model to study the chemical interactions of the particles with the flow field. The spallation code is one-way coupled to a CFD solver that models the hypersonic flow field around an ablative sample. Spalled particles behavior is numerically studied for argon and air flow field. The chemistry model is compared with that of Park's model which complies with oxidation and sublimation and shows disagreement for nitridation.

Separation Bubbles And Vortex Formation In Cavity Flows, Kartheek Ravulapati

Doctoral Dissertations and Master's Theses

This research is a computational fluid dynamic study of the formation of vortices and separation bubbles in a square cavity as well as in a cylindrical cavity. Whereas there has been previous research work on the problem of a free stream over different types of cavities, like open and closed cavities or lid driven cavities, this research on an inlet induced flow inside a square cavity lead to unusual and interesting basic fluid dynamical phenomena. The flow in a square cavity and in a cylindrical cavity is simulated over a range of Reynolds numbers and the appearance of separation bubbles …

Neutron Imaging Of Lithium (Li) Coolants Inside High Temperature Niobium (Nb) Heat Pipes, Brad Harrison Hight

Masters Theses

Lithium (Li) behavior inside a high temperature Nb-Li leading edge heat pipe was successfully imaged under induction heating operation via neutron imaging. Startup and cool-down operations gave visual confirmation of bulk Li movement using both gravity assisted and inverted operating orientations. The pipe was imaged during an operation cycle from ambient conditions, heated to a steady state temperature of 908.8 ⁰C, and allowed to cool below 200^°C. The experiment was performed at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, and at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee.

Tomographic images …

A Qualitative Experimental Study Of Drag Reduction Devices For Tractor Trailers With Ground Effects, Nicolas Robert Reed

Masters Theses

This is an experimental qualitative study of how drag reduction devices affect air flow around a tractor trailer. A 1/32 scale detail model of a truck with its trailer was used for testing in a 20"x14" low speed wind tunnel at the University of Tennessee Space Institute. Major modifications were made to the wind tunnel so that it would include a moving bed (floor) section for ground effect simulation. This was done to accurately simulate relative ground movement with the truck being held stationary in the tunnel flow.

Drag reduction devices were designed based on aerodynamic fundamental understanding for streamlining …

Performance Improvement Through Velocity Triangle Optimization-Driven Redesign For Mitigating The Horseshoe Vortex In Axial Turbines, Vladislav Shulman

Doctoral Dissertations and Master's Theses

Momentum differences between the neighboring streamlines at the end wall/primary flow interaction region of an axial turbine stage induce three-dimensional vortical flow structures, such as the leading edge horseshoe vortex, resulting in significant aerodynamic performance deterioration. Reducing the effect of such flow instabilities requires turbine blade modification to discourage boundary layer roll-up, but traditional structural modification design systems can be prohibitively complex and time-intensive.

To address this problem, this study contributes a blade modification method involving airfoil shape optimization, designed to adjust the leading edge airfoil shape in horseshoe vortex-affected turbine applications. The key insight is that airfoil design (treated …