| Development of a Versatile Conditioning Wind Tunnel for Evaporative Fate Studies |
Oct-2009 |
63 pages |
| Authors:
H D Durst; James E Danberg; Daniel J Weber; Daniel Waysbort; Clayton S Moury; EDGEWOOD CHEMICAL BIOLOGICAL CENTER ABERDEEN PROVING GROUND MD
|
 | This report documents the development of a conditioning wind tunnel that allows multiple test samples to be conditioned at identical environmental settings that are used in smaller vapor sampling wind tunnels. The conditioning of multiple samples, especially those involving persistent chemicals, allows for the efficient use of a limited number of instrumented vapor sampling tunnels. Up to nine samples can be sequentially and quickly cycled through the instrumented vapor wind ... |
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| U.S. Army Research Laboratory Meteorological Measurements for Joint Urban 2003 |
Sep-2009 |
90 pages |
| Authors:
David Ligon; Cheryl Kipp; Doyule S Elliott; Ed Creegan; San Chang; Manny Bustillos; Dennis Garvey; Giap Huynh; Ronald Cionco; Edward Measure; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| The Joint Urban 2003 (JU2003) project, a multi-agency undertaking to study turbulent transport and diffusion in the urban boundary layer, was conducted in Oklahoma City, OK, in summer 2003. The field campaign involved extensive meteorological and gas tracer measurements to investigate the dispersion of simulated contaminants in and around the city. Instrumentation provided by the U.S. Army Research Laboratory's (ARL) Battlefield Environment Division (BED) included a Doppler lidar, a mobile ... |
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| Resurgent Russia in 2030. Challenge for the USAF |
Sep-2009 |
101 pages |
| Authors:
Mark Butler; Theodore C Hailes; Ronald Buckley; David Blanks; Phillip Preen; Michael Tarlton; AIR UNIV MAXWELL AFB AL
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| Russia has had a turbulent history, and those experiences have had an indelible influence on the nation as it moved from its tsarist past, through the Soviet interregnum, to its brief flirtation with democracy. These traditions and cultural pressures have instilled in the Russian psyche a belief that strives for stability and seeks strong leadership. Furthermore, Russia tends to value stability and its proclivity for strong leadership even when these ... |
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| Moored Observations to Define the Structure and Energetics of Non-Linear Internal Wave Generation over the New Jersey Shelf |
Aug-2009 |
10 pages |
| Authors:
Jonathan D Nash; OREGON STATE UNIV CORVALLIS COLL OF OCEANIC AND ATMOSPHERIC SCIENCES
|
| Non-Linear Internal Wave (NLIW) packets are ubiquitous, yet they arrive with a high degree of irregularity in coastal oceans. Through this award, three water-column moorings and four bottom landers were deployed during the New Jersey Shelf Shallow Water 2006 (SW06) experiment. These moorings span the generation region for NLIWs and have been used to (1) quantify the structure, energetics, and timing of O(100) wave packets, (2) elucidate wave formation, the ... |
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| Quantum Enhanced Imaging by Entangled States |
Jul-2009 |
123 pages |
| Authors:
Doyle Nichols; NORTHROP GRUMMAN SYSTEMS CORP LINTHICUM HEIGHTS MD
|
| The use of entangled states in a prospective standoff imaging sensor has been explored. Specifically, the question of whether enhanced performance (in terms of achievable resolution, in particular) may be obtained through the use of entangled states in a ghost imaging configuration has been investigated. The resiliency of such a system in the presence of transmission impairments that necessarily accompany sensors in a tactical environment, such as large optical loss, ... |
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| Progress Toward a Multidimensional Representation of Mortar Interior Ballistics |
Jun-2009 |
38 pages |
| Authors:
John R Schmidt; Michael J Nusca; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| Lumped-parameter interior ballistics (IB) codes have had limited success in simulating the IB of mortars due to the complex nature of the firing event. Only near the end of the firing event does the mortar conform to the conventional ballistics model for which lumped-parameter codes were designed. Modified lumped-parameter models are capable of simulating some key mortar variables. There are significant pressure waves developed in mortars, which are due in ... |
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| Flow Simulations: The Lagrangian Averaged Navier-stokes Equations and Optimization |
19-May-2009 |
11 pages |
| Authors:
Kamran Mohseni; COLORADO UNIV AT BOULDER DEPT OF AEROSPACE ENGINEERING SCIENCES
|
| This project had two objectives in using Lagrangian techniques and their application in flows. The first research thrust area was to develop a modeling technique that will allow for efficient computation of compressible flows which could include simulations involving both shock and turbulent behavior. Spatial averaging of the nonlinear convective term was applied to the Burgers and Euler equations. The second research thrust area was the development of Lagrangian averaging ... |
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| Non-linear Internal Wave Evolution in the South China Sea: 2005 Field Program |
01-May-2009 |
6 pages |
| Authors:
Robert Pinkel; SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA MARINE PHYSICAL LAB
|
| This program funded by the Office of Naval Research under grant N00014-05-1-0140 is a 2005 field program (SCS05), where our primary challenge was to see if the waves arriving at the western slopes of the South China Sea were in fact, propagating trans-basin from generating sites to the east. |
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| Characterizing the Turbulent Wind Flow Near a Wind Barrier Using a Data Set Collected with an Array of Sonic Anemometers |
May-2009 |
28 pages |
| Authors:
David Quintis; Sean D'Arcy; Robert Brice; David Tofsted; Jimmy Yarbrough; Yansen Wang; Scott Elliott; Thomas Truong; Michael Davalos; ARMY RESEARCH LAB ADELPHI MD COMPUTATIONAL AND INFORMATION SCIENCES DIRECTORATE
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| An array of 10 sonic anemometers was used to observe the mean wind and turbulence near an artificial wind barrier at the High Speed Test Track facility on Holloman Air Force Base, NM. In order to test the effectiveness of such barriers in reducing cross-track winds, a prototype barrier was constructed using a polyester screen material rated as providing 30% porosity. The barrier dimensions were 100 m in length and ... |
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| Detached-Eddy Simulation of Flow Non-Linearity of Fluid-Structural Interactions Using High Order Schemes |
May-2009 |
199 pages |
| Authors:
Gecheng Zha; Baoyuan Wang; MIAMI UNIV CORAL GABLES FL DEPT OF MECHANICAL ENGINEERING
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| The objective of this research is to develop an efficient and accurate methodology to resolve flow non-linearity of fluid-structural interaction. To achieve this purpose, a numerical strategy to apply the detached-eddy simulation (DES) with a fully coupled fluid-structural interaction model is established for the first time. The following novel numerical algorithms are also created: a general sub-domain boundary mapping procedure for parallel computation to reduce wall clock simulation time, an ... |
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| A Preliminary Comparison of Daylit and Night C(2/n) Profiles Measured by Thermosonde |
20-Apr-2009 |
9 pages |
| Authors:
John R Roadcap; Paul Tracy; AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE
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| The refractive index structure constant C(2/n) is needed to characterize optical wave propagation in a refractive turbulent scattering medium. A limited number of in situ measurements of C(2/n) made during day and night conditions from the surface to 10 km above sea level are compared in three different atmospheric boundary layer environments: dry convective, moist convective, and marine inversion. C(2/n) on average appears to be higher through the convective boundary ... |
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| Next Generation Modeling for Deep Water Wave Breaking and Langmuir Circulation |
Apr-2009 |
6 pages |
| Authors:
Eric D Skyllingstad; OREGON STATE UNIV CORVALLIS COLL OF OCEANIC AND ATMOSPHERIC SCIENCES
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| The long-range goal is to improve our ability to understand and predict surface waves, wave breaking, and the transfer of momentum between the atmosphere and ocean. The objectives of our research are to use two free-surface, three-dimensional, turbulent, computational fluid dynamics models to investigate and quantify the interaction between surface waves and upper ocean turbulence. The models are to be tested in comparison with equivalent laboratory experiments conducted in the ... |
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| Chemical Modeling for Large-Eddy Simulation of Turbulent Combustion |
31-Mar-2009 |
41 pages |
| Authors:
Heinz Pitsch; LELAND STANFORD JUNIOR UNIV CA
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| In the present project the focus was on developing advanced combustion models for large-eddy simulations (LES) and to develop automatic chemistry reduction techniques and reduced chemical mechanisms for JP-8 surrogate fuels. The aim of the combustion LES modeling part was to advance the models for non-premixed and premixed combustion towards a generalized combustion model that covers all combustion regimes. Towards this end, for the premixed regime, a dynamic model for ... |
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| Radar Observations of Turbulence Using MST and FMCW Radar (BRIEFING CHARTS) |
09-Mar-2009 |
20 pages |
| Authors:
Frank D Eaton; Gregory D Nastrom; NASTROM CONSULTING LLC SAINT CLOUD MN
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| Radar observation of turbulence using MST and FMCW radar. |
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| Wave Optics Simulation of Optically Augmented Retroreflections for Mononstatic/Bistatic Detection |
Mar-2009 |
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| Authors:
Tatar; John J III; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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 | Optical devices interrogated with a laser in the appropriate band can exhibit strong, deterministic reflections of the incident beam. This characteristic could be exploited for optical target detection and identification. The distribution of reflected power is strongly dependent on the geometry of the interrogation scenario, atmospheric conditions, and the cross section of the target optical device. Previous work on laser interrogation systems in this area has focused on analytic models ... |
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| Assessment of Weather Sensitivites and Air Force Weather (AFW) Support to Tactical Lasers in the Lower Troposphere |
Mar-2009 |
83 pages |
| Authors:
Francesco J Echeverria; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT/DEPT OF ENGINEERING PHYSICS
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| ATL scientists need to develop a full understanding of the interaction effects between a high-energy laser beam and the atmosphere through which it propagates. Achieving this understanding is important for many reasons. In particular, the high cost of DE weapons systems makes each propagation event expensive. Having an understanding of the atmosphere in which a high-energy laser propagates will increase efficiency and effectiveness of the ATL weapon system, which in ... |
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| Adaptive Control Of Woofer-Tweeter Adaptive Optics |
Mar-2009 |
82 pages |
| Authors:
Jimmie J Perez; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| Adaptive optics applies advanced sensing and control to improve the ability of optical systems to collect images through a turbulent atmosphere. The results of this research effort demonstrate that the combination of two recent approaches improves the performance of adaptive optics in directed energy and laser communication scenarios. The first approach is adaptive control, which offers improved performance over fixed-gain controllers in the presence of rapidly changing turbulence. The second ... |
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| Tunable Diode Laser Absorption Spectroscopy Verification Analysis for Use in the Combustion Optimization and Analysis Laser Laboratory |
Mar-2009 |
125 pages |
| Authors:
Christina R Serianne; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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| The AFIT Combustion Optimization and Analysis Laser (COAL) laboratory has state-of-the-art laser diagnostic capability for combustion process. The research for this thesis served to enhance the COAL lab's capability. Currently, there are no known commercially available tunable diode lasers that produce Ultra-Violet radiation required for this analysis. Sum-frequency generation at 313.5 nm was utilized for high speed OH absorption and temperature measurements at a rate of 2kHz. The Tunable Diode ... |
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| Polymer Drag Reduction and Bioluminescence Reduction |
Mar-2009 |
9 pages |
| Authors:
Michael I Latz; CALIFORNIA UNIV REGENTS SAN DIEGO LA JOLLA CA
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| Drag reducing polymers interfere with the bursting process in turbulence by absorbing the energy like a shock absorber. The objective of this project was to test the effect of the polymer drag reducing agent polyethylene oxide (PEO) on bioluminescence stimulation in fully-characterized pipe flow. The well-documented reduction of turbulent skin friction by PEO was hypothesized to also result in a similar reduction of flow-stimulated bioluminescence. Drag reduction and bioluminescence suppression ... |
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| A Computational Tool for Evaluating THz Imaging Performance in Brownout Conditions at Land Sites Throughout the World |
Mar-2009 |
65 pages |
| Authors:
Seth L Marek; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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| This study quantifies terahertz (THz) or sub-millimeter imaging performance during simulated rotary-wing brownout or whiteout environments based on geographic location and recent/current atmospheric weather conditions. The atmospheric conditions are defined through the Air Force Institute of Technology Center for Directed Energy (AFIT/CDE) Laser Environmental Effects Definition and Reference or LEEDR model. This model enables the creation of vertical profiles of temperature, pressure, water vapor content, optical turbulence, and atmospheric particulates ... |
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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
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| 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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| Demonstration and Verification of a Broad Spectrum Anomalous Dispersion Effects Tool for Index of Refraction and Optical Turbulence Calculations |
Mar-2009 |
119 pages |
| Authors:
J J Cohen; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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| An atmospheric optical turbulence strength model with a broad wavelength range of 355nm (ultraviolet) to 8.6m (radio frequencies) has been created at AFIT and implemented into the High Energy Laser End-to-End Operational Simulation tool (HELEEOS). This modeling and simulation tool is a first principles atmospheric propagation and characterization model. Within HELEEOS lies the High-Resolution Transmission Molecular Absorption (HITRAN) database, containing 1,734,469 spectral lines for 37 different molecules as of version ... |
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| Efficient Simulation and Novel Modeling by Using Generic Three-Dimensional Exact Solutions to Analyze Transport Dynamics in Turbulent Vortices |
28-Feb-2009 |
17 pages |
| Authors:
Sukalyan Bhattacharya; TEXAS TECH UNIV LUBBOCK
|
| In this project, we have formulated an alternative boundary-layer theory. This new analysis will be able to mathematically describe flow-separation unlike the classical theory. In our research, we have partially validated the developed theory and concluded that approach has considerable potential to account for flow-separation. The effective description of separated flow can potentially lead to a fast simulation-algorithm for aerodynamic computation. Our estimate predicts that this semianalytical scheme will compute ... |
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| Filtered Density Function for Subgrid Scale Modeling of Turbulent Combustion |
25-Feb-2009 |
13 pages |
| Authors:
P Givi; M R Sheikhi; PITTSBURGH UNIV PA DEPT OF MECHANICAL ENGINEERING
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| This research was concentrated primarily on developments and applications of the filtered density function (FDF) for subgrid scale (SGS) modeling of turbulent reacting flows. During the past three years, this work addressed: (1) development of the joint velocity-scalar filtered mass density function (VSFMDF), (2) development of the joint frequency-velocity-scalar filtered mass density function (FVS-FMDF), and (3) implementation of the scalar filtered mass density function (SFMDF) and VSFMDF for large eddy ... |
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| Radiation and Dissipation of Internal Waves Generated by Geostrophic Motions Impinging on Small-Scale Topography |
Feb-2009 |
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| Authors:
Maxim Nikurashin; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA DEPT OF PHYSICAL OCEANOGRAPHY
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| Observations and inverse models suggest that small-scale turbulent mixing is enhanced in the Southern Ocean in regions above rough topography. The enhancement extends 1 km above the topography suggesting that mixing is supported by breaking of gravity waves radiated from the ocean bottom. In other regions, gravity wave radiation by bottom topography has been primarily associated with the barotropic tide. In this study, we explore the alternative hypothesis that the ... |
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| Joint Observational Research on Nocturnal Atmospheric Dispersion of Aerosols (JORNADA) |
Feb-2009 |
14 pages |
| Authors:
David Miller; Carmen Nappo; April Hiscox; CONNECTICUT UNIV STORRS
|
| Four major analyses were conducted using the stable boundary layer JORNADA data. First was the analysis of the movement of instantaneous plumes released from a spray aircraft and continuously scanned with the lidar. Techniques for quantifying the concentrations of aerosols in the drifting plumes were established. The effects on plume dynamics and spread of short time (seconds) sub-mesoscale events were quantified. The second was an analysis of wave modified flux ... |
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| Wave Transformation Over Reefs: Evaluation of One-Dimensional Numerical Models |
Jan-2009 |
208 pages |
| Authors:
Zeki Demirbilek; Alejandro Sanchez; Okey G Nwogu; Donald L Ward; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS COASTAL AND HYDRAULICS LAB
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| Three one-dimensional (1D) numerical wave models are evaluated for wave transformation over reefs and estimates of wave setup, runup, and ponding levels in an island setting where the beach is fronted by fringing reef and lagoons. The numerical models are based on different governing equations. BOUSS-1D and RBREAK2 are phase-resolving models that respectively solve the time-dependent Boussinesq and shallow water equations. WAV1D solves the 1D wave-averaged energy conservation equation. Laboratory ... |
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| Atmospheric Laser and Infrared Transmission Model |
Jan-2009 |
45 pages |
| Authors:
David A Lee; Hemm; Robert V Jr; LOGISTICS MANAGEMENT INST (LMI) MCLEAN VA
|
| This report describes the 2008 version of the Atmospheric Laser and Infrared Transmission (ALIRT) model developed by LMI for the Tactical Air Division of the Office of the Secretary of Defense, Program Analysis and Evaluation. ALIRT is a physical optics model that implements a method for calculating the peak and average fluence delivered to an airborne or ground-based target from a laser weapon on an airborne platform, when the beam ... |
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| Lagrangian Observations of Nonlinear Internal Waves and Turbulence Mixing in Luzon Strait and South China Sea and Internal Wave in the Vicinity of the Kuroshio Path |
30-Dec-2008 |
22 pages |
| Authors:
Ren-Chieh Lien; Eric A D'Asaro; WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB
|
| Two related projects were funded sequentially under the same grant number. The first was to conduct an experiment near DongSha Island, using the Lagrangian float, to understand the energy cascade from barotropic tides, internal tides, nonlinear internal waves, to turbulence mixing in the northern South China Sea. Results are reported. The second was to analyze observations of data taken in the vicinity of the Kuroshio path from Luzon Strait to ... |
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| A Computational Framework Based on Variational LES Method for the Multi-Disciplinary Analysis of MAVS With Flapping Wings |
Dec-2008 |
8 pages |
| Authors:
Charbel Farhat; Ajaykumar Rajasekharan; STANFORD UNIV CA DEPT OF MECHANICAL ENGINEERING
|
| In this paper the three level formulation of a variational multi-scale (VMS) large eddy simulation (LES) method for compressible flow computations is extended for applications involving moving/deforming grids. A consistent method to improve the VMS-LES constant dynamically as the flow develops (dynamic VMS-LES) is also extended for dynamic grid applications. Two applications of VMS-LES for the simulation of separated flow over moving NACA-0012 extruded airfoil is then presented. The first ... |
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| 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 ... |
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| Simulation of Flow Past a Sphere using the Fluent Code |
Dec-2008 |
35 pages |
| Authors:
D A Jones; D B Clarke; DEFENSE SCIENCE AND TECHNOLOGY ORGANIZATION VICTORIA (AUSTRALIA) MARITIME PLATFORMS DIV
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| We use the commercial computational fluid dynamics code Fluent to simulate the flow around a sphere in several different flow regimes; steady-state laminar flow at a Reynolds number (Re) of 100, time-dependent laminar flow at Re = 300, and turbulent flow at Re = 10,000 and Re = 1,000,000. These simulations provide a test of the ability of the code to accurately reproduce typical flow structures observed in generic bluff ... |
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| Innovative Techniques to Predict Atmospheric Effects on Sensor Performance |
06-Oct-2008 |
14 pages |
| Authors:
Anthony V Dentamaro; Patricia H Doherty; BOSTON COLL CHESTNUT HILL MA INST FOR SCIENTIFIC RESEARCH
|
| The Boston College Institute for Scientific Research (ISR) is conducting innovative research in areas relating to development and demonstration of new technologies to predict atmospheric effects on sensor performance for acquisition, mission planning and employment of the Air Force's current and next generation electro-optical (EO) systems. Emphasis includes space-, air-, and groundbased EO systems, laser systems including the Airborne Laser (ABL), surveillance and lidar and radar remote sensing technologies. |
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| Revolutionary Physics-Based Design Tools for Quiet Helicopters, Phase I-B Extension |
20-Sep-2008 |
20 pages |
| Authors:
Lakshmi N Sankar; Kenneth S Brentner; GEORGIA TECH RESEARCH CORP ATLANTA
|
| A computational research program was performed at Georgia Institute of Technology, Penn State University, and at Northern Arizona University to develop a set of first-principles based computational modeling tools for analyzing and designing advanced helicopter configurations. The approach involved incorporation of advanced numerical algorithms and turbulence models in OVERFLOW 2, development of advanced comprehensive analyses (DYMORE and RCAS) that are seamlessly coupled to the flow analysis, modeling of rotor noise ... |
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| Analysis of Near-Surface Atmospheric and Oceanic Measurements Obtained During CBLAST-Low |
16-Sep-2008 |
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| Authors:
J H Trowbridge; A J Plueddemann; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| Atmospheric and oceanic measurements obtained during the low-wind component of the Coupled Boundary Layers and Air-Sea Transfer program (CBLAST-Low) were used to elucidate the dynamics of the ocean surface mixed layer. The objective was to quantify and understand the roles of shear- and buoyancy-generated turbulence, Langmuir circulations, and wave breaking in determining the surface-layer structure and dynamics. The project supported the doctoral research of Greg Gerbi, a student in the ... |
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| Closed-Loop Adaptive Optics Control in Strong Atmospheric Turbulence |
01-Sep-2008 |
151 pages |
| Authors:
Todd M Venema; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| A self-referencing interferometer based closed-loop adaptive optics controller is developed which is designed to operate effectively under strong turbulence conditions. The aberrated optical field is modeled stochastically and then estimates of the state of the system are developed using a steady-state, fixed-gain Kalman filter. The phase of the optical field is considered the state of the system which is wrapped in a limited range of (-pi;pi]. This phase is unwrapped ... |
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| 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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| Sound-Wave Coherence in Atmospheric Turbulence With Intrinsic and Global Intermittency |
Aug-2008 |
17 pages |
| Authors:
Vladimir E Ostashev; D K Wilson; George H Goedecke; ENGINEER RESEARCH AND DEVELOPMENT CENTER HANOVER NH COLD REGIONS RESEARCH AND ENGINEERING LAB
|
| The coherence function of sound waves propagating through an intermittently turbulent atmosphere is calculated theoretically. Intermittency mechanisms due to both the turbulent energy cascade (intrinsic intermittency) and spatially uneven production (global intermittency) are modeled using ensembles of quasiwavelets (QWs), which are analogous to turbulent eddies. The intrinsic intermittency is associated with decreasing spatial density (packing fraction) of the QWs with decreasing size. Global intermittency is introduced by allowing the local ... |
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| Investigating Characteristics of Air-Sea Interactions in the Wave and Surface Layers |
02-Jul-2008 |
13 pages |
| Authors:
Jielun Sun; NATIONAL CENTER FOR ATMOSPHERIC RESEARCH BOULDER CO MESOSCALE AND MICROSCALE METEOROLOGY DIV
|
| We were funded to participate in the Coupled Boundary Layers/Air-Sea Transfer under low wind (CBLAST-Low) pilot experiment in 2001 and main experiment in 2003 and analyze the data collected from both field campaigns. Our focuses are air-sea interactions under weak winds by analyzing simultaneous measurements of directional waves and atmospheric turbulence. We found that air-sea interactions strongly depend on whether the oceanic wave energy peak is dominated by swell or ... |
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| Investigation of Small-Caliber Primer Function Using a Multiphase Computational Model |
01-Jul-2008 |
36 pages |
| Authors:
John R Schmidt; Michael J Nusca; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| This report describes further development in the formulation of a primer model that is compatible with the ARL-NGEN3 code and small caliber weapons that takes in account multidimensional, multiphase interior ballistics codes, which employ coupled Eulerian-Lagrangian schemes to explicitly treat both the gas and solid phase. The model is based on the One Dimensional Turbulence modeling approach that has recently emerged as a powerful tool in multiphase simulations. Initial results ... |
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| Preliminary Global Radiation Belt Formation and Prediction Model |
25-Jun-2008 |
28 pages |
| Authors:
Michael J Keskinen; NAVAL RESEARCH LAB WASHINGTON DC PLASMA PHYSICS DIV
|
| A computational model for the time-dependent dynamics of the electron and ion terrestrial radiation belts has been developed. The model solves the fundamental bounce-averaged electron and ion modified Boltzmann Fokker-Planck equations for energy, pitch angle, and L-shell. The code has been applied to broadband whistler turbulence and found to be consistent with empirical models of radiation belt dynamics. |
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| Impacts of Ocean Waves on the Atmospheric Surface Layer: Simulations and Observations |
06 JUN 2008 |
79 pages |
| Authors:
Peter P. Sullivan; James C. McWilliams; W. K. Melville; NATIONAL CENTER FOR ATMOSPHERIC RESEARCH BOULDER CO MESOSCALE AND MICROSCALE METEOROLOGY DIV
|
| This this award investigated surface boundary layers and air-sea interaction with theoretical and numerical research. Our long term scientific objective was to explore the nature of intermittence, coherent structures, and turbulent fluxes and their coupling in the surface layers of the marine atmospheric and oceanic planetary boundary layers (PBL). Efforts were focused on the effects of surface gravity waves on the near-surface dynamics, surface fluxes, and coupling between the atmospheric ... |
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| 2007 Program of Study: Boundary Layers |
Jun-2008 |
|
| Authors:
Claudia Cenedese; John A Whitehead; Joseph Pedlosky; Steven Lentz; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| The topic of the Principal Lectures for the forty-ninth year of the program was Boundary Layers. The subject centers around those problems in which the boundary conditions lead to a large gradient near the boundary. Nine of this year's principal lectures were given by Joe Pedlosky and the tenth was given by Steve Lentz. The fluid mechanics of boundary layers was reviewed, first starting from its classical roots and then ... |
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| Analysis of TODWL PBL Wind Profiles Over Monterey Bay: Towards Ground Truth Winds for WindSAT and Other Remote Sensors |
29 MAY 2008 |
17 pages |
| Authors:
Ralph C. Foster; Robert A. Brown; WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB
|
| Under this project we analyzed data from the TOWDL (Test of Wind Doppler Lidar) data acquired from February-March, 2002 and February, 2003 over and near Monterey Bay, CA to characterize the coherent structures and to compare them to our simple models of PBL roll vortices. This information is crucial for developing Cal/Val strategies and will help advance our fundamental understanding of the planetary boundary layer (PBL). A good model of ... |
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| Optical Phase Unwrapping in the Presence of Branch Points |
12-May-2008 |
15 pages |
| Authors:
Todd M Venema; Jason D Schmidt; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
|
| Strong turbulence causes phase discontinuities known as branch points in an optical field. These discontinuities complicate the phase unwrapping necessary to apply phase corrections onto a deformable mirror in an adaptive optics (AO) system. This paper proposes a non-optimal but effective and implementable phase unwrapping method for optical fields containing branch points. This method first applies a least-squares (LS) unwrapper to the field which isolates and unwraps the LS component ... |
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| Estimation of Combined Wave and Storm Surge Overtopping at Earthen Levees |
MAY 2008 |
17 pages |
| Authors:
Steven A. Hughes; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS COASTAL AND HYDRAULICS LAB
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| This Coastal and Hydraulics Engineering Technical Note (CHETN) provides empirical equations for estimating several parameters of unsteady flow resulting from the combination of steady storm surge overflow and overtopping of irregular waves at a trapezoidal-shaped earthen levee. Equations are given for the average overtopping discharge and the cumulative probability distribution of instantaneous overtopping discharge. On the landward-side slope, empirical equations can be used to estimate the mean flow depth, mean ... |
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| Characterization and Prediction of Clear Air and Optical Stratospheric Turbulence for DoD High Altitude Platforms |
21 MAR 2008 |
52 pages |
| Authors:
Alex Mahalov; Basi Nicolaenko; ARIZONA STATE UNIV TEMPE
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| Stratospheric Clear Air Turbulence (CAT) is a major challenge to the safety, controllability and flight path optimization of the Global Hawk, Predator and other Unmanned Aerial Vehicles (UAVs) and Platforms. Optical Turbulence (OT) layers impact on the polarization and focusing of laser beams in communication systems and the Airborne Laser (ABL). The completed fundamental research project investigated the microscale physics of the upper troposphere/lower stratosphere (UTLS), closely correlating field measurements, ... |
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| Investigation of 2-Dimensional Isotropy of Under-Ice Roughness in the Beaufort Gyre and Implications for Mixed Layer Ocean Turbulence |
MAR 2008 |
73 pages |
| Authors:
Timothy P. McGeehan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| The two-dimensional (2D) spectral properties, including the degree of isotropy, of under-ice roughness in the Beaufort Gyre were investigated. Under-ice roughness plays an important role in turbulent ocean heat, salt, and momentum fluxes that determine the delicate balance between surface forcing and the ocean interior that sustains or reduces the perennial ice cover. Accurate characterization of this roughness is important for numerical modeling and prediction of the Arctic air-ice-ocean system, ... |
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| Analysis of Non-Uniform Gain for Control of a Deformable Mirror in an Adaptive-Optics System |
MAR 2008 |
131 pages |
| Authors:
Kevin P. Vitayaudom; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| The objective of this research was to develop and experimentally verify the use of spatially varying gain maps on the servo-loop controller of a deformable mirror for improvements in the performance of an adaptive optics system and the mitigation of instabilities that can occur over edge actuators of a deformable mirror. The edge subapertures of a Shack-Hartmann wavefront sensor have lower signal-to-noise ratios and are more susceptible to measurement errors ... |
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