Aerodynamics and Fluid Mechanics Commons^™

Dynamic Supersonic Base Store Ejection Simulation Using Beggar, Michael D. Johnson

Theses and Dissertations

Static and dynamic conditions throughout various aft supersonic store separation events are examined using the Beggar Computational Fluid Dynamics (CFD) code from Air Force SEEK Eagle Office at Eglin Air Force Base, FL. An 8.9 deg half angle sphere cone is used for the carrier vehicle with an identically shaped store stowed within a hollow compartment in the aft section of the carrier body. Dynamic store separation simulations are implemented at a free-stream Mach of 2.9 with a Reynolds number of Re = 6.9 x 10⁶/m referenced against carrier base diameter. Analysis covers multiple dynamic separation events along …

Global Skin Friction Diagnostics In Complex Separated Flows, Sudesh A. Woodiga

Masters Theses

This work describes the application of a global luminescent oil film skin friction meter to quantitative global skin friction diagnostics in complex separated flows. The development of this technique is based on the relationship between the oil film thickness and luminescent intensity of an oil film mixed with a luminescent dye. The projected thin oil film equation is given to relate the normalized luminescent intensity with skin friction. The basis for this technique is the variational solution for the thin oil film equation on the image plane. The variational formulation with a smoothness constraint on skin friction is proposed to …

Numerical Simulation Of Uva Ramjet/Scramjet Hypersonic Engine With Hydrogen-Air Combustion Using Wind-Us, Vishal Anand Bhagwandin

Master's Theses - Daytona Beach

The internal flowpath of University of Virginia's Mach 5, direct-connect, dual-mode scramjet engine was simulated using Wind-US, a density-based Reynolds-Averaged Navier-Stokes flow solver. Detailed flowfield simulation results are directly compared to experimental data to evaluate the accuracy of the numerical model and to provide insight into the flowfield behavior. Four hydrogen-air reaction mechanisms were initially assessed using the Burrows-Kurkov case. An Evans-Schexnayder, 7-specie, 8-reaction set with third body efficiencies was then selected for the scramjet simulations. The scramjet simulations included one fuel-off case and two reacting cases with different equivalence ratios, all with clean, non-vitiated air supply. The strong sensitivity …

Design And Numerical Evaluation Of A Counter- Rotating Compressor In The Absence Of Boundary Layer Control: Part I, Naiara Petralanda

Master's Theses - Daytona Beach

The purpose of this thesis was to design and evaluate a three stage counter-rotating compressor that employed well established design principles and technologies using a phased approach. The objective of the first phase was to generate the preliminary annulus shape and estimate the major parameters by modeling the flow as inviscid and time independent. The second and third phases refined the design approximating the flow using Euler's equations and the Navier-Stokes equations respectively.

The performance predictions decreased as the design move forward and more accurate flow and loss models were used. The final three dimensional analysis, which was limited to …

Study Of The Influence Of Nacelle And Pylon On Aerodynamics Of A New Vu Design, Romain Larose

Master's Theses - Daytona Beach

The purpose of this thesis was to illustrate the influence of the nacelle and pylon on aerodynamics of a new Very Light Jet design, using Computational Fluid Dynamics.

The objective of the first phase was to repair the existing CATIA model in order to facilitate the meshing process.

The second and third phase was to create two meshes: a mesh for the complete model (aircraft with nacelle and pylon), and a second for the aircraft alone.

The two problems have been solved at cruise conditions using Navier-Stokes equations with a second order accuracy.

The model complying with theory, the results …

Computational Solution Of Tail Buffet Response And Active Flow Control, Kaushik Laxmikant Joshi

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, numerical simulation of the multidisciplinary method for prediction and control of vortex induced tail buffeting is studied using delta wing-single tail configuration. Flow conditions are chosen such that wing vortex cores experience vortex breakdown and the resulting wake flow impinges on the vertical tail. The aero/structure problem is solved sequentially using three sets of equations on a multi-block grid structure. To obtain aerodynamic loading on the tail, the fluid flow around the wing-tail assembly is computed by time-accurately solving unsteady, laminar, compressible Navier-Stokes equations using an implicit, upwind, flux-difference splitting finite volume scheme. Then the aeroelastic equations …

Cfd As Applied To The Design Of Short Takeoff And Landing Vehicles Using Circulation Control, Tyler M. Ball

Master's Theses

The ability to predict the distance required for an aircraft to takeoff is an essential component of aircraft design. It involves aspects related to each of the major aircraft systems: aerodynamics, propulsion, configuration, structures, and stability and control. For an aircraft designed for short takeoffs and landings (STOL), designing the aircraft to provide a short takeoff distance, or more precisely the balanced field length (BFL), often leads to the use of a powered lift technique such as circulation control (CC). Although CC has been around for many years, it has never been used on a production aircraft. This is in …

Using Ansys Workbench Computer Environment In Turbomachinery Design Process, Patricia Lynn Bowlds

Master's Theses - Daytona Beach

The main focus of designing turbomachinery is to analyze and optimize the aerodynamic efficiency and structural integrity of the machine. The preferred way to perform aerodynamic and structural analysis is to connect the analyses and shorten the analysis time as much as possible. ANSYS, Inc. provides a comprehensive approach to model fluid structure interaction phenomenon in turbomachinery within the ANSYS Workbench environment. This environment combines a number of software components that conduct blade design, fluid dynamic and structural analyses, and pre- and post-processing including mesh generation and overall performance estimation.

The focus of this study is to apply the ANSYS …

Wing Optimization Technique Based On Vortex Lattice Theory, Santiago Pinzon

Master's Theses - Daytona Beach

An integrated aerodynamic optimization technique based on vortex lattice theory is being proposed. The technique in this work will aim at optimizing the geometric parameters of a general wing with NACA 65-210 airfoil sections under a low speed aerodynamic regime. This will be completed by performing an aerodynamic analysis based on vortex lattice theory with the objective of satisfying a performance index function. This function will seek to optimize the high lift-to-drag ratio of the wing at cruise velocity, while maximizing theoretical cruise range and minimizing wing weight. The optimization method has been developed using MATLAB and the focus of …

Filtered Rayleigh Scattering Measurements In A Buoyant Flow Field, Steven M. Meents

Theses and Dissertations

Filtered Rayleigh Scattering (FRS) is a non-intrusive, laser-based flow characterization technique that consists of a narrow linewidth laser, a molecular absorption filter, and a high resolution camera behind the filter to record images. Gases of different species have different molecular scattering cross-sections that become apparent as they pass through the interrogating laser light source, and this difference is used to discriminate between the different gaseous components. This study focuses on the behavior of a buoyant helium jet exiting horizontally into ambient air, and more specifically this jet’s tendency to form side lobes that are discharged from the core fluid under …

Determination Of Static And Dynamic Stability Derivatives Using Beggar, Michael E. Bartowitz

Theses and Dissertations

The static and dynamic pitch and roll stability derivatives of a finned, axisymmetric missile known as the Basic Finner were examined using a Computational Fluid Dynamics (CFD) approach. Stability derivatives are used to characterize vehicle motion, and knowledge of them is critical to the design of stable uncontrolled vehicles and control systems for controlled vehicles. Using CFD to characterize the motion of new munition designs has the potential to improve overall performance and reduce research and testing costs. The present analysis simulated forced oscillation and free oscillation of the Basic Finner model using the Air Force SEEK EAGLE Office's Beggar …

Characterization And Control Of Carbon Dioxide Seed Particle Image Velocimetry, Bartt G. Greene

Theses and Dissertations

Particle Image Velocimetry (PIV) data was acquired in two separate supersonic wind tunnels with carbon dioxide (CO₂) particles utilized as the seed material. Previous work in clean seeding showed CO₂ could be used as seed material to produce velocity maps. This research provides the first quantitative assessment of particle response, particle size control via purge gas, and scalability using CO₂ particles. A variety of feed tube and shroud configurations, in combination with varying volumetric flow rates of purge air were measured using a laser diffraction device. The CO₂ particles were injected into the stilling chamber …

Piv-Based Examination Of Deep Stall On An Oscillating Air Foil, Daniel E. Fredberg

Theses and Dissertations

A number of studies suggest that the deep stall flow fields produced by a pure-pitch and a pure-plunge oscillating airfoil are equivalent, when effective angles of attack are matched. This assumption is examined using particle image velocimetry (PIV). Sinusoidal oscillations of a pure-plunge and pure-pitch airfoil with matched reduced frequency k = 3.93 and with kinematically equivalent amplitudes of effective angle of attack are comparatively examined using results of PIV in a free surface water tunnel at AFRL/RB, Wright Patterson AFB. Experiments were conducted at Re = 10,000 and Re = 40,000, based on free stream velocity and airfoil chord, …

Extending Cfd Modeling To Near-Continuum Flows Using Enhanced Thermophysical Modeling, Abram E. Claycomb

Theses and Dissertations

The constitutive relations found in traditional Navier-Stokes-based computational fluid dynamics solvers are known to be limited in altitude. The presence of nonequilibrium phenomena beyond what these methods are able to predict becomes more prevalent at higher altitudes, or increasing Knudsen number. The bulk viscosity, normally assumed to be zero in most computational fluid dynamics applications, is examined as a means of increasing the range of applicability of computational fluid dynamics. The bulk viscosity model used was from recent calculations available in the literature, from a new anisotropic potential energy surface, and is restricted to temperatures below 2000 K. The normal …

Experimental Investigation Of Active Control Of Bluff Body Vortex Shedding, Ilteris Koc

Mechanical & Aerospace Engineering Theses & Dissertations

Mean and fluctuating forces acting on a body are strongly related to vortex shedding generated behind it. Therefore, it is possible to obtain substantial reductions of at least the unsteady forces if vortex shedding is controlled or its regularity is reduced. While conventional active flow control methods are mainly concerned with direct interaction with, and alteration of, the mean flow about a body, modern techniques involve altering existing flow instabilities using relatively small inputs to obtain large-scale changes of mean flows. Aerodynamic flow control may be intended to delay or suppress boundary layer separation through creation of a boundary layer …