| Examining Passive Flow Control Devices with High Speed Shadowgraph Images around a Mach 1.5 Cavity Flow Field (Postprint) |
Jun 2012 |
21 pages |
| Authors:
Ryan F Schmit; Frank Semmelmayer; Mitchell Haverkamp; James E Grove; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH AEROSPACE SYSTEMS DIR
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 | An examination of a rectangular cavity with an L/D of 5.67 was tested at Mach 1.5 with a corresponding Reynolds number of 2.3x106/ft. High speed shadowgraph movies were simultaneously sampled with dynamic pressure sensors at 75 kHz. Fourier analysis was performed on the high speed movies as well as the dynamic pressure data, which resulted in determining the locations of dominant cavity frequencies in the flow field. Four passive flow ... |
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| Reynolds Number Effects on Thrust Coefficients and PIV for Flapping Wing Micro Air Vehicles |
09 Mar 2012 |
132 pages |
| Authors:
John P Tekell; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH DEPT OF AERONAUTICS AND ASTRONAUTICS
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| For the last several years the Air Force Institute of Technology (AFIT) has conducted research in aerodynamics for flapping wing micro air vehicles (MAVs). The focus of this research was to augment this effort by measuring thrust, velocity, and torque in tanks of water and glycerin using a scale and a reaction torque cell. The results for different flapping mechanisms are compared to a rotating propeller with the goal of ... |
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| Evaluation of the Thorax of Manduca sexta for Flapping Wing Micro Air Vehicle Applications |
Mar 2012 |
182 pages |
| Authors:
Alex C Hollenbeck; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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| The tobacco hornworm hawkmoth (Manduca sexta) provides an excellent model from which to garner knowledge pertaining to the development of a Flapping Wing Micro Air Vehicle (FWMAV). Insect-sized FWMAVs will be used by the future warfighter for reconnaissance, nuclear/chemical/biological hazard sensing, and targeting. One of the major challenges facing FWMAV developers is the energetically demanding nature of low Reynolds flapping flight. Investigating the Manduca sexta thorax/wing flapping mechanism as a ... |
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| Measurements of the Mechanisms of Laminar-Turbulent Transition in the Mach-6 Quiet Tunnel |
28 Feb 2012 |
38 pages |
| Authors:
Steven P Schneider; PURDUE UNIV LAFAYETTE IN SCHOOL OF AERONAUTICS AND ASTRONAUTICS
|
| The Mach-6 tunnel continues to run quiet to moderately high Reynolds numbers. Quiet flow was degraded in 2010 when the throat was opened, but a thorough repolishing of the throat resulted in a significant improvement in performance. Since the nozzle-wall boundary layer remains laminar more than 10 inches downstream of the exit to unit Reynolds numbers near 3.5 million per foot, unprecedented quiet-flow Reynolds numbers can now be achieved on ... |
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| Direct Numerical Simulations of Very Stable Atmospheric Boundary Layers |
10 Jan 2012 |
7 pages |
| Authors:
Oscar Flores; James J Riley; WASHINGTON UNIV SEATTLE OFFICE OF SPONSORED PROGRAMS
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| The objective of the research is to address a number of outstanding issues related to very stable atmospheric boundary layers, including criteria for the collapse of the turbulence, the intermittent behavior and the strong anisotropy of turbulence, horizontal dispersion and meandering of plumes, and the local scaling of the velocities in terms of predictable or measurable parameters. The approach to the research is direct numerical simulation of stably stratified Ekman ... |
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| On the Propagation of Nonlinear Acoustic Waves in Viscous and Thermoviscous Fluids |
Jan 2012 |
9 pages |
| Authors:
P M Jordan; G V Norton; S A Chin-Bing; A Warn-Varnas; NAVAL RESEARCH LAB STENNIS DETACHMENT STENNIS SPACE CENTER MS
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| Acoustic travelling waves are studied in the context of nonlinear propagation in Newtonian fluids. First we examine the one-dimensional (1D) versions of four weakly-nonlinear acoustic models, all of which admit known travelling wave solutions (TWS)s in the form of Taylor shocks. Next, we derive the exact but implicit, kink-type TWS of the compressible 1D Navier-Stokes equations under the homentropic assumption. Then, using three simple metrics, we numerically compare the TWSs ... |
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| Closed-Loop Control for High Reynolds Number Turbulent Compressible Jets |
14 Dec 2011 |
28 pages |
| Authors:
Mark N Glauser; Jacques Lewalle; SYRACUSE UNIV NY DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
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| From the viewpoint of the PIs, this project has been very successful on several fronts. The data acquisition has yielded good acoustic and PIV records; some effect of jet actuators on farfield noise have been measured through spectra and cross-correlations; POD decomposition of near-field velocity shows that cross-correlations with the far-field noise is accounted for by velocity mode 6 within a particular downstream r- plane window; the wavelet processing of ... |
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| A Technique for Measurement of Static and Dynamic Longitudinal Aerodynamic Derivatives Using the DSTO Water Tunnel |
Dec 2011 |
47 pages |
| Authors:
Daniel M Newman; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION VICTORIA (AUSTRALIA)
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| The DSTO water tunnel's balance and rotary support mechanism provides a measurement capability for longitudinal dynamic derivatives. This report documents the underlying theory and computational implementation of a technique which uses the water tunnel for determination of normal force and pitching moment coe cient derivatives with respect to angle of attack, non-dimensional pitch rate and angle of attack rate. |
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| Vortex-Induced Vibration: Universal Phenomena in Diverse VIV Systems |
28 Nov 2011 |
24 pages |
| Authors:
Charles H Williamson; CORNELL UNIV ITHACA NY DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
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| The long-term goals of the research have been to investigate the important mechanisms involved in the interaction of current and waves with structures in the ocean. We have studied the ultra-high resolution controlled vibration of cylinders in a flow, and have been able to accurately predict free vibration response, as well as to understand free vibration phenomena, by employing energy portrait diagrams. We have constructed an accurate map of force ... |
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| Fundamental Experimental and Numerical Investigation of Active Control of 3-D Flows |
06 Oct 2011 |
24 pages |
| Authors:
Michael Amitary; Kenneth Jansen; RENSSELAER POLYTECHNIC INST TROY NY
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| A combined experimental and numerical work was conducted on the interaction between finite span synthetic jets and a 3-D cross-flow. We completed a series of experimental and numerical simulations of the interaction of the synthetic jets with a cross-flow over unswept and swept configurations. The results show that the interaction results in the formation of secondary flow structures that enhance mixing and increase the efficiency of flow control. We publish ... |
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| Investigation of Transitional Flows on Compressor Blades in Cascade |
Sep 2011 |
111 pages |
| Authors:
Michael L Holihan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| Flow around polished second-generation controlled-diffusion blades in cascade set at their design inlet flow angle was investigated at various Reynolds numbers using static pressure measurements, five-hole probe surveys, twocomponent laser Doppler velocimetry (LDV), computational fluid dynamics and flow visualization. A suction-side separation bubble formed at Reynolds number, based on chord length, of 203,000 and collapsed by a Reynolds number of 393,000. Five-hole probe surveys characterized the blade-row inlet and outlet ... |
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| Study of Varying Boundary Layer Height on Turret Flow Structures |
JUN 2011 |
119 pages |
| Authors:
Renato Jelic; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH DEPT OF AERONAUTICS AND ASTRONAUTICS
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| The Air Force Institute of Technology and the Air Force Research Labs are investigating flows over turrets which are commonly encountered in directed energy integrations with air vehicles. In this work, the computational study was performed using the NASA developed time-marching finite volume code OVERFLOW 2.2 to analyze the effect of boundary layer height on symmetrical and non-symmetrical turret geometries. The effects of aerodynamics yield to the aberration of the ... |
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| Numerical Investigation of Serpentine Plasma Actuators for Separation Control at Low Reynolds Number |
Jun 2011 |
17 pages |
| Authors:
Mark Riherd; Subrata Roy; Miguel Visbal; FLORIDA UNIV GAINESVILLE DEPT OF MECHANICAL ENGINEERING
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| Dielectric Barrier Discharge (DBD) plasma actuators with serpentine shaped electrodes cause a change in the operational behavior of the flow control mechanism relative to the standard linear actuator due to the introduction of fully three dimensional vortices. A parametric study is performed on a partially separated transitional flow over an SD7003 airfoil. This study examines the change in behavior as a function of geometric parameters, in particular the geometric amplitude ... |
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| Effect of Gas Injection on Transition in Hypervelocity Boundary Layers |
05 MAY 2011 |
7 pages |
| Authors:
J. S. Jewell; I. A. Leyva; N. J. Parziale; J. E. Shepherd; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
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| A novel method to delay transition in hypervelocity flows in air over slender bodies by injecting CO2 into the boundary layer is presented. The dominant transition mechanism in hypersonic flow is the inviscid second (Mack) mode, which is associated with acoustic disturbances which are trapped and amplified inside the boundary layer [8]. In dissociated CO2-rich flows, nonequilibrium molecular vibration damps the acoustic instability, and for the high-temperature, high-pressure conditions associated ... |
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| Hypersonic Laminar-Turbulent Transition on Slender Cones at Zero Angle of Attack: Measurements in Support of Mechanism-Based Models for Scaling Ground-Test Data to Flight |
04 Mar 2011 |
18 pages |
| Authors:
Steven P Schneider; PURDUE UNIV LAFAYETTE IN SCHOOL OF AERONAUTICS AND ASTRONAUTICS
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| Maintaining low laminar heating may be critical to hypersonic gliding reentry vehicles such as the several which have been proposed for the Prompt Global Strike (PGS) mission. However, no single ground test can duplicate the Mach number, Reynolds number, enthalpy, surface temperature, scale, roughness, ablation and freestream noise of flight; thus, ground-test measurements oflaminar-turbulent transition must be compared and extrapolated to flight using analysis. Fortunately, the first mechanism-based prediction methods ... |
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| Summary of Two Independent Performance Measurements of the ONR Axial Waterjet 2 (AxWJ-2) |
MAR 2011 |
44 pages |
| Authors:
Matthew W. Marquardt; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD
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| This report presents the experimental axial flow waterjet measurements of the ONR AxWJ-7 conducted by Rolls Royce Naval Marine and the Naval Surface Warfare Center Carderock Division. While the details and the data of these two experiments can be found in separate reports, the purpose of this document is to provide an all-in-one comparison of their findings, to be used by researchers across the hydrodynamic field in the public domain. ... |
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| Perching Experiment at Low Reynolds Number: Force and PIV Measurements of Rectangular Flat Wing Models in Perching Motion |
10 NOV 2010 |
73 pages |
| Authors:
Rolf E. Radespiel; TECHNICAL UNIV BRAUNSCHWEIG (GERMANY) INST OF FLUID MECHANICS
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| This report comprises aerodynamic measurements of a wing in perching motion carried out with the MAVlab facility at the Institute of Fluid Mechanics of Braunschweig University. In this context, the perching motion is modeled according to the wing motions of birds to rapidly reduce velocity when landing on a small spot i.e. a perch. The here discussed perching motion is defined as a discontinuous pitching of a wing from low ... |
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| Dynamics of Vorticity Defects in Stratified Shear |
19 Oct 2010 |
34 pages |
| Authors:
Anubhad Roy; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| Stability of shear flows at high Reynolds number has been one of the cornerstones of hydrodynamic stability. A canonical problem which contains the basic features is that of a shear layer - two streams of different velocity owing past each other with different density. Helmholtz[18] and Kelvin[21] were probably the earliest to consider evolution of disturbances in a stratified vortex sheet. While attempting a more general case Rayleigh[27] approximated the ... |
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| Dynamics of the Mixed Layers in Stratified Sheared Flows |
18 Oct 2010 |
21 pages |
| Authors:
Georgy Manucharyan; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| Vast verity of geophysical flows occur in density stratified fluids in a presence of sheared mean velocity profiles. Under such conditions it's been observed that vigorous turbulence leads to generation of mixed layers within the fluid, e.g. the regions of homogeneous density separated from each other by strong density gradients (interfaces). These layers could be of large vertical scales as well as of fine scales. An example of such flows ... |
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| Hybrid LES/RANS Simulation of the Effects of Boundary Layer Control Devices Using Immersed Boundary Methods |
22 FEB 2010 |
76 pages |
| Authors:
Jack R. Edwards; NORTH CAROLINA STATE UNIV AT RALEIGH
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| This work has developed an extension of an existing immersed-boundary (IB) method to compressible, turbulent flows and has investigated its use in simulating the effects of different types of flow control devices: micro vortex generators, bleed-hole arrays, aeroelastically-deforming "mesoflaps", and boundary layer trips. The IB method has been used with Reynolds-averaged Navier-Stokes (Menter SST) and hybrid large-eddy simulation / Reynolds averaged Navier-Stokes (LES/RANS) turbulence closures. The method has been applied ... |
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| High-Fidelity Simulations of Moving and Flexible Airfoils at Low Reynolds Numbers (Postprint) |
Feb 2010 |
22 pages |
| Authors:
Miguel R Visbal; Raymond E Gordnier; Marshall C Galbraith; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH AIR VEHICLES DIR/ AERONAUTICAL SCIENCES DIV/COMPUTATIONAL SCIENCES BRANCH
|
| The present paper highlights results derived from the application of a high-fidelity simulation technique to the analysis of low-Reynolds-number transitional flows over moving and flexible canonical configurations motivated by small natural and man-made flyers. This effort addresses three separate fluid dynamic phenomena relevant to small fliers, including: laminar separation and transition over a stationary airfoil, transition effects on the dynamic stall vortex generated by a plunging airfoil, and the effect ... |
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| On the Impact of Injection Schemes on Transition in Hypersonic Boundary Layers |
13-Oct-2009 |
12 pages |
| Authors:
Ivett A Leyva; Stuart Laurence; Hans G Hornung; Joseph S Jewell; Joe Shepherd; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
| Three geometries are explored for injecting CO2 into the boundary layer of a sharp five degree half-angle cone. The impact of the injection geometry, namely discrete injection holes or a porous conical section, on tripping the boundary layer is examined, both with and without injected flow. The experiments are conducted at Caltech's T5 reflected shock tunnel. Two different air free-stream conditions are explored. For the discrete-hole injectors, the diameter for ... |
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| CFD Prediction of Magnus Effect in Subsonic to Supersonic Flight |
Sep-2009 |
46 pages |
| Authors:
James DeSpirito; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| The aerodynamic coefficients of the 7-cal. U.S. Army-Navy Spinner Rocket were characterized using computational fluid dynamic (CFD) calculations and validated using archival experimental data. The static aerodynamic coefficients, roll-damping, and pitch-damping moments were accurately predicted by steady-state Reynolds-averaged Navier-Stokes (RANS) as well as unsteady hybrid RANS/large-eddy simulation (LES) CFD. The Magnus moment was overpredicted in the subsonic and transonic regime. Unsteady RANS/LES computations did not improve the prediction of Magnus ... |
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| An Overview of Advanced Concepts for Near-Space Systems |
30-Jun-2009 |
|
| Authors:
Marcus Young; Anthony Pancotti; Stephanie Keith; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
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 | A brief review of both near-term and far-term platforms proposed for near-space operations is given. The primary focus of the paper is, however, a review of potential advanced propulsion systems for such long-duration near-space platforms. The basic requirements for near-space propulsion systems are defined. Low Reynolds number propellers, the current workhorse, are used as a baseline for comparison. Two broad classifications are identified as potential sources of force in near ... |
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| Measurements of the Effectiveness of Concave Spherical Dimples for Enhancement of Hot-gas Side Heat Transfer |
02-Jun-2009 |
10 pages |
| Authors:
Stephen A Danczyk; Edward B Coy; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| Measurements of the heat transfer enhancement effects of concave spherical dimples have been performed under hydrogen-oxygen hot-fire conditions in a subscale combustion chamber. Seven configurations were tested with a range of area densities from 15-70% and depth to diameter ratios of 0.111 to 0.333. Enhancements of 15-82% relative to a smooth surface were measured. Reynolds number was varied by a factor of 5 and was found to have an insignificant ... |
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| Flow Visualization Studies over a UCAV 1303 Model |
Jun-2009 |
58 pages |
| Authors:
Weng H Chua; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This study is a qualitative documentation of the main flow features over an Unmanned Combat Air Vehicle (UCAV) 1303 model by flow visualization techniques where it gives the first understanding of the UCAV maneuverability under steady and unsteady maneuver conditions. The relevant fluid flow physics is not available presently and, hence, this thesis concentrated on generating those critical details. Towards this goal, model studies were conducted on the United States ... |
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| Wind Tunnel Analysis And Flight Test of A Wing Fence On A T-38 |
26-Mar-2009 |
267 pages |
| Authors:
Michael D Williams; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH DEPT OF AERONAUTICS AND ASTRONAUTICS
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| A low-speed wind tunnel study and flight tests were performed to examine the effects of a wing fence on the T-38A. Wind tunnel results were based upon force and moment data collected with a six-component balance and flow visualization at Reynolds numbers up to 0.3 x 10(exp 6), based on mean aerodynamic chord. The model did not include the last 7.79 feet of the aircraft, and the engine and exhaust ... |
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| Super Maneuverable, Flapping Wing Micro-Air-Vehicles |
16-Mar-2009 |
28 pages |
| Authors:
B Balachandran; E Balaras; Marcos Vanella; Timothy Fitzgerald; Sergio Preidikman; MARYLAND UNIV COLLEGE PARK DEPT OF MECHANICAL ENGINEERING
|
| Interest in the development of super-maneuverable, micro-air-vehicles has led to the re-examination of basic flight modes, particularly, those that are inspired by biological observations. The majority of experimental and numerical studies related to flapping flight have explored the relationships between the thrust coefficient (and propulsive efficiency) and wing geometry and kinematics. Relatively speaking, the wing flexibility and the interplay between kinematics and flexibility have received less attention, and currently, it ... |
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| Interface Conditions for Hybrid RANS/LES Simulations of Complex and Compressible Flows |
06-Mar-2009 |
31 pages |
| Authors:
Ugo Piomelli; Elias Balaras; MARYLAND UNIV COLLEGE PARK DEPT OF MECHANICAL ENGINEERING
|
| We have demonstrated the applicability of synthetic turbulence coupled with the controlled-forcing method to generate eddies at the interface between RANS and LES in hybrid calculations. We obtained shorter transition regions and improved model accuracy. Realistic turbulence can be generated within 5 boundary-layer thicknesses of the RANS/LES interface even in cases in which the data supplied by the RANS is inaccurate, or the assumptions on which the forcing is based ... |
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| Tools for the Conceptual Design and Engineering Analysis of Micro Air Vehicles |
Mar-2009 |
156 pages |
| Authors:
Mustafa Turan; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
|
| Micro Air Vehicles (MAV) are a subset of Unmanned Aircraft (UAS) that are up to two orders of magnitude smaller than manned systems. Near-Earth environments, such as forests, caves, tunnels and urban structures make reconnaissance, surveillance and search-and-rescue missions difficult and dangerous to accomplish. Therefore, MAVs are considered ideal for these types of missions. However, the data using full size aircraft is inadequate to characterize miniature aircraft parameters due to ... |
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| An Experimental Investigation Studying the Influence of Dimples on a Film Cooled Turbine Blade Leading Edge |
Mar-2009 |
171 pages |
| Authors:
Paul G Frisinger; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| An investigation was conducted to examine the effect of a row of cylindrical surface dimples in reducing the heat load on a turbine blade leading edge model. The models consisted of a foam cylindrical leading edge with a flat afterbody fabricated from Plexiglass. A single coolant hole was located 21.5? from the leading edge, angled 20? to the surface and 90? from the streamwise direction. The leading edge diameter to ... |
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| Towards High-Reynolds Number Quiet Flow in Hypersonic Tunnels |
23-Feb-2009 |
17 pages |
| Authors:
Doyle D Knight; Hadassah Naiman; RUTGERS - THE STATE UNIV NEW BRUNSWICK NJ DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
|
| The report summarizes a research program focused on two main issues related to the achievement of high Reynolds number quiet flow in hypersonic tunnels, namely, 1) automated optimal design of quiet hypersonic tunnels, and 2) tunnel startup in the presence of blunt models. In the former case, a fully automated optimal design methodology was developed to determine the optimal shape of the supersonic nozzle to achieve laminar flow on the ... |
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| Nonlinear Structures Optimization for Flexible Flapping Wing MAVs |
Feb-2009 |
19 pages |
| Authors:
Robert L Jr; Walker; Craig E Svanberg; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH AIR VEHICLES DIRECTORATE
|
| This report documents the culmination of in-house and AFIT collaboration in the area of nonlinear structures optimization for flexible flapping wing MAVs. The work was divided into four different tasks, including: Preliminary design of flapping wing device, Couple Abaqus with aerodynamic model, Comparison of experimental and computational results, and Evaluate CSIRF progress for transition to FY09 6.2 program. Technology developed in this task is being transitioned in the VAES program ... |
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| Turbulent Boundary Layers on a Systematically Varied Rough Wall |
JAN 2009 |
10 pages |
| Authors:
Michael P. Schultz; Karen A. Flack; NAVAL ACADEMY ANNAPOLIS MD DEPT OF NAVAL ARCHITECTURE OCEAN AND MARINE ENGINEERING
|
| Results of an experimental investigation of the flow over a model roughness are presented. The series of roughness consists of close-packed pyramids in which both the height and the slope were systematically varied. The aim of this work was to document the mean flow and subsequently gain insight into the physical roughness scales which contribute to drag. The mean velocity profiles for all nine rough surfaces collapse with smooth-wall results ... |
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| Transition Delay in Hypervelocity Boundary Layers by Means of CO2/Acoustic Instability Interactions |
08-Dec-2008 |
52 pages |
| Authors:
Ivett A Leyva; Stuart Laurence; Amy W Beierholm; Hans G Hornung; Ross Wagnild; Graham Candler; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
| A novel method to delay transition in hypervelocity flows over slender bodies by injecting CO2 into the boundary layer of interest is investigated. The results presented here consist of both experimental and computational data. The experimental data was obtained at Caltech's T5 reflected shock tunnel, while the computational data was obtained at the University of Minnesota. The experimental model was a 5 degree sharp cone, chosen because of its relevance ... |
|
| Measurements of the Effectiveness of Concave Spherical Dimples for Enhancement of Hot-gas Side Heat Transfer (Preprint) |
04-Dec-2008 |
10 pages |
| Authors:
Stephen A Danczyk; Edward B Coy; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
| Measurements of the heat transfer enhancement effects of concave spherical dimples have been performed under hydrogenoxygen hot-fire conditions in a subscale combustion chamber. Seven configurations were tested with a range of area densities from 15-70% and depth to diameter ratios of 0.111 to 0.333. (Additional quantitiative results will included in the form of heat transfer coefficients and Stanton number.) Enhancements of 15-82% relative to a smooth surface were measured. Reynolds ... |
|
| Capabilities for Magnus Prediction in Subsonic and Transonic Flight |
Dec-2008 |
9 pages |
| Authors:
J DeSpirito; S I Silton; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| The Magnus characteristics of three spin-stabilized projectiles were characterized using steady-state RANS and time-accurate RANS/LES computational fluid dynamic simulations. RANS/LES simulations improved the Magnus moment prediction for projectiles with rounded or chamfered bases. No difference was found between the RANS and RANS/LES simulations for the projectile with a sharp-cornered base?either with or without a boattail. The near-body flow field was similar for RANS and RANS/LES simulations; but the RANS/LES simulations ... |
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| DNS and RANS Simulation of Dispersion Downstream of an Obstacle |
Dec-2008 |
9 pages |
| Authors:
Gianluca Iaccarino; Riccardo Rossi; BOLOGNA UNIV (ITALY)
|
| Dispersion in the wake of an obstacle is studied as a step towards the analysis of bio-agent release in urban environments. Available experimental measurements are used to compare in details numerical predictions obtained using Reynolds-Averaged Navier-Stokes (RANS) techniques and Direct Numerical Simulations (DNS). In particular, turbulent scalar fluxes are compared to assess the quality of simple closure based on eddy diffusivity assumptions. The results obtained using different RANS closures show ... |
|
| Unique Stealth Unmanned Aerial Vehicle (UAV) Houck Aircraft Design Program. Volume 2: Prototype Report |
Nov-2008 |
149 pages |
| Authors:
Timothy Fry; DAYTON UNIV OH
|
| This report covers the collaborative activities conducted under the leadership of the University of Dayton Research Institute on the Unique Stealth Unmanned Aerial Vehicle (UAV) Houck Aircraft Design Program. This was organized in five phases: aerodynamic evaluation of 6-inch model; aerodynamic evaluation of 24-inch model; design exploration for the Preferred System Concept; design of Preferred System Concept; and fabrication of flying prototype aircraft. Overall, this configuration, as modeled, was found ... |
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| Transition Delay in a Hypervelocity Boundary Layer using Nonequilibrium CO2 Injection |
28-Oct-2008 |
132 pages |
| Authors:
Amy K Beierholm; Ivett Leyva; S J Laurence; J Jewel; H G Hornung; CALIFORNIA INST OF TECH PASADENA GRADUATE AERONAUTICAL LABS
|
| A new technique to delay transition to turbulence in hypervelocity air flows is introduced and investigated in this work. The main motivation for such a technique is the pressing need to reduce aerodynamic heating rates on hypersonic vehicles. Turbulent heat transfer rates can be an order of magnitude higher than laminar rates at hypersonic Mach numbers. Hence, schemes to delay transition to turbulence could provide an important means to reduce ... |
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| Combined Effects of Wakes and Jet Pulsing on Film Cooling |
OCT 2008 |
13 pages |
| Authors:
Kristofer M. Womack; Ralph J. Volino; Michael P. Schultz; NAVAL ACADEMY ANNAPOLIS MD DEPT OF MECHANICAL ENGINEERING
|
| Pulsed film cooling jets subject to periodic wakes were studied experimentally. The wakes were generated with a spoked wheel upstream of a flat plate. Cases with a single row of cylindrical film cooling holes inclined at 35 deg to the surface were considered at blowing ratios B of 0.50 and 1.0 with jet pulsing and wake Strouhal numbers of 0.15, 0.30, and 0.60. Wake timing was varied with respect to ... |
|
| RDHWT/MARIAH II Hypersonic Wind Tunnel Research Program |
01-Sep-2008 |
165 pages |
| Authors:
M L Laster; C C Limbaugh; J L Jordan; AEROSPACE TESTING ALLIANCE (ATA) ARNOLD AFB TN
|
| The U.S. Air Force sponsored and the USAF Arnold Engineering Development Center directed the Radiantly Driven Hypersonic Wind Tunnel (RDHWT)/ Magnetohydrodynamic Accelerator Research Into Advanced Hypersonics (MARIAH II) Program. This report primarily covers the research for the period from January 2001 through July 2004. The scope of the research program was to develop enabling technologies for a medium-scale hypersonic wind tunnel (MSHWT) that would provide a Mach 8 to 15 ... |
|
| Pylon Effects on a Scramjet Cavity Flameholder Flowfield |
01-Sep-2008 |
204 pages |
| Authors:
Andrew B Freeborn; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
|
| Cavity flameholders in supersonic combustion ramjet (scramjet) combustors, while effective, fail to take advantage of the full combustor volume. Adding a pylon to the leading edge of a cavity flameholder generates a flowfield increasing mass exchange between the cavity and main combustor flow, increasing the mixing interface between flameholder products and main combustor flow, and exhibiting minimal Reynolds number effects. To demonstrate this modified flowfield driven by supersonic expansion behind ... |
|
| Mass Remaining During Evaporation of Sessile Drop |
01-Sep-2008 |
35 pages |
| Authors:
James E Danberg; SCIENCE APPLICATIONS INTERNATIONAL CORP (SAIC) ABINGDON MD
|
| A theory to predict the evaporation rate of HD (mustard agent) for the special case of a glass substrate has been developed. This is an important reference case for the wind tunnel and field test measurements of the HD evaporation rate. The HD drop is treated as a spherical segment with a constant base diameter characterized by the variation of the droplet shape factor (height to base diameter) or contact ... |
|
| A High-Order, Adaptive, Discontinuous Galerkin Finite Element Method for the Reynolds-Averaged Navier-Stokes Equations |
01-Sep-2008 |
184 pages |
| Authors:
Todd A Oliver; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF AERONAUTICS AND ASTRONAUTICS
|
| This thesis presents high-order, discontinuous Galerkin (DG) discretizations of the Reynolds-Averaged Navier-Stokes (RANS) equations and an output-based error estimation and mesh adaptation algorithm for these discretizations. In particular, DG discretizations of the RANS equations with the Spalart-Allmaras (SA) turbulence model are examined. The dual consistency of multiple DG discretizations of the RANS-SA system is analyzed. The approach of simply weighting gradient dependent source terms by a test function and integrating ... |
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| Minimum Pressure Envelope Cavitation Analysis Using Two-Dimensional Panel Method |
01-Jun-2008 |
102 pages |
| Authors:
Christopher J Peterson; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MECHANICAL ENGINEERING
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| An analysis tool for calculating minimum pressure envelopes was developed using XFOIL. This thesis presents MATLAB(registered) executables that interface with a modified version of XFOIL for determining the minimum pressure of a foil operating in an inviscid fluid. The code creates minimum pressure envelopes, similar to those published by Brockett (1965). XFOIL, developed by Mark Drela in 1986, is a design system for Low Reynolds Number Airfoils that combines the ... |
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| Active and Passive Control of Supersonic Wakes: Numerical Investigations using DNS and LES |
Jun-2008 |
41 pages |
| Authors:
Hermann F Fasel; ARIZONA UNIV TUCSON
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| At supersonic speed the base drag of blunt axisymmetric bodies can makeup a substantial fraction of the total drag. A reduction of the base drag is highly desirable as it would considerably improve aerodynamic performance. We employed computational fluid dynamics for investigating transitional supersonic axisymmetric wakes at a freestream Mach number of M=2.46 and a Reynolds number based on diameter of Re_D=100,000. For these simulations, to lower the grid resolution ... |
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| Heat Transfer Measurements for a Film Cooled Turbine Vane Cascade |
01-May-2008 |
26 pages |
| Authors:
Douglas R Thurman; Philip E Poinsatte; James D Heidmann; ARMY RESEARCH LAB CLEVELAND OH VEHICLE TECHNOLOGY DIRECTORATE
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| Experimental heat transfer and pressure measurements were obtained on a large scale film cooled turbine vane cascade. The objective was to investigate heat transfer on a commercial high pressure first stage turbine vane at near engine Mach and Reynolds number conditions. Additionally blowing ratios and coolant density were also matched. Numerical computations were made with the Glenn-HT code of the same geometry and compared with the experimental results. We used ... |
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| Semi-Analytical Approach to Three-Dimensional Shape Optimization Problems |
APR 2008 |
21 pages |
| Authors:
Michael Zabarankin; STEVENS INST OF TECH HOBOKEN NJ
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| A semi-analytical approach to three-dimensional (3-D) shape optimization problems for a viscous incompressible fluid under the assumption of zero (low) Reynolds number has been developed. It couples the theory of generalized analytic functions with the adjoint equations-based method. A solution to Stokes equations governing the behavior of the fluid has been reduced to integral equations based on the Cauchy integral formula for k-harmonically analytic functions. The fluid velocity and boundary ... |
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| Turbulent Mixing in Stably Stratified Flows |
01-Mar-2008 |
101 pages |
| Authors:
MASSACHUSETTS UNIV AMHERST
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| High resolution direct numerical simulations are used to investigate the dynamics of turbulence in flows subject to strong stable stratification, which are common in natural settings. Results are presented for two categories of simulations, uniform and non-uniform density stratification. For all simulated flows, the density stratification was held constant in time, and there was no ambient shear. Flows with uniform density stratification are first analyzed to help provide clear insight ... |
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