Aerospace Engineering Commons^™

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 …

Performing Particle Image Velocimetry In A Supersonic Wind Tunnel Using Carbon Dioxide As The Seed Material, Donald W. Peltier Iii

Theses and Dissertations

Particle image velocimetry (PIV) was performed utilizing clean seed particles generated by injecting liquid carbon dioxide (CO₂) directly into an open-circuit blowdown Mach 2.9 supersonic wind tunnel. Rapid atomization and cooling of the liquid CO₂ created a preponderance of nearly uniform and well dispersed microscopic dry ice particles which were illuminated using a frequency double Nd:YAG laser. Ample light was scattered from the flow tracers, which provided a strong signal to noise ratio. The particles completely sublimed into an innocuous gas downstream of the test section causing no side effects or problems with wind tunnel operation. A …

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 …

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 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 …

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 …

A Comparative Analysis Of Single-Stage-To-Orbit Rocket And Air-Breathing Vehicles, Benjamin S. Orloff

Theses and Dissertations

This study compares and contrasts the performance of a variety of rocket and air breathing, single-stage-to-orbit, reusable launch vehicles. Fuels considered include bi-propellant and tri-propellant combinations of hydrogen and hydrocarbon fuels. Astrox Corporation's HySIDE code was used to model the vehicles and predict their characteristics and performance. Vehicle empty mass, wetted area and growth rates were used as figures of merit to predict the procurement, operational and maintenance cost trends of a vehicle system as well as the system's practicality. Results were compared to those of two-stage-to-orbit reusable launch systems using similar modeling methods. The study found that single-stage-to-orbit vehicles …

Alleviation Of Buffet-Induced Vibration Using Piezoelectric Actuators, Shawn D. Morganstern

Theses and Dissertations

Buffet-induced vibration has been problematic for aircraft structures for many years. The F-16 ventral fin, while prone to these effects, lends itself well to the evaluation of modern active structural and flow control technologies. The objective of this research was to determine the most critical natural modes of vibration for the F-16 ventral fin and design piezoelectric actuators capable of reducing buffet-induced ventral fin vibration. A finite element model (FEM) for the fin was developed, tuned and optimized to closely match published modal frequencies. Piezoelectric actuator patches were designed using the strain characteristics of the FEM and integrated into the …

Macroscopic Computational Model Of Dielectric Barrier Discharge Plasma Actuators, Timothy R. Klein

Theses and Dissertations

Recent progress in the generation and sustainment of gas discharges at atmospheric pressure has energized research in the field of plasma-aerodynamics. Plasma actuators are promising devices that achieve flow control with no moving parts, do not alter the airfoil shape and place no parts in the flow. The operation of a plasma actuator is examined using a macroscopic (force and power addition) computational fluid dynamic model of a dielectric barrier discharge, DBD, in Fluent. A parametric approach is adopted to survey the range of requisite magnitudes of momentum and energy delivered to the flow field and to identify the effects …

Modeling, Stability, And Control Of A Rotatable Tail On A Micro Air Vehicle, Travis J. Higgs

Theses and Dissertations

This research uses existing experimental wind tunnel data to develop a non-linear model that is used to characterize the stability of a flexible wing Micro Air Vehicle (MAV) with a rotatable tail. The experimental data are curve fit based on either angle of attack or angle of sideslip, and the coupled effect of tail rotation and tail deflection on the force and moment coefficients. Static optimization trims the input and state variables for Steady Level Unaccelerated Flight (SLUF). The resulting initial conditions are fed to an open loop non-linear Simulink/Matlab simulation. The study found that the bare MAV design is …

The Effect Of Aerodynamic Surfaces Versus Thrust Maneuvers On Reentry Vehicles, Meredith M. Albrecht

Theses and Dissertations

This research effort analyzes the effect of aerodynamic surfaces versus thrust maneuvers on a reentry vehicle. At high altitudes the effect of aerodynamic surfaces on the reentry vehicle is small due to low atmospheric density; however as the vehicle reaches lower altitudes a lift maneuver is very successful in deflecting the vehicle and creating a large impact footprint. When a continuous thrust maneuver is input in the place of a lift maneuver the results are very similar at the highest maneuver altitudes, although the impact footprint shrinks rapidly as the maneuver altitude decreases. Additionally, when the thrust maneuver is along …

A Prediction Code For The Thrust Performance Of Two-Dimensional, Non-Axisynnetric, Converging Diverging Nozzles, Angela M. Geatz

Theses and Dissertations

The objective of this research is to develop a prediction code for the Air Force Research Laboratory Propulsion Directorate that can accurately determine the gross thrust coefficient for a user defined nonaxisymmetric two-dimensional converging diverging nozzle. The code includes the effects of friction, angularity, and expansion losses on nozzle efficiency. To demonstrate the prediction method, the generated computational results were compared to experimental data, as well as computational results from other existing nozzle performance codes, for a number of different nozzle geometries. The nozzle internal performance prediction code showed excellent agreement with experimental data in predicting the gross thrust performance …

Characterization Of Upstream Mixing Cavities And A Downstream Combustion Cavity In Supersonic Flow, Adam P. Quick

Theses and Dissertations

A key area of study in air-breathing hydrocarbon-fueled scramjet combustors is the characterization of cavity-based fuel injection and flame holding. One issue concerns oscillatory disturbances caused by trapped vortices in the main flame holder cavity as a fuel-air mixing enhancement technique. Previous research demonstrates that oscillatory disturbances can be carried downstream via the shear layer and alter the oscillatory characteristics of a downstream cavity. This study investigates the mixing effectiveness of three upstream direct-fueled mixing cavities as well as the effect on the oscillatory behavior of the downstream combustion cavity by the upstream mixing cavity. The three upstream mixing cavities …

Aerodynamic Analysis Of Lattice Grid Fins In Transonic Flow, Karl S. Orthner

Theses and Dissertations

Lattice grid fins have been studied for missile tail control for several years. A lattice grid fin can be described as an unconventional missile control surface comprised of an outer frame supported by an inner lattice grid of lifting surfaces. This unconventional fin design offers favorable lift characteristics at high angle of attack as well as almost zero hinge moments allowing the use of small and light actuators. In addition, they promise good storability for potential tube-launched and internal carriage dispenser-launched applications. The drawback for the lattice grid fins is the high drag and potentially poor radar cross section performance …

Experimental Investigation Into The Aerodynamic Performance Of Both Rigid And Flexible Wing Structured Micro-Air-Vehicles, Anthony M. Deluca

Theses and Dissertations

The Air Force Research Lab, Munitions Directorate, Eglin Air Force Base, Florida has designed a man-portable carbon-fiber Micro-Air-Vehicle (MA V) used for on-the-spot surveillance by Special Operations Forces (SOF) for enemy reconnaissance as well as post-strike Battle Damage Assessment (BDA).The main goals of this experiment are: 1) characterize the flow quality of the new AFIT 3' x 3' wind tunnel and 2) determine the aerodynamic performance characteristics of the 24" span, 6" chord flexible and rigid wing MA V s. The turbulent intensity of the wind tunnel was approximately 2%. Both MA Vs had an average lift slope within 3.5% …

Intelligent Strain Sensing On A Smart Composite Wing Using Extrinsic Fabry-Perot Interferometric Sensors And Neural Networks, Kakkattukuzhy M. Isaac, Donald C. Wunsch, Steve Eugene Watkins, Rohit Dua, V. M. Eller

Electrical and Computer Engineering Faculty Research & Creative Works

Strain prediction at various locations on a smart composite wing can provide useful information on its aerodynamic condition. The smart wing consisted of a glass/epoxy composite beam with three extrinsic Fabry-Perot interferometric (EFPI) sensors mounted at three different locations near the wing root. Strain acting on the three sensors at different air speeds and angles-of-attack were experimentally obtained in a closed circuit wind tunnel under normal conditions of operation. A function mapping the angle of attack and air speed to the strains on the three sensors was simulated using feedforward neural networks trained using a backpropagation training algorithm. This mapping …

External Aerodynamics Of Heavy Ground Vehicles: Computations And Wind Tunnel Testing, Ilhan Bayraktar

Mechanical & Aerospace Engineering Theses & Dissertations

Aerodynamic characteristics of a ground vehicle affect vehicle operation in many ways. Aerodynamic drag, lift and side forces have influence on fuel efficiency, vehicle top speed and acceleration performance. In addition, engine cooling, air conditioning, wind noise, visibility, stability and crosswind sensitivity are some other tasks for vehicle aerodynamics. All of these areas benefit from drag reduction and changing the lift force in favor of the operating conditions. This can be achieved by optimization of external body geometry and flow modification devices. Considering the latter, a thorough understanding of the airflow is a prerequisite.

The present study aims to simulate …

Desktop Computer Programs For Preliminary Design Of Transonic Compressor Rotors, Brian C. Mcdonald

Theses and Dissertations

A need exist for correlation-based desktop computer programs that predict the flow through transonic compressor rotors with nominal computational time and cost. Modified versions of two desktop computer programs, BOWSHOCK and TRANSROTOR, were used to perform a parametric study on a modem compressor rotor. BOWSHOCK calculates the exit flow properties of a supersonic streamtube through a user-defined compressor rotor. TRANSROTOR calculates flow properties at three stations in a user-defined compressor stage. Modifications to TRANSROTOR included the incorporation of a recently published rotor loss model. Baseline and modified TRANSROTOR versions were run with two modern transonic compressor blades. Results were compared …

Measurements Of The Effects Of Tunnel Wall Proximity On The Velocity Field Upstream Of A Rod With Vortex Shedding In Low-Speed Flow, David R. Hopper

Theses and Dissertations

High cycle fatigue is an important consideration in blade design for turbomachinery. Blades in an engine undergo countless loading cycles in a lifetime, the result of pressure waves that propagate upstream and downstream from disturbances in the flow. Better understanding of these effects would allow blade designers to reduce the effects of high cycle fatigue, such as costly recurring maintenance or catastrophic engine failure. An experimental study was undertaken to determine the unsteady flow field upstream of a single cylinder in a subsonic flow. Von Karman vortex shedding from the cylinder produced a forcing function much like periodic blade passage …

Portfolio Assessment In Aerodynamics, Nikos J. Mourtos

Faculty Publications

A new way of assessing student learning in an aerodynamics course through the use of portfolios is presented. The approach is portable to any engineering course, with a few modifications depending on content. The main idea is to allow students more responsibility for their own learning. Instead of having everyone in the class perform identical activities (homework, experiments, projects, tests, etc.), a cadre of assignments is made available to them. Students choose and perform (within reason) the ones that suit them better in terms of their own strengths and learning styles. The ultimate goal is for each student to demonstrate …

Numerical And Experimental Investigation Of The Flowfield Near A Wrap-Around Fin, Carl P. Tilmann

Theses and Dissertations

A wall-mounted semi-cylindrical model fitted with a single wrap-around fin (WAF) has been investigated both numerically and experimentally, with the objective of characterizing the mean and turbulent flowfield in the vicinity of the fin. Numerical and experimental results are used to determine the nature of the flowfield and quantify the effects of fin curvature on the character of the flow near WAFs. This research has been motivated by the need to identify possible sources of a rolling moment reversal observed at high speeds in sub-scale flight tests. Detailed mean flow and turbulence measurements were obtained in the AFIT Mach 3 …

Wing-Section Optimization For Supersonic Viscous Flow, Cem Cihan Item

Mechanical & Aerospace Engineering Theses & Dissertations

The recent interest in the High Speed Civil Transport (HSCT) has resulted in renewed research studies of optimized supersonic cruise transport configurations. Incorporation of flow viscosity effects in the design process of such a supersonic wing is currently under investigation. This may lead to more accurate problem formulations and, in tum, greater aerodynamic efficiency than can be obtained by the traditional, inviscid, linear theories. In this context, for a design code to be a candidate for a complex optimization problem, such as three-dimensional viscous supersonic wing design, it should be validated using simpler building-block shapes.

To optimize the shape of …

Implementation Of A Multiblock Sensitivity Analysis Method In Numerical Aerodynamic Shape Optimization, James Matthew Lacasse

Mechanical & Aerospace Engineering Theses & Dissertations

A multiblock sensitivity analysis method is applied in a numerical aerodynamic shape optimization technique. The Sensitivity Analysis Domain Decomposition (SADD) scheme which is implemented in this study was developed to reduce the computer memory requirements resulting from the aerodynamic sensitivity analysis equations, Discrete sensitivity analysis offers the ability to compute quasi-analytical derivatives in a more efficient manner than traditional finite-difference methods, which tend to be computationally expensive and prone to inaccuracies.

The direct optimization procedure couples CFD analysis based on the two-dimensional thin-layer Navier-Stokes equations with a gradient-based numerical optimization technique. The linking mechanism is the sensitivity equation derived from …

Computation Of The Aerodynamic Characteristics Of A Subsonic Transport Aircraft Using A Panel Method, Lillianne Plaster Whitelock Troeger

Mechanical & Aerospace Engineering Theses & Dissertations

An advanced low-order panel method, VSAERO, is applied to a full-configuration transport aircraft. Wing pressure distributions as well as lift, drag, and pitching moment coefficients calculated for the full computational configuration are compared with experimental data. In addition, partial configurations are evaluated computationally to determine the relevance of certain complex aircraft components to the computations. It is shown that the wing-surface pressure distributions and pitching moment coefficient are well predicted by VSAERO. The lift coefficient is consistently overpredicted by the code.

Boundary Layer Influences On The Subsonic Near-Wake Of A Family Of Three-Dimensional Bluff Bodies, Charles Willliam Alcorn

Mechanical & Aerospace Engineering Theses & Dissertations

A study is reported on subsonic bluff body near-wake flows. It has been determined that one family of bluff bodies, namely slanted-base ogive cylinders, can experience either a closed recirculating near-wake, or a longitudinal vortex near-wake depending on the base slant-angle and the Reynolds number. This suggests a dependence of near-wake parameters on the state of the boundary layer ahead of separation. This report addresses the influence of the boundary layer on the near-wake of slanted-base bluff bodies. Experiments were conducted in two facilities, the 6-inch Magnetic Suspension and Balance System (MSBS) at NASA Langley Research Center and the Old …

Dynamic Analysis Of A Combat Aircraft With Control Surface Failure, Marc Roy

Theses and Dissertations

An investigation was performed to analyze the dynamic stability characteristic of an aircraft which has sustained damage to a primary control surface. The analysis was performed using the existing functional form of actual wind tunnel data taken on an F-16 model. Two control schemes are used for trimming an F-16 that has sustained damage to its rudder. The first control scheme represent the basic aircraft, while the second allowed the horizontal tail ailerons to move independently from the flaperons. The investigation was conducted for one flight condition representative of the aircraft at cruise speed. Region in α/β (angle of attack)/(sideslip …

Navier-Stokes Analysis Of Cold Gas Scramjet Nozzle-Afterbody Flowfields, Walter C. Engelund

Mechanical & Aerospace Engineering Theses & Dissertations

The recent renewal of interest in hypersonic aerodynamics, brought about largely in part due to the development of the National Aerospace Plane (NASP), is resulting in an increased reliance on computational fluid dynamics for flowfield data in this flight regime. The design of the nozzle-afterbody section for a hypersonic transport such as the NASP is currently underway, and is being conducted using both computational fluid dynamics and cold, non-reacting, simulant gas experimental models. In this study, a computational analysis is conducted for the flow through a scramjet nozzle-afterbody test section.

Computations have been performed for a cold gas simulation of …

Aerodynamic Forces On Flight Crew Helmets, Timothy A. Sestak, Richard M. Howard, Chester A. Heard

Publications

Wind tunnel tests were conducted to deter- mine the aerodynamic forces generated on aircrew flight helmets. Three helmets were tested: two used by aircrews flying ejection seat aircraft in the U.S. military, the Navy HGU-33/P and the Air Force HGU-53/P; and one prototype helmet of significantly different shape and volume. Axial and normal forces were measured through a range of pitch and yaw angles. It was found that large forces exist tending to promote helmet loss during ejection, and that simple modifications to the current helmet configurations can reduce those forces by as much as 40%. It is demonstrated that …