Aerospace Engineering Commons^™

Active Control Of Nonlinear Panel Flutter At Supersonic Speed Using Aeroelastic Modes And Self-Sensing Piezoelectric Actuators Under Yawed Flow Angle, Myounghee Kim

Mechanical & Aerospace Engineering Theses & Dissertations

Suppression of nonlinear panel flutter at supersonic speeds has been investigated traditionally with system equations of motion in terms of in vacuo modal coordinates. For isotropic and symmetrically laminated orthotropic composite plates, the limit-cycle oscillations converged with six in vacuo natural modes at zero yaw angle. However, as laminated composite plates undergo the effect of an arbitrary yawed flow angle, complicated characteristics emerge when increasing the required in vacuo natural modes for an analysis of limit-cycle oscillations. In order to design an effective controller, the large number of modes should be reduced. As a result, the small number of modes …

Comparative Study Of Aerodynamic Interference During Aft Dispense Of Munitions, Matthew G. Burkinshaw

Theses and Dissertations

Based on forthcoming USAF needs, an investigation was launched to further the understanding of aft dispense of munitions in a high-speed environment. A computational fluid dynamics (CFD) study was performed followed by a wind tunnel experiment. The study consisted of a strut-mounted cone simulating a parent vehicle and a sting mounted cone-cylinder store situated directly behind the cone. The CFD modeled the test objects inside a supersonic wind tunnel in which the experiments took place. The CFD study consisted of evaluating a new strut designed to reduce asymmetry in the airflow aft of the cone. The CFD study also included …

Flight Dynamic Response Of Hale Aircraft To Kc-135 Flowfield, Amanda J. Devuono

Theses and Dissertations

This research effort examines the static effects of a KC-135 flowfield on a flexible winged Sensorcraft model. The KC-135 flowfield data is generated by a vortex lattice code and integrated into Sensorcraft model for analysis. Building on previous research, a refueling situation was modeled to note the effects of the Sensorcraft at varying locations within the flowfield. The Sensorcraft model was analyzed for both rigid and flexible wings as a means of comparision. Flowfield locations of interest were determined and trimmed conditions were computed for each flowfield location. Utilizing the trimmed condition and flowfield locations, the nonlinear set of EOM's …

Cfd Analysis Of A T-38 Wing Fence, Daniel A. Solfelt

Theses and Dissertations

A computational study of the effects of a wing fence on the T-38 Talon was performed. RANS simulations were conducted using the CFD solver AVUS to examine the flow around the T-38 and the fence at a Reynolds number of 10 million. The T-38 was modeled as a half aircraft with a symmetry plane down the center line and did not include the empennage. The engine inlet and exhaust were modeled as sink and source boundary conditions using mass flow and pressure specifications. Two fence geometries placed 26" from the wing tip were tested. The first fence, called a simple …

Cfd Investigation Of Effect Of Depth To Diameter Ratio On Dimple Flow // Computational Fluid Dynamics Investigation Of Effect Of Depth To Diameter Ratio On Dimple Flow Dynamics, Robert B. Etter

Theses and Dissertations

This study aimed to further the understanding of laminar flow through a dimple with the goal of mitigating flow separation. Dimples of various depth to diameter ratios (0.05, 0.15) were examined for three different dimple diameters and chordwise locations, corresponding to diameter based (ReD) and chordwise location based (Rex) Reynolds number combinations of ReD 20500\Rex 5000, ReD 20500 Rex 77000, and ReD 9000 Rex 21000. For the last combination, a dimple of depth to diameter ratio of 0.25 was also examined. The dimples were placed in a flat plate located in a diverging channel causing an adverse pressure gradient encouraging …

A Comparison Of Film Cooling Techniques In A High Speed, True Scale, Fully Cooled Turbine Vane Ring, Michael J. Umholtz

Theses and Dissertations

An effort was undertaken to understand the impact of different film cooling configurations in a true scale turbine vane for three proprietary airfoil designs. The measurements for this study were taken at the United States Air Force Turbine Research Facility (TRF). The TRF enabled heat transfer data to be obtained on full scale turbine hardware under realistic engine conditions. The surface heat flux of the turbine blades was analyzed using the impulse response method. The overall effectiveness was compared between airfoil types at 60% span over varying streamwise locations on both suction and pressure surfaces. Using an approximated massflow, a …

Optimization Of Zero Net-Mass Flow Actuators For Aero-Optics Applications, Moira L. Denatale, Jonathan M. Mihaly

Renée Crown University Honors Thesis Projects - All

Using experimental methods, zero net-mass flow actuators were optimized to manipulate flow around an airborne laser turret in order to reduce destructive aero-optics effects. Synthetic jets are created by 50 mm and 27 mm piezoelectric disk actuators. Our optimization process involved identifying an actuator’s cavity size, driving frequency, and amplitude to achieve the strongest, most consistent jet possible. The effects of driving a single actuator versus driving two actuators in or out of phase with one another were also investigated. An initial cavity depth was determined using the Helmholtz resonator cavity approximation which estimates the ideal cavity depth for a …

Aerodynamic And Acoustic Investigations Of An Advanced Over-The-Wing Nacelle Transport Aircraft Configuration, Geoffrey A. Hill

Mechanical & Aerospace Engineering Theses & Dissertations

The transonic aerodynamic and low-speed acoustic characteristics of an advanced, Over-the-Wing Nacelle (OWN), subsonic transport configuration are assessed. The cruise aerodynamics of the OWN were analyzed using both inviscid Euler and viscous Navier-Stokes CFD. Results of the assessments are compared to a similar configuration with a more traditional Under-the-Wing Nacelle (UWN) installation and a similar reference Wing-Body Qualitative observations and quantitative drag computations are made for the three configurations at a cruise Mach number of0.78, an approximate altitude of35,000-ft, and a C_L, of 0.44. It was found that the OWN's novel inboard wing channel design is effective in …

Cfd Investigation Of Flow Past Idealized Engine Nacelle Clutter /// Computational Fluid Dynamics Investigation Of Flow Past Idealized Engine Nacelle Clutter, Matthew S. Caspers

Theses and Dissertations

This research modeled low-speed flow past idealized engine nacelle clutter in support of aircraft re suppression research. The idealized clutter was comprised of three vertical rows of staggered circular cylinders approximating typical nacelle obstructions such as fuel lines and wire bundles. Single-phase, Detached-Eddy Simulations (DES) were conducted using the commercial CFD solver, Fluent™, to resolve the flow-field dynamics inside the clutter element and determine mechanisms accounting for the failure of suppressant spray droplets from traversing the array under low-speed, free-stream conditions (ReD = 1, 575). The numerical models provided no evidence that span-wise vorticity or non-uniform shedding was responsible for …

Filtered Rayleigh Scattering Measurements In A Bouyant Flowfield, Christopher C. Mcgaha

Theses and Dissertations

Filtered Rayleigh Scattering (FRS) is a non-intrusive technique for studying flowfields. Molecular scattering provides the signal to the camera, and the difference in molecular cross section can be used to discriminate between unmixed gaseous components. The focus of this research is to document the behavior of a horizontal buoyant jet using FRS. A helium jet of precisely controlled mass flow rate is injected into a standard room temperature environment, and FRS provides the means to measure its core trajectory and mixing rate. Trajectory analysis, conducted with consideration of the Reynolds number and Grashof number, can be used to compare these …

Quantifying Non-Equilibrium In Hypersonic Flows Using Entropy Generation, Ryan W. Carr

Theses and Dissertations

The constitutive relations traditionally used for finding shear stress and heat flux in a fluid become invalid in non-equilibrium flow. Their derivation from kinetic theory only demonstrates they are valid only for small deviations from equilibrium. Because it is fundamentally linked to non-equilibrium, entropy generation is used to investigate the limits of the continuum constitutive relations. However, the continuum equations are inherently limited to near equilibrium conditions due to the constitutive relations; thus kinetic theory must be used as a basis for comparison. Direct Simulation Monte Carlo (DSMC), a particle method alternative to continuum methods, is based on kinetic theory …

Experimental Investigation Of Oblique Wing Aerodynamics At Low Speed, Matthew J. Dillsaver

Theses and Dissertations

In an effort to increase the range of missiles and guided bombs, the USAF is looking at options for new wing configurations. One such configuration being considered is oblique wings. An oblique wing is a wing that pivots about a point on the aircraft fuselage thereby having one side swept forward and the other swept aft. Additional interest is looking at a wing only configuration that also rotates with one wing tip forward of the other. Studies have shown that this configuration can provide less drag for a given lift at both supersonic cruise and subsonic loiter conditions. This experiment …

Experimental Characterization Of Turbulent Flow Around Cylinder Arrays, Adam D. Harder

Theses and Dissertations

This research was done as part of an effort to develop alternative fire suppressant technologies for aircraft engine nacelles. A circular cylinder array was designed, built, and placed in the AFIT roll-around low speed wind tunnel to model generic clutter inside an engine nacelle. A turbulence grid was fabricated to enable measurements of the effects of turbulence level, independent of airspeed, on the flow over different model configurations. The wind tunnel test section was 12 inches wide x 12 inches high x 24 inches long. Pressure differential measurements were taken on various cylinder configurations. The configurations included one cylinder as …

Demonstration Of Clean Particle Seeding For Particle Image Velocimetry In A Closed Circuit Supersonic Wind Tunnel, Charles M. Mcniel

Theses and Dissertations

The purpose of this research was to determine whether solid carbon dioxide (CO₂) particles might provide a satisfactory, and cleaner, alternative to traditional seed material for Particle Image Velocimetry (PIV) for use in a closed circuit supersonic wind tunnel. The Air Force Institute of Technology (AFIT) closed circuit pressure-vacuum supersonic wind tunnel was utilized, which achieves a nominal Mach number of Mach 2.9 in a 2.5 inch by 2.5 inch square test section. CO₂ was dispensed into the flow as a liquid from a standard compressed gas liquid tank through two different injector styles at two injection …

The Aerodynamic Performance Of The 24 Inch Houck Configuration, Michael M. Walker

Theses and Dissertations

Fuel efficiency of aircraft is of great importance to the military and private sector. A more efficient wing design for UAVs would lead to improvements in mission support while reducing fuel costs for the Air Force. An experimental investigation of one candidate design, the Houck Aircraft Configuration, has been conducted in the AFIT low speed wind tunnel. This aircraft shares similarities to other joined-wing aircraft, but includes curved flow-guides of varying spanwise camber connecting the upper and lower wingtips. Experimental results that the addition of flow guides on the 24" Houck Configuration results in a 2.5% reduction in L/D(sub max) …

Validation Of Conjugate Heat-Transfer Capability For Water- Cooled High-Speed Flows, Bruno R. Fletcher

Master's Theses - Daytona Beach

A FORTRAN conduction/convection heat transfer module named FOGO (meaning fire in Portuguese) has been developed to perform the conjugate heat transfer analyses with existing flow solvers. In this work, FOGO is coupled with TBD and WIND-US flow solvers. WIND-US is a well validated flow solver developed by NASA, AEDC, and Boeing. TBD is a new flow solver developed at ERAU. TBD is verified for laminar stagnation point heat transfer prediction and turbulent flowfield protection. The FOGO module is verified against an exact solution for transient one-dimensional heat flow in a semi-infinite solid

The coupled TBD-FOGO and WIND-FOGO conjugate heat-transfer solvers …

Modeling Redox-Based Magnetohydrodynamics In Three-Dimensional Microfluidic Channels, Hussameddine S. Kabbani, Aihua Wang, Xiaobing Luo, Shizhi Qian

Mechanical Engineering Faculty Research

RedOx-based magnetohydrodynamic MHD[1] flows in three-dimensional microfluidic channels are investigated theoretically with a coupled mathematical model consisting of the Nernst-Planck equations for the concentrations of ionic species, the local electroneutrality condition for the electric potential, and the Navier-Stokes equations for the flow field. A potential difference is externally applied across two planar electrodes positioned along the opposing walls of a microchannel that is filled with a dilute RedOx electrolyte solution, and a Faradaic current transmitted through the solution results. The entire device is positioned under a magnetic field which can be provided by either a permanent magnet or an electromagnet. …

Coupling Of Fluid & Solid Thermal Models To Correct Heat Flux Measurements Taken On Launch Vehicles, Danielle M. Ford

Master's Theses - Daytona Beach

Knowledge of aerothermally induced convective heat transfer and plume induced radiative heat transfer loads is essential to the design of thermal protection systems (TPS) for launch vehicles. These loads are measured via the cylindrical heat flux gauges that are flush mounted with the outer surface of a launch vehicle and are exposed to the in-flight external thermal and velocity boundary layers as well as thermal radiation. Typically, Schmidt-Boelter gauges measure the incident heat flux based on the one-Dimensional Fourier's law. This instrumentation, when surrounded by low-conductivity insulation, has an exposed surface temperature significantly lower than the insulation. A substantial disturbance …

Capillary-Driven Flows Along Rounded Interior Corners, Yongkang Chen, Mark M. Weislogel, Cory L. Nardin

Mechanical and Materials Engineering Faculty Publications and Presentations

The problem of low-gravity isothermal capillary flow along interior corners that are rounded is revisited analytically in this work. By careful selection of geometric length scales and through the introduction of a new geometric scaling parameter Tc, the Navier–Stokes equation is reduced to a convenient∼O(1) form for both analytic and numeric solutions for all values of corner half-angle α and corner roundedness ratio λ for perfectly wetting fluids. The scaling and analysis of the problem captures much of the intricate geometric dependence of the viscous resistance and significantly reduces the reliance on numerical data compared with several previous solution methods …

Flow Control Of Airfoil At Post-Stall Conditions By Multiple Frequency Applied Saado Jets, A. Şamil Demirsöz

Mechanical & Aerospace Engineering Theses & Dissertations

Flow separation over lifting aerodynamic components, such as airfoils and wings, occurs during stall conditions which are caused by adverse changes (i.e.; high angle of attack, inflow conditions, etc.) in the operating conditions of aerodynamic components. During stall conditions, the flow over airfoil loses its momentum, creating high pressure zones on the upper surface of the airfoil and even a small increase in pressure causes the fluid particles to stop and separate to a low pressure zone. In order to eliminate the flow separation, the low momentum flow should be removed in order to maintain the high momentum and low …

Three Component Velocity Measurements In The Tip Vortex Of A Micro-Air-Vehicle, Hong-Joon Park

Theses and Dissertations

The purpose of this research was to improve the MAV that will be used for battle damage assessment and reconnaissance or local surveillance through the experiments in AFIT wind tunnel. The experiments were performed to investigate the wing displacement and wing tip vortex interaction. To conduct the experiments, telescopic survey tool and tri-axial hot-wire anemometer was utilized. The results indicate that wing tip displacement of the flexible wing was approximately 8 times that of the rigid wing in an unstalled condition and data suggests that flexible wing has a denser core-distribution of velocity within the wing tip vortex and delays …

An Investigation Of The Dynamic Effects Of Flap Deflection On The Aerodynamic Characteristics Of An Airplane Wing Using Computational Fluid Dynamics, Alexander Moerchel

Master's Theses - Daytona Beach

Flaps are used to increase an airplane's lift and to adjust its stability and maneuverability. This study shows an application of STAR-CD, a commercial computational fluid dynamics (CFD) software, to an investigation of the dynamic effects of flap deflection on the lift, drag and moment coefficients, as well as on the location of the center of pressure. For this study, a plain flap was modeled with a moving mesh and was attached to a NACA 0012 airfoil and a wing of a general aviation aircraft for a 2D and 3D investigation, respectively. In addition, the flap deflection rates were varied …

Global Modeling Of Pitch Damping From Flight Data, Noah M. Favaregh

Mechanical & Aerospace Engineering Theses & Dissertations

Flight testing using a designed experiment was used to model pitch damping in the longitudinal short-period mode of an aircraft. Multi-step elevator maneuvers were flown at different angles of attack and power levels on an electrically powered, propeller-driven UltraStick 120 remotely controlled model A Central Composite Response Surface Design was used to select angle of attack and power levels for each maneuver. During post flight analysis it was discovered that power was not measured correctly for this purpose so advance ratio was selected as a replacement factor. Parameter estimation results for each maneuver were modeled globally using a single response …

Particle Image Velocimetry Using A Novel, Non-Intrusive Particle Seeding, Charles J. Delapp Ii

Theses and Dissertations

The purpose of this research effort was to study the use of non-intrusive particle seeding for Particle Image Velocimetry (PIV). Current seeding material and techniques involve the use of either solid particles or liquid mixtures which can contaminate or damage closed circuit wind tunnels, and in some cases can introduce a potential fire or explosive hazard. The proposed method is based on creating seed particles utilizing Carbon Dioxide (CO2). The CO2 would be dispensed into the flow as a liquid, immediately condensing to solid seed particles as they leave the spray nozzle. The advantage of using these particles is that …

A Wind Tunnel Investigation Of Joined Wing Scissor Morphing, Christopher C. Dike

Theses and Dissertations

The Air Force Research Laboratory's Munitions Directorate has been looking to extend the range of its small smart bomb. Corneille [6] has conducted tests to determine the aerodynamic characteristics of joined wings on a missile and determine if joined wings are more beneficial than a single wing configuration. The concept of retrofitting wings on the bomb introduced an interesting problem: storage before deployment. This study conducted steady-state low speed wind tunnel testing of a joined wing configuration that morphed from a compact configuration for storage to a full extension. These steady-state tests examine differing sweep angles of the same joined …

Characterizing A Co-Flow Nozzle For Use In A Filtered Rayleigh Scattering System, David S. Miceli

Theses and Dissertations

Research was conducted on the flow field exiting a co-annular flow nozzle for use in filtered Rayleigh scattering flow visualizations. More specifically, the flow visualizations were of the flow field exiting a coflow nozzle and illuminated by a tunable, nominal 4.2 watt narrow line width Argon laser operating at 514.5nm. ND:YAG lasers are typically used in this application, but some of the properties of a tunable Argon laser make it an attractive alternative. Before generating flow visualizations, the coflow nozzle was characterized both experimentally and computationally. Due to a flow asymmetry in the outer annulus flow field, the nozzle was …

Experimental Investigation Of The Aerodynamic Ground Effect Of A Tailless Lambda-Shaped Ucav With Wing Flaps, Jason T. Mostaccio

Theses and Dissertations

This experimental study adequately identified the ground effect region of a lambda-shaped unmanned combat air vehicle (UCAV). The lambda planform used in this study was originally tested in a previous experiment to determine the stability and control characteristics generated out-of-ground-effect. The following study extends the existing database by analyzing the inherent aerodynamic behavior that is produced by employing trailing edge flap deflections while flying in-ground-effect (IGE). To accomplish this objective, static ground effect tests were performed in the AFIT 3? x 3? subsonic wind tunnel where a ground plane was used to simulate the forces and moments on the UCAV …

Dynamic Nonlinear Bending And Torsion Of A Cantilever Beam, Michael S. Whiting

Theses and Dissertations

This effort sought to measure the dynamic nonlinear bending and torsion response of a cantilever beam. The natural frequencies of a cantilever beam in both chord and flap directions were measured at different static root pitch angles with varying levels of weights attached at the free end. The results were compared with previous experimentation to validate the data and testing procedures while lowering the associated error bands. Additionally, methodology for measuring mode shapes was set forth and mode shapes were measured for a few test cases with zero degrees of root pitch.

Design Optimization Of The First Stage Fan Blade Of A Low Bypass Turbofan Engine, Troy James Ramnath

Master's Theses - Daytona Beach

A procedure for solving for and analyzing the aerodynamics, thermodynamics, and blade geometry across the first stage rotor blade under an extreme set of conditions, while altering several design parameters, has been developed and applied. The conditions for which the analyses have been developed were designed for the use of, but not exclusively limited to the application of, military aircraft at altitude. The approach consists of solving for specific key performance parameters across the first stage rotor and analyzing their trends due to the effect of varying other parameters, such as the axial velocity at the rotor's trailing edge, circumferential …

Free Flight Store Simulation Using Beggar, Judson T. Babcock

Theses and Dissertations

The complete numerical solution of the airflow around a store in extended free flight is of particular importance to the United States Air Force. Beggar is the primary Computational Fluid Dynamics (CFD) program used by the USAF to obtain solutions for store separations. However, Beggar's ability to simulate a store in free flight is limited because the store must fall through a static background mesh, eventually reaching a point where the solution will fail. The length of any free flight simulation is consequently limited by the height of the background mesh. Code modifications are made to Beggar to remove this …