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1

A fail safe laser activated switch used as an emergency control link at the Langley Vortex Research Facility  

Microsoft Academic Search

A fail safe light activated switch was used as an emergency control link at the Langley Vortex Research Facility. In this facility aircraft models were towed through a still air test chamber by a gasoline powered vehicle which was launched from one end of a 427-meter track and attained velocities to 31 m\\/sec in the test chamber. A 5 mW

P. C. Kassel Jr.

1978-01-01

2

Riblet\\/LEBU research at NASA Langley  

Microsoft Academic Search

The rising energy costs of the early 1970's made the public aware of the need for new innovative concepts to reduce energy usage. An innovative turbulent boundary layer skin-friction reduction program was begun at NASA Langley in 1972. Two successful drag reduction techniques have resulted from the Langley program, i.e., riblets and LEBUs. The research effort in these two areas

Michael J. Walsh; John B. Anders

1989-01-01

3

ARIES: NASA Langley's Airborne Research Facility  

Microsoft Academic Search

In 1994, the NASA Langley Research Center (LaRC) acquired a B -757 -200 aircraft to replace the aging B - 737 Transport Systems Researc h Vehicle (TSRV). The TSRV was a modified B -737 -100, which served as a trailblazer in the development of glass cockpit technologies and other innovative aeronautical concepts. The mission for the B -757 is to

Michael S. Wusk

4

Nasa Langley Research Center Seventy-Fifth Anniversary Publications, 1992.  

National Technical Information Service (NTIS)

The following are presented: The National Advisory Committee for Aeronautics Charter; Exploring NASA's Roots, the History of NASA Langley Research Center; NASA Langley's National Historic Landmarks; The Mustang Story: Recollections of the XP-51; Testing t...

1992-01-01

5

NASA Langley Research Center's Unmanned Aerial System Surrogate Research Aircraft.  

National Technical Information Service (NTIS)

Research is needed to determine what procedures, aircraft sensors and other systems will be required to allow Unmanned Aerial Systems (UAS) to safely operate with manned aircraft in the National Airspace System (NAS). The NASA Langley Research Center has ...

A. Jessup C. Joyce C. T. Howell F. Jones H. Verstynen J. Mielnik P. Sugden

2010-01-01

6

22. Photocopy of photograph (original in the Langley Research Center ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

22. Photocopy of photograph (original in the Langley Research Center Archives, Hampton, VA LaRC) (L6415) STUFFED SEAGULL ON CARRIAGE OF TOWING TANK - 1932; EXPERIMENT TO DETERMINE AERODYNAMIC QUALITIES OF BIRDS. - NASA Langley Research Center, Seaplane Towing Channel, 108 Andrews Street, Hampton, Hampton, VA

7

Active Control Technology at NASA Langley Research Center.  

National Technical Information Service (NTIS)

NASA Langley has a long history of attacking important technical opportunities from a broad base of supporting disciplines. The research and development at Langley in this subject area range from the test tube to the test flight. The information covered h...

A. R. McGowan R. R. Antcliff

2001-01-01

8

Active Control Technology at NASA Langley Research Center.  

National Technical Information Service (NTIS)

NASA Langley has a long history of attacking important technical opportunities from a broad base of supporting disciplines. The research and development at Langley in this subject area range from the test tube to the test flight. The information covered h...

R. R. Antcliff A. M. R. McGowan

2000-01-01

9

Telerobotic Research at NASA Langley Research Center.  

National Technical Information Service (NTIS)

An overview of Automation Technology Branch facilities and research is presented. Manipulator research includes dual-arm coordination studies, space manipulator dynamics, end-effector controller development, automatic space structure assembly, and the dev...

N. E. Sliwa

1987-01-01

10

Overview of active flow control at NASA Langley Research Center  

Microsoft Academic Search

The paper summarizes active flow control projects currently underway at the NASA Langley Research Center. Technology development is being pursued within a multidisciplinary, cooperative approach, involving the classical disciplines of fluid mechanics, structural mechanics, material science, acoustics, and stability and control theory. Complementing the companion papers in this session, the present paper will focus on projects that have the goal

Latunia G. Pack; Ronald D. Joslin

1998-01-01

11

Scientific and Technical Photography at NASA Langley Research Center.  

National Technical Information Service (NTIS)

As part of my assignment connected with the Scientific and Technical Photography & Lab (STPL) at the NASA Langley Research Center I conducted a series of interviews and observed the day to day operations of the STPL with the ultimate objective of becoming...

A. Davidhazy

1994-01-01

12

Large space antenna communications systems: Integrated Langley Research Center\\/Jet Propulsion Laboratory development activities. 2: Langley Research Center activities  

Microsoft Academic Search

The electromagnetic analysis activities at the Langley Research Center are resulting in efficient and accurate analytical methods for predicting both far- and near-field radiation characteristics of large offset multiple-beam multiple-aperture mesh reflector antennas. The utilization of aperture integration augmented with Geometrical Theory of Diffraction in analyzing the large reflector antenna system is emphasized.

T. G. Cambell; M. C. Bailey; C. R. Cockrell; F. B. Beck

1983-01-01

13

Langley Aerospace Research Student Scholars Project  

NASA Website

[Educators Grades Pre-K-Higher Education & Students Higher Education] [Available: Nationally] Participants spend 10 weeks conducting state-of-the-art research with other students from across the nation. They work with NASA researchers exploring an ...

14

NASA LANGLEY RESEARCH CENTER'S DISTRIBUTED MASS STORAGE SYSTEM  

Microsoft Academic Search

Abstract There is a trend in institutions with high performance,computing,and data management,requirements to explore mass storage systems with peripherals directly attached to a high speed network. The Distributed Mass Storage System (DMSS) Project at the NASA Langley Research Center (LaRC) is building such a system and expects to put it into production use by the end of 1993. This paper

Juliet Z. Pao; D. Creig Humes

15

Electronic photography at NASA Langley Research Center  

NASA Astrophysics Data System (ADS)

The field of photography began a metamorphosis several years ago which promises to fundamentally change how images are captured, transmitted, and output. At this time the metamorphosis is still in the early stages, but already new processes, hardware, and software are allowing many individuals and organizations to explore the entry of imaging into the information revolution. Exploration at this time is prerequisite to leading expertise in the future, and a number of branches at LaRC have ventured into electronic and digital imaging. Their progress until recently has been limited by two factors: the lack of an integrated approach and the lack of an electronic photographic capability. The purpose of the research conducted was to address these two items. In some respects, the lack of electronic photographs has prevented application of an integrated imaging approach. Since everything could not be electronic, the tendency was to work with hard copy. Over the summer, the Photographics Section has set up an Electronic Photography Laboratory. This laboratory now has the capability to scan film images, process the images, and output the images in a variety of forms. Future plans also include electronic capture capability. The current forms of image processing available include sharpening, noise reduction, dust removal, tone correction, color balancing, image editing, cropping, electronic separations, and halftoning. Output choices include customer specified electronic file formats which can be output on magnetic or optical disks or over the network, 4400 line photographic quality prints and transparencies to 8.5 by 11 inches, and 8000 line film negatives and transparencies to 4 by 5 inches. The problem of integrated imaging involves a number of branches at LaRC including Visual Imaging, Research Printing and Publishing, Data Visualization and Animation, Advanced Computing, and various research groups. These units must work together to develop common approaches to image processing and archiving. The ultimate goal is to be able to search for images using an on-line database and image catalog. These images could then be retrieved over the network as needed, along with information on the acquisition and processing prior to storage. For this goal to be realized, a number of standard processing protocols must be developed to allow the classification of images into categories. Standard series of processing algorithms can then be applied to each category (although many of these may be adaptive between images). research effort begun this summer, it may be one of the first organizations to develop an integrated approach to imaging. As such, it could serve as a model for other organizations in government and the private sector.

Holm, Jack M.

1994-12-01

16

Publications on acoustics research at the Langley Research Center during 1980-1986  

NASA Astrophysics Data System (ADS)

This report is a compilation of publications from acoustics research at the Langley Research Center. The reports are listed in chronological order and summarize the written output of the Acoustics Division and its predecessor, The Acoustics and Noise Reduction Division, for the period 1980 through 1986. The information assembled has been extracted from the 1980 through 1986 issues for the Technical Memorandum entitled, Scientific and Technical Information Output of the Langley Research Center for the Calendar Year.

Sutherland, Linda W.

1988-07-01

17

A SURVEY OF RESEARCH PERFORMED AT NASA LANGLEY RESEARCH CENTER'S IMPACT DYNAMICS RESEARCH FACILITY  

Microsoft Academic Search

The Impact Dynamics Research Facility (IDRF) is a 240-ft.-high gantry structure located at NASA Langley Research Center in Hampton, Virginia. The facility was originally built in 1963 as a lunar landing simulator, allowing the Apollo astronauts to practice lunar landings under real- istic conditions. The IDRF was designated a National Historic Landmark in 1985 based on its significant contributions to

Karen E. Jackson; Edwin L. Fasanella

18

Aeroelasticity at the NASA Langley Research Center Recent Progress, New Challenges.  

National Technical Information Service (NTIS)

Recent progress in aeroelasticity, particularly at the NASA Langley Research Center is reviewed to look at the questions answered and questions raised, and to attempt to define appropriate research emphasis needed in the near future and beyond. The paper ...

P. W. Hanson

1985-01-01

19

National Aeronautics and Space Administration Langley Research Center's Design Criteria for Small Unmanned Aerial Vehicle Development.  

National Technical Information Service (NTIS)

National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) has a long, rich tradition of advanced aeronautics research using subscale aircraft. LaRC has developed detailed procedures and guidelines that set forth criteria for the ...

C. M. Cagle M. A. Hutchinson T. L. Jordan V. E. Watkins W. M. Langford

2007-01-01

20

The NASA Langley Research Center's Unmanned Aerial System Surrogate research aircraft  

Microsoft Academic Search

Research is needed to determine what procedures, aircraft sensors and other systems will be required to allow Unmanned Aerial Systems (UAS) to safely operate with manned aircraft in the National Airspace System (NAS). The NASA Langley Research Center has transformed a Cirrus Design SR22 general aviation (GA) aircraft into a UAS Surrogate research aircraft to serve as a platform for

Charles T. Howell; Artie Jessup; Frank Jones; C. Joyce; P. Sugden; H. Verstynen; J. Mielnik

2010-01-01

21

A Summary of DOD-Sponsored Research Performed at NASA Langley's Impact Dynamics Research Facility  

Microsoft Academic Search

The Impact Dynamics Research Facility (IDRF) is a 240-ft.-high gantry structure located at NASA Langley Research Center in Hampton, Virginia. The IDRF was originally built in the early 1960's for use as a Lunar Landing Research Facility. As such, the facility was configured to simulate the reduced gravitational environment of the Moon, allowing the Apollo astro- nauts to practice lunar

Karen E. Jackson; Richard L. Boitnott; Edwin L. Fasanella; Lisa E. Jones; Karen H. Lyle

2006-01-01

22

Validation of Force Limited Vibration Testing at NASA Langley Research Center.  

National Technical Information Service (NTIS)

Vibration tests were performed to develop and validate the forced limited vibration testing capability at the NASA Langley Research Center. The force limited vibration test technique has been utilized at the Jet Propulsion Laboratory and other NASA center...

C. Rice R. D. Buehrle

2003-01-01

23

Coherent Anti-Stokes Raman Spectroscopy (CARS) Measurements in Supersonic Combustors at NASA Langley Research Center.  

National Technical Information Service (NTIS)

This paper describes the recent use of coherent anti-Stokes Raman spectroscopy (CARS) to study supersonic combustion at NASA Langley Research Center. CARS is a nonlinear optical measurement technique used to measure temperature and species mole fractions ...

P. M. Danehy S. B. OByrne S. A. Tedder A. D. Cutler

2005-01-01

24

Scientific and technical photography at NASA Langley Research Center  

NASA Astrophysics Data System (ADS)

As part of my assignment connected with the Scientific and Technical Photography & Lab (STPL) at the NASA Langley Research Center I conducted a series of interviews and observed the day to day operations of the STPL with the ultimate objective of becoming exposed first hand to a scientific and technical photo/imaging department for which my school prepares its graduates. I was also asked to share my observations with the staff in order that these comments and observations might assist the STPL to better serve its customers. Meetings with several individuals responsible for various wind tunnels and with a group that provides photo-optical instrumentation services at the Center gave me an overview of the services provided by the Lab and possible areas for development. In summary form these are some of the observations that resulted from the interviews and daily contact with the STPL facility. (1) The STPL is perceived as a valuable and almost indispensable service group within the organization. This comment was invariably made by everyone. Everyone also seemed to support the idea that the STPL continue to provide its current level of service and quality. (2) The STPL generally is not perceived to be a highly technically oriented group but rather as a provider of high quality photographic illustration and documentation services. In spite of the importance and high marks assigned to the STPL there are several observations that merit consideration and evaluation for possible inclusion into the STPL's scope of expertise and future operating practices. (1) While the care and concern for artistic rendition of subjects is seen as laudable and sometimes valuable, the time that this often requires is seen as interfering with keeping the tunnels operating at maximum productivity. Tunnel managers would like to shorten down-time due to photography, have services available during evening hours and on short notice. It may be of interest to the STPL that tunnel managers are incorporating ever greater imaging capabilities in their facilities. To some extent this could mean a reduced demand for traditional photographic services. (2) The photographic archive is seen as a Center resource. Archiving of images, as well as data, is a matter of concern to the investigators. The early holdings of the Photographic Archives are quickly deteriorating. The relative inaccessibility of the material held in the archives is problematic. (3) In certain cases delivery or preparation of digital image files instead of, or along with, hardcopy is already being perceived by the STPL's customers as desirable. The STPL should make this option available, and the fact that it has, or will have this capability widely known. (4) The STPL needs to continue to provide expert advice and technical imaging support in terms of application information to users of traditional photographic and new electronic imaging systems. Cooperative demo projects might be undertaken to maintain or improve the capabilities of the Lab. (5) STPL personnel do not yet have significant electronic imaging or electronic communication skills and improvements in this is an area could potentially have a positive impact on the Center. (6) High speed photographic or imaging services are often mentioned by the STPL as being of primary importance to their mission but the lab supports very few projects calling for high speed imaging services. Much high speed equipment is in poor state of repair. It is interesting to note that when the operation of lasers, digital imaging or quantitative techniques are requested these are directed to another NASA department. Could joint activities be initiated to solve problems? (7).

Davidhazy, Andrew

1994-12-01

25

NASA LANGLEY RESEARCH CENTER AND THE TIDEWATER INTERAGENCY POLLUTION PREVENTION PROGRAM  

EPA Science Inventory

National Aeronautics and Space Administration (NASA)'s Langley Research Center (LaRC) is an 807-acre research center devoted to aeronautics and space research. aRC has initiated a broad-based pollution prevention program guided by a Pollution Prevention Program Plan and implement...

26

World Wide Web and Technology Transfer at NASA Langley Research Center.  

National Technical Information Service (NTIS)

NASA Langley Research Center (LaRC) began using the World Wide Web (WWW) in the summer of 1993, becoming the first NASA installation to provide a Center-wide home page. This coincided with a reorganization of LaRC to provide a more concentrated focus on t...

D. J. Bianco M. L. Nelson

1994-01-01

27

The langley research center remote computing terminal system: Implementation and first year's operation  

Microsoft Academic Search

In April 1965 a remote computing terminal system was installed at the Langley Research Center in support of open shop programming. This paper describes the system and relates some of the experience gained in using and managing it. Because this system grew out of the needs of the open shop programmers, I will begin by reviewing the development of our

Roger V. Butler

1966-01-01

28

NASA LANGLEY AND NLR RESEARCH OF DISTRIBUTED AIR\\/GROUND TRAFFIC MANAGEMENT  

Microsoft Academic Search

Distributed Air\\/Ground Traffic Management (DAG- TM) is a concept of future air traffic operations that proposes to distribute information, decision-making authority, and responsibility among flight crews, the air traffic service provider, and aeronautical operational control organizations. This paper provides an overview and status of DAG-TM research at NASA Langley Research Center and the National Aerospace Laboratory of The Netherlands. Specific

Mark G. Ballin; Jacco M. Hoekstra; David J. Wing; Gary W. Lohr

29

OAI-PMH Architecture for the NASA Langley Research Center Atmospheric Science Data Center  

Microsoft Academic Search

We present the architectural decisions involved in adding an Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) interface to the NASA Langley Research Center Atmospheric Science Data Center (ASDC). We review four possible implementation strategies and discuss the implications of our choice. The ASDC differs from most OAI-PMH implementations because of its complex data model, large size (1.3 petabytes) of

Churngwei Chu; Walter E. Baskin; Juliet Z. Pao; Michael L. Nelson

2006-01-01

30

Noncoincident validation of Aura MLS observations using the Langley Research Center Lagrangian chemistry and transport model  

Microsoft Academic Search

We evaluate Aura Microwave Limb Sounder version 2.2 measurements of O3, HCl, and H2O with version 19 HALOE observations using a model-assisted, noncoincident intercomparison technique. Air parcels in the Langley Research Center Lagrangian chemistry and transport model (LCTM) are initialized from HALOE observations made during three different 3-week periods in 2004 and early 2005. The LCTM tracks the dynamical and

D. B. Considine; M. Natarajan; T. D. Fairlie; G. S. Lingenfelser; R. B. Pierce; L. Froidevaux; A. Lambert

2008-01-01

31

NASA LANGLEY RESEARCH CENTER'S SIMULATION-TO-FLIGHT CONCEPT ACCOMPLISHED THROUGH THE INTEGRATION LABORATORIES OF THE TRANSPORT RESEARCH FACILITY  

Microsoft Academic Search

The Flight Simulation and Software Branch (FSSB) at NASA Langley Research Center (LaRC) maintains the unique national asset identified as the Transport Research Facility (TRF). The TRF is a group of facilities and integration laboratories utilized to support the LaRC's simulation-to-flight concept. This concept incorporates common software, hardware, and processes for both ground- based flight simulators and LaRC's B-757-200 flying

Debbie Martínez; Paul C. Davidson; P. Sean Kenney; Brian K. Hutchinson

32

Facilities and Research Capabilities High Speed Phenomena Division, David Taylor Model Basin, Langley Field, VA.  

National Technical Information Service (NTIS)

The towing basins used by the High Speed Phenomena Division, David Taylor Model Basin at Langley Field, Virginia, are described. Information on physical characteristics of the basins, towing carriages, towing gear, model-handling equipment, instruments, a...

R. E. Olson W. F. Brownell

1964-01-01

33

A History of Full-Scale Aircraft and Rotorcraft Crash Testing and Simulation at NASA Langley Research Center  

Microsoft Academic Search

This paper summarizes 2-1\\/2 decades of full-scale aircraft and rotorcraft crash testing performed at the Impact Dynamics Research Facility (IDRF) located at NASA Langley Research Center in Hampton, Virginia. The IDRF is a 240-ft.-high steel gantry that was built originally as a lunar landing simulator facility in the early 1960's. It was converted into a full-scale crash test facility for

Karen E. Jackson; Richard L. Boitnott; Edwin L. Fasanella; Lisa E. Jones; Karen H. Lyle

34

Recent Langley helicopter acoustics contributions  

Microsoft Academic Search

The helicopter acoustics program at NASA Langley has included technology for elements of noise control ranging from sources of noise to receivers of noise. The scope of Langley contributions for about the last decade is discussed. Specifically, the resolution of two certification noise quantification issues by subjective acoustics research, the development status of the helicopter system noise prediction program ROTONET

Homer G. Morgan; S. P. Pao; C. A. Powell

1988-01-01

35

Authentic K-12 Science Projects at the NASA Langley Research Center  

NASA Astrophysics Data System (ADS)

The North Central Regional Educational Library (NCREL) has the following to say about authentic learning: "Students are presented with problem-solving activities that incorporate authentic, real-life questions and issues in a format that encourages collaborative effort, dialogue with informed expert sources, and generalization to broader ideas and application" An education team within the Science Directorate at NASA Langley Research Center has been developing education projects with these attributes of authentic learning since 1996. Currently, three projects are underway. The Students' Cloud Observations On-Line (S'COOL) Project, begun in December 1996, involves K-12 students in making ground truth observations of clouds at the time that a NASA earth-observing satellite passes overhead. The students report data through an on-line form, and can later visualize their data along with the corresponding satellite retrieved cloud properties. Students are invited to take an active part in the validation effort for cloud retrievals, analyzing the data and reporting any findings of interest to the Clouds and the Earth's Radiant Energy System (CERES) science team. The team made a connection with the GLOBE program in 2002, helping to define a protocol for student observation of contrails as part of the existing cloud protocol. These protocols involve students in observing parameters of interest for on-going scientific activities; while the GLOBE program provides a forum for dialog between students, educators, and scientists. In 2004, the team launched the Mentoring and inquirY using NASA Data on Atmospheric and earth science for Teachers and Amateurs (MY NASA DATA) project. The goal of this project is to remove the barriers that prevent the K-12 and citizen science communities from making use of the large volume of Earth System Science data that NASA has collected and archived. This allows students to select a problem of real-life importance, and to explore it using high quality data sources. A MY NASA DATA e-mentor network provides opportunities for educators, students, and citizens to engage in dialog about the questions they encounter. This paper will provide an overview of these projects, and some lessons learned for authentic K-12 science efforts.

Chambers, L. H.; Moore, S. W.; Sepulveda, R.

2006-05-01

36

Noise whitening in airborne wind profiling with a pulsed 2-micron coherent doppler lidar at NASA Langley Research Center  

NASA Astrophysics Data System (ADS)

Two different noise whitening methods in airborne wind profiling with a pulsed 2-micron coherent Doppler lidar system at NASA Langley Research Center in Virginia are presented. In order to provide accurate wind parameter estimates from the airborne lidar data acquired during the NASA Genesis and Rapid Intensification Processes (GRIP) campaign in 2010, the adverse effects of background instrument noise must be compensated properly in the early stage of data processing. The results of the two methods are presented using selected GRIP data and compared with the dropsonde data for verification purposes.

Beyon, Jeffrey Y.; Arthur, Grant E.; Koch, Grady J.; Kavaya, Michael J.

2012-05-01

37

Evaluation of the NASA Langley Research Center airborne High Spectral Resolution Lidar extinction measurements during the Megacity Initiative: Local and Global Research Observations (MILAGRO) Campaign  

Microsoft Academic Search

The NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidar (HSRL) was deployed on the NASA LaRC B-200 King Air aircraft and measured profiles of aerosol extinction, backscatter, and depolarization during the Megacity Initiative: Local and Global Research Observations (MILAGRO) Campaign in March 2006. The HSRL collected approximately 55 hours of data over 15 science flights, which were coordinated

R. R. Rogers; R. A. Ferrare; C. A. Hostetler; J. W. Hair; A. L. Cook; D. B. Harper; M. D. Obland; S. P. Burton; A. D. Clarke; P. B. Russell; J. Redemann; J. M. Livingston

2007-01-01

38

Summary of Fluidic Thrust Vectoring Research Conducted at NASA Langley Research Center.  

National Technical Information Service (NTIS)

Interest in low-observable aircraft and in lowering an aircraft's exhaust system weight sparked decades of research for fixed geometry exhaust nozzles. The desire for such integrated exhaust nozzles was the catalyst for new fluidic control techniques; inc...

K. A. Deere

2003-01-01

39

SUMMARY OF FLUIDIC THRUST VECTORING RESEARCH CONDUCTED AT NASA LANGLEY RESEARCH CENTER  

Microsoft Academic Search

Interest in low-observable aircraft and in lowering an aircraft's exhaust system weight sparked decades of research for fixed geometry exhaust nozzles. The desire for such integrated exhaust nozzles was the catalyst for new fluidic control techniques; including throat area control, expansion control, and thrust-vector angle control. This paper summarizes a variety of fluidic thrust vectoring concepts that have been tested

Karen A. Deere

2003-01-01

40

Airborne wind profiling algorithms for the pulsed 2-micron coherent doppler Lidar at NASA Langley Research Center  

NASA Astrophysics Data System (ADS)

Two versions of airborne wind profiling algorithms for the pulsed 2-micron coherent Doppler lidar system at NASA Langley Research Center in Virginia are presented. Each algorithm utilizes different number of line-of-sight (LOS) lidar returns while compensating the adverse effects of different coordinate systems between the aircraft and the Earth. One of the two algorithms APOLO (Airborne Wind Profiling Algorithm for Doppler Wind Lidar) estimates wind products using two LOSs. The other algorithm utilizes five LOSs. The airborne lidar data were acquired during the NASA's Genesis and Rapid Intensification Processes (GRIP) campaign in 2010. The wind profile products from the two algorithms are compared with the dropsonde data to validate their results.

Beyon, Jeffrey Y.; Koch, Grady J.; Kavaya, Michael J.; Ray, Taylor J.

2013-05-01

41

An overview of selected NASP aeroelastic studies at the NASA Langley Research Center  

NASA Astrophysics Data System (ADS)

Following an initial discussion of the NASP flight environment, the results of recent aeroelastic testing of NASP-type highly swept delta-wing models in Langley's Transonic Dynamics Tunnel (TDT) are summarized. Subsonic and transonic flutter characteristics of a variety of these models are described, and several analytical codes used to predict flutter of these models are evaluated. These codes generally provide good, but conservative predictions of subsonic and transonic flutter. Also, test results are presented on a nonlinear transonic phenomena known as aileron buzz which occurred in the wind tunnel on highly swept delta wings with full-span ailerons. An analytical procedure which assesses the effects of hypersonic heating on aeroelastic instabilities (aerothermoelasticity) is also described. This procedure accurately predicted flutter of a heated aluminum wing on which experimental data exists. Results are presented on the application of this method to calculate the flutter characteristics of a fine-element model of a generic NASP configuration. Finally, it is demonstrated analytically that active controls can be employed to improve the aeroelastic stability and ride quality of a generic NASP vehicle flying at hypersonic speeds.

Spain, Charles V.; Soistmann, David L.; Parker, Ellen C.; Gibbons, Michael D.; Gilbert, Michael G.

1990-10-01

42

Chemical climatology of the middle atmosphere simulated by the NASA Langley Research Center Interactive Modeling Project for Atmospheric Chemistry and Transport (IMPACT) model  

Microsoft Academic Search

The stratospheric chemical characteristics of the NASA Langley Research Center Interactive Modeling Project for Atmospheric Chemistry and Transport model are evaluated. We focus on species relevant to stratospheric ozone including the main constituents of the odd nitrogen and inorganic chlorine families. Model-derived chemical climatologies resulting from 20 years of integrations are compared with observations made primarily by the experiments aboard

Jassim A. Al-Saadi; R. Bradley Pierce; Murali Natarajan; T. Duncan Fairlie; William L. Grose

2004-01-01

43

Experimental Investigations of the NASA Common Research Model in the NASA Langley National Transonic Facility and NASA Ames 11-Ft Transonic Wind Tunnel (Invited).  

National Technical Information Service (NTIS)

Experimental aerodynamic investigations of the NASA Common Research Model have been conducted in the NASA Langley National Transonic Facility and the NASA Ames 11-ft wind tunnel. Data have been obtained at chord Reynolds numbers of 5 million for five diff...

A. Dittberner S. M. Rivers

2011-01-01

44

Strategy for Electronic Dissemination of NASA Langley Technical Publications.  

National Technical Information Service (NTIS)

To demonstrate NASA Langley Research Center's relevance and to transfer technology to external customers in a timely and efficient manner, Langley has formed a working group to study and recommend a course of action for the electronic dissemination of tec...

D. G. Roper M. K. Mccaskill S. D. Holland J. L. Walsh M. L. Nelson

1994-01-01

45

Recent advances in active noise and vibration control at NASA Langley Research Center  

NASA Astrophysics Data System (ADS)

Over the past 15 years NASA has investigated the use of active control technology for aircraft interior noise. More recently this work has been supported through the Advanced Subsonic Technology Noise Reduction Program (1994-2001), High Speed Research Program (1994-1999), and through the Quiet Aircraft Technology Program (2000-present). The interior environment is recognized as an important element in flight safety, crew communications and fatigue, as well as passenger comfort. This presentation will overview research in active noise and vibration control relating to interior noise being investigated by NASA. The research to be presented includes: active control of aircraft fuselage sidewall transmission due to turbulent boundary layer or jet noise excitation, active control of interior tones due to propeller excitation of aircraft structures, and adaptive stiffening of structures for noise, vibration, and fatigue control. Work on actuator technology ranging from piezoelectrics, shape memory actuators, and fluidic actuators will be described including applications. Control system technology will be included that is experimentally based, real-time, and adaptive.

Gibbs, Gary P.; Cabell, Randolph H.; Palumbo, Daniel L.; Silcox, Richard J.; Turner, Travis L.

2002-11-01

46

Langley Fitness Center.  

National Technical Information Service (NTIS)

NASA Langley recognizes the importance of healthy employees by committing itself to offering a complete fitness program. The scope of the program focuses on promoting overall health and wellness in an effort to reduce the risks of illness and disease and ...

1993-01-01

47

The Langley Atmospheric Sciences Data Center  

NSDL National Science Digital Library

This collection of radiation budget, cloud, aerosol, and tropospheric data from the Langley Research Center of the National Aeronautics and Space Administration (NASA) contains recent and archival data sets. The data are free, but users must register and log in for access. Downloads from the NASA Water Vapor Project, the Clouds and Earth's Radiant Energy System (CERES) Pathfinder, and the Airborne Multi-angle Imaging SpectroRadiometer (AirMISR) are among the offerings (Java, HTML, FTP). The site also features pages on software, Langley Center activities, news, and a FAQ page.

48

NASA Langley/CNU Distance Learning Programs.  

National Technical Information Service (NTIS)

NASA Langley Research Center and Christopher Newport University (CNU) provide, free to the public, distance learning programs that focus on math, science, and/or technology over a spectrum of education levels from K-adult. The effort started in 1997, and ...

R. Caton T. E. Pinelli

2002-01-01

49

NASA Langley Scientific and Technical Information Output: 1998.  

National Technical Information Service (NTIS)

This document is a compilation of the scientific and technical information that the Langley Research Center has produced during the calendar year 1998. Included are citations for Technical Publications, Conference Publications, Technical Memorandums, Cont...

H. B. C. Machie S. H. C. Stewart

1999-01-01

50

Vortex  

NSDL National Science Digital Library

In this activity, learners create a tornado in a bottle to observe a spiraling, funnel-shaped vortex. A simple connector device allows water to drain from a 2-liter bottle into a second bottle. Learners can observe the whirling water and then repeat the process by inverting the bottle. Use this activity to talk about surface tension, pressure, gravity, friction, angular momentum, and centripetal force.

Exploratorium, The

2012-06-26

51

Research on aircraft trailing vortex detection based on laser's multiplex information echo  

NASA Astrophysics Data System (ADS)

Airfoil trailing vortex is an important reason for the crash, and vortex detection is the basic premise for the civil aeronautics boards to make the flight measures and protect civil aviation's security. So a new method of aircraft trailing vortex detection based on laser's multiplex information echo has been proposed in this paper. According to the classical aerodynamics theories, the formation mechanism of the trailing vortex from the airfoil wingtip has been analyzed, and the vortex model of Boeing 737 in the taking-off phase has also been established on the FLUENT software platform. Combining with the unique morphological structure characteristics of trailing vortex, we have discussed the vortex's possible impact on the frequency, amplitude and phase information of laser echo, and expounded the principle of detecting vortex based on fusing this information variation of laser echo. In order to prove the feasibility of this detecting technique, the field experiment of detecting the vortex of civil Boeing 737 by laser has been carried on. The experimental result has shown that the aircraft vortex could be found really in the laser scanning area, and its diffusion characteristic has been very similar to the previous simulation result. Therefore, this vortex detection means based on laser's multiplex information echo was proved to be practicable relatively in this paper. It will provide the detection and identification of aircraft's trailing vortex a new way, and have massive research value and extensive application prospect as well.

Zhao, Nan-Xiang; Wu, Yong-Hua; Hu, Yi-Hua; Lei, Wu-Hu

2010-05-01

52

Contacting NASA's Langley Research Center  

NASA Website

NASA.gov brings you images, videos and interactive features from the unique perspective of America's space agency. Get the latest updates on NASA missions, subscribe to blogs, RSS feeds and podcasts, watch NASA TV live, or simply read about our ...

53

Model-Based Systems Engineering Pilot Program at NASA Langley.  

National Technical Information Service (NTIS)

NASA Langley Research Center conducted a pilot program to evaluate the benefits of using a Model-Based Systems Engineering (MBSE) approach during the early phase of the Materials International Space Station Experiment-X (MISSE-X) project. The goal of the ...

D. G. Murphy K. G. Vipavetz S. I. Infeld

2012-01-01

54

Research on the dry intrusion accompanying the low vortex precipitation  

Microsoft Academic Search

By employing the 6.7 ?m satellite vapor cloud images and NCEP\\/NCAR 1°×1° reanalysis datasets, the characteristics and mechanism\\u000a of the dry intrusion, as well as its impacts on the low vortex precipitation at the Meiyu front are explored in this paper.\\u000a It is found that the formation, development and maintenance of the low vortex precipitation at the Meiyu front are

XiuPing Yao; GuoXiong Wu; BingKe Zhao; YuBin Yu; GuiMing Yang

2007-01-01

55

Vortex Flow Aerodynamics, volume 1  

SciTech Connect

Vortex modeling techniques and experimental studies of research configurations utilizing vortex flows are discussed. Also discussed are vortex flap investigations using generic and airplane research models and vortex flap theoretical analysis and design studies.

Campbell, J.F.; Osborn, R.F.; Foughner, J.T. Jr.

1986-07-01

56

Langley Deep Field, discovery and interpretation  

Microsoft Academic Search

In May 1978, ARCO Oil and Gas Co. completed the Langley Deep Unit 1 well in Lea County, New Mexico, discovering a deep gas field with production from two horizons. The discovery well produces gas from a northwest-southeast-trending anticline that has a reverse fault at the Ellenburger formation on the northeast flank of the structure. This reverse fault, possibly persistent

G. J. Henderson; E. A. Lake; G. Douglas

1984-01-01

57

Langley Symposium on Aerodynamics, volume 1  

SciTech Connect

The purpose of this work was to present current work and results of the Langley Aeronautics Directorate covering the areas of computational fluid dynamics, viscous flows, airfoil aerodynamics, propulsion integration, test techniques, and low-speed, high-speed, and transonic aerodynamics. The following sessions are included in this volume: theoretical aerodynamics, test techniques, fluid physics, and viscous drag reduction.

Not Available

1986-12-01

58

Review of research on low-profile vortex generators to control boundary-layer separation  

Microsoft Academic Search

An in-depth review of boundary-layer flow-separation control by a passive method using low-profile vortex generators is presented. The generators are defined as those with a device height between 10% and 50% of the boundary-layer thickness. Key results are presented for several research efforts, all of which were performed within the past decade and a half where the majority of these

John C Lin

2002-01-01

59

A review of vortex shedding research and its application  

Microsoft Academic Search

This paper is a review of research work with cylinders in steady currents. The emphasis is mainly on cylinders in water, particularly the research undertaken at BHRA and its general application. Comparisons are made with the work of other authors for both water and air flow and over 60 references are reviewed. The mechanisms of flow-excited oscillations are discussed for

R. King

1977-01-01

60

Electronic photography at NASA Langley Research Center  

Microsoft Academic Search

The field of photography began a metamorphosis several years ago which promises to fundamentally change how images are captured, transmitted, and output. At this time the metamorphosis is still in the early stages, but already new processes, hardware, and software are allowing many individuals and organizations to explore the entry of imaging into the information revolution. Exploration at this time

Jack M. Holm

1994-01-01

61

Efficiency calculation and the vortex characteristics research of centrifugal pump  

NASA Astrophysics Data System (ADS)

Efficiency is an important performance indicator of the centrifugal pump, this paper establish three-dimensional model of one high head centrifugal pump in domestic with CFD software, though changing the operating conditions, statistics the calculation efficiency and energy loss under different operating conditions, compare the impact to efficiency and head calculation with steady and unsteady calculation methods, and research the affect when runner in different locations in the centrifugal pump, given and analysis the reasons of the flow field and pressure distribution of runner in different steps.

Ge, X. F.; Gao, Z. X.; Zheng, Y.; Shen, M. H.

2012-11-01

62

Langley Deep Field, discovery and interpretation  

SciTech Connect

In May 1978, ARCO Oil and Gas Co. completed the Langley Deep Unit 1 well in Lea County, New Mexico, discovering a deep gas field with production from two horizons. The discovery well produces gas from a northwest-southeast-trending anticline that has a reverse fault at the Ellenburger formation on the northeast flank of the structure. This reverse fault, possibly persistent to the base of the Wolfcamp Formation, generated an anticlinal feature in the upthrown block at the Devonian level. The fault itself is the trap at the Ellenburger formation. Since the discovery of the Langley Deep field in 1978, a new geologic interpretation has been proposed for the eastern rim of the Delaware basin. A major conclusion, based on seismic control, the well control from this field, and on subsurface control throughout southern Lea County, New Mexico, is that a strike-slip fault was activated during the Late Pennsylvanian and Early Permian and caused deformation resulting in the formation of the Langley Deep structure.

Henderson, G.J.; Lake, E.A.; Douglas, G.

1984-01-01

63

Investigation of Liner Characteristics in the NASA Langley Curved Duct Test Rig.  

National Technical Information Service (NTIS)

The Curved Duct Test Rig (CDTR), which is designed to investigate propagation of sound in a duct with flow, has been developed at NASA Langley Research Center. The duct incorporates an adaptive control system to generate a tone in the duct at a specific f...

C. H. Gerhold M. C. Brown M. G. Jones W. R. Watson

2007-01-01

64

Analysis of Dynamic Data from Supersonic Retropropulsion Experiments in NASA Langley's Unitary Plan Wind Tunnel.  

National Technical Information Service (NTIS)

Recent experimental supersonic retropropulsion tests were conducted at the NASA Langley Research Center Unitary Plan Wind Tunnel Test Section 2 for a range of Mach numbers from 2.4 to 4.6. A 5-inch 70-degree sphere-cone forebody model with a 10-inch cylin...

J. R. Codoni S. A. Berry

2012-01-01

65

Supersonic Retropropulsion Experimental Results from the NASA Langley Unitary Plan Wind Tunnel.  

National Technical Information Service (NTIS)

A new supersonic retropropulsion experimental effort, intended to provide code validation data, was recently completed in the Langley Research Center Unitary Plan Wind Tunnel Test Section 2 over the Mach number range from 2.4 to 4.6. The experimental mode...

C. J. Player K. T. Edquist M. N. Rhode S. A. Berry

2011-01-01

66

SNC Dream Chaser Testing Begins at NASA's Dryden, Langley  

NASA Website

SNC's Dream Chaser test flight craft arrived at NASA Dryden to begin tests of its flight and runway landing systems while NASA astronauts will be at Langley to fly simulations of a Dream Chaser approach and landing.

67

NASA-Langley web-based operational real-time cloud retrieval products from geostationary satellites  

NASA Astrophysics Data System (ADS)

At NASA Langley Research Center (LaRC), radiances from multiple satellites are analyzed in near real-time to produce cloud products over many regions on the globe. These data are valuable for many applications such as diagnosing aircraft icing conditions and model validation and assimilation. This paper presents an overview of the multiple products available, summarizes the content of the online database, and details web-based satellite browsers and tools to access satellite imagery and products.

Palikonda, Rabindra; Minnis, P.; Spangenberg, D. A.; Khaiyer, M. M.; Nordeen, M. L.; Ayers, J. K.; Nguyen, L.; Yi, Y.; Chan, P. K.; Trepte, Q. Z.; Chang, F.-L.; Smith, W. L., Jr.

2006-12-01

68

Laser velocimetry and blade pressure measurements of a blade-vortex interaction  

NASA Astrophysics Data System (ADS)

An investigation of the flowfield chracteristics around a rotor blade during a blade-vortex interaction (BVI) was conducted at the NASA Langley Research Center by the Army's Aeroperformance Division and the Boeing Defense and Space Group, Helicopter Division, during a wind-tunnel test in the 14 by 22-foot Subsonic Tunnel. A two-component laser velocimeter was used to measure the blade pressure during a BVI. This paper presents velocity measurements that indicate the presence of a vortex in the streamlines and vectors of the induced velocity, when studied in conjunction with the blade surface pressures, indicate how the flowfield is behaving during a BVI. The following conclusions can be made from this investigation: (1) The streamlines and vectors of the induced velocity, when studied in conjunction with the blade surface pressures, indiacte how the flowfield is behaving during a BVI. The blade approaches and intersects a vortex, and the vortex slides beneath the blade. (2) The data provide detailed flowfield information for validating computational predictions of BVI and also for evaluating and improving current wake models. Among the options investigated, only the free-wake calculation by TECH-01 indicated any BVI activity in the first quadrant.

Gorton, Susan Althoff; Poling, David R.; Dadone, Leo

1995-04-01

69

Representation and transformation of Langley's map of the infrared solar spectrum  

NASA Astrophysics Data System (ADS)

In 1900, after 18 years of research, the American astrophysicist Samuel Pierpont Langley published the final report of his investigations in the infrared region of the solar spectrum. (See Samuel P. Langley: Annals of the Astrophysical Observatory of the Smithsonian Institution, Vol. 1, Washington: Goverment Printing Office, 1900.) In this report one finds three different types of maps of the infrared region, extending from 1.1 mu-m to 5.3 mu-m and showing the positions of 750 absorption lines: a bolograph, a line spectrum and a normal spectrum. (The bolograph, the line spectrum and the normal spectrum are accessible as pl. XX and XXIV at http://adsbit.harvard.edu/books/saoann/.) Looking at these three distinct forms of representation raises the questions: Why did Langley decide to use three representations for the visualization of his results? How are these distinct representations connected? An analysis of the first question will provide further insight into the ``connection between instruments, practices, and the visual'', into the recording, evaluation and processing of the data and, furthermore, into the historical and disciplinary contexts. The prevailing trend toward the automation of measuring and registration processes, and the associated claim of `mechanical objectivity', together with standards concerning precision and completeness set by Henry Rowland's photographic measurements in the visible part of the spectrum, turn out to be the strongest elements in the development of the different forms of representation and their respective transformations.

Loettgers, Andrea

70

Formation Mechanism and Characteristics Research of Ball Lightning Based on Vortex Model  

NASA Astrophysics Data System (ADS)

The strange characteristics of ball lightning are considered as a question hard to explain. In order to solve the problem, in this paper a complete model of plasma vortex is presented for the ball lightning. By ideal MHD equations, through imposing disturbance to plasma column, the possibility of sausage and kink instability of the lightning channel is analyzed from the perspective the minimum potential energy. The conclusion is that the kink instability (m = 1) is most prone to occur. And when instability occurs, because of the difference of the magnetic field in the twisted area, the magnetic pressure makes the trend further and therefore forming the plasma vortex that may eventually turn into ball lightning if the energy of the vortex is large enough. The existence of the vortex makes ball lightning have a short period of time stability. By the proposed model, the ball lightning features that are hard to understand in the past are explained. In this paper, the reason for bead lightning is also explained from the perspective of the sausage instability.

Li, Zi-Cheng; Yang, Guo-Hua

2011-05-01

71

Composite Fuselage Shell Structures Research at NASA Langley Research Center.  

National Technical Information Service (NTIS)

Fuselage structures for transport aircraft represent a significant percentage of both the weight and the cost of these aircraft primary structures. Composite materials offer the potential for reducing both the weight and the cost of transport fuselage str...

J. H. Starnes M. J. Shuart

1992-01-01

72

Capacity analysis of the NASA Langley airport management module  

Microsoft Academic Search

This paper provides a detailed discussion of the analysis and testing performed on the NASA Langley Airport Management Module (AMM) by Seagull Technology while under contract with the South East SATSLAB. This paper presents background into the Small Aircraft Transportation System (SATS) concept and presents a brief summary of the AMM functionality. Next, the experiment design is discussed along with

M. Peters

2005-01-01

73

Overview of Dynamic Test Techniques for Flight Dynamics Research at NASA LaRC (Invited).  

National Technical Information Service (NTIS)

An overview of dynamic test techniques used at NASA Langley Research Center on scale models to obtain a comprehensive flight dynamics characterization of aerospace vehicles is presented. Dynamic test techniques have been used at Langley Research Center si...

C. M. Fremaux D. B. Owens D. D. Vicroy E. H. Heim J. M. Brandon M. A. Croom

2006-01-01

74

Vortex methods.  

National Technical Information Service (NTIS)

Vortex methods originated from the observation that in incompressible inviscid flow vorticity (or, more accurately, circulation) is a conserved quantity, as can be readily deduced from the absence of tangential stresses. Thus, if the vorticity is known at...

A. J. Chorin

1993-01-01

75

Vortex Bursting.  

National Technical Information Service (NTIS)

Vortex bursting is studied by means of visualization. The physical behavior of the phenomenon is emphasized, and its similarity with boundary layer separation or wake bursting becomes apparent. The essential influence of an increasing pressure gradient on...

H. Werle

1984-01-01

76

ADVANCED COMPOSITES TECHNOLOGY CASE STUDY AT NASA LANGLEY RESEARCH CENTER  

EPA Science Inventory

Under the Chesapeake Bay Agreement, NASA-LaRC is a member of the Tidewater Interagency Pollution Prevention Program (TIPPP). t NASA-LaRC, a technique for producing advanced composite materials without the use of solvents has been developed. his assessment was focused on the produ...

77

Airbreathing Hypersonic Systems Focus at NASA Langley Research Center.  

National Technical Information Service (NTIS)

This paper presents the status of the airbreathing hypersonic airplane and space-access vehicle design matrix, reflects on the synergies and issues, and indicates the thrust of the effort to resolve the design matrix and to focus/advance systems technolog...

J. L. Hunt V. L. Rausch

1998-01-01

78

NASA. Langley Research Center Dry Powder Towpreg System.  

National Technical Information Service (NTIS)

Dry powder polymer impregnated carbon fiber tows were produced for preform weaving and composite materials molding applications. In the process, fluidized powder is deposited on spread tow bundles and melted on the fibers by radiant heating to adhere the ...

R. M. Baucom J. M. Marchello

1990-01-01

79

Vortex methods and vortex statistics.  

National Technical Information Service (NTIS)

Vortex methods originated from the observation that in incompressible, inviscid, isentropic flow vorticity (or, more accurately, circulation) is a conserved quantity, as can be readily deduced from the absence of tangential stresses. Thus if the vorticity...

A. J. Chorin

1993-01-01

80

Vortex methods and vortex statistics  

SciTech Connect

Vortex methods originated from the observation that in incompressible, inviscid, isentropic flow vorticity (or, more accurately, circulation) is a conserved quantity, as can be readily deduced from the absence of tangential stresses. Thus if the vorticity is known at time t = 0, one can deduce the flow at a later time by simply following it around. In this narrow context, a vortex method is a numerical method that makes use of this observation. Even more generally, the analysis of vortex methods leads, to problems that are closely related to problems in quantum physics and field theory, as well as in harmonic analysis. A broad enough definition of vortex methods ends up by encompassing much of science. Even the purely computational aspects of vortex methods encompass a range of ideas for which vorticity may not be the best unifying theme. The author restricts himself in these lectures to a special class of numerical vortex methods, those that are based on a Lagrangian transport of vorticity in hydrodynamics by smoothed particles (``blobs``) and those whose understanding contributes to the understanding of blob methods. Vortex methods for inviscid flow lead to systems of ordinary differential equations that can be readily clothed in Hamiltonian form, both in three and two space dimensions, and they can preserve exactly a number of invariants of the Euler equations, including topological invariants. Their viscous versions resemble Langevin equations. As a result, they provide a very useful cartoon of statistical hydrodynamics, i.e., of turbulence, one that can to some extent be analyzed analytically and more importantly, explored numerically, with important implications also for superfluids, superconductors, and even polymers. In the authors view, vortex ``blob`` methods provide the most promising path to the understanding of these phenomena.

Chorin, A.J.

1993-05-01

81

The Langley-Newcomb brouhaha over the flying machine  

NASA Astrophysics Data System (ADS)

One century after the Wright brothers proved it was possible to build a piloted heavier-than-air “flying machine,” several airlines will soon, perhaps as early as October 2005, begin to operate the largest passenger aircraft ever built, the Airbus A380. The A380 is nearly half again as large, in terms of passenger floor space, as the Boeing 747-400. It can be configured to hold as many as 840 passengers, and it has a takeoff weight of 550,000 kg, a maximum range of 15,000 km, and a cruising speed of Mach 0.85.The remarkable advances in aeronautics realized during the past century make it difficult to understand how anyone, let alone Simon Newcomb, one of the most prominent U.S. scientists at the turn of the twentieth century, could have opposed efforts by Samuel Pierpont Langley to build a piloted winged aircraft for the military. Newcomb argued that Langley was doomed to failure because the technology required to build such an aircraft was not then available, and he bemoaned the “waste” of scarce government funds toward the effort.

Carter, W. E.; Carter, M. S.

82

Vortex Characteristic and Flow Discharge In Vortex Settling Chamber  

NASA Astrophysics Data System (ADS)

In water treatment field, separation of sediment from raw water is one of the most important problems we must face today, especially separation of fine sediment particle from muddy water - water with very high sediment concentration in natural resources such as river, reservoir, etc. There are so many different methods to solve this problem including tunnel type, vortex tubes, rectangular settling basins and the vortex type settling chamber. Among them the vortex settling chamber has recently studied so much because of its advantage. The vortex settling chamber is a device which is used to extract sediment from the diverted water by the vortex flow and centrifugal force in chamber. It can be said that vortex settling basin is an economical, efficient, and water-conserving choice compared with the other available devices especially for excluding fine suspended sediment particles. This research presents the new model of vortex settling chamber which will be focused on the separation of fine sediment from muddy water. This paper firstly presents the model in detail and some experimental cases which are carried out in this study. The relationship between flow discharge and water level will be considered and then some respective results will be presented and discussed. Finally, some conclusions are made about vortex characteristic in chamber as well as its effect on flow discharge.

Nguyen, Q.; Jan, C.

2008-12-01

83

Verification of Vortex Workflows  

Microsoft Academic Search

Vortex is a workflow language to support decision making activities. It centers around gathering and computing attributes of in- put objects. The semantics of Vortex is declarative, and the dependency graphs of Vortex programs are acyclic. This paper discusses the appli- cation of symbolic model checking techniques to verification of Vortex programs. As a case study we used a Vortex

Xiang Fu; Tevfik Bultan; Richard Hull; Jianwen Su

2001-01-01

84

Design and Preliminary Tests of a Blade Tip Air Mass Injection System for Vortex Modification and Possible Noise Reduction on a Full-Scale Helicopter Rotor.  

National Technical Information Service (NTIS)

Full-scale tests were conducted on the Langley helicopter rotor test facility as part of a study to evaluate the effectiveness of a turbulent blade tip air mass injection system in alleviating the impulsive noise (blade slap) caused by blade-vortex intera...

R. J. Pegg R. N. Hosier J. C. Balcerak H. K. Johnson

1975-01-01

85

Wind-Tunnel Free-Flight Investigation of a 0.15-Scale Model of the F-106B Airplane with Vortex Flaps.  

National Technical Information Service (NTIS)

An investigation to determine the effects of vortex flaps on the flight dynamic characteristics of the F-106B in the area of low-speed, high-angle-of-attack flight was undertaken on a 0.15-scale model of the airplane in the Langley 30- by 60-Foot Tunnel. ...

L. P. Yip

1987-01-01

86

Reduction of blade-vortex interaction noise using higher harmonic pitch control  

Microsoft Academic Search

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of

Thomas F. Brooks; Earl R. Booth Jr.; J. Ralph Jolly Jr.; William T. Yeager Jr.; Matthew L. Wilbur

1989-01-01

87

Reduction of blade-vortex interaction noise through higher harmonic pitch control  

Microsoft Academic Search

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of

Thomas F. Brooks; Earl R. Booth Jr.; J. Ralph Jolly Jr.; William T. Yeager Jr.; Matthew L. Wilbur

1990-01-01

88

Brownian vortexes  

NASA Astrophysics Data System (ADS)

Mechanical equilibrium at zero temperature does not necessarily imply thermodynamic equilibrium at finite temperature for a particle confined by a static but nonconservative force field. Instead, the diffusing particle can enter into a steady state characterized by toroidal circulation in the probability flux, which we call a Brownian vortex. The circulatory bias in the particle’s thermally driven trajectory is not simply a deterministic response to the solenoidal component of the force but rather reflects interplay between advection and diffusion in which thermal fluctuations extract work from the nonconservative force field. As an example of this previously unrecognized class of stochastic heat engines, we consider a colloidal sphere diffusing in a conventional optical tweezer. We demonstrate both theoretically and experimentally that nonconservative optical forces bias the particle’s fluctuations into toroidal vortexes whose circulation can reverse direction with temperature or laser power.

Sun, Bo; Lin, Jiayi; Darby, Ellis; Grosberg, Alexander Y.; Grier, David G.

2009-07-01

89

Experimental Performance of an Internal Resistance Heater for Langley 6-Inch Expansion Tube Driver.  

National Technical Information Service (NTIS)

An experimental investigation of the heating characteristics of an internal resistance heating element was conducted in the driver of the Langley 6-inch expansion tube to obtain actual operating conditions, to compare these results to theory, and to deter...

T. R. Creel

1972-01-01

90

The vortex flowmeter: various methods of investigating phenomena  

Microsoft Academic Search

This paper is devoted to the Karman vortex shedding flowmeter—its physical fundamentals, research, design, optimization and applications. The flowmeter is currently in a stage of rapid development. Many valuable discoveries concerning the applied Karman vortex street phenomenon have been made. In this paper, various aspects of the problems concerning the vortex meter are described. Fundamental problems and their solutions are

Grzegorz L Pankanin

2005-01-01

91

NASA Langley Atmospheric Science Data Center (ASDC) Experience with Aircraft Data  

NASA Astrophysics Data System (ADS)

Over the past decade the NASA Langley ASDC has archived and distributed a variety of aircraft mission data sets. These datasets posed unique challenges for archiving from the rigidity of the archiving system and formats to the lack of metadata. The ASDC developed a state-of-the-art data archive and distribution system to serve the atmospheric sciences data provider and researcher communities. The system, called Archive - Next Generation (ANGe), is designed with a distributed, multi-tier, serviced-based, message oriented architecture enabling new methods for searching, accessing, and customizing data. The ANGe system provides the ease and flexibility to ingest and archive aircraft data through an ad hoc workflow or to develop a new workflow to suit the providers needs. The ASDC will describe the challenges encountered in preparing aircraft data for archiving and distribution. The ASDC is currently providing guidance to the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) Earth Venture-1 project on developing collection, granule, and browse metadata as well as supporting the ADAM (Airborne Data For Assessing Models) site.

Perez, J.; Sorlie, S.; Parker, L.; Mason, K. L.; Rinsland, P.; Kusterer, J.

2011-12-01

92

PREFACE: Special section on vortex rings Special section on vortex rings  

NASA Astrophysics Data System (ADS)

This special section of Fluid Dynamics Research includes five articles on vortex rings in both classical and quantum fluids. The leading scientists of the field describe the trends in and the state-of-the-art development of experiments, theories and numerical simulations of vortex rings. The year 2008 was the 150th anniversary of 'vortex motion' since Hermann von Helmholtz opened up this field. In 1858, Helmholtz published a paper in Crelle's Journal which put forward the concept of 'vorticity' and made the first analysis of vortex motion. Fluid mechanics before that was limited to irrotational motion. In the absence of vorticity, the motion of an incompressible homogeneous fluid is virtually equivalent to a rigid-body motion in the sense that the fluid motion is determined once the boundary configuration is specified. Helmholtz proved, among other things, that, without viscosity, a vortex line is frozen into the fluid. This Helmholtz's law immediately implies the preservation of knots and links of vortex lines and its implication is enormous. One of the major trends of fluid mechanics since the latter half of the 20th century is to clarify the topological meaning of Helmholtz's law and to exploit it to develop theoretical and numerical methods to find the solutions of the Euler equations and to develop experimental techniques to gain an insight into fluid motion. Vortex rings are prominent coherent structures in a variety of fluid motions from the microscopic scale, through human and mesoscale to astrophysical scales, and have attracted people's interest. The late professor Philip G Saffman (1981) emphasized the significance of studies on vortex rings. One particular motion exemplifies the whole range of problems of vortex motion and is also a commonly known phenomenon, namely the vortex ring or smoke ring. Vortex rings are easily produced by dropping drops of one liquid into another, or by puffing fluid out of a hole, or by exhaling smoke if one has the skill. Their formation is a problem of vortex sheet dynamics, the steady state is a problem of existence, their duration is a problem of stability, and if there are several we have the problem of vortex interactions. Helmholtz himself, in the same paper (1858), devoted a few pages to an analysis of the motion of a vortex ring, and made substantial contributions. Since then, theoretical, experimental and numerical treatments of vortex rings have been developing continuously, yet we encounter mysteries and novel phenomena, with which vortex rings find new applications in, say, bio-fluid mechanics. Recently vortex rings have enlarged their scope beyond classical fluids to encompass super-fluids and Bose-Einstein condensates. On the occasion of the 150th anniversary of Helmholtz's theory on a vortex ring, it is worthwhile to bring together, in one issue, the latest understandings of and open problems in vortex rings from various aspects. The topics in this issue include development of theories and experiments for motion of vortex rings and their interaction with other vortex rings, flows and boundaries, with application to vortex-ring manipulation for flow control, original experiments on collision of vortex rings with a porous boundary, a novel numerical technique to simulate three-dimensional motion of vortex rings and new theories of dynamics of quantum vortex rings governed by nonlinear Schrödinger equations. I hope that this special section gives a sketch, in some proportion, of the current frontier of the field and provides a means to tackle future problems. References Saffman P G 1981 Dynamics of vorticity J. Fluid Mech. 106 49-58 von Helmholtz H 1858 Über Integrale der hydrodynamischen Gleichungen welche den Wirbelbewegungen entsprechen J. Reine Angew. Math. 55 25-55 (Engl. transl.: Tait P G 1867 On the integrals of the hydrodynamical equations which express vortex-motion Phil. Mag. 33 (4) 485-512)

Fukumoto, Yasuhide

2009-10-01

93

Wingtip Vortex Propeller.  

National Technical Information Service (NTIS)

A device which increases the energy efficiency and aerodynamic properties of aircraft was developed. A wingtip pusher propeller is positioned aft of the wingtip to rotate in the crossflow of the wingtip vortex. The propeller rotates against the vortex swi...

J. C. Patterson

1984-01-01

94

The Swirling Vortex  

Microsoft Academic Search

We consider an infinite vortex line in a viscous fluid interacting with a plane boundary surface at right angles to the line. If the boundary surface were absent, the vortex would impart to the fluid a circular motion about the vortex line with speed inversely proportional to the distance to the line. The presence of the boundary surface, however, leads

J. Serrin

1972-01-01

95

Research abd Technology Highlights 1995.  

National Technical Information Service (NTIS)

The mission of the NASA Langley Research Center is to increase the knowledge and capability of the United States in a full range of aeronautics disciplines and in selected space disciplines. This mission is accomplished by performing innovative research r...

1996-01-01

96

Evidence of vortex jamming in Abrikosov vortex flux flow regime  

NASA Astrophysics Data System (ADS)

We report on dynamics of nonlocal Abrikosov vortex flow in mesoscopic superconducting Nb channels. Magnetic field dependence of the nonlocal voltage induced by the flux flow shows that vortices form ordered vortex chains. Voltage asymmetry (rectification) with respect to the direction of vortex flow is evidence that vortex jamming strongly moderates vortex dynamics in mesoscopic geometries. The findings can be applied to superconducting devices exploiting vortex dynamics and vortex manipulation, including superconducting wires with engineered pinning centers.

Karapetrov, G.; Yefremenko, V.; Mihajlovi?, G.; Pearson, J. E.; Iavarone, M.; Novosad, V.; Bader, S. D.

2012-08-01

97

Evidence of Vortex Jamming in Abrikosov Vortex Flux Flow Regime  

NASA Astrophysics Data System (ADS)

We report on dynamics of non-local Abrikosov vortex flow in mesoscopic superconducting Nb channels. Magnetic field dependence of the non-local voltage induced by the flux flow shows that vortices form ordered vortex chains. Voltage asymmetry (rectification) with respect to the direction of vortex flow is evidence that vortex jamming strongly moderates vortex dynamics in mesoscopic geometries. The findings can be applied to superconducting devices exploiting vortex dynamics and vortex manipulation, including superconducting wires with engineered pinning centers.

Karapetrov, Goran; Yefremenko, V.; Mihajlovic, G.; Pearson, J. E.; Iavarone, M.; Novosad, V.; Bader, S. D.

2012-02-01

98

Measurements of Flow Turbulence in the NASA Langley Transonic Dynamics Tunnel.  

National Technical Information Service (NTIS)

An assessment of the flow turbulence in the NASA Langley Transonic Dynamics Tunnel (TDT) was conducted during calibration activities following the facility conversion from a Freon-12 heavy-gas test medium to an R134a heavy-gas test medium. Total pressure,...

C. D. Wiesman R. K. Sleeper

2005-01-01

99

Test Capabilities and Recent Experiences in the NASA Langley 8-Foot High Temperature Tunnel.  

National Technical Information Service (NTIS)

The NASA Langley 8-Foot High Temperature Tunnel is a combustion-heated hypersonic blowdown-to-atmosphere wind tunnel that provides flight enthalpy simulation for Mach numbers of 4, 5, and 7 through an altitude range from 50,000 to 120,000 feet. The open-....

J. S. Hodge S. F. Harvin

2000-01-01

100

Present Status of the MIT/NASA Langley 6-Inch MSBS.  

National Technical Information Service (NTIS)

The latest improvements are described which were made to the MIT/NASA Langley 6 Inch Magnetic Suspension and Balance System and its operational capabilities. Since its relocation from MIT in 1984, the system has suffered from reliability problems with ori...

T. Schott T. Jordan T. Daniels C. Alcorn

1992-01-01

101

The effect of uranium mine tailings on radionuclide concentrations in Langley Bay, Saskatchewan, Canada  

Microsoft Academic Search

From 1955 to 1964 the Gunnar Uranium Mine (Canada) produced approximately 8×103 tonnes of uranium oxide and about 5×106 tonnes of waste rock tailings. Large quantities of fine tailings material washed into Langley Bay, a shallow bay opening onto Lake Athabasca. The limnoiogical characteristics of this bay make it an ideal site to study the movement and impact of some

D. T. Waite; S. R. Joshi; H. Sommerstad

1988-01-01

102

33 CFR 334.275 - North and Southwest Branch, Back River, Hampton, U.S. Air Force Base, Langley, Va.; restricted area.  

Code of Federal Regulations, 2010 CFR

...Back River, Hampton, U.S. Air Force Base, Langley, Va.; restricted area...Back River, Hampton, U.S. Air Force Base, Langley, Va.; restricted area...thence along the shore of Langley Air Force Base, 35 yards off the ordinary mean...

2009-07-01

103

33 CFR 334.275 - North and Southwest Branch, Back River, Hampton, U.S. Air Force Base, Langley, Va.; restricted area.  

Code of Federal Regulations, 2010 CFR

...Back River, Hampton, U.S. Air Force Base, Langley, Va.; restricted area...Back River, Hampton, U.S. Air Force Base, Langley, Va.; restricted area...thence along the shore of Langley Air Force Base, 35 yards off the ordinary mean...

2010-07-01

104

From vortex layers to vortex sheets  

NASA Astrophysics Data System (ADS)

This paper shows that the solution of the Birkhoff-Rott equation for the vortex sheet can be approximated, for short times, by the solutions of the Euler equation for a thin vortex layer of vorticity, when its thickness vanishes and its vorticity intensity diverges suitably. The result is obtained in an analytical setup, and an example seems to indicate that this is indeed necessary.

Benedetto, D.; Pulvirenti, M.

1992-08-01

105

Aeronautics Academy at NASA's Ames, Dryden, Glenn and Langley Centers  

NASA Website

[Students Higher Education] [Available: Nationally] This U.S. college student opportunity offers intense training in aeronautics that includes research, leadership development, and broad exposure to the nation's aeronautics enterprise.

106

Spin effects in electron vortex states  

NASA Astrophysics Data System (ADS)

The recent experimental realization of electron vortex beams opens up a wide research domain previously unexplored. The present paper explores the relativistic properties of these electron vortex beams, and quantifies deviations from the scalar wave theory. It is common in electron optics to use the Schrödinger equation neglecting spin. The present paper investigates the role of spin and the total angular momentum Jz and how it pertains to the vortex states. As an application, we also investigate if it is possible to use holographic reconstruction to create novel total angular momentum eigenstates in a transmission electron microscope. It is demonstrated that relativistic spin coupling effects disappear in the paraxial limit, and spin effects in holographically created electron vortex beams can only be exploited by using specialized magnetic apertures.

Van Boxem, Ruben; Verbeeck, Jo; Partoens, Bart

2013-05-01

107

Earth Science Data and Applications for K-16 Education from the NASA Langley Atmospheric Science Data Center  

NASA Astrophysics Data System (ADS)

NASA's Science Mission Directorate aims to stimulate public interest in Earth system science and to encourage young scholars to consider careers in science, technology, engineering and mathematics. NASA's Atmospheric Science Data Center (ASDC) at Langley Research Center houses over 700 data sets related to Earth's radiation budget, clouds, aerosols and tropospheric chemistry that are being produced to increase academic understanding of the natural and anthropogenic perturbations that influence global climate change. However, barriers still exist in the use of these actual satellite observations by educators in the classroom to supplement the educational process. Thus, NASA is sponsoring the "Mentoring and inquirY using NASA Data on Atmospheric and earth science for Teachers and Amateurs" (MY NASA DATA) project to systematically support educational activities by reducing the ASDC data holdings to `microsets' that can be easily accessible and explored by the K-16 educators and students. The microsets are available via Web site (http://mynasadata.larc.nasa.gov) with associated lesson plans, computer tools, data information pages, and a science glossary. A MY NASA DATA Live Access Server (LAS) has been populated with ASDC data such that users can create custom microsets online for desired time series, parameters and geographical regions. The LAS interface is suitable for novice to advanced users, teachers or students. The microsets may be visual representations of data or text output for spreadsheet analysis. Currently, over 148 parameters from the Clouds and the Earth's Radiant Energy System (CERES), Multi-angle Imaging SpectroRadiometer (MISR), Surface Radiation Budget (SRB), Tropospheric Ozone Residual (TOR) and the International Satellite Cloud Climatology Project (ISCCP) are available and provide important information on clouds, fluxes and cycles in the Earth system. Additionally, a MY NASA DATA OPeNDAP server has been established to facilitate file transfer of ASDC data for other client applications such as MATLAB, GrADS, and IDV. OPeNDAP has become a very popular alternative for data access especially at the university research level with over 375 OPeNDAP-accessible data sets registered nationally. Teacher workshops will be held each summer for five years to help teachers learn about incorporating NASA microsets in their curriculum. The next MY NASA DATA teacher workshop will be held at Langley Research Center July 25-29, 2005. Workshop participants will create microsets and lesson plans that they believe will help their students understand Earth system concepts. These lesson plans will be reviewed and shared online as user-contributed content.

Phelps, C. S.; Chambers, L. H.; Alston, E. J.; Moore, S. W.; Oots, P. C.

2005-05-01

108

Improved vortex reactor system  

DOEpatents

An improved vortex reactor system for affecting fast pyrolysis of biomass and Refuse Derived Fuel (RDF) feed materials comprising: a vortex reactor having its axis vertically disposed in relation to a jet of a horizontally disposed steam ejector that impels feed materials from a feeder and solids from a recycle loop along with a motive gas into a top part of said reactor.

Diebold, James P. (Lakewood, CO); Scahill, John W. (Evergreen, CO)

1995-01-01

109

Vortex diode jet  

DOEpatents

A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.

Houck, Edward D. (Idaho Falls, ID)

1994-01-01

110

Vortex diode jet.  

National Technical Information Service (NTIS)

A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high re...

E. D. Houck

1993-01-01

111

Program of Research in Laminar Flow Control in the JIAFS at NASA Langley Research Center.  

National Technical Information Service (NTIS)

At high Reynolds numbers, the performance of a low drag suction LFC airplane is essentially controlled by the induced drag and the turbulent friction drag of the nonlaminarized area. The question then arises as to how the airplane cruise lift to drag rati...

W. Pfenninger

1981-01-01

112

Vortex crystals in fluids  

NASA Astrophysics Data System (ADS)

It is common in geophysical flows to observe localized regions of enhanced vorticity. This observation can be used to derive model equations to describe the motion and interaction of these localized regions, or vortices, and which are simpler than the original PDEs. The best known vortex model is derived from the incompressible Euler equations, and treats vortices as points in the plane. A large part of this dissertation utilizes this particular model, but we also survey other point vortex and weakly viscous models. The main focus of this thesis is an object known as the vortex crystal. These remarkable configurations of vortices maintain their basic shapes for long times, while perhaps rotating or translating rigidly in space. We study existence and stability of families of vortex crystals in the special case where N vortices have small and equal circulation and one vortex has large circulation. As the small circulation tends to zero, the weak vortices tend to a circle centered on the strong vortex. A special potential function of this limiting problem can be used to characterize orbits and stability. Whenever a critical point of this function is nondegenerate, we prove that the orbit can be continued via the Implicit Function Theorem, and its linear stability is determined by the eigenvalues of the Hessian matrix of the potential. For general N, we find at least three distinct families of critical points, one of which continues to a linearly stable class of vortex crystals. Because the stable family is most likely to be observed in nature, we study it extensively. Continuation methods allow us to follow these critical points to nonzero weak vortex strength and investigate stability and bifurcations. In the large N limit of this family, we prove that there is a unique one parameter family of distributions which minimize a "generalized" potential. Finally, we use point vortex and weakly viscous vortex models to analyze vortex crystal configurations observed in hurricane eyes and related numerical simulations. We find striking numerical and analytical agreement, thus validating the use of simplified vortex models to describe geophysical phenomena.

Barry, Anna M.

113

Optical vortex coronagraph.  

PubMed

We describe a method to observe dim exoplanets that eliminates light from the parent star across the entire exit pupil without sacrificing light from the planet by use of a vortex mask of topological charge m = 2. PMID:16389814

Foo, Gregory; Palacios, David M; Swartzlander, Grover A

2005-12-15

114

Wave–Vortex Interactions  

Microsoft Academic Search

\\u000a This chapter presents a theoretical investigation of wave–vortex interactions in fluid systems of interest to atmosphere and\\u000a ocean dynamics. The focus is on strong interactions in the sense that the induced changes in the vortical flow should be significant. In essence, such strong wave–vortex\\u000a interactions require significant changes in the potential vorticity (PV) of the flow either by advection of

O. Bühler

2010-01-01

115

Improved vortex reactor system  

DOEpatents

An improved vortex reactor system is described for affecting fast pyrolysis of biomass and Refuse Derived Fuel (RDF) feed materials comprising: a vortex reactor having its axis vertically disposed in relation to a jet of a horizontally disposed steam ejector that impels feed materials from a feeder and solids from a recycle loop along with a motive gas into a top part of said reactor. 12 figs.

Diebold, J.P.; Scahill, J.W.

1995-05-09

116

Vortex diode jet  

SciTech Connect

A fluid transfer system is described that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other. 10 figures.

Houck, E.D.

1994-05-17

117

Lightfoot Gets a New View of NASA Research  

NASA Website

NASA's Associate Administrator Robert Lightfoot, began his visit at NASA's Langley Research in typical fashion - as a leader. He ended it in an atypical role - as a mentee being mentored by researchers.

118

Vortex Characterization for Engineering Applications  

SciTech Connect

Realistic engineering simulation data often have features that are not optimally resolved due to practical limitations on mesh resolution. To be useful to application engineers, vortex characterization techniques must be sufficiently robust to handle realistic data with complex vortex topologies. In this paper, we present enhancements to the vortex topology identification component of an existing vortex characterization algorithm. The modified techniques are demonstrated by application to three realistic data sets that illustrate the strengths and weaknesses of our approach.

Jankun-Kelly, M; Thompson, D S; Jiang, M; Shannahan, B; Machiraju, R

2008-01-30

119

Quantum vortex reconnections  

NASA Astrophysics Data System (ADS)

We study reconnections of quantum vortices by numerically solving the governing Gross-Pitaevskii equation. We find that the minimum distance between vortices scales differently with time before and after the vortex reconnection. We also compute vortex reconnections using the Biot-Savart law for vortex filaments of infinitesimal thickness, and find that, in this model, reconnections are time symmetric. We argue that the likely cause of the difference between the Gross-Pitaevskii model and the Biot-Savart model is the intense rarefaction wave which is radiated away from a Gross-Pitaeveskii reconnection. Finally we compare our results to experimental observations in superfluid helium and discuss the different length scales probed by the two models and by experiments.

Zuccher, S.; Caliari, M.; Baggaley, A. W.; Barenghi, C. F.

2012-12-01

120

The structure of vortex breakdown  

Microsoft Academic Search

The term 'vortex breakdown', as used in the reported investigation, refers to a disturbance characterized by the formation of an internal stagnation point on the vortex axis, followed by reversed flow in a region of limited axial extent. Two forms of vortex breakdown, which predominate, are shown in photographs. One form is called 'near-axisymmetric' (sometimes 'axisymmetric'), and the other is

S. Leibovich

1978-01-01

121

Planetary Boundary Layer (PBL) Heights Derived From NASA Langley Airborne High Spectral Resolution Lidar (HSRL) Data Acquired During TexAQS/GoMACCS, CHAPS, and MILAGRO  

NASA Astrophysics Data System (ADS)

The NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL) was deployed on the NASA Langley B-200 King Air aircraft in the Mexico City metropolitan area during the Mega-city Initiative: Local and Global Research Observations (MILAGRO) campaign in March 2006; in the Houston metropolitan area during the Texas Air Quality Study (TexAQS)/Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) in August and September 2006; and in the Oklahoma City area during Cumulus Humilis Aerosol Processing Study (CHAPS) in June 2007. The HSRL instrument measures profiles of aerosol extinction, backscatter and depolarization. The height of the Planetary Boundary Layer was derived by identifying sharp gradients in the HSRL 532-nm aerosol backscatter signal profiles using an automated technique based on Brooks (2003) [I.M. Brooks, Finding Boundary Layer Top: Application of Wavelet Covariance Transform to Lidar Backscatter Profiles. Journal of Atmospheric and Oceanic Technology 20, 1092-1105, 2003]. The technique uses a Haar wavelet covariance transform with multiple wavelet dilation values to adapt to non-ideal conditions where there can be gradients in the background signals and the boundary layer can be ill defined. The technique also identifies the top and bottom of the transition (i.e. entrainment) zone. We have further modified the algorithm to find PBL heights using HSRL backscatter data acquired during GoMACCS and MILAGRO, where complex terrain and overlying aerosol layers further complicate identifying the boundary layer. In addition, PBL heights are derived from HSRL backscatter data acquired during the CHAPS campaign, in another urban environment where the terrain is not as complex. We will describe the algorithm modifications we have made and show boundary layer heights and transition zone thicknesses for HSRL measurements over the Oklahoma City, Houston, and Mexico City areas during CHAPS, TexAQS/GoMACCS, and MILAGRO.

Burton, S. P.; Ferrare, R. A.; Hostetler, C. A.; Hair, J. W.; Cook, A.; Harper, D.; Obland, M. D.; Rogers, R. R.

2007-12-01

122

Vortex pairs on surfaces  

SciTech Connect

A pair of infinitesimally close opposite vortices moving on a curved surface moves along a geodesic, according to a conjecture by Kimura. We outline a proof. Numerical simulations are presented for a pair of opposite vortices at a close but nonzero distance on a surface of revolution, the catenoid. We conjecture that the vortex pair system on a triaxial ellipsoid is a KAM perturbation of Jacobi's geodesic problem. We outline some preliminary calculations required for this study. Finding the surfaces for which the vortex pair system is integrable is in order.

Koiller, Jair [Centro de Matematica Aplicada, FGV/RJ, Praia de Botafogo 190 Rio de Janeiro, RJ, 22250-40 (Brazil); Boatto, Stefanella [Instituto de Matematica da UFRJ, C.P. 68530, Cidade Universitaria Rio de Janeiro, RJ 21945-970 (Brazil)

2009-05-06

123

First order vortex dynamics  

SciTech Connect

A non-dissipative model for vortex motion in thin superconductors is considered. The Lagrangian is a Galilean invariant version of the Ginzburg{endash}Landau model for time-dependent fields, with kinetic terms linear in the first time derivatives of the fields. It is shown how, for certain values of the coupling constants, the field dynamics can be reduced to first order differential equations for the vortex positions. Two vortices circle around one another at constant speed and separation in this model. {copyright} 1997 Academic Press, Inc.

Manton, N.S. [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW (England)

1997-05-01

124

Characterization of Particles in the Langley 0.3 Meter Transonic Cryogenic Tunnel Using Hot Wire Anemometry.  

National Technical Information Service (NTIS)

Hot wire anemometry was used to identify the nature of particles reportedly observed during free stream velocity measurements in the Langley 0.3-meter transonic cryogenic tunnel using a Laser Doppler Velocimeter. Since the heat-transfer process from the h...

J. J. Singh C. G. Marple W. T. Davis

1982-01-01

125

Experimental Results for the Eppler 387 Airfoil at Low Reynolds Numbers in the Langley Low-Turbulence Pressure Tunnel.  

National Technical Information Service (NTIS)

Experimental results were obtained for an Eppler 387 airfoil in the Langley Low Turbulence Pressure Tunnel. The tests were conducted over a Mach number range from 0.03 to 0.13 and a chord Reynolds number range for 60,000 to 460,000. Lift and pitching mome...

B. F. Millard B. S. Walker R. J. McGhee

1988-01-01

126

TES Regional and Global Atmospheric Chemistry Data Available From the NASA Langley Atmospheric Science Data Center  

NASA Astrophysics Data System (ADS)

TES Regional and Global Atmospheric Chemistry Data Available from the NASA Langley Atmospheric Science Data Center The Tropospheric Emission Spectrometer (TES) was launched into a sun-synchronous orbit aboard Aura, the third of NASA's Earth Observing System spacecraft, on July 15, 2004. The primary objective of TES is to make global, three-dimensional measurements of ozone and other chemical species involved in its formation and destruction. The NASA Langley Atmospheric Science Data Center (ASDC) is the archive and distribution center for data from the TES instrument. The TES instrument is a high-resolution imaging infrared Fourier-transform spectrometer that operates in both nadir and limb-sounding modes. TES standard Level 2 data products include global-scale vertical profile and total column measurements of ozone, water vapor, HDO, carbon monoxide, methane, and nitric acid for 16 orbits every other day. Additional products include atmospheric temperature profiles, surface temperatures, and land surface emissivity A recent reprocessing effort has produced a new version of the data which includes additional limb species and a new summary product. In the past year, Level 3 TES products have been released which provide daily or monthly global survey chemical species data interpolated onto a global latitude/longitude grid at selected pressure levels. Browse images for the Level 3 and associated Level 2 data are available with these new Level 3 products. Between global surveys, TES can make special observations using its ability to point at a specific location for a few minutes on any given orbit. This capability is used for targets such as gas-emitting volcanoes, for regional air quality studies, and in conjunction with field campaigns. The ASDC provides data access, services and tools for over 40 projects in the discipline areas of Earth's radiation budget, clouds, aerosols and tropospheric chemistry. Additional information is available from our web site, http://eosweb.larc.nasa.gov

Hunt, L. A.

2007-12-01

127

Magnetic vortex state stability, reversal and dynamics in restricted geometries.  

PubMed

Magnetic vortices are typically the ground states in geometrically confined ferromagnets with small magnetocrystalline anisotropy. In this article I review static and dynamic properties of the magnetic vortex state in small particles with nanoscale thickness and sub-micron and micron lateral sizes (magnetic dots). Magnetic dots made of soft magnetic material shaped as flat circular and elliptic cylinders are considered. Such mesoscopic dots undergo magnetization reversal through successive nucleation, displacement and annihilation of magnetic vortices. The reversal process depends on the stability of different possible zero-field magnetization configurations with respect to the dot geometrical parameters and application of an external magnetic field. The interdot magnetostatic interaction plays an important role in magnetization reversal for dot arrays with a small dot-to-dot distance, leading to decreases in the vortex nucleation and annihilation fields. Magnetic vortices reveal rich, non-trivial dynamical properties due to existance of the vortex core bearing topological charges. The vortex ground state magnetization distribution leads to a considerable modification of the nature of spin excitations in comparison to those in the uniformly magnetized state. A magnetic vortex confined in a magnetically soft ferromagnet with micron-sized lateral dimensions possesses a characteristic dynamic excitation known as a translational mode that corresponds to spiral-like precession of the vortex core around its equilibrium position. The translation motions of coupled vortices are considered. There are, above the vortex translation mode eigenfrequencies, several dynamic magnetization eigenmodes localized outside the vortex core whose frequencies are determined principally by dynamic demagnetizing fields appearing due to restricted dot geometry. The vortex excitation modes are classified as translation modes and radially or azimuthally symmetric spin waves over the vortex ground state. Studying the spin eigenmodes in such systems provides valuable information to relate the particle dynamical response to geometrical parameters. Unresolved problems are identified to attract attention of researchers working in the area of nanomagnetism. PMID:18681013

Guslienko, K Yu

2008-06-01

128

Current carrying vortex crystals  

NASA Astrophysics Data System (ADS)

Abrikosov vortices in a type-II superconducting film subjected to strong magnetic field B with periodic array of nanoholes of the density npin form sometimes a vortex crystal, even when they are driven by a transport current. It is shown numerically that the crystal melting and transition to the resistive state occurs as a coherent depinning of the single vortex dislocations. For a system with interstitial vortices, f = B/?0npin > 1, the mechanism of depinning depends on the current direction with respect to the pinning array. It was found that slightly above the critical current trajectories of moving vortices are not straight, but rather acquire a snake - like shape enveloping the system of pins. In contrast to the matching field case, f = 1, the transition to a resistive state is not coherent and is developing through formation of the “snake - like” vortex trajectories. It is pointed out that the depinning is closely associated with the appearance of a strongly varying electric field. We calculated the electric fields accompanying vortex crystal melting and found the voltage-current characteristics. When the pinning array is made random, the critical current is reduced.

Rosenstein, B.; Shapiro, I.; Berco, D.; Shapiro, B. Ya

2012-12-01

129

Laminar vortex boundary layers  

NASA Astrophysics Data System (ADS)

The interaction of a Burgers--Rott vortex with a rigid no-slip normal wall is investigated via direct numerical simulations of the unsteady axisymmetric Navier--Stokes equations. The flows in the boundary layer and away from the vortex core have a self-similar structure, i.e. the solutions at time t, radius r, height z, and Reynolds number Re can be reduced to single profiles for the angular momentum and the azimuthal vorticity dependent on a single similarity variable. The similarity variable is the direction normal to the wall scaled by Re^1/2 and a function of r and t. The boundary layer flow near the axis for low-Re consists of a matching between a Bödewadt-like flow near r=0, where the vortex flow is near solid-body rotation, and a potential vortex boundary layer flow. For medium Re, waves form within the core radius resulting from the inflection points in the Bödewadt-like profiles. At large Re, there are also waves that travel vertically along the interface between the rotational core and the irrotational flow outside the core at r? 1.

Arrese, Juan C.; Lopez, John M.

1996-11-01

130

CONTRIBUTIONS TO ACTIVE BUFFETING ALLEVIATION PROGRAMS BY THE NASA LANGLEY RESEARCH CENTER  

Microsoft Academic Search

Buffeting is an aeroelastic phenomenon which plagues high performance aircraft, especially those with twin vertical tails like the F\\/A-18, at high angles of attack. This buffeting is a concern from fatigue and inspection points of view. By means of wind-tunnel and flight tests, this phenomenon is well studied to the point that buffet loads can be estimated and fatigue life

Robert W. Moses

131

NASA LANGLEY RESEARCH CENTERÕS CONTRIBUTIONS TO INTERNATIONAL ACTIVE BUFFETING ALLEVIATION PROGRAMS  

Microsoft Academic Search

Buffeting is an aeroelastic phenomenon which plagues high performance aircraft, especially those with twin vertical tails like the F\\/A-18, at high angles of attack. This buffeting is a concern from fatigue and inspection points of view. By means of wind-tunnel and flight tests, this phenomenon is well studied to the point that buffet loads can be estimated and fatigue life

Robert W. Moses

132

Summary of Compliant and Multi-Arm Control at NASA. Langley Research Center.  

National Technical Information Service (NTIS)

The topics are presented in viewgraph form and include the: single arm system, single arm axis system, single arm control systems, single arm hand controller axis system, single arm position axis system, single arm vision axis system, single arm force axi...

F. W. Harrison

1992-01-01

133

NASA Langley Research Center HBCU/OMU Program: 1990 Student Support Survey.  

National Technical Information Service (NTIS)

The results of a survey of students who are receiving support through the Historically Black Colleges and Universities and Other Minority Universities are given. Information is given on the race, sex, ethnic distribution, grade point average distribution,...

R. L. Yang S. N. Tiwari

1991-01-01

134

The World Wide Web and Technology Transfer at NASA Langley Research Center  

Microsoft Academic Search

Service.As with LTRS, the emphasis of NTRS is ease of use and conceptual simplicity. When users accessNTRS, keywords are entered in the dialog box. If they wish, they may also select which collections ofdocuments to search. NTRS then returns a list of documents matching the specified search terms, fromwhich the user selects abstracts to view. If, after viewing an abstract,

Michael L. Nelson; David J. Bianco

1994-01-01

135

Open Rotor Noise Prediction at NASA Langley - Capabilities, Research and Development.  

National Technical Information Service (NTIS)

The high fuel prices of recent years have caused the operating cost of the airlines to soar. In an effort to bring down the fuel consumption, the major aircraft engine manufacturers are now taking a fresh look at open rotors for the propulsion of future a...

F. Farassat

2010-01-01

136

Analysis of NASA Common Research Model Dynamic Data.  

National Technical Information Service (NTIS)

Recent NASA Common Research Model (CRM) tests at the Langley National Transonic Facility (NTF) and Ames 11-foot Transonic Wind Tunnel (11-foot TWT) have generated an experimental database for CFD code validation. The database consists of force and moment,...

M. J. Acheson S. Balakrishna

2011-01-01

137

Exploring XP for Scientific Research  

Microsoft Academic Search

Can we successfully apply XP (Extreme Programming) in a scientific research context? A pilot project at the NASA Langley Research Center tested XPs applicability in this context. Since the cultural environment at a government research center differs from the customer-centric business view, eight of XPs 12 practices seemed incompatible with the existing research culture. Despite initial awkwardness, the authors determined

William A. Wood; William L. Kleb

2003-01-01

138

Technical Education Outreach in Materials Science and Technology Based on NASA's Materials Research.  

National Technical Information Service (NTIS)

The grant NAG-1 -2125, Technical Education Outreach in Materials Science and Technology, based on NASA s Materials Research, involves collaborative effort among the National Aeronautics and Space Administration s Langley Research Center (NASA-LaRC), Norfo...

J. A. Jacobs

2003-01-01

139

Two new vortex liquids  

NASA Astrophysics Data System (ADS)

In 1967, Reatto and Chester proposed that solid helium-4 might exhibit superfluidity, and in 1970, Leggett suggested what was thought to be a definitive experimental test: to find non-classical rotational inertia in a toroidal sample. More than three decades later, the observation by Kim and Chan of exactly that effect generated great interest and has been repeated and confirmed by a number of groups. However, many attempts to find actual superflow in truly solid samples have failed. Here, I draw an analogy with a second example of anomalous response to vorticity in a dissipative fluid, the vortex liquid phase in the pseudogap region of high-temperature superconductors, and propose that the solid helium experiments have been mischaracterized: what is observed is not supersolidity but an incompressible vortex liquid. This state is distinct from a conventional liquid in that its properties are dominated by conserved supercurrents flowing around a thermally fluctuating tangle of vortices.

Anderson, Philip W.

2007-03-01

140

Aeroacoustics of viscous vortex reconnection  

NASA Astrophysics Data System (ADS)

Reconnection of two anti-parallel vortex tubes is studied by direct numerical simulations and large-eddy simulations of the incompressible Navier-Stokes equations over a wide range (2000-50,000) of the vortex Reynolds number (Re). A detailed investigation of the flow dynamics is performed and at high Re, multiple reconnections are observed as the newly formed ``bridges'' interact by self and mutual induction. To investigate acoustics produced by the recoil action of the vortex threads, M"ohring's theory of vortex sound is applied to the flow field and evaluated at varying far-field locations. The acoustic solver is verified against calculations of laminar vortex ring collision. For anti-parallel vortex reconnection, the resulting far-field spectra are shown to be grid converged at low-to-mid frequencies. To assess the relevance to fully turbulent jet noise, the dependence of reconnection upon Reynolds number is investigated.

Paredes, Pedro; Nichols, Joseph W.; Duraisamy, Karthik; Hussain, Fazle

2011-11-01

141

High sensitivity vortex shedding flowmeter  

SciTech Connect

This patent describes an apparatus for measuring fluid flows. It comprises: a flowmeter body including a flow passage; a vortex generator of an elongated cylindrical shape disposed across a cross section of the flow passage, wherein at lest one extremity of the vortex generator is secured to the flowmeter body; a transducer contained in a container vessel secured to the flowmeter body, wherein the transducer is pressed onto a thin wall of the container vessel; and a flexible coupling connecting the thin wall of the container vessel to a deflective portion of the vortex generating, wherein the flexible coupling enhances relative deflection between the vortex generator and the container vessel. Wherein fluctuating fluid dynamic forces resulting from vortices shed from the vortex generator and experienced by vortex generator generate fluctuating electrical signals from the transducer as a measure of fluid flow through the flow passage.

Lew, H.S.

1989-12-05

142

Confined Vortex Scrubber  

SciTech Connect

The program objective is to demonstrate efficient removal of fine particulates to sufficiently low levels to meet proposed small scale coal combustor emission standards. This is to be accomplished using a novel particulate removal device, the Confined Vortex Scrubber. This is the first quarterly technical progress report under this contract. Accordingly, a summary of the cleanup concept and the structure of the program is given here.

Not Available

1990-02-01

143

The vortex flap  

NASA Astrophysics Data System (ADS)

The Vortex Flap is a new type of mechanically driven high-lift device consisting of a rotating cylinder placed underneath and near the trailing edge of an airfoil. Wind tunnel tests were designed and conducted in the Washington University Low-Speed Wind Tunnel. Wind tunnel tests indicate that the Vortex Flap produces notable lift coefficient increments and increases maximum lift coefficients, particularly for the low Reynolds number range tested. The best configurations of the configurations investigated (not necessarily optimal) produce lift increments of 300-900% at low-to-moderate angles of attack, and increase the maximum lift coefficient on the order of 200%. The large lift increments found, particularly at low angles of attack, underscore the ability to drive the airfoil to high lift coefficients even at low angles of attack, a potentially useful characteristic for certain flight maneuvers. Regions of fairly high L/D (on the order of 10) as well as low L/D performance were identified. The nondimensional cylinder rotation speed was found to be the most important experimental parameter. Methods for correcting wind tunnel data were developed and outlined, and a Response Surface Method was applied to the corrected data for ease of interpretation. Performance comparisons between the Vortex Flap and other trailing-edge high-lift devices are included. To demonstrate the potential of the device, a Navy mission specification for a VTOL ship-borne UAV, currently filled by a rotary-wing aircraft, is analyzed using a hypothetical fixed wing aircraft and the Vortex Flap. It is demonstrated that, under certain reasonable wind-over-deck conditions, such an aircraft could hypothetically fill a VTOL mission.

Buerge, Brandon T.

144

Vortex generating mass flowmeter  

SciTech Connect

This patent describes a vortex generating flowmeter. It comprises: a first port; a second port; a flow measurement passage between the ports; a restriction formed in the flow passage between the first and second ports, the restriction comprising a converging diverging nozzle; a rod producing drag in the passage between the restriction and the second port; and means for sensing fluid pressure in the vicinity if the rod.

Hughes, N.

1990-01-30

145

Vortex Design Problem  

Microsoft Academic Search

In this investigation we are concerned with a family of solutions of the 2D steady--state Euler equations, known as the Prandtl--Batchelor flows, which are characterized by the presence of finite--area vortex patches embedded in an irrotational flow. We are interested in flows in the exterior of a circular cylinder and with a uniform stream at infinity, since such flows are

Bartosz Protas

2007-01-01

146

Confined vortex scrubber  

SciTech Connect

The program objective is to demonstrate efficient removal of fine particulates to sufficiently low levels to meet proposed small scale coal combustor emission standards. This is to be accomplished using a novel particulate removal device, the Confined Vortex Scrubber (CVS). The CVS consists of a cylindrical vortex chamber with tangential flue gas inlets. The clean gas exit is via tangent slots in a central tube. Liquid is introduced into the chamber and is confined with the vortex chamber by the centrifugal force generated by the gas flow itself. This confined liquid forms a layer through which the flue gas is then forced to bubble, producing a strong gas/liquid interaction, high inertial separation forces and efficient particulate cleanup. In effect, each of the sub-millimeter diameter gas bubbles in the liquid layer acts as a micro-cyclone, inertially separating particles into the surrounding liquid. The CVS thus obtains efficient particle removal by forcing intimate and vigorous interaction between the particle laden flue gas and the liquid scrubbing medium.

Not Available

1990-05-01

147

Vortex structures in dipolar condensates  

SciTech Connect

We investigate the properties of single vortices and of the vortex lattice in a rotating dipolar condensate. We show that vortices in this system possess several features induced by the long-range anisotropic dipolar interaction between particles. For example, when the dipoles are polarized along the rotation axis, vortices may display a craterlike structure; when dipoles are polarized orthogonal to the rotation axis, the vortex cores take an elliptical shape and the vortex lattice no longer possesses hexagonal symmetry.

Yi, S. [Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77251-1892 (United States); Institute of Theoretical Physics, Chinese Academy of Science, Beijing, 100080 (China); Pu, H. [Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77251-1892 (United States)

2006-06-15

148

Laser transit anemometer measurements on a slender cone in the Langley unitary plan wind tunnel  

NASA Astrophysics Data System (ADS)

A laser transit anemometer (LTA) system was used to probe the boundary layer on a slender (5 degree half angle) cone model in the Langley unitary plan wind tunnel. The anemometer system utilized a pair of laser beams with a diameter of 40 micrometers spaced 1230 micrometers apart to measure the transit times of ensembles of seeding particles using a cross-correlation technique. From these measurements, boundary layer profiles around the model were constructed and compared with CFD calculations. The measured boundary layer profiles representing the boundary layer velocity normalized to the edge velocity as a function of height above the model surface were collected with the model at zero angle of attack for four different flow conditions, and were collected in a vertical plane that bisected the model's longitudinal center line at a location 635 mm from the tip of the forebody cone. The results indicate an excellent ability of the LTA system to make velocity measurements deep into the boundary layer. However, because of disturbances in the flow field caused by onboard seeding, premature transition occurred implying that upstream seeding is mandatory if model flow field integrity is to be maintained. A description and results of the flow field surveys are presented.

Humphreys, William M., Jr.; Hunter, William W., Jr.; Covell, Peter F.; Nichols, Cecil E., Jr.

1990-12-01

149

Disrupted states of vortex flow and vortex breakdown  

Microsoft Academic Search

Flow visualization studies and laser Doppler anemometer measurements on swirling water flows reveal six distinct types of very large amplitude disturbance modes of the vortex core. Three, 'axisymmetric' and spiral vortex breakdowns, and the 'double helix,' have been described by others. A definite order of evolution in parameter space (Reynolds number and circulations) occurs, and is described. Puzzling responses of

J. H. Faler; S. Leibovich

1977-01-01

150

Geometric Methods for Vortex Extraction  

Microsoft Academic Search

This paper presents two vortex detection methods which are based on the geometric properties of streamlines. Unlike traditional vortex detection meth- ods, which are based on point-samples of physical quantities, one of our methods is also effective in detecting weak vortices. In addition, it allows for quantitative feature extraction by calculating numerical attributes of vortices. Results are pre- sented of

I. Ari Sadarjoen; Frits H. Post

151

Instability of a junction vortex  

Microsoft Academic Search

The flow field in the region where a moving wall, started from rest, slides under a stationary one, produces an interesting flow phenomena with relatively simple generation geometry. Experiments show that if the wall speed is high enough a vortex forms close to the junction of the moving wall with the stationary one. Vortex formation was observed for the range

Takashi Naitoh; James Allen

2005-01-01

152

Fast-Time Simulation Environment for Airborne Merging and Spacing Research.  

National Technical Information Service (NTIS)

As part of NASA's Distributed Air/Ground Traffic Management (DAG-TM) effort, NASA Langley Research Center is developing concepts and algorithms for merging multiple aircraft arrival streams and precisely spacing aircraft over the runway threshold. An airb...

F. J. L. Bussink N. A. Doble B. E. Barmore S. Singer

2005-01-01

153

Further Investigation of the Support System Effects and Wing Twist on the NASA Common Research Model.  

National Technical Information Service (NTIS)

An experimental investigation of the NASA Common Research Model was conducted in the NASA Langley National Transonic Facility and NASA Ames 11-foot Transonic Wind Tunnel Facility for use in the Drag Prediction Workshop. As data from the experimental inves...

C. A. Hunter M. B. Rivers R. L. Campbell

2012-01-01

154

Karman vortex street parametrization with image processing application  

NASA Astrophysics Data System (ADS)

The karman vortex street phenomenon is applied in the vortex flowmeter. Application of various methods of investigations is necessary in the course of getting increased knowledge of the phenomenon. Flow visualization being the leading method of aero- and hydrodynamic phenomena investigations enables qualitative evaluation in micro-scale. Due to the image processing application in analysis of flow visualization pictures, calculation of geometrical parameters of the Karman vortex street is feasible. So, the quantitative information is obtained. The worked out methodology of investigations as well as designed software for analysis of vortex street pictures are described in the paper. The results of the carried out laboratory tests are reported. Flow visualization has been carried out on the especially designed laboratory tests are reported. Flow visualization has been carried out on the especially designed laboratory stand. The visualized flow has been recorded on the magnetic tape and then processed into set of consecutive frames. Four groups of frames of similar vortex development phases have been put on the image processing procedure. Distances between adjoining vortices have been calculated. On the basis of obtained results it can be stated, that in spite of probabilistic nature of the investigated phenomenon strengthened by the applied research method (flow visualization), the proposed method enables quantitative determination of Karman vortex street parameters.

Pankanin, Grzegorz; Kulinczak, Artur; Berlinski, Jerzy

2003-09-01

155

Chaotic Mixing around a Quasigeostrophic Ellipsoidal Vortex  

NASA Astrophysics Data System (ADS)

In geophysical flows, coherent vortex structures persist for long time and they dominate both the dynamics and the scalar transport of geophysical turbulence. Meacham et al.1,2) obtained a series of exact unsteady solution of the quasigeostrophic equation, which represents a uniform ellipsoidal vortex patch embedded in a uniform 3D shear field. These solutions are natural extension of the well known 2D Kirchhoff-Moore & Saffman-Kida elliptical vortices. The motion of fluid particles around a 2D elliptical vortex patch in an external shear flow has been investigated both numerically by Polvani & Wisdom3) and Dahleh4) and analytically by Kawakami & Funakoshi5). Chaotic mixing occurs in the regions near the heteroclinic orbits of the Poincare map of particle locations after every vortex rotation period and the chaotic region expands wider and wider as the strain increases. In this paper, the motion of fluid particle around an ellipsoidal vortex (almost a tilted spheroid) in an external 3D shear flow is examined analytically and numerically. When a spheroidal vortex is embedded in an otherwise quiescent fluid, it rotates rigidly with a constant angular velocity ? 0, which is a function of the aspect ratio. A fluid particle moves along a streamline in the coordinate system rotating with the spheroid. There are two saddles and heteroclinic orbits connecting them on the horizontal plane z=0 including the vortex center. The heteroclinic orbits change into homoclinic orbits on the horizontal plane slightly off center (z>0). One saddle becomes a node as z increases but the other remains to be a saddle with homoclinic orbits on the horizontal plane which intersects the vortex. We impose such perturbations as, 1) deformation to slightly non-spheroidal ellipsoid, 2) uniform horizontal strain and 3) uniform vertical shear on the tilted spheroidal vortex. In order to show the appearance of the chaotic motion analytically, we apply Melnikov's method to the perturbed system. The Melnikov functions computed along the heteroclinic and homoclinic orbits intersect zero transversely in any cases, suggesting the occurrence of chaotic mixing of fluid particles. In fact, numerically computed stroboscopic Poincare plots scatter along the heteroclinic and homoclinic orbits even when the perturbations are very weak. It is found that the chaotic region is wider on the plane z>0 and that the vertical shear induces the mixing most efficiently. The chaotic regions expand wider and wider as the perturbations become stronger. 1)S. P. Meacham, et al.: Dyn. Atmos. Oceans 21 (1994) 167. 2)S. P. Meacham, et al: Phys. Fluids 9 (1997) 2310. 3)L.M.Polvani & J.Wisdom: Phys. Fluids A2 (1990) 123. 4)M.D.Dahleh: Phys. Fluids A4 (1992) 1979. 5)A.Kawakami & M.Funakoshi: Fluid Dynamics Research 25 (1999) 167.

Miyazaki, T.; Yamamoto, M.

2002-05-01

156

Vortex safety in aviation  

NASA Astrophysics Data System (ADS)

The objective is the general review of impact of aircraft wake vortices on the follower aircraft encountering the wake. Currently, the presence of wake vortices past aircraft limits the airspace capacity and flight safety level for aircraft of different purposes. However, wake vortex nature and evolution have not been studied in full measure. A mathematical model simulating the process of near wake generation past bodies of different shapes, as well as the wake evolution after rolling-up into wake vortices (far wake) is developed. The processes are suggested to be modeled by means of the Method of Discrete Vortices. Far wake evolution is determined by its complex interaction with the atmosphere and ground boundary layer. The main factors that are supposed to take into account are: wind and ambient turbulence 3Ddistributions, temperature stratification of the atmosphere, wind shear, as well as some others which effects will be manifested as considerable during the investigation. The ground boundary layer effects on wake vortex evolution are substantial at low flight altitudes and are determined through the boundary layer separation.

Turchak, L. I.

2012-10-01

157

Geochemical Indicators and Seasonality Controls to Arsenic Mobility in Groundwater in Langley, British Columbia  

NASA Astrophysics Data System (ADS)

In this study, geochemical indicators are used to determine risk of arsenic mobilization in groundwater for an aquifer system in a temperate climate region. The study area is the township of Langley, BC, where arsenic in some well waters has been reported to be above the Canadian drinking water guideline (0.010 mg/l). Arsenic typically becomes mobile in reducing groundwaters and alkaline oxidizing groundwaters. Due to its mobility behavior, arsenic concentrations have been observed to correlate with anions and oxianions species in oxidizing waters, and to correlate with redox sensitive species in reducing waters. Historical groundwater geochemistry datasets available for the study area have variable data completeness and quality. Species observed to correlate with arsenic concentrations are queried in these datasets and used as indicators to produce an arsenic mobility risk map. A multi-proxy approach is used where a region is only considered to have high arsenic mobility potential if more than one indicator is observed. Preliminary data analyses show a positive correlation between arsenic and pH, with the highest arsenic concentrations occurring at a pH above 8. Geochemical modeling using PHREEQC demonstrates saturation with respect to hematite and goethite and undersaturation with respect to pyrite. No correlation is observed between arsenic and redox sensitive species, such as Fe, Mn, SO4 and NH4, while weak correlations were found between arsenic and pH sensitive species, as HCO3, Mo, B and F. These observations suggest that the groundwaters are oxidizing and that arsenic mobility is likely being controlled by desorption from solids as a result of groundwater alkaline conditions. Temporal variations in arsenic concentrations and associated species are examined with groundwater level variations to address seasonality controls to arsenic mobility and to identify potential long term trends. The results presented and the geochemical indicators used will be tested through extensive well water sampling and geochemical analyses starting in the summer of 2009.

Cavalcanti de A, R.; Kirste, D.; Allen, D.

2009-05-01

158

All-optical discrete vortex switch  

SciTech Connect

We introduce discrete vortex solitons and vortex breathers in circular arrays of nonlinear waveguides. The simplest vortex breather in a four-waveguide coupler is a nonlinear dynamic state changing its topological charge between +1 and -1 periodically during propagation. We find the stability domain for this solution and suggest an all-optical vortex switching scheme.

Desyatnikov, Anton S. [Nonlinear Physics Center, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Dennis, Mark R. [H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Ferrando, Albert [Interdisciplinary Modeling Group, InterTech and Departament d'Optica, Universitat de Valencia, E-46100 Burjassot (Spain)

2011-06-15

159

Modeling and simulation of vortex induced vibration on the subsea riser\\/pipeline (GRP pipe)  

Microsoft Academic Search

This paper presents the research work conducted to investigate the dynamics characteristics of the offshore riser pipeline due to vortex flow and to develop a model that could predict its vortex induced responses. Glass-fiber reinforced plastic (GRP) pipe is used for this study. A two-dimensional finite element computational method is implemented to approximately describe the dynamic behavior of the riser.

Raja Nor Fauziah bt Raja Adli; Ir. Idris Ibrahim

2011-01-01

160

Reduction of helicopter blade-vortex interaction noise by active rotor control technology  

Microsoft Academic Search

Helicopter blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently

Yung H. Yu; Bernd Gmelin; Wolf Splettstoesser; Jean J. Philippe; Jean Prieur; Thomas F. Brooks

1997-01-01

161

Vortex methods and their application to trailing wake vortex simulations  

NASA Astrophysics Data System (ADS)

Vortex methods are competitive for simulating incompressible unsteady flows, because they have negligible dispersion error and good energy conservation. The various methods are presented, including the recent developments: particle redistribution, diffusion, relaxation (by projection), efficient solvers (fast multipole method, vortex-in-cell method, hybrid method) and parallel computer implementations. Examples relating to wing/aircraft trailing wake vortices are presented: 2-D and 3-D, inviscid and viscous, direct numerical simulation and large eddy simulation. We consider wake roll-ups, vortex tube dynamics, 3-D instabilities and the complexity/turbulence they produce. A vortex system in ground effects is also presented. To cite this article: G. Winckelmans et al., C. R. Physique 6 (2005).

Winckelmans, Grégoire; Cocle, Roger; Dufresne, Louis; Capart, Raphaël

2005-05-01

162

Vortex dynamics in anisotropic traps  

SciTech Connect

We investigate the dynamics of linear vortex lattices in anisotropic traps in two dimensions and show that the interplay between the rotation and the anisotropy leads to a rich but highly regular dynamics.

McEndoo, S.; Busch, Th. [Department of Physics, University College Cork, Cork (Ireland)

2010-07-15

163

Discrete vortex representation of magnetohydrodynamics  

SciTech Connect

We present an alternative approach to statistical analysis of an intermittent ideal MHD fluid in two dimensions, based on the hydrodynamical discrete vortex model applied to the Elsasser variables. The model contains negative temperature states which predict the formation of magnetic islands, but also includes a natural limit under which the equilibrium states revert to the familiar twin-vortex states predicted by hydrodynamical turbulence theories. Numerical dynamical calculations yield equilibrium spectra in agreement with the theoretical predictions.

Kinney, R.; Tajima, T.; Petviashvili, N. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies; McWilliams, J.C. [National Center for Atmospheric Research, Boulder, CO (United States)

1993-02-01

164

Hydraulic characteristics of vertical vortex at hydraulic intakes * * Project supported by the National Natural Science Foundation of China (Grant No. 50379030) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20020610016)  

Microsoft Academic Search

The trace of vertical vortex flow at hydraulic intakes is of the shape of spiral lines, which was observed in the presented experiments with the tracer technique. It represents the fluid particles flow spirally from the water surface to the underwater and rotate around the vortex-axis multi-cycle. This process is similar to the movement of screw. To describe the multi-circle

Yun-liang CHEN; Chao WU; Mao YE; Xiao-ming JU

2007-01-01

165

Unpinning triggers for superfluid vortex avalanches  

NASA Astrophysics Data System (ADS)

The pinning and collective unpinning of superfluid vortices in a decelerating container is a key element of the canonical model of neutron star glitches and laboratory spin-down experiments with helium II. Here the dynamics of vortex (un-)pinning is explored using numerical Gross-Pitaevskii calculations, with a view to understanding the triggers for catastrophic unpinning events (vortex avalanches) that lead to rotational glitches. We explicitly identify three triggers: rotational shear between the bulk condensate and the pinned vortices, a vortex proximity effect driven by the repulsive vortex-vortex interaction, and sound waves emitted by moving and repinning vortices. So long as dissipation is low, sound waves emitted by a repinning vortex are found to be sufficiently strong to unpin a nearby vortex. For both ballistic and forced vortex motion, the maximum inter-vortex separation required to unpin scales inversely with pinning strength.

Warszawski, L.; Melatos, A.; Berloff, N. G.

2012-03-01

166

Acoustics Division recent accomplishments and research plans  

NASA Astrophysics Data System (ADS)

The research program currently being implemented by the Acoustics Division of NASA Langley Research Center is described. The scope, focus, and thrusts of the research are discussed and illustrated for each technical area by examples of recent technical accomplishments. Included is a list of publications for the last two calendar years. The organization, staff, and facilities are also briefly described.

Clark, L. R.; Morgan, H. G.

1986-07-01

167

ELDORA Observations during VORTEX 95.  

NASA Astrophysics Data System (ADS)

Airborne radar platforms have played an increasingly important role in advancing our understanding of storms that are either too remote or occur too infrequently for ground-based radars. Recognizing this potential, the National Center for Atmospheric Research and the Centre de Recherche en Physique de l'Environnment Terrestre et Planetaire have designed and developed ELDORA (Electra Doppler Radar), a tail Doppler radar with the following unique capabilities: 1) increased accuracy and sensitivity by averaging more independent samples in the radar pulse volume, 2) higher spatial resolution in the along-track direction by using a faster rotation rate of the antenna, and 3) a large unambiguous velocity measuring interval by means of a dual pulse repetition frequency. Although the first field deployment of ELDORA occurred in 1993, it was not until VORTEX (Verification of the Origins of Rotation in Tornadoes Experiment) that the system was operating up to its full capabilities. Examples of the radar's ability to detect clear-air phenomena are presented along with high-resolution images near severe local storms and tornadoes.

Wakimoto, Roger M.; Liu, Ching-Hwang; Lee, Wen-Chau; Hildebrand, Peter H.; Bluestein, Howard B.

1996-07-01

168

The hairpin vortex illusion  

NASA Astrophysics Data System (ADS)

It has long been customary to assume that vortical structures in turbulent flows are synonymous with regions of rotational motion. Mathematical implementations of this idea using numerical and experimental velocity data from turbulent boundary layers reveal the presence of hairpin vortices, both singly and in groups called packets. However, vorticity may be present that does not directly cause rotation, and by failing to take this into account it is possible to be misled as to the true nature of the vortical structures. In this work a vortex filament scheme is applied to boundary layer flow that allows for a view of structures unrestrained by the requirement that they be regions of rotational motion. It is found that furrow-like streamwise aligned eruptions of the nominally spanwise near-wall vorticity overlying low-speed streaks are the primary structural feature of the transitioning boundary layer. These progress from an arch-like form at their upstream end to either one or two-lobed mushroom-shapes at their downstream end. The rotational motion associated with the furrows has the appearance of hairpins. Mushroom-shaped structures rapidly breakdown into complex forms in the post-transitional region that may have rotational signatures similar to that of packets.

Bernard, Peter S.

2011-12-01

169

ME-?SR study in YBCO vortex states.  

NASA Astrophysics Data System (ADS)

We are analyzing ?SR vortex data of YBa2Cu3O7-? (Tc = 91 K). The average superconducting grain size is ˜20 ?m. The ?SR data are recorded in a transverse 1 kOe field and at temperatures below 10 K. The ?SR technique is used to probe the magnetic fields in the cuprate vortex state. The ?SR signals show an oscillatory time dependence. To determine the frequency-dependent signals, we use the Maximum Entropy (ME) transform technique. [2] The ME-Burg algorithm removes noise, and does not suffer from Fourier-like truncation effects. The frequency signals are better fit with Lorentzians than static Gaussians. This Lorentzian behavior indicates the existence of dynamic magnetism in and around the vortex cores. This is consistent with earlier YBCO vortex ME-?SR results [3] and the SO(5) modeling [4] of cuprate superconductivity, predicting the existence of antiferromagnetism in the vortex states. Research is supported by NSF-REU and WiSE at SJSU. [1] C. Boekema et al, Physica C282-287 (1997) 2069. [2] J Lee et al, J Appl Phys 95 (2004) 6906 and ref therein; AIP www: Virtual J Appl of Superconductivity 2004 V6 Iss11. [3] C. Boekema et al, 8th Int M2S-HTSC Conf, Physica C in press. [4] H-D Chen et al, Phys Rev B70 (2004) 024516; SC Zhang, Science 275 (1997) 1089.

Le, T. H.; Boekema, C.

2007-03-01

170

A nonlinear approximation for vortex sheet evolution and singularity formation  

NASA Astrophysics Data System (ADS)

The evolution of a vortex sheet in two-dimensional, incompressible, inviscid flow is governed by the integro-differential equation of Birkhoff-Rott. We derive a simple approximation for vortex sheet evolution, consisting of a system of four first-order differential equations. This approximate system has the advantage of involving only local operators. The errors in the approximation are shown to be relatively small even if the sheet has infinite curvature at a point. For the approximate equations, exact similarity solutions exhibiting singularity formation are constructed. Research supported by the National Science Foundation and the Alfred P. Sloan Foundation.

Caflisch, Russel E.; Semmes, Stephen

1990-03-01

171

Point vortex dynamics in a magnetized plasma  

Microsoft Academic Search

A self-consistent theory describing vortex-wave dynamics in a magnetized plasma has been formulated based on the Hasegawa-Mima equation by extending the modulated point vortex model so as to include the vortex-wave interactions. The energy and entrophy are shown to be conserved in contrast with the previous modulated point vortex description. Dynamical behaviors of vortices under the interaction with waves are

Mitsuo Kono; Hideaki Shibahara; Kentaro Yabuki

1994-01-01

172

Optical vortex coronagraphy with an elliptical aperture.  

PubMed

An optical vortex coronagraph that makes efficient use of a larger fraction of the clear aperture of a Cassegrain-type telescope is described. This design incorporates an elliptical subaperture rather than the conventional circular subaperture. We derive a new vortex phase mask that maintains the same theoretical contrast of a circularly symmetric vortex coronagraph. PMID:23314632

Ruane, Garreth J; Swartzlander, Grover A

2013-01-10

173

Photographic studies of quantized vortex lines  

Microsoft Academic Search

A study of the behavior of systems of quantized vortex lines in rotating superfluid4He is described. Using a photographic technique, the positions of the vortex cores at the free surface of the liquid are recorded in the form of time-lapse motion pictures. The observation of stationary arrays of vortices are discussed and a comparison with the predictions of rectilinear vortex

E. J. Yarmchukt; R. E. Packard

1982-01-01

174

Instability of vortex pair leapfrogging  

NASA Astrophysics Data System (ADS)

Leapfrogging is a periodic solution of the four-vortex problem with two positive and two negative point vortices all of the same absolute circulation arranged as co-axial vortex pairs. The set of co-axial motions can be parameterized by the ratio 0 < ? < 1 of vortex pair sizes at the time when one pair passes through the other. Leapfrogging occurs for ? > ?2, where ?=2-1 is the silver ratio. The motion is known in full analytical detail since the 1877 thesis of Gröbli and a well known 1894 paper by Love. Acheson [``Instability of vortex leapfrogging,'' Eur. J. Phys. 21, 269-273 (2000)] determined by numerical experiments that leapfrogging is linearly unstable for ?2 < ? < 0.382, but apparently stable for larger ?. Here we derive a linear system of equations governing small perturbations of the leapfrogging motion. We show that symmetry-breaking perturbations are essentially governed by a 2D linear system with time-periodic coefficients and perform a Floquet analysis. We find transition from linearly unstable to stable leapfrogging at ? = ?2 ~ 0.381966, where ?=12(5-1) is the golden ratio. Acheson also suggested that there was a sharp transition between a ``disintegration'' instability mode, where two pairs fly off to infinity, and a ``walkabout'' mode, where the vortices depart from leapfrogging but still remain within a finite distance of one another. We show numerically that this transition is more gradual, a result that we relate to earlier investigations of chaotic scattering of vortex pairs [L. Tophøj and H. Aref, ``Chaotic scattering of two identical point vortex pairs revisited,'' Phys. Fluids 20, 093605 (2008)]. Both leapfrogging and ``walkabout'' motions can appear as intermediate states in chaotic scattering at the same values of linear impulse and energy.

Tophøj, Laust; Aref, Hassan

2013-01-01

175

Vortex ice in nanostructured superconductors  

SciTech Connect

We demonstrate using numerical simulations of nanostructured superconductors that it is possible to realize vortex ice states that are analogous to square and kagome ice. The system can be brought into a state that obeys either global or local ice rules by applying an external current according to an annealing protocol. We explore the breakdown of the ice rules due to disorder in the nanostructure array and show that in square ice, topological defects appear along grain boundaries, while in kagome ice, individual defects appear. We argue that the vortex system offers significant advantages over other artificial ice systems.

Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia J [Los Alamos National Laboratory; Libal, Andras J [Los Alamos National Laboratory

2008-01-01

176

HIFiRE Direct-Connect Rig (HDCR) Phase I Scramjet Test Results from the NASA Langley Arc-Heated Scramjet Test Facility.  

National Technical Information Service (NTIS)

A series of hydrocarbon-fueled direct-connect scramjet ground tests has been completed in the NASA Langley Arc-Heated Scramjet Test Facility (AHSTF) at simulated Mach 8 flight conditions. These experiments were part of an initial test phase to support Fli...

A. Storch K. Cabell M. Gruber N. Hass

2011-01-01

177

A Fan Pressure Ratio Correlation in Terms of Mach Number and Reynolds Number for the Langley 0.3 Meter Transonic Cryogenic Tunnel.  

National Technical Information Service (NTIS)

Calibration data for the two dimensional test section of the Langley 0.3 Meter Transonic Cryogenic Tunnel were used to develop a Mach number-Reynolds number correlation for the fan pressure ratio in terms of test section conditions. Well established engin...

P. L. Lawing C. L. Ladson

1980-01-01

178

Atmospheric pressure ion focusing with a vortex stream.  

PubMed

For successful operation of ionization analysis techniques an efficient sampling and sample ion transportation into an analytical path are required. This is of particular importance for atmospheric pressure ionization sources like corona discharge, electrospray, MALDI, ionization with radioactive isotopes ((3)H, (63)Ni) that produce nonuniform spatial distribution of sample ions. The available methods of sample ion focusing with electric fields are either efficient at reduced pressure (to 1 Torr) or feature high sample losses. In this paper we suggest to use a highly whirled gas stream for atmospheric pressure ion focusing. We use a (63)Ni radioactive source to produce an ionized bipolar sample at atmospheric pressure. It is shown by experiments that compared to an aspiration method a forced highly whirled vortex stream allows one to enhance the efficiency of remote ionized sample collection at distances equal to the vortex sampler diameter by an order of magnitude. With a vortex stream, a sixfold increase in the efficiency of the radial ionized sample collection has been obtained. It may be deduced that with the vortex stream remote sampling obtains a new feature which is characterized by a considerable enhancement of the efficiency of the ionized sample collection and can be called as a "gas-dynamic" ionized sample focusing. Considered is the effect of recombination losses of the ionized sample during the remote sampling thereof with the vortex sampler. Prospects for a practical implementation of the vortex sampler for solving the problems of the customs control over the smuggling of radioactive ? and ? sources are made based on the research results. PMID:21872021

Kolomiets, Yuri N; Pervukhin, Viktor V

2011-07-12

179

Reevaluation of the NOAA/CMDL carbon monoxide reference scale and comparisons with CO reference gases at NASA-Langley and the Fraunhofer Institut  

SciTech Connect

The carbon monoxide (CO) reference scale created by the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL) is used to quantify measurements of CO in the atmosphere, calibrate standards of other laboratories and to otherwise provide reference gases to the community measuring atmospheric CO. This reference scale was created based upon a set of primary standards prepared by gravimetric methods at CMDL and has been propagated to a set of working standards. In this paper we compare CO mixing ratios assigned to the working standards by three approaches: (1) calibration against the original gravimetric standards, (2) calibration using only working standards as the reference gas, and (3) calibration against three new gravimetric standards prepared to CMDL. The agreement between these values was typically better than 1%. The calibration histories of CMDL working standards are reviewed with respect to expected rates of CO change in the atmosphere. Using a Monte Carlo approach to simulate the effect of drifting standards on calculated mixing ratios, we conclude that the error solely associated with the maintenance of standards will limit the ability to detect small CO changes in the atmosphere. We also report results of intercalibration experiments conducted between CMDL and the Diode Laser Sensor Group (DACOM) at the NASA Langley Research Center (Hampton, Virginia), and CMDL and the Fraunhofer-Institut (Garmisch-Partenkirchen, Germany). Each laboratory calibrated several working standards for CO using their reference gases, and these results were compared to calibrations conducted by CMDL. The intercomparison of eight standards (CO concentrations between approximately 100 and approximately 165 ppb) by CMDL and NASA agreed to better than +/- 2%. (Abstract Truncated)

Novelli, P.C.; Collins, J.E. Jr.; Myers, R.C.; Sachse, G.W.; Scheel, H.E. [Univ. of Colordo, Boulder, CO (United States)]|[Science and Technology Corporation, Hampton, VA (United States)]|[NOAA, Boulder, CO (United States)]|[NASA, Langley Research Center, Hampton, VA (United States)]|[Fraunhofer-Inst. fuer Atmospharishce Umweltforschung (Germany)

1994-06-01

180

Vortex Dynamics in Magnetized Plasmas  

Microsoft Academic Search

Low frequency dynamics of electrostatic fluctuations in strongly magnetized plasmas have been studied. It was found that perturbations in density and potential can be very localized, indicating the applicability of an approximate description based on a finite number of vortices. A model based on a few isolated vortical structures is discussed, with particular attention to vortex collapse, where three vortices

M. Kono; B. Krane; H. L. Pécseli; J. Trulsen

1998-01-01

181

Vortex imaging in unconventional superconductors  

NASA Astrophysics Data System (ADS)

The real space imaging of vortices in unconventional superconductors not only provides important information about the effectiveness of flux pinning that can inform high current applications, but also yields crucial insights into the form of the superconducting order parameter. For example, the structure of the vortex lattice reflects effective mass and order parameter anisotropies within the material, and profiles of isolated vortices provide a local measure of the magnetic penetration depth that can be used to infer the superfluid density. We describe here the analysis of recent studies whereby state-of-the-art scanning Hall probe microscopy (SHPM) has been used to perform vortex-resolved magnetic imaging on two distinct families of unconventional superconductors. Two sets of results will be analysed in detail; (i) vortex lattice structural transitions in the p-wave superconductor Sr2RuO4 that reflect underlying anisotropies in the system and (ii) a quantitative analysis of vortex profiles in Co-doped 122 pnictide superconductors (SrFe2?xCoxAs2 & BaFe2?xCoxAs2) that allows one to infer the temperature-dependent superfluid density. The latter has then been compared with predictions for different order parameter models for a multiband superconductor.

Bending, S. J.; Curran, P. J.; Desoky, W. M. A.; Khotkevych, V. V.; Gibbs, A.; Mackenzie, A. P.; Tamegai, T.; Sebastian, S. E.

2012-09-01

182

Transverse force on a vortex and vortex mass: Effects of free bulk and vortex-core bound quasiparticles  

NASA Astrophysics Data System (ADS)

The paper reassesses the old but still controversial problem of the transverse force on a vortex and the vortex mass. The transverse force from free bulk quasiparticles on the vortex, both in the Bose and the Fermi liquids, originates from the Aharonov-Bohm effect. However, in the Fermi liquid, one should take into account peculiarities of the Aharonov-Bohm effect for BCS quasiparticles described by two-component spinor wave functions. There is no connection between the transverse force (either from free bulk quasiparticles or from vortex-core bound quasiparticles) and the spectral flow in the vortex core in superfluid Fermi liquid, in contrast to widely known claims. In fact, there is no steady spectral flow in the core of the moving vortex, and the analogy with the Andreev bound states in the superconductor-normal-metal-superconductor junction, where the spectral flow is really possible, is not valid in this respect. The role of the backflow on the vortex mass is clarified. The backflow is an inevitable consequence of a mismatch between the currents inside and outside the vortex core and restores the conservation of the particle number (charge) violated by this mismatch. In the Fermi liquid, the backflow compensates the current through the core bound states, which is a source of the vortex mass (the Kopnin mass). This results in renormalization of the Kopnin vortex mass by a numerical factor.

Sonin, E. B.

2013-04-01

183

Confined vortex scrubber offers high-efficiency acid gas and particulate removal  

SciTech Connect

Over the years, proponents of the defense industry have maintained that many of the technologies developed for the military can be successfully adapted to civilian applications. One example of such technology transfer could be the use of confined vortex scrubbers for emission control applications. Originally developed during research into nuclear rocket propulsion, these devices use the force generated by rotational gas flow to hold introduced liquid in a stable vortex. The resulting contact between gas and liquid phases removes acid gases and particulate matter from combustion process offgases. The use of a confined vortex scrubber for emission control is described in this paper. 1 ref., 2 figs.

NONE

1995-05-01

184

Preliminary study of the three-dimensional deformation of the vortex in Karman vortex street  

NASA Astrophysics Data System (ADS)

The mechanism for 3D evolution of the isolated Karman vortex and the thin-vortex filament in a circular cylinder wake is studied numerically using the LIA method. The results show that the vortex motion is unstable for small 3D disturbances in the separated wake of a circular cylinder. Karman vortex in the time-averaged wake flowfield wolves into a horseshoe-spoon-like 3D structure. The thin vortex filament deforms three-dimensionally in the braid and generates streamwise vortex structures which incline to the region maximum-deformation direction of the flowfield.

Ling, Guocan; Guo, Liang; Wu, Zuobin; Ma, Huiyang

1992-03-01

185

Microwave radiometer sensor technology research for Earth science measurements  

Microsoft Academic Search

A research program has been initiated at NASA Langley Research Center to investigate the critical technologies for developing advanced microwave radiometers suitable for Earth science observations. A significant objective of this research is to enable microwave measurements with adequate spatial resolutions for a number of Earth science parameters, such as sea ice, precipitation, soil moisture, sea surface temperature, and wind

Richard F. Harrington; Marion C. Bailey; Bruce M. Kendall; Lyle C. Schroeder; Roland W. Lawrence; Thomas G. Campbell

1993-01-01

186

Optical Rankine Vortex and Anomalous Circulation of Light  

SciTech Connect

Rankine vortex characteristics of a partially coherent optical vortex are explored using classical and physical optics. Unlike a perfectly coherent vortex mode, the circulation is not quantized. Excess circulation is predicted owing to the wave nature of composite vortex fields. Based on these findings, we propose a vortex stellar interferometer.

Swartzlander, Grover A. Jr.; Hernandez-Aranda, Raul I. [College of Optical Sciences, University of Arizona, Tucson, Arizona 85718 (United States); Photonics and Mathematical Optics Group, Tecnologico de Monterrey, Monterrey 64849 (Mexico)

2007-10-19

187

Dynamics of vortex line in presence of stationary vortex  

NASA Astrophysics Data System (ADS)

The motion of a thin vortex with infinitesimally small vorticity in the velocity field created by a steady straight vortex is studied. The motion is governed by non-integrable PDE generalizing the Nonlinear Schrodinger equation (NLSE). Situation is essentially different in a co-rotating case, which is analog of the defocusing NLSE and a counter-rotating case, which can be compared with the focusing NLSE. The governing equation has special solutions shaped as rotating helixes. In the counter-rotating case all helixes are unstable, while in the co-rotating case they could be both stable and unstable. Growth of instability of counter-rotating helix ends up with formation of singularity and merging of vortices. The process of merging goes in a self-similar regime. The basic equation has a rich family of solitonic solutions. Analytic calculations are supported by numerical experiment.

Zakharov, Vladimir E.

2010-03-01

188

Experiments on jet/vortex interaction  

NASA Astrophysics Data System (ADS)

An experimental study was performed to evaluate the effect of a cold jet on a single trailing vortex. Flow visualization and particle image velocimetry (PIV) measurements were conducted in wind and water tunnels. The main parameters were the ratio of jet-to-vortex strength, the jet-to-vortex distance, the jet inclination angle and the Reynolds number. It was shown that the jet turbulence is wrapped around the vortex and ingested into it. This takes place faster with decreasing jet-to-vortex distance and increasing jet strength. Both time-averaged and instantaneous flow fields showed that the trailing vortex became diffused with its rotational velocity and vorticity levels reduced when the jet is located close to the vortex. The mechanism with which the jet interacts with the vortex is a combination of vortices shed by the jet and the turbulence. No noticeable differences were found within the Reynolds number range tested. The effect of jet on the vortex is delayed when the jet is blowing at an angle to the free stream and away from the vortex such as during take-off.

Margaris, P.; Marles, D.; Gursul, I.

2008-02-01

189

The role of optimal vortex formation in biological fluid transport  

PubMed Central

Animal phyla that require macro-scale fluid transport for functioning have repeatedly and often independently converged on the use of jet flows. During flow initiation these jets form fluid vortex rings, which facilitate mass transfer by stationary pumps (e.g. cardiac chambers) and momentum transfer by mobile systems (e.g. jet-propelled swimmers). Previous research has shown that vortex rings generated in the laboratory can be optimized for efficiency or thrust, based on the jet length-to-diameter ratio (L/D), with peak performance occurring at 3.5vortex ring formation. This new approach identifies simple rules for effective fluid transport, facilitates comparative biological studies of jet flows across animal phyla irrespective of their specific functions and can be extended to unify theories of optimal jet-based and flapping-based vortex ring formation.

Dabiri, John O; Gharib, Morteza

2005-01-01

190

Microburst Simulation via Vortex-Ring and Turbulent Jet Models.  

NASA Astrophysics Data System (ADS)

Microbursts, suggested as primary causes of many aircraft fatal crashes, are the subject of this research. A microburst, or low-level intense wind shear, is generated by a thunderstorm or a small rain cloud, and presents hazardous conditions for aircraft during take-off and landing maneuvers. Recently released data show that a microburst resembles a transient vortex ring. Three microburst models have been constructed in this study. First, the turbulent jet model encompasses a free jet at high altitude and a wall jet near the ground surface. Second, the vortex ring model is a combination of a primary and an image vortex ring, with an inviscid -viscous interaction at the central axial and surface regions. An unsteady version of this model is also provided by solving the trajectory equation with the Direct Formal Integration (DFI) method or with the Runge-Kutta method. Third and finally, the complete unsteady microburst model equations (conservation of mass, momentum, and energy), or what has been referred to as the Navier-Stokes model formulation, are solved by the successive over relaxation method. Results show that the microburst can be simulated accurately by impulsive turbulent jet at high altitude and a transient vortex ring in mid-air and near the ground surface. In addition to improved understanding of the physical nature of microbursts, the models presented here can also be used for flight simulation and the pilot training purposes.

Wan, Tung

191

Adiabatic preparation of vortex lattices  

NASA Astrophysics Data System (ADS)

By engineering appropriate artificial gauge potentials, a Bose-Einstein condensate (BEC) can be adiabatically loaded into a current-carrying state that is analogous to a vortex lattice of a rotating uniform Bose gas. We give two explicit, experimentally feasible protocols by which vortex lattices can be smoothly formed from a condensate initially at rest. In the first example we show how this can be achieved by adiabatically loading a uniform BEC into an optical flux lattice, formed from coherent optical coupling of internal states of the atom. In the second example we study a tight-binding model that is continuously manipulated in parameter space such that it smoothly transforms into the Harper-Hofstadter model with 1/3 flux per plaquette.

Baur, Stefan K.; Cooper, Nigel R.

2013-09-01

192

Vortex Molecules in Bose-Einstein Condensates  

NASA Astrophysics Data System (ADS)

Stable vortex dimers are known to exist in coherently coupled two component Bose-Einstein condensates (BECs). We construct stable vortex trimers in three component BECs and find that the shape can be controlled by changing the internal coherent (Rabi) couplings. Stable vortex N-omers are also constructed in coherently coupled N-component BECs. We classify all possible N-omers in terms of the mathematical graph theory. Next, we study effects of the Rabi coupling in vortex lattices in two-component BECs. We find how the vortex lattices without the Rabi coupling known before are connected to the Abrikosov lattice of integer vortices with increasing the Rabi coupling. In this process, vortex dimers change their partners in various ways at large couplings. We then find that the Abrikosov lattices are robust in three-component BECs.

Nitta, Muneto; Eto, Minoru; Cipriani, Mattia

2013-10-01

193

Phase diagram of magnetic vortex dynamics  

NASA Astrophysics Data System (ADS)

The dynamics of a magnetic vortex are influenced profoundly by nonlinear effects at large and small amplitudes. For example, a strongly driven magnetic vortex is unstable with respect to internal deformation, leading to reversal of its core magnetization. At small amplitudes, a nonlinear response is associated with pinning of the vortex core. Given these phenomena, there is an acute need for a global picture of vortex dynamics over a wide range of excitation amplitudes and frequencies. We have constructed a phase diagram of vortex dynamics in permalloy (Ni80Fe20) disks by probing the response spectrum over four orders of magnitude in excitation power. We identify the boundary separating pinned and unpinned dynamics in a phase space of amplitude and frequency. Our approach allows for a highly quantitative analysis of the pinning potential for localized defects and can be used to trace the dynamics of a single vortex from deep in the pinning regime to the onset of core reversal.

Chen, T. Y.; Galkiewicz, A. T.; Crowell, P. A.

2012-05-01

194

Vortex dynamics in patterned nanomagnets  

Microsoft Academic Search

Magnetic vortices in restricted geometries, characterized by a circulating in-plane magnetization and an out-of-plane vortex core, exhibit a rich excitation spectrum, of which the fundamental mode is a non-degenerate translational excitation that corresponds to circular motion of its core at a characteristic frequency. Recently there has been considerable interest in the unique dynamics of these vortices, motivated in part by

K. S. Buchanan; M. Grimsditch; F. Y. Fradin; S. D. Bader; V. Novosad

2009-01-01

195

Two-color interface vortex solitons  

SciTech Connect

We study the existence and properties of vortex solitons supported by an interface between two distinct optical lattices imprinted in nonlinear quadratic media. We analyze the impact of guiding parameters of lattices and phase mismatching conditions on the existence and stability of two-color interface vortex solitons. The salient point is that interface vortex solitons feature highly asymmetric profiles, and are stable throughout almost the entire existence domain.

Xu Zhiyong [Nonlinear Physics Center and Center for Ultrahigh-Bandwidth Devices for Optical Systems (CUDOS), Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2010-02-15

196

Quantum Kinematics of Bosonic Vortex Loops  

SciTech Connect

Poisson structure for vortex filaments (loops and arcs) in 2D ideal incompressible fluid is analyzed in detail. Canonical coordinates and momenta on coadjoint orbits of the area-preserving diffeomorphism group, associated with such vortices, are found. The quantum space of states in the simplest case of ''bosonic'' vortex loops is built within a geometric quantization approach to the description of a quantum fluid. Fock-like structure and non-local creation and annihilation operators of quantum vortex filaments are introduced.

Goldin, G.A.; Owczarek, R.; Sharp, D.H.

1999-05-06

197

Vortex Beams for Atomic Resolution Dichroism  

SciTech Connect

Vortex beams carrying orbital angular momentum have been produced recently with electron microscopy by interfering an incident electron beam with a grid containing dislocations. Here, we present an analytical derivation of vortex wave functions in reciprocal and real space. We outline their mathematical and physical properties and describe the conditions under which vortex beams can be used in scanning transmission microscopy to measure magnetic properties of materials at the atomic scale.

Idrobo Tapia, Juan C [ORNL; Pennycook, Stephen J [ORNL

2011-01-01

198

An investigation of counterrotating tip vortex interaction  

NASA Astrophysics Data System (ADS)

A tip vortex interaction model originally developed for compressors has been extended and adapted for use with counterrotating open rotors. Comparison of available acoustic data with predictions (made with and without the tip vortex model included) illustrate the importance of this interaction effect. This report documents the analytical modeling, a limited experimental verification, and certain key parametric studies pertaining to the tip vortex as a noise source mechanism for the unsteady loading noise of counterrotating properllers.

Majjigi, R. K.; Uenishi, K.; Gliebe, P. R.

1989-10-01

199

Facts and fallacies of vortex flowmeters  

SciTech Connect

Vortex flowmeters have been popular since the late 1960s. They have been sold as everything from a panacea for severe service flow applications to a direct replacement for orifice meters. In many ways, vortex flowmeters have not lived up to industry expectations and therefore, have obtained a bad reputation. However, vortex flowmeters can be good flow measurement devices if applied properly, and they do have a place in the processing industries for certain flow applications.

DeVries, E.A.

1982-08-01

200

Sierra Nevada Corporation Dream Chaser Testing Begins at NASA Dryden, Langley  

NASA Website

Sierra Nevada Corporation's (SNC) Space Systems Dream Chaser flight vehicle arrived at NASA's Dryden Flight Research Center in Edwards, Calif., Wednesday to begin tests of its flight and runway landing systems.

201

Interaction of a Strong Vortex with Decaying Turbulence.  

National Technical Information Service (NTIS)

The evolution of a localized, axially symmetric vortex under the action of shear stresses associated with decaying two-dimensional turbulent vorticity which is inhomogeneous in the presence of the vortex is studied analytically. For a vortex which is suff...

P. W. Terry

1988-01-01

202

Heat Transfer Investigation of Langley Research Center Transition Models at a Mach Number of 8, Volume 2.  

National Technical Information Service (NTIS)

The results are presented of a wind tunnel test program to determine aerodynamic heat transfer distributions on delta body and straight body transition models of the space shuttle. Heat transfer rates were determined by the phase-change paint technique on...

C. B. Johnson J. D. Warmbrod R. K. Matthews W. R. Martindale

1972-01-01

203

Vortex lattice inhomogeneity in spatially inhomogeneous superfluids  

SciTech Connect

A trapped degenerate Bose gas exhibits superfluidity with spatially nonuniform superfluid density. We show that the vortex distribution in such a highly inhomogeneous rotating superfluid is nevertheless nearly uniform. The inhomogeneity in vortex density, which diminishes in the rapid-rotation limit, is driven by the discrete way vortices impart angular momentum to the superfluid. This effect favors the highest vortex density in regions where the superfluid density is most uniform (e.g., the center of a harmonically trapped gas). A striking consequence of this is that the boson velocity deviates from a rigid-body form exhibiting a radial-shear flow past the vortex lattice.

Sheehy, Daniel E.; Radzihovsky, Leo [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)

2004-11-01

204

Flow visualizations of perpendicular blade vortex interactions  

NASA Astrophysics Data System (ADS)

Helium bubble flow visualizations have been performed to study perpendicular interaction of a turbulent trailing vortex and a rectangular wing in the Virginia Tech Stability Tunnel. Many combinations of vortex strength, vortex-blade separation (Z(sub s)) and blade angle of attack were studied. Photographs of representative cases are presented. A range of phenomena were observed. For Z(sub s) greater than a few percent chord the vortex is deflected as it passes the blade under the influence of the local streamline curvature and its image in the blade. Initially the interaction appears to have no influence on the core. Downstream, however, the vortex core begins to diffuse and grow, presumably as a consequence of its interaction with the blade wake. The magnitude of these effects increases with reduction in Z(sub s). For Z(sub s) near zero the form of the interaction changes and becomes dependent on the vortex strength. For lower strengths the vortex appears to split into two filaments on the leading edge of the blade, one passing on the pressure and one passing on the suction side. At higher strengths the vortex bursts in the vicinity of the leading edge. In either case the core of its remnants then rapidly diffuse with distance downstream. Increase in Reynolds number did not qualitatively affect the flow apart from decreasing the amplitude of the small low-frequency wandering motions of the vortex. Changes in wing tip geometry and boundary layer trip had very little effect.

Rife, Michael C.; Davenport, William J.

1992-10-01

205

Wake vortex alleviation using rapidly actuated segmented Gurney flaps  

NASA Astrophysics Data System (ADS)

All bodies that generate lift also generate circulation. The circulation generated by large commercial aircraft remains in their wake in the form of trailing vortices. These vortices can be hazardous to following aircraft due to their strength and persistence. To account for this, airports abide by spacing rules which govern the frequency with which aircraft can use their runways when operating in instrument flight rules. These spacing rules are the limiting factor on increasing airport capacity. We conducted an experimental and computational study to assess the potential for using rapidly actuated segmented Gurney flaps, also known as Miniature Trailing Edge Effectors (MiTEs), for active wake vortex alleviation. Wind tunnel tests were performed on a half-span model NACA 0012 wing equipped with an array of 13 independent MITE pairs. The chord-based Reynolds number was around 350,000. Each MiTE could extend 0.015 chord lengths perpendicular to the freestream on the pressure side of the wing. Pressure profiles and a five-hole probe survey in the near wake were used to examine the influence that the MiTEs had upon the wing aerodynamics and the vortex rollup process. Particle image velocimetry was used to measure the static and time-dependent response of the vortex in the intermediate wake to various MiTE actuation schemes. These results were used to form complete initial conditions for vortex filament computations of the far wake evolution. Results from these computations showed that the perturbations created by MiTEs could be used to excite a variety of three-dimensional inviscid vortex instabilities. Finally, the research performed on MiTEs led to the invention of a more practical wake alleviation device: the spanwise actuating Gurney flap. Prototype tests showed that this device could produce similar perturbations to the MiTEs.

Matalanis, Claude G.

206

Detrainment from a Vortex Pair in a Nonstratified Fluid  

NASA Astrophysics Data System (ADS)

Laboratory experiments of detrainment from a vortex pair are reported to better understand and numerically model the evolution of aircraft trailing wake vortices. The vortex pair was generated by towing a model wing down a water-filled, unstratified towing tank at an angle of attack. Nearly neutrally buoyant particles were introduced into the vortex cell or into the vortex core. The detrainment of fluid from the vortex cell is shown to be faster than the detrainment from the vortex core.

Delisi, Donald P.; Lai, David Y.

2011-09-01

207

Major research topics in combustion  

Microsoft Academic Search

The Institute for Computer Applications in Science and Engineering (ICASE) and NASA Langley Research Center (LaRC) hosted a workshop on October 2--4, 1989 to discuss some combustion problems of technological interest to LaRC and to foster interaction with the academic community in these research areas. The topics chosen for this purpose were flame structure, flame holding\\/extinction, chemical kinetics, turbulence-kinetics interaction,

M. Y. Hussaini; A. Kumar; R. G. Voigt

1992-01-01

208

A Large Scale PIV Investigation of a Flap Edge Vortex  

Microsoft Academic Search

A recent experiment at NASA\\/Ames Research Center demonstrated the application of a large scale 'on-line' Particle Image Velocimetry, (PIV), in a 7' x 10' wind tunnel. Data was collected for freestream velocities in the range from approximately 40 m\\/sec to 100 m\\/sec. The flow field of interest for this investigation was a vortex that was generated by a flap edge.

Stephen M. Walker; M. B. Alkislar; L. Lourenco; A. Krothapalli

1996-01-01

209

Improving propulsive efficiency through passive mechanisms using a Starling vortex generator  

NASA Astrophysics Data System (ADS)

Ruiz et al. (2011) demonstrated that pulsed propulsion with vortex rings, much like those seen in the wake of jellyfish and squid, can greatly enhance the overall efficiency of submersible vehicles. The objective of the present research is to achieve pulsed propulsion passively using a Starling vortex generator which consists of a collapsible tube within an airtight box. Recent work has shown that a Starling vortex generator is able to generate vortex rings, which indicates enhanced propulsion, while requiring less energy to generate pulsatility than the system by Ruiz et al. (2011). Current work is focused on conducting an experimental parameter study to determine an empirical scaling law suitable for design purposes, with the aim to integrate the device into a full-scale unmanned undersea vehicle.

Whittlesey, Robert; Dabiri, John

2011-11-01

210

A flow physics study of flap-mounted vortex generators on a multi-element airfoil  

NASA Astrophysics Data System (ADS)

Vortex generators are a commonly used aerodynamic "fix" for flow separation problems. They are typically used to remedy flow separation due to design shortcomings or changes in operating conditions that exceed the original design point. Flow separation is often encountered with high lift systems. Flaps and slats can be difficult to design due to complicated flow phenomena and large Reynolds number effects. Previous research has indicated the effectiveness of vortex generators in correcting flow separation over a flap. In fact, significant aerodynamic performance improvements were predicted for high-lift systems that incorporate vortex generators in the original design. Before this may be attempted, a better understanding of vortex generator flow physics must be obtained for the development of appropriate design tools and analysis methods. The research contained herein is focused on a detailed flow physics study of vortex generators mounted to the flap of a three-element high-lift airfoil. Detailed velocity measurements taken using a three-component laser Doppler velocimeter were used to vortex/boundary layer interactions and global flowfield effects. The full Reynolds stress tensor and mean velocity field was measured in addition to surface pressures. Three basic vortex generator arrangements were studied: upflow, downflow, and corotating. Although not optimized, all three types of vortex generators were effective at eliminating boundary layer separation. The vortices demonstrated a tendency to rise from the flap surface regardless of orientation and decayed rapidly, with cross-stream vorticity dropping below measurable levels by 75% flap chord. However, the embedded vortices produced significant perturbations in the turbulence field and mean flow of the flap boundary layer that persisted to the flap trailing edge.

Klausmeyer, Steven Michael

211

Reduction of blade-vortex interaction noise through higher harmonic pitch control  

NASA Astrophysics Data System (ADS)

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4 to 5 dB) were found for low-speed descent conditions, where helicopter BVI noise is most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels.

Brooks, Thomas F.; Booth, Earl R., Jr.; Jolly, J. Ralph, Jr.; Yeager, William T., Jr.; Wilbur, Matthew L.

1990-01-01

212

Reduction of blade-vortex interaction noise using higher harmonic pitch control  

NASA Astrophysics Data System (ADS)

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4 to 5 dB) were found for low-speed descent conditions, where helicopter BVI noise is most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels.

Brooks, Thomas F.; Booth, Earl R., Jr.; Jolly, J. Ralph, Jr.; Yeager, William T., Jr.; Wilbur, Matthew L.

1989-07-01

213

Traversing field of view and AR-PIV for mid-field wake vortex investigation in a towing tank  

NASA Astrophysics Data System (ADS)

Wake vortex flow experiments are performed in a water tank where a 1:48 scaled model of a large transport aircraft A340-300 is towed at the speed of 3 and 5 ms-1 with values of the angle of attack ?={2°, 4°, 8°}. Particle image velocimetry (PIV) measurements are performed in a plane perpendicular to the towing direction describing the streamwise component of the wake vorticity. The instantaneous field of view (I-FOV) is traversed vertically with an underwater moving-camera device tracking the vortex core during the downward motion. An adaptive resolution (AR) image-processing technique is introduced that enhances the PIV interrogation in terms of spatial resolution and accuracy. The main objectives of the investigation are to demonstrate the applicability of PIV diagnostics in wake vortex research with towing-tank facilities. The specific implementation of the traversing field-of-view (T-FOV) technique and the AR image processing are driven by the need to characterize the vortex wake global properties as well as the vortex decay phenomenon in the mid- and far-field. Relevant aerodynamic information is obtained in the mid-field where the time evolution of the vortex structure (core radius and tangential velocity) and of the overall vortex wake (vortex trajectory, descent velocity, circulation) are discussed.

Scarano, F.; van Wijk, C.; Veldhuis, L. L. M.

2002-08-01

214

Exact Solution of the Bidirectional Vortex  

Microsoft Academic Search

In this paper, we present an inviscid solution that describes the cyclonic motion of a bidirectional vortex in a cylindrical chamber. The study is prompted by the need to characterize the flowfield inside a swirl-driven thrust chamber. This chamber has the advantage of confining mixing and combustion to an inner vortex tube that remains separated from the chamber walls by

Anand B. Vyas; Joseph Majdalani

2006-01-01

215

An investigation of counterrotating tip vortex interaction  

Microsoft Academic Search

A tip vortex interaction model originally developed for compressors has been extended and adapted for use with counterrotating open rotors. Comparison of available acoustic data with predictions (made with and without the tip vortex model included) illustrate the importance of this interaction effect. This report documents the analytical modeling, a limited experimental verification, and certain key parametric studies pertaining to

R. K. Majjigi; K. Uenishi; P. R. Gliebe

1989-01-01

216

Decoherence in Josephson vortex quantum bits  

Microsoft Academic Search

We investigated decoherence of a Josephson vortex quantum bit (qubit) in dissipative and noisy environment. As the Josephson vortex qubit (JVQ) is fabricated by using a long Josephson junction (LJJ), we use the perturbed sine-Gordon equation to describe the phase dynamics representing a two-state system and estimate the effects of quasiparticle dissipation and weakly fluctuating critical and bias currents on

Ju H. Kim; Ramesh P. Dhungana; Kee-Su Park

2007-01-01

217

Decoherence in Josephson Vortex Quantum Bits  

Microsoft Academic Search

We investigated decoherence of a Josephson vortex quantum bit (qubit) in dissipative and noisy environment. As the Josephson vortex qubit is fabricated by using a long Josephson junction (LJJ), we use the perturbed sine-Gordon equation to describe the phase dynamics representing a two-state system and estimate the effects of quasiparticle dissipation and weakly fluctuating critical and bias currents on the

Ju Kim; Ramesh Dhungana; Kee-Su Park

2006-01-01

218

Vortex-nozzle interactions in ramjet combustors  

Microsoft Academic Search

A facility designed to study the role of vortex-nozzle interactions in promoting low frequency instabilities in ramjet combustors is described. The design issues are outlined, as are potential instabilities. Preliminary data are reported which indicate the possibility of a recirculation vortex instability being an important mode.

K. Yu; S. Lee; H. E. Stewart; J. W. Daily

1986-01-01

219

Helical waves on a vortex filament  

NASA Astrophysics Data System (ADS)

A vortex filament in a perfect fluid is an excellent system, similar to an elastic string, elastic membrane, diffusion tube, and conducting rod, for presenting the equations of mathematical physics. A small amplitude helical wave spreading along an unstretchable vortex filament is shown to obey the linear Schrödinger equation. Taking into account elastic properties of the filament leads to the Klein-Gordon equation.

Dmitriyev, Valery P.

2005-06-01

220

Tkachenko Polarons in Vortex Lattices  

NASA Astrophysics Data System (ADS)

We analyze the properties of impurities immersed in a vortex lattice formed by ultracold bosons in the mean field quantum Hall regime. In addition to the effects of a periodic lattice potential, the impurity is dressed by collective modes with parabolic dispersion (Tkachenko modes). We derive the effective polaron model, which contains a marginal impurity-phonon interaction. The polaron spectral function exhibits a Lorentzian broadening for arbitrarily small wave vectors even at zero temperature, in contrast with the result for optical or acoustic phonons. The anomalous damping of Tkachenko polarons could be detected experimentally using momentum-resolved spectroscopy.

Caracanhas, M. A.; Bagnato, V. S.; Pereira, R. G.

2013-09-01

221

Vortex ratchet induced by controlled edge roughness  

NASA Astrophysics Data System (ADS)

We demonstrate theoretically and experimentally the generation of rectified mean vortex displacement resulting from a controlled difference between the surface barriers at the opposite borders of a superconducting strip. Our investigation focuses on Al superconducting strips where, in one of the two sample borders, a saw tooth-like array of micro-indentations has been imprinted. The origin of the vortex ratchet effect is based on the fact that (i) the onset of vortex motion is mainly governed by the entrance/nucleation of vortices and (ii) the current lines bunching produced by the indentations facilitates the entrance/nucleation of vortices. Only for one current direction the indentations are positioned at the side of vortex entry and the onset of the resistive regime is lowered compared to the opposite current direction. This investigation points to the relevance of ubiquitous border effects typically neglected when interpreting vortex ratchet measurements on samples with arrays of local asymmetric pinning sites.

Cerbu, D.; Gladilin, V. N.; Cuppens, J.; Fritzsche, J.; Tempere, J.; Devreese, J. T.; Moshchalkov, V. V.; Silhanek, A. V.; Van de Vondel, J.

2013-06-01

222

Nonlinear analysis for the evolution of vortex sheetsResearch supported in part by the Air Force Office of Scientific Research under grant AFOSR 85-0017 and URI grant AFOSR 86-0352 and by the Alfred P. Sloan Foundation  

Microsoft Academic Search

The perturbations in a nearly flat vortex sheet will initially grow due to Kelvin-Helmholtz instability. Asymptotic analysis and numerical computations of the subsequent nonlinear evolution show several interesting features. At some finite time the vortex sheet develops a singularity in its shape; i.e. the curvature becomes infinite at a point. This is immediately followed by roll-up of the sheet into

Russel E Caflisch

1988-01-01

223

The effects of long-chain polymers on tip vortex flow and cavitation inception  

NASA Astrophysics Data System (ADS)

Experiments have shown that propeller/hydrofoil tip vortex cavitation can be suppressed by properly injecting dilute polymer solutions at the tip. However, the mechanisms for this phenomenon are not well understood yet. To understand better the underlying flow physics the tip vortex flow generated by a rotating propeller in water and a dilute polymer solution (FENE-P model) was numerically simulated. It is found that the vortex flow structure is changed by the non-Newtonian features of polymers. Phenomenally the vortical rotation in a polymer solution is slower and the vortex center pressure is higher than in water. The non-Newtonian stress is much stronger than the Newtonian stresses in water. To further understand the non-Newtonian stresses contribution, the FENE-P model is also applied to a simplified quasi-cylindrical vortex. It is found analytically that in addition to the three normal stresses that are expected to be quadratic in the shear rate, one of the shear components is also quadratic. We also studied polymer effects on the dynamics of a bubble nucleus in the tip vortex. The bubble was found to grow to an elongated large cavity in water while it collapses in the polymer solution for the same cavitation number. This work was supported by the Office of Naval Research, Contract N00014-04-C-0110, monitored by Dr. Ki-Han Kim.

Zhang, Quan; Hsiao, Chao-Tsung; Chahine, Georges L.

2011-11-01

224

Majorana fermions in vortex lattices.  

PubMed

We consider Majorana fermions tunneling among an array of vortices in a 2D chiral p-wave superconductor or equivalent material. The amplitude for Majorana fermions to tunnel between a pair of vortices is found to necessarily depend on the background superconducting phase profile; it is found to be proportional to the sine of half the difference between the phases at the two vortices. Using this result we study tight-binding models of Majorana fermions in vortices arranged in triangular or square lattices. In both cases we find that the aforementioned phase-tunneling relationship leads to the creation of superlattices where the Majorana fermions form macroscopically degenerate localizable flat bands at zero energy, in addition to other dispersive bands. This finding suggests that tunneling processes in these vortex arrays do not change the energies of a finite fraction of Majorana fermions, contrary to previous expectation. The presence of flat Majorana bands, and hence less-than-expected decoherence in these vortex arrays, bodes well for the prospects of topological quantum computation with large numbers of Majorana states. PMID:24116796

Biswas, Rudro R

2013-09-25

225

Majorana Fermions in Vortex Lattices  

NASA Astrophysics Data System (ADS)

We consider Majorana fermions tunneling among an array of vortices in a 2D chiral p-wave superconductor or equivalent material. The amplitude for Majorana fermions to tunnel between a pair of vortices is found to necessarily depend on the background superconducting phase profile; it is found to be proportional to the sine of half the difference between the phases at the two vortices. Using this result we study tight-binding models of Majorana fermions in vortices arranged in triangular or square lattices. In both cases we find that the aforementioned phase-tunneling relationship leads to the creation of superlattices where the Majorana fermions form macroscopically degenerate localizable flat bands at zero energy, in addition to other dispersive bands. This finding suggests that tunneling processes in these vortex arrays do not change the energies of a finite fraction of Majorana fermions, contrary to previous expectation. The presence of flat Majorana bands, and hence less-than-expected decoherence in these vortex arrays, bodes well for the prospects of topological quantum computation with large numbers of Majorana states.

Biswas, Rudro R.

2013-09-01

226

Vortex dynamics in R4  

NASA Astrophysics Data System (ADS)

The vortex dynamics of Euler's equations for a constant density fluid flow in R4 is studied. Most of the paper focuses on singular Dirac delta distributions of the vorticity two-form ? in R4. These distributions are supported on two-dimensional surfaces termed membranes and are the analogs of vortex filaments in R3 and point vortices in R2. The self-induced velocity field of a membrane is shown to be unbounded and is regularized using a local induction approximation. The regularized self-induced velocity field is then shown to be proportional to the mean curvature vector field of the membrane but rotated by 90° in the plane of normals. Next, the Hamiltonian membrane model is presented. The symplectic structure for this model is derived from a general formula for vorticity distributions due to Marsden and Weinstein [``Coadjoint orbits, vortices and Clebsch variables for incompressible fluids,'' Physica D 7, 305-323 (1983)]. Finally, the dynamics of the four-form ? ? ? is examined. It is shown that Ertel's vorticity theorem in R3, for the constant density case, can be viewed as a special case of the dynamics of this four-form.

Shashikanth, Banavara N.

2012-01-01

227

Quantum vortex strings: A review  

SciTech Connect

The quantum worldsheet dynamics of vortex strings contains information about the 4d non-Abelian gauge theory in which the string lives. Here I tell this story. The string worldsheet theory is typically some variant of the CP{sup N-1} sigma-model, describing the orientation of the string in a U(N) gauge group. Qualitative parallels between 2d sigma-models and 4d non-Abelian gauge theories have been known since the 1970s. The vortex string provides a quantitative link between the two. In 4d theories with N=2 supersymmetry, the exact BPS spectrum of the worldsheet coincides with the bulk spectrum in 4d. Moreover, by tuning parameters, the CP{sup N-1} sigma-model can be coaxed to flow to an interacting conformal fixed point which is related to the 4d Argyres-Douglas fixed point. For theories with N=1 supersymmetry, the worldsheet theory suffers dynamical supersymmetry breaking and, more interestingly, supersymmetry restoration, in a way which captures the physics of Seiberg's quantum deformed moduli space.

Tong, David [Department of Applied, Mathematics and Theoretical Physics, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 OBA (United Kingdom)], E-mail: d.tong@damtp.cam.ac.uk

2009-01-15

228

1995 NASA High-Speed Research Program Sonic Boom Workshop, Volume 2.  

National Technical Information Service (NTIS)

The High-Speed Research Program and NASA Langley Research Center sponsored the NASA High-Speed Research Program Sonic Boom Workshop on September 12-13, 1995. The workshop was designed to bring together NASAs scientists and engineers and their counterparts...

1999-01-01

229

Vortex-induced vibrations of a sphere  

NASA Astrophysics Data System (ADS)

There are many studies on the vortex-induced vibrations of a cylindrical body, but almost none concerned with such vibrations for a sphere, despite the fact that tethered bodies are a common configuration. In this paper, we study the dynamics of an elastically mounted or tethered sphere in a steady flow, employing displacement, force and vorticity measurements. Within a particular range of flow speeds, where the oscillation frequency (f) is of the order of the static-body vortex shedding frequency (f_{vo}), there exist two modes of periodic large-amplitude oscillation, defined as modes I and II, separated by a transition regime exhibiting non-periodic vibration. The dominant wake structure for both modes is a chain of streamwise vortex loops on alternating sides of the wake. Further downstream, the heads of the vortex loops pinch off to form a sequence of vortex rings. We employ an analogy with the lift on an aircraft that is associated with its trailing vortex pair (of strength Gamma(*) and spacing b(*) ), and thereby compute the rate of change of impulse for the streamwise vortex pair, yielding the vortex force coefficient (cvortex): [ cvortex = {8}/{pi} {U^*_{v}}b^*( - Gamma^*). ] This calculation yields predicted forces in reasonable agreement with direct measurements on the sphere. This is significant because it indicates that the principal vorticity dynamics giving rise to vortex-induced vibration for a sphere are the motions of these streamwise vortex pairs. The Griffin plot, showing peak amplitudes as a function of the mass damping (m(*zeta) ), exhibits a good collapse of data, indicating a maximum response of around 0.9 diameters. Following recent studies of cylinder vortex-induced vibration, we deduce the existence of a critical mass ratio, m(*_{crit}) {?} 0.6, below which large-amplitude vibrations are predicted to persist to infinite normalized velocities. An unexpected large-amplitude and highly periodic mode (mode III) is found at distinctly higher flow velocities where the frequency of vibration (f) is far below the frequency of vortex shedding for a static body. We find that the low-frequency streamwise vortex pairs are able to impart lift (or transverse force) to the body, yielding a positive energy transfer per cycle.

Govardhan, R. N.; Williamson, C. H. K.

2005-05-01

230

Review of Ranque–Hilsch effects in vortex tubes  

Microsoft Academic Search

The vortex tube or Ranque–Hilsch vortex tube is a device that enables the separation of hot and cold air as compressed air flows tangentially into the vortex chamber through inlet nozzles. Separating cold and hot airs by using the principles of the vortex tube can be applied to industrial applications such as cooling equipment in CNC machines, refrigerators, cooling suits,

Smith Eiamsa-ard; Pongjet Promvonge

2008-01-01

231

Dynamics of vortex core switching in ferromagnetic nanodisks  

NASA Astrophysics Data System (ADS)

Dynamics of magnetic vortex core switching in nanometer-scale Permalloy disk, having a single vortex ground state, was investigated by micromagnetic modeling. When an in-plane magnetic field pulse with an appropriate strength and duration is applied to the vortex structure, additional two vortices, i.e., a circular and an antivortex, are created near the original vortex core. Sequentially, the vortex-antivortex pair annihilates. A spin wave is created at the annihilation point and propagated through the entire element; the relaxed state for the system is the single vortex state with a switched vortex core.

Xiao, Q. F.; Rudge, J.; Choi, B. C.; Hong, Y. K.; Donohoe, G.

2006-12-01

232

Vortex Method Simulation of Turbulent Channel Flow  

NASA Astrophysics Data System (ADS)

Turbulent flow in a channel is simulated using a vortex method. Smoothed vortex sheets cover the near wall region while the vorticity in the remainder of the flow is contained in convecting and stretching vortex filaments. The sheet elements are convected and regridded at each time step thus enabling evaluation of their wall-normal viscous diffusion and vortex stretching using finite differences. New filaments are created during significant ejection events initiated by parent vortices. Chorin's hairpin removal algorithm is used as a physically based subgrid model to limit the range of resolved scales. Calculations on the order of 2000 time steps have been completed thus far. From a perturbed state, the numerical solution develops toward a self-sustained turbulent flow. An initial explosive growth in the number of new vortex structures occurs as the flow compensates for the absence of sufficient spanwise vorticity in the initial conditions. Vortex production is self-limiting, however, and the flow subsequently relaxes toward a quasi-equilibrium in which new vortex filament creation occurs at only a small number of spatially intermittent locations. Preliminary statistics taken from the ongoing simulations suggest that the computational field is approaching the correct physical state. Supported by ONR Grant N00014-94-10106.

Bernard, Peter

1996-11-01

233

Vortex Ring Interaction with a Heated Screen  

NASA Astrophysics Data System (ADS)

Previous examinations of vortex rings impinging on porous screens has shown the reformation of the vortex ring with a lower velocity after passing through the screen, the creation of secondary vortices, and mixing. A heated screen could, in principle, alter the vortex-screen interaction by changing the local liquid viscosity and density. In the present investigation, a mechanical piston-cylinder vortex ring generator was used to create vortex rings in an aqueous sucrose solution. The rings impinged on a screen of horizontal wires that were heated using electrical current. The flow was visualized with food color and video imaging. Tests with and without heat were conducted at a piston stroke-to-jet diameter ratio of 4 and a jet Reynolds number (Re) of 1000. The vortex rings slowed after passing through the screen, but in tests with heat, they maintained a higher fraction of their before-screen velocity due to reduction in fluid viscosity near the wires. In addition, small ``fingers'' that developed on the front of the vortex rings as they passed through the screen exhibited positive buoyancy effects in the heated case.

Smith, Jason; Krueger, Paul S.

2008-11-01

234

High Mode Vortex Induced Vibration (VIV) Experiments on a Large-Scale Riser  

Microsoft Academic Search

The focus of this research is on the development and testing of a large-scale model riser (130 m in length) undergoing high mode vortex induced vibrations (VIV) in the ocean environment. This large scale model will provide an intermediate step between the common riser models (8-10 m in length) that have mainly been used to research VIV to date and

D. Murrin; M. Ordonez; G. Stone; N. Bose; Wei Qiu

2007-01-01

235

Contrasting vortex-gyration dispersions for different lattice bases in one-dimensional magnetic vortex arrays  

NASA Astrophysics Data System (ADS)

We performed micromagnetic numerical and analytical calculations in studying the effects of change in the primitive unit cells of one-dimensional (1D) vortex arrays on collective vortex-gyration dispersion. As the primitive basis, we consider alternating constituent materials (NiMnSb vs. Permalloy) and alternating dimensions including constituent disk diameter and thickness. In the simplest case, that of one vortex-state disk of given dimensions and single material in the primitive cell, only a single branch of collective vortex-gyration dispersion appears. By contrast, two constituent disks' different alternating materials, thicknesses, and diameters yield characteristic two-branch dispersions, the band widths and gaps of which differ in each case. This work offers not only an efficient means of manipulating collective vortex-gyration band structures but also a foundation for the development of a rich variety of 1D or 2D magnonic crystals and their band structures based on dipolar-coupled-vortex arrays.

Han, Dong-Soo; Jeong, Han-Byeol; Kim, Sang-Koog

2013-09-01

236

Propagation Dynamics of Electron Vortex Pairs  

NASA Astrophysics Data System (ADS)

Electron vortex beams carrying orbital angular momentum have been experimentally realized very recently. Here, we present the generation and propagation dynamics of electron vortex pairs embedded in a single beam, using a nanofabricated holographic grating. The rotation of two electron vortices with the same topological charges and the annihilation of two electron vortices with opposite charges were observed. The experimental results are well explained by the Gouy phase shift and confirmed by numerical simulations of the propagation. The results of this study may help develop an intuitive understanding of electron vortex motion and give a new viewpoint for analyzing electron microscope images and phase change in a crystal.

Hasegawa, Yuya; Saitoh, Koh; Tanaka, Nobuo; Uchida, Masaya

2013-07-01

237

Spin-orbit interactions in vortex singularimetry  

NASA Astrophysics Data System (ADS)

On scattering, the high strength singularity of a vortex beam breaks into a configuration of single charge vortices. The precise geometry of such a vortex constellation depends on the angle of incidence and the material properties of the scatterer, but also on the optical spin-orbit coupling as choosing different input and output polarization results in a family of vortex constellation. Measuring the position of the individual vortices allows us to reconstruct elements in an systematic expansion of the scattering matrix, in an analogy to optical aberration theory. We discuss in detail the dependence of the constellation geometry on external parameters, which is the basis for an optical metrology based on vortices.

Götte, Jörg B.; Dennis, Mark R.

2013-09-01

238

Observation of an x-ray vortex.  

PubMed

Phase singularities are a ubiquitous feature of waves of all forms and represent a fundamental aspect of wave topology. An optical vortex phase singularity occurs when there is a spiral phase ramp about a point phase singularity. We report an experimental observation of an optical vortex in a field consisting of 9-keV x-ray photons. The vortex is created with an x-ray optical structure that imparts a spiral phase distribution to the incident wave field and is observed by use of diffraction about a wire to create a division-of-wave-front interferometer. PMID:18033352

Peele, Andrew G; McMahon, Philip J; Paterson, David; Tran, Chanh Q; Mancuso, Adrian P; Nugent, Keith A; Hayes, Jason P; Harvey, Erol; Lai, Barry; McNulty, Ian

2002-01-01

239

Dissipative Vortex Dynamics and Magnus Force  

NASA Astrophysics Data System (ADS)

A single vortex in the infinite plane, emerging as a solution of a conservative PDE with global U(1) and Galilean symmetry, is a very special object. Its singular properties, as well as special symmetries of the governing equation, which are broken in more realistic models, have been a source of paradoxes and erroneous conclusions during the long history of theory of vortex motion. A detailed review containing further references is found in the recent monograph by this author [1]. This communication sketches main ideas and pitfalls of singular perturbation techniques that allow to describe slow vortex motion including effects of weak dissipation.

Pismen, L. M.

240

Aerodynamic, aeroacoustic, and aeroelastic investigations of airfoil-vortex interaction using large-eddy simulation  

NASA Astrophysics Data System (ADS)

In helicopters, vortices (generated at the tip of the rotor blades) interact with the next advancing blades during certain flight and manoeuvring conditions, generating undesirable levels of acoustic noise and vibration. These Blade-Vortex Interactions (BVIs), which may cause the most disturbing acoustic noise, normally occur in descent or high-speed forward flight. Acoustic noise characterization (and potential reduction) is one the areas generating intensive research interest to the rotorcraft industry. Since experimental investigations of BVI are extremely costly, some insights into the BVI or AVI (2-D Airfoil-Vortex Interaction) can be gained using Computational Fluid Dynamics (CFD) numerical simulations. Numerical simulation of BVI or AVI has been of interest to CFD for many years. There are still difficulties concerning an accurate numerical prediction of BVI. One of the main issues is the inherent dissipation of CFD turbulence models, which severely affects the preservation of the vortex characteristics. Moreover this is not an issue only for aerodynamic and aeroacoustic analysis but also for aeroelastic investigations as well, especially when the strong (two-way) aeroelastic coupling is of interest. The present investigation concentrates mainly on AVI simulations. The simulations are performed for Mach number, Ma = 0.3, resulting in a Reynolds number, Re = 1.3 x 106, which is based on the chord, c, of the airfoil (NACA0012). Extensive literature search has indicated that the present work represents the first comprehensive investigation of AVI using the LES numerical approach, in the rotorcraft research community. The major factor affecting the aerodynamic coefficients and aeroacoustic field as a result of airfoil-vortex interaction is observed to be the unsteady pressure generated at the location of the interaction. The present numerical results show that the aerodynamic coefficients (lift, moment, and drag) and aeroacoustic field are strongly dependent on the airfoil-vortex vertical miss-distance, airfoil angle of attack, vortex characteristics, and aeroelastic response of airfoil to airfoil-vortex interaction. A decay of airfoil-vortex interactions with the increase of vertical miss-distance and angle of attack was observed. Also, a decay of airfoil-vortex interactions is observed for the case of a flexible structure when compared with the case of a rigid structure. The decay of vortex core size produces a decrease in the aerodynamic coefficients.

Ilie, Marcel

241

Laboratory scale simulation of spontaneous vertical convective vortex generation  

NASA Astrophysics Data System (ADS)

The new mechanism of spontaneous vertical vortex generation in stratified fluid is under consideration. This phenomenon was discovered in the framework of experimental attempt [1] to proof the hypothesis of universal character of bifurcation curve formulated in [2]. The experiment with slow cubic cell inclination from bottom heating position was performed. The theoretically predicted curve form had been proved; but in the transition process from abnormal convection flow to normal one during bifurcation curve crossing the unexpected spontaneous vertical convective vortex motion has been discovered. Possibility of spontaneous vertical convective vortex generation application to atmospheric behavior explanation and to Earth's mantle one is discussed. New non-local hurricane generation mechanism and observed oceanic volcano archipelago's form explanation attempt are formulated and speculated. [1] AN Sharifulin, AN Poludnitsin, AS Kravchuk Laboratory Scale Simulation of Nonlocal Generation of a Tropical Cyclone. Journal of Experimental and Theoretical Physics, 2008, V.107, No.6, p.1090. [2] AI Nikitin, AN Sharifulin, Concerning the bifurcations of steady-state thermal convection regimes in a closed cavity due to the Whitney folding-type singularity. Heat Transfer -- Soviet Research, v.21, no.2, 1989, p.213.

Sharifulin, Albert; Poludnitsin, Anatoly

2009-11-01

242

GET AWAY SPECIAL PAYLOAD G-093: THE VORTEX RING TRANSIT EXPERIMENT (VORTEX) FLIGHTS  

Microsoft Academic Search

Get Away Special payload G-093 was designed and built by the University of Michigan Students for the Exploration and Development of Space. Also known as the VOrtex Ring Transit EXperiment (VORTEX), G-093 was flown on Shuttle mission STS-89 in January 1998 and again on STS-88 in December 1998. VORTEX was flown to answer some basic questions about fluid atomization—the process

Sven G. Bilén; Luis P. Bernal

243

Vortex lattices and crystalline geometries  

NASA Astrophysics Data System (ADS)

We consider AdS2×R2 solutions supported by a magnetic field, such as those which arise in the near-horizon limit of magnetically charged AdS4 Reissner-Nordstrom black branes. In the presence of an electrically charged scalar field, such magnetic solutions can be unstable to spontaneous formation of a vortex lattice. We solve the coupled partial differential equations that govern the charged scalar, gauge field, and metric degrees of freedom to lowest nontrivial order in an expansion around the critical point and discuss the corrections to the free energy and thermodynamic functions arising from the formation of the lattice. We describe how such solutions can also be interpreted, via S-duality, as characterizing infrared crystalline phases of conformal field theories doped by a chemical potential, but in zero magnetic field; the doped conformal field theories are dual to geometries that exhibit dynamical scaling and hyperscaling violation.

Bao, Ning; Harrison, Sarah; Kachru, Shamit; Sachdev, Subir

2013-07-01

244

Seasonal Changes in Vortex Behavior on Saturn  

NASA Astrophysics Data System (ADS)

The multi-filter images from the Imaging Science Subsystem (ISS) onboard Cassini are utilized to explore the vortex behavior on Saturn during the time period of 2004-2011 (starting in northern winter, moving through equinox, into northern spring). Our exploration is concentrated in the northern hemisphere, which is a follow-up study of the vortex survey in the southern hemisphere (Vasavada et al., 2006). We mainly utilize ISS images from two filters (i.e., MT3 and CB2), which probe the pressure levels around the tropopause and upper troposphere, respectively. Our exploration based on the maps in 2005 and 2008 suggests that there are significantly different vortex behaviors (i.e., size, spatial distribution, and vertical structure) between the two hemispheres. We are exploring more global maps after Saturn’s spring equinox (August, 2009) to see if there are seasonal effects on the vortex behavior.

Trammell, Harold J.; Li, L.; Smith, M. A.; Jiang, X.; Vasavada, A. R.

2012-10-01

245

Fluidic Vortex Amplifier for Environmental Control.  

National Technical Information Service (NTIS)

The work focused on a technology that uses a fluidic vortex amplifier for environmental control of industrial enclosures. The basic requirement for environmental control is a flow component that can vary its flow resistance quickly and automatically in re...

S. C. Chang

1987-01-01

246

Vortex Dynamics in Artificially Fabricated Superconducting Networks.  

National Technical Information Service (NTIS)

Contents: Vortex dynamics in Josephson-junction arrays; The superconducting transition of 2-D Josephson-junctions arrays in a small perpendicular magnetic field; Phase transition of frustrated two-dimensional Josephson-junction arrays; Phase fluctuations ...

H. S. J. van der Zant

1991-01-01

247

Vortex Dynamics and Separation Over Pitching Wings.  

National Technical Information Service (NTIS)

This project, aimed at an extensive study of the unsteady vortex dynamics and separation of pitching wings. Significant accomplishments were made in the project. These included extensive documentation of the 2-D velocity and vorticity field around a pitch...

B. R. Ramaprian

1995-01-01

248

Vortex sorter for Bose-Einstein condensates  

SciTech Connect

We have designed interferometers that sort Bose-Einstein condensates into their vortex components. The Bose-Einstein condensates in the two arms of the interferometer are rotated with respect to each other through fixed angles; different vortex components then exit the interferometer in different directions. The method we use to rotate the Bose-Einstein condensates involves asymmetric phase imprinting and is itself new. We have modeled rotation through fixed angles and sorting into vortex components with even and odd values of the topological charge of two-dimensional Bose-Einstein condensates in a number of states (pure or superposition vortex states for different values of the scattering length). Our scheme may have applications for quantum information processing.

Whyte, Graeme; Veitch, John; Courtial, Johannes [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Oehberg, Patrik [Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

2004-07-01

249

Vortex phase separation in mesoscopic superconductors.  

PubMed

We demonstrate that in mesoscopic type II superconductors with the lateral size commensurate with London penetration depth, the ground state of vortices pinned by homogeneously distributed columnar defects can form a hierarchical nested domain structure. Each domain is characterized by an average number of vortices trapped at a single pinning site within a given domain. Our study marks a radical departure from the current understanding of the ground state in disordered macroscopic systems and provides an insight into the interplay between disorder, vortex-vortex interaction, and confinement within finite system size. The observed vortex phase segregation implies the existence of the soliton solution for the vortex density in the finite superconductors and establishes a new class of nonlinear systems that exhibit the soliton phenomenon. PMID:23629058

Iaroshenko, O; Rybalko, V; Vinokur, V M; Berlyand, L

2013-01-01

250

Vortex phase separation in mesoscopic superconductors  

PubMed Central

We demonstrate that in mesoscopic type II superconductors with the lateral size commensurate with London penetration depth, the ground state of vortices pinned by homogeneously distributed columnar defects can form a hierarchical nested domain structure. Each domain is characterized by an average number of vortices trapped at a single pinning site within a given domain. Our study marks a radical departure from the current understanding of the ground state in disordered macroscopic systems and provides an insight into the interplay between disorder, vortex-vortex interaction, and confinement within finite system size. The observed vortex phase segregation implies the existence of the soliton solution for the vortex density in the finite superconductors and establishes a new class of nonlinear systems that exhibit the soliton phenomenon.

Iaroshenko, O.; Rybalko, V.; Vinokur, V. M.; Berlyand, L.

2013-01-01

251

On the evolution of laminar vortex rings  

NASA Astrophysics Data System (ADS)

Using Laser Doppler Anemometry (LDA) and Digital Particle Image Velocimetry (DPIV), the physical properties of laminar vortex rings are investigated in the Reynolds-number range 830 ? Re ? 1650. The measured initial circulations of the vortex rings are found to agree well with corrected versions of the vorticity-flux (slug-flow) model proposed by Didden and Pullin. The DPIV and LDA data show excellent agreement regarding local velocities and vortex-ring circulations. The DPIV data depict the distribution of the vorticity and circulation in the core regions, where the resulting vorticity distributions are found to be self-similar Gaussian profiles. The propagation velocity of the vortex rings is well approximated by an analytical model of Saffman for large core sizes. In the asymptotic limit t ? ?, the trajectories are in excellent agreement with the exact Stokes-dipole solution of Cantwell and Rott.

Weigand, A.; Gharib, M.

1997-04-01

252

Vortex renormalization in three space dimensions  

SciTech Connect

A three-dimensional heuristic renormalization-group theory for vortex filaments in three space dimensions is developed. It is based on a low-fugacity assumption and follows a methodology inspired by the Kosterlitz-Thouless analysis in two dimensions and its extension to three dimensions by Williams and Shenoy. The results agree with recent numerical and theoretical analyses of sparse vortex systems and, in a certain inconsistent simplification, reproduce the Williams smooth vortex theory and a form of its ``fractal`` extension by Shenoy. It is also shown that this theory is incomplete in its present form, pending an accounting for the dense vortex systems that arise at the transition. Nevertheless, the theory provides a check on other work and constitutes a potentially useful computational tool.

Chorin, A.J.; Hald, O.H. [Department of Mathematics, University of California, Berkeley, California 94720 (United States)

1995-05-01

253

Superconducting fraunhofer microscopy the one vortex problem  

NASA Astrophysics Data System (ADS)

A new kind of microscopy based on the Fraunhofer diffraction effect has been developed to determine the location of a single Abrikosov vortex that is trapped in a superconducting thin film, which in turn is one leg of a Josephson junction. With proper manipulation of currents, the vortex can be pushed to any desired location in the thin film. This microscopy has been used to measure the elementary pinning force on a single vortex in several different materials. Using these methods, it has been possible to follow a vortex as it begins to thermally depin and hops to different sites. Thermal depinning always seems to occur when the bulk superfluid density is about 4% of the zero temperature value.

Finnemore, D. K.

254

Spin dynamics in magnetic vortex structures  

NASA Astrophysics Data System (ADS)

This dissertation addresses spin dynamics in magnetic vortex structures, which have been experimentally investigated using time-resolved Kerr microscopy. This technique has been successfully implemented as a local spectroscopic probe to observe spin dynamics in geometrically confined magnetic structures with picosecond time resolution and spatial resolution on the order of a few hundred nanometers. Using electron-beam lithography, well-defined permalloy Ni81Fe19 disks with diameters in the range between 500 nm and 5 mum were fabricated. In the remnant state, permalloy disks form a flux-closure structure with a magnetic vortex core at the center of disk. The magnetization inside the core points out-of or into the disk plane. As the applied field decreases from a saturated state, the disks exhibit a distinct magnetization reversal process associated with the nucleation and subsequent annihilation of a magnetic vortex. The motion of a magnetic vortex, a gyrotropic mode, is directly observed in real time and space. The observed eigenfrequencies of the vortex mode as a function of disk size are in a good agreement with micromagnetic simulations. They also fall close to the predictions of a theory in which the magnetization of the displaced vortex is assumed to deform so that there are no magnetostatic charges at the edge of the disk. It is also observed that the vortex-mode eigenfrequency is nearly independent of the in-plane applied field. Azimuthal spin-wave modes, standing waves along the azimuthal direction in the vortex state, are investigated by exciting the spin system using an in-plane magnetic field pulse. Due to the cylindrical symmetry of the vortex state in remanence, two azimuthal modes propagating along opposite directions with the same number of azimuthal nodes are expected to be degenerate. However, our experimental results clearly demonstrate that the relative phase of the two azimuthal modes is determined by the polarity of the vortex core, and the magnitude of the splitting is of the same order as the vortex gyrotropic frequency. The broken degeneracy of the azimuthal spin-wave modes reveals how low-frequency excitations associated with domain structure influence spin-wave dynamics.

Park, Jooho

255

Towards a string formulation of vortex dynamics  

SciTech Connect

We derive an exact equation of motion for a non-relativistic vortex in two- and three-dimensional models with a complex field. The velocity is given in terms of gradients of the complex field at the vortex position. We discuss the problem of reducing the field dynamics to a closed dynamical system with non-locally interacting strings as the fundamental degrees of freedom.

Elsebeth Schroeder [Bayreuth Univ. (Germany). Physics Inst.; Ola Toernkvist

1998-01-01

256

Decoherence in Josephson vortex quantum bits  

Microsoft Academic Search

We investigate decoherence of a Josephson vortex quantum bit (qubit) in a dissipative and noisy environment. We use the perturbed sine-Gordon equation to describe the two-state system as the Josephson vortex qubit (JVQ) is fabricated by using a long Josephson junction. We compute the coherence time T2 by estimating the effects of quasiparticle dissipation and weakly fluctuating bias currents on

Ju H. Kim; Ramesh P. Dhungana; Kee-Su Park

2007-01-01

257

Production and application of electron vortex beams.  

PubMed

Vortex beams (also known as beams with a phase singularity) consist of spiralling wavefronts that give rise to angular momentum around the propagation direction. Vortex photon beams are widely used in applications such as optical tweezers to manipulate micrometre-sized particles and in micro-motors to provide angular momentum, improving channel capacity in optical and radio-wave information transfer, astrophysics and so on. Very recently, an experimental realization of vortex beams formed of electrons was demonstrated. Here we describe the creation of vortex electron beams, making use of a versatile holographic reconstruction technique in a transmission electron microscope. This technique is a reproducible method of creating vortex electron beams in a conventional electron microscope. We demonstrate how they may be used in electron energy-loss spectroscopy to detect the magnetic state of materials and describe their properties. Our results show that electron vortex beams hold promise for new applications, in particular for analysing and manipulating nanomaterials, and can be easily produced. PMID:20844532

Verbeeck, J; Tian, H; Schattschneider, P

2010-09-16

258

Vortex phases in type-I superconductors  

NASA Astrophysics Data System (ADS)

Sufficiently thin films of type-I superconductor in a perpendicular magnetic field exhibit a triangular vortex lattice, while thick films develop an intermediate state. To elucidate what happens between these two regimes, precise numerical calculations have been made within Ginzburg-Landau theory at kappa =0.5 and 0.25 for a variety of vortex lattice structures with one flux quantum per unit cell. The phase diagram in the space of mean induction and film thickness includes a narrow wedge in which a square lattice is stable, surrounded by the domain of stability of the triangular lattice at thinner films/lower fields and, on the other side, rectangular lattices with continuously varying aspect ratio. The vortex lattice has an anomalously small shear modulus within and close to the square lattice phase. Solutions of the Ginzburg-Landau equations have also been obtained for bulk systems and thin films for vortex lattices with one vortex but two flux quanta per square or triangular unit cell. These lattices of double fluxoid vortices are thermodynamically unstable in bulk in both type-I and type-II superconductors, as expected. In type-I films the situation is less clear, because the corresponding calculations for more complicated vortex lattice structures are not yet possible.

Sweeney, Mark

259

Vortex Methods with Spatially Varying Cores  

NASA Astrophysics Data System (ADS)

The accuracy of vortex methods employing smooth vortex particles/blobs is determined by the blob size, which can be viewed as a mollifier of the vorticity field. For computational efficiency, this core size needs to be spatially variable as particles are used to discretize different parts of the flow field, such as the boundary layer and the wake in bluff body flows. We derive here a consistent approximation for the viscous Navier-Stokes equations using variable size vortex particles. This derivation is based on the implementation of mappings that allow the consistent formulation of the diffusion and convection operators of the Navier-Stokes equations in the context of vortex methods. Several local mappings can be combined giving the capability of ``mesh-embedding'' to vortex methods. It is shown that the proposed variable method offers a significant improvement on the computational efficiency of constant core size methods while maintaining the adaptive character of the method. The method is ideally suited to flows such as wakes and shear layers and the validity of the approach is illustrated by showing results from cylinder flows and wall-vortex interactions. Using this scheme, previously unattainable simulations of cylinders undergoing rotary oscillations at high Reynolds numbers reveal an interesting mechanism for drastic drag reduction.

Cottet, Georges-Henri; Koumoutsakos, Petros; Salihi, Mohamed Lemine Ould

2000-07-01

260

Vortex-state oscillations in soft magnetic cylindrical dots  

NASA Astrophysics Data System (ADS)

We have studied magnetic vortex oscillations in soft submicron cylindrical dots with variable thickness and diameter by an analytical approach and micromagnetic simulations. We have considered two kinds of modes of the vortex magnetization oscillations: (1) low-frequency translation mode, corresponding to the movement of the vortex as a whole near its equilibrium position and (2) high-frequency vortex modes, which correspond to radially symmetric oscillations of the vortex magnetization, mainly outside the vortex core. The vortex translational eigenmode was calculated numerically in frequency and time domains for different dot aspect ratios. To describe the discrete set of vortex high-frequency modes we applied the linearized equation of motion of dynamic magnetization over the vortex ground state. We considered only radially symmetric magnetization oscillations modes. The eigenfrequencies of both kinds of the excitation modes are determined by magnetostatic interactions. They are proportional to the thickness/diameter ratio and lie in the GHz range for typical dot sizes.

Guslienko, K. Yu.; Scholz, W.; Chantrell, R. W.; Novosad, V.

2005-04-01

261

Effects of vortex packet interactions on turbulence structure  

NASA Astrophysics Data System (ADS)

DNS of channel flow at Reynolds numbers of 150, 300 and 590, based on half channel height and the wall friction velocity, has substantiated that hairpin vortex packets densely populate wall turbulence and constitute a commonly recurring structure. The hairpins are typically asymmetric, leading to much more complicated packet structures than a symmetric hairpin vortex train. Interactions of vortex packets with each other and with the turbulent flow are inevitable and complex. They result in first order changes in the vortex packets themselves, e.g., vortex annihilation and generation of new vortices. Vortex packets evolved from a single hairpin vortex increase Reynolds stresses due to coherence of vortices in the packet, while the interactions between vortex packets can produce an even bigger increase. The spanwise interactions increase Reynolds stress and change structure more than streamwise interactions. Both types of interactions generate a new vortex structure of larger scale than the parents.

Liu, Zichao; Adrian, Ronold J.

2000-11-01

262

Summary of NASA-Lewis Research Center solar heating and cooling and wind energy programs  

Microsoft Academic Search

NASA is planning to construct and operate a solar heating and cooling system in conjunction with a new office building being constructed at Langley Research Center. The technology support for this project will be provided by a solar energy program underway at NASA's Lewis Research Center. The solar program at Lewis includes: testing of solar collectors with a solar simulator,

R. W. Vernon

1975-01-01

263

Vortex Motion Near a Heating Sphere--Reynolds Analogy Revisited  

NASA Astrophysics Data System (ADS)

Recently, it was reported [M. Masoudi, W.A. Sirignano, Intl. J. Heat mass Transfer, 1997] that when sphere heating in a uniform flow is perturbed by vortex motion, global self-similarity is observed and the resulting correlation predicts that sphere Nusselt number fluctuations due to vortex motion scale with the vortex circulation with unity exponent: Nu' ~ ?0 / 2 ? , (Nu' = perturbations in sphere Nusselt number due to vortex motion, ?0 = non-dimensional initial vortex circulation). It will be shown that Reynolds Analogy confirms this worthwhile computational observation and also unveils the reason for the unity exponent of vortex circulation.

Masoudi, Mansour

1999-11-01

264

Three-vortex configurations in trapped Bose-Einstein condensates  

SciTech Connect

We report on the creation of three-vortex clusters in a {sup 87}Rb Bose-Einstein condensate by oscillatory excitation of the condensate. This procedure can create vortices of both circulations, so that we are able to create several types of vortex clusters using the same mechanism. The three-vortex configurations are dominated by two types, namely, an equilateral-triangle arrangement and a linear arrangement. We interpret these most stable configurations respectively as three vortices with the same circulation and as a vortex-antivortex-vortex cluster. The linear configurations are very likely experimental signatures of predicted stationary vortex clusters.

Seman, J. A.; Henn, E. A. L.; Shiozaki, R. F.; Ramos, E. R. F.; Caracanhas, M.; Castilho, P.; Castelo Branco, C.; Tavares, P. E. S.; Poveda-Cuevas, F. J.; Magalhaes, K. M. F.; Bagnato, V. S. [Instituto de Fisica de Sao Carlos, USP, Caixa Postal 369, 13560-970 Sao Carlos, Sao Paulo (Brazil); Haque, M. [Max Planck Institute for Physics of Complex Systems Noethnitzer Strasse 38, D-01187 Dresden (Germany); Roati, G. [LENS and Dipartimento di Fisica, Universita di Firenze, and INO-CNR, Via Nello Carrara 1, I-50019 Sesto Fiorentino (Italy)

2010-09-15

265

Vortex Ring Properties Before and After Interaction with a Screen  

NASA Astrophysics Data System (ADS)

The interaction of a vortex ring with a screen was investigated using Molecular Tagging Velocimetry (MTV). The screen had a porosity of 65% and a small wire diameter (Dw=0.0178 cm) with respect to the vortex ring diameter (Dw/ Dring=5.23x10-3). The results show that as the vortex ring approached the screen the initial interaction was much like that for a vortex ring/solid wall interaction. Specifically, the vortex ring slowed down and expanded as it approached the screen. A secondary vortex was formed that separated from the wall and orbited the primary vortex. Because the wall was porous the primary vortex ring passed through the wall, however, the secondary ring slowly convected back upstream. Data showed that the peak vorticity of the primary vortex dropped by nearly a factor of 4 after passing through while the radius increased in size only slightly (15%). The circulation of the primary vortex before and after the interaction decreased by more than a factor of 2 confirming conclusions from prior flow visualization results. The secondary vortex was both smaller and weaker than the primary vortex as is observed for vortex/wall interactions.

Hrynuk, John; Bohl, Douglas

2011-11-01

266

Vortex dynamics in superconducting MgB2 and prospects for applications.  

PubMed

The recently discovered superconductor magnesium diboride, MgB2, has a transition temperature, Tc, approaching 40 K, placing it intermediate between the families of low- and high-temperature superconductors. In practical applications, superconductors are permeated by quantized vortices of magnetic flux. When a supercurrent flows, there is dissipation of energy unless these vortices are 'pinned' in some way, and so inhibited from moving under the influence of the Lorentz force. Such vortex motion ultimately determines the critical current density, Jc, which the superconductor can support. Vortex behaviour has proved to be more complicated in high-temperature superconductors than in low-temperature superconductors and, although this has stimulated extensive theoretical and experimental research, it has also impeded applications. Here we describe the vortex behaviour in MgB2, as reflected in Jc and in the vortex creep rate, S, the latter being a measure of how fast the 'persistent' supercurrents decay. Our results show that naturally occurring grain boundaries are highly transparent to supercurrents, a desirable property which contrasts with the behaviour of the high-temperature superconductors. On the other hand, we observe a steep, practically deleterious decline in Jc with increasing magnetic field, which is likely to reflect the high degree of crystalline perfection in our samples, and hence a low vortex pinning energy. PMID:11279489

Bugoslavsky, Y; Perkins, G K; Qi, X; Cohen, L F; Caplin, A D

2001-03-29

267

Heat Transfer Enhancement in Separated and Vortex Flows  

SciTech Connect

This document summarizes the research performance done at the Heat Transfer Laboratory of the University of Minnesota on heat transfer and energy separation in separated and vortex flow supported by DOE in the period September 1, 1998--August 31, 2003. Unsteady and complicated flow structures in separated or vortex flows are the main reason for a poor understanding of heat transfer under such conditions. The research from the University of Minnesota focused on the following important aspects of understanding such flows: (1) Heat/mass transfer from a circular cylinder; (2) study of energy separation and heat transfer in free jet flows and shear layers; and (3) study of energy separation on the surface and in the wake of a cylinder in crossflow. The current study used three different experimental setups to accomplish these goals. A wind tunnel and a liquid tunnel using water and mixtures of ethylene glycol and water, is used for the study of prandtl number effect with uniform heat flux from the circular cylinder. A high velocity air jet is used to study energy separation in free jets. A high speed wind tunnel, same as used for the first part, is utilized for energy separation effects on the surface and in the wake of the circular cylinder. The final outcome of this study is a substantial advancement in this research area.

Richard J. Goldstein

2004-05-27

268

Reduction of dust entrainment in pneumatic dryers of the spiral-vortex type  

Microsoft Academic Search

A number of modifications to pneumatic dryers of the spiral and vortex types have been developed by the Moscow Institute for Chemical Equipment Construction (MIKhM) and the Scientific-Research Institute for Polymers (NIIpolimerov). A common feature of these modifications is the presence of a drying channel which is bent into the form of an Archimedean spiral over its length and which

V. S. Konovalov; E. L. Foteeva; V. M. Ul'yanov

1993-01-01

269

A Comparison of Wake-Vortex Models for Use in Probabilistic Aviation Safety Analysis  

Microsoft Academic Search

The goal of this paper is to address part of a larger safety issue in aviation: What is the probability that a landing aircraft flies through a wake vortex generated by the aircraft in front of it and subsequently crashes? An important element needed to address this overall research question is a model to predict the evolution of wake vortices

J. F. Shortle

270

Numerical analysis of slender vortex motion  

SciTech Connect

Several numerical methods for slender vortex motion (the local induction equation, the Klein-Majda equation, and the Klein-Knio equation) are compared on the specific example of sideband instability of Kelvin waves on a vortex. Numerical experiments on this model problem indicate that all these methods yield qualitatively similar behavior, and this behavior is different from the behavior of a non-slender vortex with variable cross-section. It is found that the boundaries between stable, recurrent, and chaotic regimes in the parameter space of the model problem depend on the method used. The boundaries of these domains in the parameter space for the Klein-Majda equation and for the Klein-Knio equation are closely related to the core size. When the core size is large enough, the Klein-Majda equation always exhibits stable solutions for our model problem. Various conclusions are drawn; in particular, the behavior of turbulent vortices cannot be captured by these local approximations, and probably cannot be captured by any slender vortex model with constant vortex cross-section. Speculations about the differences between classical and superfluid hydrodynamics are also offered.

Zhou, H.

1996-02-01

271

Quantum dynamics of a single vortex.  

PubMed

Vortices occur naturally in a wide range of gases and fluids, from macroscopic to microscopic scales. In Bose-Einstein condensates of dilute atomic gases, superfluid helium and superconductors, the existence of vortices is a consequence of the quantum nature of the system. Quantized vortices of supercurrent are generated by magnetic flux penetrating the material, and play a key role in determining the material properties and the performance of superconductor-based devices. At high temperatures the dynamics of such vortices are essentially classical, while at low temperatures previous experiments have suggested collective quantum dynamics. However, the question of whether vortex tunnelling occurs at low temperatures has been addressed only for large collections of vortices. Here we study the quantum dynamics of an individual vortex in a superconducting Josephson junction. By measuring the statistics of the vortex escape from a controllable pinning potential, we demonstrate the existence of quantized levels of the vortex energy within the trapping potential well and quantum tunnelling of the vortex through the pinning barrier. PMID:12968173

Wallraff, A; Lukashenko, A; Lisenfeld, J; Kemp, A; Fistul, M V; Koval, Y; Ustinov, A V

2003-09-11

272

Spin Dynamics in Magnetic Vortex Structures  

NASA Astrophysics Data System (ADS)

We have studied the spin dynamics of individual permalloy disks with thicknesses of 50 nm and diameters from 200 nm to 2 ? m using time-resolved Kerr microscopy. Magnetic fields up to 800 ˜ Oe are applied in the plane of the disks, for which the micromagnetic configuration in small fields is a vortex. We observe three distinct spin-wave modes in the vortex state: a gyrotropic mode at low frequency (< 1 GHz) that is due to the translational degree of freedom of the vortex core, as well as two spin-wave modes of predominantly magnetostatic character at higher frequencies (> 4 GHz). The frequency of the gyrotropic mode increases with decreasing disk diameter as predicted from the vortex equation of motion as well as micromagnetic simulations. The gyrotropic frequency is independent of the applied field, or, equivalently, of the position of the vortex core inside the disk. Of the upper pair of modes, the lower frequency excitation has an effective wave vector parallel to the edges of the disk and a line of nodes along the diameter. In the saturated state, an ordinary FMR mode is observed in disks with diameters larger than 1 ? m , and this splits into several modes as the diameter decreases. This work was supported by NSF DMR 99-83777, the University of Minnesota MRSEC (NSF DMR-0212032), and the Minnesota Supercomputing Institute.

Park, J. P.; Eames, P.; Crowell, P. A.

2004-03-01

273

Vortex Breakdown in Atmospheric Columnar Vortices.  

NASA Astrophysics Data System (ADS)

Vortex breakdown occurs in tornadoes and waterspouts. This phenomenon may give information on the state and future behavior of those whirlwinds. Because of the rarity of recorded events, archival sources are consulted for qualitative descriptions from earlier times and compared with contemporary sources. Drawings and eyewitness reports from earlier times, rare photographs, movies, and observations from recent years indicate the occurrence of vortex breakdown in tornadoes and waterspouts near the ground, in the midsection of the funnel, and close to or inside the parent cloud. Since the contour of the whirlwind's funnel is delineated only by markers in the form of condensates, dust, or other debris, these markers may distort or obscure the evidence of vortex breakdown. This is a likely reason for the rare observation and identification of vortex breakdown which might be more common in whirlwinds than has been previously thought. According to the records examined, meteorologists deserve the honor for discovering and describing vortex breakdown long before the systematic investigation of recent years.

Lugt, H. J.

1989-12-01

274

Vortex shedding from edges including viscous effects  

NASA Astrophysics Data System (ADS)

This paper describes results obtained by using the inviscid Cloud-in-Cell vortex method to model the vortex sheet which is shed and rolls up from a single sharp edge. There is good agreement between these results and previous (Pullin 1978) computations of the development of the sheet in impulsively started incompressible inviscid flow. The Cloud-in-Cell method has been modified to include viscous diffusion calculated by finite differences on the mesh to give a mixed Eulerian-Lagrangian Navier-Stokes solver. This method has been shown to model the diffusing free vortex and the Stokes boundary layer quite accurately. It is used to compute impulsively started flow past sharp right-angled edges and edges with small rounding. The effect of viscous diffusion on the development of the shed vortex is discussed. The method is also used to study the effect of rounding on the vortex shedding from a right-angled edge in oscillatory flow. This problem is particularly important in determining the roll damping and hence response of certain types of ship hull in waves. It is shown that the strength and effect of the shed vortices rapidly decrease as the ratio of the edge radius to the oscillation amplitude increases, and that at larger values of this ratio the mode of shedding changes from two vortices per cycle from one edge to a more complicated mode. The computed results are compared with flow visualisation using dye and neutrally buoyant particles in water flow around an oscillating edge.

Graham, J. M. R.; Cozens, P. D.

1988-09-01

275

Dynamic Control of Collapse in a Vortex Airy Beam  

PubMed Central

Here we study systematically the self-focusing dynamics and collapse of vortex Airy optical beams in a Kerr medium. The collapse is suppressed compared to a non-vortex Airy beam in a Kerr medium due to the existence of vortex fields. The locations of collapse depend sensitively on the initial power, vortex order, and modulation parameters. The collapse may occur in a position where the initial field is nearly zero, while no collapse appears in the region where the initial field is mainly distributed. Compared with a non-vortex Airy beam, the collapse of a vortex Airy beam can occur at a position away from the area of the initial field distribution. Our study shows the possibility of controlling and manipulating the collapse, especially the precise position of collapse, by purposely choosing appropriate initial power, vortex order or modulation parameters of a vortex Airy beam.

Chen, Rui-Pin; Chew, Khian-Hooi; He, Sailing

2013-01-01

276

Flow past Bluff Bodies by a Vortex Method.  

National Technical Information Service (NTIS)

A review of the literature on vortex methods for the representation of vortex sheets and the literature in two dimensional viscous incompressible flow past bluff bodies, mainly the circular cylinder, both experimental and numerical, with emphasis on the u...

A. P. Burrows

1990-01-01

277

Vortex solitons in defocusing media with spatially inhomogeneous nonlinearity.  

PubMed

The analytical two- and three-dimensional vortex solitons with arbitrary values of vorticity are constructed in the cubic defocusing media with spatially inhomogeneous nonlinearity. The values of the nonlinearity coefficients are zero near the center and increase rapidly toward the periphery. In addition to the analytical ones, a number of vortex solitons are found numerically. It is shown that analytical vortex solitons are stable. Also, the stability region of the numerically constructed vortex solitons are given. PMID:23004891

Tian, Qing; Wu, Lei; Zhang, Yonghao; Zhang, Jie-Fang

2012-05-11

278

Vortex pinning in layered superconductors: strong pinning and electromagnetic interactions  

Microsoft Academic Search

We study the pinning of vortices in layered type-II superconductors in the presence of uncorrelated quenched disorder, accounting for the electromagnetic interactions in the vortex system. Using collective pinning theory and introducing the new concept of variable-range thermal smoothing of the pinning potential, we map out the pinning diagram and find the regimes of single-pancake-vortex (0D), single-vortex (1D), pancake-vortex-bundle (2D)

Orlando S. Wagner; Guido Burkhard; Vadim B. Geshkenbein; Gianni Blatter

1998-01-01

279

Tip vortex cavitation suppression by water ejection from wing tip  

NASA Astrophysics Data System (ADS)

In the present study we investigated how a water jet, used to create a winglet-like effect, actively reduces or suppress the cavitation formed into the core of a tip vortex. Modifications of the vortex structure were monitored by measuring the velocity profiles with laser Doppler velocimetry. High-speed jets proved to be very effective in increasing the size of the vortex core, thus inhibiting the formation of tip vortex cavitation.

Farhat, Mohamed; Reclari, Martino

2010-11-01

280

Application of Piloted Simulation to High-Angle-of-Attack Flight-Dynamics Research for Fighter Aircraft.  

National Technical Information Service (NTIS)

This paper reviews the use of piloted simulation at Langley Research Center as part of the NASA High-Angle-of-Attack Technology Program (HATP), which was created to provide concepts and methods for the design of advanced fighter aircraft. A major research...

M. E. Ogburn J. V. Foster K. D. Hoffler

2005-01-01

281

Vortex generation in oscillatory canopy flow  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate for the first time the generation of coherent vortices at the top of a canopy in oscillatory (i.e., wave-dominated) flow. Through a series of flow visualization experiments, vortex formation is shown to occur when two conditions described by the Keulegan-Carpenter (KC) and Reynolds (Re) numbers are met. First, the wave period must be sufficiently long to allow the generation of the shear-driven instability at the top of the canopy; this occurs when KC ? 5. Second, the vortex instability must be able to overcome the stabilizing effects of viscosity; this occurs when Re ? 1000. The vortices greatly increase the rate of vertical mixing within the canopy, such that any prediction of residence time in a coastal canopy requires an understanding of whether vortex generation is occurring.

Ghisalberti, Marco; Schlosser, Tamara

2013-03-01

282

Thermal crisis of a vortex source  

NASA Astrophysics Data System (ADS)

The effect of circulation in the field of a bulk vortex source on thermal crisis (flow choking induced by energy supply in a layer in accordance with a known law) is studied. Substantial changes in the value of energy supply parameter and slight variations in the coordinate of the critical cross section in which the velocity of sound is attained are revealed, and the dependence of these parameters on the location and width of the heat-supply region is noted. The possibility of transition to a supersonic flow when the heat release region is near the minimal cross section of the vortex source is analyzed. The difference between the cases of polyatomic and monatomic gases is demonstrated. Distinguishing features of the vortex sink are considered.

Kucherov, A. N.

2011-07-01

283

Sphagnum moss disperses spores with vortex rings.  

PubMed

Sphagnum spores, which have low terminal velocities, are carried by turbulent wind currents to establish colonies many kilometers away. However, spores that are easily kept aloft are also rapidly decelerated in still air; thus, dispersal range depends strongly on release height. Vascular plants grow tall to lift spores into sufficient wind currents for dispersal, but nonvascular plants such as Sphagnum cannot grow sufficiently high. High-speed videos show that exploding capsules of Sphagnum generate vortex rings to efficiently carry spores high enough to be dispersed by turbulent air currents. Spores launched ballistically at similar speeds through still air would travel a few millimeters and not easily reach turbulent air. Vortex rings are used by animals; here, we report vortex rings generated by plants. PMID:20651145

Whitaker, Dwight L; Edwards, Joan

2010-07-23

284

Mechanical study on vortex entanglement in melt-textured YBCO  

Microsoft Academic Search

The mechanical dissipation was measured using a vibrating-reed technique in various magnetic fields on melt-textured YBa2Cu3O7?? (YBCO) sample. The crossover from vortex entanglement to vortex disentanglement was observed in the high temperature side of the dissipation peak due to vortex motion. The effect of entangled length on the crossover temperature was also discussed.

Z. Li; J. S. Zhu; X. B. Wu; C. B. Cai; H. Zhang; Y. N. Wang

2000-01-01

285

Mechanical study on vortex entanglement in melt-textured YBCO  

Microsoft Academic Search

The mechanical dissipation was measured using a vibrating-reed technique in various magnetic fields on melt-textured YBa2Cu3O7-delta (YBCO) sample. The crossover from vortex entanglement to vortex disentanglement was observed in the high temperature side of the dissipation peak due to vortex motion. The effect of entangled length on the crossover temperature was also discussed.

Z. Li; J. S. Zhu; X. B. Wu; C. B. Cai; H. Zhang; Y. N. Wang

2000-01-01

286

Direct Observation of Internal Spin Structure of Magnetic Vortex Cores  

Microsoft Academic Search

Thin film nanoscale elements with a curling magnetic structure (vortex) are a promising candidate for future nonvolatile data storage devices. Their properties are strongly influenced by the spin structure in the vortex core. We have used spin-polarized scanning tunneling microscopy on nanoscale iron islands to probe for the first time the internal spin structure of magnetic vortex cores. Using tips

A. Wachowiak; J. Wiebe; M. Bode; O. Pietzsch; M. Morgenstern; R. Wiesendanger

2002-01-01

287

Slowing down of vortex rings in Bose-Einstein condensates  

SciTech Connect

We consider vortex rings moving in a Bose-Einstein condensate. By numerically solving the Gross-Pitaevskii equation, we show that if the circular shape of the ring is perturbed by helical Kelvin waves of given amplitude and azimuthal wave number, the translational self-induced velocity of the vortex ring is reduced; at large amplitude, the vortex ring halts.

Helm, John L.; Barenghi, Carlo F.; Youd, Anthony J. [School of Mathematics and Statistics, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom)

2011-04-15

288

Hot-wire and vorticity meter wake vortex surveys  

Microsoft Academic Search

The vorticity meter used in the experiments consists of a paddle-wheel sensor mounted on a rotating shaft and fitted with a jeweled bearing. Vorticity data for a trailing vortex obtained with the vorticity meter are presented in a graph, taking into account an injected and a basic vortex. The tangential and axial velocity profile of a trailing vortex, as determined

A. D. Zalay

1976-01-01

289

Thermal and power characteristics of plasma torch with reverse vortex  

NASA Astrophysics Data System (ADS)

The results of experimental investigations of electrical and thermal characteristics of a vortex plasma torch with a reverse vortex, generated in a hollow blind-end electrode, are presented. It is shown that the reverse vortex essentially improves the performance of the plasma torch and contributes to an increase in the thermal efficiency and enthalpy of the plasma jet.

Essiptchouk, A. M.; Charakhovski, L. I.; Filho, G. P.; Maciel, H. S.; Otani, Ch; Barros, E. A.

2009-09-01

290

Thermal and power characteristics of plasma torch with reverse vortex  

Microsoft Academic Search

The results of experimental investigations of electrical and thermal characteristics of a vortex plasma torch with a reverse vortex, generated in a hollow blind-end electrode, are presented. It is shown that the reverse vortex essentially improves the performance of the plasma torch and contributes to an increase in the thermal efficiency and enthalpy of the plasma jet.

A. M. Essiptchouk; L. I. Charakhovski; G. P. Filho; H. S. Maciel; Ch Otani; E. A. Barros

2009-01-01

291

Vortex Sheet Model for a Turbulent Mixing Layer  

NASA Astrophysics Data System (ADS)

The primary aim of this work is to study instability induced roll up of a slightly perturbed vortex sheet in an Euler fluid. A point vortex model tends to evolve into a chaotic cloud of point vortices instead of smooth double branched spirals. The present model uses linear splines to interpolate the vortex sheet. Computer simulation of this vortex sheet is numerically prohibitive. However, the evolution of the vortex sheet can be performed conveniently using a closed form equation of motion which derived from the basic equations of vortex dynamics. The vortex sheet rolls up into a smooth double branched spiral. A vortex core is formed by regular windings of the vortex sheet and irrotational fluid in between the layers. Various statistical quantities like the growth rate and mean velocity profiles are computed along with the evolution of the vortex sheet. The problem of spontaneous appearance of singularity in an evolving vortex sheet is treated in detail. The critical time for the present vortex sheet model is calculated analytically and compared to the numerical value.

Paul, Ujjayan; Narasimha, Roddam; Alam, Meheboob

2011-03-01

292

Response of a vortex flowmeter to impulsive vibrations  

Microsoft Academic Search

Experiments were performed to study the response of a vortex flowmeter to structural vibrations due to impulsive forces applied on the pipe. Vortex-shedding signals obtained by a piezoelectric sensor embedded in a vortex shedder were examined. Major findings are described as follows. First, by improving the design of the piezoelectric sensor, the sensor sensitivity to structural vibrations could be reduced.

J. J Miau; C. C Hu; J. H Chou

2000-01-01

293

Dynamics of a pinned magnetic vortex  

NASA Astrophysics Data System (ADS)

Disks patterned from soft ferromagnetic films typically form a single magnetic vortex for diameters on the order of a few microns or less. The vortex dynamics include both ordinary spin waves and a gyrotropic mode, in which the vortex core undergoes circular motion about its equilibrium position [1, 2]. This mode has sub-GHz frequencies which ideally depend only on the aspect ratio (diameter over thickness) of the disk [2, 3]. We have used time-resolved Kerr microscopy to investigate the gyrotropic mode as a function of the equilibrium position of the core, which can be tuned by an applied field with a sensitivity of ˜1 nm/Oe. In the limit of high excitation amplitude, the gyrotropic frequency fG is independent of the vortex core position, as previously predicted and observed [1, 3]. For small amplitudes, however, we observe unexpected fluctuations in fG as a function of the applied field. The average core displacement between consecutive frequency peaks, as well as the average frequency shift, is observed to be independent of disk diameter. These observations indicate that the fluctuations are due to a distribution of nanoscale defects that pin the vortex core by lowering its energy [4]. Furthermore, they are consistent with a model in which the frequency shift for a particular fluctuation is a direct measure of the interaction energy of the vortex core with one defect. By mapping fG as a function of orthogonal in-plane static fields, we image the 2D spatial distribution of defects with nanoscale resolution. [1] K. Yu Guslienko et.al., JAP 91, 8037 (2002). [2] J. Park et.al., PRB 67, 020403(R) (2003). [3] V. Novosad et.al., PRB 72, 024455 (2005). [4] R. L. Compton and P. A. Crowell, PRL 97, 137202 (2006).

Compton, Robert

2008-03-01

294

Flow field measurements of leading-edge separation vortex formed on a delta wing with vortex flaps  

Microsoft Academic Search

Wind tunnel tests are carried out using a 70 delta wing model with leading-edge vortex flaps. The structure of the leading-edge\\u000a separation vortex over the leading-edge vortex flap is measured by use of a 5 holes pitot probe, surface pressure measurement\\u000a technique and oil flow visualization technique. Separation vortices formed on a plain delta wing, on a vortex flap and

K. Rinoie

2001-01-01

295

Numerical Validation of Quasigeostrophic Ellipsoidal Vortex Model  

NASA Astrophysics Data System (ADS)

In geophysical flows, coherent vortex structures persist for long time and their interactions dominate the dynamics of geophysical turbulence. Meacham et al.1,2) obtained a series of exact unsteady solution of the quasigeostrophic equation, which represents a uniform ellipsoidal vortex patch embedded in a uniform 3D shear field. Miyazaki et al.3,4) have derived a Hamiltonian dynamical system of 3N degrees of freedom, describing the interactions of N ellipsoidal vortices, where each coherent vortex was modeled by an ellipsoid of uniform potential vorticity. The center of vorticity and the angular momentum are conserved, besides the total energy and Casimirs of the system, such as the vortex height and the vortex volume. There are three Poisson-commutable invariants, which is less than the degree of freedom for N>=2, and chaotic motions are observed even in a two-body system. In this paper, direct numerical simulations based on a Contour Advective Semi-Lagrangian algorithm (CASL) are performed in order to assess the validity of the Hamiltonian model. First, the instability of a tilted spheroid is investigated. A prolate spheroid becomes unstable against the third Legendre mode when the aspect ratio is less than 0.44 and the inclination angle is larger than 0.48.5) Weakly unstable flatter spheroidal vortices emit thin filaments from their top and bottom, whereas strongly unstable slender spheroidal vortices are broken up into two pieces. Secondly, the interaction of two co-rotating spheroidal vortices on slightly different vertical levels, which plays a key role in the turbulence dynamics, is studied in detail. The Hamiltonian model can predict the critical distance of symmetric mergers very well, except for mergers of vortices on the same horizontal plane. The model gives poorer predictions in asymmetric cases, where vorticity exchange occurs (instead of merger) along the threshold determined by the Hamiltonian model. The slenderer vortex loses half of its original volume, and the flatter vortex expands slightly absorbing some of the filaments ejected from the slenderer vortex. This is a new dynamical process linked with the energy and enstrophy cascades. Considerable amounts of energy and enstrophy are dissipated in these events. The correlation between the energy dissipation and the enstrophy dissipation is good, suggesting the existence of a simple deterministic reset-rule. 1)S. P. Meacham, et al.: Dyn. Atmos. Oceans 21 (1994) 167. 2)S. P. Meacham, et al: Phys. Fluids 9 (1997) 2310. 3)T. Miyazaki, et al.: J. Phys. Soc. Jpn. 69 (2000) 3233. 4)T. Miyazaki, et al.: J. Phys. Soc. Jpn. 70 (2001) 1942. 5)T. Miyazaki, et al.: J. Phys. Soc. Jpn. 68 (1999) 2592.

Miyazaki, T.; Fujishima, S.

2002-05-01

296

Direct generation of optical vortex pulses  

NASA Astrophysics Data System (ADS)

We demonstrate the direct generation of optical vortex pulses with stable energy and changeable orbital angular momentum. Single Laguerre-Gaussian (LG0,l) laser modes were directly generated using a laser diode with output intensity profile of doughnut distribution. With passive Q-switching, vortex pulses with stable energy were obtained. Moreover, the topological charge was changeable by variation of the pump power. By a mode-converter and second harmonic generation, the LG0,2l mode was identified. It can be proposed that this pulsed laser should have promising applications in various fields based on its compact structure, stable and high pulse energy, and changeable orbital angular momentum.

Zhao, Yongguang; Wang, Zhengping; Yu, Haohai; Zhuang, Shidong; Zhang, Huaijin; Xu, Xiaodong; Xu, Jun; Xu, Xinguang; Wang, Jiyang

2012-07-01

297

Spherical Shell Vortex Model For Compound Drops  

NASA Astrophysics Data System (ADS)

A new generalization of the classical solution for inviscid incompressible flow with vorticity known as Hill's spherical vortex is presented here. The new solution includes a concentric sphere inside the spherical body produced by Hill's vortex. The internal sphere can be filled with a different fluid,with limiting cases of a spherical cavity, or solid sphere. This solution is applicable to coated pill and pellet manfacture.The present solution also includes internal swirling about the axis parallel to the direction of oncoming flow.

Shusser, Michael; Weihs, Daniel

2003-11-01

298

Effect of vortex flows on ammonia oxidation  

SciTech Connect

The oxidation of ammonia over platinum sieve catalysts was investigated given the vortex flows found in industrial contact units. Mathematical and physical models were used to assess the influence of vortices on ammonia oxidation. The flow pattern of the ammonia-air mixture in the reactor was modeled as a stream with a partial recycle. It is shown that vortex flows reduce the conversion of ammonia to nitrogen monoxide and increase the passage of unconverted ammonia through the catalyst sieve. Over long contact periods, the main effect of vortices is to increase the passage of unconverted ammonia, which may lead to the formation of explosive compounds.

Beskov, V.S.; Shpinel', E.E.

1988-09-01

299

Bluff Body Flow Simulation Using a Vortex Element Method  

SciTech Connect

Heavy ground vehicles, especially those involved in long-haul freight transportation, consume a significant part of our nation's energy supply. it is therefore of utmost importance to improve their efficiency, both to reduce emissions and to decrease reliance on imported oil. At highway speeds, more than half of the power consumed by a typical semi truck goes into overcoming aerodynamic drag, a fraction which increases with speed and crosswind. Thanks to better tools and increased awareness, recent years have seen substantial aerodynamic improvements by the truck industry, such as tractor/trailer height matching, radiator area reduction, and swept fairings. However, there remains substantial room for improvement as understanding of turbulent fluid dynamics grows. The group's research effort focused on vortex particle methods, a novel approach for computational fluid dynamics (CFD). Where common CFD methods solve or model the Navier-Stokes equations on a grid which stretches from the truck surface outward, vortex particle methods solve the vorticity equation on a Lagrangian basis of smooth particles and do not require a grid. They worked to advance the state of the art in vortex particle methods, improving their ability to handle the complicated, high Reynolds number flow around heavy vehicles. Specific challenges that they have addressed include finding strategies to accurate capture vorticity generation and resultant forces at the truck wall, handling the aerodynamics of spinning bodies such as tires, application of the method to the GTS model, computation time reduction through improved integration methods, a closest point transform for particle method in complex geometrics, and work on large eddy simulation (LES) turbulence modeling.

Anthony Leonard; Phillippe Chatelain; Michael Rebel

2004-09-30

300

Vortex focusing of ions produced in corona discharge.  

PubMed

Completeness of the ion transportation into an analytical path defines the efficiency of ionization analysis techniques. This is of particular importance for atmospheric pressure ionization sources like corona discharge, electrospray, ionization with radioactive ((3)H, (63)Ni) isotopes that produce nonuniform spatial distribution of sample ions. The available methods of sample ion focusing are either efficient at reduced pressure (~1Torr) or feature high sample losses. This paper deals with experimental research into atmospheric pressure focusing of unipolar (positive) ions using a highly swirled air stream with a well-defined vortex core. Effects of electrical fields from corona needle and inlet capillary of mass spectrometer on collection efficiency is considered. We used a corona discharge to produce an ionized unipolar sample. It is shown experimentally that with an electrical field barrier efficient transportation and focusing of an ionized sample are possible only when a metal plate restricting the stream and provided with an opening covered with a grid is used. This gives a five-fold increase of the transportation efficiency. It is shown that the electric field barrier in the vortex sampling region reduces the efficiency of remote ionized sample transportation two times. The difference in the efficiency of light ion focusing observed may be explained by a high mobility and a significant effect of the electric field barrier upon them. It is possible to conclude based on the experimental data that the presence of the field barrier narrows considerably (more than by one and half) the region of the vortex sample ion focusing. PMID:23618173

Kolomiets, Yuri N; Pervukhin, Viktor V

2013-02-14

301

Vortex Ring Extremization for Low Speed Maneuvering of Underwater Vehicles  

NASA Astrophysics Data System (ADS)

Most attempts in underwater locomotion have been focused on propeller thrust generation or recently on flapping locomotion. However, new developments in autonomous and tethered underwater vehicles motivated closer look at the biomimetics of sea animals. To this end, Cephalopoda and jelly fish utilize pulsatile jets and vortex formation for locomotion. To avoid further complications with background flows, we focus on the formation of the leading vortex ring rather than a train of vortices. It is shown that a pinched-off vortex ring characterizes the extremum impulse accumulated by the leading vortex ring in vortex formation process. An appropriate scaling for vortex ring impulse is found and the limiting values of the non-dimensionalized impulses are established. An estimate for the non-dimensional impulses is provided by equating their values from the slug model with their values from a vortex in the Norbury family of vortices. For a vortex ring generator with constant kinetic energy and circulation generation rate, the pinched-off vortex ring has a maximum impulse of I_nd^E ? 11 normalized by the circulation and energy. On the other hand, for a vortex ring generator with constant rate of circulation generation at a constant translational velocity, a pinched-off vortex ring produces a minimum impulse of I_nd^? ? 0.12 normalized by the circulation and translational velocity. Direct numerical simulations of vortex ring formation and vortex ring pinch-off process are performed and the estimated values of the non-dimensionalized impulses are confirmed. These ideas are employed in designing a vortex jet generator for low speed maneuvering of underwater robots. The presented vortex generators are simple and low cost, they consume little valuable payload space, and they have no moving external parts. Experimental data are presented in support of the optimal formation number of 4 for maximum thrust generation.

Mohseni, Kamran

2004-11-01

302

Vortex shedding in the wake of a step cylinder  

NASA Astrophysics Data System (ADS)

Flow past a circular cylinder with a single stepwise discontinuity in diameter was investigated numerically for the diameter ratio D/d=2 and two Reynolds numbers, ReD=150 and 300. The primary focus was on vortex shedding and vortex interactions occurring in the cylinder wake. In agreement with previous experimental findings, three distinct spanwise vortex cells were identified in the step-cylinder wake: a single vortex shedding cell in the wake of the small cylinder (the S-cell) and two vortex shedding cells in the wake of the large cylinder, one in the region downstream of the step (the N-cell) and the other away from the step (the L-cell). Due to the differences in vortex shedding frequencies, complex vortex connections occurred in two vortex interaction regions located between the adjacent cells. However, distinct differences in vortex splitting and vortex dislocations were identified in the two regions. The region at the boundary between the S-cell and the N-cell was relatively narrow and its spanwise extent did not fluctuate significantly. In this region, vortex dislocations manifested as half-loop connections between two S-cell vortices of opposite sign. In contrast, the region at the boundary between the N-cell and the L-cell exhibited transient behavior, with large scale vortex dislocations causing cyclic variation in the extent of N-cell vortices. Spectral analysis of velocity data showed that the presence of the N-cell was continuous through all simulations. For ReD=300, small scale streamwise vortices forming in the wake of the large cylinder weaken the primary spanwise vortices and vortex connections, complicating vortex dynamics in the step-cylinder wake. However, no significant Reynolds number effect on the average spanwise extent of the vortex cells and the two transition regions between neighboring cells was observed. Finally, formation of N-cell vortices was shown to be linked to downwash fluctuations near the step.

Morton, Chris; Yarusevych, Serhiy

2010-08-01

303

Use of Piloted Simulation for High-Angle-of-Attack Agility Research and Design Criteria Development.  

National Technical Information Service (NTIS)

This paper reviews the use of piloted simulation at Langley Research Center as part of the NASA High-Angle-of Attack Technology Program (HATP) to provide methods and concepts for the design of advanced fighter aircraft. A major focus of this program is to...

M. E. Ogburn J. V. Foster K. D. Hoffler

2004-01-01

304

Collaborations Focused on Enhancing Undergraduate Involvement in Remote Sensing Applications to Atmospheric and Earth Science Research  

Microsoft Academic Search

This paper discusses the mentoring strategies used with groups of undergraduate physics, mathematics and atmospheric science majors to develop their ability to contribute to remote sensing investigations. The projects have been a joint effort of scientists and educators at NASA Langley Research Center, Hampton University in Virginia, Elizabeth City State University in North Carolina, Stennis Space Center, and The Office

Linda Hayden; Ali H. Omar

2006-01-01

305

Vortex penetration depth of organic superconductors: Evidence for vortex lattice melting  

SciTech Connect

The authors observe a crossover field H* in the temperature and magnetic field dependence of the rf vortex penetration depth in {kappa}-(ET){sub 2}Cu[N(CN){sub 2}]Br for {rvec H}{sub dc}{parallel}{cflx b}-axis. They find that H* can be described quantitatively by the 3D Lindemann melting theory; thus, it corresponds to the melting of the vortex lattice in {kappa}-(ET){sub 2}Cu[N(CN){sub 2}]Br and lies very close to the irreversibility line. In the vortex-liquid state, they argue that the saturation of the vortex penetration depth in a magnetic field results from the finite size of the sample. The results do not have the scaling form predicted by the Coffey-Clem model in contrast to previous findings.

Tea, N.H.; Giannetta, R.W.; Salamon, M.B. [Univ. of Illinois, Urbana, IL (United States); Williams, J.M.; Wang, H.H.; Geiser, U. [Argonne National Lab., IL (United States). Chemistry and Materials Science Div.

1997-07-01

306

Vortex knots in a Bose-Einstein condensate.  

PubMed

We present a method for numerically building a vortex knot state in the superfluid wave function of a Bose-Einstein condensate. We integrate in time the governing Gross-Pitaevskii equation to determine evolution and shape preservation of the two (topologically) simplest vortex knots which can be wrapped over a torus. We find that the velocity of a vortex knot depends on the ratio of poloidal and toroidal radius: for smaller ratio, the knot travels faster. Finally, we show how vortex knots break up into vortex rings. PMID:22587179

Proment, Davide; Onorato, Miguel; Barenghi, Carlo F

2012-03-19

307

Vortex polarization dynamics in a square magnetic nanodot  

NASA Astrophysics Data System (ADS)

Langevin simulations at finite temperature of two-dimensional magnetic nanodots were performed using the Landau–Lifshitz equation with exchange and dipolar interactions. In a wide range of temperatures, the dynamics of square samples with one central vortex was studied, focusing on the out-of-plane magnetic component at the vortex-core. This vortex-core undergoes polarization sign reversals in a thermally activated process. In the intervals between polarization flips, the out-of-plane spin components at the vortex-core show oscillations with identifiable frequencies connected with certain eigenfrequencies of the system associated with polarity active modes. The vortex-core positions were also monitored.

Depondt, Ph; Lévy, J.-C. S.; Mamica, S.

2013-11-01

308

3D vortex formation of drag-based propulsors  

NASA Astrophysics Data System (ADS)

Three dimensional vortex formation mechanism of impulsively rotating plates is studied experimentally using defocusing digital particle image velocimetry. The plate face is normal to the moving direction to simulate drag-based propulsion and only one power stroke is considered. In order to compare the effect of shape on vortex generation, three different shapes of plate (rectangular, triangular and duck's webbed-foot shapes) are used. These three cases show striking differences in vortex formation process during power stroke. Axial flow is shown to play an important role in the tip vortex formation. Correlation between hydrodynamic forces acting on the plate and vortex formation processes is described.

Kim, Daegyoum; Gharib, Morteza

2008-11-01

309

Vortex pinning by quenched randomness in neutron stars  

NASA Astrophysics Data System (ADS)

Pulsar glitches are commonly attributed to the transfer of angular momentum from the superfluid to the solid crust. The change in angular momentum of the neutron superfluid is determined by the motion of its vortex lines. In the star's inner crust, we assume vortices are pinned by density fluctuations of defects (vacancies in the nuclear lattice or impurities) and move by the process of vortex creep. The vortex line, subjected to a random potential, has many metastable states for which a barrier energy and a pinning force are estimated. Scaling properties of vortex creep including both quantum and classical unpinning processes are obtained, namely the vortex creep velocity and the crossover temperature.

Chevalier, Eric

1993-09-01

310

Topological analysis of paraxially scattered electron vortex beams  

NASA Astrophysics Data System (ADS)

We investigate topological aspects of subnanometer electron vortex beams upon elastic propagation through atomic scattering potentials. Two main aspects can be distinguished: (i) significantly reduced delocalization compared to a similar nonvortex beam if the beam centers on an atomic column and (ii) site symmetry dependent splitting of higher-order vortex beams. Furthermore, the results provide insight into the complex vortex line fabric within the elastically scattered wave containing characteristic vortex loops predominantly attached to atomic columns and characteristic twists of vortex lines around atomic columns.

Lubk, Axel; Clark, Laura; Guzzinati, Giulio; Verbeeck, Jo

2013-03-01

311

Vortex model of open channel flows with gravel beds  

NASA Astrophysics Data System (ADS)

Turbulent structures are known to be important physical processes in gravel-bed rivers. A number of limitations exist that prohibit the advancement and prediction of turbulence structures for optimization of civil infrastructure, biological habitats and sediment transport in gravel-bed rivers. This includes measurement limitations that prohibit characterization of size and strength of turbulent structures in the riverine environment for different case studies as well as traditional numerical modeling limitations that prohibit modeling and prediction of turbulent structure for heterogeneous beds under high Reynolds number flows using the Navier-Stokes equations. While these limitations exist, researchers have developed various theories for the structure of turbulence in boundary layer flows including large eddies in gravel-bed rivers. While these theories have varied in details and applicable conditions, a common hypothesis has been a structural organization in the fluid which links eddies formed at the wall to coherent turbulent structures such as large eddies which may be observed vertically across the entire flow depth in an open channel. Recently physics has also seen the advancement of topological fluid mechanical ideas concerned with the study of vortex structures, braids, links and knots in velocity vector fields. In the present study the structural organization hypothesis is investigated with topological fluid mechanics and experimental results which are used to derive a vortex model for gravel-bed flows. Velocity field measurements in gravel-bed flow conditions in the laboratory were used to characterize temporal and spatial structures which may be attributed to vortex motions and reconnection phenomena. Turbulent velocity time series data were measured with ADV and decomposed using statistical decompositions to measure turbulent length scales. PIV was used to measure spatial velocity vector fields which were decomposed with filtering techniques for flow visualization. Under the specific conditions of a turbulent burst the fluid domain is organized as a braided flow of vortices connected by prime knot patterns of thin-cored flux tubes embedded on an abstract vortex surface itself having topology of a Klein bottle. This model explains observed streamline patterns in the vicinity of a strong turbulent burst in a gravel-bed river as a coherent structure in the turbulent velocity field. KEY WORDS: Open channel flow, turbulence, gravel-bed rivers, coherent structures, velocity distributions

Belcher, Brian James

312

Dynamic origin of vortex core switching in soft magnetic nanodots.  

PubMed

The magnetic vortex with in-plane curling magnetization and out-of-plane magnetization at the core is a unique ground state in nanoscale magnetic elements. This kind of magnetic vortex can be used, through its downward or upward core orientation, as a memory unit for information storage, and thus, controllable core switching deserves some special attention. Our analytical and micromagnetic calculations reveal that the origin of vortex core reversal is a gyrotropic field. This field is induced by vortex dynamic motion and is proportional to the velocity of the moving vortex. Our calculations elucidate the physical origin of the vortex core dynamic reversal, and, thereby, offer a key to effective manipulation of the vortex core orientation. PMID:18232915

Guslienko, Konstantin Yu; Lee, Ki-Suk; Kim, Sang-Koog

2008-01-16

313

Magnetic vortex dynamics induced by an electrical current  

NASA Astrophysics Data System (ADS)

A magnetic nanoparticle in a vortex state is a promising candidate for the information storage. One bit of information corresponds to the upward or downward magnetization of the vortex core (vortex polarity). The dynamics of the magnetic vortex driven by a spin current is studied theoretically. Using a simple analytical model and numerical simulations, we show that a nondecaying vortex motion can be excited by a dc spin-polarized current, whose intensity exceeds a first threshold value as a result of the balance between a spin-torque pumping and damping forces. The irreversible switching of the vortex polarity takes place for a current above a second threshold. The mechanism of the switching, which involves the process of creation and annihilation of a vortex-antivortex pair is described analytically, using a rigid model, and confirmed by detailed spin-lattice simulations.

Gaididei, Yuri; Kravchuk, Volodymyr P.; Sheka, Denis D.

314

Vortex element methods for fluid dynamic analysis of engineering systems  

SciTech Connect

This book consists of two parts (a total of 12 chapters), an appendix (17 computer programs), a bibliography, and an index. Part one, entitled: The surface vorticity method for inviscid ideal flow, is comprised of six chapters: The basis of surface singularity modeling; lifting bodies, two-dimensional aerofoils and cascades; mixed-flow and radial cascades; bodies of revolution, ducts and annuli; ducted propellers and fans; and three-dimensional and meridional flows in turbomachines. Part two, entitled: Free shear layers, vortex dynamics and vortex cloud analysis, covers the remaining five chapters: Free vorticity shear layers and inverse methods; vortex dynamics in inviscid flows; simulation of viscous diffusion in discrete vortex modeling; vortex cloud modeling by the boundary integral method; further development and applications of vortex cloud modeling to lifting bodies and cascades; and, use of grid systems in vortex dynamics and meridional flows.

Lewis, R.I.

1991-12-31

315

Stability of incompressible current-vortex sheets  

NASA Astrophysics Data System (ADS)

We revisit the study in [Y. Trakhinin, On the existence of incompressible current-vortex sheets: study of a linearized free boundary value problem, Math. Methods Appl. Sci. 28 (2005) 917-945] where an energy a priori estimate for the linearized free boundary value problem for planar current-vortex sheets in ideal incompressible magnetohydrodynamics was proved for a part of the whole stability domain found a long time ago in [S.I. Syrovatskij, The stability of tangential discontinuities in a magnetohydrodynamic medium, Zh. Eksper. Teor. Fiz. 24 (1953) 622-629 (in Russian); W.I. Axford, Note on a problem of magnetohydrodynamic stability, Canad. J. Phys. 40 (1962) 654-655]. In this paper we derive an a priori estimate in the whole stability domain. The crucial point in deriving this estimate is the construction of a symbolic symmetrizer for a nonstandard elliptic problem for the small perturbation of total pressure. This symmetrizer is an analogue of Kreiss' type symmetrizers. As in hyperbolic theory, the failure of the uniform Lopatinski condition, i.e., the fact that current-vortex sheets are only weakly (neutrally) stable yields loss of derivatives in the energy estimate. The result of this paper is a necessary step to prove the local-in-time existence of stable nonplanar incompressible current-vortex sheets by a suitable Nash-Moser type iteration scheme.

Morando, Alessandro; Trakhinin, Yuri; Trebeschi, Paola

2008-11-01

316

Combustion analysis of a vortex biomass furnace  

Microsoft Academic Search

A vortex type biomass furnace was tested for converting corn cobs into thermal energy. The performance of the furnace was determined by a series of 13 tests. Two independent variables were studied: corn cob feeding rate, and air damper opening. Response surface method of analysis was used to statistically analyze the results of the test. The results showed that three

Wahby; M. F. I

1982-01-01

317

Steady ellipsoidal vortex rings with finite cores  

Microsoft Academic Search

The present paper provides explicit numerical descriptions of vortex rings that are exact solutions to the Navier-Stokes equations inside of the chosen ellipsoidal boundaries. It is a particular feature of the resulting rings that they have finite cores within which the vorticity is nonzero whereas outside the cores no vorticity exists. The vorticity distribution is in agreement with the Navier-Stokes

F. Durst; B. Schoenung; M. Simons

1981-01-01

318

Vortex induced motion in compliant structures  

NASA Astrophysics Data System (ADS)

The coupling of the unsteady shedding of vortices from the leading and trailing edges of a flat plate can lead to large scale oscillations of a structure. Examples of these large motions abound in engineered structures (Traffic signs vibrating in the wind, wing flutter, chattering venetian blinds, etc.) and in nature (the rustling of leaves on a tree in the wind). In all of these examples, the efficiency of energy extraction from the flow to the structure increases dramatically as the vortex shedding and structural vibrations near resonance. As the motion becomes more exaggerated, the fluid-structure interaction becomes increasingly nonlinear as the motion of the plate becomes increasingly important to the vortex shedding dynamics. We present experimental results from two related systems tested in a low speed wind tunnel (using high-speed videography, PIV and hotwire anemometry) (i) a rectangular cantilevered flat plate free to bend and twist, and (ii) a flexible ribbon pinned at its two ends and exposed to the flow. In both systems, a rich phase map of vortex-induced vibrations is described in which both mechanisms for vortex shedding and structural vibration can be tuned independently using geometry, material properties and flow conditions.

Song, Arnold; Tuttman, Max; Breuer, Kenneth

2008-11-01

319

Vortex Ring State and Asymmetric Thrust Oscillations  

Microsoft Academic Search

When the helical vortices of a rotor are not convected away, the vortices may form a ring-like structure about the rotor disk. This vortex ring state (VRS) is most common during rapid descent and leads to thrust oscillations coupled to the formation and subsequent breakdown of the ring. Experimental observations at and near VRS were made using strobed particle image

Gregory McCauley; Omer Savas; Francis Caradonna

2008-01-01

320

Observations on Multiple Trailing Vortex Merger  

NASA Astrophysics Data System (ADS)

The merger of multiple trailing vortices is observed experimentally. Rectangular wing semi-spans of various aspect ratios are used to create wing-tip vortices in a miniature water towing tank. The wings are supported from a pair of streamlined struts positioned near the tank walls which are towed from the towing carriage. LIF and DPIV are the experimental measurement tools. Using multiple airfoils, up to 4 separate trailing vortices can be created in the tank at the same time. The vortices generated are of like sign (co-rotating). The effects of initial separation distance, circulation Reynolds number Re_?, relative vortex strength, and number of vortices (2, 3, or 4) are investigated. A single trailing vortex is used as a baseline. Chord-based Reynolds number Rec is varied from approximately 4 \\cdot 10^4 to 4 \\cdot 10^5 and Re_? is varied from approximately 5 \\cdot 10^3 to 3 \\cdot 10^5. As in previous observations,( Chen, Jacob, & Sava?), to appear in JFM. the merger of a pair of co-rotating vortices is observed in typically one orbit period. The extremes of Re_? show variations in the merger process while relative vortex stength has a large impact on merger details. The total circulation remains constant from roll-up completion through merger, as do kinetic energy and angular momentum. For 3 or 4 vortices, merger occurs between the closest vortices first; thereafter the system behaves similar to a co-rotating vortex pair.

Jacob, J. D.

1998-11-01

321

Calculation of Vortex-Flap Aerodynamic Characteristics.  

National Technical Information Service (NTIS)

The lateral-directional characteristics for configurations with vortex flaps were calculated by the VORSTAB code. In view of the poor correlation between the VORSTABL results and the data, it was decided to examine in detail the reasons behind the discrep...

C. E. Lan C. C. Hsing

1985-01-01

322

Dynamics of Saturn's South Polar Vortex  

Microsoft Academic Search

We present observations of Saturn's south polar vortex (SPV) showing that it shares some properties with terrestrial hurricanes: cyclonic circulation, warm central region (the eye) surrounded by a ring of high clouds (the eye wall), and convective clouds outside the eye. The polar location and the absence of an ocean are major differences. It also shares properties with the polar

Ulyana A. Dyudina; Andrew P. Ingersoll; Shawn P. Ewald; Ashwin R. Vasavada; Robert A. West; Anthony D. Del Genio; John M. Barbara; Carolyn C. Porco; Richard K. Achterberg; F. Michael Flasar; Amy A. Simon-Miller; Leigh N. Fletcher

2008-01-01

323

Optical vortex behavior in dynamic speckle fields  

NASA Astrophysics Data System (ADS)

The dynamic behavior of phase singularities, or optical vortices, in the pseudo-phase representation of dynamic speckle patterns is investigated. Sequences of band-limited, dynamic speckle patterns with predetermined Gaussian decorrelation behavior were generated, and the pseudo-phase realizations of the individual speckle patterns were calculated via a two-dimensional Hilbert transform algorithm. Singular points in the pseudo-phase representation are identified by calculating the local topological charge as determined by convolution of the pseudo-phase representations with a series of 2×2 nabla filters. The spatial locations of the phase singularities are tracked over all frames of the speckle sequences, and recorded in three-dimensional space (x,y,f), where f is frame number in the sequence. The behavior of the phase singularities traces 'vortex trails' which are representative of the speckle dynamics. Slowly decorrelating speckle patterns results in long, relatively straight vortex trails, while rapidly decorrelating speckle patterns results in tortuous, relatively short vortex trails. Optical vortex analysis such as described herein can be used as a descriptor of biological activity, flow, and motion.

Kirkpatrick, Sean J.; Khaksari, Kosar; Thomas, Dennis; Duncan, Donald D.

2012-05-01

324

VORTEX INDUCED VIBRATIONS AT HIGH REYNOLDS NUMBERS  

Microsoft Academic Search

Vortex induced vibrations of circular section structures are a well known and deeply studied phenomenon because many engineering applications are involved by this kind of prob- lems. Up to now most part of the experimental results belong to a Reynolds Number range be- tween 500 and 6 ¢ 104 and no reliable numerical simulations are available for Reynolds higher than

Giorgio Diana; Marco Belloli; Stefano Giappino; Sara Muggiasca

325

Josephson vortex quantum bits: Decoherence and entanglement  

Microsoft Academic Search

In this dissertation work, I investigate the decoherence time of a Josephson vortex qubit (JVQ) and the level of entanglement between two JVQs. A JVQ may be fabricated by embedding two closely spaced microresistors in the insulating layer of a long Josephson junction (LJJ). The phase dynamics of the JVQ may be described by using the perturbed sine-Gordon equation. This

Ramesh P. Dhungana

2009-01-01

326

Vortex Dipoles with Prescribed Nonlinear Profiles  

NASA Astrophysics Data System (ADS)

We obtain translating vortex pairs using a generalization of the method used in Elcrat,Fornberg,Horn and Miller JFM2000 409 for vortex patches in flow past a cylinder. When the profile function F in ??=?F(?-?), ? the stream function for the flow, is piecewise constant the flows obtained are the Translating V-States found in Wu,Overman and Zabusky JCP1984 53. When the vortex support attaches to the symmetry axis the flows are called dipoles, and when F is linear we retrieve the Lamb-Chaplygin pair. The solution procedure that we use in which ? is obtained from an iteration ??n+1=F(?n) where the area of the vortex support is fixed in an inner iteration, allows general F. We have computed solutions for F that have 2 continuous derivatives at ?=0. These lead to ``smooth'' dipoles, and the solutions obtained have elliptical shapes of the sort obtained recently in Kizner and Khvoles Reg.Chaotic Dyn. 2004 9. The methods that we use extend naturally to translating dipoles in the ? -plane approximation for flow over a rotating sphere.

Elcrat, Alan; Miller, Ken; Albrecht, Trenton

2009-11-01

327

On tornado-like vortex flows  

Microsoft Academic Search

In a first step, the problem of inviscid axisymmetric flow with buoyancy is investigated. It is found that both supercritical and subcritical vortex flows depart from their critical flow states if they are dominated by buoyancy. In a second step, the effects of entrainment are also taken into account. However, the investigation is restricted to nearly self-similar flows. Both supercritical

Jakob J. Keller

1994-01-01

328

Studies of perturbed three vortex dynamics  

NASA Astrophysics Data System (ADS)

It is well known that the dynamics of three point vortices moving in an ideal fluid in the plane can be expressed in Hamiltonian form, where the resulting equations of motion are completely integrable in the sense of Liouville and Arnold. The focus of this investigation is on the persistence of regular behavior (especially periodic motion) associated with completely integrable systems for certain (admissible) kinds of Hamiltonian perturbations of the three vortex system in a plane. After a brief survey of the dynamics of the integrable planar three vortex system, it is shown that the admissible class of perturbed systems is broad enough to include three vortices in a half plane, three coaxial slender vortex rings in three space, and ``restricted'' four vortex dynamics in a plane. Included are two basic categories of results for admissible perturbations: (i) general theorems for the persistence of invariant tori and periodic orbits using Kolmogorov-Arnold-Moser- and Poincaré-Birkhoff-type arguments and (ii) more specific and quantitative conclusions of a classical perturbation theory nature guaranteeing the existence of periodic orbits of the perturbed system close to cycles of the unperturbed system, which occur in abundance near centers. In addition, several numerical simulations are provided to illustrate the validity of the theorems as well as indicating their limitations as manifested by transitions to chaotic dynamics.

Blackmore, Denis; Ting, Lu; Knio, Omar

2007-06-01

329

Tip vortex cavitation suppression by mass injection  

NASA Astrophysics Data System (ADS)

Injection of water and aqueous polymer solutions in to the core of a trailing vortex is found to delay the onset of tip vortex cavitation (TVC). For the case without any mass injection, cavitation inception (?I= 3.3) occurred at a substantially higher pressure (-Cpmin= 2.3) than that was expected based on the mean vortical flow. Mass injection (both water and polymer) into the vortex core led to a reduction in the inception pressure. 2-D Particle Image Velocimetry was performed in a region of flow in the vicinity of the average inception location near the hydrofoil tip to determine the instantaneous flow fields near the vortex core. Mass injection led to significant modification of the unsteady flow field, while the average flow field was not strongly affected. A 50% reduction in RMS velocities in comparison with the non-injection conditions was observed for the case of polymer injection, the case of maximum cavitation suppression. Cavitation inception/desinence studies were conducted for different mass and momentum fluxes to develop a hypothesis for TVC suppression.

Ganesh, Harish; Chang, Natasha; Ceccio, Steven

2010-11-01

330

A Cold Jovian Arctic Polar Vortex: Evidence from Infrared Imaging  

NASA Astrophysics Data System (ADS)

A prominent cold arctic airmass in Jupiter is revealed by thermal images taken at NASA's Infrared Telescope Facility (IRTF) during Jupiter's northern summer in 1999. This cold airmass is well defined by a sharp 4-degree thermal gradient in both the stratosphere and the upper troposphere and tropopause regions. The latitude boundary of the cold airmass oscillates in longitude with principal wavenumber 5--6. This longitudinal oscillation is coincident with the oscillation of the boundary of the thick polar hood that is detectable in reflected sunlight that is sensitive to particles around Jupiter's tropopause (~100 mbar pressure), using IRTF 2.3-?m and HST WFPC2 890-nm images. The sinusoidal boundaries slowly rotate prograde with respect to the interior. The proximity and similarity of the thermal and particle boundaries suggests that the phenomenon is a classical polar vortex of the same type as seen in the Earth's antarctic. Testing of possible gaseous entrainment within the vortex' area would verify or refute similarities with polar vortices in the Earth, Venus, Mars and possibly Titan. This phenomenon is relevant to studies of terrestrial meteorology by measuring the extent to which stratospheric phenomena can drive tropospheric properties. Detailed studies of Jupiter's polar regions might be most easily accomplished from appropriate remote sensing instrumentation on a polar orbiter mission as a result of optimized spatial resolution. The work reported here was supported by funds from NASA to the Jet Propulsion Laboratory, California Institute of Technology. Ori Fox was supported by the Undergraduate Student Researcher Program (USRP).

Orton, G. S.; Fisher, B. M.; Baines, K. H.; Momary, T.; Fox, O.

2002-12-01

331

Vortex nanoliquid in high-temperature superconductors  

NASA Astrophysics Data System (ADS)

Vortex matter is commonly considered as a homogenous glassy medium. Correlated disorder in the form of columnar defects (CDs) is shown to result in formation of new heterogeneous phases of vortex matter. We have developed a magneto-optical method that allows visualization of the distribution of small transport currents applied to BSCCO crystals irradiated through patterned masks [1]. When vortices outnumber CDs we identify two distinct populations: vortices residing on CDs are strongly pinned and form a rigid `porous' skeleton, whereas the excess vortices form weakly pinned ordered crystallites caged within the pores of the skeleton [2,3]. The melting process of this porous vortex matter is qualitatively different from melting of a homogenous system. The soft crystallites melt while the rigid skeleton remains in tact, forming a vortex nanoliquid in which intercalated liquid droplets of just few vortices are embedded in a porous solid matrix. The nanoliquid phase possesses unique properties and displays a high degree of correlation along the c-axis but no transverse critical current. The melting of heterogeneous vortex matter occurs in two steps resulting in a ``Y'' shaped phase diagram: first the soft crystallites undergo a melting transition forming a nanoliquid in which localized and delocalized vortices coexist, while a homogeneous liquid is formed at higher temperatures upon a delocalization transition of the skeleton from the CDs [1]. At lower fields the solid melts through a single first-order phase transition. [1] S. S. Banerjee, S. Goldberg, A. Soibel, Y. Myasoedov, M. Rappaport, E. Zeldov, F. de la Cruz, C. J. van der Beek, M. Konczykowski, T. Tamegai, and V. M. Vinokur, PRL 93, 097002 (2004). [2] S. S. Banerjee et al., PRL 90, 087004 (2003). [3] M. Menghini et al., PRL 90, 147001 (2003).

Zeldov, Eli

2005-03-01

332

Persistence of Metastable Vortex Lattice Domains in MgB2 in the Presence of Vortex Motion  

SciTech Connect

Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.

Rastovski, Catherine [University of Notre Dame, IN; Schlesinger, Kimberly [University of Notre Dame, IN; Gannon, William J [Northwestern University, Evanston; Dewhurst, Charles [Institut Laue-Langevin (ILL); Debeer-Schmitt, Lisa M [ORNL; Zhigadlo, Nikolai [ETH Zurich, Switzerland; Karpinski, Janusz [ETH Zurich, Switzerland; Eskildsen, Morten [University of Notre Dame, IN

2013-01-01

333

Identifying optimal vortex spacing for swimming and flying animals  

NASA Astrophysics Data System (ADS)

Swimming and flying animals generate thrust by creating an unsteady vortex wake through the oscillation of their appendages. To determine the vortex spacing that maximizes propulsive efficiency, a finite core vortex array model was developed to compute the unsteady velocity field generated by vortex streets representative of bio- inspired propulsion. The model systematically varies the streamwise and transverse spacing between vortex cores to determine the time averaged velocity field induced by a reverse von Karman vortex street and a uniform freestream velocity. Experimental particle image velocimetry was conducted in the wake of a rigid pitching panel to determine the size and strength of the vortex cores to input to the model. Viscosity is accounted for by assuming a Gaussian vorticity distribution around the vortex core. A linear spatial stability analysis was performed on the computed velocity profiles to determine which vortex configuration leads to efficient propulsion. Here it is assumed that efficient propulsion proceeds when the driving frequency of the vortex street matches the resonant frequency of velocity jet.

Dewey, Peter A.; Moored, Keith W.; Quinn, Daniel B.; Smits, Alexander J.

2011-11-01

334

On the Origin of Polar Vortex Air  

NASA Astrophysics Data System (ADS)

The existence of the multi-year HALOE CH4 data set, together with some comparisons of forward with back trajectory calculations which we have carried out, has motivated us to reexamine the question of polar vortex descent. Three-dimensional diabatic trajectory calculations have been carried out for the seven month fall to spring period in both the northern hemisphere (NH) and southern hemisphere (SH) polar stratosphere for the years 1992-1999. These computations are compared to fixed descent computations where the parcels were fixed at their latitude-longitude locations and allowed to descend without circulating. The forward trajectory computed descent is always less than the fixed descent due to horizontal parcel motions and variations in heating rates with latitude and longitude. Although the forward calculations estimate the maximum amount of descent that can occur, they do not necessarily indicate the actual origin of springtime vortex air. This is because more equatorward air can be entrained within the vortex during its formation. To examine the origin of the spring vortex air, the trajectory model was run backward for seven months from spring to fall. The back trajectories show a complex distribution of parcels in which one population originates in the upper stratosphere and mesosphere and experiences considerable descent in the polar regions, while the remaining parcels originate at lower altitudes of the middle and lower stratosphere and are mixed into the polar regions during vortex formation without experiencing as much vertical transport. The amount of descent experienced by the first population shows little variability from year to year, while the computed descent and mixing of the remaining parcels show considerable interannual variability due to the varying polar meteorology. Because of this complex parcel distribution it is not meaningful to speak of a net amount of descent experienced over the entire winter period. Since the back trajectories indicate that much of the air can come from lower altitudes than would be implied by the forward calculations, using a comparison between pre-winter and post-winter tracer profiles to estimate the amount of descent over this period will give erroneous descent amounts. In order to evaluate the computed descent, spring methane amounts were computed by mapping HALOE fall observations onto the final latitude-altitude locations of the back trajectories. These locations indicate the origin of the spring vortex air. The agreement between the computed means and the spring HALOE means is generally within 0.1-0.2 ppmv in the NH and 0.1-0.4 ppmv in the SH.

Rosenfield, J. E.; Schoeberl, M. R.

2001-05-01

335

Experimental study of a vortex ring impacting a smart material-based cantilevered plate  

NASA Astrophysics Data System (ADS)

Recent developments in lightweight smart materials have generated scientific and technological advancements in small scale energy harvesting for powering low-consumption electronic devices. Often, energy is harvested from base excitation of a cantilevered smart material strip. In this case, the encompassing fluid acts as a passive damper, reducing the vibration amplitude and frequency, which reduces the harvesting capacity. By comparison, relatively few research efforts to date have explored the feasibility of using smart materials for harvesting energy directly from fluid motion. In this paper we employ vortex rings as the source from which to extract energy and use an ionic polymer metal composite (IPMC) strip in a cantilevered configuration as the harvesting device. Vortex rings, generated using a piston/cylinder arrangement submersed in water, are fired at the IPMC harvester and the resulting impact is recorded using a high speed video camera. The vortex ring propagation and circulation are estimated using flow visualization and particle image velocimetry. The plate deflection and electrical output are recorded as functions of time and correlated to the vortex strength and geometry.

Peterson, Sean; Porfiri, Maurizio

2011-11-01

336

Modeling and simulation of vortex induced vibration on the subsea riser/pipeline (GRP pipe)  

NASA Astrophysics Data System (ADS)

This paper presents the research work conducted to investigate the dynamics characteristics of the offshore riser pipeline due to vortex flow and to develop a model that could predict its vortex induced responses. Glass-fiber reinforced plastic (GRP) pipe is used for this study which has smaller density from the steel. A two-dimensional finite element computational method is implemented to describe the dynamic behavior of the riser. The governing equation of motion was based on Hamilton's principle, consists of the strain energy due to bending and axial deformation, kinetic energy due to both riser and internal fluid movement and also external force from currents and waves. A direct integration method namely Newmark integration scheme is proposed to solve the equation of motion. A MATLAB program code was developed to obtain the simulation results. The natural frequency and damping ratio are presented for each mode. Dynamic response of riser is shown in time-domain and the numerical results are discussed. Several parameter effects are used to investigate dynamic responses and the results show an agreement with the theory. Vortex shedding phenomenon also has been discussed in this paper. As a conclusion, the simulation results have successfully shown the vortex induced vibration responses for GRP pipeline.

Raja Adli, Raja Nor Fauziah bt; Ibrahim, Idris

2012-06-01

337

The dynamics of vortex shedding of flow past a vertical flat plate; LES studies  

NASA Astrophysics Data System (ADS)

Although, apparently flow-induced vibrations represent a canonical problem, a complete understanding of the fluid-structure mechanism of interaction has not yet been achieved. One of the issues associated with flow induced vibrations stems from the vortex shedding phenomenon. It is well known that vortex streets are formed in the wake of bluff bodies over a wide range of Reynolds numbers. The periodic shedding of vortices may result in significant fluctuating loading on the body. When the shedding frequency is close to one of the characteristic frequencies of the body, the resonant oscillations of the body can be excited, causing damaging instabilities. Various studies regarding the vortex shedding resonance or "lock-on" phenomenon have been conducted. However, the effect of Reynolds number on the "lock-on" regime is yet to be fully understood. The "lock-on" phenomenon is of critical importance for the analysis of flow-induced vibration, when the aeroelastic response of the structure is considered. In the present research the influence of sweeping angle on the plate tip vortex formation is studied numerically using large eddy simulation (LES). The results show an increase in magnitude and size of vertical structures developed in the wake of the plate.

Velez, Carlos; Ilie, Marcel

2010-11-01

338

Resuspension onset and crater erosion by a vortex ring interacting with a particle layer  

NASA Astrophysics Data System (ADS)

This paper presents results from an experimental investigation of the interaction of a vortex ring with a particle layer. The flow dynamics during the onset of particle resuspension are analysed using particle image velocimetry, while a light attenuation method provides accurate measurements of the final eroded crater shape. This work is a continuation of the research described in R. J. Munro, N. Bethke, and S. B. Dalziel, ``Sediment resuspension and erosion by vortex rings,'' Phys. Fluids 21, 046601 (2009), which focussed on the general resuspension onset dynamics and initial crater formation. Here, we analyse the velocity induced by the vortex ring on the particle layer surface during the resuspension of particles for different particle sizes, and the shape and size of the final craters that are formed by the impact of the vortex ring. We find that the boundary condition is characterised by a quasi-slip velocity at the particle layer surface, independent of the particle size. The particle diameter, and thus bed permeability, is found to have a significant effect on the final crater characteristics.

Bethke, N.; Dalziel, S. B.

2012-06-01

339

Vortex structure in strongly stratified flows  

NASA Astrophysics Data System (ADS)

Turbulence decaying experiments have been performed, with the aim of focusing in the middle of a strongly stratified density interface. The experiments have been done under different external conditions[1]: Non-Rotating Decaying 2D Turbulence experiments , Rotating Decaying 2D Turbulence experiments, And steady rotating stratified experiments. Non-Rotating experiments were performed in a 1mx1m tank, while the Rotating experiments were performed in a rectangular tank of 4mx 2m; this rectangular tank was placed in the middle of the Coriolis Rotating platform at the Trondheim Marine Systems Research Infrastructure supported by the European Union TMR Project HydraLab. The set of stirred experiments is a compilation of several series of traversing grid mixing experiments, dependent on the initial interface Richardson number [2]. PIV was used to map the velocity and vorticity plots in time. The density of the brine used in the experiments to create a sharp density interface. The boundary conditions for all the rotating experiment are related to initial Reynolds Rer, Rossby Ro, Ekman Ek and Richardson gradient Rig numbers, the results are summarized and presented in a 3D parameter map using power relationships. The experimental results of the strongly non-homogeneous turbulent dynamics shows the different decay of the strongest vortices as a function of the local Richardson number and the interaction mechanisms between inertial and internal waves. A study of vortex decay number indicates a strong non linear relationship with a slower decay due to the internal wave activity at intermediate Richardson number experiments. The intermittency of the flow is studied using a generalized intermitency parameter family that depends on the order.[3,4] [1] Matulka A.M. PhD Thesis UPC, Barcelona 2010. [2]Matulka A.M., Redondo J.M. and Carrillo A. Experiments in rotating decaying 2D flows Il nuovo cimento C, 31, 5-6, 757-770. 2008. [3]Ben-Mahjoub O., Babiano A. y Redondo J.M. Velocity structure and Extended Self Similarity in nonhomogeneous Turbulent Jets and Wakes. Journal of flow turbulence and combustion. 59 , 299-313. 1998. [4]Ben-Mahjoub O., Redondo J.M., and R. Alami. Turbulent Structure Functions in Geophysical Flows, Rapp. Comm. int. Mer Medit., 35, 126-127. 1998 [3]Babiano, A., Dubrulle, B., Frick, P. Some properties of two-dimensional inverse energy cascade dynamics, Phys. Rev. E. 55, 2693, 1997. [4]Vindel J.M., Yague C. and J.M. Redondo, Structure function analysis and intermittency in the ABL, NonLin. Proc. Geophys. 15, 6. 915-929. 2009.

Magdalena Matulka, Anna

2010-05-01

340

Neutron Scattering Studies of Vortex Matter in Type-II Superconductors  

SciTech Connect

The proposed program is an experimental study of the fundamental properties of Abrikosov vortex matter in type-II superconductors. Most superconducting materials used in applications such as MRI are type II and their transport properties are determined by the interplay between random pinning, interaction and thermal fluctuation effects in the vortex state. Given the technological importance of these materials, a fundamental understanding of the vortex matter is necessary. The vortex lines in type-II superconductors also form a useful model system for fundamental studies of a number of important issues in condensed matter physics, such as the presence of a symmetry-breaking phase transition in the presence of random pinning. Recent advances in neutron scattering facilities such as the major upgrade of the NIST cold source and the Spallation Neutron Source are providing unprecedented opportunities in addressing some of the longstanding issues in vortex physics. The core component of the proposed program is to use small angle neutron scattering and Bitter decoration experiments to provide the most stringent test of the Bragg glass theory by measuring the structure factor in both the real and reciprocal spaces. The proposed experiments include a neutron reflectometry experiment to measure the precise Q-dependence of the structure factor of the vortex lattice in the Bragg glass state. A second set of SANS experiments will be on a shear-strained Nb single crystal for testing a recently proposed theory of the stability of Bragg glass. The objective is to artificially create a set of parallel grain boundaries into a Nb single crystal and use SANS to measure the vortex matter diffraction pattern as a function of the changing angle between the applied magnetic field to the grain boundaries. The intrinsic merits of the proposed work are a new fundamental understanding of type-II superconductors on which superconducting technology is based, and a firm understanding of phases and phase transitions in condensed matter systems with random pinning. The broader impact of the program includes the training of future generation of neutron scientists, and further development of neutron scattering and complementary techniques for studies of superconducting materials. The graduate and undergraduate students participating in this project will learn the state-of-the-art neutron scattering techniques, acquire a wide range of materials research experiences, and participate in the frontier research of superconductivity. This should best prepare the students for future careers in academia, industry, or government.

Xinsheng Ling

2012-02-02

341

Mass flow measurement of gas-liquid bubble flow with the combined use of a Venturi tube and a vortex flowmeter  

Microsoft Academic Search

Development of effective techniques for gas-liquid two-phase flow measurement is of interest to both academic research and industrial applications. This paper presents a novel approach to the measurement of the mass flow rate of homogeneous gas-liquid bubble flow with the combined use of a Venturi tube and a vortex flowmeter. The Venturi tube and the vortex flowmeter were mounted in

Zhiqiang Sun

2010-01-01

342

Dynamic LES of Colliding Vortex Rings Using a 3D Vortex Method  

NASA Astrophysics Data System (ADS)

A Lagrangian particle method is used to simulate the collision of coaxial vortex rings in three dimensions. The scheme combines a 3D, adaptive, viscous, vortex element method with a dynamic eddy viscosity model of the subfilter scale stresses. The vortex method is based on discretization of the vorticity field into Lagrangian vortex elements and transport of the elements along particle trajectories. The computations incorporate a mesh redistribution algorithm which creates new elements in regions of high strain and locally redistributes the vorticity field into a smaller number of elements when particles tend to cluster. The subfilter scale vorticity model consists of approximating the effect of unresolved vorticity stresses using a gradient-diffusion eddy viscosity model, following the development in Part I (J. R. Mansfield, O. M. Knio, and C. Meneveau, J. Comput. Phys. 145, 693 (1998)). Dynamic implementation of the model relies on determining model coefficients through test-filtering the Lagrangian particle representation of the filtered vorticity field. Computations of ring collisions show that, combined, the mesh redistribution scheme and subfilter scale model result in a robust scheme that can be extended into the late stages of evolution of the flow. In addition, it is shown that the Lagrangian LES scheme captures several experimentally observed features of the ring collisions, including turbulent breakdown into small-scale structures and the generation of small-scale radially propagating vortex rings.

Mansfield, John R.; Knio, Omar M.; Meneveau, Charles

1999-06-01

343

Fast numerical simulation of vortex shedding in tube arrays using a discrete vortex method  

NASA Astrophysics Data System (ADS)

Vortex shedding may occur in tube arrays, resulting in strong excitation forces at discrete frequencies. In the past, the Strouhal numbers governing vortex shedding in these systems were determined primarily by experiment. This paper presents a computationally inexpensive method of numerical simulation for the unsteady flow through a rigid normal triangular tube array which determines both the frequency of vortex shedding and the instantaneous flow structure. The technique used is based on a discrete vortex method similar to the cloud-in-cell approach which has been applied to flow problems for small numbers of cylinders. However, in the current implementation, the flow velocity calculation is carried out on an unstructured grid using a finite element discretization. Thus, the complex geometry associated with a tube array can be easily accommodated. The method, referred to as the ``Cloud-in-element'' method, is validated for the standard case of flow over a single cylinder and then applied to flow through a normal triangular array with a pitch-to-diameter of 1.6. The Reynolds number is 2200. The Strouhal number obtained from the numerical simulation is 1.27, which is within 6% of the value available in the literature. Qualitatively, the vortex shedding pattern obtained is in agreement with published flow visualization.

Sweeney, C.; Meskell, C.

2003-11-01

344

Jetlike tunneling from a trapped vortex  

NASA Astrophysics Data System (ADS)

We analyze tunneling from vortex states in elliptically shaped traps. Using the hydrodynamic representation of the Gross-Pitaevskii (nonlinear Schrödinger) equation, we derive analytically and demonstrate numerically an interesting type of quantum fluid flow: a jetlike singularity formed by the interaction between the vortex and the asymmetric trap. For strongly elongated traps and high enough vorticity, the ellipticity overwhelms the circular rotation, resulting in the ejection of jets in narrow, well-defined directions. These jets are formed due to a convergence of trajectories starting from the top of the potential barrier and meeting at a certain point on the exit line. Under proper conditions they will appear in any coherent wave system with angular momentum and noncircular symmetry, such as superfluids, Bose-Einstein condensates, and light.

Cohen, E.; Muenzel, S.; Farberovich, O.; Fleischer, J.; Fleurov, V.; Soffer, A.

2013-10-01

345

Stationary vortex sheets in a stirring flow  

NASA Astrophysics Data System (ADS)

Stationary vortex sheets in a two-dimensional stirring flow may be approximated by arrays of stationary point vortices arranged along the support of the sheets. These vortices lie at the roots of a polynomial that satisfies a generalized Lamé differential equation; the polynomial itself (not the roots) determines the complex potential and stream function. In this paper, sufficient conditions for the stirring flow are found so that the differential equation has two independent polynomial solutions with simple closed-form expressions, analogous to hypergeometric polynomials. The corresponding point vortex array then depends on a complex parameter that controls the location of the sheet, so that it may pass through any selected point. Stationary sheets in a periodic flow are approximated by the same method.

O'Neil, Kevin A.

2013-03-01

346

Integrated compact optical vortex beam emitters.  

PubMed

Emerging applications based on optical beams carrying orbital angular momentum (OAM) will probably require photonic integrated devices and circuits for miniaturization, improved performance, and enhanced functionality. We demonstrate silicon-integrated optical vortex emitters, using angular gratings to extract light confined in whispering gallery modes with high OAM into free-space beams with well-controlled amounts of OAM. The smallest device has a radius of 3.9 micrometers. Experimental characterization confirms the theoretical prediction that the emitted beams carry exactly defined and adjustable OAM. Fabrication of integrated arrays and demonstration of simultaneous emission of multiple identical optical vortices provide the potential for large-scale integration of optical vortex emitters on complementary metal-oxide-semiconductor compatible silicon chips for wide-ranging applications. PMID:23087243

Cai, Xinlun; Wang, Jianwei; Strain, Michael J; Johnson-Morris, Benjamin; Zhu, Jiangbo; Sorel, Marc; O'Brien, Jeremy L; Thompson, Mark G; Yu, Siyuan

2012-10-19

347

The Breakdown of Compressible Vortex Flows  

NASA Astrophysics Data System (ADS)

The theoretical foundation for the global analysis of the dynamics of vortex flows is extended to the case of subsonic compressible swirling flows in a finite-length, straight, circular pipe. A novel nonlinear partial differential equation for the solution of the flow stream function is developed in terms of the incoming specific total enthalpy, specific entropy, and circulation functions. Solutions of the resulting nonlinear ordinary differential equation for the columnar case together with a newly derived flow-force condition describe the flow outlet state. These solutions are used to form the bifurcation diagrams of steady, compressible flows with swirl as the swirl level is increased. These provide theoretical predictions of the critical swirl ratio for the first appearance of vortex breakdown as function of Mach number.

Rusak, Zvi; Choi, Jung J.

2008-11-01

348

A broad-band scalar vortex coronagraph  

NASA Astrophysics Data System (ADS)

Broad-band coronagraphy with deep nulling and small inner working angle has the potential of delivering images and spectra of exoplanets and other faint objects. In recent years, many coronagraphic schemes have been proposed, the most promising being the optical vortex phase mask coronagraphs. In this paper, a new scheme of broad-band optical scalar vortex coronagraph is proposed and characterized experimentally in the laboratory. Our setup employs a pair of computer-generated phase gratings (one of them containing a singularity) to control the chromatic dispersion of phase plates and achieves a constant peak-to-peak attenuation below 1 × 10-3 over a bandwidth of 120 nm centred at 700 nm. An inner working angle of ˜?/D is demonstrated along with a raw contrast of 11.5 mag at 2?/D.

Errmann, R.; Minardi, S.; Pertsch, T.

2013-10-01

349

Geometric symmetries in superfluid vortex dynamics  

SciTech Connect

Dynamics of quantized vortex lines in a superfluid feature symmetries associated with the geometric character of the complex-valued field, w(z)=x(z)+iy(z), describing the instant shape of the line. Along with a natural set of Noether's constants of motion, which - apart from their rather specific expressions in terms of w(z) - are nothing but components of the total linear and angular momenta of the fluid, the geometric symmetry brings about crucial consequences for kinetics of distortion waves on the vortex lines, the Kelvin waves. It is the geometric symmetry that renders Kelvin-wave cascade local in the wave-number space. Similar considerations apply to other systems with purely geometric degrees of freedom.

Kozik, Evgeny [Institute for Theoretical Physics, ETH Zurich, CH-8093 Zurich (Switzerland); Svistunov, Boris [Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Russian Research Center 'Kurchatov Institute', 123182 Moscow (Russian Federation)

2010-10-01

350

Vortex flow for a holographic superconductor  

SciTech Connect

We investigate energy dissipation associated with the motion of the scalar condensate in a holographic superconductor model constructed from the charged scalar field coupled to the Maxwell field. Upon application of constant magnetic and electric fields, we analytically construct the vortex-flow solution and find the vortex-flow resistance near the second-order phase transition where the scalar condensate begins. The characteristic feature of the nonequilibrium state agrees with the one predicted by the time-dependent Ginzburg-Landau (TDGL) theory. We evaluate the kinetic coefficient in the TDGL equation along the line of the second-order phase transition. At zero magnetic field, the other coefficients in the TDGL equation are also evaluated just below the critical temperature.

Maeda, Kengo; Okamura, Takashi [Faculty of Engineering, Shibaura Institute of Technology, Saitama, 330-8570 (Japan); Department of Physics, Kwansei Gakuin University, Sanda, 669-1337 (Japan)

2011-03-15

351

Optical Vortex Generation from Molecular Chromophore Arrays  

NASA Astrophysics Data System (ADS)

The generation of light endowed with orbital angular momentum, frequently termed optical vortex light, is commonly achieved by passing a conventional beam through suitably constructed optical elements. This Letter shows that the necessary phase structure for vortex propagation can be directly produced through the creation of twisted light from the vacuum. The mechanism is based on optical emission from a family of chromophore nanoarrays that satisfy specific geometric and symmetry constraints. Each such array can support pairs of electronically delocalized doubly degenerate excitons whose azimuthal phase progression is responsible for the helical wave front of the emitted radiation. The exciton symmetry dictates the maximum magnitude of topological charge; detailed analysis secures the conditions necessary to deliver optical vortices of arbitrary order.

Williams, Mathew D.; Coles, Matt M.; Saadi, Kamel; Bradshaw, David S.; Andrews, David L.

2013-10-01

352

Stationary vortex sheets in a stirring flow  

NASA Astrophysics Data System (ADS)

Stationary vortex sheets in a two-dimensional stirring flow may be approximated by arrays of stationary point vortices arranged along the support of the sheets. These vortices lie at the roots of a polynomial that satisfies a generalized Lamé differential equation; the polynomial itself (not the roots) determines the complex potential and stream function. In this paper, sufficient conditions for the stirring flow are found so that the differential equation has two independent polynomial solutions with simple closed-form expressions, analogous to hypergeometric polynomials. The corresponding point vortex array then depends on a complex parameter that controls the location of the sheet, so that it may pass through any selected point. Stationary sheets in a periodic flow are approximated by the same method.

O'Neil, Kevin A.

2013-11-01

353

Vortex Domains in Ferroelectric Nano-Structures  

NASA Astrophysics Data System (ADS)

Recently the study of submicron-diameter ferroelectric disks and squares and rectangles fabricated from films of ca. 100-300 nm thick have revealed usual domain patterns, qualitatively different from the stripe domains commonly studied in macroscopic specimens in the past. These include doughnut-shaped domains, four-fold vertex closure domains, and fractal domains. The static configurations offer a variety of puzzles, and the structures differ from those in magnetic vortex domains, presumably due to the much larger anisotropy in ferroelectrics, which generally prohibits true vortex configurations with polarization forced out of plane. The dynamics also differ qualitatively from early studies: For decades ferroelectrics were thought to be highly Ising-like, but recent data and theoretical simulations favor Bloch walls and more Heisenberg-like kinetics. This talk will include data from Alina Schilling and Marty Gregg in Belfast, Marin Alexe in Halle, and modeling from Hlinka and Marton in Prague and Bellaiche and Prosandeev in Arkansas.

Scott, James F.

2011-03-01

354

Deterministic Josephson vortex ratchet with a load.  

PubMed

We investigate experimentally a deterministic underdamped Josephson vortex ratchet-a fluxon particle moving along a Josephson junction in an asymmetric periodic potential. By applying a sinusoidal driving current, one can compel the vortex to move in a certain direction, producing an average dc voltage across the junction. Being in such a rectification regime, we also load the ratchet, i.e., apply an additional dc bias current I(dc) (counterforce) which tilts the potential so that the fluxon climbs uphill due to the ratchet effect. The value of the bias current at which the fluxon stops climbing up defines the strength of the ratchet effect and is determined experimentally. This allows us to estimate the loading capability of the ratchet, the output power, and the efficiency. For the quasistatic regime we present a simple model which delivers straightforward analytic expressions for the above-mentioned figures of merit. PMID:22400527

Knufinke, M; Ilin, K; Siegel, M; Koelle, D; Kleiner, R; Goldobin, E

2012-01-13

355

Holographic vortex liquids and superfluid turbulence.  

PubMed

Superfluid turbulence is a fascinating phenomenon for which a satisfactory theoretical framework is lacking. Holographic duality provides a systematic approach to studying such quantum turbulence by mapping the dynamics of a strongly interacting quantum liquid into the dynamics of classical gravity. We use this gravitational description to numerically construct turbulent flows in a holographic superfluid in two spatial dimensions. We find that the superfluid kinetic energy spectrum obeys the Kolmogorov -5/3 scaling law, with energy injected at long wavelengths undergoing a direct cascade to short wavelengths where dissipation by vortex annihilation and vortex drag becomes efficient. This dissipation has a simple gravitational interpretation as energy flux across a black hole event horizon. PMID:23888034

Chesler, Paul M; Liu, Hong; Adams, Allan

2013-07-26

356

Point vortex dynamics: Recent results and open problems  

SciTech Connect

The concept of point vortex motion, a classical model in the theory of two-dimensional, incompressible fluid mechanics, was introduced by Helmholtz in 1858. Exploration of the solutions to these equations has made fitful progress since that time as the point vortex model has been brought to bear on various physical situations: atomic structure, large-scale weather patterns, ''vortex street'' wakes, vortex lattices in superfluids and superconductors, etc. The point vortex equations also provide an interesting example of transition to chaotic behavior. We give a brief historical introduction to these topics and develop two of them in particular to the point of current understanding: steadily moving configurations of point vortices; and collision dynamics of vortex pairs. 26 refs.

Aref, H.; Kadtke, J.B.; Zawadzki, I.; Campbell, L.J.; Eckhardt, B.

1987-01-01

357

Dynamics of vortex nucleation in nanomagnets with broken symmetry  

NASA Astrophysics Data System (ADS)

We investigate the dynamics of magnetic vortex nucleation in sub-100-nm mesoscopic magnets with the aim of establishing an independent control of vortex polarity and chirality. We consider the dynamic behavior of the vortex spin structure in an object with broken symmetry—a Pacman-like nanomagnet shape—proposing a model based on classical electrodynamics and providing a proof by conducting micromagnetic calculations. The model provides evidence that the desired vortex chirality and polarity could be established by applying solely quasistatic in-plane magnetic field along specific directions with respect to the structure's asymmetry. We identify the modes of vortex nucleation that are robust against external magnetic field noise. These vortex nucleation modes are common among a wide range of sub-100-nm magnets with broken rotational symmetry. The results could lead to the practical realization of high density magnetic memories based on magnetic vortices.

Tóbik, Jaroslav; Cambel, Vladimír; Karapetrov, Goran

2012-10-01

358

Numerical simulation of shock-vortex interaction in Schardin's problem  

NASA Astrophysics Data System (ADS)

Shock diffraction over a two-dimensional wedge and subsequent shock-vortex interaction have been numerically simulated using the AUSM scheme. After the passage of the incident shock over the wedge, the generated tip vortex interacts with a reflected shock. The resulting shock pattern has been captured well. It matches the existing experimental and numerical results reported in the literature. We solve the Navier-Stokes equations using high accuracy schemes and extend the existing results by focussing on the Kelvin-Helmholtz instability generated vortices which follow a spiral path to the vortex core and on their way interact with shock waves embedded within the vortex. Vortex detection algorithms have been used to visualize the spiral structure of the initial vortex and its final breakdown into a turbulent state. Plotting the dilatation field we notice a new source of diverging acoustic waves and a lambda shock at the wedge tip.

Halder, P.; De, S.; Sinhamahapatra, K. P.; Singh, N.

2013-09-01

359

Vortex tube can increase liquid hydrocarbon recovery at plant inlet  

SciTech Connect

Use of a vortex-tube device yields improved inlet gas-liquid separation, when compared with a Joule-Thomson system, but is less costly and complex than a true isentropic system, such as a turboexpander. Because the vortex-tube unit provides separation as well as pressure reduction, the capital cost of a Joule-Thomson system with valve and separator will be similar to that of the vortex-tube system. Future applications of vortex-tube units will be concentrated where performance improvements over Joule-Thomson units, at low capital cost, are required. The operating characteristics of a vortex tube permit gas, in part, to be reduced in temperature to less than that normally achievable through isenthalpic expansion. The following three examples show how vortex technology can be applied to achieve these aims.

Hajdik, B. [CBS Engineering Inc., Houston, TX (United States); Lorey, M. [Filtan Anlagenbau GmbH, Langenselbold (Germany); Steinle, J. [BEB Erdoel and Erdgas GmbH, Hannover (Germany); Thomas, K. [Falk and Thomas Engineering GmbH, Wettenberg (Germany)

1997-09-08

360

Effective Magnus Force on a Magnetic Vortex  

Microsoft Academic Search

In classical hydrodynamics, a Magnus force exists between a vortex and the hosting fluid acting transverse to their relative\\u000a motion. There is a quantum Magnus force acting on vortices in superfluids and superconductors and an analogous force acting\\u000a on magnetic vortices excited in spin systems. Couplings with the system quasiparticles can modify this to an effective Magnus\\u000a force by introducing

L. R. Thompson; P. C. E. Stamp

361

Vortex ring modelling of toroidal bubbles  

Microsoft Academic Search

During the collapse of a bubble near a surface, a high-speed liquid jet often forms and subsequently impacts upon the opposite\\u000a bubble surface. The jet impact transforms the originally singly-connected bubble to a toroidal bubble, and generates circulation\\u000a in the flow around it. A toroidal bubble simulation is presented by introducing a vortex ring seeded inside the bubble torus\\u000a to

Q. X. Wang; K. S. Yeo; B. C. Khoo; K. Y. Lam

2005-01-01

362

Vortex bubble formation in pair plasmas.  

PubMed

It is shown that delocalized vortex solitons in relativistic pair plasmas with small temperature asymmetries can be unstable for intermediate intensities of the background electromagnetic field. Instability leads to the generation of ever-expanding cavitating bubbles in which the electromagnetic fields are zero. The existence of such electromagnetic bubbles is demonstrated by qualitative arguments based on a hydrodynamic analogy, and by numerical solutions of the appropriate nonlinear Schrödinger equation with a saturating nonlinearity. PMID:23944600

Berezhiani, V I; Shatashvili, N L; Mahajan, S M; Aleksi?, B N

2013-07-18

363

A VORTEX PARTICLE METHOD FOR COMPRESSIBLE FLOWS  

Microsoft Academic Search

A vortex particle method for the simulation of two- dimensional compressible flows is developed. The computational elements are Lagrangian particles that carry vorticity,dilatation,enthalpy,entropy and density. The velocity field is decomposed into irrotational and solenoidal parts,which allows its calculation in terms of the particles' vorticity and dilatation. The particle coverage is truncated and incident acoustic waves are absorbed using a suitable

Jeff Eldredge; Tim Colonius; Anthony Leonard

2001-01-01

364

Vortex shedding from solid rocket propellant inhibitors  

Microsoft Academic Search

Vortex shedding frequency caused by the protrusion of inhibitors into the flow field of a solid rocket motor is investigated by experimental and mathematical models. The time dependent Navier-Stokes equations are solved using a finite difference technique assuming incompressible, two-dimensional flow under both laminar and turbulent flow conditions. For laminar flow, explicit solutions are obtained using a vorticity-transport equation in

P. H. Shu; R. H. Sforzini; W. A. Foster Jr.

1986-01-01

365

Evolution of Vortex Rings Exiting Inclined Cylinders  

NASA Astrophysics Data System (ADS)

Vortex rings initiated in cylinders with exit incline lengths of 0, D/4, and D/2 were investigated for Reynolds numbers up to 30,000. The fluid exiting each cylinder was visualized with an ionized bromothymol blue solution, and velocity fields were obtained with PIV. In each inclined case, vortex rings form at angles smaller than the cylinder incline angle. Entrainment of ambient fluid on the short side of the cylinder is much stronger than that on the long side. This results in a larger circulation about the short side of the ring and a greater propagation velocity on that side. The incline angle of the ring thus decreases as it moves downstream. Behind the ring core, an impulsive wave of entrained ambient fluid flows parallel to the cylinder exit plane. Some of this fluid is wrapped into the core, while the rest is ejected outward past the long cylinder edge. The vortex ring dynamics differ significantly from those observed in jets from inclined nozzles where neighboring rings are connected by straining zones, and ring incline angles increase with downstream distance.

Longmire, E. K.; Webster, D. R.; Reetz, M.; Gefroh, D.

1996-11-01

366

Numerical Validation of Quasigeostrophic Ellipsoidal Vortex Model  

NASA Astrophysics Data System (ADS)

In geophysical flows, coherent vortex structures persist for long time and their interactions dominate the dynamics of geophysical turbulence. Meacham et al. obtained a series of exact unsteady solution of the quasigeostrophic equation, which represents a uniform ellipsoidal vortex patch embedded in a uniform 3D shear field. Miyazaki et al. derived a Hamiltonian dynamical system describing the interactions of N ellipsoidal vortices, where each coherent vortex was modeled by an ellipsoid of uniform potential vorticity. In this paper, direct numerical simulations based on a Contour Advective Semi-Lagrangian algorithm (CASL) are performed in order to assess the validity of the Hamiltonian model. First, the instability of a tilted spheroid is investigated. A prolate spheroid becomes unstable against the third Legendre mode when the aspect ratio is less than 0.44 and the inclination angle is larger than 0.48. Weakly unstable flatter spheroidal vortices emit thin filaments from their top and bottom, whereas strongly ustable slender spheriodal vortices are broken up into two pieces. Secondly, the interaction of two co-rotaing spheroidal vortices on slightly different vertical levels is studied in detail. It is shown that the Hamiltonian model can predict the critical merger distance fairly well. Considerable amounts of energy and enstrophy are dissipated in these events. The correlation between the energy dissipation and the enstrophy dissipation is good, suggesting the existence of a deterministic reset-rule.

Miyazaki, Takeshi; Asai, Akinori; Yamamoto, Masahiro; Fujishima, Shinsuke

2002-11-01

367

Vortex jamming in superconductors and granular rheology  

NASA Astrophysics Data System (ADS)

We demonstrate that a highly frustrated anisotropic Josephson junction array (JJA) on a square lattice exhibits a zero-temperature jamming transition, which shares much in common with those in granular systems. Anisotropy of the Josephson couplings along the horizontal and vertical directions plays roles similar to normal load or density in granular systems. We studied numerically static and dynamic response of the system against shear, i.e. injection of external electric current at zero temperature. Current-voltage curves at various strength of the anisotropy exhibit universal scaling features around the jamming point much as do the flow curves in granular rheology, shear-stress versus shear-rate. It turns out that at zero temperature the jamming transition occurs right at the isotropic coupling and anisotropic JJA behaves as exotic fragile vortex matter: it behaves as a superconductor (vortex glass) in one direction, whereas it is a normal conductor (vortex liquid) in the other direction even at zero temperature. Furthermore, we find a variant of the theoretical model for the anisotropic JJA quantitatively reproduces universal master flow-curves of the granular systems. Our results suggest an unexpected common paradigm stretching over seemingly unrelated fields—the rheology of soft materials and superconductivity.

Yoshino, Hajime; Nogawa, Tomoaki; Kim, Bongsoo

2009-01-01

368

Sediment resuspension and erosion by vortex rings  

NASA Astrophysics Data System (ADS)

Particle resuspension and erosion induced by a vortex ring interacting with a sediment layer was investigated experimentally using flow visualization (particle image velocimetry), high-speed video, and a recently developed light attenuation method for measuring displacements in bed level. Near-spherical sediment particles were used throughout with relative densities of 1.2-7 and diameters (d) ranging between 90 and 1600 ?m. Attention was focused on initially smooth, horizontal bedforms with the vortex ring aligned to approach the bed vertically. Interaction characteristics were investigated in terms of the dimensionless Shields parameter, defined using the vortex-ring propagation speed. The critical conditions for resuspension (whereby particles are only just resuspended) were determined as a function of particle Reynolds number (based on the particle settling velocity and d). The effects of viscous damping were found to be significant for d/?<15, where ? denotes the viscous sublayer thickness. Measurements of bed deformation were obtained during the interaction period, for a range of impact conditions. The (azimuthal) mean crater profile is shown to be generally self-similar during the interaction period, except for the most energetic impacts and larger sediment types. Loss of similarity occurs when the local bed slope approaches the repose limit, leading to collapse. Erosion, deposition, and resuspension volumes are analyzed as a function interaction time, impact condition, and sediment size.

Munro, R. J.; Bethke, N.; Dalziel, S. B.

2009-04-01

369

Vortex ring refraction at large Froude numbers  

NASA Astrophysics Data System (ADS)

We have experimentally studied the impact of an initially planar axisymmetric vortex ring, incident at an oblique angle, upon a gravity-induced interface separating two fluids of differing densities. After impact, the vortex ring was found to exhibit a variety of subsequent trajectories, which we organize according to both the incidence angle, ?i , and the interface strength, defined as the ratio of the Atwood and Froude numbers, A/F . For grazing incidence angles (?i?70°) vortices either penetrate or reflect from the interface, depending on whether the interface is weak or strong. In some cases, reflected vortices execute damped oscillations before finally disintegrating. For smaller incidence angles (?i?70°) vortices penetrate the interface. When there is a strong interface, these vortices are observed to curve back up toward the interface. When there is a weak interface, these vortices are observed to refract downward, away from the interface. The critical interface strength below which vortex ring refraction is observed is given by log10(A/F)=-2.38±0.05 .

Kuehn, Kerry; Moeller, Matthew; Schulz, Michael; Sanfelippo, Daniel

2010-07-01

370

Vortex ring refraction at large Froude numbers  

NASA Astrophysics Data System (ADS)

We have experimentally studied the impact of an initially planar axisymmetric vortex ring, incident at an oblique angle, upon a gravity-induced interface separating two fluids of differing densities. After impact, the vortex ring was found to exhibit a variety of subsequent trajectories, which we organize according to both the incidence angle, ?i, and the interface strength, defined as the ratio of the Atwood and Froude numbers, A/F. For grazing incidence angles (?i70 deg.) vortices either penetrate or reflect from the interface, depending on whether the interface is weak or strong. In some cases, reflected vortices execute damped oscillations before finally disintegrating. For smaller incidence angles (?i70 deg.) vortices penetrate the interface. When there is a strong interface, these vortices are observed to curve back up toward the interface. When there is a weak interface, these vortices are observed to refract downward, away from the interface. The critical interface strength below which vortex ring refraction is observed is given by 10(A/F)= -2.38 ±0.05.

Kuehn, Kerry; Moeller, Matthew; Schulz, Michael; Sanfelippo, Daniel

2010-11-01

371

Evolution of Vortex Sheets in a Channel  

NASA Astrophysics Data System (ADS)

The nonlinear flow is considered which results when two immiscible inviscid incompressible fluids of different densities and velocities separated by an interface which is free to move and which supports surface tension, are caused to flow in a straight infinite channel. The approach involves the derivation of model evolution equations for the interface and velocity jump across the interface using long-wave asymptotics and the ensuing analysis and computation of these models. When surface tension is absent it is shown that the system of governing evolution equations terminates in a singularity after a finite time. This is achieved by studying a 2 x 2 system of nonlinear conservation laws in the complex plane and by numerical solution of the evolution equations. The vortex-sheet formulation of the exact nonlinear two-dimensional flow of a vortex sheet which is bounded in a channel is also considered. An appropriate Birkhoff-Rott type integro-differential evolution equation for two-phase inviscid flows in channels of arbitrary aspect ratios is derived. For the case of a spatially periodic vortex sheet, this Birkhoff-Rott type equation is written in terms of Jacobi's functions. The equation is shown to recover the limits of unbounded and non-periodic flows which are known in the literature.

Barannyk, Lyudmyla; Papageorgiou, Demetrius

2003-11-01

372

Tip vortex cavitation suppression via mass injection  

NASA Astrophysics Data System (ADS)

Tip vortex cavitation (TVC) suppression by mass injection in the core of the vortex was studied with an elliptical plan-form hydrofoil NACA-66 modified in a re-circulating water tunnel of known nuclei distribution. The chord based Re was O(106) for all experiments. Water and Polyox WSR 301 solution for a range of concentrations (10 to 500pmm) and relative flow rates (Qjet / Qcore of 0.033 to 0.27) were injected. Also, different injection port size and angle of attack were studied. It was found that the TVC suppression effect was different for inception and desinence. The baseline (no injection) inception cavitation number was more than the average negative pressure coefficient, -Cp of the vortex, while mass addition reduced the inception cavitation number to approximately the --Cp value. TVC desinence for the baseline case was found to match the estimated --Cp value and polymer injection provided some cavitation suppression. Flow measurements were made to understand the underlying physics of TVC. The mechanisms and scalability that lead to TVC suppression by mass injection are discussed.

Ganesh, Harish; Chang, Natasha; Yakushiji, Ryo; Ceccio, Steven

2009-11-01

373

a Laboratory Investigation of Two-Celled Vortex Flows  

Microsoft Academic Search

An experimental study of the steady-state kinematics, dynamics, and morphology of two-celled vortex flows has been conducted in the Ward-type tornado vortex chamber (TVC) at Purdue University, with emphasis on exploring the vertical momentum balance in the vortex core and better defining the flow near the external boundaries of the TVC. The TVC was modified for these experiments to more

Randal Lee Pauley

1986-01-01

374

An inviscid model for vortex shedding from a deforming body  

Microsoft Academic Search

An inviscid vortex sheet model is developed in order to study the unsteady separated flow past a two-dimensional deforming\\u000a body which moves with a prescribed motion in an otherwise quiescent fluid. Following Jones (J Fluid Mech 496, 405–441, 2003)\\u000a the flow is assumed to comprise of a bound vortex sheet attached to the body and two separate vortex sheets originating

Ratnesh K. Shukla; Jeff. D. Eldredge

2007-01-01

375

A review on design criteria for vortex tubes  

Microsoft Academic Search

In this study, the past investigations of the design criteria of vortex tubes were overviewed and the detailed information\\u000a was presented on the design of them. Vortex tubes were classified and the type of them was described. All criteria on the\\u000a design of vortex tubes were given in detail using experimental and theoretical results from the past until now. Finally,

M. Yilmaz; M. Kaya; S. Karagoz; S. Erdogan

2009-01-01

376

Electric spectroscopy of vortex states and dynamics in magnetic disks  

NASA Astrophysics Data System (ADS)

Spin-polarized radio frequency (RF) currents and RF-Oersted fields resonantly excite a magnetic vortex core confined in a micron-scale soft magnetic disk. In this study, we measured the rectifying voltage spectra caused by the anisotropic magnetoresistance oscillation due to the gyration of the vortex with different polarity and chirality. The measured spectra are presented such that we can determine the vortex properties and strength of the spin torques and Oersted field accurately and directly through analytical calculation.

Goto, Minori; Hata, Hiroshi; Yamaguchi, Akinobu; Nakatani, Yoshinobu; Yamaoka, Takehiro; Nozaki, Yukio; Miyajima, Hideki

2011-08-01

377

A Vortex Method for Turbulent Flow Simulation, With Applications  

Microsoft Academic Search

A vortex method specifically designed for turbulent flow modeling and simulation has been implemented in the VORCAT code (see www.vorcat.com). Computational elements consist of straight vortex tubes combined to form filaments and finite thickness, thin, unstructured, triangular vortex sheets several layers deep covering solid surfaces. The latter efficiently resolve steep vorticity gradients in the near-wall region and permit accurate evaluation

Peter Bernard; Athanassios Dimas; Isaac Lottati

2000-01-01

378

Double-well potential for a Josephson vortex qubit  

Microsoft Academic Search

The prospect of designing a vortex qubit is analyzed theoretically by studying the classical dynamics of a vortex in a double-well potential created in a semiannular Josephson junction. A vortex in a double-well potential behaves like a particle in a two-level system and can be a candidate for a qubit. Tunability of the double-well potential inside a semiannular Josephson junction

P. D. Shaju; V. C. Kuriakose

2005-01-01

379

Vortex-wave interaction on the surface of a sphere  

Microsoft Academic Search

The time-dependent interaction of a point vortex with a vorticity jump separating regions of opposite signed and constant vorticities on the surface of a non-rotating sphere is examined. First, small amplitude interfacial waves are considered where linear theory is applicable. A point vortex in a region of same-signed vorticity will initially move away from the interface and a point vortex

Rhodri B. Nelson; N. Robb McDonald

2011-01-01

380

Edge barrier pinning for a single superconducting vortex  

NASA Astrophysics Data System (ADS)

Thermal depinning of a single vortex trapped in a superconducting thin film has been measured in order to study the Bean-Livingston surface barrier. There are two forces that bias the motion of the vortex in the natural pinning potential of the film. These are the image force pulling the vortex toward the edge of the film and the Lorentz force of the Meissner currents pushing the vortex toward the center of the film. With zero applied magnetic field, a vortex trapped in a clean, well-defined junction will begin to spontaneously move over large distances of 1 ?m or more at a temperature where the reduced order parameter is about ?/?0=0.2. When ?/?0 has been further reduced to ?/?0=0.15, the vortex exits the film, giving a vortex-free state below Tc. In zero applied field, the data show that the image force clearly causes a trapped vortex to leave the film. When a perpendicular magnetic field is applied, however, results show that new vortices were nucleated for fields higher than 20 mG. At 20 mG, the Meissner current force was only a few percent of the pinning force and this biasing force causes the vortex to exit the film at a temperature 0.050 K lower than in zero field.

Kouzoudis, D.; Breitwisch, M.; Finnemore, D. K.

1999-10-01

381

Novel Vortex Generator and Mode Converter for Electron Beams  

NASA Astrophysics Data System (ADS)

A mode converter for electron vortex beams is described. Numerical simulations, confirmed by experiment, show that the converter transforms a vortex beam with a topological charge m=±1 into beams closely resembling Hermite-Gaussian HG10 and HG01 modes. The converter can be used as a mode discriminator or filter for electron vortex beams. Combining the converter with a phase plate turns a plane wave into modes with topological charge m=±1. This combination serves as a generator of electron vortex beams of high brilliance.

Schattschneider, P.; Stöger-Pollach, M.; Verbeeck, J.

2012-08-01

382

Confinement and center vortex dynamics in different gauge groups  

SciTech Connect

The random vortex world-surface model is extended to the gauge groups SU(4) and Sp(2). Compared to the SU(2) and SU(3) models studied previously, which reproduce the infrared properties of the corresponding Yang-Mills theories on the basis of a simple vortex world-surface curvature action, new dynamical characteristics become important. In the SU(4) case, an explicit dependence of the vortex effective action on the configuration of the Abelian magnetic monopoles residing on the vortices emerges; in the Sp(2) case, a new 'stickiness' contribution to the vortex action serves to drive the deconfinement phase transition towards the correct first-order behavior.

Engelhardt, M.; Sperisen, B. [Department of Physics, New Mexico State University, Las Cruces, NM 88003 (United States)

2007-02-27

383

Magnetic vortex dynamics induced by spin-transfer torque  

NASA Astrophysics Data System (ADS)

We theoretically study the dynamics of a magnetic vortex under spin-polarized electric current in ferromagnets. The equation of motion of the vortex in terms of collective coordinates is derived. We compare our theory with recent experiments for current-induced vortex displacement and resonance motion in a ferromagnetic nanodot. Our estimate for the displacement and the resonance frequency shows a good agreement with the experiment. We also study the current-induced motion of a vortex wall in a ferromagnetic thin wire.

Shibata, J.; Nakatani, Y.; Tatara, G.; Kohno, H.; Otani, Y.

2007-03-01

384

Investigation of the wingtip vortex behind an oscillating airfoil  

NASA Astrophysics Data System (ADS)

The near-field flow structure of the tip vortex generated by a NACA 0015 wing oscillating though the attached-flow, light-stall and deep-stall regimes was investigated at Rec = 1.86 x 105. Particular emphasis was placed on the effects of oscillation frequency and mean incidence upon the spatial and temporal evolution of the unsteady vortex structure. Phase-locked, ensemble-averaged cross-flow and axial velocity fields, vorticity distributions, and turbulence structures over a full cycle of oscillation were compared to static wing-tip vortex results, and the dynamic effects upon the vortex strength, size, trajectory and associated induced drag were examined. Through the attached-flow and light-stall oscillations, most vortex properties were qualitatively similar to the static cases, though a small degree of hysteresis between the pitch-up and pitch-down phases of motion was observed. The radial distributions of circulation within the inner region of the vortex were self-similar, and showed only small variations from the static case. When the wing was oscillated through the deep-stall regime, a dramatic decrease in tip vortex strength and concentration was observed at the end of the upstroke, as a result of the growth of the leading-edge vortex and subsequent catastrophic flow separation. The use of passive spoilers and active flaps to control the strength and trajectory of the tip vortex was also investigated.

Birch, David M.

385

Edge barrier pinning for a single superconducting vortex  

SciTech Connect

Thermal depinning of a single vortex trapped in a superconducting thin film has been measured in order to study the Bean-Livingston surface barrier. There are two forces that bias the motion of the vortex in the natural pinning potential of the film. These are the image force pulling the vortex toward the edge of the film and the Lorentz force of the Meissner currents pushing the vortex toward the center of the film. With zero applied magnetic field, a vortex trapped in a clean, well-defined junction will begin to spontaneously move over large distances of 1 {mu}m or more at a temperature where the reduced order parameter is about {Delta}/{Delta}{sub 0}=0.2. When {Delta}/{Delta}{sub 0} has been further reduced to {Delta}/{Delta}{sub 0}=0.15, the vortex exits the film, giving a vortex-free state below T{sub c}. In zero applied field, the data show that the image force clearly causes a trapped vortex to leave the film. When a perpendicular magnetic field is applied, however, results show that new vortices were nucleated for fields higher than 20 mG. At 20 mG, the Meissner current force was only a few percent of the pinning force and this biasing force causes the vortex to exit the film at a temperature 0.050 K lower than in zero field. {copyright} {ital 1999} {ital The American Physical Society}

Kouzoudis, D.; Breitwisch, M.; Finnemore, D.K. [Ames Laboratory, USDOE and Department of Physics, Iowa State University, Ames, Iowa 50011 (United States)

1999-10-01

386

Note: a simple experimental arrangement to generate optical vortex beams.  

PubMed

In this Note, we present a simple experimental arrangement to generate optical vortex beams. We have demonstrated how by taking print of an interferogram on a transparent sheet, vortex beams with various topological charges can be generated. Experimental results show that the vortex beam indeed carries the topological charge that is used to compute the interferograms. In addition to being simple and inexpensive, one major advantage of the arrangement is that it makes it possible to generate different vortex beams quickly, unlike using the photographic process to create the holograms. PMID:23464265

Kumar, Dhirendra; Das, Abhijit; Boruah, Bosanta R

2013-02-01

387

Generation of programmable 3D optical vortex structures through devil's vortex-lens arrays.  

PubMed

Different spatial distributions of optical vortices have been generated and characterized by implementing arrays of devil's vortex lenses in a reconfigurable spatial light modulator. A simple design procedure assigns the preferred position and topological charge value to each vortex in the structure, tuning the desired angular momentum. Distributions with charges and momenta of the opposite sign have been experimentally demonstrated. The angular velocity exhibited by the phase distribution around the focal plane has been visualized, showing an excellent agreement with the simulations. The practical limits of the method, with interest for applications involving particle transfer and manipulation, have been evaluated. PMID:23938437

Calabuig, Alejandro; Sánchez-Ruiz, Sergio; Martínez-León, Lluís; Tajahuerce, Enrique; Fernández-Alonso, Mercedes; Furlan, Walter D; Monsoriu, Juan A; Pons-Martí, Amparo

2013-08-10

388

Development of a vortex combustor (VC) for space\\/water heating applications (cold flow modeling)  

Microsoft Academic Search

This report focuses on the discussion of cold flow measurements and mathematical modeling of the vortex combustor (VC). A parallel research project on the combustion tests of a 2-4 MB\\/H proof-of- concept VC has been conducted by the Naval Civil Engineering Laboratory. This final report is divided into seven chapters: Chapter 1 discusses the concept and advantages of the VC,

Nieh

1990-01-01

389

Development of a Dynamically Scaled Generic Transport Model Testbed for Flight Research Experiments  

Microsoft Academic Search

This paper details the design and development of the Airborne Subscale Transport Aircraft Research (AirSTAR) test-bed at NASA Langley Research Center (LaRC). The aircraft is a 5.5% dynamically scaled, remotely piloted, twin-turbine, swept wing, Generic Transport Model (GTM) which will be used to provide an experimental flight test capability for research experiments pertaining to dynamics modeling and control beyond the

Thomas Jordan; William Langford; Christine Belcastro; John Foster; Gautam Shah; Gregory Howland; Reggie Kidd

390

Guiding-center dynamics of vortex dipoles in Bose-Einstein condensates  

SciTech Connect

A quantized vortex dipole is the simplest vortex molecule, comprising two countercirculating vortex lines in a superfluid. Although vortex dipoles are endemic in two-dimensional superfluids, the precise details of their dynamics have remained largely unexplored. We present here several striking observations of vortex dipoles in dilute-gas Bose-Einstein condensates, and develop a vortex-particle model that generates vortex line trajectories that are in good agreement with the experimental data. Interestingly, these diverse trajectories exhibit essentially identical quasiperiodic behavior, in which the vortex lines undergo stable epicyclic orbits.

Middelkamp, S.; Schmelcher, P. [Zentrum fuer Optische Quantentechnologien, Universitaet Hamburg, Luruper Chaussee 149, DE-22761 Hamburg (Germany); Torres, P. J. [Departamento de Matematica Aplicada, Universidad de Granada, ES-18071 Granada (Spain); Kevrekidis, P. G. [Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003-4515 (United States); Frantzeskakis, D. J. [Department of Physics, University of Athens, Panepistimiopolis, Zografos, Athens 157 84 (Greece); Carretero-Gonzalez, R. [Nonlinear Dynamical System Group, Computational Science Research Center and Department of Mathematics and Statistics, San Diego State University, San Diego, California 92182-7720 (United States); Freilich, D. V.; Hall, D. S. [Department of Physics, Amherst College, Amherst, Massachusetts 01002-5000 (United States)

2011-07-15

391

Numerical Investigation of the Influence of Spanwise Force Variation in Circular Cylinders Undergoing Vortex Induced Vibrations at High Reynolds Number  

Microsoft Academic Search

The focus of this research is on the development of a new approach for simulating vortex induced vibrations on marine risers at high Reynolds numbers. This method considers the span-wise variation of the lift and drag forces, and determines the moment acting on the cylinder. The predicted motion then consists of a rotational component to accompany the traditional cross-stream and

David Murrin; Julio Militzer; N. Bose; R. Campregher

2007-01-01

392

Controlling vortex pinning and vortex phase diagrams of FeAs-based superconductors through particle irradiation and substitution  

NASA Astrophysics Data System (ADS)

The prominent vortex pinning features of the Ba-122 and Sm-1111 family of pnictide superconductors are presented. For isovalently doped BaFe2(As1-xPx)2 we observe the systematic evolution of vortex pinning with increasing P-doping from fishtail behavior to a distinct peak effect near the irreversibility field to a reversible magnetization and Bean Livingston surface barriers. The enhancement of vortex pinning resulting from heavy ion and proton irradiation is shown to arise from delta-Tc-type pinning. These results will be compared to those on optimal doped BaKFe2As2 and SmFeAs(O1-xFx). High-energy heavy-ion irradiation induced defects lead to a decrease in the superconducting anisotropy, an increase in the slope of the temperature dependence of the irreversibility line and only small suppression of Tc. In all cases, we see a large enhancement of the critical current following particle irradiation. In particular, on BaKFe2As2 irradiated to a dose matching field of 21 T with 1.3-GeV Pb-ions, Jc ˜ 4 MA/cm^2 at 5 K and in 7 T || c is achieved, comparable to results for YBCO coated conductors at the same temperature and field.[4pt] In collaboration with L. Fang, Y. Jia, J. A. Schlueter, H. Claus, C. Chaparro, G. Sheet, A. E. Koshelev, G. W. Crabtree, W. K. Kwok, Materials Science Division, Argonne National Laboratory, Argonne, Illinois, USA; S. F. Xu, Physics Division, Argonne National Laboratory, Argonne, Illinois, USA; H. F. Hu, J. M. Zuo, Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois, USA; A. Kayani, Physics Department, Western Michigan University, Kalamazoo, Michigan, USA; H.-H. Wen, University of Nanjing, Nanjing, China; and N. D. Zhigadlo, J. Karpinski, Solid State Physics Laboratory, ETH Zurich, Switzerland.[4pt] This work was supported by the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the DoE, Office of Basic Energy Sciences (LF, YJ, HC, AEK, CC, GS, GWC, HFH, JMZ), by the DoE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 (UW, JAS, WKK) and by the ATLAS accelerator at Argonne (SFZ).

Welp, Ulrich

2012-02-01

393

Vortex Mass, Magnus Force, Viscosity, and the Specific Heat of the Vortex Lattice in Layered Superconductors  

NASA Astrophysics Data System (ADS)

The dynamical motion of a lattice of pancake vortices in a layered superconductor contributes an additional vortex-lattice heat capacity C_v. In contrast to the Debye model of atomic crystalline lattices, the pancake vortices experience a Magnus force and a viscous damping force proportional to their velocity, in addition to the usual Newtonian inertial force proportional to their acceleration. For small distortions of the equilibrium lattice, the resulting mean-square displacement yields C_v, including both classical and quantum regimes. Numerical studies with physically realistic parameters indicate that the Magnus force dominates the viscous damping, so that the resulting vortex-lattice heat capacity Cv resembles that for an undamped vortex system.(K. A. Moler, A. L. Fetter, and A. Kapitulnik, J. Low Temp. Phys. 100), 185RC (1995). A nonzero pancake-vortex mass mv produces an additional Einstein-like branch of the normal-mode spectrum, but its effect is generally negligible unless m_v/me >~ 20.

Fetter, Alexander L.

1996-03-01

394

The leading-edge vortex and quasisteady vortex shedding on an accelerating plate  

NASA Astrophysics Data System (ADS)

A computational inquiry focuses on leading-edge vortex (LEV) growth and shedding during acceleration of a two-dimensional flat plate at a fixed 10°-60° angle of attack and low Reynolds number. The plate accelerates from rest with a velocity given by a power of time ranging from 0 to 5. During the initial LEV growth, subtraction of the added mass lift from the computed lift reveals an LEV-induced lift augmentation evident across all powers and angles of attack. For the range of Reynolds numbers considered, a universal time scale exists for the peak when ?>=30°, with augmentation lasting about four to five chord lengths of translation. This time scale matches well with the half-stroke of a flying insect. An oscillating pattern of leading- and trailing-edge vortex shedding follows the shedding of the initial LEV. The nondimensional frequency of shedding and lift coefficient minima and maxima closely match their values in the absence of acceleration. These observations support a quasisteady theory of vortex shedding, where dynamics are determined primarily by velocity and not acceleration. Finally, the nondimensional vortex formation time is found to be a function of the Reynolds number, but only weakly when the Reynolds number is high.

Chen, Kevin K.; Colonius, Tim; Taira, Kunihiko

2010-03-01

395

Early pinch-off in formation of consecutive vortex rings due to vortex interaction  

NASA Astrophysics Data System (ADS)

The formation of an isolated vortex ring from a starting jet is a limited process described by the non-dimensional formation time. During formation, the vorticity flux of the jet shear layer is entrained into the forming ring until the formation time reaches a limit, upon which the ring pinches off from the trailing jet (Gharib et al. 1998). The limiting formation time can be attributed to the Kevin-Benjamin principle, which dictates that pinch-off occurs when the shear layer is no longer able to deliver the energy required for the existence of a steady vortex ring. In formation of consecutive vortex rings from a pulsed jet, due to interaction between vortex rings, the limiting ring growth process depends not only on the formation time, but also on the pulsing frequency of the jet. This experimental study on a classic piston-cylinder arrangement finds that when pulsing frequency is high and interaction between rings is strong, the forming ring pinches off at a significantly smaller formation time compared with that in isolated ring formation. A theoretical model is developed to explain the reduced limiting formation time in consecutive ring formation.

Peng, Jifeng

2011-11-01

396

A new vortex generator geometry for a counter-flow Ranque–Hilsch vortex tube  

Microsoft Academic Search

In this study, a new geometry is introduced for the cold end side (i.e. where the swirl flow is introduced into the tube), which is called ‘helical swirl flow generator’. Effect of the helical length of the swirl flow generator on the performance of the vortex tube are investigated for varying values of other geometrical parameters as a function of

Orhan Ayd?n; Burak Markal; Mete Avc?

2010-01-01

397

Rotorcraft acoustic radiation prediction based on a refined blade-vortex interaction model  

NASA Astrophysics Data System (ADS)

The analysis of rotorcraft aerodynamics and acoustics is a challenging problem, primarily due to the fact that a rotorcraft continually flies through its own wake. The generation mechanism for a rotorcraft wake, which is dominated by strong, concentrated blade-tip trailing vortices, is similar to that in fixed wing aerodynamics. However, following blades encounter shed vortices from previous blades before they are swept downstream, resulting in sharp, impulsive loading on the blades. The blade/wake encounter, known as Blade-Vortex Interaction, or BVI, is responsible for a significant amount of vibratory loading and the characteristic rotorcraft acoustic signature in certain flight regimes. The present work addressed three different aspects of this interaction at a fundamental level. First, an analytical model for the prediction of trailing vortex structure is discussed. The model as presented is the culmination of a lengthy research effort to isolate the key physical mechanisms which govern vortex sheet rollup. Based on the Betz model, properties of the flow such as mass flux, axial momentum flux, and axial flux of angular momentum are conserved on either a differential or integral basis during the rollup process. The formation of a viscous central core was facilitated by the assumption of a turbulent mixing process with final vortex velocity profiles chosen to be consistent with a rotational flow mixing model and experimental observation. A general derivation of the method is outlined, followed by a comparison of model predictions with experimental vortex measurements, and finally a viscous blade drag model to account for additional effects of aerodynamic drag on vortex structure. The second phase of this program involved the development of a new formulation of lifting surface theory with the ultimate goal of an accurate, reduced order hybrid analytical/numerical model for fast rotorcraft load calculations. Currently, accurate rotorcraft airload analyses are limited by the massive computational power required to capture the small time scale events associated with BVI. This problem has two primary facets: accurate knowledge of the wake geometry, and accurate resolution of the impulsive loading imposed by a tip vortex on a blade. The present work addressed the second facet, providing a mathematical framework for solving the impulsive loading problem analytically, then asymptotically matching this solution to a low-resolution numerical calculation. A method was developed which uses continuous sheets of integrated boundary elements to model the lifting surface and wake. Special elements were developed to capture local behavior in high-gradient regions of the flow, thereby reducing the burden placed on the surrounding numerical method. Unsteady calculations for several classical cases were made in both frequency and time domain to demonstrate the performance of the method. Finally, a new unsteady, compressible boundary element method was applied to the problem of BVI acoustic radiation prediction. This numerical method, combined with the viscous core trailing vortex model, was used to duplicate the geometry and flight configuration of a detailed experimental BVI study carried out at NASA Ames Research Center. Blade surface pressure and near- and far-field acoustic radiation calculations were made. All calculations were shown to compare favorably with experimentally measured values. The linear boundary element method with non-linear corrections proved sufficient over most of the rotor azimuth, and particular in the region of the blade vortex interaction, suggesting that full non-linear CFD schemes are not necessary for rotorcraft noise prediction.

Rule, John Allen

1997-08-01

398

Stable vortex rings due to parametric wave mixing  

Microsoft Academic Search

Summary form only given. Since the pioneering experimental results of optical vortex solitons have been in the centre of interest because of their fundamental importance in optics and other fields of physics, and because of their potential applications for all-optical information processing. Formally conventional vortex solitons exist on an infinite nonzero background, which in practice requires rather large beam sizes

I. Towers; R. A. Sammut; V. Buryak; K. Kolossovski; B. A. Malomed

2000-01-01

399

Vortex Created by Skyrmion Spin Texture under Magnetic Field  

Microsoft Academic Search

We show that a vortex current is created around a skyrmion spin texture under magnetic field due to a radial spin motive force in a two-dimensional metal with localized magnetic moments even in the absence of any superconductivity correlations. The effect is expected both for ferromagnetic and for antiferromagnetic systems. The Skyrmion-induced vortex mechanism provides a picture for large Nernst

Takao Morinari

2010-01-01

400

Visualization of a vortex flow in a rotating tank  

NASA Astrophysics Data System (ADS)

Flow structures of a vortex in a rotating tank were studied employing tracer method. The velocity measurements were made by photographing the motions of small polystyrene particles and analyzing strobo flash light pictures. The vortex flow is confined to a cylindrical region which is composed of a spiral upward flow in the center surrounded by an annular downward flow.

Kawano, Yosuke

401

Spontaneous vortex phases in ferromagnet-superconductor nanocomposites  

Microsoft Academic Search

The interplay between superconductivity and magnetism gives rise to many intriguing and exciting phenomena. In this Letter we report about a novel manifestation of this interplay: a temperature induced phase transition between different spontaneous vortex phases in lead superconducting films with embedded magnetic nanoparticles. Unlike common vortices in superconductors the vortex phase appears without any applied magnetic field. The vortices

Y. T. Xing; H. Micklitz; T. G. Rappoport; M. V. Milosevic; I. G. Solórzano-Naranjo; E. Baggio-Saitovitch

2008-01-01

402

Evidence of spontaneous vortex phase in ferromagnet-superconductor nanocomposites  

Microsoft Academic Search

The interplay between superconductivity and magnetism gives rise to many intriguing phenomena. We report a novel manifestation of this interplay: the appearance of a spontaneous vortex phase in superconducting films with embedded magnetic nanoparticles. These systems can be seen as artificial analogues of ferromagnetic superconductors. Unlike traditional vortices in superconductors, this vortex phase appears without any applied magnetic field. The

Tatiana Rappoport; Yutao Xing; Hans Micklitz; Milorad Milosevic; Ivan Solorzano-Naranjo; Elisa Baggio-Saitovitch

2008-01-01

403

Vortex flow filtration of mammalian and insect cells  

Microsoft Academic Search

The use of vortex flow filtration for harvesting cells or conditioned medium from large scale bioreactors has proven to be an efficient, low shear method of cell concentration and conditioned medium clarification. Several 8–10 L batches of the human histiocytic lymphoma U-937 cell line (ATCC CRL 1593) were concentrated to less than 1 L by vortex flow filtration through a

Steven J. Hawrylik; David J. Wasilko; Joann S. Pillar; John B. Cheng; S. Edward Lee

1994-01-01

404

Active control of vortex breakdown by a spinning wave generator  

Microsoft Academic Search

The results of an experimental study on an active control of the vortex breakdown are presented. Four different modes of spinning disturbances are imposed on the vortex breakdown by a spinning wave generator, which is a device to produce, at a specified frequency, a sinusoidal wave disturbance spinning in the circumferential direction. It is shown that the m = 0

M. Kikuchi; K. Hirano; T. Yuge; M. Kurosaka

1993-01-01

405

Analysis of helicopter blade vortex structure by laser velocimetry  

Microsoft Academic Search

In descent flight, helicopter external noise is mainly generated by the Blade Vortex Interaction (BVI). To under-stand the dynamics of this phenomenon, the vortex must be characterized before its interaction with the blade, which means that its viscous core radius, its strength and its distance to the blade have to be determined by non-intrusive measurement techniques. As part of the

A. Boutier; J. Lefèvre; F. Micheli

1996-01-01

406

Vortex dynamics in the wake of a mechanical fish  

NASA Astrophysics Data System (ADS)

This study focuses on the three-dimensional flow around a mechanical fish model, which reproduces the typical undulatory body and fin motion of a carangiform swimmer. The mechanical model consists of a flexible skeleton embedded in a soft transparent silicone body, which is connected with two cams to a flapping and bending hinge generating a traveling wave motion with increasing amplitude from anterior to posterior, extending to a combined heaving and pitching motion at the fin. The model is submerged in a water tank and towed at the characteristic swimming speed for the neutral swimming mode at U/V = 1. The method of Scanning Particle Image Velocimetry was used to analyze the three-dimensional time-dependent flow field in the axial and saggital planes. The results confirm the earlier observations that the wake develops into a chain of vortex rings which travel sidewards perpendicular to the swimming direction. However, instead of one single vortex shed at each tail beat half-cycle we observed a pair of two vortex rings being shed. Each pair consists of a larger main vortex ring corresponding to the tail beat start stop vortex, while the second vortex ring is due to the body bending motion. The existence of the second vortex reflects the role of the body in undulatory swimming. A simplified model of the fish body comparing it to a plate with a hinged flap demonstrates the link between the sequence of kinematics and vortex shedding.

Brücker, Christoph; Bleckmann, Horst

2007-11-01

407

Vortex dynamics in the wake of a mechanical fish  

NASA Astrophysics Data System (ADS)

This study focuses on the three-dimensional flow around a mechanical fish model, which reproduces the typical undulatory body and fin motion of a carangiform swimmer. The mechanical model consists of a flexible skeleton embedded in a soft transparent silicone body, which is connected with two cams to a flapping and bending hinge generating a traveling wave motion with increasing amplitude from anterior to posterior, extending to a combined heaving and pitching motion at the fin. The model is submerged in a water tank and towed at the characteristic swimming speed for the neutral swimming mode at U/V = 1. The method of Scanning Particle Image Velocimetry was used to analyze the three-dimensional time-dependent flow field in the axial and saggital planes. The results confirm the earlier observations that the wake develops into a chain of vortex rings which travel sidewards perpendicular to the swimming direction. However, instead of one single vortex shed at each tail beat half-cycle we observed a pair of two vortex rings being shed. Each pair consists of a larger main vortex ring corresponding to the tail beat start-stop vortex, while the second vortex ring is due to the body bending motion. The existence of the second vortex reflects the role of the body in undulatory swimming. A simplified model of the fish body comparing it to a plate with a hinged flap demonstrates the link between the sequence of kinematics and vortex shedding.

Brücker, Christoph; Bleckmann, Horst

408

Wing Wake Vortices and Temporal Vortex Pair Instabilities  

Microsoft Academic Search

In this presentation we include selected results which have originated from vortex dynamics studies conducted at Cornell, in collaboration with IRPHE, Marseille. These studies concern, in particular, the spatial development of delta wing trailing vortices, and the temporal development of counter-rotating vortex pairs. There are, as might be expected, similarities in the instabilities of both of these basic flows, as

C. H. K. Williamson; T. Leweke; G. D. Miller

2001-01-01

409

Interactions between a Submesoscale Anticyclonic Vortex and a Front  

Microsoft Academic Search

The evolution of a submesoscale anticyclonic vortex was observed by high-frequency Doppler radio current meters and satellite radiometers. The vortex formed between two large cyclones to the southwest of Oahu, Hawaii. The radius of the core was ;15 km; the azimuthal velocity reached 35 cm s 21 ; and the surface vorticity remained below 2f for 9 days, reaching an

Cédric Chavanne; Pierre Flament; Klaus-Werner Gurgel

2010-01-01

410

THE POWER INITIATING POINT AND TAIL VORTEX IN SCUBA SWIMMING  

Microsoft Academic Search

The purpose of this paper was to explore the position of the power initiating point and the function of tail vortex in scuba swimming. According to the kinematics, human structure and fluid dynamics analysis, it is apparent that the waist serves as the power initiating point. Unlike the traditional concept of swimming, the tail vortex does not always provide resistance

Shuping Li; Youlian Hong; Tze-Chung Luk

411

Alleviation of fuselage form drag using vortex flows: Final report  

Microsoft Academic Search

The concept of using vortex generators to reduce the fuselage form drag of transport aircraft combines the outflow from the plane of symmetry which is induced by the rotational component of the vortex flow with the energization of the boundary layer to reduce the momentum thickness and to delay or eliminate flow separation. This idea was first advanced by the

Wortman

1987-01-01

412

Vortex Visualization in Ultra Low Reynolds Number Insect Flight  

Microsoft Academic Search

Fig. 1. Vortex formation, attachment and shedding on the left forewing and hindwing of a dragonfly during takeoff. Abstract—We present the visual analysis of a biologically inspired CFD simulation of the deformable flapping wings of a dragonfly as it takes off and begins to maneuver, using vortex detection and integration-based flow lines. The additional seed placement and perceptual challenges introduced

Christopher Koehler; Thomas Wischgoll; Haibo Dong; Zachary Gaston

2011-01-01

413

Optical vortex coronagraphs on ground-based telescopes  

Microsoft Academic Search

The optical vortex coronagraph is potentially a remarkably effective device, at least for an ideal unobstructed telescope. Most ground-based telescopes however suffer from central obscuration and also have to operate through the aberrations of the turbulent atmosphere. This paper analyses the performance of the optical vortex in these circumstances and compares to some other designs, showing that it performs similarly

Charles Jenkins

2008-01-01

414

Core dynamics of a strained vortex: instability and transition  

Microsoft Academic Search

We study the instability of a laminar vortex column (in an external orthogonal strain field) to an axisymmetric core size perturbation, and the resulting transition to fine-scale turbulence. The perturbation, which evolves as a standing wave oscillation (i.e. core dynamics, CD), is inviscidly amplified by the external strain. Analysis of a weakly strained Rankine vortex explains the physical mechanism of

D. S. Pradeep; F. Hussain

2001-01-01

415

Karman vortex street parametrization with image processing application  

Microsoft Academic Search

The karman vortex street phenomenon is applied in the vortex flowmeter. Application of various methods of investigations is necessary in the course of getting increased knowledge of the phenomenon. Flow visualization being the leading method of aero- and hydrodynamic phenomena investigations enables qualitative evaluation in micro-scale. Due to the image processing application in analysis of flow visualization pictures, calculation of

Grzegorz Pankanin; Artur Kulinczak; Jerzy Berlinski

2003-01-01

416

Unitary qubit lattice simulations of complex vortex structures  

Microsoft Academic Search

A quantum vortex is a topological singularity with quantized circulation, unlike a classical vortex with its continuous circulation strength. Quantum turbulence, envisaged as strong tangle of quantum vortices, of a Bose–Einstein condensate is examined by developing a unitary qubit lattice algorithm for the solution of the Gross–Pitaevskii equation. Earlier, it was shown that a certain class of initial conditions had

George Vahala; Jeffrey Yepez; Linda Vahala; Min Soe

2012-01-01

417

Entanglement of Two Josephson Vortex Quantum Bits in Resonant Cavity  

Microsoft Academic Search

We investigate the entanglement between two Josephson vortex qubits (JVQ's) in a resonant cavity. A JVQ may be fabricated using two closely spaced microresistor sites in an insulator layer of a long Josephson junction. The phase dynamics of a Josephson vortex (or fluxon) may be described using the perturbed sine-Gordon equation. In a uniform electromagnetic field, it is found that

Isaac O'Bryant; Ramesh P. Dhungana; Ju H. Kim

2008-01-01

418

Entanglement of Two Josephson Vortex Qubits in Resonant Cavity  

Microsoft Academic Search

We discuss the entanglement of two Josephson vortex qubits (JVQs) interacting via the magnetic induction effect. A JVQ may be fabricated by implanting two closely spaced microresistors in the insulating layer of a long Josephson junction (LJJ). These two microresistors generate a double-well potential which traps a Josephson vortex (i.e., fluxon). The macroscopic quantum tunneling (MQT) of the fluxon from

Ramesh Dhungana; Isaac O'Bryant; Ju Kim

2009-01-01

419

Vortex dropshaft retrofitting: case of Naples city (Italy)  

Microsoft Academic Search

This work describes the main hydraulic features of vortex dropshafts along with some examples of their mis-designs and consequent malfunction. Laboratory experiments were conducted to test the hydraulic performance of subcritical vortex intakes using supercritical approach flow design basis. The purposes of these drop structures are to: (i) convey the storm runoff towards the sea through the existing sewer system

Giuseppe Del Giudice; Corrado Gisonni

2011-01-01

420

Separated Flow past Slender delta Wings with Secondary Vortex Simulation.  

National Technical Information Service (NTIS)

The flow about a slender flat-plate delta wing at angleof-attack is represented by replacing the vortex corefeeding sheet system associated with leading edge separation by a force-free concentrated vortex. Secondary flow phenomena near the leading edge ar...

B. Pershing

1964-01-01

421

Nonlinear analysis for the evolution of vortex sheets  

NASA Astrophysics Data System (ADS)

Mathematical results on nonlinear vortex sheet evolution and singularity formation are presented. For sufficiently small analytic perturbations of a nearly flat vortex sheet, smooth solutions of the Birkhoff-Rott equation are shown to exist almost up to the expected time of singularity formation. A construction of exact solutions that develop singularities in finite time starting from analytic initial data is presented.

Caflisch, Russel E.

1988-09-01

422

Vortex past a right vertical cylinder in a rotating fluid  

Microsoft Academic Search

Interaction between a vortex and a right vertical cylinder was investigated in the laboratory for both a self propagating vortex and for one advected by a background uniform flow. In the former case experiments were carried out with a sloping bottom in order to simulate the beta-plane. In the latter case the bottom was flat and a cylinder was towed,

Claudia Cenedese

2000-01-01

423

Current-Driven Vortex Oscillations in Metallic Nanocontacts  

Microsoft Academic Search

We present experimental evidence of subgigahertz spin-transfer oscillations in metallic nanocontacts that are due to the translational motion of a magnetic vortex. The vortex is shown to execute large-amplitude orbital motion outside the contact region. Good agreement with analytical theory and micromagnetics simulations is found.

Q. Mistral; M. van Kampen; G. Hrkac; Joo-Von Kim; T. Devolder; P. Crozat; C. Chappert; L. Lagae; T. Schrefl

2008-01-01

424

Management of a Longitudinal Vortex for Separation Control  

Microsoft Academic Search

Solid (fin) type vortex generators are known to be effective on suppressing flow separations and widely used at various fluid mechanical elements such as intakes or airfoils of airplanes. But the solid type generators themselves are the cause of extra flow drag. In this study we designed a blowing jet type vortex generator to realize smart control of flow separation.

Hiroyuki ABE; Takehiko SEGAWA; Takayuki MATSUNUMA; Hiro YOSHIDA

425

Investigation of asymmetry of vortex flow over slender delta wings  

NASA Astrophysics Data System (ADS)

Vortex flow, a major area of interest in fluid mechanics, is widespread in nature and in many man-made fluid mechanical devices. It can create havoc as cyclones or tornadoes or have significant implications in the performance of turbo-fluid machines or supersonic vehicles and so forth. Asymmetric vortices can cause a loss of lift and increase in rolling moment which can significantly affect wing stability and control. Up until the early nineties, it was generally believed that vortex asymmetry was the result of vortex interactions due to the close proximity of vortices over slender delta wings. However, some recent studies have thrown considerable doubt on the validity of this hypothesis. As a result, wind tunnel investigations were conducted on a series of nine delta wing planforms with sharp and round leading edges to examine the occurrence of vortex asymmetry at different angles of attack and sideslip. The study included surface oil and laser light sheet flow visualization in addition to surface pressure and hot-wire velocity measurements under static conditions. The effects of incidence, sideslip and sweep angles as well as Reynolds number variations were investigated. In this study, it was found that the effect of apex and leading edge shape played an important role in vortex asymmetry generation at high angle of attack. Vortex asymmetry was not observed over slender sharp leading edge delta wings due to the separation point being fixed at the sharp leading edge. Experimental results for these wings showed that the vortices do not impinge on one another because they do not get any closer beyond a certain value of angle of attack. Thus vortex asymmetry was not generated. However, significant vortex asymmetry was observed for round leading-edged delta wings. Asymmetric separation positions over the round leading edge was the result of laminar/turbulent transition which caused vortex asymmetry on these delta wing configurations. Sideslip angle and vortex breakdown were found to be the other major contributors to vortex asymmetry generation over sharp leading edged delta wings. Reynolds number, in the range investigated, was found to have negligible effect on vortex asymmetry on these shapes but had a major asymmetric influence on round leading edged delta wings. In this study it was also found that asymmetric flow separation or asymmetric flow reattachment are the main flow mechanisms triggering the vortex asymmetry. Variation in density and viscosity would not play an important role in the generation of leading edge vortices and as a result, hydrodynamic instability is not the major source of generating vortex asymmetry over sharp leading edged slender delta wings.

Atashbaz, Ghasem

426

Polarization holography for vortex retarders recording.  

PubMed

We present an original static recording method for vortex retarders (VRs) made from liquid crystal polymers (LCPs) using the superimposition of several polarized beams. VRs are birefringent plates characterized by a rotation of their fast axis about their center. The new method is based on polarization holography and photo-orientable LCP. Combining several polarized beams induces the polarization patterns required for the recording process of VRs without mechanical action. A mathematical description of the method, the outcomes of the numerical simulations, and the first experimental results are presented. PMID:24085221

Piron, Pierre; Blain, Pascal; Habraken, Serge; Mawet, Dimitri

2013-10-01

427

Vortex filament model and multifractal conjecture  

NASA Astrophysics Data System (ADS)

We develop a theory of turbulence based on the inviscid Navier-Stokes equation. We get a simple but exact stochastic solution (vortex filament model) which allows us to obtain a power law for velocity structure functions in the inertial range. Combining the model with the multifractal conjecture, we calculate the scaling exponents without using the extended self-similarity approach. The results obtained are shown to be in very good agreement with numerical simulations and experimental data. The role of more general stochastic solutions of the Navier-Stokes equation is discussed.

Zybin, K. P.; Sirota, V. A.

2012-05-01

428

Superconducting vortex lattices for ultracold atoms.  

PubMed

We propose and analyze a nanoengineered vortex array in a thin-film type-II superconductor as a magnetic lattice for ultracold atoms. This proposal addresses several of the key questions in the development of atomic quantum simulators. By trapping atoms close to the surface, tools of nanofabrication and structuring of lattices on the scale of few tens of nanometers become available with a corresponding benefit in energy scales and temperature requirements. This can be combined with the possibility of magnetic single site addressing and manipulation together with a favorable scaling of superconducting surface-induced decoherence. PMID:24138251

Romero-Isart, O; Navau, C; Sanchez, A; Zoller, P; Cirac, J I

2013-10-04

429

Vortex flow in acoustically levitated drops  

NASA Astrophysics Data System (ADS)

The internal flow of acoustically levitated water drops is investigated experimentally. This study reveals a kind of vortex flow which rotates in the meridional plane of the levitated drop. The magnitude of fluid velocity is nearly vanishing at the drop center, whereas it increases toward the free surface of a levitated drop until the maximum value of about 80 mm/s. A transition of streamline shapes from concentric circles to ellipses takes place at the distance of about 1.2 mm from the drop center. The fluid velocity distribution is plotted as a function of polar angle for seven characteristic streamlines.

Yan, Z. L.; Xie, W. J.; Wei, B.

2011-08-01

430

Vortex filament model and multifractal conjecture.  

PubMed

We develop a theory of turbulence based on the inviscid Navier-Stokes equation. We get a simple but exact stochastic solution (vortex filament model) which allows us to obtain a power law for velocity structure functions in the inertial range. Combining the model with the multifractal conjecture, we calculate the scaling exponents without using the extended self-similarity approach. The results obtained are shown to be in very good agreement with numerical simulations and experimental data. The role of more general stochastic solutions of the Navier-Stokes equation is discussed. PMID:23004872

Zybin, K P; Sirota, V A

2012-05-30

431

Superconducting Vortex Lattices for Ultracold Atoms  

NASA Astrophysics Data System (ADS)

We propose and analyze a nanoengineered vortex array in a thin-film type-II superconductor as a magnetic lattice for ultracold atoms. This proposal addresses several of the key questions in the development of atomic quantum simulators. By trapping atoms close to the surface, tools of nanofabrication and structuring of lattices on the scale of few tens of nanometers become available with a corresponding benefit in energy scales and temperature requirements. This can be combined with the possibility of magnetic single site addressing and manipulation together with a favorable scaling of superconducting surface-induced decoherence.

Romero-Isart, O.; Navau, C.; Sanchez, A.; Zoller, P.; Cirac, J. I.

2013-10-01

432

Nonlinear Stability for Steady Vortex Pairs  

NASA Astrophysics Data System (ADS)

In this article, we prove nonlinear orbital stability for steadily translating vortex pairs, a family of nonlinear waves that are exact solutions of the incompressible, two-dimensional Euler equations. We use an adaptation of Kelvin's variational principle, maximizing kinetic energy penalised by a multiple of momentum among mirror-symmetric isovortical rearrangements. This formulation has the advantage that the functional to be maximized and the constraint set are both invariant under the flow of the time-dependent Euler equations, and this observation is used strongly in the analysis. Previous work on existence yields a wide class of examples to which our result applies.

Burton, Geoffrey R.; Nussenzveig Lopes, Helena J.; Lopes Filho, Milton C.

2013-10-01

433

Numerical analysis of a vortex controlled diffuser  

NASA Astrophysics Data System (ADS)

A numerical study of a prototypical vortex controlled diffuser is performed. The basic diffuser geometry consists of a step expansion in a pipe of area ratio 2.25:1. The incompressible Reynolds averaged Navier-Stokes equations, employing the K-epsilon turbulence model, are solved. Results are presented for bleed rates ranging from 1 to 7 percent. Diffuser efficiencies in excess of 80 percent are obtained. Reattachment lengths are reduced by a factor of up to 3. These results are in qualitative agreement with previous experimental work. However, differences in some basic details of experimentally observed and the present numerically generated flowfields exist. The effect of swirl is also investigated.

Spall, Robert E.

1993-11-01

434

Dynamics of Saturn's South Polar Vortex  

NASA Astrophysics Data System (ADS)

We present observations of Saturn's south polar vortex (SPV) showing that it shares some properties with terrestrial hurricanes: cyclonic circulation, warm central region (the eye) surrounded by a ring of high clouds (the eye wall), and convective clouds outside the eye. The polar location and the absence of an ocean are major differences. It also shares properties with the polar vortices on Venus, such as polar location, cyclonic circulation, warm center, and long lifetime, but the Venus vortices have cold collars and are not associated with convective clouds. The SPV's combination of properties is unique among vortices in the solar system.

Dyudina, Ulyana A.; Ingersoll, Andrew P.; Ewald, Shawn P.; Vasavada, Ashwin R.; West, Robert A.; Del Genio, Anthony D.; Barbara, John M.; Porco, Carolyn C.; Achterberg, Richard K.; Flasar, F. Michael; Simon-Miller, Amy A.; Fletcher, Leigh N.

2008-03-01

435

Dynamical Phases of Driven Vortex Systems  

SciTech Connect

We study numerically the motion of vortices in dirty type II superconductors. In two dimensions at strong driving currents, vortices form highly correlated {open_quote}{open_quote}static channels.{close_quote}{close_quote} The static structure factor exhibits convincing scaling behavior, demonstrating quasi-long-range translational order in the transverse direction. However, order in the longitudinal direction is only short range. We clearly establish the existence of a finite transverse critical current, suggesting strong barriers against transverse driving forces. We discuss these results in terms of recently proposed theories of the moving vortex systems. {copyright} {ital 1996 The American Physical Society.}

Moon, K.; Scalettar, R.T.; Zimanyi, G.T. [Physics Department, University of California, Davis, California 95616 (United States)

1996-09-01

436

Experimental investigation of wake vortex in a water towing tank  

NASA Astrophysics Data System (ADS)

Wake vortex behind an aircraft would introduce great hazard to the following aircraft and threaten to the flight safety. Generic model using two rectangular airfoils was employed for generating wake vortex system to investigate the method of wake vortex alliviation. The investigation was carried out in a water towing tank equipt with Particle Image Velocimetry system. Characteristics of double-vortex flow were analyzed for selected cases, proving that the intensity of the vortex is reduced with respect to the interaction between the wake vortices. The study exhibited that the R-L instability was most effectively triggered with parameter combinations of ?1=10°, ?2=8°and b=50mm respectively. As a result, the circulation of the wake vortices was alleviated by nearly 40% accordingly.

Liu, Yue; Wang, Junwei; Liu, Zhirong; Bao, Feng

2012-10-01

437

A vortex pair near a density gradient interface  

NASA Astrophysics Data System (ADS)

The dynamics of a vortex pair in a stratified atmosphere near a density gradient interface is considered here using direct numerical simulations. A density-gradient interface has continuous density but discontinuous gradient of density, and is a common model of the tropopause. The vortex pair is released below the interface and allowed to propagate vertically toward the interface. The anelastic approximation of the Navier-Stokes equations are treated using a spectral method, and the initial vortex has a Gaussian distribution of vorticity. The results show that strong vortices propagate through the interface without much change in dynamics. Weaker vortices will dissipate energy when they reach the interface and although a remnant of the vortex pair transits the interface, it does not achieve the same altitude that it would have without the interface. Overall, the interface is not a barrier to vortex pairs, but would be expected to change the distribution of energy in more complicated flows.

Shaw, Surupa; Jenkins, Nick; McHugh, John

2011-11-01

438

The stability of a family of vortex rings  

NASA Astrophysics Data System (ADS)

Jetting swimmers, such as squid or jellyfish, propel themselves by forming axisymmetric vortex rings. In order to evaluate the performance of these swimmers, we must asses the optimality of the vortex wakes they produce, which requires an understanding of their stability. We consider the Norbury family of vorticesootnotetextJ. Norbury, J. Fluid Mech., 57, 417-431, 1973. as a model for the vortex rings produced by jetting swimmers. PozrikidisootnotetextC. Pozrikidis, J. Fluid Mech., 168, 337-367, 1986. has studied the stability of Hill's spherical vortex under axisymmetric prolate and oblate shape perturbations. However, the stability of other members of the Norbury family to axisymmetric perturbations of the type that might occur during the vortex formation process in jetting swimmers is unknown. In order to asses the stability of different members of the family, we introduce physically pertinent shape perturbations and simulate their development in a manner akin to Pozrikidis' analysis.

O'Farrell, Clara; Dabiri, John O.

2010-11-01

439

The design of optical fiber vortex flowmeter's probe  

NASA Astrophysics Data System (ADS)

The vortex flowmeter works in a poor environment, therefore the stability and accuracy of the online testing system have become the core question for getting high accuracy. The optical probe is the main part of the system which produces and obtains the vortex signal. This paper designs the vortex shedder according to the hydromechanics principle, and it is proposed to be ringlike structures, also gives the test results which prove the effectiveness of the shedder on vortex decomposition. A liquid flow online testing system is designed according to the vortex signal characteristics, and the optical fiber is chosen as the sense organ. Then it designed the probe's parameters and the necessary important circuits of the system to further increase its accuracy. It also assembles the sensor system which is designed to insure the rationality, reliability, stability of the structure. Finally it proposed the methods on the coefficient revision and the liquid condition parameter compensation to get higher accuracy.

Lin, Xiaolin; Wang, Yutian; Ni, Yang; Li, Jianxia

2009-07-01

440

Quantum vortex dynamics in two-dimensional neutral superfluids  

SciTech Connect

We derive an effective action for the vortex-position degree of freedom in a superfluid by integrating out condensate phase- and density-fluctuation environmental modes. When the quantum dynamics of environmental fluctuations is neglected, we confirm the occurrence of the vortex Magnus force and obtain an expression for the vortex mass. We find that this adiabatic approximation is valid only when the superfluid droplet radius R, or the typical distance between vortices, is very much larger than the coherence length xi. We go beyond the adiabatic approximation numerically, accounting for the quantum dynamics of environmental modes and capturing their dissipative coupling to condensate dynamics. For the case of an optical-lattice superfluid, we demonstrate that vortex motion damping can be adjusted by tuning the ratio between the tunneling energy J and the on-site interaction energy U. We comment on the possibility of realizing vortex-Landau-level physics.

Wang, C.-C. Joseph [University of Texas at Austin, Department of Physics, 1 University Station C1600, Austin, Texas 78712-0264 (United States); Duine, R. A.; MacDonald, A. H. [Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, NL-3584 CE Utrecht (Netherlands)

2010-01-15

441

Vortex dynamics in incompressible Richtmyer-Meshkov Instability  

NASA Astrophysics Data System (ADS)

We study temporal evolution of an interface in the Richtmyer- Meshkov instability numerically. The interface is treated as a vortex sheet and the Birkhoff-Rott equation is used in order to describe motion of a vortex sheet. We show that redistribution of grid points to equal arclength and the application of the Fourier series expansion for numerical differentiations and integrations make it possible to perform long-time caluculations. Successive profiles of a vortex sheet and the temporal evolution of the sheet strength are presented, and especially the evolution of the sheet strength of a vortex core, defined as a point at which the absolute values of the curvature and strength of a sheet become maximum, is discussed. It is found that the sheet strength of a vortex core takes a maximal value at a finite time and turns to gradually decreasing when the Atwood number in the system is non-zero.

Matsuoka, Chihiro; Nishihara, Katsunobu

2005-10-01

442

Stability of an optical vortex in a circular nematic cell  

SciTech Connect

The stability of an optical vortex in a cell with a circular cross section containing a nematic liquid crystal is studied. A modulation theory based on an averaged Lagrangian formulation is developed to study this stability. It is found that the vortex is stable unless the radius of the cell is very small, nearly the width of the vortex itself. Based on the analysis of a stationary vortex, the stability of a low-amplitude vortex in a large cell under the influence of its orbital angular momentum and the repelling effect of the cell boundary are studied. The predictions of this modulation theory are found to be in excellent agreement with numerical simulations.

Minzoni, Antonmaria A. [Fenomenos Nonlineales y Mecanica (FENOMEC), Departamento de Matematicas y Mecanica, Instituto de Investigacion en Matematicas Aplicadas y Sistemas, Universidad Nacional Autonoma de Mexico, 01000 Mexico D.F. (Mexico); Smyth, Noel F. [School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom); Xu Zhiyong [Nonlinear Physics Center, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2010-03-15

443

A study of short wave instability on vortex filaments  

SciTech Connect

The numerical stability and accuracy of the vortex method are studied. The effect of the ordinary differential equations (ODE) solver and of the time step on the numerical stability is analyzed. Various ODE solvers are compared and a best performer is chosen. A new constraint on the time step based on numerical stability is proposed and verified in numerical simulations. It is shown through numerical examples that empirical rules for selecting the spatial discretization obtained in simple test problems may not be extended to more general problems. The thin tube vortex filament method is applied to the problem of Widnall`s instability on vortex rings. Numerical results different from previous calculations are presented and the source of the discrepancies is explained. The long time behavior of the unstable mode on thin vortex rings is simulated and analyzed. The short wave instability on vortex filaments is investigated both theoretically and numerically. It is shown that the short wave instability always occurs on co-rotating vortex filaments of fixed core structure. Furthermore when they are close to each other, vortex filaments produce short wave unstable modes which lead to wild stretching and folding. However, when the inter-filament distance is large in comparison with the core size of the filaments, unstable modes are bounded by a small fraction of the core size and the vortex filaments do not create hairpins nor wild stretching. These findings may explain the smooth behavior of the superfluid vortices. The formation of hairpin structures on numerical vortex filaments is investigated. It is shown that the formation of hairpin structures is independent of the ODE solver, of the time step and of other numerical parameters. The hairpin structures are primarily caused by short wave instability on co-rotating vortex filaments.

Wang, Hong Yun

1996-12-01

444

The critical cross-section of a vortex  

NASA Astrophysics Data System (ADS)

This paper discusses the problem of critical-flow cross-sections in vortex flows. It is shown that there are two different types of vortex flows, A-type and B-type vortices (say). An A-type vortex approaches its critical flow state as its cross-sectional area increases and departs from the critical state as the cross-sectional area is decreased. This property is associated with the particular dependence of total pressure and circulation on the stream function, and it holds for both subcritical and supercritical A-type vortices. On the other hand, both subcritical and supercritical B-type vortices approach their critical flow states as their cross-sectional areas are decreased and depart from their critical states for increasing cross-sectional area. As was shown by Benjamin, setting the first variation of the flow force with respect to the stream function equal to zero leads to Euler's equation of motion. The second variation also vanishes if the corresponding flow state is critical. In this case the sign of the third variation decides whether the flow is an A-type or a B-type vortex. Within the framework of inviscid-fluid flow theory the type of a vortex is preserved unless vortex breakdown occurs. Making use of the knowledge that vortex flows are controlled by two different types of critical-flow cross-sections a variety of vortex flow phenomena are investigated, including the two types of inlet vortices that are observed upstream of jet engines, the behavior of vortex valves, the flow characteristics of liquid-fuel atomizers and the bath tub vortex.

Keller, Jakob J.

1995-01-01

445

Actions Needed to Ensure Scientific and Technical Information is Adequately Reviewed at Goddard Space Flight Center, Johnson Space Center, Langley Research Center, and Marshall Space Flight Center.  

National Technical Information Service (NTIS)

This audit was initiated in response to a hotline complaint regarding the review, approval, and release of scientific and technical information (STI) at Johnson Space Center. The complainant alleged that Johnson personnel conducting export control reviews...

2008-01-01

446

Vortex Rossby waves on smooth circular vortices Part II. Idealized numerical experiments for tropical cyclone and polar vortex interiors  

Microsoft Academic Search

Idealized linear and nonlinear numerical experiments are carried out to test the predictions of the theory developed in Brunet and Montgomery (Vortex Rossby Waves on Smooth Circular Vortices Part I: Theory (pages 153-177, this issue)). For a monopolar tropical cyclone-like vortex whose strength lies between a tropical depression and tropical storm, linear theory remains uniformly valid in time in the

Michael T. Montgomerya; Gilbert Brunet

447

Numerical studies of plume-vortex interactions  

NASA Astrophysics Data System (ADS)

A new mixing model was developed to study the initial engine exhaust plume evolution with reduced reaction mechanism for the lower stratosphere. The results show that the effects of the local lack of mixing have an inhibiting effect on ozone depletion in the near-field plume. Inclusion of heterogeneous kinetics involving formation of condensed nitric and sulfuric acid on soot particles showed that 15% of the available NOx, is converted into its inactive form. A comprehensive and efficient aerosol model coupled with chemical kinetics and the jet flow model was developed. The predictions of aerosol number density, surface area density agree with previous simulations qualitatively. The comparison of predictions between with and without the micro-mixing effect also suggests that lack of micro-mixing tends to underpredict the aerosol number density. To study the plume-vortex interaction, a parallel LES code is first validated against experimental free jet data and then applied to the study of the near-field plume-vortex interaction dynamics with gas-phase and heterogeneous chemistry. The simulation results show reasonable agreement with in-situ observations. Results indicate that a significant difference between spatial and temporal simulation exists, which affects the accuracy of the prediction of sulfuric acid aerosols in the wake. Analysis of the results also shows that spatial simulation is more suitable for the near field interaction process.

Wu, Junxiao

1999-11-01

448

Vortex ring refraction at large Froude numbers  

NASA Astrophysics Data System (ADS)

We have experimentally studied the impact of a planar axisymmetric vortex ring, incident at an oblique angle, upon a sharp gravity-induced interface separating two fluids of differing densities. After impact, the vortex ring was found to exhibit a variety of subsequent trajectories, which we have organized according to both the incidence angle, and the ratio of the Atwood and Froude numbers, A/F. For relatively small angles of incidence, the vortices tended to penetrate the interface. In such cases, the more slowly moving vortices, having values of A/F .004, tended to subsequently curve back up toward the interface. Quickly moving vortices, on the other hand, tended to refract downward, similar to a light ray entering a medium having a higher refractive index. A simplistic application of Snell's law of refraction cannot, however, account for the observed trajectories. For grazing angles of incidence, fast moving vortices tended to penetrate the interface, whereas slower vortices tended to reflect from the interface. In some cases, the reflected vortices executed damped oscillations before finally disintegrating.

Kuehn, Kerry; Moeller, Matthew; Schulz, Michael; Sanfelippo, Daniel

2010-03-01

449

Non-Riemannian geometry of vortex acoustics  

SciTech Connect

The concept of acoustic torsion is introduced by making use of the scalar wave equation in Riemann-Cartan spacetime. Acoustic torsion extends the acoustic metric previously given by Unruh (PRL-1981). The wave equation describes irrotational perturbations in rotational nonrelativistic fluids. This physical motivation allows us to show that the acoustic line element can be conformally mapped to the line element of a stationary torsion loop in non-Riemannian gravity. Two examples of such sonic analogues are given. The first is the stationary torsion loop in teleparallel gravity. In the far from the vortex approximation, the Cartan torsion vector is shown to be proportional to the quantum vortex number of the superfluid. The torsion vector is also shown to be proportional to the superfluid vorticity in the presence of vortices. The formation of superfluid vortices is shown not to be favored by torsion loops in Riemann-Cartan spacetime, as long as this model is concerned. It is suggested that the teleparallel model may help to find a model for superfluid neutron stars vortices based on non-Riemannian gravity.

Garcia de Andrade, L.C. [Departamento de Fisica Teorica, Instituto de Fisica, Universidade Estadual do Rio de Janeiro, Rua Sao Francisco Xavier 524, Maracana, 20550, Rio de Janeiro, RJ (Brazil)

2004-09-15

450

Unsteady turbulent round jets and vortex motion  

NASA Astrophysics Data System (ADS)

A new model to predict the velocity distribution in round jets with time-varying injection profiles has been formulated as an extension of steady jet theory. The approach introduces an effective injection velocity within the jet based on a representative response time. It is assumed that the instantaneous injection velocity affects the velocity within the jet with an exponential response function and that the response time is related to the fluid particle's residence time within the jet, consistent with the theory of translation of jet vortex rings from Helmholtz's vortex motion analysis [P. G. Tait, London Edinburgh Dublin Philos. Mag. J. Sci. 33, 485 (1867)]. The Helmholtz theory is also shown to reduce to the well-known velocity decay rate in the case of steady turbulent gas jets. A Duhamel superposition integral is used to determine the effective injection velocity for time-varying injection rates. The model is tested with different injection profiles and different ambient densities. The results are also compared with numerical results from a computational fluid dynamics code. The comparisons agree very well and the new model is shown to offer an efficient method to predict jet tip penetrations for unsteady jets.

Abani, Neerav; Reitz, Rolf D.

2007-12-01

451

Vortex breakdown in slowly diverging pipes  

NASA Astrophysics Data System (ADS)

Steady vortex breakdown of incompressible, high-Reynolds-number, swirling flows through slowly diverging axisymmetric pipes is studied. The rate of divergence is chosen so that viscous diffusion across the pipe is significant. An asymptotic high-Reynolds-number approximation leads to interactive boundary-layer equations which are solved numerically. For a given geometry it is known that, as the swirl is increased from zero, a bifurcation fold is usually encountered at a critical value of the swirl (often before the onset of flow reversal). This fold has been cited as the reason for vortex breakdown, since the flow must snap to another solution branch for larger swirls. However, as shown by Buntine & Saffman (1995, Proc. R. Soc. Lond. A 449, 139), the flow can reverse before the fold is reached. We study such flows when there is a relatively rapid expansion of the pipe. The flow then consists of almost inviscid regions separated by thin viscous layers. Inter alia, we examine the limiting flow in the recirculating bubble and compare our numerical results with earlier theories.

Herrada, Miguel A.; Cowley, Stephen J.

2001-11-01

452

Kelvin wave turbulence generated by vortex reconnections  

NASA Astrophysics Data System (ADS)

Reconnections of quantum vortex filaments create sharp bends, which degenerate into propagating Kelvin waves. These waves cascade their energy down-scale and their wave action up-scale via weakly nonlinear interactions, and this is the main mechanism of turbulence at scales less than the inter-vortex distance. In the case of an idealized forcing concentrated around a single scale k 0, the turbulence spectrum exponent has a pure direct cascade form -17/5 at scales k > k 0 [B. V. Svistunov, Phys. Rev. B 52, 3647 (1995)] and a pure inverse cascade form -3 at k < k 0 (V. Lebedev, private communication). However, forcing produced by the reconnections contains a broad range of Fourier modes. What scaling should one expect in this case? An answer to this question has been obtained using the differential model for the Kelvin wave turbulence introduced in [S. Nazarenko, JETP Lett. 83, 198 (2005)]. The main result is that the direct cascade scaling dominates; i.e., the reconnection forcing is more or less equivalent to a low-frequency forcing.

Nazarenko, S.

2007-02-01

453

PERFORMANCE IMPROVEMENT OF AIRFOILS FOR WIND TURBINES BY THE MODIFIED VORTEX GENERATOR  

Microsoft Academic Search

In this paper, the new modified vortex generator (VG) was developed for wind turbine airfoils. The modified vortex generator has a section of airfoil to decrease the drag of the vortex generator itself while keeping the strength of streamwise vortices. The wind tunnel experiments were conducted to examine the effectiveness of the modified vortex generator. The effect of Reynolds number,

Tetsuya KOGAKI; Hikaru MATSUMIYA; Kaori KIEDA; Naofumi YOSHIMIZU; Yuusuke YAMAMOTO

454

Magnetic vortex dynamics in elliptical dots: Field dependence and interaction effects  

Microsoft Academic Search

This study aims to investigate experimentally the dynamics of magnetic vortices and vortex pairs confined in lithographically defined Permalloy ellipses using microwave reflection technique. The single vortex magnetization state exhibits a single, low frequency peak in the impedance derivative spectrum for a given external field. Experimental results show that vortex polarization dominates the vortex dynamics while it plays a negligible

K. S. Buchanan; P. E. Roy; M. Grimsditch; E. Y. Fradin; K. Y. Guslienko; S. D. Bader; V. Novosad

2006-01-01

455

Thermal vortex dynamics in thin circular ferromagnetic nanodisks  

NASA Astrophysics Data System (ADS)

The dynamics of gyrotropic vortex motion in a thin circular nanodisk of soft ferromagnetic material is considered. The demagnetization field is calculated using two-dimensional Green's functions for the thin-film problem and fast Fourier transforms. At zero temperature, the dynamics of the Landau-Lifshitz-Gilbert equation is simulated using fourth-order Runge-Kutta integration. Pure vortex initial conditions at a desired position are obtained with a Lagrange multipliers constraint. These methods give accurate estimates of the vortex restoring force constant kF and gyrotropic frequency, showing that the vortex core motion is described by the Thiele equation to very high precision. At finite temperature, the second-order Heun algorithm is applied to the Langevin dynamical equation with thermal noise and damping. A spontaneous gyrotropic motion takes place without the application of an external magnetic field, driven only by thermal fluctuations. The statistics of the vortex radial position and rotational velocity are described with Boltzmann distributions determined by kF and by a vortex gyrotropic mass mG=G2/kF, respectively, where G is the vortex gyrovector.

Wysin, G. M.; Figueiredo, W.

2012-09-01

456

Reynolds-number Effect on Vortex Ring Evolution  

NASA Astrophysics Data System (ADS)

An analytical model describing a vortex ring for low Reynolds numbers (Re) proposed previously by Kaplanski and Rudi [Phys. Fluids,17, 087101 (2005)], is extended to a vortex rings for higher Reynolds numbers. The experimental results show that the vortex ring core takes the oblate ellipsoidal shape with increasing Re. In order to model this feature, we suggest an expression for the vorticity distribution, which corrects the linearized solution of the Navier-Stokes equation, with two disposable nondimensional parameters ? and ? governing the shape of the vortex core, and derive the new expressions for the streamfuction, circulation, energy and translation velocity on the basis of it. The appropriate values of ? and ? are calculated by equating the nondimensional energy Ed and circulation \\Gcyd of the theoretical vortex to the corresponding values obtained from the experimental or numerical vortex ring. To validate the model, the data adapted from the numerical study of a vortex ring at Re = 1400 performed by Danaila and Helie [Phys. Fluids, 20, 073602 (2008)], is applied. It is shown that the predicted temporal evolution of the translation velocity at high Reynolds numbers matches very well with the experiments and numerical simulations.

Kaplanski, F.; Fukumoto, Y.; Rudi, Y.

2011-09-01

457

Vortex dynamics in cubic-quintic Bose-Einstein condensates.  

PubMed

We study vortex dynamics in a trapped Bose-Einstein condensate with tunable two- and three-body interactions. The dynamics is governed by two-dimensional cubic-quintic Gross-Pitaevskii equation. A time-dependent variational method has been used to obtain critical rotational frequency and surface mode frequency analytically and are compared with numerical simulation results. An imaginary time propagation method and Crank-Nicolson scheme for discretization have been used for numerical simulation. The numerically calculated average value of the angular momentum per particle shows very clearly its dynamical relation with the time development of the vortex formation. The rotational frequency dependence of the variation of average value of the angular momentum per particle with time shows that vortices form much faster in time for higher rotational frequency. Similarly, the vortex forms much faster in time with an increase of the strength of the repulsive three-body interaction. The simulation of the vortex lattice formation in the condensate shows that the presence of the three-body interactions does not alter the vortex lattice pattern but it helps in the shape deformations of the condensate thereby leading to vortex lattice formation. Likewise, the three-body interactions enable the vortex lattice formation in Bose-Einstein condensates even with attractive two-body interactions and in purely quintic BEC. PMID:23944535

Mithun, T; Porsezian, K; Dey, Bishwajyoti

2013-07-08

458

Interaction of heat release and vortex breakdown during flame flashback driven by combustion induced vortex breakdown  

Microsoft Academic Search

The interaction of heat release by chemical reaction and the flow dominates flame transition in swirling flows caused by combustion\\u000a induced vortex breakdown (CIVB). The simultaneous application of 1 kHz high-speed particle imaging velocimetry (PIV) for the\\u000a analysis of the flow field and OH planar laser-induced fluorescence for the detection of the flame front is particularly useful\\u000a for the improvement

Marco Konle; Thomas Sattelmayer

2009-01-01

459

Vertically homogeneous stationary tornado-type vortex  

NASA Astrophysics Data System (ADS)

Tornado is regarded as one of the most dangerous atmosphere phenomena. The tornado phenomenon has been intensively studied so far, however, there is still no established and accepted theory of how tornadoes form, an uncertainty still exists concerning extreme winds and pressure drops in tornadoes. It is commonly accepted that it is possible to describe tornado from the set of nonlinear hydrodynamical equations, however, it is still unclear which non-linear processes are responsible for its formation. Nonlinear terms in the system are associated with either centrifugal force, or entropy transport, or transport of humidity. It appears that the amount and spatial distribution of precipitation with the convection are important indicators of the weather phenomena associated with a particular storm. The low-precipitation supercells that produce relatively little precipitation and yet show clear visual signs of rotation. Low-precipitation supercells occur most often near the surface dryline and, owing to the sparse precipitation and relatively dry environments with little cloudiness. Low-precipitation storms are frequently non-tornadic and many are non-severe despite exhibiting persistent rotation. On the other hand, the so-called high-precipitation storms are characterized by substantial precipitation within their mesocyclonic circulations. When high-precipitation storms have a recognizable hook radar echo, reflectivity in the hook is comparable to those in the precipitation core. High-precipitation supercells are probably the most common form of supercell and produce severe weather of all types including tornadoes. Therefore, in this work we consider a hydrodynamic system with only one nonlinear term associated with atmosphere humidity, which yields energy to the system. The tornado vortex is usually to a good approximation cylindrical so we use cylindrical geometry and homogeneity in vertical direction. In this case the problem reduces to a system of ordinary differential equations. Rotation in the vortex is associated with compressibility so we also take into account the compressibility of the gas. Under certain approximations the problem reduces to a single high-order nonlinear equation. Numerical solution of the obtained high-order equation describes all three velocity components and all thermodynamic parameters in the system. The system exhibits high rotation and strong vertical air flow in the middle part of the vortex.

Rutkevich, P. B.; Rutkevych, P. P.

2010-05-01

460

Hidden vortex lattices in a thermally paired superfluid  

SciTech Connect

We study the evolution of rotational response of a statistical mechanical model of two-component superfluid with a nondissipative drag interaction as the system undergoes a transition into a paired superfluid phase at finite temperature. The transition manifests itself in a change of (i) vortex-lattice symmetry and (ii) nature of the vortex state. Instead of a vortex lattice, the system forms a highly disordered tangle which constantly undergoes merger and reconnecting processes involving different types of vortices with a 'hidden' breakdown of translation symmetry.

Dahl, E. K.; Sudboe, A. [Department of Physics, Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Babaev, E. [Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Department of Theoretical Physics, The Royal Institute of Technology, 10691 Stockholm (Sweden)

2008-10-01

461

Experimental observation of a tripolar vortex in a plasma  

NASA Astrophysics Data System (ADS)

A tripolar vortex, three aligned vortices with alternate signs of polarity of rotation, has been observed in a plasma for the first time. The tripolar vortex always appears with a deep density depression in the neutral particles, and the rotation direction of each vortex is opposite to that of the E×B rotation due to the ambipolar electric field. It is shown that a net momentum transfer during the charge-exchange interaction produces an effective force acting on the ions. The present experiment shows that this effective force may dominate the ambipolar-electric field and drive the anti-E×B vortical motion of ions.

Okamoto, A.; Hara, K.; Nagaoka, K.; Yoshimura, S.; Vranješ, J.; Kono, M.; Tanaka, M. Y.

2003-06-01

462

The novel electrodynamics of combined pancake and Josephson vortex lattice  

NASA Astrophysics Data System (ADS)

Description of a Josephson vortex (JV) crossed by pancake vortex stacks (PVSs) aligned along the c-axis is proposed. The model, which is based on the extended London theory, takes into account the interaction of PVSs with currents of JV which deform the PVS lattice. The deformation of the PVS lattice induces additional currents along the c-axis which renormalize the JV field distribution as well as the energy of JV. This account for the recent observation of the non-monotonical angular dependence of the vortex lattice melting transition in Bi2Sr2CaCu2O8+? [J. Mirkovi? et al., Phys. Rev. Lett. 86 (2001) 886].

Savel'ev, S.; Mirkovi?, J.; Kadowaki, K.

2001-09-01

463

Dissipative vortex solitons in two-dimensional lattices  

SciTech Connect

We report the existence of stable symmetric vortex-type solutions for two-dimensional nonlinear discrete dissipative systems governed by a cubic-quintic complex Ginzburg-Landau equation. We construct a whole family of vortex solitons with a topological charge S=1. Surprisingly, the dynamical evolution of unstable solutions of this family does not significantly alter their profile, but instead their phase distribution completely changes; they transform into two-charge swirl-vortex solitons. We dynamically excite this structure showing its experimental feasibility.

Mejia-Cortes, C.; Soto-Crespo, J. M. [Instituto de Optica, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain); Molina, Mario I.; Vicencio, Rodrigo A. [Departamento de Fisica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Center for Optics and Photonics, Universidad de Concepcion, Casilla 4016, Concepcion (Chile)

2010-12-15

464

Effective Dynamics of a Magnetic Vortex in a Local Potential  

NASA Astrophysics Data System (ADS)

We study a simplified mean field model of superconductor dynamics in the presence of impurities or for variable superconductor depth. This model is given by the gradient-flow version of the Ginzburg-Landau equations (Gorkov-Eliashberg equations) with an addition of a potential term. We find a dynamical law of motion of the vortex center, involving the potential, such that for datum close to a (static) magnetic vortex the solution is close, for all times, to a magnetic vortex whose center obeys this law.

Strauss, Y.; Sigal, I. M.

2006-04-01

465

Nonlinear vortex dynamics and transient domains in ferromagnetic disks  

NASA Astrophysics Data System (ADS)

We report a time-resolved imaging and micromagnetic simulation study of the relaxation dynamics of a magnetic vortex in the nonlinear regime. We use time-resolved photoemission electron microscopy and micromagnetic calculations to examine the emergence of nonlinear vortex dynamics in patterned Ni80Fe20 disks in the limit of long field pulses. We show for core shifts beyond ˜20%-25% of the disk radius, the initial motion is characterized by distortions of the vortex, a transient cross-tie wall state, and instabilities in the core polarization that influence the core trajectories.

Cheng, X. M.; Buchanan, K. S.; Divan, R.; Guslienko, K. Y.; Keavney, D. J.

2009-05-01

466

Harnessing Optical Vortex Lattices in Nematic Liquid Crystals  

NASA Astrophysics Data System (ADS)

By creating self-induced vortexlike defects in the nematic liquid crystal layer of a light valve, we demonstrate the realization of programable lattices of optical vortices with arbitrary distribution in space. On each lattice site, every matter vortex acts as a photonic spin-to-orbital momentum coupler and an array of circularly polarized input beams is converted into an output array of vortex beams with topological charges consistent with the matter lattice. The vortex arrangements are explained on the basis of light-induced matter defects of both signs and consistent topological rules.

Barboza, R.; Bortolozzo, U.; Assanto, G.; Vidal-Henriquez, E.; Clerc, M. G.; Residori, S.

2013-08-01

467

Dynamic analysis of marine risers with vortex excitation  

SciTech Connect

The basic equations for nonplanar transverse vibrations of marine risers are derived from the theory of elastic rods. A numerical method is developed for solution of the equations by time integration. Spatial discretization is accomplished by a hybrid finite element method. Vortex excitation is modeled by the coupled wake oscillator proposed by Iwan and Blevins. The vortex oscillator equations are integrated numerically in time along with the riser equations. By way of example, several typical riser problems are analyzed including forced vibration and vortex-induced vibration.

Nordgren, R.P.

1982-03-01

468

Spiral vortex solution of Birkhoff-Rott equation  

NASA Astrophysics Data System (ADS)

Evolution of a spiral vortex-sheet in an unbounded inviscid fluid is considered and a similarity solution to the Birkhoff-Rott equation (an integro-differential equation governing vortex-sheet dynamics) is presented. This solution exhibits evolution of a double-branched vortex-sheet of an exponential spiral. It is shown that this is equivalent to the previously known solution obtained by the other method. However the present analysis discloses an anomaly of this similarity solution, which is associated with the behavior at infinity.

Kambe, T.

1989-07-01

469

Stability of a vortex sheet roll-up  

NASA Astrophysics Data System (ADS)

The stability of vortex sheet roll-up is studied using a Lagrangian vortex method. We consider an initially unstable (Kelvin-Helmholtz) vortex sheet. During its nonlinear evolution, a perturbation is added to test it for a secondary instability. The growth of the perturbation depends on its phase and on the local strain rate. In the linear stage of this secondary instability, the dispersion relation is calculated. It is found that the growth rate and the cutoff wave number are fixed by the regularization parameter of the Birkhoff-Rott equation.

Abid, Malek; Verga, Alberto

2002-11-01

470

Fractional vortex in asymmetric 0-? long Josephson junctions  

NASA Astrophysics Data System (ADS)

We consider an infinitely long 0-? Josephson junction consisting of 0 and ? regions having different critical current densities jc,0 and jc,?. The ground state of such a junction corr