Science.gov

Sample records for wind shear

  1. CAT LIDAR wind shear studies

    NASA Technical Reports Server (NTRS)

    Goff, R. W.

    1978-01-01

    The studies considered the major meteorological factors producing wind shear, methods to define and classify wind shear in terms significant from an aircraft perturbation standpoint, the significance of sensor location and scan geometry on the detection and measurement of wind shear, and the tradeoffs involved in sensor performance such as range/velocity resolution, update frequency and data averaging interval.

  2. Structure of wind-shear turbulence

    NASA Technical Reports Server (NTRS)

    Trevino, G.; Laituri, T. R.

    1989-01-01

    The statistical characteristics of wind shear turbulence are modelled. Isotropic turbulence serves as the basis of comparison for the anisotropic turbulence which exists in wind shear. The question of turbulence scales in wind shear is addressed from the perspective of power spectral density.

  3. Structure of wind-shear turbulence

    NASA Technical Reports Server (NTRS)

    Trevino, G.; Laituri, T. R.

    1988-01-01

    The statistical characteristics of wind-shear turbulence are modelled. Isotropic turbulence serves as the basis of comparison for the anisotropic turbulence which exists in wind shear. The question of how turbulence scales in a wind shear is addressed from the perspective of power spectral density.

  4. Wind shear modeling for aircraft hazard definition

    NASA Technical Reports Server (NTRS)

    Frost, W.; Camp, D. W.; Wang, S. T.

    1978-01-01

    Mathematical models of wind profiles were developed for use in fast time and manned flight simulation studies aimed at defining and eliminating these wind shear hazards. A set of wind profiles and associated wind shear characteristics for stable and neutral boundary layers, thunderstorms, and frontal winds potentially encounterable by aircraft in the terminal area are given. Engineering models of wind shear for direct hazard analysis are presented in mathematical formulae, graphs, tables, and computer lookup routines. The wind profile data utilized to establish the models are described as to location, how obtained, time of observation and number of data points up to 500 m. Recommendations, engineering interpretations and guidelines for use of the data are given and the range of applicability of the wind shear models is described.

  5. Flight in low-level wind shear

    NASA Technical Reports Server (NTRS)

    Frost, W.

    1983-01-01

    Results of studies of wind shear hazard to aircraft operation are summarized. Existing wind shear profiles currently used in computer and flight simulator studies are reviewed. The governing equations of motion for an aircraft are derived incorporating the variable wind effects. Quantitative discussions of the effects of wind shear on aircraft performance are presented. These are followed by a review of mathematical solutions to both the linear and nonlinear forms of the governing equations. Solutions with and without control laws are presented. The application of detailed analysis to develop warning and detection systems based on Doppler radar measuring wind speed along the flight path is given. A number of flight path deterioration parameters are defined and evaluated. Comparison of computer-predicted flight paths with those measured in a manned flight simulator is made. Some proposed airborne and ground-based wind shear hazard warning and detection systems are reviewed. The advantages and disadvantages of both types of systems are discussed.

  6. Summary Proceedings of a Wind Shear Workshop

    NASA Technical Reports Server (NTRS)

    Enders, J. H.; Melvin, W. W.; Frost, W.; Camp, D. W.

    1983-01-01

    A number of recent program results and current issues were addressed: the data collection phase of the highly successful Joint Airport Weather Study (JAWS) Project and the NASA-B5f7B Gust Gradient Program, the use of these data for flight crew training through educational programs (e.g., films) and with manned flight training simulators, methods for post-accident determination of wind conditions from flight data recorders, the microburst wind shear phenomenon which was positively measured and described the ring vortex as a possible generating mechanism, the optimum flight procedure for use during an unexpected wind shear encounter, evaluation of the low-level wind shear alert system (LLWSAS), and assessment of the demonstrated and viable application of Doppler radar as an operational wind shear warning and detection system.

  7. Wind shear and turbulence simulation

    NASA Technical Reports Server (NTRS)

    Bowles, Roland L.

    1987-01-01

    The aviation community is increasing its reliance on flight simulators. This is true both in pilot training and in research and development. In moving research concepts through the development pipeline, there is a sequence of events which take place: analysis, ground based simulation, inflight simulation, and flight testing. Increasing fidelity as progress toward the flight testing arena is accompanied by increasing cost. The question that seems to be posed in relation to the meteorological aspects of flight simulation is, How much fidelity is enough and can it be quantified. As a part of the Langley Simulation Technology Program, there are three principal areas of focus, one being improved simulation of weather hazards. A close liaison with the JAWS project was established because of the Langley Simulation Technology interests regarding reliable simulation of severe convective weather phenomena and their impact on aviation systems. Simulation offers the only feasible approach for examining the utility of new technology and new procedures for coping with severe convective weather phenomena such as wind shear. These simulation concepts are discussed in detail.

  8. Pulsed laser Doppler measurements of wind shear

    NASA Technical Reports Server (NTRS)

    Dimarzio, C.; Harris, C.; Bilbro, J. W.; Weaver, E. A.; Burnham, D. C.; Hallock, J. N.

    1979-01-01

    There is a need for a sensor at the airport that can remotely detect, identify, and track wind shears near the airport in order to assure aircraft safety. To determine the viability of a laser wind-shear system, the NASA pulsed coherent Doppler CO2 lidar (Jelalian et al., 1972) was installed in a semitrailer van with a rooftop-mounted hemispherical scanner and was used to monitor thunderstorm gust fronts. Wind shears associated with the gust fronts at the Kennedy Space Center (KSC) between 5 July and 4 August 1978 were measured and tracked. The most significant data collected at KSC are discussed. The wind shears were clearly visible in both real-time velocity vs. azimuth plots and in postprocessing displays of velocities vs. position. The results indicate that a lidar system cannot be used effectively when moderate precipitation exists between the sensor and the region of interest.

  9. Probabilistic reasoning for intelligent wind shear avoidance

    NASA Technical Reports Server (NTRS)

    Stratton, D. Alexander; Stengel, Robert F.

    1990-01-01

    A computerized intelligent cockpit aid can increase flight-crew awareness of wind shear, improving avoidance decisions. The FAA Windshear Training Aid (WTA) provides guidelines for assessing the risk of wind shear encounter from meteorological evidence. Use of these guidelines in the cockpit is complicated by uncertainty surrounding meteorological knowledge of wind shear. Bayesian network representation is discussed as a means of modeling this uncertain knowledge in a computer. A probabilistic model of the WTA guidelines using Bayesian network representation is presented. This model combines evidence from sources of varying reliability and incorporates results from meteorological studies of wind shear. The probabilistic model can provide flight crews with meaningful estimates of risk to aid their decisions, using evidence from a variety of sources and a base of meteorological knowledge.

  10. Wind shear related research at Princeton University

    NASA Technical Reports Server (NTRS)

    Stengel, Robert

    1992-01-01

    The topics addressed are: (1) real-time decision aiding-aircraft guidance for wind shear avoidance; (2) reducing the thrust-manual recovery strategies; and (3) dynamic behaviour of and aircraft encountering a single axis vortex.

  11. Unresolved issues in wind shear encounters

    NASA Technical Reports Server (NTRS)

    Stengel, Robert F.

    1987-01-01

    Much remains to be learned about the hazards of low altitude wind shear to aviation. New research should be conducted on the nature of the atmospheric environment, on aircraft performance, and on guidance and control aids. In conducting this research, it is important to distinguish between near-term and far-term objectives, between basic and applied research, and between uses of results for aircraft design or for real-time implementation. Advances in on-board electronics can be applied to assuring that aircraft of all classes have near optimal protection against wind shear hazards.

  12. Flight penetration of wind shear: Control strategies

    NASA Technical Reports Server (NTRS)

    Joshi, Amit S.

    1988-01-01

    Wind shear is a dangerous condition where there is a sharp change in the direction and magnitude of the wind velocity over a short distance or time. This condition is especially dangerous to aircraft during landing and takeoff and can cause a sudden loss of lift and thereby height at a critical time. A numerical simulation showed the effective performance of the Linear Quadratic Regulator and the Nonlinear Inverse Dynamics controllers. The major conclusions are listed and discussed.

  13. Infrared low-level wind shear work

    NASA Technical Reports Server (NTRS)

    Adamson, Pat

    1988-01-01

    Results of field experiments for the detection of clear air disturbance and low level wind shear utilizing an infrared airborne system are given in vugraph form. The hits, misses and nuisance alarms scores are given. Information is given on the infrared spatial resolution technique. The popular index of aircraft hazard (F= WX over g - VN over AS) is developed for a remote temperature sensor.

  14. Progress on Intelligent Guidance and Control for Wind Shear Encounter

    NASA Technical Reports Server (NTRS)

    Stratton, D. Alexander

    1990-01-01

    Low altitude wind shear poses a serious threat to air safety. Avoiding severe wind shear challenges the ability of flight crews, as it involves assessing risk from uncertain evidence. A computerized intelligent cockpit aid can increase flight crew awareness of wind shear, improving avoidance decisions. The primary functions of a cockpit advisory expert system for wind shear avoidance are discussed. Also introduced are computational techniques being implemented to enable these primary functions.

  15. Wind shear training applications for 91/135

    NASA Technical Reports Server (NTRS)

    Arbon, ED

    1991-01-01

    The requirement for wind shear training of all pilots has been demonstrated too often by the accident statistics of past years. Documents were developed to train airline crews on specific aircraft and to teach recognition of the meteorological conditions that are conducive to wind shear and microburst formation. A Wind Shear Training Aid program is discussed.

  16. Wind Shear Characteristics at Central Plains Tall Towers (presentation)

    SciTech Connect

    Schwartz, M.; Elliott, D.

    2006-06-05

    The objectives of this report are: (1) Analyze wind shear characteristics at tall tower sites for diverse areas in the central plains (Texas to North Dakota)--Turbines hub heights are now 70-100 m above ground and Wind measurements at 70-100+ m have been rare. (2) Present conclusions about wind shear characteristics for prime wind energy development regions.

  17. Wind shear predictive detector technology study status

    NASA Technical Reports Server (NTRS)

    Gandolfi, C.

    1990-01-01

    Among the different elements to be investigated when considering the Wind Shear hazard, the Aeronautical Navigation Technical Service (STNA/3E), whose task is to participate in the development of new technologies and equipments, focused its effort on airborne and ground sensors for the detection of low-level wind shear. The first task, initiated in 1986, consists in the evaluation of three candidate techniques for forward-looking sensors: lidar, sodar, and radar. No development is presently foreseen for an infrared based air turbulence advance warning system although some flight experiments took place in the 70's. A Thomson infrared radiometer was then installed on an Air France Boeing 707 to evaluate its capability of detecting clear air turbulence. The conclusion showed that this technique was apparently able to detect cloud layers but that additional experiments were needed; on the other hand, the rarity of the phenomenon and the difficulty in operating on a commercial aircraft were also mentioned.

  18. Optimal recovery from microburst wind shear

    NASA Technical Reports Server (NTRS)

    Mulgund, Sandeep S.

    1993-01-01

    Severe low-altitude wind variability represents an infrequent but significant hazard to aircraft taking off or landing. During the period from 1964 to 1985, microburst wind shear was a contributing factor in at least 26 civil aviation accidents involving nearly 500 fatalities and over 200 injuries. A microburst is a strong localized downdraft that strikes the ground, creating winds that diverge radially from the impact point. The physics of microbursts have only been recently understood in detail, and it has been found that effective recovery from inadvertent encounters may require piloting techniques that are counter-intuitive to flight crews. The goal of this work was to optimize the flight path of a twin-jet transport aircraft encountering a microburst during approach to landing. The objective was to execute an escape maneuver that maintained safe ground clearance and an adequate stall margin during the climb-out portion of the trajectory.

  19. Microbursts as an aviation wind shear hazard

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.

    1981-01-01

    The downburst-related accidents or near-misses of jet aircraft have been occurring at the rate of once or twice a year since 1975. A microburst with its field comparable to the length of runways can induce a wind shear which endangers landing or liftoff aircraft; the latest near miss landing of a 727 aircraft at Atlanta, Ga. in 1979 indicated that some microbursts are too small to trigger the warning device of the anemometer network at major U.S. airports. The nature of microbursts and their possible detection by Doppler radar are discussed, along with proposed studies of small-scale microbursts.

  20. Airborne infrared low level wind shear predictor

    NASA Technical Reports Server (NTRS)

    Kuhn, P. M.; Kurkowski, R. L.

    1984-01-01

    The operating principles and test performance of an airborne IR (13-16 micron) temperature-sensing detection and warning system for low-level wind shear (LLWS) are presented. The physics of LLWS phenomena and of the IR radiometer are introduced. The cold density-current outflow or gust front related to LLWS is observed in the IR spectrum of CO2 by a radiometer with + or - 0.5-C accuracy at 0.5-Hz sampling rate; LLWS alerts are given on the basis of specific criteria. Test results from the JAWS experiments conducted at Denver in July 1982, are presented graphically and discussed. The feasibility of the passive IR system is demonstrated, with an average warning time of 51 sec, corresponding to a distance from touchdown of about 2 miles.

  1. Impact of Vertical Wind Shear on Tropical Cyclone Rainfall

    NASA Technical Reports Server (NTRS)

    Cecil, Dan; Marchok, Tim

    2014-01-01

    While tropical cyclone rainfall has a large axisymmetric component, previous observational and theoretical studies have shown that environmental vertical wind shear leads to an asymmetric component of the vertical motion and precipitation fields. Composites consistently depict a precipitation enhancement downshear and also cyclonically downwind from the downshear direction. For consistence with much of the literature and with Northern Hemisphere observations, this is subsequently referred to as "Downshear-Left". Stronger shear magnitudes are associated with greater amplitude precipitation asymmetries. Recent work has reinforced the prior findings, and explored details of the response of the precipitation and kinematic fields to environmental vertical wind shear. Much of this research has focused on tropical cyclones away from land, to limit the influence of other processes that might distort the signal related to vertical wind shear. Recent evidence does suggest vertical wind shear can also play a major role in precipitation asymmetries during and after landfall.

  2. Pilot-aircraft system response to wind shear

    NASA Technical Reports Server (NTRS)

    Turkel, B. S.; Frost, W.; Camp, D. W.

    1980-01-01

    The nonlinear aircraft motion and automatic control computer model of Frost and Reddy has been expanded to incorporate the human pilot into simulations of aircraft response to wind shear. Fixed-stick, autopilot, and manned computer simulations are made with an aircraft having characteristics of a Queen Air (small commuter-type aircraft) flown through longitudinal winds measured by a Doppler radar beamed along the glide slope during the SESAME '79 experiments in Oklahoma. Simulations are also made flying a model Boeing 727 through sinusoidal head wind to tail wind shears at the phugoid frequency to evaluate the response of manned aircraft in thunderstorm wind environments.

  3. Quantifying shear-induced wave transformations in the solar wind

    E-print Network

    Grigol Gogoberidze; Andria Rogava; Stefaan Poedts

    2007-03-20

    The possibility of velocity shear-induced linear transformations of different magnetohydrodynamic waves in the solar wind is studied both analytically and numerically. A quantitative analysis of the wave transformation processes for all possible plasma-$\\beta$ regimes is performed. By applying the obtained criteria for effective wave coupling to the solar wind parameters, we show that velocity shear-induced linear transformations of Alfv\\'en waves into magneto-acoustic waves could effectively take place for the relatively low-frequency Alfv\\'en waves in the energy containing interval. The obtained results are in a good qualitative agreement with the observed features of density perturbations in the solar wind.

  4. Study of the Low Level Wind Shear using AMDAR reports

    NASA Astrophysics Data System (ADS)

    Urlea, Ana-Denisa; Pietrisi, Mirela

    2015-04-01

    The aim of this work is the study of the effects of the wind shear on aircraft flights, in particularly when it appears on path of take-off or landing phase which is the most troublesome phase. This phenomenon has a lot of generating sources as: convection, frontal surfaces, strong surface wind coupled with local topography, breezes (either sea or mountain originated), mountain waves or low level temperature inversions. Low Level Jet is also a most frequent cause of Low Level Wind Shear. It has a lot of generating causes, but in Romania the most encountered is the presence of a Mediterranean low in southeastern part of Europe mainly in winter, sometimes in the first days of spring or the last days of autumn. It generates Low Level Wind Shear between surface and up to 600m, affecting approaching, landing or take-off phases of an aircraft flight. Diagnosis of meteorological general and local conditions and presence of Low Level Jet- generating Low Level Wind Shear is made using Meteo-France ARPEGE products model and ALARO high resolution model dedicated to Romanian area. The study is focused on use of real-time and in situ data as AMDAR (Aircraft Meteorological Data Relay) registrations with verification of a mobile Doppler SODAR registrations-("SOnic Detection And Ranging" system -PCS.2000- Metek manufactured by Meteorologische Messtechnik GMBH) in the processes of estimation of the quantitative and qualitative manifestation of Low Level Wind Shear. The results will be used to improve the timing and the accuracy of the Low Level Wind Shear forecasting for the aerodrome area.

  5. The influence of wind shear on aerodynamic coefficients

    NASA Technical Reports Server (NTRS)

    Frost, W.; Hutto, E.

    1974-01-01

    The purpose of this study is to investigate the influence of wind shear on the lift, drag, roll and yaw moments of a wing in a horizontal wind gradient at various elevations and roll angles. The models of wind shear considered are those proposed by Leurs (1973) for atmospheric flow over horizontally homogeneous and uniform terrain. A general series solution for the distribution of lift along the wing span following the method of Houghton and Brock (1970) is employed to compute the loads and moments on the airfoil. Results of the computations indicate that wind shear can have a significant effect on the rolling and yawing moments of the wing of an aircraft flying with one wing low in the atmospheric boundary layer. These moments are directly influenced by the magnitude of the wind gradient in the neutral atmosphere reflected by the magnitude of the friction velocity. The effect of wind shear on lift and drag is negligible. Stability of the atmosphere tends to increase the magnitude of the rolling moment while decreasing its variation with elevation.

  6. Intelligent guidance and control for wind shear encounter

    NASA Technical Reports Server (NTRS)

    Stengel, Robert F.

    1988-01-01

    The principal objective is to develop methods for assessing the likelihood of wind shear encounter, for deciding what flight path to pursue, and for using the aircraft's full potential for combating wind shear. This study requires the definition of both deterministic and statistical techniques for fusing internal and external information, for making go/no-go decisions, and for generating commands to the aircraft's cockpit displays and autopilot for both manually controlled and automatic flight. The program has begun with the development of a real-time expert system for pilot aiding that is based on the results of the FAA Windshear Training Aids Program. A two-volume manual that presents an overview, pilot guide, training program, and substantiating data provides guidelines for this initial development. The Expert System to Avoid Wind Shear (ESAWS) currently contains over 140 rules and is coded in the LISP programming language for implementation on a Symbolics 3670 LISP machine.

  7. Temperature lapse rate as an adjunct to wind shear detection

    NASA Technical Reports Server (NTRS)

    Zweifil, Terry

    1991-01-01

    Several meteorological parameters were examined to determine if measurable atmospheric conditions can improve windshear detection devices. Lapse rate, the temperature change with altitude, shows promise as being an important parameter in the prediction of severe wind shears. It is easily measured from existing aircraft instrumentation, and it can be important indicator of convective activity including thunderstorms and microbursts. The meteorological theory behind lapse rate measurement is briefly reviewed, and and FAA certified system is described that is currently implemented in the Honeywell Wind Shear Detection and Guidance System.

  8. The relationship of an integral wind shear hazard to aircraft performance limitations

    NASA Technical Reports Server (NTRS)

    Lewis, M. S.; Robinson, P. A.; Hinton, D. A.; Bowles, R. L.

    1994-01-01

    The development and certification of airborne forward-looking wind shear detection systems has required a hazard definition stated in terms of sensor observable wind field characteristics. This paper outlines the definition of the F-factor wind shear hazard index and an average F-factor quantity, calculated over a specified averaging interval, which may be used to judge an aircraft's potential performance loss due to a given wind shear field. A technique for estimating airplane energy changes during a wind shear encounter is presented and used to determine the wind shear intensity, as a function of the averaging interval, that presents significant hazard to transport category airplanes. The wind shear hazard levels are compared to averaged F-factor values at various averaging intervals for four actual wind shear encounters. Results indicate that averaging intervals of about one kilometer could be used in a simple method to discern hazardous shears.

  9. Reinforcement Learning for Autonomous Dynamic Soaring in Shear Winds

    E-print Network

    Spletzer, John R.

    Reinforcement Learning for Autonomous Dynamic Soaring in Shear Winds Corey Montella and John R. Spletzer Abstract-- Dynamic soaring (DS) is an aerobatic maneuver whereby a gliding aircraft harnesses approaches to dynamic soaring in autonomous unmanned aerial vehicles (UAVs) use nonlinear optimizers

  10. Status of NASA's IR wind shear detection research

    NASA Technical Reports Server (NTRS)

    Mckissick, Burnell

    1991-01-01

    The status of NASA's wind shear detection research is reported in viewgraph form. Information is given on early experience, FLIR detectors, quantities measured by Airborne Warning and Avoidance System 1 (AWAS 1), the time series model for Flight 551, conclusions from NASA 737 flights, conclusions on Orlando 7-7-90, and AWAS 3 mnemonics.

  11. Doppler weather radar with predictive wind shear detection capabilities

    NASA Technical Reports Server (NTRS)

    Kuntman, Daryal

    1991-01-01

    The status of Bendix research on Doppler weather radar with predictive wind shear detection capability is given in viewgraph form. Information is given on the RDR-4A, a fully coherent, solid state transmitter having Doppler turbulence capability. Frequency generation data, plans, modifications, system characteristics and certification requirements are covered.

  12. Investigations of high latitude wind shears in the lower thermosphere

    NASA Astrophysics Data System (ADS)

    Marshall, Timothy Richard

    The Atmospheric Response in Aurora (ARIA) rocket campaign of March 1992 represented an effort to measure the effect of the prolonged heating due to a diffuse aurora on the neutral atmosphere. A previous model had predicted strong zonal winds in the lower thermosphere as the result of the strong coupling between the ionosphere and neutral atmosphere. An instrumented payload was launched into the diffuse aurora to measure neutral and plasma compositions, and two chemical releases provided the neutral wind measurements. In addition to this data, ground-based magnetometers and satellite measurements of the interplanetary magnetic field (IMF), electric fields, particle precipitation, and ram drift were incorporated into the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure. The AMIE procedure provided patterns of the electrostatic potential, electric fields, conductivities, and Joule heating on a global scale. The results of this analysis show the activity the chemical release of March 3 occurred in the region of greatest Joule heating. The neutral wind profile show strong wind shear existing at 115 km altitude, approximately the same altitude of the maximum electron density measured by the instrumented payload. This feature had a magnitude of approximately 150 m/s and was in the direction of the auroral electric field (southwestward). These wind shears coexisting with maximum's in electron densities have been studied for many years from chemical releases done at midlatitudes. The explanation for the midlatitude wind shears however fails to explain the high latitude wind shears seen in the ARIA release due to the vertical nature of the magnetic field. At auroral latitudes the electron density does not build up like at lower latitudes. In order to investigate high latitude wind shears, 15 additional high latitude chemical release experiments, performed by Heppner during the 1970's, have been reanalyzed. A steady state solution called modified geostrophic adjustment is used in attempting to model these features. This model is simply a balance of the pressure gradient, Corolis and Lorentz forces. By incorporating the Time Dependent Ionospheric Model (TDIM) of Utah State, along with a model neutral atmosphere provided by MSIS90E, wind simulations were compared with sixteen chemical release experiments. Simulation results show the presence of wind shears around 120 km altitude whenever the electron density profile shows a maximum at approximately that height. The existence of this wind shear is shown to be dependent on the Hall conductivity, which can dominate the Pedersen conductivity at lower thermospheric heights. The magnitude of the wind shear produced in the steady-state solution is also observed to be dependent on the strength of the imposed electric field. Comparisons of these modeled velocities with the neutral wind profiles obtained from the Heppner chemical releases show varied results depending on the stability of the prevailing conditions, but results from the ARIA release compare quite well due to the prolonged heating due to the diffuse aurora.

  13. Air/ground wind shear information integration: Flight test results

    NASA Technical Reports Server (NTRS)

    Hinton, David A.

    1992-01-01

    An element of the NASA/FAA wind shear program is the integration of ground-based microburst information on the flight deck, to support airborne wind shear alerting and microburst avoidance. NASA conducted a wind shear flight test program in the summer of 1991 during which airborne processing of Terminal Doppler Weather Radar (TDWR) data was used to derive microburst alerts. High level microburst products were extracted from TDWR, transmitted to a NASA Boeing 737 in flight via data link, and processed to estimate the wind shear hazard level (F-factor) that would be experienced by the aircraft in the core of each microburst. The microburst location and F-factor were used to derive a situation display and alerts. The situation display was successfully used to maneuver the aircraft for microburst penetrations, during which in situ 'truth' measurements were made. A total of 19 penetrations were made of TDWR-reported microburst locations, resulting in 18 airborne microburst alerts from the TDWR data and two microburst alerts from the airborne in situ measurements. The primary factors affecting alerting performance were spatial offset of the flight path from the region of strongest shear, differences in TDWR measurement altitude and airplane penetration altitude, and variations in microburst outflow profiles. Predicted and measured F-factors agreed well in penetrations near microburst cores. Although improvements in airborne and ground processing of the TDWR measurement would be required to support an airborne executive-level alerting protocol, the feasibility of airborne utilization of TDWR data link data has been demonstrated.

  14. Wind Shear/Turbulence Inputs to Flight Simulation and Systems Certification

    NASA Technical Reports Server (NTRS)

    Bowles, Roland L. (editor); Frost, Walter (editor)

    1987-01-01

    The purpose of the workshop was to provide a forum for industry, universities, and government to assess current status and likely future requirements for application of flight simulators to aviation safety concerns and system certification issues associated with wind shear and atmospheric turbulence. Research findings presented included characterization of wind shear and turbulence hazards based on modeling efforts and quantitative results obtained from field measurement programs. Future research thrusts needed to maximally exploit flight simulators for aviation safety application involving wind shear and turbulence were identified. The conference contained sessions on: Existing wind shear data and simulator implementation initiatives; Invited papers regarding wind shear and turbulence simulation requirements; and Committee working session reports.

  15. Aalborg Universitet Impact of Wind Shear and Tower Shadow Effects on Power System with Large Scale

    E-print Network

    Hu, Weihao

    and the power flow situation of the original power system especially when the integration of wind powerAalborg Universitet Impact of Wind Shear and Tower Shadow Effects on Power System with Large Scale., & Chen, Z. (2011). Impact of Wind Shear and Tower Shadow Effects on Power System with Large Scale Wind

  16. A theoretical analysis of airplane longitudinal stability and control as affected by wind shear

    NASA Technical Reports Server (NTRS)

    Sherman, W. L.

    1977-01-01

    The longitudinal equations of motion with wind shear terms were used to analyze the stability and motions of a jet transport. A positive wind shear gives a decreasing head wind or changes a head wind into a tail wind. A negative wind shear gives a decreasing tail wind or changes a tail wind into a head wind. It was found that wind shear had very little effect on the short period mode and that negative wind shear, although it affected the phugoid, did not cause stability problems. On the other hand, it was found that positive wind shear can cause the phugoid to become aperiodic and unstable. In this case, a stability boundary for the phugoid was found that is valid for most aircraft at all flight speeds. Calculations of aircraft motions confirmed the results of the stability analysis. It was found that a flight path control automatic pilot and an airspeed control system provide good control in all types of wind shear. Appendixes give equations of motion that include the effects of downdrafts and updrafts and extend the longitudinal equations of motion for shear to six degrees of freedom.

  17. A problem formulation for glideslope tracking in wind shear using advanced robust control techniques

    NASA Technical Reports Server (NTRS)

    Belcastro, Christine M.; Chang, B.-C.; Fischl, Robert

    1992-01-01

    A formulation of the longitudinal glideslope tracking of a transport-class aircraft in severe wind shear and turbulence for application to robust control system design is presented. Mathematical wind shear models are incorporated into the vehicle mathematical model, and wind turbulence is modeled as an input disturbance signal. For this problem formulation, the horizontal and vertical wind shear gradients are treated as real uncertain parameters that vary over an entire wind shear profile. The primary objective is to examine the formulation of this problem into an appropriate design format for use in m-synthesis control system design.

  18. Flight guidance research for recovery from microburst wind shear

    NASA Technical Reports Server (NTRS)

    Hinton, David A.

    1990-01-01

    Research is in progress to develop flight strategy concepts for avoidance and recovery from microburst wind shears. The objectives of this study are to evaluate the performance of various strategies for recovery from wind shear encountered during the approach-to-landing, examine the associated piloting factors, and evaluate the payoff of forward-look sensing. Both batch and piloted simulations are utilized. The industry-recommended manual recovery technique is used as a baseline strategy. Two advanced strategies were selected for the piloted tests. The first strategy emulates the recovery characteristics shown by prior optimal trajectory analysis, by initially tracking the glideslope, then commanding a shallow climb. The second strategy generates a flight path angle schedule that is a function of airplane energy state and the instantaneous shear strength. All three strategies are tested with reactive sensing only and with forward-look sensing. Piloted simulation tests are in progress. Tentative results indicate that, using only reactive alerts, there appears to be little difference in performance between the various strategies. With forward-look alerts, the advanced guidance strategies appear to have advantages over the baseline strategy. Relatively short forward-look alert times, on the order of 10 or 15 seconds, produce a far greater recovery benefit than optimizing a recovery from a reactive alert.

  19. Roles of wind shear at different vertical levels: Cloud system organization and properties

    NASA Astrophysics Data System (ADS)

    Chen, Qian; Fan, Jiwen; Hagos, Samson; Gustafson, William I.; Berg, Larry K.

    2015-07-01

    Understanding critical processes that contribute to the organization of mesoscale convective systems (MCSs) is important for accurate weather forecasts and climate predictions. In this study, we investigate the effects of wind shear at different vertical levels on the organization and properties of convective systems using the Weather Research and Forecasting model with spectral bin microphysics. Based on a control run for a MCS with weak wind shear (Ctrl), we find that increasing wind shear at the lower troposphere (L-shear) leads to a more organized quasi-line convective system. Strong wind shear in the middle troposphere (M-shear) tends to produce large vorticity and form a mesocyclone circulation and an isolated strong storm that leans toward supercellular structure. By increasing wind shear at the upper vertical levels only (U-shear), the organization of the convection is not changed much, but the convective intensity is weakened. Increasing wind shear in the middle troposphere for the selected case results in a significant drying, and the drying is more significant when conserving moisture advection at the lateral boundaries, contributing to the suppressed convective strength and precipitation relative to Ctrl. Precipitation in the L-shear and U-shear does not change much from Ctrl. Evident changes of cloud macrophysical and microphysical properties in the strong wind shear cases are mainly due to large changes in convective organization and water vapor. The insights obtained from this study help us better understand the major factors contributing to convective organization and precipitation.

  20. Simulation study to evaluate a constant-groundspeed approach method in moderate and severe wind shears

    NASA Technical Reports Server (NTRS)

    Kelley, W. W.

    1979-01-01

    The use of a constant-groundspeed procedure for flying final approaches in moderate and severe wind shear environments was investigated. Performance was compared to results of simulated constant-airspeed approaches in identical wind profiles. The simulation model was a medium twin-jet transport equipped with an autothrottle for maintaining constant groundspeed or constant airspeed. For both moderate and severe wind shears, the constant-groundspeed approach method was shown to provide a way to more safely negotiate the shears while also providing predictable and acceptable touchdown performance. Results showed airspeeds on final approach to be considerably higher using the constant-groundspeed method, which supplied the additional stall margin needed when tail-wind shears were encountered. Throttle movements were noticeably reduced in all wind profiles when constant-groundspeed approaches were flown. Touchdown conditions were practically identical for both approach methods in moderate wind shear.

  1. Shear and Turbulence Estimates for Calculation of Wind Turbine Loads and Responses Under Hurricane Strength Winds

    NASA Astrophysics Data System (ADS)

    Kosovic, B.; Bryan, G. H.; Haupt, S. E.

    2012-12-01

    Schwartz et al. (2010) recently reported that the total gross energy-generating offshore wind resource in the United States in waters less than 30m deep is approximately 1000 GW. Estimated offshore generating capacity is thus equivalent to the current generating capacity in the United States. Offshore wind power can therefore play important role in electricity production in the United States. However, most of this resource is located along the East Coast of the United States and in the Gulf of Mexico, areas frequently affected by tropical cyclones including hurricanes. Hurricane strength winds, associated shear and turbulence can affect performance and structural integrity of wind turbines. In a recent study Rose et al. (2012) attempted to estimate the risk to offshore wind turbines from hurricane strength winds over a lifetime of a wind farm (i.e. 20 years). According to Rose et al. turbine tower buckling has been observed in typhoons. They concluded that there is "substantial risk that Category 3 and higher hurricanes can destroy half or more of the turbines at some locations." More robust designs including appropriate controls can mitigate the risk of wind turbine damage. To develop such designs good estimates of turbine loads under hurricane strength winds are essential. We use output from a large-eddy simulation of a hurricane to estimate shear and turbulence intensity over first couple of hundred meters above sea surface. We compute power spectra of three velocity components at several distances from the eye of the hurricane. Based on these spectra analytical spectral forms are developed and included in TurbSim, a stochastic inflow turbulence code developed by the National Renewable Energy Laboratory (NREL, http://wind.nrel.gov/designcodes/preprocessors/turbsim/). TurbSim provides a numerical simulation including bursts of coherent turbulence associated with organized turbulent structures. It can generate realistic flow conditions that an operating turbine would encounter under hurricane strength winds. These flow fields can be used to estimate wind turbine loads and responses with AeroDyn (http://wind.nrel.gov/designcodes/simulators/aerodyn/) and FAST (http://wind.nrel.gov/designcodes/simulators/fast/) codes also developed by NREL.

  2. Detection Probability Modeling for Airport Wind-Shear August 28, 2008

    E-print Network

    Cho, John Y. N.

    -sensor performer for microburst and gust-front detection among the considered wind-shear sensing systems. Also the required 90% microburst detection probability at many airports, even after the planned upgrade to its wind-shear detection coverage. The typical LLWAS detection probability for microbursts was low (~50

  3. Analysis of strong nocturnal shears for wind machine design. Final report

    SciTech Connect

    Mahrt, L.; Heald, R.C.

    1980-11-01

    Wind shear data at wind turbine heights from several sites is reviewed and new data is documented in terms of total and component shear. A variety of atmospheric scenarios may combine to give large persistent shear. Among these, strong boundary layer stability is foremost. It occurs with strong nocturnal surface cooling, in low level frontal and subsidence inversions, and in thunderstorm outflows. Strong shears resulting from surface radiation inversions are particularly evident over the High Plains where dry air and high altitude combine to result in strong radiational cooling. Terrain is also an important influence on shear but it is not well understood and is very site specific.

  4. Algorithms for airborne Doppler radar wind shear detection

    NASA Technical Reports Server (NTRS)

    Gillberg, Jeff; Pockrandt, Mitch; Symosek, Peter; Benser, Earl T.

    1992-01-01

    Honeywell has developed algorithms for the detection of wind shear/microburst using airborne Doppler radar. The Honeywell algorithms use three dimensional pattern recognition techniques and the selection of an associated scanning pattern forward of the aircraft. This 'volumetric scan' approach acquires reflectivity, velocity, and spectral width from a three dimensional volume as opposed to the conventional use of a two dimensional azimuthal slice of data at a fixed elevation. The algorithm approach is based on detection and classification of velocity patterns which are indicative of microburst phenomenon while minimizing the false alarms due to ground clutter return. Simulation studies of microburst phenomenon and x-band radar interaction with the microburst have been performed and results of that study are presented. Algorithm performance indetection of both 'wet' and 'dry' microbursts is presented.

  5. Optimal nonlinear estimation for aircraft flight control in wind shear

    NASA Technical Reports Server (NTRS)

    Mulgund, Sandeep S.

    1994-01-01

    The most recent results in an ongoing research effort at Princeton in the area of flight dynamics in wind shear are described. The first undertaking in this project was a trajectory optimization study. The flight path of a medium-haul twin-jet transport aircraft was optimized during microburst encounters on final approach. The assumed goal was to track a reference climb rate during an aborted landing, subject to a minimum airspeed constraint. The results demonstrated that the energy loss through the microburst significantly affected the qualitative nature of the optimal flight path. In microbursts of light to moderate strength, the aircraft was able to track the reference climb rate successfully. In severe microbursts, the minimum airspeed constraint in the optimization forced the aircraft to settle on a climb rate smaller than the target. A tradeoff was forced between the objectives of flight path tracking and stall prevention.

  6. Small scale structure in uniform wind tunnel turbulent shear flow

    NASA Astrophysics Data System (ADS)

    Shen, Xiaochun

    Wind tunnel uniform turbulent shear flows were set up to test the postulate of local isotropy (PLI). The Reynolds number was varied in the range 100 ? Rl ? 1200. It was shown that while PLI is well obeyed at the 2nd order, it is violated starting at the 3rd order in the inertial range and at the 5th order in the dissipation range. In particular, PLI requires the odd order statistics in the shear direction (y direction) approach zero as Rl ? infinity. In the dissipation range, although the skewness of ? u/?y, S36u/6y , decreased with Rl (as R-0.54l ), the 5th order normalized moment of ?u/?y, S56u/6y , was of order 10, and showed no diminution with Reynolds number ( ˜R0l ). The 7th order normalized moment of ?u/?y, S76u/6y , increased with Reynolds number ( ˜R0.58l ). Within the inertial range at Rl ˜ 1000, the odd order transverse structure functions, Dnuu (Deltay) (n odd), were nonzero, exhibiting scaling ranges similar to the longitudinal structure functions, Dnuu (Deltax). The normalized 3rd order transverse structure function S3uu (Deltay) had a value ˜0.5; S5uu (Deltay) and S7uu (Deltay) were of order 10 and 100, respectively. Both the inertial range and dissipation range transverse statistics indicate, at least to Rl ˜ 1000, PLI is untenable. It was also shown that the scaling exponents of Dnuu (Deltay) depended on Reynolds number but were independent of the mean shear. At low Reynolds number, they were smaller than the scaling exponents of Dnuu (Deltax). At high Reynolds number, they were the same as those of Dnuu (Deltax). The scaling exponents of the transverse structure functions, Dnvv (Deltax), were always smaller than the scaling exponents of Dnuu (Deltax). Their value were influenced both by Reynolds number and by the large scale anisotropy. The scaling exponents of the even order mixed structure functions that are explicitly zero in isotropic turbulence were determined for uniform turbulent shear flow at Rl ˜ 1000. The ratio of their scaling to those of Dnuu (Deltax) decreased systematically with increasing orders and were close to unity at the 8th order, suggesting at high orders, the anisotropic sectors are equally important as the isotropic sector at small scales.

  7. Wind turbine blade shear web disbond detection using rotor blade operational sensing and data analysis.

    PubMed

    Myrent, Noah; Adams, Douglas E; Griffith, D Todd

    2015-02-28

    A wind turbine blade's structural dynamic response is simulated and analysed with the goal of characterizing the presence and severity of a shear web disbond. Computer models of a 5?MW offshore utility-scale wind turbine were created to develop effective algorithms for detecting such damage. Through data analysis and with the use of blade measurements, a shear web disbond was quantified according to its length. An aerodynamic sensitivity study was conducted to ensure robustness of the detection algorithms. In all analyses, the blade's flap-wise acceleration and root-pitching moment were the clearest indicators of the presence and severity of a shear web disbond. A combination of blade and non-blade measurements was formulated into a final algorithm for the detection and quantification of the disbond. The probability of detection was 100% for the optimized wind speed ranges in laminar, 30% horizontal shear and 60% horizontal shear conditions. PMID:25583871

  8. Recognizing low-altitude wind shear hazards from Doppler weather radar - an artificial intelligence approach

    SciTech Connect

    Campbell, S.D.; Olson, S.H.

    1987-03-01

    This paper describes an artificial intelligence-based approach for automated recognition of wind shear hazards. The design of a prototype system for recognizing low-altitude wind shear events from Doppler radar displays is presented. This system, called WX1, consists of a conventional expert system augmented by a specialized capability for processing radar images. The radar image processing component of the system employs numerical and computer vision techniques to extract features from radar data. The expert system carries out symbolic reasoning on these features using a set of heuristic rules expressing meteorological knowledge about wind shear recognition. Results are provided demonstrating the ability of the system to recognize microburst and gust front wind shear events. 11 references.

  9. TRMM Satellite Shows Bertha's Heavy Rain Pushed From Wind Shear - Duration: 13 seconds.

    NASA Video Gallery

    TRMM Satellite Shows Bertha's Heavy Rain Pushed From Wind Shear This 3-D flyby of Tropical Storm Bertha on Aug. 1 was created from TRMM satellite data. It shows (from the south) intense thunderstor...

  10. Roles of Wind Shear at Different Vertical Levels, Part I: Cloud System Organization and Properties

    SciTech Connect

    Chen, Qian; Fan, Jiwen; Hagos, Samson M.; Gustafson, William I.; Berg, Larry K.

    2015-07-16

    Understanding of critical processes that contribute to the organization of mesoscale convective systems is important for accurate weather forecast and climate prediction. In this study, we investigate the effects of wind shear at different vertical levels on the organization and properties of cloud systems using the Weather Research & Forecasting (WRF) model with a spectral-bin microphysical scheme. The sensitivity experiments are performed by increasing wind shear at the lower (0-5 km), middle (5-10 km), upper (> 10 km) and the entire troposphere, respectively, based on a control run for a mesoscale convective system (MCS) with weak wind shear. We find that increasing wind shear at the both lower and middle vertical levels reduces the domain-accumulated precipitation and the occurrence of heavy rain, while increasing wind shear at the upper levels changes little on precipitation. Although increasing wind shear at the lower-levels is favorable for a more organized quasi-line system which leads to enlarged updraft core area, and enhanced updraft velocities and vertical mass fluxes, the precipitation is still reduced by 18.6% compared with the control run due to stronger rain evaporation induced by the low-level wind shear. Strong wind shear in the middle levels only produces a strong super-cell over a narrow area, leading to 67.3% reduction of precipitation over the domain. By increasing wind shear at the upper levels only, the organization of the convection is not changed much, but the increased cloudiness at the upper-levels leads to stronger surface cooling and then stabilizes the atmosphere and weakens the convection. When strong wind shear exists over the entire vertical profile, a deep dry layer (2-9 km) is produced and convection is severely suppressed. There are fewer very-high (cloud top height (CTH) > 15 km) and very-deep (cloud thickness > 15 km) clouds, and the precipitation is only about 11.8% of the control run. The changes in cloud microphysical properties further explain the reduction of surface rain by strong wind shear especially at the lower- and middle-levels. The insights obtained from this study help us better understand the cloud system organization and provide foundation for better parameterizing organized MCS.

  11. NASA experimental airborne doppler radar and real time processor for wind shear detection

    NASA Technical Reports Server (NTRS)

    Schaffner, Philip H.; Richards, Mark A.; Jones, William R.; Crittenden, Lucille H.

    1992-01-01

    The topics are presented in viewgraph form and include the following: experimental radar system capabilities; an experimental radar system block diagram; wind shear radar signal and data processor (WRSDP); WRSDP hardware architecture; WRSDP system design goals; DSP software development tools; OS-9 software development tools; WRSDP digital signal processing; WRSDP display operational modes; WRSDP division of functions; structure of WRSDP signal and data processing algorithms; and the wind shear radar flight experiment.

  12. Parametrization of convection with wind shear effect in global climate models

    NASA Astrophysics Data System (ADS)

    Cao, Zhiyu; Herzog, Michael; Graf, Hans

    2015-04-01

    Convection is a fundamental process in the climate system and remains one of the major uncertainties in our understanding and numerical modeling of the atmosphere. It manifests itself as cumulus clouds that are parameterized in global climate models due to their subgrid scale nature. Wind shear affects entrainment and plays a key role in the formation and growth of cumulus clouds. Strong wind shear inhibits the growth of cumulus clouds by disrupting or weakening the conditional instability. The Convective Cloud Field Model (CCFM) is a spectral mass flux parameterization, consisting of a one-dimensional entraining parcel model for individual convective clouds and a calculation of the cloud spectrum for the number of convective clouds. The wind shear effect can be parameterized by the entrainment rate. The entrainment rate in a windy environment is calculated in three dimensions in which the motion of parcel, ambient air and the plume angle are considered. The horizontal dynamics of cumulus clouds is introduced in the entraining parcel model based on the conservation of horizontal momentum. CCFM with wind shear effects has been successfully implemented and tested within the ECHAM6 climate model. We will presents the parameterization of wind shear effects and discuss their impact within ECHAM6, with a particular focus on tropical precipitation distributions. Keywords: convection, entrainment, wind shear effect

  13. Power spectral density analysis of wind-shear turbulence for related flight simulations. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Laituri, Tony R.

    1988-01-01

    Meteorological phenomena known as microbursts can produce abrupt changes in wind direction and/or speed over a very short distance in the atmosphere. These changes in flow characteristics have been labelled wind shear. Because of its adverse effects on aerodynamic lift, wind shear poses its most immediate threat to flight operations at low altitudes. The number of recent commercial aircraft accidents attributed to wind shear has necessitated a better understanding of how energy is transferred to an aircraft from wind-shear turbulence. Isotropic turbulence here serves as the basis of comparison for the anisotropic turbulence which exists in the low-altitude wind shear. The related question of how isotropic turbulence scales in a wind shear is addressed from the perspective of power spectral density (psd). The role of the psd in related Monte Carlo simulations is also considered.

  14. The detection and measurement of microburst wind shear by an airborne lidar system

    NASA Technical Reports Server (NTRS)

    Robinson, Paul A.; Bowles, Roland L.; Targ, Russell

    1993-01-01

    The NASA Lockheed Missiles and Space Company (LMSC) Coherent Lidar Airborne Shear Sensor (CLASS) employs coherent lidar technology as a basis for a forward-looking predictive wind shear detection system. Line of sight wind velocities measured ahead of the aircraft are combined with aircraft state parameters to relate the measured wind change (or shear) ahead of an aircraft to its performance loss or gain. In this way the system can predict whether a shear detected ahead of the aircraft poses a significant threat to the aircraft and provide an advance warning to the flight crew. Installed aboard NASA's Boeing 737 research aircraft, the CLASS system is flown through convective microburst wind shears in Denver, Co., and Orlando, Fl. Some preliminary flight test results are presented. It is seen that the system was able to detect and measure wind shears ahead of the aircraft in the relatively dry Denver environment, but its performance was degraded in the high humidity and heavy rain in Orlando.

  15. Total energy-rate feedback for automatic glide-slope tracking during wind-shear penetration

    NASA Technical Reports Server (NTRS)

    Belcastro, C. M.; Ostroff, A. J.

    1984-01-01

    Low-altitude wind shear is recognized as an infrequent but significant hazard to all aircraft during the take-off and landing phases of flight. A total energy-rate sensor was developed for measuring the specific total energy rate of an airplane with respect to the air mass. Control-system designs, both with and without energy-rate feedback, for the approach to landing of a transport airplane through a severe-wind-shear and gust environment are presented in order to evaluate this application of the sensor. A system model incorporates wind-shear-dynamics equations with the airplane equations of motion to permit analysis of the control systems under various wind-shear conditions. The control systems are designed using optimal-output feedback and are analyzed using frequency-domain control-theory techniques. Control-system performance is evaluated using a complete nonlinear simulation of the airplane combined with a severe-wind-shear and gust data package. This evaluation is concerned with control system stability and regulation capability only.

  16. Climatological characteristics of high altitude wind shear and lapse rate layers

    NASA Technical Reports Server (NTRS)

    Ehernberger, L. J.; Guttman, N. B.

    1981-01-01

    Indications of the climatological distribution of wind shear and temperature lapse and inversion rates as observed by rawinsonde measurements over the western United States are recorded. Frequencies of the strongest shear, lapse rates, and inversion layer strengths were observed for a 1 year period of record and were tabulated for the lower troposphere, the upper troposphere, and five altitude intervals in the lower stratosphere. Selected bivariate frequencies were also tabulated. Strong wind shears, lapse rates, and inversion are observed less frequently as altitude increases from 175 millibars to 20 millibars. On a seasonal basis the frequencies were higher in winter than in summer except for minor influences due to increased tropopause altitude in summer and the stratospheric wind reversal in the spring and fall.

  17. Effects of vertical wind shear on the cumulus transport of momentum: Observations and parameterization

    SciTech Connect

    Wu, Xiaoqing; Yania, Michio )

    1994-06-01

    Dynamical effects of organized cumulus convection on its environment with vertical wind shear are studied. Analyses of the wind field and momentum budget residual for mesoscale convective systems observed during Severe Environmental Storms and Mesoscale Experiment (SESAME) and Preliminary Regional Experiment for Storm-Central (PRE-STORM) reveal systematic differences in the vertical transport of horizontal momentum between mesoscale convective complex (MCC) and squall line cases. In the MCC, a distinct minimum in wind speed appears over the area of intense convection and the momentum budget residual acts to decelerate the environmental wind and to reduce the upper-level vertical shear. Therefore, the inferred vertical transport of momentum in the MCC is downgradient in the upper layer. On the other hand, in the squall line, there is no wind speed minimum and the upper-level vertical shear of the line-normal component of the environmental wind increases as convection develops. Thus, the vertical transport of momentum normal to the squall line is upgradient in the upper layer, although the transport of momentum parallel to the line is downgradient. The effects of cumulus convection on the environmental flow are through the subsidence of environmental air that compensates the cloud mass flux, the detrainment of momentum from clouds, and the convective-scale horizontal pressure gradient force acting on the environment. A cumulus momentum parameterization including the convective-scale pressure gradient force is formu lated.

  18. Generation of auroral Omega bands by shear instability of the neutral winds

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.; Walterscheid, R. L.

    1985-01-01

    Thermospheric neutral wind acceleration via ion drag in the conducting E-region of the ionosphere is greatly increased by electron precipitation associated with auroras. This increased acceleration can lead to the development of significant horizontal wind shears, which were found to be unstable to the Kelvin-Helmholtz shear instability. Numerical simulation of the neutral response to an intense, postmidnight, diffuse aurora shows tne formation of an E-region 'jet stream' within the aurora, with peak winds speeds greather than 700 m/s after one hour. It is proposed that this jet stream produces unstable Kelvin-Helmholtz waves, which can drive waves of discrete aurora along the poleward boundary of the preexisting diffuse aurora. It is suggested that such auroral waves, driven by the neutral winds, form eastward propagating waves (omega bands) occasionally observed along the poleward boundary of postmidnight diffuse auroras. It was found that neutral wind shears that develop in response to discrete auroral arcs are unstable; however, the resulting wind waves are not expected to drive significant auroral waves along discrete arcs.

  19. Airborne Wind Shear Detection and Warning Systems: Third Combined Manufacturers' and Technologists' Conference, part 1

    NASA Technical Reports Server (NTRS)

    Vicroy, Dan D. (compiler); Bowles, Roland L. (compiler); Schlickenmaier, Herbert (compiler)

    1991-01-01

    Papers presented at the conference on airborne wind shear detection and warning systems are compiled. The following subject areas are covered: terms of reference; case study; flight management; sensor fusion and flight evaluation; Terminal Doppler Weather Radar data link/display; heavy rain aerodynamics; and second generation reactive systems.

  20. Vertical wind shear on Jupiter from Cassini images Liming Li,1

    E-print Network

    Vertical wind shear on Jupiter from Cassini images Liming Li,1 Andrew P. Ingersoll,1 Ashwin R 2006. [1] Multifilter images of Jupiter acquired by the Cassini Imaging Science Subsystem (ISS on Jupiter from Cassini images, J. Geophys. Res., 111, E04004, doi:10.1029/2005JE002556. 1. Introduction [2

  1. Airborne Doppler lidar detection of wind shear. Results of performance analysis

    NASA Technical Reports Server (NTRS)

    Huffaker, R. Milton

    1988-01-01

    Results of a performance analysis of an airborne Doppler radar wind shear detection system are given in vugraph form. It was concluded that both CO sub 2 and Ho:YAG lasers are feasible for dry microburst applications, but with limited performance in wet microbursts. The Ho:YAG performs better than the CO sub 2 for a set of identical lidar parameters.

  2. Effects of Vertical Wind Shear on the Predictability of Tropical Cyclones FUQING ZHANG AND DANDAN TAO

    E-print Network

    Thompson, Anne

    Effects of Vertical Wind Shear on the Predictability of Tropical Cyclones FUQING ZHANG AND DANDAN methods. A recent study by Zhang et al. (2011) showed that the hurricane intensity forecast ac- curacy can chaotic, less well understood, and intrinsically less predictable. The recent study of Zhang and Sippel

  3. Simultaneous measurements of wind shear and temperature gradient spectra in the stratosphere

    SciTech Connect

    Barat, J.; Cot, C. )

    1989-10-01

    The authors present in this paper the first high resolution analysis of wind shears and temperature gradient measured over 25 m in the low stratosphere. Their power spectral densities deduced by two different methods show that for vertical wavelengths greater than 500 m the behaviors of the temperature and vertical velocity fluctuating field are significantly different from the saturated wave model predictions.

  4. Application of infrared radiometers for airborne detection of clear air turbulence and low level wind shear, airborne infrared low level wind shear detection test

    NASA Technical Reports Server (NTRS)

    Kuhn, P. M.

    1985-01-01

    The feasibility of infrared optical techniques for the advance detection and avoidance of low level wind shear (LLWS) or low altitude wind shear hazardous to aircraft operations was investigated. A primary feasibility research effort was conducted with infrared detectors and instrumentation aboard the NASA Ames Research Center Learjet. The main field effort was flown on the NASA-Ames Dryden B57B aircraft. The original approach visualized a forward-looking, infrared transmitting (KRS-5) window through which signals would reach the detector. The present concept of a one inch diameter light pipe with a 45 deg angled mirror enables a much simpler installation virtually anywhere on the aircraft coupled with the possibility of horizontal scanning via rotation of the forward directed mirror. Present infrared detectors and filters would certainly permit ranging and horizontal scanning in a variety of methods. CRT display technology could provide a contoured picture with possible shear intensity levels from the infrared detection system on the weather radar or a small adjunct display. This procedure shoud be further developed and pilot evaluated in a light aircraft such as a Cessna 207 or equivalent.

  5. Contributions on the Subject of Longitudinal Movements of Aircraft in Wind Shears. Ph.D. Thesis - Technischen Univ., 1983

    NASA Technical Reports Server (NTRS)

    Krauspe, P.

    1985-01-01

    The effect of downburst-type wind shears on the longitudinal dynamic behavior of an unguided aircraft is simulated numerically on the basis of published meteorological data and the flight characteristics of an A300-B passenger jet. The nonlinear differential equations of the aircraft motion are linearized by conventional methods, and the wind effects are introduced via the linear derivatives of the wind components referred to the wind gradients to obtain simplified technical models of the longitudinal response to all possible types of constant-gradient wind shears during the first 20-60 sec. Graphs, maps, and diagrams are provided, and a number of accidents presumed to have involved wind shears are analyzed in detail.

  6. Feasibility study of a procedure to detect and warn of low level wind shear

    NASA Technical Reports Server (NTRS)

    Turkel, B. S.; Kessel, P. A.; Frost, W.

    1981-01-01

    A Doppler radar system which provides an aircraft with advanced warning of longitudinal wind shear is described. This system uses a Doppler radar beamed along the glide slope linked with an on line microprocessor containing a two dimensional, three degree of freedom model of the motion of an aircraft including pilot/autopilot control. The Doppler measured longitudinal glide slope winds are entered into the aircraft motion model, and a simulated controlled aircraft trajectory is calculated. Several flight path deterioration parameters are calculated from the computed aircraft trajectory information. The aircraft trajectory program, pilot control models, and the flight path deterioration parameters are discussed. The performance of the computer model and a test pilot in a flight simulator through longitudinal and vertical wind fields characteristic of a thunderstorm wind field are compared.

  7. Increased Tropical Atlantic Wind Shear in Model Projections of Global Warming

    NASA Astrophysics Data System (ADS)

    Vecchi, G. A.; Soden, B. J.

    2007-05-01

    To help understand possible impacts of anthropogenic greenhouse warming on hurricane activity, we assess model-projected changes in large-scale environmental factors tied to variations in hurricane statistics. This study focuses on vertical wind shear (Vs) over the tropical Atlantic during hurricane season, the increase of which has been historically associated with diminished hurricane activity and intensity. A suite of state-of-the-art global climate model experiments is used to project changes in Vs over the 21st century. Substantial (up to 30 percent) increases in tropical Atlantic and East Pacific shear are robust features of these experiments, and are shown to be connected to the model-projected decrease in the Pacific Walker circulation. The relative changes in shear are found to be comparable to those of other large-scale environmental parameters associated with Atlantic hurricane activity. The influence of these Vs changes should be incorporated into projections of long-term hurricane activity.

  8. Increased tropical Atlantic wind shear in model projections of global warming

    NASA Astrophysics Data System (ADS)

    Vecchi, Gabriel A.; Soden, Brian J.

    2007-04-01

    To help understand possible impacts of anthropogenic greenhouse warming on hurricane activity, we assess model-projected changes in large-scale environmental factors tied to variations in hurricane statistics. This study focuses on vertical wind shear (Vs) over the tropical Atlantic during hurricane season, the increase of which has been historically associated with diminished hurricane activity and intensity. A suite of state-of-the-art global climate model experiments is used to project changes in Vs over the 21st century. Substantial increases in tropical Atlantic and East Pacific shear are robust features of these experiments, and are shown to be connected to the model-projected decrease in the Pacific Walker circulation. The relative changes in shear are found to be comparable to those of other large-scale environmental parameters associated with Atlantic hurricane activity. The influence of these Vs changes should be incorporated into projections of long-term hurricane activity.

  9. Performance analysis and technical assessment of coherent lidar systems for airborne wind shear detection

    NASA Technical Reports Server (NTRS)

    Huffaker, R. Milton; Targ, Russell

    1988-01-01

    Detailed computer simulations of the lidar wind-measuring process have been conducted to evaluate the use of pulsed coherent lidar for airborne windshear monitoring. NASA data fields for an actual microburst event were used in the simulation. Both CO2 and Ho:YAG laser lidar systems performed well in the microburst test case, and were able to measure wind shear in the severe weather of this wet microburst to ranges in excess of 1.4 km. The consequent warning time gained was about 15 sec.

  10. Operational wind shear detection and warning - The 'CLAWS' experience at Denver and future objectives

    NASA Technical Reports Server (NTRS)

    Mccarthy, John; Wilson, James W.; Hjelmfelt, Mark R.

    1986-01-01

    An operational wind shear detection and warning experiment was conducted at Denver's Stapleton International Airport in summer 1984. Based on meteorological interpretation of scope displays from a Doppler weather radar, warnings were transmitted to the air traffic control tower via voice radio. Analyses of results indicated real skill in daily microburst forecasts and very short-term (less than 5-min) warnings. Wind shift advisories with 15-30 min forecasts, permitted more efficient runway reconfigurations. Potential fuel savings were estimated at $875,000/yr at Stapleton. The philosophy of future development toward an automated, operational system is discussed.

  11. Wind Shear May Produce Long-Lived Storms and Squall Lines on Titan

    NASA Astrophysics Data System (ADS)

    Rafkin, Scot C. R.; Barth, Erika

    2015-11-01

    The impact of CAPE and wind shear on storms in a Titan-like environment are explored through numerical simulation. Numerical modeling indicates that both large-scale shear and CAPE environment control the dynamics of the clouds. This response to the large-scale environment is analogous to the behavior of deep convective clouds on Earth. The balance between shear and CAPE, as expressed through the bulk Richardson Number (NR), is a good indicator of the response of a storm to its environment. Large NR results in short-lived single cell storms (Figure 1). As shear increases for a given CAPE, and NR decreases, the storms transition to a multicellular regime. Multicellular storms are longer-lived and are characterized by a downdraft generated cold pool that interacts with the background shear vorticity to initiate cells along the leading edge of the storm gust front (Figure 2). Very long-lived storms (>24 hours) propagating for 1000 km or more might be possible. The most intense multicellular systems simulated in this study behave similar to terrestrial squall lines, and very long-lived storms (>24 hours) propagating for 1000 km or more might be possible. Cloud outbursts and linear cloud features observed from ground and Cassini may be the result of these organized storm systems. Varying amounts of shear in the Titan environment might explain the variety of convective cloud expressions identified in Cassini orbiter and ground-based observations. The resulting distribution and magnitude of precipitation as well as surface winds associated with storms have implications on the formation of fluvial and aeolian features, including dunes, and on the exchange of methane with the surface and lakes.

  12. Airborne Wind Shear Detection and Warning Systems: First Combined Manufacturers' and Technologists' Conference

    NASA Technical Reports Server (NTRS)

    Spady, Amos A., Jr. (compiler); Bowles, Roland L. (compiler); Schlickenmaier, Herbert (compiler)

    1988-01-01

    The purpose of the meeting was to transfer significant, ongoing results gained during the first year of the joint NASA/FAA Airborne Wind Shear Program to the technical industry and to pose problems of current concern to the combined group. It also provided a forum for manufacturers to review forward-looking technology concepts and for technologists to gain an understanding of FAA certification requirements and the problems encountered by the manufacturers during the development of airborne equipment.

  13. WIND-SHEARING IN GASEOUS PROTOPLANETARY DISKS AND THE EVOLUTION OF BINARY PLANETESIMALS

    SciTech Connect

    Perets, Hagai B.; Murray-Clay, Ruth A.

    2011-05-20

    One of the first stages of planet formation is the growth of small planetesimals and their accumulation into large planetesimals and planetary embryos. This early stage occurs much before the dispersal of most of the gas from the protoplanetary disk. Due to their different aerodynamic properties, planetesimals of different sizes and shapes experience different drag forces from the gas during this time. Such differential forces produce a wind-shearing (WISH) effect between close by, different-sized planetesimals. For any two planetesimals, a WISH radius can be considered at which the differential acceleration due to the wind becomes greater than the mutual gravitational pull between the planetesimals. We find that the WISH radius could be much smaller than the gravitational shearing radius by the star (the Hill radius). In other words, during the gas-phase of the disk, WISH could play a more important role than tidal perturbations by the star. Here, we study the WISH radii for planetesimal pairs of different sizes and compare the effects of wind and gravitational shearing (drag force versus gravitational tidal force). We then discuss the role of WISH for the stability and survival of binary planetesimals. Binaries are sheared apart by the wind if they are wider than their WISH radius. WISH-stable binaries can also inspiral, and possibly coalesce, due to gas drag. Here, we calculate the WISH radius and the gas-drag-induced merger timescale, providing stability and survival criteria for gas-embedded binary planetesimals. Our results suggest that even WISH-stable binaries may merge in times shorter than the lifetime of the gaseous disk. This may constrain currently observed binary planetesimals to have formed far from the star or at a late stage after the dispersal of most of the disk gas. We note that the WISH radius may also be important for other processes such as planetesimal erosion and planetesimal encounters and collisions in a gaseous environment.

  14. Wind waves on a mudflat: The influence of fetch and depth on bed shear stresses

    NASA Astrophysics Data System (ADS)

    Mariotti, Giulio; Fagherazzi, Sergio

    2013-06-01

    Wind waves were measured in the Willapa Bay mudflats, Washington State, USA, for two months. Wave height, period, and bed shear stresses were modulated by water depth (0-3.5m), wind speed (0-20m/s), and fetch (1-5km). Good agreement was found between the measured waves and predictions of the wave spectral model SWAN using either simplified 1D flat bottom or 2D geometries. The relationship between bed shear stress and water depth shows a dependence on fetch: the decay of bed shear stress with increasing water depth is gradual for long fetch and rapid for short fetch. This difference is explained by the coupled effects of water depth, wave height and wave period. Due to the fetch-dependent bed shear stress, different morphological consequences for tidal flats of different size are predicted. In small (˜2km) and sheltered tidal flats, waves cause the largest sediment resuspension when water levels are near mean sea level. In extensive tidal flats (˜20km) or in flats exposed to waves propagating from deep water, waves also are effective in causing substrate erosion during high tides or large storm surges.

  15. Wind waves on a mudflat: The influence of fetch and depth on bed shear stresses

    NASA Astrophysics Data System (ADS)

    Mariotti, Giulio; Fagherazzi, Sergio

    2013-06-01

    Wind waves were measured in the Willapa Bay mudflats, Washington State, USA, for two months. Wave height, period, and bed shear stresses were modulated by water depth (0-3.5 m), wind speed (0-20 m/s), and fetch (1-5 km). Good agreement was found between the measured waves and predictions of the wave spectral model SWAN using either simplified 1D flat bottom or 2D geometries. The relationship between bed shear stress and water depth shows a dependence on fetch: the decay of bed shear stress with increasing water depth is gradual for long fetch and rapid for short fetch. This difference is explained by the coupled effects of water depth, wave height and wave period. Due to the fetch-dependent bed shear stress, different morphological consequences for tidal flats of different size are predicted. In small (˜2 km) and sheltered tidal flats, waves cause the largest sediment resuspension when water levels are near mean sea level. In extensive tidal flats (˜20 km) or in flats exposed to waves propagating from deep water, waves also are effective in causing substrate erosion during high tides or large storm surges.

  16. Rossby-Khantadze electromagnetic planetary waves driven by sheared zonal winds in the E-layer ionosphere

    SciTech Connect

    Futatani, S.; Horton, W.; Kahlon, L. Z.; Kaladze, T. D.

    2015-01-15

    Nonlinear simulations of electromagnetic Rossby and Khantadze planetary waves in the presence of a shearless and sheared zonal flows in the weakly ionized ionospheric E-layer are carried out. The simulations show that the nonlinear action of the vortex structures keeps the solitary character in the presence of shearless zonal winds as well as the ideal solutions of solitary vortex in the absence of zonal winds. In the presence of sheared zonal winds, the zonal flows result in breaking into separate multiple smaller pieces. A passively convected scalar field is shown to clarify the transport associated with the vortices. The work shows that the zonal shear flows provide an energy source into the vortex structure according to the shear rate of the zonal winds.

  17. An Examination of Aviation Accidents Associated with Turbulence, Wind Shear and Thunderstorm

    NASA Technical Reports Server (NTRS)

    Evans, Joni K.

    2013-01-01

    The focal point of the study reported here was the definition and examination of turbulence, wind shear and thunderstorm in relation to aviation accidents. NASA project management desired this information regarding distinct subgroups of atmospheric hazards, in order to better focus their research portfolio. A seven category expansion of Kaplan's turbulence categories was developed, which included wake turbulence, mountain wave turbulence, clear air turbulence, cloud turbulence, convective turbulence, thunderstorm without mention of turbulence, and low altitude wind shear, microburst or turbulence (with no mention of thunderstorms).More than 800 accidents from flights based in the United States during 1987-2008 were selected from a National Transportation Safety Board (NTSB) database. Accidents were selected for inclusion in this study if turbulence, thunderstorm, wind shear or microburst was considered either a cause or a factor in the accident report, and each accident was assigned to only one hazard category. This report summarizes the differences between the categories in terms of factors such as flight operations category, aircraft engine type, the accident's geographic location and time of year, degree of injury to aircraft occupants, aircraft damage, age and certification of the pilot and the phase of flight at the time of the accident.

  18. Airport Surveillance Radar (ASR-9) wind shear processor: 1991 test at Orlando, Florida

    NASA Astrophysics Data System (ADS)

    Weber, M. E.

    1992-06-01

    An operational test of a Wind Shear Processor (WSP) add-on to the Federal Aviation Administration's airport surveillance radar (ASR-9) took place at Orlando International Airport during July and August 1991. The test allowed for both quantitative assessment of the WSP's signal processing and wind shear detection algorithms and for feedback from air traffic controllers and their supervisors on the strengths and weaknesses of the system. Thunderstorm activity during the test period was intense; low-altitude wind shear impacted the runways or approach/departure corridors on 40 of the 53 test days. As in previous evaluations of the WSP in the southeastern United States, microburst detection performance was very reliable. Over 95 percent of the strong microbursts that affected the Orlando airport during the test period were detected by the system. Gust front detection during the test, while operationally useful, was not as reliable as it should have been, given the quality of gust front signatures in the base reflectivity and radial velocity data from the WSP. Subsequent development of a Machine Intelligent Gust Front Algorithm has resulted in significantly improved detection capability. Results from the operational test are being utilized in ongoing refinement of the WSP.

  19. Equatorial F region neutral winds and shears near sunset measured with chemical release techniques

    NASA Astrophysics Data System (ADS)

    Kiene, A.; Larsen, M. F.; Kudeki, E.

    2015-10-01

    The period near sunset is a dynamic and critical time for the daily development of the equatorial nighttime ionosphere and the instabilities that occur there. It is during these hours that the preconditions necessary for the later development of Equatorial Spread F (ESF) plasma instabilities occur. The neutral dynamics of the sunset ionosphere are also of critical importance to the generation of currents and electric fields; however, the behavior of the neutrals is experimentally understood primarily through very limited single-altitude measurements or measurements that provide weighted altitude means of the winds as a function of time. To date, there have been very few vertically resolved neutral wind measurements in the F region at sunset. We present two sets of sounding rocket chemical release measurements, one from a launch in the Marshall Islands on Kwajalein atoll and one from Alcantara, Brazil. Analysis of the release motions has yielded vertically resolved neutral wind profiles that show both the mean horizontal winds and the vertical shears in the winds. In both experiments, we observe significant vertical gradients in the zonal wind that are unexpected by classical assumptions about the behavior of the neutral wind at these altitudes at sunset near the geomagnetic equator.

  20. Watershed Scale Shear Stress From Tethersonde Wind Profile Measurements Under Near Neutral and Unstable Atmospheric Stability

    NASA Astrophysics Data System (ADS)

    Parlange, M. B.; Katul, G. G.

    1995-04-01

    Mean wind speed profiles were measured in the atmospheric surface layer, using a tethersonde system, above the Ojai Valley Watershed in southern California. The valley is mainly planted with mature avocado and orange trees. The surface shear stress and latent and sensible heat fluxes were measured above the trees which are up to 9 m in height. Near-neutral wind speed profile measurements allowed the determination of the watershed surface roughness (z0 = 1.4 m) and the momentum displacement height (d0 = 7.0 m). The wind speed measurements obtained under unstable atmospheric stability were analyzed using Monin-Obukhov similarity theory. New stability correction functions proposed based on theory and experiments of Kader-Yaglom as well as the now classic Businger-Dyer type functions were tested. The watershed shear stress values calculated using the surface layer wind speed profiles with the new Monin-Obukhov stability functions were found to be improved in comparison with the values obtained with the Businger-Dyer functions under strongly unstable stability conditions. The Monin-Obukhov model with the Businger-Dyer stability correction function underpredicted the momentum flux by 25% under strongly unstable stability conditions, while the new Kader-Yaglom formulation compared well on average (R2 = 0.77) with the surface eddy correlation measurements for all atmospheric stability conditions. The unstable 100-m drag coefficient was found to be u*2/V1002 = 0.0182.

  1. A spatial model of wind shear and turbulence for flight simulation. Ph.D. Thesis - Colorado State Univ.

    NASA Technical Reports Server (NTRS)

    Campbell, C. W.

    1984-01-01

    A three dimensional model which combines measurements of wind shear in the real atmosphere with three dimensional Monte Carlo simulated turbulence was developed. The wind field over the body of an aircraft can be simulated and all aerodynamic loads and moments calculated.

  2. Airborne Wind Shear Detection and Warning Systems: Fourth Combined Manufacturers' and Technologists' Conference, part 1

    NASA Technical Reports Server (NTRS)

    Vicroy, Dan D. (compiler); Bowles, Roland L. (compiler); Passman, Robert H. (compiler)

    1992-01-01

    The purpose of the meeting was to transfer significant ongoing results of the NASA/FAA joint Airborne Wind Shear Program to the technical industry and to pose problems of current concern to the combined group. It also provided a forum for manufacturers to review forward-look technology concepts and for technologists to gain an understanding of the problems encountered by the manufacturers during the development of airborne equipment and the FAA certification requirements. The present document was compiled to record the essence of the technology updates and discussions which follow each.

  3. Airborne Wind Shear Detection and Warning Systems: Third Combined Manufacturers' and Technologists' Conference, part 2

    NASA Technical Reports Server (NTRS)

    Vicroy, Dan D. (compiler); Bowles, Roland L. (compiler); Schlickenmaier, Herbert (compiler)

    1991-01-01

    The Third Combined Manufacturers' and Technologists' Conference was held in Hampton, Va., on October 16-18, 1990. The purpose of the meeting was to transfer significant on-going results of the NASA/FAA joint Airborne Wind Shear Program to the technical industry and to pose problems of current concern to the combined group. It also provided a forum for manufacturers to review forward-look technology concepts and for technologists to gain an understanding of the problems encountered by the manufacturers during the development of airborne equipment and the FAA certification requirements.

  4. Airborne Wind Shear Detection and Warning Systems. Second Combined Manufacturers' and Technologists' Conference, part 1

    NASA Technical Reports Server (NTRS)

    Spady, Amos A., Jr. (compiler); Bowles, Roland L. (compiler); Schlickenmaier, Herbert (compiler)

    1990-01-01

    The Second Combined Manufacturers' and Technologists' Conference hosted jointly by NASA Langley (LaRC) and the Federal Aviation Administration (FAA) was held in Williamsburg, Virginia, on October 18 to 20, 1988. The purpose of the meeting was to transfer significant, ongoing results gained during the second year of the joint NASA/FAA Airborne Wind Shear Program to the technical industry and to pose problems of current concern to the combined group. It also provided a forum for manufacturers to review forward-look technology concepts and for technologists to gain an understanding of the problems encountered by the manufacturers during the development of airborne equipment and the FAA certification requirements.

  5. Turbulent transport model of wind shear in thunderstorm gust fronts and warm fronts

    NASA Technical Reports Server (NTRS)

    Lewellen, W. S.; Teske, M. E.; Segur, H. C. O.

    1978-01-01

    A model of turbulent flow in the atmospheric boundary layer was used to simulate the low-level wind and turbulence profiles associated with both local thunderstorm gust fronts and synoptic-scale warm fronts. Dimensional analyses of both type fronts provided the physical scaling necessary to permit normalized simulations to represent fronts for any temperature jump. The sensitivity of the thunderstorm gust front to five different dimensionless parameters as well as a change from axisymmetric to planar geometry was examined. The sensitivity of the warm front to variations in the Rossby number was examined. Results of the simulations are discussed in terms of the conditions which lead to wind shears which are likely to be most hazardous for aircraft operations.

  6. The Structural Changes of Tropical Cyclones Upon Interaction with Vertical Wind Shear

    NASA Technical Reports Server (NTRS)

    Ritchie, Elizabeth A.

    2003-01-01

    The Fourth Convection and Moisture Experiment (CAMEX-4) provided a unique opportunity to observe the distributions and document the roles of important atmospheric factors that impact the development of the core asymmetries and core structural changes of tropical cyclones embedded in vertical wind shear. The state-of-the-art instruments flown on the NASA DC-8 and ER-2, in addition to those on the NOAA aircraft, provided a unique set of observations that documented the core structure throughout the depth of the tropical cyclone. These data have been used to conduct a combined observational and modeling study using a state-of-the-art, high- resolution mesoscale model to examine the role of the environmental vertical wind shear in producing tropical cyclone core asymmetries, and the effects on the structure and intensity of tropical cyclones.The scientific objectives of this study were to obtain in situ measurements that would allow documentation of the physical mechanisms that influence the development of the asymmetric convection and its effect on the core structure of the tropical cyclone.

  7. Assessment of Wind Shear and Wind Energy Potential in the Baltic Sea Region of Latvia

    NASA Astrophysics Data System (ADS)

    Bezrukovs, V.; Bezrukovs, Vl.; Zacepins, A.; Komashilovs, V.

    2015-04-01

    The paper is devoted to the investigation into the wind energy potential based on long-term observations of the wind speed and energy density fluctuations at heights from 10 to 160 m on the Baltic Sea coast of Latvia. During the observations (2004 - 2013), the wind speed and direction values were measured, and the statistical database was accumulated using a LOGGER 9200 Symphonie measuring systems mounted on 60 m masts - one on the western coast and another on the north-east of Latvia. From June 2011 to May 2012, these measurements were complemented with the data for the heights from 40 to 160 m obtained by means of a ZephIR lidar and with the metrological data provided by "Latvian Environment, Geology and Meteorology Centre" for the same period. The graphs of seasonal fluctuations in the wind speed were obtained for the heights up to 160 m by measurements over the period of 2007 - 2013. The results of the research on the wind speed distribution up to 200 m are promising for evaluation of the wind energy potential of Latvia and will be helpful in assessment of prospective sites for construction of WPPs. Zin?tniskais raksts ir velt?ts p?t?jumam par v?ja ener?ijas potenci?lu Latvijas teritorij?, Baltijas j?ras piekrast?, balstoties uz ilgtermi?a v?ja ?truma un v?ja ener?ijas bl?vuma sv?rst?bu nov?rojumiem no 10 l?dz 160 metriem augstum?. V?ja ?truma un v?ja virziena m?r?jumu dati tika ieg?ti un apkopoti statistiskaj? datub?z? laika period? no 2004 l?dz 2013. gadam, izmantojot m?r?šanas sist?mu LOGGER 9200 Symphonie, kas bija ier?kot? uz 60 metru augsta masta - viena rietumu piekrast? un otra Latvijas zieme?u-austrumos. No 2011. gada j?nija l?dz 2012. gada maijam m?r?jumu datub?ze tika papildin?ta ar datiem, kas tika ieg?ti ar lidaruZephIR augstumos no 40 l?dz 160 metriem, un datiem no "Latvijas Vides, ?eolo?ijas un meteorolo?ijas centra" tam pašam laika periodam. Analiz?jot m?r?jumus 2007. g.-2013. g., grafiki ar v?ja sezon?l?m ?truma sv?rst?b?m tika ieg?ti l?dz 160 metru augstumam. P?t?juma rezult?ti par v?ja ?truma sadal?jumu l?dz 200 metriem, ?auj nov?rt?t v?ja ener?ijas potenci?lu Latvij?, un tiem ir j?pal?dz noteikt perspekt?v?k?s vietas v?ja turb?nu izvietošanai.

  8. A shear sensitive monomer-polymer liquid crystal system for wind tunnel applications

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Singh, Jag J.; Eftekhari, Abe

    1992-01-01

    Characteristics of a liquid crystal system, comprised of a shear-sensitive cholesteric-monomer liquid crystal thin-film coated on a liquid-crystal polymer substrate, are described. The system provides stable Grandjean texture, a desirable feature for shear-stress measurements using selective reflection from the monomer liquid-crystal helix structure. Impingement of gas or air flow on the monomer liquid-crystal free surface changes the wavelength of the selective reflection for an incident white light from red toward blue with increase in the rate of gas flow. The contrast of the selectively reflected light improves considerably by providing a thin black coating of about 5 microns at the monomer-polymer interface. The coating thickness is such that the steric interactions are still sufficiently strong to maintain Grandjean texture. For a small angle of incidence of a monochromatic light, the measurement of the reflected light intensity normal to the monomer-polymer liquid-crystal interface enables the determination of the wavelength for selective reflection as a function of the gas-flow differential pressure applied in the plane of the interface. The variation of the wavelength with the pressure is linear with a slope of about 2 nm/mmHg. Furthermore, the shear-stress effects are reversible unlike for monomer liquid crystal-metal systems used for flow visualization on wind-tunnel model surfaces. The present system offers a suitable method for direct on-line measurement of shear stress field from measurements of the wavelength for selective reflection for an incident white light.

  9. Microburst wind structure and evaluation of Doppler radar for airport wind shear detection

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Roberts, R. D.; Kessinger, C.; Mccarthy, J.

    1984-01-01

    The horizontal and vertical structure of airflow within microbursts has been determined using Doppler weather radar data from the Joint Airport Weather Studies (JAWS) Project. It is shown that the downdraft typically associated with microbursts is about 1 km wide and begins to spread horizontally at a height below 1 km. The median time from initial divergence at the surface to maximum differential wind velocity across the microburst is five minutes. The height of maximum differential velocity is about 75 m, and the median velocity differential is 22 m/s over an average distance of 3.1 km. The outflow of the air is asymmetric, averaging twice as strong along the maximum axis compared to the mininum axis. Some technical requirements for a radar system to detect microbursts and to provide aircraft with early warnings of the onset of windshear are identified.

  10. Airborne Wind Shear Detection and Warning Systems. Second Combined Manufacturers' and Technologists' Conference, part 2

    NASA Technical Reports Server (NTRS)

    Spady, Amos A., Jr. (compiler); Bowles, Roland L. (compiler); Schlickenmaier, Herbert (compiler)

    1990-01-01

    The Second Combined Manufacturers' and Technologists' Conference was hosted jointly by NASA Langley (LaRC) and the Federal Aviation Administration (FAA) in Williamsburg, Virginia, on October 18 to 20, 1988. The meeting was co-chaired by Dr. Roland Bowles of LaRC and Herbrt Schlickenmaier of the FAA. The purpose of the meeting was to transfer significant, ongoing results gained during the second year of the joint NASA/FAA Airborne Wind Shear Program to the technical industry and to pose problems of current concern to the combined group. It also provided a forum for manufacturers to review forward-look technology concepts and for technologists to gain an understanding of the problems encountered by the manufacturers during the development of airborne equipment and the FAA certification requirements.

  11. 1983 lightning, turbulence, wind shear, and Doppler radar studies at the National Severe Storms Laboratory

    NASA Technical Reports Server (NTRS)

    Lee, J. T.

    1984-01-01

    As part of continuing research on aviation related weather hazards, numerous experiments were incorporated into the 1983 Spring Observation Program. This year's program was an abbreviated one because of commitments made to the development of the Next Generation Radar (NEXRAD) project. The National Oceanic and Atmospheric Administration's (NOAA) P-3 Orion and the National Aeronautics and Space Administration's (NASA) RB-57B and U-2 were the main aircraft involved in the studies of lightning, wind shear, turbulence, and storm structure. A total of 14 flights were made by these aircraft during the period of May 16 through June 5, 1983. Aircraft instrumentation experiments are described, and resultant data sets available for research are detailed. Aircraft instrumentation and Doppler radar characteristics are detailed.

  12. Airborne Wind Shear Detection and Warning Systems. Fourth Combined Manufacturers' and Technologists' Conference, part 2

    NASA Technical Reports Server (NTRS)

    Vicroy, Dan D. (compiler); Bowles, Roland L. (compiler); Passman, Robert H. (compiler)

    1992-01-01

    The Fourth Combined Manufacturers' and Technologists' Conference was hosted jointly by NASA Langley Research Center (LaRC) and the Federal Aviation Administration (FAA) in Williamsburg, Virginia, on April 14-16, 1992. The meeting was co-chaired by Dr. Roland Bowles of LaRC and Bob Passman of the FAA. The purpose of the meeting was to transfer significant ongoing results of the NASA/FAA Joint Airborne Wind Shear Program to the technical industry and to pose problems of current concern to the combined group. It also provided a forum for manufacturers to review forward-look technology concepts and for technologists to gain an understanding of the problems encountered by the manufacturers during the development of airborne equipment and the FAA certification requirements. The present document has been compiled to record the essence of the technology updates and discussions which follow each.

  13. Effects of turbulent eddies and Langmuir circulations on scalar transfer in a sheared wind-driven liquid flow

    NASA Astrophysics Data System (ADS)

    Takagaki, Naohisa; Kurose, Ryoichi; Tsujimoto, Yuta; Komori, Satoru; Takahashi, Keiko

    2015-01-01

    The effects of turbulent eddies and Langmuir circulations in liquid flow on scalar transfer across a sheared wind-driven gas-liquid interface are investigated by means of a direct numerical simulation of a gas-liquid two-phase turbulent flow with a wind-driven nonbreaking wavy interface. The wind-driven wavy gas-liquid interface is captured using an arbitrary Lagrangian-Eulerian method with boundary-fitted coordinates on moving grids. The results show that Langmuir circulations are generated on the liquid side below the sheared wind-driven gas-liquid interface. The marker particles on the gas-liquid interface, the turbulent eddies in the form of streamwise vortices on the liquid side (i.e., the typical horseshoe vortices associated with bursting motions), and the low scalar flux lines on the gas-liquid interface induced by the turbulent eddies on the liquid side tend to locally concentrate in the regions along the downward flows caused by the Langmuir circulations. It is suggested that the turbulent eddies on the liquid side mainly control the scalar transfer across the sheared wind-driven gas-liquid interface, and the effect of the Langmuir circulations is relatively small.

  14. Dynamic impact of the vertical shear of gradient wind on the tropical cyclone boundary layer wind field

    NASA Astrophysics Data System (ADS)

    Cai, Ninghao; Xu, Xin; Song, Lili; Bai, Lina; Ming, Jie; Wang, Yuan

    2014-02-01

    This work studies the impact of the vertical shear of gradient wind (VSGW) in the free atmosphere on the tropical cyclone boundary layer (TCBL). A new TCBL model is established, which relies on fiveforce balance including the pressure gradient force, Coriolis force, centrifugal force, turbulent friction, and inertial deviation force. This model is then employed to idealize tropical cyclones (TCs) produced by DeMaria's model, under different VSGW conditions (non-VSGW, positive VSGW, negative VSGW, and VSGW increase/decrease along the radial direction). The results show that the free-atmosphere VSGW is particularly important to the intensity of TC. For negative VSGW, the total horizontal velocity in the TCBL is somewhat suppressed. However, with the maximum radial inflow displaced upward and outward, the radial velocity notably intensifies. Consequently, the convergence is enhanced throughout the TCBL, giving rise to a stronger vertical pumping at the TCBL top. In contrast, for positive VSGW, the radial inflow is significantly suppressed, even with divergent outflow in the middle-upper TCBL. For varying VSGW along the radial direction, the results indicate that the sign and value of VSGW is more important than its radial distribution, and the negative VSGW induces stronger convergence and Ekman pumping in the TCBL, which favors the formation and intensification of TC.

  15. Numerical simulation to determine the effects of incident wind shear and turbulence level on the flow around a building

    SciTech Connect

    Zhang, Y.Q.; Huber, A.H.; Arya, S.P.S.; Snyder, W.H.

    1992-01-01

    The effects of incident shear and turbulence on flow around a cubical building are being investigated by a turbulent kinetic energy/dissipation model (TEMPEST). The numerical simulations demonstrate significant effects due to the differences in the incident flow. The addition of upstream turbulence and shear results in a reduced size of the cavity directly behind the building. The accuracy of numerical simulations is verified by comparing the predicted mean flow fields with the available wind-tunnel measurements of Castro and Robins (1977). Comparing the authors' results with experimental data, the authors show that the TEMPEST model can reasonably simulate the mean flow.

  16. Importance of thermal effects and sea surface roughness for wind resource and wind shear at offshore sites

    E-print Network

    Heinemann, Detlev

    of offshore wind power utilisation depends on the favourable wind conditions offshore as compared to sites for this flow. It's applicability for wind power prediction at offshore sites is investigated using data from at offshore sites Bernhard Lange*, Søren Larsen# , Jørgen Højstrup# , Rebecca Barthelmie# *ForWind - Centre

  17. The ATC evaluation of the prototype Airport Surveillance Radar Wind Shear Processor (ASR-WSP) at Orlando International Airport

    NASA Astrophysics Data System (ADS)

    Martinez, Radame

    1993-03-01

    The Airport Surveillance Radar Wind Shear Processor (ASR-WSP), also known as Airport Surveillance Radar-9 (ASR-9) modification for low altitude wind shear detection, is a production ASR-9 with an expanded weather channel for added processing capabilities. The primary mission of the ASR-WSP is to enhance the safety of air travel through the timely detection and reporting of hazardous wind shear in and near the terminal approach and departure zones of the airport. It will also improve the management of air traffic (AT) in the terminal area through the forecast of precipitation, and ultimately the detection of other hazardous weather phenomena. The ASR-WSP may be used as a stand-alone system at airports without a Terminal Doppler Weather Radar (TDWR) or Enhanced-Low Level Wind Shear Alert System (E-LLWAS), or in an integrated mode with either or both the TDWR and E-LLWAS. An operational evaluation of a prototype ASR-WSP, developed by Massachusetts Institute of Technology Lincoln Laboratories (MIT/LL), was conducted at the Orlando International Airport (MCO) in Orlando, Florida, during the period 29 Jun. to 31 Aug. 1992. The objective of the evaluation was to obtain Federal Aviation Administration (FAA) air traffic controller reaction to the prototype ASR-WSP weather data and display equipment. The following are highlights of the evaluation: (1) the ASW-WSP is very useful when making runway configuration changes; (2) the ASR-WSP is not perceived to be as accurate as the prototype TDWR; (3) the gust front prediction feature is not reliable; and (4) the information provided on both the RDT and the GSD is very useful.

  18. Radar-based severe storm climatology for Austrian complex orography related to vertical wind shear and atmospheric instability

    NASA Astrophysics Data System (ADS)

    Kaltenboeck, Rudolf; Steinheimer, Martin

    2015-05-01

    The paper examines the temporal and spatial distribution of intense convective cores as a function of CAPE and vertical wind shear. C band weather radar data are exploited over the complex orography of Austria. Further ERA-Interim data are used for the classification of synoptic flow and instability. A 5-year period of convective seasons shows the presence of severe thunderstorms over Austria. The spatial distribution of high radar reflectivity differs from the radar derived precipitation field due to the contribution of stratiform rain, weak convective events, and radar related measurement errors. Westerly and southerly flow classes are associated with more widespread thunderstorm development. One of the key results is that the strong deep-layer shear environment leads to organized, line oriented pattern over wide areas of Austria, except the observed minima over the Alpine crest. These preferred areas for severe storm occurrence can be well used for nowcasting. Especially during low CAPE conditions the magnitude of deep-layer shear is very important for the spatial arrangement, maximum size of the convective system, and time of occurrence. For the eastern part of Austria and the Alps, high deep-layer shear tends to produce larger cell cores in terms of high radar reflectivity. For the Alps during low CAPE conditions and for the eastern part of Austria for all CAPE classifications, the strong deep-layer shear increases the frequency of severe storms and shifts the peak of occurrence from afternoon toward the evening.

  19. Automatic detection of low altitude wind shear due to gust fronts in the terminal Doppler weather radar operational demonstration

    NASA Technical Reports Server (NTRS)

    Klingle-Wilson, Diana

    1990-01-01

    A gust front is the leading edge of the cold air outflow from a thunderstorm. Wind shears and turbulence along the gust front may produce potentially hazardous conditions for an aircraft on takeoff or landing such that runway operations are significantly impacted. The Federal Aviation Administration (FAA) has therefore determined that the detection of gust fronts in the terminal environment be an integral part of the Terminal Doppler Weather Radar (TDWR) system. Detection of these shears by the Gust Front Algorithm permits the generation of warnings that can be issued to pilots on approach and departure. In addition to the detection capability, the algorithm provides an estimate of the wind speed and direction following the gust front (termed wind shift) and the forecasted location of the gust front up to 20 minutes before it impacts terminal operations. This has shown utility as a runway management tool, alerting runway supervisors to approaching wind shifts and the possible need to change runway configurations. The formation and characteristics of gust fronts and their signatures in Doppler radar data are discussed. A brief description of the algorithm and its products for use by Air Traffic Control (ATC), along with an assessment of the algorithm's performance during the 1988 Operational Test and Evaluation, is presented.

  20. A two-dimensional study of the maximum power that can be obtained from a wind turbine in a wind shear layer

    SciTech Connect

    Johansson, B.C.A.

    1981-04-01

    In 1926 Albert Betz derived a one-dimensional stream tube theory for the maximum power that can be obtained from a wind turbine in a uniform flow. However, for modern large wind turbines there is a considerable velocity gradient in the approaching flow, since the wind flow field above the ground normally is a shear layer with a velocity profile reminding of that of a boundary layer of a wing or a flat plate. The present study extends Betz' theory to a two-dimensional case, where the undisturbed velocity field is given and allowed to vary arbitrarily vertically, and the location of the wind turbine is given. The maximum power is calculated by the method of calculus of variations. It is found that for common wind velocity profiles the maximum power is only slightly larger than the power, which is obtained by a constant relative wind speed retardation, equal to Betz' retardation, while for a linear velocity profile there is a considerable difference.

  1. Role of upper-level wind shear on the structure and maintenance of derecho-producing convective systems

    NASA Astrophysics Data System (ADS)

    Coniglio, Michael Charles

    Common large-scale environments associated with the development of derecho-producing convective systems from a large number of events are identified using statistical clustering of the 500-mb geopotential heights as guidance. The majority of the events (72%) fall into three main patterns that include a well-defined upstream trough (40%), a ridge (20%), and a zonal, low-amplitude flow (12%), which is defined as an additional warm-season pattern that is not identified in past studies of derecho environments. Through an analysis of proximity soundings, discrepancies are found in both low-level and deep-tropospheric shear parameters between observations and the shear profiles considered favorable for strong, long-lived convective systems in idealized simulations. To explore the role of upper-level shear in derecho environments, a set of two-dimensional simulations of density currents within a dry, neutrally stable environment are used to examine the ability of a cold pool to lift environmental air within a vertically sheared flow. The results confirm that the addition of upper-level shear to a wind profile with weak to moderate low-level shear increases the vertical displacement of low-level parcels despite a decrease in the vertical velocity along the cold pool interface, as suggested by previous studies. Parcels that are elevated above the surface (1-2 km) overturn and are responsible for the deep lifting in the deep-shear environments. This deep overturning caused by the upper-level shear helps to maintain the tilt of the convective systems in more complex two-dimensional and three dimensional simulations. The overturning also is shown to greatly increase the size of the convective systems in the three-dimensional simulations by facilitating the initiation and maintenance of convective cells along the cold pool. When combined with estimates of the cold pool motion and the storm-relative hodograph, these results may best be used for the prediction of the demise of strong, linear mesoscale convective systems (MCSs) and may provide a conceptual model for the persistence of strong MCSs above a surface nocturnal inversion in situations that are not forced by a low-level jet.

  2. Further examination of the thermodynamic modification of the inflow layer of tropical cyclones by vertical wind shear

    NASA Astrophysics Data System (ADS)

    Riemer, M.; Montgomery, M. T.; Nicholls, M. E.

    2013-01-01

    Recent work has developed a new framework for the impact of vertical wind shear on the intensity evolution of tropical cyclones. A focus of this framework is on the frustration of the tropical cyclone's power machine by shear-induced, persistent downdrafts that flush relatively cool and dry (lower equivalent potential temperature, ?e) air into the storm's inflow layer. These previous results have been based on idealised numerical experiments for which we have deliberately chosen a simple set of physical parameterisations. Before efforts are undertaken to test the proposed framework with real atmospheric data, we assess here the robustness of our previous results in a more realistic and representative experimental setup by surveying and diagnosing five additional numerical experiments. The modifications of the experimental setup comprise the values of the exchange coefficients of surface heat and momentum fluxes, the inclusion of experiments with ice microphysics, and the consideration of weaker, but still mature tropical cyclones. In all experiments, the depression of the inflow layer ?e values is significant and all tropical cyclones exhibit the same general structural changes when interacting with the imposed vertical wind shear. Tropical cyclones in which strong downdrafts occur more frequently exhibit a more pronounced depression of inflow layer ?e outside of the eyewall in our experiments. The magnitude of the ?e depression underneath the eyewall early after shear is imposed in our experiments correlates well with the magnitude of the ensuing weakening of the respective tropical cyclone. Based on the evidence presented, it is concluded that the newly proposed framework is a robust description of intensity modification in our suite of experiments.

  3. Further examination of the thermodynamic modification of the inflow layer of tropical cyclones by vertical wind shear

    NASA Astrophysics Data System (ADS)

    Riemer, M.; Montgomery, M. T.; Nicholls, M. E.

    2012-03-01

    Recent work has developed a new framework for the impact of vertical wind shear on the intensity evolution of tropical cyclones. A focus of this framework is on the frustration of the tropical cyclone's power machine by shear-induced, persistent downdrafts that flush relatively cool and dry (lower equivalent potential temperature, ?e) air into the storm's inflow layer. These previous results have been based on idealised numerical experiments for which we have deliberately chosen a simple set of physical parameterisations. Before efforts are undertaken to test the proposed framework with real atmospheric data, we here survey and diagnose five additional numerical experiments with some modifications of the experimental setup to assess the robustness of our previous results. The modifications comprise the values of the exchange coefficients of surface heat and momentum fluxes, the inclusion of experiments with ice microphysics, and the consideration of weaker, but still mature tropical cyclones. In all experiments, the depression of the inflow layer ?e values is significant and all tropical cyclones exhibit the same general structural changes when interacting with the imposed vertical wind shear. Tropical cyclones with a higher downdraft activity exhibit a more pronounced depression of inflow layer ?e outside of the eyewall in our experiments. The magnitude of the ?e depression underneath the eyewall early after shear is imposed in our experiments correlates well with the magnitude of the ensuing weakening of the respective tropical cyclone. Based on the evidence presented, it is concluded that the newly proposed framework is a robust description of intensity modification in our suite of experiments.

  4. Competing mechanisms of plasma transport in inhomogeneous configurations with velocity shear: the solar-wind interaction with earth's magnetosphere.

    PubMed

    Faganello, M; Califano, F; Pegoraro, F

    2008-01-11

    Two-dimensional simulations of the Kelvin-Helmholtz instability in an inhomogeneous compressible plasma with a density gradient show that, in a transverse magnetic field configuration, the vortex pairing process and the Rayleigh-Taylor secondary instability compete during the nonlinear evolution of the vortices. Two different regimes exist depending on the value of the density jump across the velocity shear layer. These regimes have different physical signatures that can be crucial for the interpretation of satellite data of the interaction of the solar wind with the magnetospheric plasma. PMID:18232777

  5. Competing Mechanisms of Plasma Transport in Inhomogeneous Configurations with Velocity Shear: The Solar-Wind Interaction with Earth's Magnetosphere

    SciTech Connect

    Faganello, M.; Califano, F.; Pegoraro, F.

    2008-01-11

    Two-dimensional simulations of the Kelvin-Helmholtz instability in an inhomogeneous compressible plasma with a density gradient show that, in a transverse magnetic field configuration, the vortex pairing process and the Rayleigh-Taylor secondary instability compete during the nonlinear evolution of the vortices. Two different regimes exist depending on the value of the density jump across the velocity shear layer. These regimes have different physical signatures that can be crucial for the interpretation of satellite data of the interaction of the solar wind with the magnetospheric plasma.

  6. Solar-wind turbulence and shear: a superposed-epoch analysis of corotating interaction regions at 1 AU

    SciTech Connect

    Borovsky, Joseph E; Denton, Michael H

    2009-01-01

    A superposed-epoch analysis of ACE and OMNI2 measurements is performed on 27 corotating interaction regions (CIRs) in 2003-2008, with the zero epoch taken to be the stream interface as determined by the maximum of the plasma vorticity. The structure of CIRs is investigated. When the flow measurements are rotated into the local-Parker-spiral coordinate system the shear is seen to be abrupt and intense, with vorticities on the order of 10{sup -5}-10{sup -4} sec{sup -1}. Converging flows perpendicular to the stream interface are seen in the local-Parker-spiral coordinate system and about half of the CIRs show a layer of divergent rebound flow away from the stream interface. Arguments indicate that any spreading of turbulence away from the region where it is produced is limited to about 10{sup 6} km, which is very small compared with the thickness of a CrR. Analysis of the turbulence across the CrRs is performed. When possible, the effects of discontinuities are removed from the data. Fluctuation amplitudes, the Alfvenicity, and the level of Alfvenic correlations all vary smoothly across the CrR. The Alfven ratio exhibits a decrease at the shear zone of the stream interface. Fourier analysis of 4.5-hr subintervals of ACE data is performed and the results are superposed averaged as an ensemble of realizations. The spectral slopes of the velocity, magnetic-field, and total-energy fluctuations vary smoothly across the CIR. The total-energy spectral slope is {approx} 3/2 in the slow and fast wind and in the CrRs. Analysis of the Elsasser inward-outward fluctuations shows a smooth transition across the CrR from an inward-outward balance in the slow wind to an outward dominance in the fast wind. A number of signatures of turbulence driving at the shear zone are sought (entropy change, turbulence amplitude, Alfvenicity, Alfven ratio, spectral slopes, in-out nature): none show evidence of driving of turbulence by shear.

  7. A model of wind shear and turbulence in the surface boundary layer

    NASA Technical Reports Server (NTRS)

    Luers, J. K.

    1973-01-01

    A model of wind and turbulence has been described for the surface boundary layer. The wind structure in the surface layer is considered to be a function of the surface parameters, stability, and height. The surface parameters considered are: (1) the surface roughness length; (2) the surface friction velocity; and (3) the zero plane displacement height. The stability parameter, Z/L, where L is the Monin-Obukov stability length, describes the thermal effect on the wind profile. The logarithmic wind profile is used to describe the mean wind field in the neutral boundary layer, and a logarithmic profile with a stability defect is used to describe the stable and unstable atmospheric conditions. For the very stable conditions, the logarithmic wind law does not hold. Under this condition, the layers of the atmosphere become disconnected and large scale frontal motions are the predominate factor in defining the wind profile. Figures are presented which represent some typical wind profiles in the very stable condition.

  8. Simulations of neutral wind shear effect on the equatorial ionosphere irregularities

    NASA Astrophysics Data System (ADS)

    Kim, J.; Chagelishvili, G.; Horton, W.

    2005-12-01

    We present numerical calculations of the large-scale electron density driven by the gradient drift instability in the daytime equatorial electrojet. Under two-fluid theory the linear analysis for kilometer scale waves lead to the result that all the perturbations are transformed to small scales through linear convection by shear and then damped by diffusion. The inclusion of the nonlinearity enables inverse energy cascade to provide energy to long scale. The feedback between velocity shear and nonlinearity keeps waves growing and leads to the turbulence. In strongly turbulent regime, the nonlinear states are saturated [1]. Since the convective nonlinearities are isotropic while the interactions of velocity shear with waves are anisotropic, the feedback do not necessarily enable waves to grow. The growth of waves are highly variable on k-space configuration [2]. Our simulations show that the directional relationship between vorticity of irregularities and shear are one of key factors. Thus during the transient period, the irregularities show the anisotropy of the vorticity power spectrum. We report the evolution of the power spectrum of the vorticity and density of irregularties and its anistropic nature as observed. The work was supported in part by the Department of NSF Grant ATM-0229863 and ISTC Grant G-553. C. Ronchi, R.N. Sudan, and D.T. Farley. Numerical simulations of large-scale plasma turbulece in teh day time equatorial electrojet. J. Geophys. Res., 96:21263--21279, 1991. G.D. Chagelishvili, R.G. Chanishvili, T.S. Hristov, and J.G. Lominadze. A turbulence model in unbounded smooth shear flows : The weak turbulence approach. JETP, 94(2):434--445, 2002.

  9. Environmental control of deep convective clouds on Titan: The combined effect of CAPE and wind shear on storm dynamics, morphology, and lifetime

    NASA Astrophysics Data System (ADS)

    Rafkin, Scot C. R.; Barth, E. L.

    2015-04-01

    Titan has deep convective clouds driven by the release of latent from methane condensation. As on Earth, the presence of convective available potential energy (CAPE), which quantifies the amount of energy available through condensation, is required for storms to develop. While CAPE is a requirement for storms, the dynamics, morphology, and longevity of storms on Earth is controlled by both CAPE and wind shear, often expressed as a ratio in the form of the bulk Richardson Number. The impact of CAPE and wind shear on storms in a Titan-like environment are explored through numerical simulation. Model results indicate that Titan storms should respond to changes in the Richardson Number in a manner similar to storms on Earth. Very long-lived storms (>24 h) propagating for 1000 km or more might be possible on Titan when CAPE and wind shear are properly balanced. Some of the simulated storms exhibit dynamics similar to squall lines. Varying amounts of shear in the Titan environment might explain the variety of convective cloud expressions—varying from short-lived single cell storms to longer-lived linear features and large cloud bursts—identified in Cassini orbiter and ground-based observations. The varying amounts and spatial distribution of precipitation, as well as surface winds associated with storms, should have implications on the formation of fluvial and aeolian features and on the exchange of methane with the surface and lakes.

  10. Simulation comparison of a decoupled longitudinal control system and a velocity vector control wheel steering system during landings in wind shear

    NASA Technical Reports Server (NTRS)

    Kimball, G., Jr.

    1980-01-01

    A simulator comparison of the velocity vector control wheel steering (VCWS) system and a decoupled longitudinal control system is presented. The piloting task was to use the electronic attitude direction indicator (EADI) to capture and maintain a 3 degree glide slope in the presence of wind shear and to complete the landing using the perspective runway included on the EADI. The decoupled control system used constant prefilter and feedback gains to provide steady state decoupling of flight path angle, pitch angle, and forward velocity. The decoupled control system improved the pilots' ability to control airspeed and flight path angle during the final stages of an approach made in severe wind shear. The system also improved their ability to complete safe landings. The pilots preferred the decoupled control system in severe winds and, on a pilot rating scale, rated the approach and landing task with the decoupled control system as much as 3 to 4 increments better than use of the VCWS system.

  11. Fixed-base simulation study of decoupled longitudinal controls during approach and landing of a medium jet transport in the presence of wind shear

    NASA Technical Reports Server (NTRS)

    Miller, G. K., Jr.

    1979-01-01

    The use of decoupled longitudinal controls during the approach and landing of a typical twin-engine jet transport in the presence of wind shear was studied. The simulation included use of a localizer and flight director to capture and maintain a 3 deg glide slope. The pilot then completed the landing by using visual cues provided below an altitude of 200 m by closed-circuit television and a terrain model. The decoupled controls used constant prefilter and feedback gains to provide steady state decoupling of flight path angle, pitch angle, and forward velocity. The use of the decoupled control system improved pilot performance during the approach and at touchdown in the presence of wind shears. The pilots preferred the decoupled controls and rated the task 1 to 3 increments better on a pilot rating scale, depending on wind conditions, than was the case when conventional controls were used.

  12. VELOCITY-SHEAR-INDUCED MODE COUPLING IN THE SOLAR ATMOSPHERE AND SOLAR WIND: IMPLICATIONS FOR PLASMA HEATING AND MHD TURBULENCE

    SciTech Connect

    Hollweg, Joseph V.; Chandran, Benjamin D. G.; Kaghashvili, Edisher Kh. E-mail: ekaghash@aer.com

    2013-06-01

    We analytically consider how velocity shear in the corona and solar wind can cause an initial Alfven wave to drive up other propagating signals. The process is similar to the familiar coupling into other modes induced by non-WKB refraction in an inhomogeneous plasma, except here the refraction is a consequence of velocity shear. We limit our discussion to a low-beta plasma, and ignore couplings into signals resembling the slow mode. If the initial Alfven wave is propagating nearly parallel to the background magnetic field, then the induced signals are mainly a forward-going (i.e., propagating in the same sense as the original Alfven wave) fast mode, and a driven signal propagating like a forward-going Alfven wave but polarized like the fast mode; both signals are compressive and subject to damping by the Landau resonance. For an initial Alfven wave propagating obliquely with respect to the magnetic field, the induced signals are mainly forward- and backward-going fast modes, and a driven signal propagating like a forward-going Alfven wave but polarized like the fast mode; these signals are all compressive and subject to damping by the Landau resonance. A backward-going Alfven wave, thought to be important in the development of MHD turbulence, is also produced, but it is very weak. However, we suggest that for oblique propagation of the initial Alfven wave the induced fast-polarized signal propagating like a forward-going Alfven wave may interact coherently with the initial Alfven wave and distort it at a strong-turbulence-like rate.

  13. The development of convective instability, wind shear, and vertical motion in relation to convection activity and synoptic systems in AVE 4

    NASA Technical Reports Server (NTRS)

    Davis, J. G.; Scoggins, J. R.

    1981-01-01

    Data from the Fourth Atmospheric Variability Experiment were used to investigate conditions/factors responsible for the development (local time rate-of-change) of convective instability, wind shear, and vertical motion in areas with varying degrees of convective activity. AVE IV sounding data were taken at 3 or 6 h intervals during a 36 h period on 24-25 April 1975 over approximately the eastern half of the United States. An error analysis was performed for each variable studied.

  14. Motion and interaction of decaying trailing vortices in spanwise shear wind

    NASA Technical Reports Server (NTRS)

    Liu, C. H.; Lu, T.

    1986-01-01

    A simulation is presented of the drift of trailing vortices in a cross-wind near the ground by an unsteady, two-dimensional, rotational flow field with a concentration of large vorticity in vortical spots (having a finite but small effective size and finite total strength). The problem is analyzed by a combination of the method of matched asymptotic analyses for the decay of the vortical spots and the Euler solution for the unsteady rotational flow. Using the method of averaging, a special numerical method is developed in which the grid size and time step depend only on the length and velocity scales of the background flow and are independent of the effective core size of a vortical spot. The core size can be much smaller than the grid size, whereas the peak velocity in the core is inversely propertional to the spot size. Numerical results are presented to demonstrate the strong interaction between the trajectories of the vortical spots and the change of the vorticity distribution in the background flow field.

  15. Simulator evaluation of the effects of reduced spoiler and thrust authority on a decoupled longitudinal control system during landings in wind shear

    NASA Technical Reports Server (NTRS)

    Miller, G. K., Jr.

    1981-01-01

    The effect of reduced control authority, both in symmetric spoiler travel and thrust level, on the effectiveness of a decoupled longitudinal control system was examined during the approach and landing of the NASA terminal configured vehicle (TCV) aft flight deck simulator in the presence of wind shear. The evaluation was conducted in a fixed-base simulator that represented the TCV aft cockpit. There were no statistically significant effects of reduced spoiler and thrust authority on pilot performance during approach and landing. Increased wind severity degraded approach and landing performance by an amount that was often significant. However, every attempted landing was completed safely regardless of the wind severity. There were statistically significant differences in performance between subjects, but the differences were generally restricted to the control wheel and control-column activity during the approach.

  16. NUMERICAL SIMULATION TO DETERMINE THE EFFECTS OF INCIDENT WIND SHEAR AND TURBULENCE LEVEL ON THE FLOW AROUND A BUILDING

    EPA Science Inventory

    The effects of incident shear and turbulence on flow around a cubical building are being investigated by a turbulent kinetic energy dissipation (k-e) model (TEMPEST). he numerical simulations demonstrate significant effects due to the differences in the incident flow. he addition...

  17. Use of Dual-Polarization Radar Variables to Assess Low-Level Wind Shear in Severe Thunderstorm Near-storm Environments in the Tennessee Valley

    NASA Technical Reports Server (NTRS)

    Crowe, Christina C.; Schultz, Christopher J.; Kumjian, Matthew; Carey, Lawerence D.; Petersen, Walter A.

    2011-01-01

    The upgrade of the National Weather Service (NWS) network of S ]band dual-polarization radars is currently underway, and the incorporation of polarimetric information into the real ]time forecasting process will enhance the forecaster fs ability to assess thunderstorms and their near ]storm environments. Recent research has suggested that the combination of polarimetric variables differential reflectivity (ZDR) and specific differential phase (KDP) can be useful in the assessment of low level wind shear within a thunderstorm. In an environment with strong low ]level veering of the wind, ZDR values will be largest along the right inflow edge of the thunderstorm near a large gradient in horizontal reflectivity (indicative of large raindrops falling with a relative lack of smaller drops), and take the shape of an arc. Meanwhile, KDP values, which are proportional to liquid water content and indicative of a large number of smaller drops, are maximized deeper into the forward flank precipitation shield than the ZDR arc as the smaller drops are being advected further from the updraft core by the low level winds than the larger raindrops. Using findings from previous work, three severe weather events that occurred in North Alabama were examined in order to assess the utility of these signatures in determining the potential for tornadic activity. The first case is from October 26, 2010, where a large number of storms indicated tornadic potential from a standard reflectivity and velocity analysis but very few storms actually produced tornadoes. The second event is from February 28, 2011, where tornadic storms were present early on in the event, but as the day progressed, the tornado threat transitioned to a high wind threat. The third case is from April 27, 2011, where multiple rounds of tornadic storms ransacked the Tennessee Valley. This event provides a dataset including multiple modes of tornadic development, including QLCS and supercell structures. The overarching goal of examining these three events is to compare dual ]polarization features from this larger dataset to previous work and to determine if these signatures can be a useful indication of the potential for tornadic activity associated with the amount of low ]level wind shear in the near ]storm environment.

  18. Thermal Wind The thermal wind is defined as the vector difference between the geostrophic winds at

    E-print Network

    Hennon, Christopher C.

    ATMS 310 Thermal Wind The thermal wind is defined as the vector difference between the geostrophic winds at two levels. It is not really a wind at all, just a measure of the shear of the geostrophic wind. But there are good reasons for considering the geostrophic wind; mainly, it provides a convenient way of connecting

  19. Inviscid Interactions Between Wake Vortices and Shear Layers

    NASA Technical Reports Server (NTRS)

    Zheng, Z. C.; Baek, K.

    1998-01-01

    Aircraft trailing vortices can be influenced significantly by atmospheric conditions such as crosswind, turbulence, and stratification. According to the NASA 1994 and 1995 field measurement program in Memphis, Tennessee, the descending aircraft wake vortices could stall or be deflected at the top of low-level temperature inversions that usually produce pronounced shear zones. Numerical simulations of vortex/shear interactions with ground effects have been performed by several groups. Burnham used a series of evenly spaced line vortices at a particular altitude to model the ground shear layer of the cross- wind. He found that the wind shear was swept up around the downwind vortex and caused the downwind vortex to move upward, and claimed that the effect was actually produced by the vertical gradient in the wind shear rather than by the wind shear directly, because uniformly distributed wind-shear vortices would have no effect on the trailing vortex vertical motion. Recently, Proctor et al. numerically tested the effects of narrow shear zones on the behavior of the vortex pair, motivated by the observation of the Memphis field data. The shear-layer sensitivity tests indicated that the downwind vortex was more sensitive and deflected to a higher altitude than its upwind counterpart. The downstream vortex contained vorticity of opposite sign to that of the shear. There was no detectable preference for the downwind vortex (or upwind vortex) to weaken (or strengthen) at a greater rate.

  20. Shear thickening, shear localization and elastic turbulence.

    NASA Astrophysics Data System (ADS)

    Bonn, Daniel

    2006-03-01

    The vast majority of complex fluids is shear thinning. The mechanisms of shear thinning are relatively well understood, and the phenomenon is widely used to tailor the rheology of complex fluids. Shear thickening is the exception to this rule, is incompletely understood and hardly ever used to tailor fluid properties. We study shear thickening in granular pastes (cornstarch), and show that shear localization (banding) is an essential ingredient for shear thickening. For high flow rates, the shear banding is followed by ‘elastic turbulence’. Our measurements provide us with the mechanism of both shear thickening and the flow instabilities that result from it.

  1. Lagrangian Coherent Structure Analysis of Terminal Winds Detected by Lidar. Part I: Turbulence Structures

    E-print Network

    Tang, Wenbo

    Lagrangian Coherent Structure Analysis of Terminal Winds Detected by Lidar. Part I: Turbulence, and wind shear. Based on a recently developed finite-domain­finite-time Lyapunov exponent (FDFTLE significant low- altitude wind shear. Such wind shear is an aviation hazard as it may change the lift

  2. Role of velocity shears in turbulent dissipation

    NASA Astrophysics Data System (ADS)

    Parashar, T. N.; Ghosh, S.

    2013-12-01

    The discussion about what processes are important in solar wind plasma heating usually concentrates on wave particle interactions or on energization by low frequency structures like current sheets and reconnection sites. Less attention has been paid to the role of local velocity shears in plasma heating. We study this problem using Hall-FLR MHD and hybrid codes. We see that the velocity shear sites are related to hot spots and most of the dissipated energy comes from velocity shears. The ultimate energy deposition mechanism is electromagnetic interactions but these interactions are enhanced at the velocity shear sites making them an attractive candidate for sites of dissipation along with magnetic shear sites like the current sheets and reconnection sites.

  3. Speed and Direction Shear in the Stable Nocturnal Boundary Layer

    SciTech Connect

    Walter, K.; Weiss, C. C.; Swift, A. H. P.; Chapman, J.; Kelley, N. D.

    2009-02-01

    Numerous previous works have shown that vertical shear in wind speed and wind direction exist in the atmospheric boundary layer. In this work, meteorological forcing mechanisms, such as the Ekman spiral, thermal wind, and inertial oscillation, are discussed as likely drivers of such shears in the statically stable environment. Since the inertial oscillation, the Ekman spiral, and statically stable conditions are independent of geography, potentially significant magnitudes of speed and direction shear are hypothesized to occur to some extent at any inland site in the world. The frequency of occurrence of non-trivial magnitudes of speed and direction shear are analyzed from observation platforms in Lubbock, Texas and Goodland, Indiana. On average, the correlation between speed and direction shear magnitudes and static atmospheric stability are found to be very high. Moreover, large magnitude speed and direction shears are observed in conditions with relatively high hub-height wind speeds. The effects of speed and direction shear on wind turbine power performance are tested by incorporating a simple steady direction shear profile into the fatigue analysis structures and turbulence simulation code from the National Renewable Energy Laboratory. In general, the effect on turbine power production varies with the magnitude of speed and direction shear across the turbine rotor, with the majority of simulated conditions exhibiting power loss relative to a zero shear baseline. When coupled with observational data, the observed power gain is calculated to be as great as 0.5% and depletion as great as 3% relative to a no shear baseline. The average annual power change at Lubbock is estimated to be -0.5%

  4. Wind turbine acoustics

    NASA Technical Reports Server (NTRS)

    Hubbard, Harvey H.; Shepherd, Kevin P.

    1990-01-01

    Available information on the physical characteristics of the noise generated by wind turbines is summarized, with example sound pressure time histories, narrow- and broadband frequency spectra, and noise radiation patterns. Reviewed are noise measurement standards, analysis technology, and a method of characterizing wind turbine noise. Prediction methods are given for both low-frequency rotational harmonics and broadband noise components. Also included are atmospheric propagation data showing the effects of distance and refraction by wind shear. Human perception thresholds, based on laboratory and field tests, are given. Building vibration analysis methods are summarized. The bibliography of this report lists technical publications on all aspects of wind turbine acoustics.

  5. Mitigating shear lag in tall buildings

    NASA Astrophysics Data System (ADS)

    Gaur, Himanshu; Goliya, Ravindra K.

    2015-09-01

    As the height of building increases, effect of shear lag also becomes considerable in the design of high-rise buildings. In this paper, shear lag effect in tall buildings of heights, i.e., 120, 96, 72, 48 and 36 stories of which aspect ratio ranges from 3 to 10 is studied. Tube-in-tube structural system with façade bracing is used for designing the building of height 120 story. It is found that bracing system considerably reduces the shear lag effect and hence increases the building stiffness to withstand lateral loads. Different geometric patterns of bracing system are considered. The best effective geometric configuration of bracing system is concluded in this study. Lateral force, as wind load is applied on the buildings as it is the most dominating lateral force for such heights. Wind load is set as per Indian standard code of practice IS 875 Part-3. For analysis purpose SAP 2000 software program is used.

  6. A model of Barchan dunes including lateral shear stress.

    PubMed

    Schwämmle, V; Herrmann, H J

    2005-01-01

    Barchan dunes are found where sand availability is low and wind direction quite constant. The two dimensional shear stress of the wind field and the sand movement by saltation and avalanches over a barchan dune are simulated. The model with one dimensional shear stress is extended including surface diffusion and lateral shear stress. The resulting final shape is compared to the results of the model with a one dimensional shear stress and confirmed by comparison to measurements. We found agreement and improvements with respect to the model with one dimensional shear stress. Additionally, a characteristic edge at the center of the windward side is discovered which is also observed for big barchans. Diffusion effects reduce this effect for small dunes. PMID:15688141

  7. Optimal recovery from microburst wind shear

    NASA Technical Reports Server (NTRS)

    Mulgund, Sandeep S.; Stengel, Robert F.

    1992-01-01

    The flight path of a twin-jet transport aircraft is optimized in a microburst encounter during approach to landing. The objective is to execute an escape maneuver that maintains safe ground clearance and an adequate stall margin during the climb-out portion of the trajectory. A cost function penalizing rate of climb deviations from a nominal value and rate of elevator deflection produces qualitatively good results in a variety of microburst encounters. The optimal maneuver is a gradual pitch-up that ceases near the core of the microburst, followed by a slight reduction in pitch attitude in the tailwind area of the microburst. A minimum airspeed constraint in the optimization prevents excessive airspeed loss in very severe microbursts. The aircraft equations of motion include short-period dynamics, so that the optimization solves directly for the control surface deflections required to achieve the optimal flight paths.

  8. Advanced technology wind shear prediction system evaluation

    NASA Technical Reports Server (NTRS)

    Gering, Greg

    1992-01-01

    The program overviews: (1) American Airline (AA)/Turbulence Prediction Systems (TPS), which have installed forward looking infrared predictive windshear system on 3 MD-80 aircraft; (2) AA/TPS AWAS III evaluation, which is a joint effort and is installed in the noise landing gear (NLG) area and a data recorder installed in the E/E compartment.

  9. Reduced shear power spectrum

    SciTech Connect

    Dodelson, Scott; Shapiro, Charles; White, Martin J.; /UC, Berkeley, Astron. Dept. /UC, Berkeley

    2005-08-01

    Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by (1-{kappa}) where {kappa} is the projected density field. They compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important an smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.

  10. Multi-hazard Reliability Assessment of Offshore Wind Turbines 

    E-print Network

    Mardfekri Rastehkenari, Maryam 1981-

    2012-12-04

    A probabilistic framework is developed to assess the structural reliability of offshore wind turbines. Probabilistic models are developed to predict the deformation, shear force and bending moment demands on the support structure of wind turbines...

  11. Microburst vertical wind estimation from horizontal wind measurements

    NASA Technical Reports Server (NTRS)

    Vicroy, Dan D.

    1994-01-01

    The vertical wind or downdraft component of a microburst-generated wind shear can significantly degrade airplane performance. Doppler radar and lidar are two sensor technologies being tested to provide flight crews with early warning of the presence of hazardous wind shear. An inherent limitation of Doppler-based sensors is the inability to measure velocities perpendicular to the line of sight, which results in an underestimate of the total wind shear hazard. One solution to the line-of-sight limitation is to use a vertical wind model to estimate the vertical component from the horizontal wind measurement. The objective of this study was to assess the ability of simple vertical wind models to improve the hazard prediction capability of an airborne Doppler sensor in a realistic microburst environment. Both simulation and flight test measurements were used to test the vertical wind models. The results indicate that in the altitude region of interest (at or below 300 m), the simple vertical wind models improved the hazard estimate. The radar simulation study showed that the magnitude of the performance improvement was altitude dependent. The altitude of maximum performance improvement occurred at about 300 m.

  12. Dipole shear anisotropy logging

    SciTech Connect

    Esmersoy, C.; Kane, M.; Koster, K.; Williams, M.; Boyd, A.

    1994-12-31

    Sonic-scale shear anisotropy of formations are obtained from dipole-shear measurements acquired by orthogonal source and receiver pairs. These measurements resemble miniature 4-component shear VSP surveys inside the borehole. Data from two orthogonal sources and an array of orthogonal receivers are processed providing three main logs; the fast and slow shear slownesses, and the fast shear polarization angle. Potential applications include: shale anisotropy for better seismic models, maximum stress and fracture/microcrack strike direction for horizontal well drilling and fracture height and azimuth determination in hydraulic fracturing.

  13. Interpretation of combined wind profiler and aircraft-measured tropospheric winds and clear air turbulence

    NASA Technical Reports Server (NTRS)

    Thomson, D. W.; Syrett, William J.; Fairall, C. W.

    1991-01-01

    In the first experiment, it was found that wind profilers are far better suited for the detailed examination of jet stream structure than are weather balloons. The combination of good vertical resolution with not previously obtained temporal resolution reveals structural details not seen before. Development of probability-derived shear values appears possible. A good correlation between pilot reports of turbulence and wind shear was found. In the second experiment, hourly measurements of wind speed and direction obtained using two wind profiling Doppler radars during two prolonged jet stream occurrences over western Pennsylvania were analyzed. In particular, the time-variant characteristics of derived shear profiles were examined. Profiler data dropouts were studied in an attempt to determine possible reasons for the apparently reduced performance of profiling radar operating beneath a jet stream. Richardson number and wind shear statistics were examined along with pilot reports of turbulence in the vicinity of the profiler.

  14. Shearing stability of lubricants

    NASA Technical Reports Server (NTRS)

    Shiba, Y.; Gijyutsu, G.

    1984-01-01

    Shearing stabilities of lubricating oils containing a high mol. wt. polymer as a viscosity index improver were studied by use of ultrasound. The oils were degraded by cavitation and the degradation generally followed first order kinetics with the rate of degradation increasing with the intensity of the ultrasonic irradiation and the cumulative energy applied. The shear stability was mainly affected by the mol. wt. of the polymer additive and could be determined in a short time by mechanical shearing with ultrasound.

  15. Shear Thinning in Xenon

    NASA Technical Reports Server (NTRS)

    Bergm Robert F.; Moldover, Michael R.; Yao, Minwu; Zimmerli, Gregory A.

    2009-01-01

    We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids such as molten plastics or ketchup, near the critical point of xenon. The data span a wide range of dimensionless shear rate: the product of the shear rate and the relaxation time of critical fluctuations was greater than 0.001 and was less than 700. As predicted by theory, shear thinning occurred when this product was greater than 1. The measurements were conducted aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity.

  16. TURBULENT SHEAR ACCELERATION

    SciTech Connect

    Ohira, Yutaka

    2013-04-10

    We consider particle acceleration by large-scale incompressible turbulence with a length scale larger than the particle mean free path. We derive an ensemble-averaged transport equation of energetic charged particles from an extended transport equation that contains the shear acceleration. The ensemble-averaged transport equation describes particle acceleration by incompressible turbulence (turbulent shear acceleration). We find that for Kolmogorov turbulence, the turbulent shear acceleration becomes important on small scales. Moreover, using Monte Carlo simulations, we confirm that the ensemble-averaged transport equation describes the turbulent shear acceleration.

  17. Strongly sheared stratocumulus convection: an observationally based large-eddy simulation study

    NASA Astrophysics Data System (ADS)

    Wang, S.; Zheng, X.; Jiang, Q.

    2012-02-01

    Unusually large wind shears across the inversion in the stratocumulus-topped marine boundary layer (MBL) were frequently observed during VOCALS-REx. To investigate the impact of wind shear on the MBL turbulence structure, a large-eddy simulation (LES) model is used to simulate the strongly sheared MBL observed from Twin-Otter RF 18 on 13 November 2008. The LES simulated turbulence statistics agree in general with those derived from the measurements, with the MBL exhibiting a decoupled structure characterized by an enhanced entrainment and a turbulence intensity minimum just below the clouds. Sensitivity simulations show that the shear tends to reduce the dynamic stability of the inversion, enhance the entrainment mixing, and decrease the cloud water. Consequently, the turbulence intensity in the MBL is significantly weakened by the intense wind shear. The inversion thickens considerably and the MBL top separates from the cloud top, creating a finite cloud-free sublayer of 10-50 m thickness within the inversion, depending on the shear intensity. The wind shear enhances the turbulence buoyant consumption within the inversion, and simultaneously weakens the buoyant production in the cloud layer. These effects may result in different heating rates between the cloud and subcloud layer, leading to a process that tends to decouple the cloud from the subcloud layer. The decoupling process occurs even without solar radiation in the case of an intense wind shear similar to the observations.

  18. Surface flow visualization with shear stress sensitivive liquid crystals

    NASA Astrophysics Data System (ADS)

    Pengel, K.

    The use of non-capsulated liquid crystals, which react directly to wall shear forces, for surface flow visualization, is presented. The temperature sensitivity is avoided by producing a mixture with an event temperature (first red indication temperature) above the expected investigation temperature range. Below the event temperature the liquid crystals are only sensitive to shear stress, resulting in a wavelength variation of the reflected light. The analysis of video pictures from a low speed wind tunnel lead to information about the wall shear stress distribution on an Airbus wing, and in particular about the detection of the laminar to turbulent boundary layer transition.

  19. Internal gravity wave-atmospheric wind interaction - A cause of clear air turbulence.

    NASA Technical Reports Server (NTRS)

    Bekofske, K.; Liu, V. C.

    1972-01-01

    The interaction between an internal gravity wave (IGW) and a vertical wind shear is discussed as a possible cause in the production of clear air turbulence in the free atmosphere. It is shown that under certain typical condition the interaction of an IGW with a background wind shear near a critical level provides a mechanism for depositing sufficient momentum in certain regions of the atmosphere to significantly increase the local mean wind shear and to lead to the production of turbulence.

  20. Bacteria in shear flow

    E-print Network

    Marcos, Ph.D. Massachusetts Institute of Technology

    2011-01-01

    Bacteria are ubiquitous and play a critical role in many contexts. Their environment is nearly always dynamic due to the prevalence of fluid flow: creeping flow in soil, highly sheared flow in bodily conduits, and turbulent ...

  1. Shear Unzipping of DNA

    E-print Network

    Buddhapriya Chakrabarti; David R. Nelson

    2009-04-09

    We study theoretically the mechanical failure of a simple model of double stranded DNA under an applied shear. Starting from a more microscopic Hamiltonian that describes a sheared DNA, we arrive at a nonlinear generalization of a ladder model of shear unzipping proposed earlier by deGennes [deGennes P. G. C. R. Acad. Sci., Ser. IV; Phys., Astrophys. 2001, 1505]. Using this model and a combination of analytical and numerical methods, we study the DNA "unzipping" transition when the shearing force exceeds a critical threshold at zero temperature. We also explore the effects of sequence heterogeneity and finite temperature and discuss possible applications to determine the strength of colloidal nanoparticle assemblies functionalized by DNA.

  2. Excitation of vortex meandering in shear flow

    NASA Astrophysics Data System (ADS)

    Schröttle, Josef; Dörnbrack, Andreas; Schumann, Ulrich

    2015-06-01

    This paper investigates the evolution of a streamwise aligned columnar vortex with vorticity {\\boldsymbol{ ? }} in an axial background shear of magnitude ? by means of linear stability analysis and numerical simulations. A long wave mode of vorticity normal to the plane spanned by the background shear vector {\\boldsymbol{ ? }} and the vorticity of the vortex are excited by an instability. The stationary wave modes of the vertical and lateral vorticity are amplified. In order to form a helical vortex, the lateral and vertical vorticity can be phase shifted by half a wavelength. The linear and nonlinear evolutions of the vortex in the shear flow are studied numerically. Linearized simulations confirm the results of the stability analysis. The nonlinear simulations reveal further evolution of the helix in the shear flow. The linearly excited mode persists in co-existence with evolving smaller scale instabilities until the flow becomes fully turbulent at the time of O(100 {{? }-1}). Turbulent mixing dampens the amplifying mode. The described phenomenon of vortex meandering may serve as an alternative explanation for the excitation of wind turbine wake meandering in the atmospheric boundary layer.

  3. WAVE ACTION AND BOTTOM SHEAR STRESSES IN LAKE ERIE

    EPA Science Inventory

    For Lake Erie, the amplitudes and periods of wind-driven, surface gravity waves were calculated by means of the SMB hindcasting method. Bottom orbital velocities and bottom shear stresses were then calculated using linear wave theory and Kajiura's (1968) turbulent oscillating bou...

  4. Analysis of Rhode Island Coastal Wind Profiles

    NASA Astrophysics Data System (ADS)

    Knorr, K. I.; Merrill, J. T.

    2012-12-01

    Eleven wind profile data sets were collected at sites in Rhode Island between 2007 and the present, extending over periods from 6 to 20 months, with a mean of 14 months. The data was gathered from meteorological towers via anemometers and wind vanes at heights up to 60 m, or using SoDAR (Sonic Detection And Ranging) instruments at heights up to 200 m. Wind speeds are generally greater in the fall and winter, with minimum wind speeds occurring in the summer. Winds blow most frequently from the northwest in the winter and from the southwest in the summer. The power law describes wind speed with height in neutral static stability conditions; the fitted shear coefficient characterizes the distribution and is used in wind resource assessment. Marine sites exhibit higher wind speeds and lower shear than terrestrial sites, due to lower surface drag. In contrast, terrestrial sites experience more shear and greater temporal variability. The magnitude of diel and seasonal differences between marine and terrestrial locations will be discussed. The land-breeze sea-breeze cycle influences wind throughout the study area; the magnitude of this variation, along with azimuthal shear will be considered. In addition to the short-term profile data, we used several multi-decadal single height anemometer data sets. Wind estimates at hub height over an extended time period calculated using Measure Correlate Predict (MCP) algorithms will be discussed in the context of hypothesized temporal trends in the wind speeds. Utilization of such data for wind energy and other applications will be discussed.

  5. Shear strength of metals under uniaxial deformation and pure shear

    NASA Astrophysics Data System (ADS)

    Latypov, F. T.; Mayer, A. E.

    2015-11-01

    In this paper, we investigate the dynamic shear strength of perfect monocrystalline metals using the molecular dynamics simulation. Three types of deformation (single shear, uniaxial compression and tension) are investigated for five metals of different crystallographic systems (fcc, bcc and hcp). A strong dependence of the calculated shear strength on the deformation type is observed. In the case of bcc (iron) and hcp (titanium) metals, the maximal shear strength is achieved at the uniaxial compression, while the minimal shear strength is observed at the uniaxial tension. In the case of fcc metals (aluminum, copper, nickel) the largest strength is achieved at the pure shear, the lowest strength is obtained at the uniaxial compression.

  6. Shear thickening of cornstarch suspensions

    E-print Network

    Abdoulaye Fall; François Bertrand; Guillaume Ovarlez; Daniel Bonn

    2012-06-08

    We study the rheology of cornstarch suspensions, a non-Brownian particle system that exhibits discontinuous shear thickening. Using magnetic resonance imaging (MRI), the local properties of the flow are obtained by the determination of local velocity profiles and concentrations in a Couette cell. For low rotational rates, we observe shear localization characteristic of yield stress fluids. When the overall shear rate is increased, the width of the sheared region increases. The discontinuous shear thickening is found to set in at the end of this shear localization regime when all of the fluid is sheared: the existence of a nonflowing region, thus, seems to prevent or delay shear thickening. Macroscopic observations using different measurement geometries show that the smaller the gap of the shear cell, the lower the shear rate at which shear thickening sets in. We, thus, propose that the discontinuous shear thickening of cornstarch suspensions is a consequence of dilatancy: the system under flow attempts to dilate but instead undergoes a jamming transition, because it is confined. This proposition is confirmed by an independent measurement of the dilation of the suspension as a function of the shear rate. It is also explains the MRI observations: when flow is localized, the nonflowing region plays the role of a "dilatancy reservoir" which allows the material to be sheared without jamming.

  7. Shear thickening of cornstarch suspensions

    NASA Astrophysics Data System (ADS)

    Fall, Abdoulaye; Bertrand, François; Ovarlez, Guillaume; Bonn, Daniel

    We study the rheology of cornstarch suspensions, a non-Brownian particle system that exhibits discontinuous shear thickening. Using magnetic resonance imaging (MRI), the local properties of the flow are obtained by the determination of local velocity profiles and concentrations in a Couette cell. For low rotational rates, we observe shear localization characteristic of yield stress fluids. When the overall shear rate is increased, the width of the sheared region increases. The discontinuous shear thickening is found to set in at the end of this shear localization regime when all of the fluid is sheared: the existence of a nonflowing region, thus, seems to prevent or delay shear thickening. Macroscopic observations using different measurement geometries show that the smaller the gap of the shear cell, the lower the shear rate at which shear thickening sets in. We, thus, propose that the discontinuous shear thickening of cornstarch suspensions is a consequence of dilatancy: the system under flow attempts to dilate but instead undergoes a jamming transition, because it is confined. This proposition is confirmed by an independent measurement of the dilation of the suspension as a function of the shear rate. It is also explains the MRI observations: when flow is localized, the nonflowing region plays the role of a "dilatancy reservoir" which allows the material to be sheared without jamming.

  8. Free volume under shear.

    PubMed

    Maiti, Moumita; Vinutha, H A; Sastry, Srikanth; Heussinger, Claus

    2015-10-14

    Using an athermal quasistatic simulation protocol, we study the distribution of free volumes in sheared hard-particle packings close to, but below, the random-close packing threshold. We show that under shear, and independent of volume fraction, the free volumes develop features similar to close-packed systems - particles self-organize in a manner as to mimick the isotropically jammed state. We compare athermally sheared packings with thermalized packings and show that thermalization leads to an erasure of these structural features. The temporal evolution in particular the opening-up and the closing of free-volume patches is associated with the single-particle dynamics, showing a crossover from ballistic to diffusive behavior. PMID:26472384

  9. Free volume under shear

    NASA Astrophysics Data System (ADS)

    Maiti, Moumita; Vinutha, H. A.; Sastry, Srikanth; Heussinger, Claus

    2015-10-01

    Using an athermal quasistatic simulation protocol, we study the distribution of free volumes in sheared hard-particle packings close to, but below, the random-close packing threshold. We show that under shear, and independent of volume fraction, the free volumes develop features similar to close-packed systems — particles self-organize in a manner as to mimick the isotropically jammed state. We compare athermally sheared packings with thermalized packings and show that thermalization leads to an erasure of these structural features. The temporal evolution in particular the opening-up and the closing of free-volume patches is associated with the single-particle dynamics, showing a crossover from ballistic to diffusive behavior.

  10. Free volume under shear

    E-print Network

    Moumita Maiti; H. A. Vinutha; Srikanth Sastry; Claus Heussinger

    2015-06-20

    Using an athermal quasistatic simulation protocol, we study the distribution of free volumes in sheared hard-particle packings close to, but below, the random-close packing threshold. We show that under shear, and independent of volume fraction, the free volumes develop features similar to close-packed systems -- particles self-organize in a manner as to mimick the isotropically jammed state. We compare athermally sheared packings with thermalized packings and show that thermalization leads to an erasure of these structural features. The temporal evolution, in particular the opening-up and the closing of free-volume patches is associated with the single-particle dynamics, showing a crossover from ballistic to diffusive behavior.

  11. Final Report for The Creation of a Physics-based Ground-effect Model, Phase 2 - Inclusion of the Effects of Wind, Stratification, and Shear into the New Ground Effect Model

    NASA Technical Reports Server (NTRS)

    Sarpkaya, Turgut

    2006-01-01

    The reduction of the separation of the leading and following aircrafts is desirable to enhance the airport capacity provided that there is a physics-based operational model applicable to all regions of the flight domain (out of ground effect, OGE; near ground effect, NGE; and in ground effect, IGE) and that the quality of the quantitative input from the measurements of the prevailing atmospheric conditions and the quality of the total airport operations regarding the safety and the sound interpretation of the prevailing conditions match the quality of the analysis and numerical simulations. In the absence of an analytical solution, the physics of the flow is best expressed by a mathematical model based on numerical simulations, field and laboratory experiments, and heuristic reasoning. This report deals with the creation of a sound physics-based real-time IGE model of the aircraft wake vortices subjected to crosswind, stratification and shear.

  12. Ultrasonic shear wave couplant

    DOEpatents

    Kupperman, David S. (Oak Park, IL); Lanham, Ronald N. (Lockport, IL)

    1985-01-01

    Ultrasonically testing of an article at high temperatures is accomplished by the use of a compact layer of a dry ceramic powder as a couplant in a method which involves providing an ultrasonic transducer as a probe capable of transmitting shear waves, coupling the probe to the article through a thin compact layer of a dry ceramic powder, propagating a shear wave from the probe through the ceramic powder and into the article to develop echo signals, and analyzing the echo signals to determine at least one physical characteristic of the article.

  13. Ultrasonic shear wave couplant

    DOEpatents

    Kupperman, D.S.; Lanham, R.N.

    1984-04-11

    Ultrasonically testing of an article at high temperatures is accomplished by the use of a compact layer of a dry ceramic powder as a couplant in a method which involves providing an ultrasonic transducer as a probe capable of transmitting shear waves, coupling the probe to the article through a thin compact layer of a dry ceramic powder, propagating a shear wave from the probe through the ceramic powder and into the article to develop echo signals, and analyzing the echo signals to determine at least one physical characteristic of the article.

  14. 2009 ASME WIND ENERGY SYMPOSIUM Static and Fatigue Testing of Thick Adhesive Joints for

    E-print Network

    1 2009 ASME WIND ENERGY SYMPOSIUM Static and Fatigue Testing of Thick Adhesive Joints for Wind as wind blade size has increased. Typical blade joints use paste adhesives several millimeters thick aircraft, which are also of relevance to wind blades in many instances. The strengths of lap-shear and many

  15. Radial Heliospheric Magnetic Fields in Solar Wind Rarefaction Regions: Ulysses Observations

    E-print Network

    Sanahuja, Blai

    Radial Heliospheric Magnetic Fields in Solar Wind Rarefaction Regions: Ulysses Observations D it observed solar wind shears from the incursions of high-latitude fast solar wind toward the low-latitude slow solar wind. We look for nearly radial field orientations commonly observed in rarefaction regions

  16. Wind Turbines Adaptation to the Variability of the Wind Field

    NASA Astrophysics Data System (ADS)

    Ulianov, Yuriy; Martynenko, Gennadii; Misaylov, Vitaliy; Soliannikova, Iuliia

    2010-05-01

    WIND TURBINES ADAPTATION TO THE VARIABILITY OF THE WIND FIELD The subject of our scientific research is wind power turbines (WPT) with the horizontal axis which were now common in the world. Efficient wind turbines work is largely determined by non-stationarity of the wind field, expressed in its gustiness, the presence of vertical and horizontal shifts of wind speed and direction. At critical values of the wind parameters WPT has aerodynamic and mechanical overload, leading to breakdowns, premature wear and reduce the life of the wind turbine. To prevent accidents at the peak values of wind speed it is used the regulatory system of windwheels. WPT control systems provide a process orientation of the wind turbine rotor axis in the line of the mean wind. Wind turbines are also equipped with braking device used to protect against breakdowns when a significant increase in the wind. In general, all these methods of regulation are not always effective. Thus, in practice there may be situations when the wind speed is many times greater than the stated limit. For example, if there are microbursts in the atmospheric boundary layer, low-level wind shears caused by its gust front, storms, etc. It is required for a wind power turbine adaptation to intensive short-term wind impulses and considerable vertical wind shifts that the data about them shall be obtained ahead of time. To do this it is necessary to have the information on the real structure of the wind field in the area of the blade sweep for the minimum range against the wind that is determined by the mean speed and the system action time. The implementation of acoustic and laser traditional wind sounding systems is limited by ambient acoustic noise, by heavy rain, snowfall and by fog. There are free of these disadvantages the inclined radioacoustic sounding (IRASS) technique which works for a system of remote detection and control of wind gusts. IRASS technique is realized as low-potential Doppler pulse radar including combined RF-acoustic antenna installed coaxially with the gondola of the wind power turbine. The work of the technique is synchronized with rotation of blades to eliminate their shielding action. Dangerous in terms of dynamic strength is the wind load pulse, the rise time which is comparable with the period of the natural frequency of the wind turbine elements (blade, tower, rotor, etc.). The amplitude decay of resonant vibrations at critical values of the speed of rotation can be realized through the use of mechanical elastic supports with nonlinear artificial dampers. They have a high coefficient of resistance, but may cause self-excited oscillations. We propose the way to deal with raised vibration of wind turbine elements at the expense of short-term increase of damping in the range of critical rotary axis speeds or during impulsive effects of wind loadings (wind gusts). This is possible through the use of non-linear electromagnetic dampers or active magnetic bearings. Their feature is the possibility of varying the mechanical stiffness and damping properties by changing the electrical parameters of electromagnets. The controlling of these parameters is carried out by the control system (CS) with the information feedback on the spatial-temporal structure of the wind field obtained from IRASS. In the composition of the CS can also be included the rotational speed sensor of the WPT rotor. This approach to the adaptation of wind turbines will allow to reduce vibration and to perform early compensation of the load on their components, which arise under the wind gusts. In addition, corrections about the wind field obtained with IRASS, would increase the mean power of WPT.

  17. Vortices in shear

    NASA Astrophysics Data System (ADS)

    Meacham, Stephen P.; Flierl, Glenn R.; Send, Uwe

    1989-01-01

    The nature and stability of Kida's exact, time-dependent solutions for uniform, elliptical vortices in an ambient strain field are investigated. In addition to the classical Love mode of instability, we discover a class of resonant instabilities. Our linearized analysis is supplemented by numerical simulations of vortices in shear which follow the non-linear development of some of these instabilities.

  18. Wind Simulation

    Energy Science and Technology Software Center (ESTSC)

    2008-12-31

    The Software consists of a spreadsheet written in Microsoft Excel that provides an hourly simulation of a wind energy system, which includes a calculation of wind turbine output as a power-curve fit of wind speed.

  19. Determination of surface shear stress with the naphthalene sublimation technique

    NASA Technical Reports Server (NTRS)

    Lee, J. A.; Greeley, Ronald

    1987-01-01

    Aeolian entrainment and transport are functions of surface shear stress and particle characteristics. Measuring surface shear stress is difficult, however, where logarithmic wind profiles are not found, such as regions around large roughness elements. An outline of a method whereby shear stress can be mapped on the surface around an object is presented. The technique involves the sublimation of naphthalene (C10H8) which is a function of surface shear stress and surface temperature. This technique is based on the assumption that the transfer of momentum, heat and mass are analogous (Reynolds analogy). If the Reynolds analogy can be shown to be correct for a given situation, then knowledge of the diffusion of one property allows the determination of the others. The analytical framework and data acquisition for the method are described. The technique was tested in the Planetary Geology Wind Tunnel. Results show that the naphthalene sublimation technique is a reasonably accurate method for determining shear stress, particularly around objects where numerous point values are needed.

  20. Thermal and humidity winds in outer planet atmospheres

    SciTech Connect

    Sun, Zi-Ping; Schubert, G.; Stoker, C.R. NASA, Ames Research Center, Moffett Field, CA )

    1991-05-01

    Among the dynamical consequences of molecular weight variations due to condensation in hydrogen atmospheres is the creation of geostrophic wind variations by horizontal variations in molecular weight. In the present illustrative model, it is shown that such horizontal gradients are generated by methane condensation in the cases of the Uranus and Neptune atmospheres. As a result, the zonal wind shear is different in both magnitude and direction from the value determined while neglecting molecular weight variations. The horizontal molecular weight gradients due to condensation of minor constituents also vertically shear the zonal wind, giving rise to what may be termed the 'humidity wind'. 15 refs.

  1. Imaging Faults and Shear Zones Using Receiver Functions

    NASA Astrophysics Data System (ADS)

    Schulte-Pelkum, Vera; Mahan, Kevin H.

    2014-11-01

    The geometry of faults at seismogenic depths and their continuation into the ductile zone is of interest for a number of applications ranging from earthquake hazard to modes of lithospheric deformation. Teleseismic passive source imaging of faults and shear zones can be useful particularly where faults are not outlined by local seismicity. Passive seismic signatures of faults may arise from abrupt changes in lithology or foliation orientation in the upper crust, and from mylonitic shear zones at greater depths. Faults and shear zones with less than near-vertical dip lend themselves to detection with teleseismic mode-converted waves (receiver functions) provided that they have either a contrast in isotropic shear velocity ( V s), or a contrast in orientation or strength of anisotropic compressional velocity ( V p). We introduce a detection method for faults and shear zones based on receiver functions. We use synthetic seismograms to demonstrate common features of dipping isotropic interfaces and contrasts in dipping foliation that allows determination of their strike and depth without making further assumptions about the model. We proceed with two applications. We first image a Laramide thrust fault in the western U.S. (the Wind River thrust fault) as a steeply dipping isotropic velocity contrast in the middle crust near the surface trace of the fault; further downdip and across the range, where basin geometry suggests the fault may sole into a subhorizontal shear zone, we identify a candidate shear zone signal from midcrustal depths. The second application is the use of microstructural data from exhumed ductile shear zones in Scotland and in the western Canadian Shield to predict the character of seismic signatures of present-day deep crustal shear zones. Realistic anisotropy in observed shear fabrics generates a signal in receiver functions that is comparable in amplitude to first-order features like the Moho. Observables that can be robustly constrained without significant tradeoffs are foliation strike and the depth of the foliation contrast. We find that an anisotropy of only a few percent in the shear zone is sufficient to generate a strong signal, but that the shear zone width is required to be >2 km for typical frequencies used in receiver function analysis to avoid destructive interference due to the signals from the boundaries of the shear zone.

  2. Observation of Shear-Induced Turbulence Using HARLIE

    NASA Technical Reports Server (NTRS)

    Miller, David O.; Schwemmer, Geary K.; Wilkerson, Thomas D.; Sanders, Jason; Guerra, David; Moody, Steven

    2000-01-01

    Ground-based measurements of atmospheric aerosol structure were made using the Holographic Airborne Rotating Lidar Instrument Experiment (HARLIE) during the HOLO-1 field campaign. The scanning ability of HARLIE affords a unique opportunity to view various atmospheric phenomena. Shear-induced turbulence plays an important role in the transport of kinetic energy in the atmosphere and on March 10, 1999, several instances of shear-induced turbulence were observed via HARLIE. Using the data collected and upper-air wind profiles the nature of the instabilities is discussed.

  3. Application and improvement of Raupach's shear stress partitioning model

    NASA Astrophysics Data System (ADS)

    Walter, B. A.; Lehning, M.; Gromke, C.

    2012-12-01

    Aeolian processes such as the entrainment, transport and redeposition of sand, soil or snow are able to significantly reshape the earth's surface. In times of increasing desertification and land degradation, often driven by wind erosion, investigations of aeolian processes become more and more important in environmental sciences. The reliable prediction of the sheltering effect of vegetation canopies against sediment erosion, for instance, is a clear practical application of such investigations to identify suitable and sustainable counteractive measures against wind erosion. This study presents an application and improvement of a theoretical model presented by Raupach (Boundary-Layer Meteorology, 1992, Vol.60, 375-395 and Journal of Geophysical Research, 1993, Vol.98, 3023-3029) which allows for quantifying the sheltering effect of vegetation against sediment erosion. The model predicts the shear stress ratios ?S'/? and ?S''/?. Here, ?S is the part of the total shear stress ? that acts on the ground beneath the plants. The spatial peak ?S'' of the surface shear stress is responsible for the onset of particle entrainment whereas the spatial mean ?S' can be used to quantify particle mass fluxes. The precise and accurate prediction of these quantities is essential when modeling wind erosion. Measurements of the surface shear stress distributions ?S(x,y) on the ground beneath live vegetation canopies (plant species: lolium perenne) were performed in a controlled wind tunnel environment to determine the model parameters and to evaluate the model performance. Rigid, non-porous wooden blocks instead of the plants were additionally tested for the purpose of comparison, since previous wind tunnel studies used exclusively artificial plant imitations for their experiments on shear stress partitioning. The model constant c, which is needed to determine the total stress ? for a canopy of interest and which remained rather unspecified to date, was found to be c ? 0.27. It was also found that the model parameter m, which relates ?S'' with ?S' and which is needed to determine the peak surface shear stress ?S'', is rather impractically defined in the original model formulation, because m is identified to be a function of the wind velocity, the roughness element shape and the roughness density. We propose an alternative, more universal definition of an a-parameter as a substitute for the m-parameter simply linearly relating ?S'' with ?S'. This strong linear relation is supported by the measurements and can be made plausible with simple fluid dynamical arguments. The advantage of a over m is that a is solely a function of the roughness element shape. Finally, a method is presented to determine the new a-parameter for different kinds of roughness elements with relatively simple experimental methods.

  4. 24 CFR 3285.403 - Sidewall, over-the-roof, mate-line, and shear wall straps.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...COMMISSIONER, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Anchorage Against Wind § 3285.403 Sidewall, over-the-roof, mate-line, and shear wall straps. If sidewall, over-the-roof,...

  5. 24 CFR 3285.403 - Sidewall, over-the-roof, mate-line, and shear wall straps.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...COMMISSIONER, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Anchorage Against Wind § 3285.403 Sidewall, over-the-roof, mate-line, and shear wall straps. If sidewall, over-the-roof,...

  6. 24 CFR 3285.403 - Sidewall, over-the-roof, mate-line, and shear wall straps.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...COMMISSIONER, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Anchorage Against Wind § 3285.403 Sidewall, over-the-roof, mate-line, and shear wall straps. If sidewall, over-the-roof,...

  7. 24 CFR 3285.403 - Sidewall, over-the-roof, mate-line, and shear wall straps.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...COMMISSIONER, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Anchorage Against Wind § 3285.403 Sidewall, over-the-roof, mate-line, and shear wall straps. If sidewall, over-the-roof,...

  8. 24 CFR 3285.403 - Sidewall, over-the-roof, mate-line, and shear wall straps.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...COMMISSIONER, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Anchorage Against Wind § 3285.403 Sidewall, over-the-roof, mate-line, and shear wall straps. If sidewall, over-the-roof,...

  9. Amplitude modulation of wind turbine noise

    E-print Network

    Makarewicz, Rufin

    2013-01-01

    Due to swish and thump amplitude modulation, the noise of wind turbines cause more annoyance than other environmental noise of the same average level. The wind shear accounts for the thump modulation (van den Berg effect). Making use of the wind speed measurements at the hub height, as well as at the top and the bottom of the rotor disc (Fig.1), the non-standard wind profile is applied. It causes variations in the A-weighted sound pressure level, LpA. The difference between the maximum and minimum of LpA characterizes thump modulation (Fig.2).

  10. Shear-thinning Fluid

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Whipped cream and the filling for pumpkin pie are two familiar materials that exhibit the shear-thinning effect seen in a range of industrial applications. It is thick enough to stand on its own atop a piece of pie, yet flows readily when pushed through a tube. This demonstrates the shear-thinning effect that was studied with the Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002. CVX observed the behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The principal investigator was Dr. Robert Berg of the National Institutes of Standards and Technology in Gaithersburg, MD.

  11. Shear-thickening compositions

    SciTech Connect

    Swanson, B.L.

    1981-10-06

    Shear-thickening aqueous compositions useful as workover fluids in producing or injection wells, as water diversion agents and mobility control fluids in post-primary oil recovery operations, and as hydraulic fracturing fluids. Well stimulation treatments are provided comprising the reaction product formed from a high molecular weight polyalkylene oxide polymer and a synthetic resin produced from aldehydes and phenols in an alkaline environment.

  12. Micromechanics of shear banding

    SciTech Connect

    Gilman, J.J.

    1992-08-01

    Shear-banding is one of many instabilities observed during the plastic flow of solids. It is a consequence of the dislocation mechanism which makes plastic flow fundamentally inhomogeneous, and is exacerbated by local adiabatic heating. Dislocation lines tend to be clustered on sets of neighboring glide planes because they are heterogeneously generated; especially through the Koehler multiple-cross-glide mechanism. Factors that influence their mobilities also play a role. Strain-hardening decreases the mobilities within shear bands thereby tending to spread (delocalize) them. Strain-softening has the inverse effect. This paper reviews the micro-mechanisms of these phenomena. It will be shown that heat production is also a consequence of the heterogeneous nature of the microscopic flow, and that dislocation dipoles play an important role. They are often not directly observable, but their presence may be inferred from changes in thermal conductivity. It is argued that after deformation at low temperatures dipoles are distributed a la Pareto so there are many more small than large ones. Instability at upper yield point, the shapes of shear-band fronts, and mechanism of heat generation are also considered. It is shown that strain-rate acceleration plays a more important role than strain-rate itself in adiabatic instability.

  13. Shear thickening fluid

    SciTech Connect

    Drake, E. N.; Dawson, Ch. R.; Morrison, M. E.

    1985-03-05

    The instant invention is directed to shear thickening fluids to prevent unwanted flow in wells penetrating subterranean formations. The shear thickening fluids comprise (1) a water swellable granular clay present in sufficient quantity so that, upon interaction with an aqueous phase, a stiff paste rapidly forms having a strength of at least 2000 lbs/100 ft/sup 2/, (2) a nonaqueous phase comprising a hydrocarbon material and a surfactant, and (3) an aqueous phase comprising water and a watersoluble polymer. The granular clay and water-polymer solution are kept separated by the intervening hydrocarbon-surfactant composition, which is the continuous phase. The intervening oil phase prevents the interaction between the water-polymer phase and the granular clay and results in a stable, nonreacting, pumpable composite until such time as the granular clay is fragmented by application of a sufficiently high shear force. Upon such fragmenting, the clay and aqueous phase interact resulting in a semi-rigid high strength paste which plugs any unwanted flow.

  14. Erosion: Wind

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind erosion refers to the detachment, transport and deposition of sediment by wind. It is a dynamic, physical process where loose, dry, bare soils are transported by strong winds. Wind erosion is a soil degrading process that affects over 500 million ha of land worldwide and creates between 500 an...

  15. Sensitivity of Southern Ocean circulation to wind stress changes: Role of relative wind stress

    NASA Astrophysics Data System (ADS)

    Munday, D. R.; Zhai, X.

    2015-11-01

    The influence of different wind stress bulk formulae on the response of the Southern Ocean circulation to wind stress changes is investigated using an idealised channel model. Surface/mixed layer properties are found to be sensitive to the use of the relative wind stress formulation, where the wind stress depends on the difference between the ocean and atmosphere velocities. Previous work has highlighted the surface eddy damping effect of this formulation, which we find leads to increased circumpolar transport. Nevertheless the transport due to thermal wind shear does lose sensitivity to wind stress changes at sufficiently high wind stress. In contrast, the sensitivity of the meridional overturning circulation is broadly the same regardless of the bulk formula used due to the adiabatic nature of the relative wind stress damping. This is a consequence of the steepening of isopycnals offsetting the reduction in eddy diffusivity in their contribution to the eddy bolus overturning, as predicted using a residual mean framework.

  16. CLASS: Coherent Lidar Airborne Shear Sensor. Windshear avoidance

    NASA Technical Reports Server (NTRS)

    Targ, Russell

    1991-01-01

    The coherent lidar airborne shear sensor (CLASS) is an airborne CO2 lidar system being designed and developed by Lockheed Missiles and Space Company, Inc. (LMSC) under contract to NASA Langley Research Center. The goal of this program is to develop a system with a 2- to 4-kilometer range that will provide a warning time of 20 to 40 seconds, so that the pilot can avoid the hazards of low-altitude wind shear under all weather conditions. It is a predictive system which will warn the pilot about a hazard that the aircraft will experience at some later time. The ability of the system to provide predictive warnings of clear air turbulence will also be evaluated. A one-year flight evaluation program will measure the line-of-sight wind velocity from a wide variety of wind fields obtained by an airborne radar, an accelerometer-based reactive wind-sensing system, and a ground-based Doppler radar. The success of the airborne lidar system will be determined by its correlation with the windfield as indicated by the onboard reactive system, which indicates the winds actually experienced by the NASA Boeing 737 aircraft.

  17. Excited waves in shear layers

    NASA Technical Reports Server (NTRS)

    Bechert, D. W.

    1982-01-01

    The generation of instability waves in free shear layers is investigated. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. The acoustical shear layer excitation by a source further away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. The theory is then extended to two streams on both sides of the shear layer having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. A reference quantity is found for the magnitude of the excited instability waves. For a comparison with measurements, numerical computations of the velocity field outside the shear layer were carried out.

  18. Magnetic energy flow in the solar wind.

    NASA Technical Reports Server (NTRS)

    Modisette, J. L.

    1972-01-01

    Discussion of the effect of rotation (tangential flow) of the solar wind on the conclusions of Whang (1971) suggesting an increase in the solar wind velocity due to the conversion of magnetic energy to kinetic energy. It is shown that the effect of the rotation of the sun on the magnetic energy flow results in most of the magnetic energy being transported by magnetic shear stress near the sun.

  19. Shear viscosity of nuclear matter

    E-print Network

    Jun Xu

    2013-02-01

    In this talk I report my recent study on the shear viscosity of neutron-rich nuclear matter from a relaxation time approach. An isospin- and momentum-dependent interaction is used in the study. Effects of density, temperature, and isospin asymmetry of nuclear matter on its shear viscosity have been discussed. Similar to the symmetry energy, the symmetry shear viscosity is defined and its density and temperature dependence are studied.

  20. True Shear Parallel Plate Viscometer

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin; Kaukler, William

    2010-01-01

    This viscometer (which can also be used as a rheometer) is designed for use with liquids over a large temperature range. The device consists of horizontally disposed, similarly sized, parallel plates with a precisely known gap. The lower plate is driven laterally with a motor to apply shear to the liquid in the gap. The upper plate is freely suspended from a double-arm pendulum with a sufficiently long radius to reduce height variations during the swing to negligible levels. A sensitive load cell measures the shear force applied by the liquid to the upper plate. Viscosity is measured by taking the ratio of shear stress to shear rate.

  1. Wind turbine wake detection with a single Doppler wind lidar

    NASA Astrophysics Data System (ADS)

    Wang, H.; Barthelmie, R. J.

    2015-06-01

    Using scanning lidar wind turbine wakes can be probed in three dimensions to produce a wealth of temporally and spatially irregular data that can be used to characterize the wakes. Unlike data from a meteorological mast or upward pointing lidar, the spatial coordinates of the measurements are not fixed and the location of the wake also varies in three dimensions. Therefore the challenge is to provide automated detection algorithms to identify wakes and quantify wake characteristics from this type of dataset. Here an algorithm is developed and evaluated on data from a large wind farm in the Midwest. A scanning coherent Doppler wind lidar was configured to measure wind speed in the wake of a continuously yawing wind turbine for two days during the experiment and wake profiles were retrieved with input of wind direction information from the nearby meteorological mast. Additional challenges to the analysis include incomplete coverage of the entire wake due to the limited scanning domain, and large wind shear that can contaminate the wake estimate because of the height variation along the line-of-sight. However, the algorithm developed in this paper is able to automatically capture wakes in lidar data from Plan Position Indicator (PPI) scans and the resultant wake statistics are consistent with previous experiment's results.

  2. Electrostatic Solitary Waves in the Solar Wind: Evidence for Instability at Solar Wind Current Sheets

    NASA Technical Reports Server (NTRS)

    Malaspina, David M.; Newman, David L.; Wilson, Lynn Bruce; Goetz, Keith; Kellogg, Paul J.; Kerstin, Kris

    2013-01-01

    A strong spatial association between bipolar electrostatic solitary waves (ESWs) and magnetic current sheets (CSs) in the solar wind is reported here for the first time. This association requires that the plasma instabilities (e.g., Buneman, electron two stream) which generate ESWs are preferentially localized to solar wind CSs. Distributions of CS properties (including shear angle, thickness, solar wind speed, and vector magnetic field change) are examined for differences between CSs associated with ESWs and randomly chosen CSs. Possible mechanisms for producing ESW-generating instabilities at solar wind CSs are considered, including magnetic reconnection.

  3. The role of shear in the transition from continuous shear thickening to discontinuous shear thickening

    NASA Astrophysics Data System (ADS)

    Jiang, Weifeng; Xuan, Shouhu; Gong, Xinglong

    2015-04-01

    Dense non-Brownian suspension has rich rheology and is hard to understand, especially for distinguishing continuous shear thickening (CST) from discontinuous shear thickening (DST). By studying the shear stress dependent rheology of a well-known DST suspension of cornstarch in water, we find that the transition from CST to DST could occur not only by increasing the volume fraction ? but also by increasing the shear stress ?. For the recovery process of jammed suspension, we observe that the shear activates the time-dependent nature of particle rearrangement. DST can then be interpreted as the consequence of shear-induced jamming. Based on the test data, we plot the schematic phase diagram in the ?-? plane and find out that ? and ? perform almost the same effect on flow-state transition.

  4. A wake detector for wind farm control

    NASA Astrophysics Data System (ADS)

    Bottasso, C. L.; Cacciola, S.; Schreiber, J.

    2015-06-01

    The paper describes an observer capable of detecting the impingement on a wind turbine rotor of the wake of an upstream machine. The observer estimates the local wind speed and turbulence intensity on the left and right parts of the rotor disk. The estimation is performed based on blade loads measured by strain gages or optical fibers, sensors which are becoming standard equipment on many modern machines. A lower wind speed and higher turbulence intensity on one part of the rotor, possibly in conjunction with other information, can then be used to infer the presence of a wake impinging on the disk. The wake state information is useful for wind plant control strategies, as for example wake deflection by active yawing. In addition, the local wind speed estimates may be used for a rough evaluation of the vertical wind shear.

  5. Wind Turbine

    USGS Multimedia Gallery

    The species of bats that are most susceptible to wind turbines all roost in trees throughout the year, leading some scientists to speculate that they may be visually mistaking wind turbines for trees in which to roost....

  6. Strongly sheared stratocumulus convection: an observationally based large-eddy simulation study

    NASA Astrophysics Data System (ADS)

    Wang, S.; Zheng, X.; Jiang, Q.

    2012-06-01

    Unusually large wind shears across the inversion in the stratocumulus-topped marine boundary layer (MBL) were frequently observed during VOCALS-REx. To investigate the impact of wind shear on the MBL turbulence structure, a large-eddy simulation (LES) model is used to simulate the strongly sheared MBL observed from Twin-Otter RF 18 on 13 November 2008. The LES simulated turbulence statistics agree in general with those derived from the measurements, with the MBL exhibiting a decoupled structure characterized by an enhanced entrainment and a turbulence intensity minimum just below the clouds. Sensitivity simulations show that the shear forcing tends to reduce the dynamic stability of the inversion, characterized by the bulk (or gradient) Richardson number. This decrease enhances the entrainment mixing, leading to reduced cloud water. Consequently, the turbulence intensity in the MBL is significantly weakened by the intense wind shear. The inversion thickens considerably and the MBL top separates from the cloud top, creating a finite cloud-free sublayer of 10-50 m thickness within the inversion, depending on the Richardson number. The weakened inversion tends to enhance the turbulence buoyant consumption and simultaneously lead to a reduced buoyant production in the cloud layer due to less radiative cooling. These effects may result in a decoupling process that creates the different heating/moistening rates between the cloud and subcloud layer, leading to a two-layered structure in the strongly sheared stratocumulus-topped MBL.

  7. Investigation of aircraft landing in variable wind fields

    NASA Technical Reports Server (NTRS)

    Frost, W.; Reddy, K. R.

    1978-01-01

    A digital simulation study is reported of the effects of gusts and wind shear on the approach and landing of aircraft. The gusts and wind shear are primarily those associated with wind fields created by surface wind passing around bluff geometries characteristic of buildings. Also, flight through a simple model of a thunderstorm is investigated. A two-dimensional model of aircraft motion was represented by a set of nonlinear equations which accounted for both spatial and temporal variations of winds. The landings of aircraft with the characteristics of a DC-8 and a DHC-6 were digitally simulated under different wind conditions with fixed and automatic controls. The resulting deviations in touchdown points and the controls that are required to maintain the desired flight path are presented. The presence of large bluff objects, such as buildings in the flight path is shown to have considerable effect on aircraft landings.

  8. Near-inertial kinetic energy budget of the mixed layer and shear evolution in the transition layer in the Arabian Sea during the monsoons

    NASA Astrophysics Data System (ADS)

    Majumder, Sudip; Tandon, Amit; Rudnick, Daniel L.; Thomas Farrar, J.

    2015-09-01

    We present the horizontal kinetic energy (KE) balance of near-inertial currents in the mixed layer and explain shear evolution in the transition layer using observations from a mooring at 15.26° N in the Arabian Sea during the southwest monsoon. The highly sheared and stratified transition layer at the mixed-layer base varies between 5 m and 35 m and correlates negatively with the wind stress. Results from the mixed layer near-inertial KE (NIKE) balance suggest that wind energy at times can energize the transition layer and at other times is fully utilized within the mixed layer. A simple two layer model is utilized to study the shear evolution in the transition layer and shown to match well with observations. The shear production in this model arises from alignment of wind stress and shear. Although the winds are unidirectional during the monsoon, the shear in the transition layer is predominantly near-inertial. The near-inertial shear bursts in the observations show the same phasing and magnitude at near-inertial frequencies as the wind-shear alignment term.

  9. Field Wind Tunnel Testing of Two Silt Loam Soils on the North American Central High Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind erosion is a natural process of sediment redistribution resulting from the shear force of the wind interacting with unprotected soil surfaces. Globally, wind erosion accounts for nearly half of all soil loss. Breaking of the prairie sod and mechanical tillage of agricultural soils on the semi...

  10. Shear Viscosity and Shear Thinning in Two-Dimensional Yukawa Liquids Z. Donko,1

    E-print Network

    Goree, John

    Shear Viscosity and Shear Thinning in Two-Dimensional Yukawa Liquids Z. Donko´,1 J. Goree,2 P nonequilibrium molecular dynamics simulation methods. Shear viscosity values in the limit of small shear rates it is demonstrated that this liquid exhibits shear thinning; i.e., the viscosity diminishes with increasing shear

  11. Generation of Large-Scale Winds in Horizontally Anisotropic Convection.

    PubMed

    von Hardenberg, J; Goluskin, D; Provenzale, A; Spiegel, E A

    2015-09-25

    We simulate three-dimensional, horizontally periodic Rayleigh-Bénard convection, confined between free-slip horizontal plates and rotating about a distant horizontal axis. When both the temperature difference between the plates and the rotation rate are sufficiently large, a strong horizontal wind is generated that is perpendicular to both the rotation vector and the gravity vector. The wind is turbulent, large-scale, and vertically sheared. Horizontal anisotropy, engendered here by rotation, appears necessary for such wind generation. Most of the kinetic energy of the flow resides in the wind, and the vertical turbulent heat flux is much lower on average than when there is no wind. PMID:26451558

  12. Solar wind

    NASA Astrophysics Data System (ADS)

    Marsch, E.; Axford, W. I.; McKenzie, J. F.

    There are three major types of solar wind - the steady fast wind, the unsteady slow wind, and the variable transient wind. The fast streams are the normal modes of the solar wind. Their basic properties can be reproduced by multi-fluid models involving waves. After briefly reviewing the history of the subject and describing some of the modern theories of the fast wind, the boundary conditions and in-situ constraints are discussed which are imposed on the models, in particular by Ulysses at high latitudes. Some of the results are then presented from SOHO observations that have brought a wealth of new information on the state of the wind in the inner corona as well as the plasma source conditions prevailing in the transition region and solar chromosphere. Finally, problem areas are identified and future research perspectives are outlined.

  13. Mechanical properties of graphene under shear deformation

    NASA Astrophysics Data System (ADS)

    Min, K.; Aluru, N. R.

    2011-01-01

    In this letter, we investigate the mechanical properties of graphene under shear deformation. Specifically, using molecular dynamics simulations, we compute the shear modulus, shear fracture strength, and shear fracture strain of zigzag and armchair graphene structures at various temperatures. To predict shear strength and fracture shear strain, we also present an analytical theory based on the kinetic analysis. We show that wrinkling behavior of graphene under shear deformation can be significant. We compute the amplitude to wavelength ratio of wrinkles using molecular dynamics and compare it with existing theory. Our results indicate that graphene can be a promising mechanical material under shear deformation.

  14. Smectic Edge Dislocations under Shear

    NASA Astrophysics Data System (ADS)

    Chen, Peilong; Lu, Chun-Yi David

    2011-09-01

    Layer structures around an edge dislocation in a smectic phase under shear are studied with both phase field and order parameter models. It is shown that, contrast to a crystal solid, the conventional picture of the Peach--Koehler force experienced by dislocations when the sample is under a shear stress cannot be readily applied to the smectic phases. Under a uniform shear flow, we obtain the phase field and order parameter solutions around an edge dislocation. The solutions elucidate properties such as the layer distortion range around the dislocation and scaling of inter-dislocation interaction on dislocation separation. Calculations on energy dissipation indicate the extreme shear-thinning behavior that an edge dislocation induces a shear stress independent of the shear rate. Finally in a bulk sample with dislocation forming loops and networks, we argue that the uniform flow component around the dislocation is important to the energy dissipation and we show that its scaling exponent with the shear rate is very close to results from many previous rheology measurements.

  15. Macroscopic Discontinuous Shear Thickening vs Local Shear Jamming in Cornstarch

    E-print Network

    A. Fall; F. Bertrand; D. Hautemayou; C. Mezière; P. Moucheront; A. Lemaître; G. Ovarlez

    2015-01-22

    We study the emergence of discontinuous shear-thickening (DST) in cornstarch, by combining macroscopic rheometry with local Magnetic Resonance Imaging (MRI) measurements. We bring evidence that macroscopic DST is observed only when the flow separates into a low-density flowing and a high-density jammed region. In the shear-thickened steady state, the local rheology in the flowing region, is not DST but, strikingly, is often shear-thinning. Our data thus show that the stress jump measured during DST, in cornstach, does not capture a secondary, high-viscosity branch of the local steady rheology, but results from the existence of a shear jamming limit at volume fractions quite significantly below random close packing.

  16. Macroscopic Discontinuous Shear Thickening versus Local Shear Jamming in Cornstarch

    NASA Astrophysics Data System (ADS)

    Fall, A.; Bertrand, F.; Hautemayou, D.; Mezière, C.; Moucheront, P.; Lemaître, A.; Ovarlez, G.

    2015-03-01

    We study the emergence of discontinuous shear thickening (DST) in cornstarch by combining macroscopic rheometry with local magnetic resonance imaging measurements. We bring evidence that macroscopic DST is observed only when the flow separates into a low-density flowing and a high-density jammed region. In the shear-thickened steady state, the local rheology in the flowing region is not DST but, strikingly, is often shear thinning. Our data thus show that the stress jump measured during DST, in cornstarch, does not capture a secondary, high-viscosity branch of the local steady rheology but results from the existence of a shear jamming limit at volume fractions quite significantly below random close packing.

  17. Macroscopic discontinuous shear thickening versus local shear jamming in cornstarch.

    PubMed

    Fall, A; Bertrand, F; Hautemayou, D; Mezière, C; Moucheront, P; Lemaître, A; Ovarlez, G

    2015-03-01

    We study the emergence of discontinuous shear thickening (DST) in cornstarch by combining macroscopic rheometry with local magnetic resonance imaging measurements. We bring evidence that macroscopic DST is observed only when the flow separates into a low-density flowing and a high-density jammed region. In the shear-thickened steady state, the local rheology in the flowing region is not DST but, strikingly, is often shear thinning. Our data thus show that the stress jump measured during DST, in cornstarch, does not capture a secondary, high-viscosity branch of the local steady rheology but results from the existence of a shear jamming limit at volume fractions quite significantly below random close packing. PMID:25793857

  18. Stellar Winds Geoffrey V. Bicknell Stellar Winds

    E-print Network

    Bicknell, Geoff

    Stellar Winds © Geoffrey V. Bicknell Stellar Winds vw Star #12;Astrophysical Gas Dynamics: Stellar Winds 2/66 1 Characteristics of stellar winds Solar wind Velocity at earth's orbit: (1) Density: (2: Stellar Winds 3/66 Mass flux (spherically symmetric wind): (5) Other stars Red giants: O&B type stars

  19. Structure of Highly Sheared Tropical Storm Chantal during CAMEX-4

    NASA Technical Reports Server (NTRS)

    Heymsfield, G. M.; Halverson, J.; Ritchie, E.; Simpson, Joanne; Molinari, J.; Tian, L.

    2006-01-01

    Tropical Storm Chantal during August 2001 was a storm that failed to intensify over the few days prior to making landfall on the Yucatan Peninsula. An observational study of Tropical Storm Chantal is presented using a diverse dataset including remote and in situ measurements from the NASA ER-2 and DC-8 and the NOAA WP-3D N42RF aircraft and satellite. The authors discuss the storm structure from the larger-scale environment down to the convective scale. Large vertical shear (850-200-hPa shear magnitude range 8-15 m/s) plays a very important role in preventing Chantal from intensifying. The storm had a poorly defined vortex that only extended up to 5-6-km altitude, and an adjacent intense convective region that comprised a mesoscale convective system (MCS). The entire low-level circulation center was in the rain-free western side of the storm, about 80 km to the west-southwest of the MCS. The MCS appears to have been primarily the result of intense convergence between large-scale, low-level easterly flow with embedded downdrafts, and the cyclonic vortex flow. The individual cells in the MCS such as cell 2 during the period of the observations were extremely intense, with reflectivity core diameters of 10 km and peak updrafts exceeding 20 m/s. Associated with this MCS were two broad subsidence (warm) regions, both of which had portions over the vortex. The first layer near 700 hPa was directly above the vortex and covered most of it. The second layer near 500 hPa was along the forward and right flanks of cell 2 and undercut the anvil divergence region above. There was not much resemblance of these subsidence layers to typical upper-level warm cores in hurricanes that are necessary to support strong surface winds and a low central pressure. The observations are compared to previous studies of weakly sheared storms and modeling studies of shear effects and intensification. The configuration of the convective updrafts, low-level circulation, and lack of vertical coherence between the upper- and lower-level warming regions likely inhibited intensification of Chantal. This configuration is consistent with modeled vortices in sheared environments, which suggest the strongest convection and rain in the downshear left quadrant of the storm, and subsidence in the upshear right quadrant. The vertical shear profile is, however, different from what was assumed in previous modeling in that the winds are strongest in the lowest levels and the deep tropospheric vertical shear is on the order of 10-12 m/s.

  20. Signal processing techniques for clutter filtering and wind shear detection

    NASA Technical Reports Server (NTRS)

    Baxa, Ernest G., Jr.; Deshpande, Manohar D

    1991-01-01

    An extended Prony algorithm applicable to signal processing techniques for clutter filtering and windshear detection is discussed. The algorithm is based upon modelling the radar return as a time series, and appears to offer potential for improving hazard factor estimates in the presence of strong clutter returns.

  1. Shear shocks in fragile networks.

    PubMed

    Ulrich, Stephan; Upadhyaya, Nitin; van Opheusden, Bas; Vitelli, Vincenzo

    2013-12-24

    A minimal model for studying the mechanical properties of amorphous solids is a disordered network of point masses connected by unbreakable springs. At a critical value of its mean connectivity, such a network becomes fragile: it undergoes a rigidity transition signaled by a vanishing shear modulus and transverse sound speed. We investigate analytically and numerically the linear and nonlinear visco-elastic response of these fragile solids by probing how shear fronts propagate through them. Our approach, which we tentatively label shear front rheology, provides an alternative route to standard oscillatory rheology. In the linear regime, we observe at late times a diffusive broadening of the fronts controlled by an effective shear viscosity that diverges at the critical point. No matter how small the microscopic coefficient of dissipation, strongly disordered networks behave as if they were overdamped because energy is irreversibly leaked into diverging nonaffine fluctuations. Close to the transition, the regime of linear response becomes vanishingly small: the tiniest shear strains generate strongly nonlinear shear shock waves qualitatively different from their compressional counterparts in granular media. The inherent nonlinearities trigger an energy cascade from low to high frequency components that keep the network away from attaining the quasi-static limit. This mechanism, reminiscent of acoustic turbulence, causes a superdiffusive broadening of the shock width. PMID:24309379

  2. Shear shocks in fragile networks

    PubMed Central

    Ulrich, Stephan; Upadhyaya, Nitin; van Opheusden, Bas; Vitelli, Vincenzo

    2013-01-01

    A minimal model for studying the mechanical properties of amorphous solids is a disordered network of point masses connected by unbreakable springs. At a critical value of its mean connectivity, such a network becomes fragile: it undergoes a rigidity transition signaled by a vanishing shear modulus and transverse sound speed. We investigate analytically and numerically the linear and nonlinear visco-elastic response of these fragile solids by probing how shear fronts propagate through them. Our approach, which we tentatively label shear front rheology, provides an alternative route to standard oscillatory rheology. In the linear regime, we observe at late times a diffusive broadening of the fronts controlled by an effective shear viscosity that diverges at the critical point. No matter how small the microscopic coefficient of dissipation, strongly disordered networks behave as if they were overdamped because energy is irreversibly leaked into diverging nonaffine fluctuations. Close to the transition, the regime of linear response becomes vanishingly small: the tiniest shear strains generate strongly nonlinear shear shock waves qualitatively different from their compressional counterparts in granular media. The inherent nonlinearities trigger an energy cascade from low to high frequency components that keep the network away from attaining the quasi-static limit. This mechanism, reminiscent of acoustic turbulence, causes a superdiffusive broadening of the shock width. PMID:24309379

  3. Low-altitude wind measurements from wide-body jet transports

    NASA Technical Reports Server (NTRS)

    Dunham, R. E., Jr.

    1982-01-01

    For a 2-week period in the spring of 1977, data were collected onboard wide-body jet transports for the determination of winds and wind shear during landings and take-offs. The data represent about 640 take-offs or landings at 14 airports in Europe and the United States. Analysis of the wind-shear data indicates that shears of a given value are equally likely to occur at any altitude in the lower 1400-ft section of the atmosphere. Analysis of the data indicates that low shears (plus or minus .033 knot/per ft) have a 67-percent chance of occurrence during a landing or take-off, while higher values (plus or minus 0.15 knot/per ft) have a 0.5-percent chance of occurrence. A determination of the duration of a given shear was not made.

  4. Infrasonic wind noise under a deciduous tree canopy.

    PubMed

    Webster, Jeremy; Raspet, Richard

    2015-05-01

    In a recent paper, the infrasonic wind noise measured at the floor of a pine forest was predicted from the measured wind velocity spectrum and profile within and above the trees [Raspet and Webster, J. Acoust. Soc. Am. 137, 651-659 (2015)]. This research studies the measured and predicted wind noise under a deciduous forest with and without leaves. A calculation of the turbulence-shear interaction pressures above the canopy predicts the low frequency peak in the wind noise spectrum. The calculated turbulence-turbulence interaction pressure due to the turbulence field near the ground predicts the measured wind noise spectrum in the higher frequency region. The low frequency peak displays little dependence on whether the trees have leaves or not. The high frequency contribution with leaves is approximately an order of magnitude smaller than the contribution without leaves. Wind noise levels with leaves are very similar to the wind noise levels in the pine forest. The calculated turbulence-shear contribution from the wind within the canopy is shown to be negligible in comparison to the turbulence-turbulence contribution in both cases. In addition, the effect of taller forests and smaller roughness lengths than those of the test forest on the turbulence-shear interaction is simulated based on measured meteorological parameters. PMID:25994698

  5. Wind Tunnel 

    E-print Network

    Unknown

    2011-08-17

    Simulation of Cooling Effect of Wind Tower on Passively Ventilated Building John Seryak Kelly Kissock Project Engineer Associate Professor Department of Mechanical and Aerospace Engineering University of Dayton... Dayton, Ohio ABSTRACT Traditional buildings are cooled and ventilated by mechanically induced drafts. Natural ventilation aspires to cool and ventilate a building by natural means, such as cross ventilation or wind towers, without mechanical...

  6. Meteorology (Wind)

    Atmospheric Science Data Center

    2014-09-25

    ... is in each range (0-2, 3-6, 7-10, 11-14, 15-18, 19-25 m/s).   Wind Speed at 50 m at 3-hourly intervals (m/s)   ... be adjusted to heights from 10 to 300 meters using the Gipe power law. Wind speeds may be adjusted for different terrain by selecting from ...

  7. Wind energy.

    PubMed

    Leithead, W E

    2007-04-15

    From its rebirth in the early 1980s, the rate of development of wind energy has been dramatic. Today, other than hydropower, it is the most important of the renewable sources of power. The UK Government and the EU Commission have adopted targets for renewable energy generation of 10 and 12% of consumption, respectively. Much of this, by necessity, must be met by wind energy. The US Department of Energy has set a goal of 6% of electricity supply from wind energy by 2020. For this potential to be fully realized, several aspects, related to public acceptance, and technical issues, related to the expected increase in penetration on the electricity network and the current drive towards larger wind turbines, need to be resolved. Nevertheless, these challenges will be met and wind energy will, very likely, become increasingly important over the next two decades. An overview of the technology is presented. PMID:17272245

  8. The effect of shear on heat budgets in a simulated Mesoscale Convective System 

    E-print Network

    Shaw, Justin David

    2000-01-01

    in the lowest 2.5 km varying from 10-25 m s?¹. A fourth simulation was conducted using the weak wind shear profile and incorporating ice microphysics. An analysis domain was produced every two hours for the northern and southern portions of the convective line...

  9. Evolution of a barotropic shear layer into elliptical vortices.

    PubMed

    Guha, Anirban; Rahmani, Mona; Lawrence, Gregory A

    2013-01-01

    When a barotropic shear layer becomes unstable, it produces the well-known Kelvin-Helmholtz instability (KHI). The nonlinear manifestation of the KHI is usually in the form of spiral billows. However, a piecewise linear shear layer produces a different type of KHI characterized by elliptical vortices of constant vorticity connected via thin braids. Using direct numerical simulation and contour dynamics, we show that the interaction between two counterpropagating vorticity waves is solely responsible for this KHI formation. We investigate the oscillation of the vorticity wave amplitude, the rotation and nutation of the elliptical vortex, and straining of the braids. Our analysis also provides a possible explanation for the formation and evolution of elliptical vortices appearing in geophysical and astrophysical flows, e.g., meddies, stratospheric polar vortices, Jovian vortices, Neptune's Great Dark Spot, and coherent vortices in the wind belts of Uranus. PMID:23410439

  10. Structure of the dayside magnetopause for low magnetic shear

    SciTech Connect

    Paschmann, G.; Baumjohann, W.; Sckopke, N.; Phan, T.D.; Luehr, H.

    1993-08-01

    The authors report a study of 22 magnetopause crossings made by AMPTE/IRM at locations where the magnetic shear was less than 30{degrees}. Such crossings are more difficult to identify because the lack of a large magnetic shear removes the most obvious signature of the magnetopause. The authors finds that in all passes they were able to observe at some time a point where the proton temperature, and perhaps also the electron temperature and temperature anisotropies, undergo a discontinuous change. Plasma flow directions usually change at this point also. They discuss typical plasma properties both outboard and on the magnetosphere side of the magnetopause, and indications of solar wind penetration of the magnetopause even in instances where there is no obvious reconnection observed.

  11. Minimal model for chaotic shear banding in shear thickening fluids.

    PubMed

    Aradian, A; Cates, M E

    2006-04-01

    We present a minimal model for spatiotemporal oscillation and rheochaos in shear thickening complex fluids at zero Reynolds number. In the model, a tendency towards inhomogeneous flows in the form of shear bands combines with a slow structural dynamics, modeled by delayed stress relaxation. Using Fourier-space numerics, we study the nonequilibrium "phase diagram" of the fluid as a function of a steady mean (spatially averaged) stress, and of the relaxation time for structural relaxation. We find several distinct regions of periodic behavior (oscillating bands, traveling bands, and more complex oscillations) and also regions of spatiotemporal rheochaos. A low-dimensional truncation of the model retains the important physical features of the full model (including rheochaos) despite the suppression of sharply defined interfaces between shear bands. Our model maps onto the FitzHugh-Nagumo model for neural network dynamics, with an unusual form of long-range coupling. PMID:16711810

  12. The many faces of the Shear Alfvén Wave

    NASA Astrophysics Data System (ADS)

    Gekelman, Walter

    2010-11-01

    One of the fundamental waves in a magnetized plasma is the shear Alfvén wave. This wave is responsible for rearranging current systems and, in fact, all low frequency currents (f< fci) are shear waves. It has become apparent that Alfvén waves are important in a wide variety of physical environments. They play a central role in the stability of magnetic confinement devices, give rise to aurora formation in planets, and are thought to contribute to heating and ion acceleration in the solar corona. Shear waves of finite transverse scale have electric fields parallel to the local background magnetic field, which is key to understanding current systems, and they can also cause particle acceleration over considerable distances in interstellar space. One may also consider magnetic flux ropes as low frequency shear waves. Shear waves can become nonlinear and in astrophysical environments this is proposed to result in turbulent cascades and the generation of structures. Measurements on board the Polar satellite indicate that the power of earthward bound shear waves equals that of the auroral electron beam. Alfvén waves have been directly observed in the solar wind, the auroral ionosphere and magnetotail, in the sun's corona, and in fusion devices. Currently there is much interest in the properties of toroidal Alfvén eigenmodes in tokamaks because they can be triggered by resonant alpha particles and thus could negatively affect particle confinement if they were to grow to large amplitudes. Shear waves of various forms have been a topic of experimental research for more than fifteen years in the Large Plasma Device (LAPD) at UCLA. The waves were first studied in both the kinetic and inertial regimes when excited by fluctuating currents with transverse dimension on the order of the collisionless skin depth c?pe . The three dimensional currents associated with the waves have been mapped and the ion motion which closes the currents across the magnetic field observed with laser induced fluorescence. The propagation in inhomogeneous magnetic fields and density gradients has been studied as well as effects of collisions and reflections from boundaries. Heating of the plasma electrons and ions has also been observed. The waves have been launched with antennas, but have also been generated by secondary processes such as mode conversion of microwaves at the upper hybrid layer followed by Cherenkov radiation by fast electrons. They are also produced by an exploding laser produced plasma in a background magnetoplasma. Magnetic field line reconnection has been observed when Alfvénic current systems interact. Flux ropes as well as temperature filaments also exhibit shear wave phenomena. Three-dimensional data illustrating these processes will be presented along with relevant theory. Part of the presentation will be in 3D!

  13. Lagrangian Coherent Structure Analysis of Terminal Winds Detected by Lidar. Part II: Structure Evolution and Comparison with Flight Data

    E-print Network

    Tang, Wenbo

    Lagrangian Coherent Structure Analysis of Terminal Winds Detected by Lidar. Part II: Structure and compare them with onboard wind shear and altitude data collected during airplane approaches. Their results Lyapunov exponent (FDFTLE) method from Tang et al. (2010) to two-dimensional horizontal wind fields

  14. Structural Aspects of Railway Truss Bridges Affecting Transverse Shear Forces in Steel-Concrete Composite Decks

    NASA Astrophysics Data System (ADS)

    Siekierski, Wojciech

    2015-03-01

    At the steel-concrete interface, the horizontal shear forces that are transverse to cross beams occur due to joint action of the steel-concrete composite deck and the truss girders. Numerical analysis showed that values of the forces are big in comparison to the longitudinal shear forces. In both cases extreme force values occur near side edges of a slab. The paper studies possibilities of reduction of these shear forces by structural alterations of the following: rigidity of a concrete slab, arrangement of a wind bracing, arrangement of concrete slab expansion joints. An existing railway truss bridge span has been analysed. Numerical analysis shows that it is possible to reduce the values of shear forces transverse to cross beams. It may reach 20% near the side edges of slabs and 23% in the centre of slab width.

  15. Wind Monitoring Report for Fort Wainwright's Donnelly Training Area

    SciTech Connect

    Orrell, Alice C.; Dixon, Douglas R.

    2011-01-18

    Using the wind data collected at a location in Fort Wainwright’s Donnelly Training Area (DTA) near the Cold Regions Test Center (CRTC) test track, Pacific Northwest National Laboratory (PNNL) estimated the gross and net energy productions that proposed turbine models would have produced exposed to the wind resource measured at the meteorological tower (met tower) location during the year of measurement. Calculations are based on the proposed turbine models’ standard atmospheric conditions power curves, the annual average wind speeds, wind shear estimates, and standard industry assumptions.

  16. Wind profile estimation from point to point laser distortion data

    NASA Technical Reports Server (NTRS)

    Leland, Robert

    1989-01-01

    The author's results on the problem of using laser distortion data to estimate the wind profile along the path of the beam are presented. A new model for the dynamics of the index of refraction in a non-constant wind is developed. The model agrees qualitatively with theoretical predictions for the index of refraction statistics in linear wind shear, and is approximated by the predictions of Taylor's hypothesis in constant wind. A framework for a potential in-flight experiment is presented, and the estimation problem is discussed in a maximum likelihood context.

  17. Stellar Winds

    NASA Astrophysics Data System (ADS)

    Owocki, Stan

    A "stellar wind" is the continuous, supersonic outflow of matter from the surface layers of a star. Our sun has a solar wind, driven by the gas-pressure expansion of the hot (T > 106 K) solar corona. It can be studied through direct in situ measurement by interplanetary spacecraft; but analogous coronal winds in more distant solar-type stars are so tenuous and transparent that that they are difficult to detect directly. Many more luminous stars have winds that are dense enough to be opaque at certain wavelengths of the star's radiation, making it possible to study their wind outflows remotely through careful interpretation of the observed stellar spectra. Red giant stars show slow, dense winds that may be driven by the pressure from magnetohydrodyanmic waves. As stars with initial mass up to 8 M ? evolve toward the Asymptotic Giant Branch (AGB), a combination of stellar pulsations and radiative scattering off dust can culminate in "superwinds" that strip away the entire stellar envelope, leaving behind a hot white dwarf stellar core with less than the Chandrasekhar mass of ˜ ?? 1. 4M ?. The winds of hot, luminous, massive stars are driven by line-scattering of stellar radiation, but such massive stars can also exhibit superwind episodes, either as Red Supergiants or Luminous Blue Variable stars. The combined wind and superwind mass loss can strip the star's hydrogen envelope, leaving behind a Wolf-Rayet star composed of the products of earlier nuclear burning via the CNO cycle. In addition to such direct effects on a star's own evolution, stellar winds can be a substantial source of mass, momentum, and energy to the interstellar medium, blowing open large cavities or "bubbles" in this ISM, seeding it with nuclear processed material, and even helping trigger the formation of new stars, and influencing their eventual fate as white dwarves or core-collapse supernovae. This chapter reviews the properties of such stellar winds, with an emphasis on the various dynamical driving processes and what they imply for key wind parameters like the wind flow speed and mass loss rate.

  18. High shear rate characterization of magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Becnel, Andrew C.; Hu, Wei; Wereley, Norman M.

    2012-04-01

    Shear mode or rotary drum-type magnetorheological energy absorbers (MREAS) are an attractive option for use in occupant or payload protection systems that operate at shear rates well over 25,000 s-1. However, their design is still performed using material properties measured using low-shear rate (<1,000 s-1) characterization techniques. This paper details a method for characterizing MR fluids at high shear rates, and presents characterization results for three commercially available MR fluids. It is proposed to utilize the perspective of apparent viscosity (the ratio of shear stress over shear rate) vs. shear rate to describe the behavior of the fluid at these shear rates. Good agreement between the measured data and predictions of MR fluid behavior are achieved using this framework. By expanding the knowledge of MR fluid behavior to these high shear strain rates, the design of MREAs is enabled for occupant protection systems for crash and mine blast events.

  19. Effects of Changing Atmospheric Conditions on Wind Turbine Performance (Poster)

    SciTech Connect

    Clifton, A.

    2012-12-01

    Multi-megawatt, utility-scale wind turbines operate in turbulent and dynamic winds that impact turbine performance in ways that are gradually becoming better understood. This poster presents a study made using a turbulent flow field simulator (TurbSim) and a Turbine aeroelastic simulator (FAST) of the response of a generic 1.5 MW wind turbine to changing inflow. The turbine power output is found to be most sensitive to wind speed and turbulence intensity, but the relationship depends on the wind speed with respect to the turbine's rated wind speed. Shear is found to be poorly correlated to power. A machine learning method called 'regression trees' is used to create a simple model of turbine performance that could be used as part of the wind resource assessment process. This study has used simple flow fields and should be extended to more complex flows, and validated with field observations.

  20. 78 FR 29364 - Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-20

    ...-005, QF07-257-004] Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4, LLC, Exelon Wind 5, LLC, Exelon Wind 6, LLC, Exelon Wind 7, LLC, Exelon Wind 8, LLC, Exelon Wind 9, LLC, Exelon Wind 10, LLC, Exelon Wind 11, LLC, High Plains Wind Power, LLC v. Xcel...

  1. Shear Relaxations of Confined Liquids.

    NASA Astrophysics Data System (ADS)

    Carson, George Amos, Jr.

    Ultrathin (<40 A) films of octamethylcyclotetrasiloxane (OMCTS), hexadecane, and dodecane were subjected to linear and non-linear oscillatory shear between flat plates. Shearing frequencies of 0.1 to 800 s^{-1} were applied at pressures from zero to 0.8 MPa using a surface rheometer only recently developed. In most cases the plates were atomically smooth mica surfaces; the role of surface interactions was examined by replacing these with alkyl chain monolayers. OMCTS and hexadecane were examined at a temperature about 5 Celsius degrees above their melting points and tended to solidify. Newtonian plateaus having enormous viscosities were observed at low shear rates. The onset of shear thinning implied relaxation times of about 0.1 s in the linear structure of the confined liquids. Large activation volumes (~80 nm ^3) suggested that shear involved large-scale collective motion. Dodecane was studied at a much higher temperature relative to its melting point and showed no signs of impending solidification though it exhibited well-defined regions of Newtonian response and power law shear thinning. When treated with molecular sieves before use, dodecane had relaxation times which were short (0.02 s) compared to hexadecane, but still exhibited large-scale collective motion. When treated with silica gel, an unexplained long -time relaxation (10 s) was seen in the Newtonian viscosity of dodecane. The relaxation time of the linear structure, 0.005 s was very small, and the storage modulus was unresolvable. The small activation volume (7nm^3) indicated a much lower level of collective motion. The activation volume remained small when dodecane was confined between tightly bound, low energy, alkyl monolayers. At low strains the storage and loss moduli became very large (>10^4 Pa), probably due to interactions with flaws in the monolayers. Dramatic signs of wall slip were observed at large strains even at low pressures.

  2. Filament winding

    NASA Astrophysics Data System (ADS)

    Shibley, A. M.

    The major aspects of filament winding are discussed, emphasizing basic reinforcement and matrix materials, winding procedures, process controls, and cured composite properties. Fiberglass (E-glass and S-glass strengths are 500,000 and 665,000 psi respectively) and polyester resins are the principal reinforcement constituent materials. Graphite and aramid reinforcements are being used more frequently, primarily for the more critical pressure vessels. Matrix systems are most commonly based on epoxy as it has superior mechanical properties, fatigue behavior, and heat resistance as compard with polyesters. A fiberglass overwrap of PVC pipe is an anticipated development in on-site winding and combination winding, and the compression molding of filament wound lay-ups will be investigated. The fabrication of weight-sensitive structural components may be achieved by using such moldings.

  3. Shearing of frictional sphere packings

    NASA Astrophysics Data System (ADS)

    Métayer, J.-F.; Suntrup, D. J., III; Radin, C.; Swinney, H. L.; Schröter, M.

    2011-03-01

    We measure shear response in packings of glass beads by pulling a thin, rough, metal plate vertically through a bed of volume fraction phi, which is set, before the plate is pulled, in the range from 0.575 to 0.628. The yield stress is velocity independent over 4 decades and increases exponentially with phi, with a transition at phi?0.595. An analysis of the measured force fluctuations indicates that the shear modulus is significantly smaller than the bulk modulus.

  4. Shearing of frictional sphere packings

    E-print Network

    Jean-François Métayer; Donald J. Suntrup III; Charles Radin; Harry L. Swinney; Matthias Schröter

    2011-04-19

    We measure shear response in packings of glass beads by pulling a thin, rough, metal plate vertically through a bed of volume fraction phi, which is set, before the plate is pulled, in the range 0.575 to 0.628. The yield stress is velocity independent over 4 decades and increases exponentially with phi, with a transition at phi approximately 0.595. An analysis of the measured force fluctuations indicates that the shear modulus is significantly smaller than the bulk modulus.

  5. Experimental observation of shear thickening oscillation

    E-print Network

    Nagahiro, Shin-ichiro; Mitarai, Namiko

    2012-01-01

    We report experimental observation of the shear thickening oscillation, i.e. the spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluid. The shear thickening oscillation is caused by the interplay between the fluid dynamics and the shear thickening, and has been predicted theoretically by the present authors using a phenomenological fluid dynamics model for the dilatant fluid, but never been reported experimentally. Using a density-matched starch-water mixture, in the cylindrical shear flow of a few centimeters flow width, we observed strong vibrations of the frequency around 20 Hz, which is consistent with our theoretical prediction.

  6. Experimental observation of shear thickening oscillation

    E-print Network

    Shin-ichiro Nagahiro; Hiizu Nakanishi; Namiko Mitarai

    2013-07-10

    We report experimental observation of the shear thickening oscillation, i.e. the spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluid. The shear thickening oscillation is caused by the interplay between the fluid dynamics and the shear thickening, and has been predicted theoretically by the present authors using a phenomenological fluid dynamics model for the dilatant fluid, but never been reported experimentally. Using a density-matched starch-water mixture, in the cylindrical shear flow of a few centimeters flow width, we observed strong vibrations of the frequency around 20 Hz, which is consistent with our theoretical prediction.

  7. A microcomputer program for estimating low altitude wind and turbulence fields

    NASA Technical Reports Server (NTRS)

    Ludwig, F. L.; Lester, Peter

    1991-01-01

    Past efforts to develop methods for objective wind analysis and to provide turbulence estimates to pilots are reviewed. The present approach involves a wind module and a turbulence module. The wind module extends the critical dividing streamline concept and past developments in mass-conserving wind interpolation schemes. The turbulence module is based on recent efforts to develop practical atmospheric turbulence parameterization schemes based on lapse rate, wind shear, surface heating, and surface roughness. The lapse rate and wind shear are readily obtained from the wind module. Surface roughness and heating come from land use information and net radiation estimates derived from cloud cover, terrain slope, local time, and latitude. This system is argued to have considerable potential for providing useful online information for many kinds of aircraft operations.

  8. Influence of refraction on wind turbine noise

    E-print Network

    Makarewicz, Rufin

    2013-01-01

    A semi-empirical method is applied to calculate the time-average sound level of wind turbine noise generation and propagation. Both are affected by wind shear refraction. Under upwind conditions the partially ensonified zone separates the fully ensonified zone (close to the turbine) and the shadow zone (far away from the turbine). Refraction is described in terms of the wind speed linear profile fitted to the power law profile. The rotating blades are treated as a two-dimensional circular source in the vertical plane. Inside the partially ensonified zone the effective A-weighted sound power decreases to zero when the receiver moves from the turbine toward the shadow zone. The presented results would be useful in practical applications to give a quick estimate of the effect of refraction on wind turbine noise.

  9. Recommendations for a wind profiling network to support Space Shuttle launches

    NASA Technical Reports Server (NTRS)

    Zamora, R. J.

    1992-01-01

    The feasibility is examined of a network of clear air radar wind profilers to forecast wind conditions before Space Shuttle launches during winter. Currently, winds are measured only in the vicinity of the shuttle launch site and wind loads on the launch vehicle are estimated using these measurements. Wind conditions upstream of the Cape are not monitored. Since large changes in the wind shear profile can be associated with weather systems moving over the Cape, it may be possible to improve wind forecasts over the launch site if wind measurements are made upstream. A radar wind profiling system is in use at the Space Shuttle launch site. This system can monitor the wind profile continuously. The existing profiler could be combined with a number of radars located upstream of the launch site. Thus, continuous wind measurements would be available upstream and at the Cape. NASA-Marshall representatives have set the requirements for radar wind profiling network. The minimum vertical resolution of the network must be set so that the wind shears over the depths greater than or = 1 km will be detected. The network should allow scientists and engineers to predict the wind profile over the Cape 6 hours before a Space Shuttle launch.

  10. The effect of shearing strain-rate on the ultimate shearing resistance of clay

    NASA Technical Reports Server (NTRS)

    Cheng, R. Y. K.

    1975-01-01

    An approach for investigating the shearing resistance of cohesive soils subjected to a high rate of shearing strain is described. A fast step-loading torque apparatus was used to induce a state of pure shear in a hollow cylindrical soil specimen. The relationship between shearing resistance and rate of shear deformation was established for various soil densities expressed in terms of initial void ratio or water content. For rate of shearing deformation studies, the shearing resistance increases initially with shearing velocity, but subsequently reaches a terminal value as the shearing velocity increases. The terminal shearing resistance is also found to increase as the density of the soil increases. The results of this investigation are useful in the rheological study of clay. It is particularly important for mobility problems of soil runways, since the soil resistance is found to be sensitive to the rate of shearing.

  11. The effect of shearing strain-rate on the ultimate shearing resistance of clay

    NASA Technical Reports Server (NTRS)

    Cheng, R. Y. K.

    1976-01-01

    The shearing resistance of cohesive soils subjected to a high rate of shearing strain was investigated. A fast step-loading torque apparatus was used to induce a state of pure shear in a hollow cylindrical soil specimen. The relationship between shearing resistance and rate of shear deformation was established for various soil densities expressed in terms of initial void ratio or water content. For rate of shearing deformation studies to date, the shearing resistance increases initially with shearing velocity but subsequently reaches a terminal value as the shearing velocity increases. The terminal shearing resistance is also found to increase as the density of the soil increases. The results are useful in the rheological study of clay. It is particularly important for mobility problems of soil runways, since the soil resistance is found to be sensitive to the rate of shearing.

  12. Shear history effect of magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Shan, Lei; Chen, Kaikai; Zhou, Ming; Zhang, Xiangjun; Meng, Yonggang; Tian, Yu

    2015-10-01

    The rheological properties of magnetorheological (MR) fluids are usually determined by particle structures and polarized particle interactions. However, the particle structures may undergo various evolutions at different shear states and history; this evolution leads to shear stress hysteresis. Therefore, the shear history effect of MR fluids was experimentally investigated in this study. In a shear rate ramp test, the shear stress at low shear rate was higher in the shear rate ramp-down process than in the shear rate ramp-up process. If the next shear test started after a rest time, the start shear stress decayed slowly and approached the original value of the first test when the interval was long enough. The MR fluids also displayed obvious hysteresis loops during the current ramp test. A high shear rate and magnetic field could reduce the shear history effect by accelerating particle structure evolutions, and then hysteresis decreased. This effect was ascribed to the evolution of particle structures during different test modes and durations, and the evolution is governed by interparticle interactions, viscous forces, and the Brownian motions of particles. These results indicated that the accuracy of the force control of MR fluids could be enhanced under high magnetic fields and high shear rates. Thus, these factors should be considered in MR actuator designs.

  13. Sheep shearing and sudden death.

    PubMed

    Irandoust, Shabnum; Heath, Karen; Byard, Roger W

    2013-11-01

    A 29-year-old sheep shearer collapsed after walking across a shearing shed floor, holding his hand over an incised wound to his neck. Attempted resuscitation was unsuccessful. At the death scene fine arterial blood spatter was noted and at autopsy a single incised wound to the neck was observed, the patterned edges of which corresponded to the teeth of the shears. Dissection revealed injury to the underlying jugular vein and the mid portion of the common carotid artery. Death was attributed to blood loss from an incised wound of the left side of the neck. This case demonstrates the rare event of an accidental death related to the actions of a sheep. Although a relatively small animal, review of the circumstances and interviews with those present revealed that sudden and unexpected movement of the sheep during shearing had caused the shearer to lose control of his electrical shears resulting in a lethal incised wound to the neck. The blood spatter pattern at the scene was supportive of both witness descriptions and the findings at autopsy. PMID:24237795

  14. External Shear in Quadruply Imaged Lens Systems

    E-print Network

    Gilbert P. Holder; Paul L. Schechter

    2003-02-06

    We use publicly available N-body simulations and semi-analytic models of galaxy formation to estimate the levels of external shear due to structure near the lens in gravitational lens systems. We also describe two selection effects, specific to four-image systems, that enhance the probability of observing systems to have higher external shear. Ignoring additional contributions from "cosmic shear" and assuming that lens galaxies are not significantly flattened, we find that the mean shear at the position of a quadruple lens galaxy is 0.11, the rms shear is roughly 0.15, and there is roughly a 45% likelihood of external shear greater than 0.1. This is much larger than previous estimates and in good agreement with typical measured external shear. The higher shear primarily stems from the tendency of early-type galaxies, which are the majority of lenses, to reside in overdense regions.

  15. Shear dynamics in higher dimensional FLRW cosmology

    NASA Astrophysics Data System (ADS)

    Pahwa, Isha; Nandan, Hemwati; Goswami, Umananda Dev

    2015-12-01

    We study the shear dynamics of higher dimensional Friedmann-Lemaître-Robertson-Walker (FLRW) cosmology by considering a non-perfect fluid which exerts different pressure in the normal and extra dimensions. We generalise the definition of shear tensor for higher dimensional spacetime and prove it to be consistent with the evolution equation for shear tensor obtained from the Ricci identities. The shear tensor however vanishes for the case of usual FLRW metric in four dimensions. The evolution of shear tensor for higher dimensional FLRW cosmology is investigated numerically. The role of extra dimensions and other parameters involved in shear dynamics is discussed in detail. We find that with increase in anisotropy parameter, time of decay of shear increases while with increase in number of extra dimensions, shear tends to decay early.

  16. Could Crop Height Affect the Wind Resource at Agriculturally Productive Wind Farm Sites?

    NASA Astrophysics Data System (ADS)

    Vanderwende, Brian; Lundquist, Julie K.

    2015-11-01

    The collocation of cropland and wind turbines in the US Midwest region introduces complex meteorological interactions that could influence both agriculture and wind-power production. Crop management practices may affect the wind resource through alterations of land-surface properties. We use the weather research and forecasting (WRF) model to estimate the impact of crop height variations on the wind resource in the presence of a large turbine array. A hypothetical wind farm consisting of 121 1.8-MW turbines is represented using the WRF model wind-farm parametrization. We represent the impact of selecting soybeans rather than maize by altering the aerodynamic roughness length in a region approximately 65 times larger than that occupied by the turbine array. Roughness lengths of 0.1 and 0.25 m represent the mature soy crop and a mature maize crop, respectively. In all but the most stable atmospheric conditions, statistically significant hub-height wind-speed increases and rotor-layer wind-shear reductions result from switching from maize to soybeans. Based on simulations for the entire month of August 2013, wind-farm energy output increases by 14 %, which would yield a significant monetary gain. Further investigation is required to determine the optimal size, shape, and crop height of the roughness modification to maximize the economic benefit and minimize the cost of such crop-management practices. These considerations must be balanced by other influences on crop choice such as soil requirements and commodity prices.

  17. Shear viscosity of the quark matter

    E-print Network

    Masaharu Iwasaki; Hiromasa Ohnishi; Takahiko Fukutome

    2007-05-14

    We discuss shear viscosity of the quark matter by using Kubo formula. The shear viscosity is calculated in the framework of the quasi-particle RPA for the Nambu-Jona-Lasinio model. We obtain a formula that the shear viscosity is expressed by the quadratic form of the quark spectral function in the chiral symmetric phase. The magnitude of the shear viscosity is discussed assuming the Breit-Wigner type for the spectral function.

  18. Refraction of shear zones in granular materials

    E-print Network

    Tamas Unger

    2007-01-08

    We study strain localization in slow shear flow focusing on layered granular materials. A heretofore unknown effect is presented here. We show that shear zones are refracted at material interfaces in analogy with refraction of light beams in optics. This phenomenon can be obtained as a consequence of a recent variational model of shear zones. The predictions of the model are tested and confirmed by 3D discrete element simulations. We found that shear zones follow Snell's law of light refraction.

  19. Measurements in support of wind farm simulations and power forecasts: The Crop/Wind-energy Experiments (CWEX)

    NASA Astrophysics Data System (ADS)

    Takle, E. S.; Rajewski, D. A.; Lundquist, J. K.; Gallus, W. A., Jr.; Sharma, A.

    2014-06-01

    The Midwest US currently is experiencing a large build-out of wind turbines in areas where the nocturnal low-level jet (NLLJ) is a prominent and frequently occurring feature. We describe shear characteristics of the NLLJ and their influence on wind power production. Reports of individual turbine power production and concurrent measurements of near-surface thermal stratification are used to turbine wake interactions and turbine interaction with the overlying atmosphere. Progress in forecasting conditions such as wind ramps and shear are discussed. Finally, the pressure perturbation introduced by a line of turbines produces surface flow convergence that may create a vertical velocity and hence a mesoscale influence on cloud formation by a wind farm.

  20. Shear flows and shear viscosity in a two-dimensional Yukawa system (dusty plasma)

    E-print Network

    Goree, John

    Shear flows and shear viscosity in a two-dimensional Yukawa system (dusty plasma) V. Nosenko and J) Abstract The shear viscosity of a two-dimensional liquid-state dusty plasma was mea- sured experimentally in the shear flow to a Navier-Stokes model, the kinematic viscosity was calculated; it was of order 1 mm2s-1

  1. Shear viscosity and shear thinning in two-dimensional Yukawa , J. Goree2

    E-print Network

    Goree, John

    Shear viscosity and shear thinning in two-dimensional Yukawa liquids Z. Donk´o1 , J. Goree2 , P using two different nonequi- librium molecular dynamics simulation methods. Shear viscosity values.e., the viscosity diminishes with increasing shear rate. It is expected that two-dimensional dusty plasmas

  2. Electrohydrodynamic Instability under an Oscillatory Shear Flow

    NASA Astrophysics Data System (ADS)

    Ogawa, Atsushi; Katsura, Shinichiro; Uesaka, Hideo; Harada, Yoshifumi

    2001-03-01

    We have experimentally studied the electrohydrodynamic instability in a nematic liquid crystal under an oscillatory shear flow. In the vicinity of an instability threshold, we observed the very slow dynamics of convection under the oscillatory shear flow with fixed control parameters. We found the resonant behavior between a mode of the underlying convection rolls and the shear flow. Dynamical scaling law is successfully applied.

  3. Stratified Shear Flow: Instability and Wave Radiation

    E-print Network

    Sutherland, Bruce

    ­dimensional shear flow in nonuniformly stratified fluid is examined with a focus on investigating circumstances into coherent vortices on the scale of the wavelength of the most unstable mode. If the fluid above the shear, the shear­layer thickens and so may become unstable to disturbances of ever larger scale limited only

  4. Stratified Shear Flow: Instability and Wave Radiation

    E-print Network

    Sutherland, Bruce

    -dimensional shear flow in nonuniformly stratified fluid is examined with a focus on investigating circumstances into coherent vortices on the scale of the wavelength of the most unstable mode. If the fluid above the shear, the shear-layer thickens and so may become unstable to disturbances of ever larger scale limited only

  5. Shear-wave velocity of slope sediments near Hudson Canyon from analysis of ambient noise

    NASA Astrophysics Data System (ADS)

    Miller, N. C.; Ten Brink, U. S.; Collins, J. A.; McGuire, J. J.; Flores, C. H.

    2014-12-01

    We present new ambient noise data that help constrain the shear strength of marine sediments on the continental slope north of Hudson Canyon on the U.S. Atlantic margin. Sediment shear strength is a key parameter in models of potentially tsunamigenic, submarine slope failures, but shear strength is difficult to measure in situ and is expected to evolve in time with changes in pore pressure. The ambient noise data were recorded by 11 short-period, ocean-bottom seismometers and hydrophones deployed in a ~1 by 1.5 km array for ~6 months on the continental slope. These high frequency (~0.1 - 50 Hz), narrow-aperture data are expected to record noise propagating as interface waves and/or resonating in the upper ~500 m of sediment. Propagation of interface waves is controlled by the shear-wave velocity of the sediment, which we measure by calculating lag-times in cross-correlations of waveforms recorded by pairs of receivers. These measurements of shear-wave velocity will be used to constrain shear strength. The data also appear to record wind-generated noise resonating in layered sediment. We expect this resonance to also be sensitive to shear-wave velocity, and spectral analysis and modeling of harmonics may provide a second constraint on sediment shear strength. Both the correlogram- and spectral-based measurements can be made using hour- to day-long segments of data, enabling us to constrain temporal evolution of shear-wave velocity and potential forcing mechanisms (e.g., tidal and storm loading and submarine groundwater discharge) through the ~6 month deployment.

  6. Wind turbine

    DOEpatents

    Cheney, Jr., Marvin C. (Glastonbury, CT)

    1982-01-01

    A wind turbine of the type having an airfoil blade (15) mounted on a flexible beam (20) and a pitch governor (55) which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter (85) which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum (65,70) which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member (90) which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

  7. Wind Generators

    NASA Technical Reports Server (NTRS)

    1989-01-01

    When Enerpro, Inc. president, Frank J. Bourbeau, attempted to file a patent on a system for synchronizing a wind generator to the electric utility grid, he discovered Marshall Space Flight Center's Frank Nola's power factor controller. Bourbeau advanced the technology and received a NASA license and a patent for his Auto Synchronous Controller (ASC). The ASC reduces generator "inrush current," which occurs when large generators are abruptly brought on line. It controls voltage so the generator is smoothly connected to the utility grid when it reaches its synchronous speed, protecting the components from inrush current damage. Generator efficiency is also increased in light winds by applying lower than rated voltage. Wind energy is utilized to drive turbines to generate electricity for utility companies.

  8. Modal wavefront reconstruction for radial shearing interferometer with lateral shear.

    PubMed

    Gu, Naiting; Huang, Linhai; Yang, Zeping; Luo, Qun; Rao, Changhui

    2011-09-15

    In a radial shearing interferometer, a portion of the test beam is magnified and used as the reference for the tested wavefront. However, the reference portion is always off center (lateral shear), which complicates the wavefront reconstruction. A modal method for solving this problem is presented here. This method uses orthogonal Zernike polynomials and its matrix formalism to calculate the Zernike coefficient of the wavefront under test. This approach has easier implementation, is better filtering, and has a more adaptive practical situation. The corresponding mathematical formula is deduced, and a computer simulation is also made to verify operation of the algorithm. The result of simulation analysis shows that the proposed method is correct and accurate. PMID:21931435

  9. Transiently Jammed State in Shear Thickening Suspensions under Shear

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Shomeek; Allen, Benjamin; Brown, Eric

    2014-03-01

    We examine the response of a suspension of cornstarch and water under normal impact at controlled velocities. This is a model system to understand why a person can run on the surface of a discontinuous shear thickening fluid. Using simultaneous high-speed imaging of the top and bottom surfaces along with normal force measurements allows us to investigate whether the force response is a result of system spanning structures. We observe a shear thickening transition where above a critical velocity the normal force increases by orders of magnitude. In the high force regime the force response is displacement dependent like a solid rather than velocity dependent like a liquid. The stresses are on the order of 106 Pa which is enough to hold up a person's weight. In this regime imaging shows the existence of a solid like structure that extends to the bottom interface.

  10. Dynamics of Sheared Granular Materials

    NASA Technical Reports Server (NTRS)

    Kondic, Lou; Utter, Brian; Behringer, Robert P.

    2002-01-01

    This work focuses on the properties of sheared granular materials near the jamming transition. The project currently involves two aspects. The first of these is an experiment that is a prototype for a planned ISS (International Space Station) flight. The second is discrete element simulations (DES) that can give insight into the behavior one might expect in a reduced-g environment. The experimental arrangement consists of an annular channel that contains the granular material. One surface, say the upper surface, rotates so as to shear the material contained in the annulus. The lower surface controls the mean density/mean stress on the sample through an actuator or other control system. A novel feature under development is the ability to 'thermalize' the layer, i.e. create a larger amount of random motion in the material, by using the actuating system to provide vibrations as well control the mean volume of the annulus. The stress states of the system are determined by transducers on the non-rotating wall. These measure both shear and normal components of the stress on different size scales. Here, the idea is to characterize the system as the density varies through values spanning dense almost solid to relatively mobile granular states. This transition regime encompasses the regime usually thought of as the glass transition, and/or the jamming transition. Motivation for this experiment springs from ideas of a granular glass transition, a related jamming transition, and from recent experiments. In particular, we note recent experiments carried out by our group to characterize this type of transition and also to demonstrate/ characterize fluctuations in slowly sheared systems. These experiments give key insights into what one might expect in near-zero g. In particular, they show that the compressibility of granular systems diverges at a transition or critical point. It is this divergence, coupled to gravity, that makes it extremely difficult if not impossible to characterize the transition region in an earth-bound experiment. In the DE modeling, we analyze dynamics of a sheared granular system in Couette geometry in two (2D) and three (3D) space dimensions. Here, the idea is to both better understand what we might encounter in a reduced-g environment, and at a deeper level to deduce the physics of sheared systems in a density regime that has not been addressed by past experiments or simulations. One aspect of the simulations addresses sheared 2D system in zero-g environment. For low volume fractions, the expected dynamics of this type of system is relatively well understood. However, as the volume fraction is increased, the system undergoes a phase transition, as explained above. The DES concentrate on the evolution of the system as the solid volume fraction is slowly increased, and in particular on the behavior of very dense systems. For these configurations, the simulations show that polydispersity of the sheared particles is a crucial factor that determines the system response. Figures 1 and 2 below, that present the total force on each grain, show that even relatively small (10 %) nonuniformity of the size of the grains (expected in typical experiments) may lead to significant modifications of the system properties, such as velocity profiles, temperature, force propagation, and formation shear bands. The simulations are extended in a few other directions, in order to provide additional insight to the experimental system analyzed above. In one direction, both gravity, and driving due to vibrations are included. These simulations allow for predictions on the driving regime that is required in the experiments in order to analyze the jamming transition. Furthermore, direct comparison of experiments and DES will allow for verification of the modeling assumptions. We have also extended our modeling efforts to 3D. The (preliminary) results of these simulations of an annular system in zero-g environment will conclude the presentation.

  11. Shear viscosity and shear thinning in two-dimensional Yukawa liquids

    E-print Network

    Z. Donkó; J. Goree; P. Hartmann; K. Kutasi

    2006-03-24

    A two-dimensional Yukawa liquid is studied using two different nonequilibrium molecular dynamics simulation methods. Shear viscosity values in the limit of small shear rates are reported for a wide range of Coulomb coupling parameter and screening length. At high shear rates it is demonstrated that this liquid exhibits shear thinning, i.e., the viscosity $\\eta$ diminishes with increasing shear rate. It is expected that two-dimensional dusty plasmas will exhibit this effect.

  12. Wind energy systems

    NASA Technical Reports Server (NTRS)

    Stewart, H. J.

    1978-01-01

    A discussion on wind energy systems involved with the DOE wind energy program is presented. Some of the problems associated with wind energy systems are discussed. The cost, efficiency, and structural design of wind energy systems are analyzed.

  13. Cracks faster than the shear wave speed

    PubMed

    Rosakis; Samudrala; Coker

    1999-05-21

    Classical dynamic fracture theories predict the surface wave speed to be the limiting speed for propagation of in-plane cracks in homogeneous, linear elastic materials subjected to remote loading. This report presents experimental evidence to the contrary. Intersonic shear-dominated crack growth featuring shear shock waves was observed along weak planes in a brittle polyester resin under far-field asymmetric loading. When steady-state conditions were attained, the shear cracks propagated at speeds close to 2 times the material shear wave speed. These observations have similarities to shallow earthquake events where intersonic shear rupture speeds have been surmised. PMID:10334984

  14. Shear piezoelectricity of optically active polysuccinimides

    NASA Astrophysics Data System (ADS)

    Tanimoto, Kazuhiro; Saihara, Shota; Adachi, Yu; Harada, Yuhei; Shiomi, Yuki; Tajitsu, Yoshiro

    2015-10-01

    Optically active crystalline polymers have shear piezoelectricity owing to their asymmetric crystal structure. In this study, to explore a novel shear piezoelectric polymer, we have focused on an imide ring structure and synthesized optically active polysuccinimides (PSIs), the minimum structure of optically active polyimides. As a result, optically active PSIs were obtained, and we observed that oriented optically active PSI films show shear piezoelectricity. Furthermore, both optical purity and molecular weight are significant factors in piezoelectric performance. This is the first report of the shear piezoelectricity of optically active polyimides, and we identify herein a novel category of a shear piezoelectric polymer.

  15. Apparatus for shearing spent nuclear fuel assemblies

    DOEpatents

    Weil, Bradley S. (Knoxville, TN); Metz, III, Curtis F. (Knoxville, TN)

    1980-01-01

    A method and apparatus are described for shearing spent nuclear fuel assemblies of the type comprising an array of fuel pins disposed within an outer metal shell or shroud. A spent fuel assembly is first compacted in a known manner and then incrementally sheared using fixed and movable shear blades having matched laterally projecting teeth which slidably intermesh to provide the desired shearing action. Incremental advancement of the fuel assembly after each shear cycle is limited to a distance corresponding to the lateral projection of the teeth to ensure fuel assembly breakup into small uniform segments which are amenable to remote chemical processing.

  16. Controlled shear/tension fixture

    DOEpatents

    Hsueh, Chun-Hway (Knoxville, TN); Liu, Chain-tsuan (Knoxville, TN); George, Easo P. (Knoxville, TN)

    2012-07-24

    A test fixture for simultaneously testing two material test samples is provided. The fixture provides substantially equal shear and tensile stresses in each test specimens. By gradually applying a load force to the fixture only one of the two specimens fractures. Upon fracture of the one specimen, the fixture and the load train lose contact and the second specimen is preserved in a state of upset just prior to fracture. Particular advantages of the fixture are (1) to control the tensile to shear load on the specimen for understanding the effect of these stresses on the deformation behavior of advanced materials, (2) to control the location of fracture for accessing localized material properties including the variation of the mechanical properties and residual stresses across the thickness of advanced materials, (3) to yield a fractured specimen for strength measurement and an unfractured specimen for examining the microstructure just prior to fracture.

  17. Scaling of entropic shear rigidity.

    PubMed

    Xing, Xiangjun; Mukhopadhyay, Swagatam; Goldbart, Paul M

    2004-11-26

    The scaling of shear modulus near the gelation-vulcanization transition is explored heuristically and analytically. It is found that in a dense melt the effective chains of the infinite cluster have sizes that scale sublinearly with their contour length. Consequently, each chain contributes k(B)T to the rigidity, which leads to a shear-modulus exponent dnu. In contrast, in phantom elastic networks the scaling is linear in the contour length, yielding an exponent identical to that of the random resistor network conductivity, as predicted by de Gennes. For nondense systems, the exponent should cross over to dnu when the percolation correlation length is much larger than the density-fluctuation length. PMID:15601099

  18. Stability Criteria of 3D Inviscid Shears

    E-print Network

    Y. Charles Li

    2009-11-09

    The classical plane Couette flow, plane Poiseuille flow, and pipe Poiseuille flow share some universal 3D steady coherent structure in the form of "streak-roll-critical layer". As the Reynolds number approaches infinity, the steady coherent structure approaches a 3D limiting shear of the form ($U(y,z), 0, 0$) in velocity variables. All such 3D shears are steady states of the 3D Euler equations. This raises the importance of investigating the stability of such inviscid 3D shears in contrast to the classical Rayleigh theory of inviscid 2D shears. Several general criteria of stability for such inviscid 3D shears are derived. In the Appendix, an argument is given to show that a 2D limiting shear can only be the classical laminar shear.

  19. Transverse shear stiffness of laminated anisotropic shells

    NASA Technical Reports Server (NTRS)

    Cohen, G. A.

    1978-01-01

    Equations are derived for the transverse shear stiffness of laminated anisotropic shells. Without making assumptions for thickness distribution for either transverse shear stresses or strains, constitutive equations for the transverse shear deformation theory of anisotropic heterogeneous shells are found. The equations are based on Taylor series expansions about a generic point for stress resultants and couples, identically satisfying plate equilibrium equations. These equations are used to find statically correct expressions for in-surface stresses, transverse shear stresses, and the area density of transverse shear strain energy, in terms of transverse shear stress resultants and redundants. The application of Castigliano's theorem of least work minimizes shear strain energy with respect to the redundants. Examples are presented for several laminated walls. Good agreement is found between the results and those of exact three-dimensional elasticity solutions for the cylindrical bending of a plate.

  20. The barotropic normal modes in certain shear flows and the traveling waves in the atmosphere

    NASA Technical Reports Server (NTRS)

    Chen, Ping

    1993-01-01

    It is shown analytically and numerically that in certain shear flows the linearized nondivergent barotropic vorticity equation has a limited number of neutral normal modes. The latitudinal structures of these shear flows can be expressed as polynomials of the sine of latitude. The first few such shear flows resemble the gross features of the zonal winds in the atmosphere of the earth at different times and altitudes. The spatial structures of the neutral normal modes in these shear flows are spherical harmonics, and, as a consequence, these modes are also the exact solutions of the fully nonlinear equation because the nonlinear interaction term vanishes identically. The spatial structures of the observed 5-, 4-, 2-, and 16-day free traveling waves in the atmosphere are often identified with the spherical harmonics with indices of (m, n) = ( 1, 2), (2, 3), (3, 3), and ( 1, 4), which are known previously as the neutral normal modes of the nondivergent barotropic vorticity equation in a motionless background state. Our results could explain why these free traveling waves can survive the shearing effects of zonal flows that are far different from rest because these spherical harmonics are also normal modes in certain shear flows that resemble the observations of the atmosphere.

  1. Shear Strength of Aluminum Oxynitride

    NASA Astrophysics Data System (ADS)

    Dandekar, Dattatraya P.; Vaughan, Brian A. M.; Proud, William G.

    2007-06-01

    Aluminum oxynitride (AlON) is a transparent, polycrystalline cubic spinel. The results of investigations^1-4 on shock response of AlON permit determination of the equation of state, and shear strength retained under shock compression. Whereas the values of the HEL of AlON holds no surprises, the inelastic response of AlON reported in Ref. 1-4 differ significantly and is stress dependent. The results of Ref. 1-2 show that AlON retains a shear strength of 3 to 4 GPa when shocked up to around 20 GPa, but the results of Ref, 3-4 seem to suggest a possible loss of shear strength when shocked to 16 GPa and beyond. Our analysis examines the observed differences in the inelastic response of AlON reported in these four studies . 1. J. U. Cazamias, et. al., in Fundamental Issues and Applications of Shock-Wave and High Strain Rate Phenomena, Eds. Staudhammer, Murr, and Meyers, Elsevier, NY, 173 (2001). 2. B. A. M. Vaughn, et.al., Shock Physics, Cavendish Laboratory, Report SP/1092 (2001) 3. T. Sekine, et.al., J. Appl. Phys. 94, 4803 (2003). 4. T. F. Thornhill, et.al., Shock Compression of Matter-2005, Eds. Furnish, Elert, Russell, White, AIP, NY, 143 (2006).

  2. The UTRC wind energy conversion system performance analysis for horizontal axis wind turbines (WECSPER)

    NASA Technical Reports Server (NTRS)

    Egolf, T. A.; Landgrebe, A. J.

    1981-01-01

    The theory for the UTRC Energy Conversion System Performance Analysis (WECSPER) for the prediction of horizontal axis wind turbine performance is presented. Major features of the analysis are the ability to: (1) treat the wind turbine blades as lifting lines with a prescribed wake model; (2) solve for the wake-induced inflow and blade circulation using real nonlinear airfoil data; and (3) iterate internally to obtain a compatible wake transport velocity and blade loading solution. This analysis also provides an approximate treatment of wake distortions due to tower shadow or wind shear profiles. Finally, selected results of internal UTRC application of the analysis to existing wind turbines and correlation with limited test data are described.

  3. Effects of incoming wind condition and wind turbine aerodynamics on the hub vortex instability

    NASA Astrophysics Data System (ADS)

    Ashton, R.; Viola, F.; Gallaire, F.; Iungo, G. V.

    2015-06-01

    Dynamics and instabilities occurring in the near-wake of wind turbines have a crucial role for the wake downstream evolution, and for the onset of far-wake instabilities. Furthermore, wake dynamics significantly affect the intra-wind farm wake flow, wake interactions and potential power losses. Therefore, the physical understanding and predictability of wind turbine wake instabilities become a nodal point for prediction of wind power harvesting and optimization of wind farm layout. This study is focused on the prediction of the hub vortex instability encountered within wind turbine wakes under different operational conditions of the wind turbine. Linear stability analysis of the wake flow is performed by means of a novel approach that enables to take effects of turbulence on wake instabilities into account. Stability analysis is performed by using as base flow the time-averaged wake velocity field at a specific downstream location. The latter is modeled through Carton-McWilliams velocity profiles by mimicking the presence of the hub vortex and helicoidal tip vortices, and matching the wind turbine thrust coefficient predicted through the actuator disc model. The results show that hub vortex instability is promoted by increasing the turbine thrust coefficient. Indeed, a larger aerodynamic load produces an enhanced wake velocity deficit and axial shear, which are considered the main sources for the wake instability. Nonetheless, wake swirl also promotes hub vortex instability, and it can also affect the azimuthal wavenumber of the most unstable mode.

  4. Formation of Relativistic Outflows in Shearing Black Hole Accretion Coronae

    E-print Network

    Prasad Subramanian; Peter A. Becker; Demosthenes Kazanas

    1999-03-22

    We examine the possibility that the relativistic jets observed in many active galactic nuclei may be powered by the Fermi acceleration of protons in a tenuous corona above a two-temperature accretion disk. In this picture the acceleration arises as a consequence of the shearing motion of the magnetic field in the corona, which is anchored in the underlying Keplerian disk. The protons in the corona have a power-law distribution because the density there is too low for proton-proton collisions to thermalize the energy supplied via Fermi acceleration. The same shear acceleration mechanism also operates in the disk itself, however, there the density is high enough for thermalization to occur and consequently the disk protons have a Maxwellian distribution. Particle acceleration in the corona leads to the development of a pressure-driven wind that passes through a critical point and subsequently transforms into a relativistic jet at large distances from the black hole. We combine the critical conditions for the wind with the structure equations for the disk and the corona to obtain a coupled disk/corona/wind model. Using the coupled model we compute the asymptotic Lorentz factor $\\Gamma_\\infty$ of the jet as a function of the cylindrical starting radius at the base of the outflow, in the corona. Our results suggest that $\\Gamma_\\infty \\lapprox 10$, which is consistent with observations of superluminal motion in blazars. We show that collisions between the jet and broad-line emission clouds can produce high-energy radiation with a luminosity sufficient to power the $\\gamma$-rays observed from blazars. Subject headings: radiation mechanisms: non-thermal, accretion, accretion disks, acceleration of particles, gamma rays: theory

  5. Reversible shear thickening at low shear rates of electrorheological fluids under electric fields

    E-print Network

    Yu Tian; Minliang Zhang; Jile Jiang; Noshir Pesika; Hongbo Zeng; Jacob Israelachvili; Yonggang Meng; Shizhu Wen

    2010-08-24

    Shear thickening is a phenomenon of significant viscosity increase of colloidal suspensions. While electrorheological (ER) fluids can be turned into a solid-like material by applying an electric field, their shear strength is widely represented by the attractive electrostatic interaction between ER particles. By shearing ER fluids between two concentric cylinders, we show a reversible shear thickening of ER fluids above a low critical shear rate (100 V/mm), which could be characterized by a modified Mason number. Shear thickening and electrostatic particle interaction-induced inter-particle friction forces is considered to be the real origin of the high shear strength of ER fluids, while the applied electric field controls the extent of shear thickening. The electric field-controlled reversible shear thickening has implications for high-performance ER/magnetorheological (MR) fluid design, clutch fluids with high friction forces triggered by applying local electric field, other field-responsive materials and intelligent systems.

  6. Use of Acoustic Wind Profilers for Uninhabited Aerial Vehicle Flight Test Activities

    NASA Technical Reports Server (NTRS)

    Donnohue, Casey J.; Underwood, Ken; Bellue, Dan G.

    2001-01-01

    Sonic detection and ranging (SODAR) systems provide crucial information to meteorologists for advising uninhabited aerial vehicle (UAV) flight crews and mission directors on historical, current, and forecasted wind and turbulence conditions. The SODAR system provided advanced warning of increasing surface winds for an X-38 flight on February 6, 1999. The SODAR system has also provided important postflight data for X-38 engineers to review the performance of the parafoil in the presence of strong wind shears near the surface at landing.

  7. Heating of the Solar Wind Beyond 1 AU by Turbulent Dissipation

    E-print Network

    Oughton, Sean

    of energy into the solar wind is argued to result from the dissipation of low frequency magnetohydrodynamic(comp) = C shear(comp) U r Z 2 ; (1) where Z 2 = hv 2 + b 2 i is the energy density, U is the solar windSH 4.1.08 Heating of the Solar Wind Beyond 1 AU by Turbulent Dissipation C. W. Smith 1 , G. P. Zank

  8. 77 FR 29633 - Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-18

    ... Energy Regulatory Commission Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC, Alta Wind XIII, LLC, Alta Wind XIV, LLC, Alta Wind XV, LLC, Alta Windpower... Practice and Procedure, 18 CFR 385.207, Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta...

  9. Nucleation of shear bands in amorphous alloys.

    PubMed

    Perepezko, John H; Imhoff, Seth D; Chen, Ming-Wei; Wang, Jun-Qiang; Gonzalez, Sergio

    2014-03-18

    The initiation and propagation of shear bands is an important mode of localized inhomogeneous deformation that occurs in a wide range of materials. In metallic glasses, shear band development is considered to center on a structural heterogeneity, a shear transformation zone that evolves into a rapidly propagating shear band under a shear stress above a threshold. Deformation by shear bands is a nucleation-controlled process, but the initiation process is unclear. Here we use nanoindentation to probe shear band nucleation during loading by measuring the first pop-in event in the load-depth curve which is demonstrated to be associated with shear band formation. We analyze a large number of independent measurements on four different bulk metallic glasses (BMGs) alloys and reveal the operation of a bimodal distribution of the first pop-in loads that are associated with different shear band nucleation sites that operate at different stress levels below the glass transition temperature, Tg. The nucleation kinetics, the nucleation barriers, and the density for each site type have been determined. The discovery of multiple shear band nucleation sites challenges the current view of nucleation at a single type of site and offers opportunities for controlling the ductility of BMG alloys. PMID:24594599

  10. Temporal oscillations of the shear stress and scattered light in a shear-banding--shear-thickening micellar solution.

    PubMed

    Azzouzi, H; Decruppe, J P; Lerouge, S; Greffier, O

    2005-08-01

    The results of optical and rheological experiments performed on a viscoelastic solution (cetyltrimethylammonium bromide + sodium salicylate in water) are reported. The flow curve has a horizontal plateau extending between two critical shear rates characteristic of heterogeneous flows formed by two layers of fluid with different viscosities. These two bands which also have different optical anisotropy are clearly seen by direct observation in polarized light. At the end of the plateau, apparent shear thickening is observed in a narrow range of shear rates; in phase oscillations of the shear stress and of the first normal stress difference are recorded in a shearing device operating under controlled strain. The direct observation of the annular gap of a Couette cell in a direction perpendicular to a plane containing the vorticity shows that the turbidity of the whole sample also undergoes time dependent variations with the same period as the shear stress. However no banding is observed during the oscillations and the flow remains homogeneous. PMID:16132153

  11. Aeolian Shear Stress Ratio Measurements within Mesquite-Dominated Landscapes of the Chihuahuan Desert, New Mexico, USA

    NASA Technical Reports Server (NTRS)

    King, James; Nickling, W. G.; Gilliles, J. A.

    2006-01-01

    A field study was conducted to ascertain the amount of protection that mesquite-dominated communities provide to the surface from wind erosion. The dynamics of the locally accelerated evolution of a mesquite/coppice dune landscape and the undetermined spatial dependence of potential erosion by wind from a shear stress partition model were investigated. Sediment transport and dust emission processes are governed by the amount of protection that can be provided by roughness elements. Although shear stress partition models exist that can describe this, their accuracy has only been tested against a limited dataset because instrumentation has previously been unable to provide the necessary measurements. This study combines the use of meteorological towers and surface shear stress measurements with Irwin sensors to measure the partition of shear stress in situ. The surface shear stress within preferentially aligned vegetation (within coppice dune development) exhibited highly skewed distributions, while a more homogenous surface stress was recorded at a site with less developed coppice dunes. Above the vegetation, the logarithmic velocity profile deduced roughness length (based on 10-min averages) exhibited a distinct correlation with compass direction for the site with vegetation preferentially aligned, while the site with more homogenously distributed vegetation showed very little variation in the roughness length. This distribution in roughness length within an area, defines a distribution of a resolved shear stress partitioning model based on these measurements, ultimately providing potential closure to a previously uncorrelated model parameter.

  12. WAKE OF A BLOCK VEHICLE IN A SHEAR-FREE BOUNDARY FLOW: AN EXPERIMENTAL AND THEORETICAL STUDY

    EPA Science Inventory

    The wake of a moving vehicle was simulated using a specially-constructed wind tunnel with a moving floor. A 'block-shaped' model vehicle was fixed in position over the test-section floor while the floor moved at the freestream air speed to produce a uniform, shear-free, approach ...

  13. EXPERIMENTAL AND THEORETICAL STUDY OF THE WAKE OF A BLOCK-SHAPED VEHICLE IN A SHEAR-FREE BOUNDARY FLOW

    EPA Science Inventory

    The wake of a moving vehicle was simulated using a specially-constructed wind tunnel with a moving floor. A 'block-shaped' model vehicle was fixed in position over the test-section floor while the floor moved at the freestream air speed to produce a uniform, shear-free, approach ...

  14. Magnetofluid Turbulence in the Solar Wind

    NASA Technical Reports Server (NTRS)

    Goldstein, Melvyn L.

    2008-01-01

    The solar wind shows striking characteristics that suggest that it is a turbulent magnetofluid, but the picture is not altogether simple. From the earliest observations, a strong correlation between magnetic fluctuations and plasma velocity fluctuations was noted. The high corrections suggest that the fluctuations are Alfven waves. In addition, the power spectrum of the magnetic fluctuation showed evidence of an inertial range that resembled that seen in fully-developed fluid turbulence. Alfven waves, however, are exact solutions of the equations of incompressible magnetohydrodynamics. Thus, there was a puzzle: how can a magnetofluid consisting of Alfven waves be turbulent? The answer lay in the role of velocity shears in the solar wind that could drive turbulent evolution. Puzzles remain: for example, the power spectrum of the velocity fluctuations is less steep than the slope of the magnetic fluctuations, nor do we understand even now why the solar wind appears to be nearly incompressible with a -5/3 power-spectral index.

  15. Overview of 6- X 6-foot wind tunnel aero-optics tests. [transonic wind tunnel tests

    NASA Technical Reports Server (NTRS)

    Buell, D. A.

    1980-01-01

    The splitter-plate arrangement used in tests in the 6 x 6 foot wind tunnel and how it was configured to study boundary layers, both heated and unheated, shear layers over a cavity, separated flows behind spoilers, accelerated flows around a turret, and a turret wake are described. The flows are characterized by examples of the steady-state pressure and of velocity profiles through the various types of flow layers.

  16. Upwelling of Arctic pycnocline associated with shear motion of sea ice

    NASA Technical Reports Server (NTRS)

    McPhee, M. G.; Kwok, R.; Robins, R.; Coon, M.

    2006-01-01

    High-resolution radar imagery shows that the dynamic response of winter sea ice to gradients in large-scale surface wind stress is often localized along quasi-linear fractures hundreds of kilometers long. Relative shearing motion across these narrow fractures can exceed 10 cm/s. In one event recorded during the drift of the SHEBA ice camp, we observed an intense zone of pycnocline upwelling (approx.14 m) associated with significant shear motion near the camp, while upward turbulent heat flux in the ocean boundary layer reached nearly 400 W/sq m, an order of magnitude greater than at any other time during the year-long drift. We attribute the upwelling to Ekman pumping associated with concentrated ice shear. Over the entire Arctic Ocean sea ice cover, this process could be responsible for significant heat exchange between the cold surface layer and warmer subsurface water at the ubiquitous fractures resulting from large-scale atmosphere-ice interactions.

  17. 78 FR 29364 - Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-20

    ...Exelon Wind 9, LLC, Exelon Wind 10, LLC, Exelon Wind 11, LLC, High Plains Wind Power, LLC v. Xcel Energy Services, Inc., Southwestern...LLC, Exelon Wind 11, LLC, and High Plains Wind Power, LLC (Complainants) filed a formal...

  18. Wind Technologies & Evolving Opportunities (Presentation)

    SciTech Connect

    Robichaud, R.

    2014-07-01

    This presentation covers opportunities for wind technology; wind energy market trends; an overview of the National Wind Technology Center near Boulder, Colorado; wind energy price and cost trends; wind turbine technology improvements; and wind resource characterization improvements.

  19. Steel Plate Shear Walls: Efficient Structural Solution for Slender High-Rise in China

    SciTech Connect

    Mathias, Neville; Long, Eric; Sarkisian, Mark; Huang Zhihui

    2008-07-08

    The 329.6 meter tall 74-story Jinta Tower in Tianjin, China, is expected, when complete, to be the tallest building in the world with slender steel plate shear walls used as the primary lateral load resisting system. The tower has an overall aspect ratio close to 1:8, and the main design challenge was to develop an efficient lateral system capable of resisting significant wind and seismic lateral loads, while simultaneously keeping wind induced oscillations under acceptable perception limits. This paper describes the process of selection of steel plate shear walls as the structural system, and presents the design philosophy, criteria and procedures that were arrived at by integrating the relevant requirements and recommendations of US and Chinese codes and standards, and current on-going research.

  20. Rheology of discontinuously shear thickening suspensions beyond simple shear

    NASA Astrophysics Data System (ADS)

    Zimoch, Pawel; McKinley, Gareth; Hosoi, Anette

    2012-02-01

    The behavior of discontinuously shear thickening suspensions in flows other than simple shear is not well understood, in part due to unresolved experimental challenges. For example, such suspensions thicken most easily close to rigid boundaries due to the no-slip condition. This makes experiments highly dependent on the shape and size of the container used. We show that by placing a lubricating layer of oil between the suspension and the container we can generate flows where thickening is nearly independent of rigid boundaries. This method is particularly useful in creating quasi one- and two-dimensional flows, which can be easily visualized. We use this method to conduct capillary breakup experiments with thickening suspensions of silica and cornstarch particles, in which we observe the formation of beads-on-a-string morphologies with multiple satellite and sub-satellite bead generations, similar to the morphologies observed in breakup of viscoelastic fluids. Using a one-dimensional continuum model, we show how nonlinear rheology of thickening suspensions results in the creation of these complex morphologies.

  1. Spatiotemporal Dynamics of Wind Velocity from Mini-Sodar Measurements

    NASA Astrophysics Data System (ADS)

    Krasnenko, N. P.; Tarasenkov, M. V.; Shamanaeva, L. G.

    2015-03-01

    Mini-sodar measurements of wind velocity profiles in the 20-200 m layer have demonstrated the high efficiency of the use of mini-sodars in monitoring the fine structure of the atmospheric boundary layer (ABL) and in detecting jets and wind shear. An analysis of measurements of vertical profiles of the wind velocity and its vertical and horizontal components has shown that analytical approximations of the vertical profile of the horizontal wind velocity are possible for both neutral and unstable stratifications of the atmosphere. They are well described by a logarithmic law. The approximation constants are found and the errors associated with their use are estimated. The established physical trends and the obtained constants for the horizontal and vertical components of the wind velocity allow a description of their hourly and daily dynamics and can be recommended for use in ABL models intended for prognostic calculations (forecasting). The vector representation makes it possible to visualize the spatiotemporal dynamics of the wind field in the atmospheric boundary layer, in particular to estimate the shape and size of jets and wind shear in them.

  2. Generality of shear thickening in suspensions

    E-print Network

    Eric Brown; Nicole A. Forman; Carlos S. Orellana; Hanjun Zhang; Benjamin W. Maynor; Douglas E. Betts; Joseph M. DeSimone; Heinrich M. Jaeger

    2010-02-05

    Suspensions are of wide interest and form the basis for many smart fluids. For most suspensions, the viscosity decreases with increasing shear rate, i.e. they shear thin. Few are reported to do the opposite, i.e. shear thicken, despite the longstanding expectation that shear thickening is a generic type of suspension behavior. Here we resolve this apparent contradiction. We demonstrate that shear thickening can be masked by a yield stress and can be recovered when the yield stress is decreased below a threshold. We show the generality of this argument and quantify the threshold in rheology experiments where we control yield stresses arising from a variety of sources, such as attractions from particle surface interactions, induced dipoles from applied electric and magnetic fields, as well as confinement of hard particles at high packing fractions. These findings open up possibilities for the design of smart suspensions that combine shear thickening with electro- or magnetorheological response.

  3. Hierarchical Cosmic Shear Power Spectrum Inference

    E-print Network

    Alsing, Justin; Jaffe, Andrew H; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till

    2015-01-01

    We develop a Bayesian hierarchical modelling approach for cosmic shear power spectrum inference, jointly sampling from the posterior distribution of the cosmic shear field and its (tomographic) power spectra. Inference of the shear power spectrum is a powerful intermediate product for a cosmic shear analysis, since it requires very few model assumptions and can be used to perform inference on a wide range of cosmological models \\emph{a posteriori} without loss of information. We show that joint posterior for the shear map and power spectrum can be sampled effectively by Gibbs sampling, iteratively drawing samples from the map and power spectrum, each conditional on the other. This approach neatly circumvents difficulties associated with complicated survey geometry and masks that plague frequentist power spectrum estimators, since the power spectrum inference provides prior information about the field in masked regions at every sampling step. We demonstrate this approach for inference of tomographic shear $E$-...

  4. Generality of shear thickening in dense suspensions.

    PubMed

    Brown, Eric; Forman, Nicole A; Orellana, Carlos S; Zhang, Hanjun; Maynor, Benjamin W; Betts, Douglas E; DeSimone, Joseph M; Jaeger, Heinrich M

    2010-03-01

    Suspensions are of wide interest and form the basis for many smart fluids. For most suspensions, the viscosity decreases with increasing shear rate, that is, they shear thin. Few are reported to do the opposite, that is, shear thicken, despite the longstanding expectation that shear thickening is a generic type of suspension behaviour. Here we resolve this apparent contradiction. We demonstrate that shear thickening can be masked by a yield stress and can be recovered when the yield stress is decreased below a threshold. We show the generality of this argument and quantify the threshold in rheology experiments where we control yield stresses arising from a variety of sources, such as attractions from particle surface interactions, induced dipoles from applied electric and magnetic fields, as well as confinement of hard particles at high packing fractions. These findings open up possibilities for the design of smart suspensions that combine shear thickening with electro- or magnetorheological response. PMID:20118945

  5. Shear Thickening and Migration in Granular Suspensions

    NASA Astrophysics Data System (ADS)

    Fall, Abdoulaye; Lemaître, Anaël; Bertrand, François; Bonn, Daniel; Ovarlez, Guillaume

    2010-12-01

    We study the emergence of shear thickening in dense suspensions of non-Brownian particles. We combine local velocity and concentration measurements using magnetic resonance imaging with macroscopic rheometry experiments. In steady state, we observe that the material is heterogeneous, and we find that the local rheology presents a continuous transition at low shear rate from a viscous to a shear thickening, Bagnoldian, behavior with shear stresses proportional to the shear rate squared, as predicted by a scaling analysis. We show that the heterogeneity results from an unexpectedly fast migration of grains, which we attribute to the emergence of the Bagnoldian rheology. The migration process is observed to be accompanied by macroscopic transient discontinuous shear thickening, which is consequently not an intrinsic property of granular suspensions.

  6. Shear Viscosity of Quark Matter

    E-print Network

    W. M. Alberico; S. Chiacchiera; H. Hansen; A. Molinari; M. Nardi

    2007-07-30

    We consider the shear viscosity of a system of quarks and its ratio to the entropy density above the critical temperature for deconfinement. Both quantities are derived and computed for different modeling of the quark self-energy, also allowing for a temperature dependence of the effective mass and width. The behaviour of the viscosity and the entropy density is argued in terms of the strength of the coupling and of the main characteristics of the quark self-energy. A comparison with existing results is also discussed.

  7. Conductor shears as iceberg encroaches

    SciTech Connect

    Not Available

    1984-10-01

    Operators in the Arctic regions must protect wellheads from encroaching icebergs and icepack sheets. Diverting ice masses and excavating large holes below scour depth is expensive. Now an alternate approach allows the conductor to shear, shuts in the well, and provides a method of re-entering the well. The new system has been successfully used by Mobil on two exploratory wells in the Hibernia field off eastern Canada. The wells used 18 3/4-in. wellheads rated at 10,000 psi with 36-in. conductor pipe. The performance of the system is discussed.

  8. Magnetorheological Shear Flow Near Jamming

    NASA Astrophysics Data System (ADS)

    Vågberg, Daniel; Tighe, Brian

    2015-03-01

    Flow in magnetorheological (MR) fluids and systems near jamming both display hallmarks of complex fluid rheology, including yield stresses and shear thinning viscosities. They are also tunable, which means that both phenomena can be used as a switching mechanism in ``smart'' fluids, i.e. fluids where properties can be tuned rapidly and reversibly by changing external parameters. We use numerical simulations to investigate the rheological properties of MR fluids close to the jamming transition as a function of the applied field and volume fraction. We are especially interested in the crossover region where both phenomena are needed to describe the observed dynamics. Funded by the Dutch Organization for Scientific Research (NWO).

  9. Shear deflection of composite wood beams 

    E-print Network

    Skaggs, Thomas David

    1992-01-01

    to characterize deflection. The primary objective of this research was to develop an algorithm to predict shear stress and deflection for layered composite wood beams. The shear stress model was developed using energy methods and Castigliano's theorem... of the textbook", The basis for many of the deflection equations for homogeneous materials are energy methods. The strain energy due to bending and shear can be found in several textbooks (e. g. Boresi and Sidebottom, 1985) as follows: v = fffr ' I...

  10. Internal gravity-shear waves in the atmospheric boundary layer from acoustic remote sensing data

    NASA Astrophysics Data System (ADS)

    Lyulyukin, V. S.; Kallistratova, M. A.; Kouznetsov, R. D.; Kuznetsov, D. D.; Chunchuzov, I. P.; Chirokova, G. Yu.

    2015-03-01

    The year-round continuous remote sounding of the atmospheric boundary layer (ABL) by means of the Doppler acoustic radar (sodar) LATAN-3 has been performed at the Zvenigorod Scientific Station of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, since 2008. A visual analysis of sodar echograms for four years revealed a large number of wavelike patterns in the intensity field of a scattered sound signal. Similar patterns were occasionally identified before in sodar, radar, and lidar sounding data. These patterns in the form of quasi-periodic inclined stripes, or cat's eyes, arise under stable stratification and significant vertical wind shears and result from the loss of the dynamic stability of the flow. In the foreign literature, these patterns, which we call internal gravity-shear waves, are often associated with Kelvin-Helmholtz waves. In the present paper, sodar echograms are classified according to the presence or absence of wavelike patterns, and a statistical analysis of the frequency of their occurrence by the year and season was performed. A relationship between the occurrence of the patterns and wind shear and between the wave length and amplitude was investigated. The criteria for the identification of gravity-shear waves, meteorological conditions of their excitation, and issues related to their observations were discussed.

  11. Development of a MEMS dual-axis differential capacitance floating element shear stress sensor

    SciTech Connect

    Barnard, Casey; Griffin, Benjamin

    2015-09-01

    A single-axis MEMS wall shear stress sensor with differential capacitive transduction method is produced. Using a synchronous modulation and demodulation interface circuit, the system is capable of making real time measurements of both mean and fluctuating wall shear stress. A sensitivity of 3.44 mV/Pa is achieved, with linearity in response demonstrated up to testing limit of 2 Pa. Minimum detectable signals of 340 ?Pa at 100 Hz and 120 ?Pa at 1 kHz are indicated, with a resonance of 3.5 kHz. Multiple full scale wind tunnel tests are performed, producing spectral measurements of turbulent boundary layers in wind speeds ranging up to 0.5 Ma (18 Pa of mean wall shear stress). The compact packaging allows for minimally invasive installation, and has proven relatively robust over multiple testing events. Temperature sensitivity, likely due to poor CTE matching of packaged materials, is an ongoing concern being addressed. These successes are being directly leveraged into a development plan for a dual-axis wall shear stress sensor, capable of producing true vector estimates at the wall.

  12. On the relationship between the surface pressure in a cavity and the shear layer above it

    NASA Astrophysics Data System (ADS)

    Ukeiley, Lawrence; Murray, Nathan

    2003-11-01

    The results of experiments to relate the velocity field in the shear layer above a cavity and the dynamic surface pressure on its floor will be discussed. The experiments used two component Particle Image Velocimetry (PIV) measurements sampled simultaneously with surface pressure measurements from piezo based sensors. These experiments were conducted in a newly constructed subsonic wind tunnel with cavities, in the wind tunnel floor, having length to depth (L/D) ratios typically characterized as open cavities. The two different L/D ratios allowed examination of cavities with and without strong evidence of resonating conditions. Analysis of the data using the Proper Orthogonal Decomposition shows the different flow structure for the resonating and non-resonating conditions. Furthermore, correlations between the fluctuating surface pressure and the velocity field in the shear layer above the cavity yield insight into the cavity resonant phenomena and its pumping action. Additionally a Stochastic Estimation procedure has been applied using the cavity surface pressure as the condition to estimate the time dependence of the shear layer above the cavity. This yields information of the kinematic processes of the large scale structures in the cavity shear layer and time dependent information of the sources in the cavity.

  13. Dynamic shear deformation in high purity Fe

    SciTech Connect

    Cerreta, Ellen K; Bingert, John F; Trujillo, Carl P; Lopez, Mike F; Gray, George T

    2009-01-01

    The forced shear test specimen, first developed by Meyer et al. [Meyer L. et al., Critical Adiabatic Shear Strength of Low Alloyed Steel Under Compressive Loading, Metallurgical Applications of Shock Wave and High Strain Rate Phenomena (Marcel Decker, 1986), 657; Hartmann K. et al., Metallurgical Effects on Impact Loaded Materials, Shock Waves and High Strain rate Phenomena in Metals (Plenum, 1981), 325-337.], has been utilized in a number of studies. While the geometry of this specimen does not allow for the microstructure to exactly define the location of shear band formation and the overall mechanical response of a specimen is highly sensitive to the geometry utilized, the forced shear specimen is useful for characterizing the influence of parameters such as strain rate, temperature, strain, and load on the microstructural evolution within a shear band. Additionally, many studies have utilized this geometry to advance the understanding of shear band development. In this study, by varying the geometry, specifically the ratio of the inner hole to the outer hat diameter, the dynamic shear localization response of high purity Fe was examined. Post mortem characterization was performed to quantify the width of the localizations and examine the microstructural and textural evolution of shear deformation in a bcc metal. Increased instability in mechanical response is strongly linked with development of enhanced intergranular misorientations, high angle boundaries, and classical shear textures characterized through orientation distribution functions.

  14. Periodically sheared 2D Yukawa systems

    NASA Astrophysics Data System (ADS)

    Kovács, Anikó Zsuzsa; Hartmann, Peter; Donkó, Zoltán

    2015-10-01

    We present non-equilibrium molecular dynamics simulation studies on the dynamic (complex) shear viscosity of a 2D Yukawa system. We have identified a non-monotonic frequency dependence of the viscosity at high frequencies and shear rates, an energy absorption maximum (local resonance) at the Einstein frequency of the system at medium shear rates, an enhanced collective wave activity, when the excitation is near the plateau frequency of the longitudinal wave dispersion, and the emergence of significant configurational anisotropy at small frequencies and high shear rates.

  15. The Descent Rates of the Shear Zones of the Equatorial QBO.

    NASA Astrophysics Data System (ADS)

    Kinnersley, Jonathan S.; Pawson, Steven

    1996-07-01

    The influence of vertical advection on the descent rate of the zero-wind line in both phases of the equatorial quasi-biennial oscillation (QBO) is investigated with the help of the `THIN AIR' stratosphere two-and-a-half-dimensional model. The model QBO is forced by two symmetric easterly and westerly waves, and yet the model reproduces qualitatively the observed asymmetry in the descent rates of the two shear zones due to the enhanced heating during easterly descent combined with the equatorial heating induced by the extratropical planetary waves. Observations show that the maximum easterly accelerations occur predominantly from May until July, which is when the modeled equatorial planetary-wave-induced heating rates are weakest. Hence, model results are consistent with the theory that vertical advection induced by extratropical planetary waves slows significantly the descent of the easterly shear zone. The model also shows the observed increase in vertical wind shear during stalling of the easterly descent (which increases the impact of vertical advection). In the model, the effect of cross-equatorial advection of momentum by the mean flow is negligible compared to the vertical advection. Changes in the propagation of planetary waves depending on the sign of the equatorial zonal wind have a small effect on the modeled equatorial heating rates and therefore do not play a large part in producing the modeled asymmetry in descent rates.

  16. Optical Beam-Shear Sensors

    NASA Technical Reports Server (NTRS)

    Martin, Stefan; Szwaykowski, Piotr

    2007-01-01

    A technique for measuring optical beam shear is based on collecting light from the four quadrants of the beam and comparing the optical power collected from each quadrant with that from the other three quadrants. As used here, "shear" signifies lateral displacement of a beam of light from a nominal optical axis. A sensor for implementing this technique consists of a modified focusing lens and a quad-cell photodetector, both centered on the nominal optical axis. The modification of the lens consists in cutting the lens into four sectors (corresponding to the four quadrants) by sawing along two orthogonal diameters, then reassembling the lens following either of two approaches described next. In one approach, the lens is reassembled by gluing the sectors back together. In the simplest variant of this approach, the kerf of the saw matches the spacing of the photodetector cells, so that the focus of each sector crosses the axis of symmetry to fall on the opposite photodetector cell (see figure). In another variant of this approach, the lens sectors are spaced apart to make their individual foci to fall on separate photodetector cells, without crossing the optical axis. In the case of a sufficiently wide beam, the modified lens could be replaced with four independent lenses placed in a square array, each focusing onto an independent photodetector

  17. Shear-Induced Reactive Gelation.

    PubMed

    Brand, Bastian; Morbidelli, Massimo; Soos, Miroslav

    2015-11-24

    In this work, we describe a method for the production of porous polymer materials in the form of particles characterized by narrow pore size distribution using the principle of shear-induced reactive gelation. Poly(styrene-co-divinylbenzene) primary particles with diameter ranging from 80 to 200 nm are used as building blocks, which are assembled into fractal-like clusters when exposed to high shear rates generated in a microchannel. It was found that independent of the primary particle size, it is possible to modulate the internal structure of formed fractal-like aggregates having fractal dimension ranging from 2.4 to 2.7 by varying the residence time in the microchannel. Thermally induced postpolymerization was used to increase the mechanical resilience of such formed clusters. Primary particle interpenetration was observed by SEM and confirmed by light scattering resulting in an increase of fractal dimension. Nitrogen sorption measurements and mercury porosimetry confirmed formation of a porous material with surface area ranging from 20 to 40 m(2)/g characterized by porosity of 70% and narrow pore size distribution with an average diameter around 700 nm without the presence of any micropores. The strong perfusive character of the synthesized material was confirmed by the existence of a plateau of the height equivalent to a theoretical plate measured at high reduced velocities using a chromatographic column packed with the synthesized microclusters. PMID:26488233

  18. Careers in Wind Energy

    ERIC Educational Resources Information Center

    Liming, Drew; Hamilton, James

    2011-01-01

    As a common form of renewable energy, wind power is generating more than just electricity. It is increasingly generating jobs for workers in many different occupations. Many workers are employed on wind farms: areas where groups of wind turbines produce electricity from wind power. Wind farms are frequently located in the midwestern, western, and…

  19. Prospecting for Wind

    ERIC Educational Resources Information Center

    Swapp, Andy; Schreuders, Paul; Reeve, Edward

    2011-01-01

    Many people use wind to help meet their needs. Over the years, people have been able to harness or capture the wind in many different ways. More recently, people have seen the rebirth of electricity-generating wind turbines. Thus, the age-old argument about technology being either good or bad can also be applied to the wind. The wind can be a…

  20. Aleutian Pribilof Islands Wind Energy Feasibility Study

    SciTech Connect

    Bruce A. Wright

    2012-03-27

    Under this project, the Aleutian Pribilof Islands Association (APIA) conducted wind feasibility studies for Adak, False Pass, Nikolski, Sand Point and St. George. The DOE funds were also be used to continue APIA's role as project coordinator, to expand the communication network quality between all participants and with other wind interest groups in the state and to provide continued education and training opportunities for regional participants. This DOE project began 09/01/2005. We completed the economic and technical feasibility studies for Adak. These were funded by the Alaska Energy Authority. Both wind and hydro appear to be viable renewable energy options for Adak. In False Pass the wind resource is generally good but the site has high turbulence. This would require special care with turbine selection and operations. False Pass may be more suitable for a tidal project. APIA is funded to complete a False Pass tidal feasibility study in 2012. Nikolski has superb potential for wind power development with Class 7 wind power density, moderate wind shear, bi-directional winds and low turbulence. APIA secured nearly $1M from the United States Department of Agriculture Rural Utilities Service Assistance to Rural Communities with Extremely High Energy Costs to install a 65kW wind turbine. The measured average power density and wind speed at Sand Point measured at 20m (66ft), are 424 W/m2 and 6.7 m/s (14.9 mph) respectively. Two 500kW Vestas turbines were installed and when fully integrated in 2012 are expected to provide a cost effective and clean source of electricity, reduce overall diesel fuel consumption estimated at 130,000 gallons/year and decrease air emissions associated with the consumption of diesel fuel. St. George Island has a Class 7 wind resource, which is superior for wind power development. The current strategy, led by Alaska Energy Authority, is to upgrade the St. George electrical distribution system and power plant. Avian studies in Nikolski and Sand Point have allowed for proper wind turbine siting without killing birds, especially endangered species and bald eagles. APIA continues coordinating and looking for funding opportunities for regional renewable energy projects. An important goal for APIA has been, and will continue to be, to involve community members with renewable energy projects and energy conservation efforts.

  1. Wind turbine

    SciTech Connect

    Traudt, R.F.

    1986-12-30

    This patent describes a wind turbine device having a main rotatable driven shaft, elongated blades operatively mounted on the main shaft for unitary rotation with the main shaft. The blade extends substantially radially away from the main shaft and is adapted to fold downwind under naturally occurring forces and simultaneously feather in direct response to the folding movement. A means associated with the blades is included for increasing the rate of fold relative to the rate of feather as the speed of rotation increases.

  2. Wind Streaks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 12 July 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth.

    Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms.

    Windstreaks are features caused by the interaction of wind and topographic landforms. The raised rims and bowls of impact craters causes a complex interaction such that the wind vortex in the lee of the crater can both scour away the surface dust and deposit it back in the center of the lee. If you look closely, you will see evidence of this in a darker 'rim' enclosing a brighter interior.

    Image information: VIS instrument. Latitude 6.9, Longitude 69.4 East (290.6 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  3. 75 FR 23263 - Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-03

    ... Energy Regulatory Commission Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC; Alta Wind VI, LLC; Alta Wind VII, LLC; Alta Wind VIII, LLC; Alta Windpower... Federal Energy Regulatory Commission (Commission), 18 CFR 285.207 (2009), Alta Wind I, LLC, Alta Wind...

  4. Determining ow type, shear rate and shear stress in magmas from bubble shapes and orientations

    E-print Network

    Manga, Michael

    the shear environments that produced bubble textures in obsidian samples using the results of theoretical the shapes and orientations of bubbles (vesicles) in obsidian to estimate shear rates and shear stresses conduits, the origin of pyroclastic obsidian, and the emplacement history and dynamics of obsidian flows

  5. Surface Shear Stress Around a Single Flexible Live Plant and a Rigid Cylinder

    NASA Astrophysics Data System (ADS)

    Walter, B. A.; Gromke, C.; Leonard, K. C.; Clifton, A.; Lehning, M.

    2010-12-01

    The sheltering effect of vegetation against soil erosion and snow transport has direct implications on land degradation and local water storage as snow in many arid and semi arid regions. Plants influence the erosion, transport and redeposition of soil and snow by the wind through momentum absorption, local stress concentration, trapping particles in motion and reducing the area of sediment exposed to the wind. The shear stress distributions on the ground beneath plant canopies determine the onset and magnitude of differential soil and snow erosion on rough or vegetated surfaces, but this has been studied exclusively with artificial and rigid vegetation elements thus far. Real plants have highly irregular structures that can be extremely flexible and porous. They align with the flow at higher wind speeds, resulting in considerable changes to the drag and flow regimes relative to rigid imitations of comparable size. We present measurements in the SLF atmospheric boundary layer wind tunnel of the surface shear stress distribution around a live grass plant (Lolium Perenne) and a solid cylinder of comparable size. Irwin sensors are used to measure pressure differences close to the surface which can be calibrated with surface shear stress velocities. The basal to frontal area index of the plant and the cylinder as well as the Reynolds number of the two experimental setups have been checked for similarity and show good agreement. Distinctive differences between the shear stress pattern around the plant and the cylinder can be attributed to the influence of the plant’s porosity and flexibility. The sheltered zone behind the plant is narrower in cross-stream and longer in streamwise direction than that of the cylinder. For the plant, the lowest shear stresses in the sheltered zone are 50% lower than the mean surface shear stress (? = 0.15 N/m2) in the undisturbed flow. The sheltering was higher behind the cylinder with values reduced by 70% relative to background. “Speed-up” zones on both sides of the roughness elements experienced peak shear stress values 60% above background for the plant and almost 130% higher for the cylinder. While the integral sheltering effect of the plant is smaller in size and magnitude than that of the cylinder, the peak shear stresses in the lateral speed up zones are significantly lower. Since the onset of soil erosion occurs when a critical threshold shear stress is experienced, the lower peak shear stress means that plants provide better protection against soil erosion than rigid elements. This result suggests that parameterizations of flow over vegetated surfaces based on measurements of rigid elements may be incorrect. Further work will investigate sheltering and shear stress concentrations as a function of cylinder / plant density using real canopies instead of single objects.

  6. Wind energy program overview

    NASA Astrophysics Data System (ADS)

    1992-02-01

    This overview emphasizes the amount of electric power that could be provided by wind power rather than traditional fossil fuels. New wind power markets, advances in technology, technology transfer, and wind resources are some topics covered in this publication.

  7. A study of some effects of vertical shear on thunderstorms

    NASA Technical Reports Server (NTRS)

    Connell, J.

    1976-01-01

    Evidence is presented for the existence of vortices and vortex pairs in thunderstorms. A preliminary parameterized model of the nonthermal generation of thunderstorm vortices derived from field observations of storms and laboratory observations of a jet in crossflow is reported, together with an explanation of how such a model might be used to guide analysis of mesoscale rawinsonde, radar, and satellite data toward an improved capability for prediction of thunderstorm motion and growth. Preliminary analyses of radar and satellite data from Atmospheric Variability Experiment IV are used with available rawinsonde data to develop a correlation between wind shears, instability, and thunderstorm motion and development. Specific studies are recommended for best development of concepts and utilization of data from Atmospheric Variability and Atmospheric Variability Severe Storms Experiments.

  8. SHEAR BEHAVIOR OF PRETENSIONED PRESTRESSED CONCRETE BEAMS

    E-print Network

    different types of stirrup were conventional single legged and double legged stirrups. and welded wire without web reinforcement. and the other was with stirrup of welded wire fabric. In order to make shear 15M deformed bars and two 13 mm 7-wire stress-relieved prestress- ing strands. The shear span length

  9. Shear-Induced Chaos Kevin K. Lin

    E-print Network

    Young, Lai-Sang

    Shear-Induced Chaos Kevin K. Lin and Lai-Sang Young Courant Institute of Mathematical Sciences New works of Wang and Young, we carry out numerical studies of shear-induced chaos in several parallel work is motivated by a series of papers by Wang and Young [34, 35, 36, 37]. In these papers

  10. Effect of Friction on Shear Jamming

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Ren, Jie; Dijksman, Joshua; Bares, Jonathan; Behringer, Robert

    2015-03-01

    Shear jamming of granular materials was first found for systems of frictional disks, with a static friction coefficient ? ~ 0 . 6 (Bi et al. Nature (2011)). Jamming by shear is obtained by starting from a zero-stress state with a packing fraction ? between ?J (isotropic jamming) and a lowest ?S for shear jamming. This phenomenon is associated with strong anisotropy in stress and the contact network in the form of force chains, which are stabilized and/or enhanced by the presence of friction. Whether shear jamming occurs for frictionless particles is under debate. The issue we address experimentally is how reducing friction affects shear jamming. We put the Teflon-wrapped photoelastic disks, lowering the friction substantially from previous experiments, in a well-studied 2D shear apparatus (Ren et al. PRL (2013)), which provides a uniform simple shear. Shear jamming is still observed; however, the difference ?J -?S is smaller with lower friction. We also observe larger anisotropies in fragile states compared to experiments with higher friction particles at the same density. In ongoing work we are studying systems using photoelastic disks with fine gears on the edge to generate very large effective friction. We acknowledge support from NSF Grant DMR1206351, NSF Grant DMS-1248071, NASA Grant NNX10AU01G and William M. Keck Foundation.

  11. Study of shear-stiffened elastomers

    NASA Astrophysics Data System (ADS)

    Tian, Tongfei; Li, Weihua; Ding, Jie; Alici, Gursel; Du, Haiping

    2013-06-01

    Shear thickening fluids, which are usually concentrated colloidal suspensions composed of non-aggregating solid particles suspended in fluids, exhibit a marked increase in viscosity beyond a critical shear rate. This increased viscosity is seen as being both 'field-activated', due to the dependence on shearing rate, as well as reversible. Shear thickening fluids have found good applications as protection materials, such as in liquid body armor, vibration absorber or dampers. This research aims to expand the protection material family by developing a novel solid status shear thickening material, called shear-stiffened elastomers. These new shear-stiffened elastomers were fabricated with the mixture of silicone rubber and silicone oil. A total of four SSE samples were fabricated in this study. Their mechanical and rheological properties under both steady-state and dynamic loading conditions were tested with a parallel-plate. The effects of silicone oil composition and angular frequency were summarized. When raising the angular frequency in dynamic shear test, the storage modulus of conventional silicone rubber shows a small increasing trend with the frequency. However, if silicone oil is selected to be mixed with silicone rubber, the storage modulus increases dramatically when the frequency and strain are both beyond the critical values.

  12. Colloidal Plastic Crystals in a Shear Field.

    PubMed

    Chu, Fangfang; Heptner, Nils; Lu, Yan; Siebenbürger, Miriam; Lindner, Peter; Dzubiella, Joachim; Ballauff, Matthias

    2015-06-01

    We study the structure and viscoelastic behavior of 3D plastic crystals of colloidal dumbbells in an oscillatory shear field based on a combination of small-angle neutron scattering experiments under shear (rheo-SANS) and Brownian dynamics computer simulations. Sterically stabilized dumbbell-shaped microgels are used as hard dumbbell model systems which consist of dumbbell-shaped polystyrene (PS) cores and thermosensitive poly(N-isopropylacrylamide) (PNIPAM) shells. Under increasing shear strain, a discontinuous transition is found from a twinned-fcc-like crystal to a partially oriented sliding-layer phase with a shear-molten state in between. In the novel partially oriented sliding-layer phase, the hard dumbbells exhibit a small but finite orientational order in the shear direction. We find that this weak correlation is sufficient to perturb the nature of the nonequilibrium phase transition as known for hard sphere systems. The discontinuous transition for hard dumbbells is observed to be accompanied by a novel yielding process with two yielding events in its viscoelastic shear response, while only a single yielding event is observed for sheared hard spheres. Our findings will be useful in interpreting the shear response of anisotropic colloidal systems and in generating novel colloidal crystals from anisotropic systems with applications in colloidal photonics. PMID:25635343

  13. Dynamic wetting of shear thinning fluids

    NASA Astrophysics Data System (ADS)

    Seevaratnam, G. K.; Suo, Y.; Ramé, E.; Walker, L. M.; Garoff, S.

    2007-01-01

    The impact of non-Newtonian behavior on dynamic wetting is critical since many fluids exhibit such behavior somewhere in the high-shear environment inherent in the wedge flow near a moving contact line. This impact will be different for two broad categories of non-Newtonian behavior, shear thinning, and elasticity. In this paper, we discuss the steady-state wetting of a fluid, aqueous solutions of xanthan gum, dominated by shear thinning but with negligible elasticity. In the shear thinning fluid, viscous bending near the contact line is greatly reduced compared to a Newtonian fluid having the same zero-shear viscosity. Concomitant with this reduction in viscous bending, the effective dynamic contact angle has a much weaker dependence on capillary number, Ca, than is observed in, or predicted for, Newtonian fluids. A simple lubrication model using a constitutive relation with power-law shear thinning at high shear rates and a Newtonian plateau at low shear rates mimics the trends seen in our data and elucidates the origins of the reduced viscous bending.

  14. Internal and Interface Shear Strength of

    E-print Network

    Zornberg, Jorge G.

    . This report investigates the mechanical behavior of GCLs by providing a state-of-the-art review of internali Internal and Interface Shear Strength of Geosynthetic Clay Liners (GCLs) by John Scott Mc;ii McCartney, John S., Zornberg, Jorge G., and Swan, Jr., Robert H. Internal and Interface Shear

  15. Shear alters motility of Escherichia coli

    NASA Astrophysics Data System (ADS)

    Molaei, Mehdi; Jalali, Maryam; Sheng, Jian

    2013-11-01

    Understanding of locomotion of microorganisms in shear flows drew a wide range of interests in microbial related topics such as biological process including pathogenic infection and biophysical interactions like biofilm formation on engineering surfaces. We employed microfluidics and digital holography microscopy to study motility of E. coli in shear flows. We controlled the shear flow in three different shear rates: 0.28 s-1, 2.8 s-1, and 28 s-1 in a straight channel with the depth of 200 ?m. Magnified holograms, recorded at 15 fps with a CCD camera over more than 20 minutes, are analyzed to obtain 3D swimming trajectories and subsequently used to extract shear responses of E.coli. Thousands of 3-D bacterial trajectories are tracked. The change of bacteria swimming characteristics including swimming velocity, reorientation, and dispersion coefficient are computed directly for individual trajectory and ensemble averaged over thousands of realizations. The results show that shear suppresses the bacterial dispersions in bulk but promote dispersions near the surface contrary to those in quiescent flow condition. Ongoing analyses are focusing to quantify effect of shear rates on tumbling frequency and reorientation of cell body, and its implication in locating the hydrodynamic mechanisms for shear enhanced angular scattering. NIH, NSF, GoMRI.

  16. Shear viscosity of pion gas

    E-print Network

    Eiji Nakano

    2007-03-21

    Using chiral perturbation theory we investigate the QCD shear viscosity ($\\eta $) to entropy density ($s$) ratio below the deconfinement temperature ($\\sim 170$ MeV) with zero baryon number density. It is found that $\\eta /s$ of QCD is monotonically decreasing in temperature ($T$) and reaches 0.6 with estimated $\\sim 50%$ uncertainty at T=120 MeV. A naive extrapolation of the leading order result shows that $\\eta /s$ reaches the $1/4\\pi $ minimum bound proposed by Kovtun, Son, and Starinets using string theory methods at $T\\sim 210$ MeV. This suggests a phase transition or cross over might occur at $T\\lesssim 210$ MeV in order for the bound to remain valid. Also, it is natural for $\\eta /s$ to stay close to the minimum bound around the phase transition temperature as was recently found in heavy ion collisions.

  17. Inverse Magnetic/Shear Catalysis

    E-print Network

    McInnes, Brett

    2015-01-01

    It is well known that very large magnetic fields are generated when the Quark-Gluon Plasma is formed during peripheral heavy-ion collisions. Lattice, holographic, and other studies strongly suggest that these fields may, for observationally relevant field values, induce ``inverse magnetic catalysis'', signalled by a lowering of the critical temperature for the chiral/deconfinement transition. The theoretical basis of this effect has recently attracted much attention; yet so far these investigations have not included another, equally dramatic consequence of the peripheral collision geometry: the QGP acquires a large angular momentum vector, parallel to the magnetic field. Here we use holographic techniques to argue that the angular momentum can also, independently, have an effect on transition temperatures, and we obtain a rough estimate of the relative effects of the presence of both a magnetic field and an angular momentum density. We find that the shearing angular momentum reinforces the effect of the magne...

  18. Tuning graphene properties by shear

    NASA Astrophysics Data System (ADS)

    Concha, Andres; Cheng, Shengfeng; Covaci, Lucian; Mahadevan, L.

    2014-03-01

    Graphene being the thinnest possible membrane made out of carbon atoms is prone to deformations under slight external forcing. Here, we take advantage of this proneness to deformations to manipulate transport properties of graphene ribbons. We analyze the effect on conductance and LDOS of the spontaneous pattern produced when a wide ribbon is subject to shear. The deformation of the ribbon produces pseudo-magnetic fields, scalar potentials, and Fermi velocity renormalization resulting in the modification of transmission properties without the need of an external gate potential. Our proposal paves the way for producing electronic waveguides by using an elastic instability that spans from the nano to macro-scales. AC was partially supported by Conicyt PAI 79112004 and Fondecyt iniciacion 11130075. LC acknowledges individual support from FWO-Vlaanderen.

  19. Magnetoconvection in sheared magnetic fields

    SciTech Connect

    Bian, N. H.; Garcia, O. E.

    2008-10-15

    The development of magnetoconvection in a sheared magnetic field is investigated. The equilibrium magnetic field B{sub 0} is horizontal and its orientation varies linearly along the vertical axis. Preliminary consideration of the transition from the inertial to the viscous regime of the gravitational resistive interchange instability, reveals that the latter is characterized by the existence of viscoresistive boundary layers of vertical width which scales as Q{sup -1/6}, where Q is the Chandrasekhar number. The situation is analogous to the one encountered in magnetically confined laboratory plasmas, where convective flows are constrained by the magnetic shear to develop in boundary layers located around resonant magnetic surfaces in order to fulfill the 'interchange condition'k{center_dot}B{sub 0}=0, where k is the wave vector of the magnetic perturbation. It follows that when the effect of thermal diffusion is taken into account in the process, convection can only occur above a certain critical value of the Rayleigh number which scales as Q{sup 2/3} for large Q. At the onset, the convection pattern is a superposition of identically thin convective rolls everywhere aligned with the local magnetic field lines and which therefore adopt the magnetic field geometry, a situation also reminiscent of the penumbra of sunspots. Using this degeneracy, equations describing the weakly nonlinear state are obtained and discussed. A reduced magnetohydrodynamic description of magnetoconvection is introduced. Since it is valid for arbitrary magnetic field configurations, it allows a simple extension to the case where there exists an inclination between the direction of gravity and the plane spanned by the equilibrium magnetic field. These reduced magnetohydrodynamic equations are proposed as a powerful tool for further investigations of magnetoconvection in more complex field line geometries.

  20. Shear layer excitation, experiment versus theory

    NASA Technical Reports Server (NTRS)

    Bechert, D. W.; Stahl, B.

    1984-01-01

    The acoustical excitation of shear layers is investigated. Acoustical excitation causes the so-called orderly structures in shear layers and jets. Also, the deviations in the spreading rate between different shear layer experiments are due to the same excitation mechanism. Measurements in the linear interaction region close to the edge from which the shear layer is shed are examined. Two sets of experiments (Houston 1981 and Berlin 1983/84) are discussed. The measurements were carried out with shear layers in air using hot wire anemometers and microphones. The agreement between these measurements and the theory is good. Even details of the fluctuating flow field correspond to theoretical predictions, such as the local occurrence of negative phase speeds.

  1. Determining Shear Stress Distribution in a Laminate

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.

    2010-01-01

    A "simplified shear solution" method approximates the through-thickness shear stress distribution within a composite laminate based on an extension of laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather, it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply-level stresses can be efficiently determined from global load resultants at a given location in a structure and used to evaluate the margin of safety on a ply-by-ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. The method has been incorporated within the HyperSizer commercial structural sizing software to improve its predictive capability for designing composite structures. The HyperSizer structural sizing software is used extensively by NASA to design composite structures. In the case of through-thickness shear loading on panels, HyperSizer previously included a basic, industry-standard, method for approximating the resulting shear stress distribution in sandwich panels. However, no such method was employed for solid laminate panels. The purpose of the innovation is to provide an approximation of the through-thickness shear stresses in a solid laminate given the through-thickness shear loads (Qx and Qy) on the panel. The method was needed for implementation within the HyperSizer structural sizing software so that the approximated ply-level shear stresses could be utilized in a failure theory to assess the adequacy of a panel design. The simplified shear solution method was developed based on extending and generalizing bi-material beam theory to plate-like structures. It is assumed that the through-thickness shear stresses arise due to local bending of the laminate induced by the through-thickness shear load, and by imposing equilibrium both vertically and horizontally, the through-thickness shear stress distribution can be calculated. The resulting shear stresses integrate to the applied shear load, are continuous at the ply interfaces, and are zero at the laminate-free surfaces. If both Qx and Qy shear loads are present, it is assumed that they act independently and that their effects can be superposed. The calculated shear stresses can be rotated within each ply to the principal material coordinates for use in a ply-level failure criterion. The novelty of the simplified shear solution method is its simplicity and the fact that it does not require solution of a particular boundary value problem. The advantages of the innovation are that an approximation of the though-thickness shear stress distribution can be quickly determined for any solid laminate or solid laminate region within a stiffened panel.

  2. WEAK LENSING MASS RECONSTRUCTION: FLEXION VERSUS SHEAR

    SciTech Connect

    Pires, S.

    2010-11-10

    Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone should not be used to do convergence map reconstruction, even on small scales.

  3. Particle acceleration efficiencies in astrophysical shear flows

    E-print Network

    F. M. Rieger; P. Duffy

    2005-02-04

    The acceleration of energetic particles in astrophysical shear flows is analyzed. We show that in the presence of a non-relativistic gradual velocity shear, power law particle momentum distributions $f(p) \\propto p^{-(3+\\alpha)}$ may be generated, assuming a momentum-dependent scattering time $\\tau \\propto p^{\\alpha}$, with $\\alpha > 0$. We consider possible acceleration sites in astrophysical jets and study the conditions for efficient acceleration. It is shown, for example, that in the presence of a gradual shear flow and a gyro-dependent particle mean free path, synchrotron radiation losses no longer stop the acceleration once it has started to work efficiently. This suggests that shear acceleration may naturally account for a second, non-thermal population of energetic particles in addition to a shock-accelerated one. The possible relevance of shear acceleration is briefly discussed with reference to the relativistic jet in the quasar 3C 273.

  4. Dynamic Jamming Point for Shear Thickening Suspensions

    NASA Astrophysics Data System (ADS)

    Brown, Eric; Jaeger, Heinrich M.

    2009-08-01

    We report on rheometry measurements to characterize the critical behavior in two model shear thickening suspensions: cornstarch in water and glass spheres in oil. The slope of the shear thickening part of the viscosity curve is found to increase dramatically with packing fraction and diverge at a critical packing fraction ?c. The magnitude of the viscosity and the yield stress are also found to have scalings that diverge at ?c. We observe shear thickening as long as the yield stress is less than the stress at the viscosity maximum. Above this point the suspensions transition to purely shear thinning. Based on these data we present a dynamic jamming phase diagram for suspensions and show that a limiting case of shear thickening corresponds to a jammed state.

  5. Three dimensional fabric evolution of sheared sand

    SciTech Connect

    Hasan, Alsidqi; Alshibli, Khalid

    2012-10-24

    Granular particles undergo translation and rolling when they are sheared. This paper presents a three-dimensional (3D) experimental assessment of fabric evolution of sheared sand at the particle level. F-75 Ottawa sand specimen was tested under an axisymmetric triaxial loading condition. It measured 9.5 mm in diameter and 20 mm in height. The quantitative evaluation was conducted by analyzing 3D high-resolution x-ray synchrotron micro-tomography images of the specimen at eight axial strain levels. The analyses included visualization of particle translation and rotation, and quantification of fabric orientation as shearing continued. Representative individual particles were successfully tracked and visualized to assess the mode of interaction between them. This paper discusses fabric evolution and compares the evolution of particles within and outside the shear band as shearing continues. Changes in particle orientation distributions are presented using fabric histograms and fabric tensor.

  6. Wind energy bibliography

    SciTech Connect

    1995-05-01

    This bibliography is designed to help the reader search for information on wind energy. The bibliography is intended to help several audiences, including engineers and scientists who may be unfamiliar with a particular aspect of wind energy, university researchers who are interested in this field, manufacturers who want to learn more about specific wind topics, and librarians who provide information to their clients. Topics covered range from the history of wind energy use to advanced wind turbine design. References for wind energy economics, the wind energy resource, and environmental and institutional issues related to wind energy are also included.

  7. Wind for Schools (Poster)

    SciTech Connect

    Baring-Gould, I.

    2010-05-01

    As the United States dramatically expands wind energy deployment, the industry is challenged with developing a skilled workforce and addressing public resistance. Wind Powering America's Wind for Schools project addresses these issues by developing Wind Application Centers (WACs) at universities; WAC students assist in implementing school wind turbines and participate in wind courses, by installing small wind turbines at community "host" schools, by implementing teacher training with interactive curricula at each host school. This poster provides an overview of the first two years of the Wind for Schools project, primarily supporting activities in Colorado, Kansas, Nebraska, South Dakota, Montana, and Idaho.

  8. THE SHEARING H I SPIRAL PATTERN OF NGC 1365

    SciTech Connect

    Speights, Jason C.; Westpfahl, David J.

    2011-07-20

    The Tremaine-Weinberg equations are solved for a pattern speed that is allowed to vary with radius. The solution method transforms an integral equation for the pattern speed to a least-squares problem with well-established procedures for statistical analysis. The method applied to the H I spiral pattern of the barred, grand-design galaxy NGC 1365 produces convincing evidence for a radial dependence in the pattern speed. The pattern speed behaves approximately as 1/r and is very similar to the material speed. There are no clear indications of corotation or Lindblad resonances. Tests show that the results are not selection biased, and that the method is not measuring the material speed. Other methods of solving the Tremaine-Weinberg equations for shearing patterns are found to produce results in agreement with those obtained using the current method. Previous estimates that relied on the assumptions of the density-wave interpretation of spiral structure are inconsistent with the results obtained using the current method. The results are consistent with spiral structure theories that allow for shearing patterns, and contradict fundamental assumptions in the density-wave interpretation that are often used for finding spiral arm pattern speeds. The spiral pattern is winding on a characteristic timescale of {approx}500 Myr.

  9. Dual shear wave induced laser speckle contrast signal and the improvement in shear wave speed measurement.

    PubMed

    Li, Sinan; Cheng, Yi; Eckersley, Robert J; Elson, Daniel S; Tang, Meng-Xing

    2015-06-01

    Shear wave speed is quantitatively related to tissue viscoelasticity. Previously we reported shear wave tracking at centimetre depths in a turbid optical medium using laser speckle contrast detection. Shear wave progression modulates displacement of optical scatterers and therefore modulates photon phase and changes the laser speckle patterns. Time-resolved charge-coupled device (CCD)-based speckle contrast analysis was used to track shear waves and measure the time-of-flight of shear waves for speed measurement. In this manuscript, we report a new observation of the laser speckle contrast difference signal for dual shear waves. A modulation of CCD speckle contrast difference was observed and simulation reproduces the modulation pattern, suggesting its origin. Both experimental and simulation results show that the dual shear wave approach generates an improved definition of temporal features in the time-of-flight optical signal and an improved signal to noise ratio with a standard deviation less than 50% that of individual shear waves. Results also show that dual shear waves can correct the bias of shear wave speed measurement caused by shear wave reflections from elastic boundaries. PMID:26114021

  10. Validity of Measurement of Shear Modulus by Ultrasound Shear Wave Elastography in Human Pennate Muscle

    PubMed Central

    Miyamoto, Naokazu; Hirata, Kosuke; Kanehisa, Hiroaki; Yoshitake, Yasuhide

    2015-01-01

    Ultrasound shear wave elastography is becoming a valuable tool for measuring mechanical properties of individual muscles. Since ultrasound shear wave elastography measures shear modulus along the principal axis of the probe (i.e., along the transverse axis of the imaging plane), the measured shear modulus most accurately represents the mechanical property of the muscle along the fascicle direction when the probe’s principal axis is parallel to the fascicle direction in the plane of the ultrasound image. However, it is unclear how the measured shear modulus is affected by the probe angle relative to the fascicle direction in the same plane. The purpose of the present study was therefore to examine whether the angle between the principal axis of the probe and the fascicle direction in the same plane affects the measured shear modulus. Shear modulus in seven specially-designed tissue-mimicking phantoms, and in eleven human in-vivo biceps brachii and medial gastrocnemius were determined by using ultrasound shear wave elastography. The probe was positioned parallel or 20° obliquely to the fascicle across the B-mode images. The reproducibility of shear modulus measurements was high for both parallel and oblique conditions. Although there was a significant effect of the probe angle relative to the fascicle on the shear modulus in human experiment, the magnitude was negligibly small. These findings indicate that the ultrasound shear wave elastography is a valid tool for evaluating the mechanical property of pennate muscles along the fascicle direction. PMID:25853777

  11. Dual shear wave induced laser speckle contrast signal and the improvement in shear wave speed measurement

    PubMed Central

    Li, Sinan; Cheng, Yi; Eckersley, Robert J; Elson, Daniel S; Tang, Meng-Xing

    2015-01-01

    Shear wave speed is quantitatively related to tissue viscoelasticity. Previously we reported shear wave tracking at centimetre depths in a turbid optical medium using laser speckle contrast detection. Shear wave progression modulates displacement of optical scatterers and therefore modulates photon phase and changes the laser speckle patterns. Time-resolved charge-coupled device (CCD)-based speckle contrast analysis was used to track shear waves and measure the time-of-flight of shear waves for speed measurement. In this manuscript, we report a new observation of the laser speckle contrast difference signal for dual shear waves. A modulation of CCD speckle contrast difference was observed and simulation reproduces the modulation pattern, suggesting its origin. Both experimental and simulation results show that the dual shear wave approach generates an improved definition of temporal features in the time-of-flight optical signal and an improved signal to noise ratio with a standard deviation less than 50% that of individual shear waves. Results also show that dual shear waves can correct the bias of shear wave speed measurement caused by shear wave reflections from elastic boundaries. PMID:26114021

  12. Shear Senses and Viscous Dissipation of Layered Ductile Simple Shear Zones

    NASA Astrophysics Data System (ADS)

    Mulchrone, Kieran F.; Mukherjee, Soumyajit

    2015-10-01

    Velocity profiles and shear heat profiles for inclined, layered Newtonian simple shear zones are considered. Reverse fault-like simple shear of the boundaries and upward net pressure gradient act together in such shear zones. As the velocity of the boundary increases, the point of highest velocity shifts from the lower layer of less viscosity into the upper layer. The shear heat profile shows a temperature peak inside the lower layer. For a more viscous upper layer, the point of highest velocity is located inside the upper layer and shifts towards the upper boundary of the shear zone. The shear heat profile shows a maximum temperature within the upper layer. Depending on the flow parameters of the two layers, the slip rate of the boundary, and the dip and thickness of the shear zone, a shear sense in reverse to the relative movement of the shear zone boundaries may develop. These models can decipher thermo-kinematics of layered shear zones in plate-scale hot orogens.

  13. Reversible shear thickening at low shear rates of electrorheological fluids under electric fields

    NASA Astrophysics Data System (ADS)

    Tian, Yu; Zhang, Minliang; Jiang, Jile; Pesika, Noshir; Zeng, Hongbo; Israelachvili, Jacob; Meng, Yonggang; Wen, Shizhu

    2011-01-01

    By shearing electrorheological (ER) fluids between two concentric cylinders, we show a reversible shear thickening of ER fluids above a low critical shear rate (<1 s-1) and a high critical electric field strength (>100 V/mm), which can be characterized by a critical apparent viscosity. Shear thickening and electrostatic particle interaction-induced interparticle friction forces are considered to play an important role in the origin of lateral shear resistance of ER fluids, while the applied electric field controls the extent of shear thickening. The electric-field-controlled reversible shear thickening has implications for high-performance electrorheological -magnetorheological fluid design, clutch fluids with high friction forces triggered by applying a local electric field, other field-responsive materials, and intelligent systems.

  14. Reversible shear thickening at low shear rates of electrorheological fluids under electric fields.

    PubMed

    Tian, Yu; Zhang, Minliang; Jiang, Jile; Pesika, Noshir; Zeng, Hongbo; Israelachvili, Jacob; Meng, Yonggang; Wen, Shizhu

    2011-01-01

    By shearing electrorheological (ER) fluids between two concentric cylinders, we show a reversible shear thickening of ER fluids above a low critical shear rate (<1?s(-1)) and a high critical electric field strength (>100 V/mm), which can be characterized by a critical apparent viscosity. Shear thickening and electrostatic particle interaction-induced interparticle friction forces are considered to play an important role in the origin of lateral shear resistance of ER fluids, while the applied electric field controls the extent of shear thickening. The electric-field-controlled reversible shear thickening has implications for high-performance electrorheological-magnetorheological fluid design, clutch fluids with high friction forces triggered by applying a local electric field, other field-responsive materials, and intelligent systems. PMID:21405692

  15. Relation between ordering and shear thinning in colloidal suspensions

    E-print Network

    Xu, Xinliang

    Colloidal suspensions exhibit shear thinning and shear thickening. The most common interpretation of these phenomena identifies layering of the fluid perpendicular to the shear gradient as the driver for the observed ...

  16. The effect of the arbitrary level assignment of satellite cloud motion wind vectors on wind analyses in the pre-thunderstorm environment

    NASA Technical Reports Server (NTRS)

    Peslen, C. A.; Koch, S. E.; Uccellini, L. W.

    1986-01-01

    The impact of satellite-derived cloud motion vectors on SESAME rawinsonde wind fields was studied in two separate cases. The effect of wind and moisture gradients on the arbitrary assignment of the satellite data is assessed to coordinate surfaces in a severe storm environment marked by strong vertical wind shear. Objective analyses of SESAME rawinsonde winds and combined winds are produced and differences between these two analyzed fields are used to make an assessment of coordinate level choice. It is shown that the standard method of arbitrarily assigning wind vectors to a low level coordinate surface yields systematic differences between the rawinsonde and combined wind analyses. Arbitrary assignment of cloud motions to the 0.9 sigma surface produces smaller differences than assignment to the 825 mb pressure surface. Systematic differences occur near moisture discontinuities and in regions of horizontal and vertical wind shears. The differences between the combined and SESAME wind fields are made smallest by vertically interpolating cloud motions to either a pressure or sigma surface.

  17. The effect of the arbitrary level assignment of satellite cloud motion wind vectors on wind analyses in the pre-thunderstorm environment

    NASA Technical Reports Server (NTRS)

    Peslen, C. A.; Koch, S. E.; Uccellini, L. W.

    1985-01-01

    The impact of satellite-derived cloud motion vectors on SESAME rawinsonde wind fields was studied in two separate cases. The effect of wind and moisture gradients on the arbitrary assignment of the satellite data is assessed to coordinate surfaces in a severe storm environment marked by strong vertical wind shear. Objective analyses of SESAME rawinsonde winds and combined winds are produced and differences between these two analyzed fields are used to make an assessment of coordinate level choice. It is shown that the standard method of arbitrarily assigning wind vectors to a low level coordinate surface yields systematic differences between the rawinsonde and combined wind analyses. Arbitrary assignment of cloud motions to the 0.9 sigma surface produces smaller differences than assignment to the 825 mb pressure surface. Systematic differences occur near moisture discontinuities and in regions of horizontal and vertical wind shears. The differences between the combined and SESAME wind fields are made smallest by vertically interpolating cloud motions to either a pressure or sigma surface.

  18. Characterization of winds through the rotor plane using a phased array SODAR and recommendations for future work.

    SciTech Connect

    Deola, Regina Anne

    2010-02-01

    Portable remote sensing devices are increasingly needed to cost effectively characterize the meteorology at a potential wind energy site as the size of modern wind turbines increase. A short term project co-locating a Sound Detection and Ranging System (SODAR) with a 200 meter instrumented meteorological tower at the Texas Tech Wind Technology Field Site was performed to collect and summarize wind information through an atmospheric layer typical of utility scale rotor plane depths. Data collected identified large speed shears and directional shears that may lead to unbalanced loads on the rotors. This report identifies suggestions for incorporation of additional data in wind resource assessments and a few thoughts on the potential for using a SODAR or SODAR data to quantify or investigate other parameters that may be significant to the wind industry.

  19. Controls of dust emission fluxes and wind erosion threshold on a wet playa

    NASA Astrophysics Data System (ADS)

    Wiggs, G.; King, J.; Thomas, D. S.; Washington, R.

    2012-12-01

    The control of dust emissions from crusted surfaces is both highly variable and difficult to measure directly. Seasonal changes in moisture availability, temperature, evaporation, surface roughness, and sediment supply result in a highly complex surface condition that remains to be fully described in the context of wind erosion potential. A highly intensive project on Sua Pan, Botswana using the PI-SWERL (portable wind tunnel) combined with surface measurements of crust and soil properties has led to a new understanding of the controls on wind erosion from these surfaces. The PI-SWERL is a highly portable wind tunnel that applies a wind shear to the surface using a motor-controlled rotating annular blade and measures resulting dust emissions with a DustTrak dust monitor. We undertook a sequence of tests with the PI-SWERL to obtain both the wind erosion threshold (using a slowly increasing shear velocity) and a dust emission flux (using a constant shear velocity) across a 12 km by 12 km grid across the pan surface. A total of just under 1000 wind tunnel tests and 2000 correlated measurements of a variety of surface properties including crust thickness, surface and subsurface soil moisture, shearing strength (shear vane), normal stress resistance (penetrometer), and surface roughness were conducted in August 2011. These results show that wind erosion potential is best described by measurements of normal stress resistance rather than shearing strength at low dust emission fluxes, but despite their frequent use in wind erosion studies of crusted surfaces neither metric provided a good explanation of higher dust emission fluxes. Surface soil moisture explained the most variation in both dust emissions and wind erosion threshold although much variation remains unexplained. Our results suggested that combining measurements of surface roughness, soil moisture, and crust thickness provided a reasonable explanation of wind erosion potential on the salt pan surface. As pan surfaces can exhibit a range of aerodynamic roughness lengths over three orders of magnitude the small-scale partition of wind stress could be considered. Surface soil moisture also had a very large range in which a relatively sharp threshold was found to increase dust emissions when combined with other surface factors. Although the role of surface moisture in dust emissions is understood it remains a very difficult (yet critical) parameter to measure and a call for more precise estimations of this metric is highly encouraged.

  20. Numerical modeling of the wind flow over a transverse dune

    PubMed Central

    Araújo, Ascânio D.; Parteli, Eric J. R.; Pöschel, Thorsten; Andrade, José S.; Herrmann, Hans J.

    2013-01-01

    Transverse dunes, which form under unidirectional winds and have fixed profile in the direction perpendicular to the wind, occur on all celestial objects of our solar system where dunes have been detected. Here we perform a numerical study of the average turbulent wind flow over a transverse dune by means of computational fluid dynamics simulations. We find that the length of the zone of recirculating flow at the dune lee — the separation bubble — displays a surprisingly strong dependence on the wind shear velocity, u*: it is nearly independent of u* for shear velocities within the range between 0.2?m/s and 0.8?m/s but increases linearly with u* for larger shear velocities. Our calculations show that transport in the direction opposite to dune migration within the separation bubble can be sustained if u* is larger than approximately 0.39?m/s, whereas a larger value of u* (about 0.49?m/s) is required to initiate this reverse transport. PMID:24091456

  1. Numerical modeling of the wind flow over a transverse dune

    E-print Network

    Ascânio D. Araújo; Eric J. R. Parteli; Thorsten Poeschel; José S. Andrade Jr.; Hans J. Herrmann

    2013-09-30

    Transverse dunes, which form under unidirectional winds and have fixed profile in the direction perpendicular to the wind, occur on all celestial objects of our solar system where dunes have been detected. Here we perform a numerical study of the average turbulent wind flow over a transverse dune by means of computational fluid dynamics simulations. We find that the length of the zone of recirculating flow at the dune lee --- the {\\em{separation bubble}} --- displays a surprisingly strong dependence on the wind shear velocity, $u_{\\ast}$: it is nearly independent of $u_{\\ast}$ for shear velocities within the range between $0.2\\,$m$$s and $0.8\\,$m$$s but increases linearly with $u_{\\ast}$ for larger shear velocities. Our calculations show that transport in the direction opposite to dune migration within the separation bubble can be sustained if $u_{\\ast}$ is larger than approximately $0.39\\,$m$$s, whereas a larger value of $u_{\\ast}$ (about $0.49\\,$m$$s) is required to initiate this reverse transport.

  2. Periodic Viscous Shear Heating Instability in Fine-Grained Shear Zones: Mechanism for Intermediate Depth Earthquakes

    NASA Astrophysics Data System (ADS)

    Coon, E.; Kelemen, P.; Hirth, G.; Spiegelman, M.

    2005-12-01

    Kelemen and Hirth (Fall 2004 AGU) presented a model for periodic, viscous shear heating instabilities along pre-existing, fine grained shear zones. This provides an attractive alternative to dehydration embrittlement for explaining intermediate-depth earthquakes, especially those in a narrow thermal window within the mantle section of subducting oceanic plates (Hacker et al JGR03). Ductile shear zones with widths of cm to m are common in shallow mantle massifs and peridotite along oceanic fracture zones. Pseudotachylites in a mantle shear zone show that shear heating temperatures exceeded the mantle solidus (Obata & Karato Tectonophys95). Olivine grain growth in shear zones is pinned by closely spaced pyroxenes; thus, once formed, these features do not `heal' on geological time scales in the absence of melt or fluid (Warren & Hirth EPSL05). Grain-size sensitive creep will be localized within these shear zones, in preference to host rocks with olivine grain size from 1 to 10 mm. Inspired by the work of Whitehead & Gans (GJRAS74), we proposed that such pre-existing shear zones might undergo repeated shear heating instabilities. This is not a new concept; what is new is that viscous deformation is limited to a narrow shear zone, because grain boundary sliding, sensitive to both stress and grain size, may accommodate creep even at high stress and high temperature. These new ideas yield a new result: simple models for a periodic shear heating instability. Last year, we presented a 1D numerical model using olivine flow laws, assuming that viscous deformation remains localized in shear zones, surrounded by host rocks undergoing elastic deformation. Stress evolves due to elastic strain and drives viscous deformation in a shear zone of specified width. Shear heating and thermal diffusion control T. A maximum of 1400 C (substantial melting of peridotite ) was imposed. Grain size evolves due to recrystallization and diffusion. For strain rates of E-13 to E-14 per sec and initial T of 600 to 850 C, this produced periodic viscous shear heating events with periods of 100's to 1000's of years. Strain rates during these events approach 1 per second as temperatures reach 1400. Cooling between events returns the shear zone almost to its initial temperature, though ultimately shear zone temperature between events exceeds 850 C resulting in stable viscous creep. Analysis shows that our system of equations jumps from one steady state to another, depending on a non-dimensional number relating the rate of shear heating to the rate of diffusive cooling. This year, Kelemen and Hirth show that the rate of stress drop during shear heating events is greater than the rate of elastic stress relaxation, so that shear heating events are a runaway instability. Rather than capping the temperature at 1400 C, we parameterize melt fraction as a function of T, and shear viscosity as a function of melt fraction. A problem with our 1D model is that predicted displacements are too large (1 to 20 m) during shear heating events, essentially because there is no resistance at shear zone ends. To address this, Coon and Spiegelman have embarked on a 3D model, incorporating a pre-existing fine-grained, tabular shear zone of finite extent, with a visco-elastic rheology for both shear zone and wall rocks. Preliminary 1D models using this approach show that the more complicated rheology yields the same result as the simpler model. We will present preliminary results, and determine the Maxwell time for this problem, since low strain rates could produce viscous relaxation in both shear zone and wall rocks with negligible shear heating.

  3. Streamwise development of the wind turbine boundary layer over a model wind turbine array

    NASA Astrophysics Data System (ADS)

    Newman, Jensen; Lebron, Jose; Meneveau, Charles; Castillo, Luciano

    2013-08-01

    The streamwise development of turbulence statistics and mean kinetic energy in a model wind farm consisting of 3 × 5 wind turbines is studied experimentally in a wind tunnel. The analysis uses planar Particle Image Velocimetry data obtained at the centerline plane of the wind farm, covering the inflow as well as four planes in between five downstream wind turbines. The data analysis is organized by dividing these measurement planes into three regions: the above-rotor, rotor-swept, and below-rotor regions. For each field, flow development is quantified using a properly defined relative difference norm based on an integration over each of the regions. Using this norm, it is found that the mean streamwise velocity approaches a fully developed state most rapidly, whereas the flow development is more gradual for the second-order statistics. The vertical entrainment flux of the mean kinetic energy by the Reynolds shear stress, ?U??u'v'?, is observed to develop at a rate similar to that of the Reynolds shear stress rather than the mean streamwise velocity component. Its development is slowest in the layer nearest to the ground. Analysis of various terms in the mean kinetic energy equation shows that the wind turbine boundary layer has not yet reached fully developed conditions by the fifth turbine but that it is approaching such conditions. By comparing the vertical entrainment flux with the horizontal flux due to the mean flow, it is found that the former increases, whereas the latter decreases, as function of downstream distance, but that the former is already an important contributor in the developing region.

  4. A hydrodynamical model of shear flow over semi-infinite barriers with application to density currents

    SciTech Connect

    Shapiro, A. )

    1992-12-01

    Vertically sheared airflow over semi-infinite barriers is investigated with a simple hydrodynamical model. The idealized flow is steady, two-dimensional, neutrally buoyant, and inviscid, bounded on the bottom by a semi-infinite impermeable barrier and on the top by a rigid tropopause lid. With attention further restricted to an exponentially decreasing wind shear, the equations of motion (Euler's equations) reduce, without approximation, to a modified Poisson equation for a pseudo streamfunction and a formula for the Exner function. The free parameters characterizing the model's environment are the tropopause height, the density scale height, the wind speed at ground level, and the wind speed at tropopause level. Additional parameters characterize the barrier geometry. Exact solutions of the equations of motion are obtained for semi-infinite plateau barriers and for a barrier qualitatively resembling the shallow density current associated with some thunderstorm outflows. These solutions are noteworthy in that the reduction of a certain nondimensional shear parameter (through negative values) results in greater vertical parcel displacements over the barrier despite a corresponding reduction in the vertical velocity. This steepening tendency culminates in overturning motions associated with both upstream and down-stream steering levels. In this latter case the low-level inflow impinging on the barrier participates in a mixed jump and overturning updraft reminiscent of updrafts simulated in numerical convective models. Conversely, for large values of the nondimensional shear parameter, parcels undergo small vertical parcel displacements over the barrier despite large vertical velocities. This latter behavior may account for the finding that strong convergence along the leading edge of storm outflows does not always trigger deep convection even in unstable environments.

  5. Impact response of shear thickening suspensions

    NASA Astrophysics Data System (ADS)

    Brown, Eric; Ozgen, Oktar; Kallmann, Marcelo; Allen, Benjamin

    2013-11-01

    Dense suspensions of hard particles such as cornstarch in water exhibit shear thickening, in which the energy dissipation rate under shear dramatically increases with increasing shear rate. Recent work has established that in steady-state shear this phenomena is a result of a dynamic jamming of the particles in suspension. Several dynamic phenomena observed in such suspensions have long been assumed to be a consequence of this shear thickening; strong impact resistance, the ability of a person to run on the fluid surface, fingering and hole instabilities under vibration, and oscillations in the speed of sinking of an object in the fluid. However, I will present results of experiments consisting of an indenter impacting a dense suspension which demonstrate that the strong impact resistance cannot be explained by existing models for steady-state shear thickening. I will show these dynamic phenomena can be reproduced by graphical simulations based on a minimal phenomenological model in which the fluid has a stiffness with a dependence on velocity history. These and other recent results suggest a need for new models to understand the dynamic phenomena associated with shear thickening fluids.

  6. Emergency wind erosion control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    February through May is the critical time for wind erosion in Kansas, but wind erosion can happen any time when high winds occur on smooth, wide fields with low vegetation and poor soil structure. The most effective wind erosion control is to ensure a protective cover of residue or growing crop thro...

  7. Global Wind Map

    ERIC Educational Resources Information Center

    Journal of College Science Teaching, 2005

    2005-01-01

    This brief article describes a new global wind-power map that has quantified global wind power and may help planners place turbines in locations that can maximize power from the winds and provide widely available low-cost energy. The researchers report that their study can assist in locating wind farms in regions known for strong and consistent…

  8. Shear Viscosity from Effective Couplings of Gravitons

    E-print Network

    Rong-Gen Cai; Zhang-Yu Nie; Ya-Wen Sun

    2008-12-12

    We calculate the shear viscosity of field theories with gravity duals using Kubo-formula by calculating the Green function of dual transverse gravitons and confirm that the value of the shear viscosity is fully determined by the effective coupling of transverse gravitons on the horizon. We calculate the effective coupling of transverse gravitons for Einstein and Gauss-Bonnet gravities coupled with matter fields, respectively. Then we apply the resulting formula to the case of AdS Gauss-Bonnet gravity with $F^4$ term corrections of Maxwell field and discuss the effect of $F^4$ terms on the ratio of the shear viscosity to entropy density.

  9. Modeling of shear localization in materials

    SciTech Connect

    Lesuer, D.; LeBlanc, M.; Riddle, B.; Jorgensen, B.

    1998-02-11

    The deformation response of a Ti alloy, Ti-6Al-4V, has been studied during shear localization. The study has involved well-controlled laboratory tests involving a double-notch shear sample. The results have been used to provide a comparison between experiment and the predicted response using DYNA2D and two material models (the Johnson-Cook model and an isotropic elastic-plastic-hydrodynamic model). The work will serve as the basis for the development of a new material model which represents the different deformation mechanisms active during shear localization.

  10. Time accurate simulations of compressible shear flows

    NASA Technical Reports Server (NTRS)

    Givi, Peyman; Steinberger, Craig J.; Vidoni, Thomas J.; Madnia, Cyrus K.

    1993-01-01

    The objectives of this research are to employ direct numerical simulation (DNS) to study the phenomenon of mixing (or lack thereof) in compressible free shear flows and to suggest new means of enhancing mixing in such flows. The shear flow configurations under investigation are those of parallel mixing layers and planar jets under both non-reacting and reacting nonpremixed conditions. During the three-years of this research program, several important issues regarding mixing and chemical reactions in compressible shear flows were investigated.

  11. A magnetorheological elastomer compressive and shear sensor

    NASA Astrophysics Data System (ADS)

    Ghafoorianfar, Nima; Gordaninejad, Faramarz

    2015-04-01

    A magnetorheological elastomer (MRE)-based wireless sensor is designed, developed and tested, which is capable of sensing compression and shear forces. The MRE wireless sensor system consists of a disk-shape MRE sample with two thin steel electrodes attached to both sides and two wires connected to electrodes. Electrical resistance of MRE sensor samples changes due to piezoresistance behavior of MRE as various axial and shear stresses are applied. Electrical resistance decreases as the applied compressive axial forces increases, on the other hand, the electrical resistance increases as the applied shear force increases. Different MRE sensor configurations are evaluated for design optimization.

  12. Buoyancy and shear characteristics of hurricane-tornado environments

    NASA Technical Reports Server (NTRS)

    Mccaul, Eugene W., Jr.

    1991-01-01

    This study presents detailed composite profiles of temperature, moisture, and wind constructed for tornado environments in tropical cyclones that affected the U.S. between 1948 and 1986. Winds are composited in components radial and tangential to the tropical cyclone center at observation time. Guided by observed patterns of tornado occurrence, composites are constructed for a variety of different stratifications of the data, including proximity to tornadoes, position relative to the cyclone center, time of day, time after cyclone landfall, cyclone translation speed, and landfall location. The composites are also compared to composite soundings from Great Plains tornado environments. A variety of sounding parameters are examined to see which are most closely related to the tornado distribution patterns. Lower-tropospheric vertical shears are found to be stronger in the tropical cyclone tornado environments than on the Great Plains. Buoyancy for the tropical cyclone tornado cases is much smaller than that seen with Great Plains tornado events and exhibits a weak negative correlation with tornado outbreak severity.

  13. The gust-front detection and wind-shift algorithms for the Terminal Doppler Weather Radar system

    NASA Technical Reports Server (NTRS)

    Hermes, Laurie G.; Witt, Arthur; Smith, Steven D.; Klingle-Wilson, Diana; Morris, Dale; Stumpf, Gregory J.; Eilts, Michael D.

    1993-01-01

    The Federal Aviation Administration's (FAA) Terminal Doppler Weather Radar (TDWR) system was primarily designed to address the operational needs of pilots in the avoidance of low-altitude wind shears upon takeoff and landing at airports. One of the primary methods of wind-shear detection for the TDWR system is the gust-front detection algorithm. The algorithm is designed to detect gust fronts that produce a wind-shear hazard and/or sustained wind shifts. It serves the hazard warning function by providing an estimate of the wind-speed gain for aircraft penetrating the gust front. The gust-front detection and wind-shift algorithms together serve a planning function by providing forecasted gust-front locations and estimates of the horizontal wind vector behind the front, respectively. This information is used by air traffic managers to determine arrival and departure runway configurations and aircraft movements to minimize the impact of wind shifts on airport capacity. This paper describes the gust-front detection and wind-shift algorithms to be fielded in the initial TDWR systems. Results of a quantitative performance evaluation using Doppler radar data collected during TDWR operational demonstrations at the Denver, Kansas City, and Orlando airports are presented. The algorithms were found to be operationally useful by the FAA airport controllers and supervisors.

  14. Inverse Magnetic/Shear Catalysis

    E-print Network

    Brett McInnes

    2015-11-17

    It is well known that very large magnetic fields are generated when the Quark-Gluon Plasma is formed during peripheral heavy-ion collisions. Lattice, holographic, and other studies strongly suggest that these fields may, for observationally relevant field values, induce ``inverse magnetic catalysis'', signalled by a lowering of the critical temperature for the chiral/deconfinement transition. The theoretical basis of this effect has recently attracted much attention; yet so far these investigations have not included another, equally dramatic consequence of the peripheral collision geometry: the QGP acquires a large angular momentum vector, parallel to the magnetic field. Here we use holographic techniques to argue that the angular momentum can also, independently, have an effect on transition temperatures, and we obtain a rough estimate of the relative effects of the presence of both a magnetic field and an angular momentum density. We find that the shearing angular momentum reinforces the effect of the magnetic field at low values of the baryonic chemical potential, but that it can actually decrease that effect at high chemical potentials

  15. Simplified Shear Solution for Determination of the Shear Stress Distribution in a Composite Panel from the Applied Shear Resultant

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.; Collier, Craig S.

    2008-01-01

    The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate or panel based on laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load resultants (as determined, for instance, by finite element analysis) at a given location in a structure and used to evaluate the margin of safety on a ply by ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. Comparisons to existing theories are made for a variety of laminates, and design examples are provided illustrating the use of the method for determining through-thickness shear stress margins in several types of composite panels and in the context of a finite element structural analysis.

  16. Determination of the Shear Stress Distribution in a Laminate from the Applied Shear Resultant--A Simplified Shear Solution

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.

    2007-01-01

    The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate based on laminated beam theory. The method does not consider the solution of a particular boundary value problem, rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load resultants (as determined, for instance, by finite element analysis) at a given location in a structure and used to evaluate the margin of safety on a ply by ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. Comparisons to existing theories are made for a variety of laminates, and design examples are provided illustrating the use of the method for determining through-thickness shear stress margins in several types of composite panels and in the context of a finite element structural analysis.

  17. Wind power. [electricity generation

    NASA Technical Reports Server (NTRS)

    Savino, J. M.

    1975-01-01

    A historical background on windmill use, the nature of wind, wind conversion system technology and requirements, the economics of wind power and comparisons with alternative systems, data needs, technology development needs, and an implementation plan for wind energy are presented. Considerable progress took place during the 1950's. Most of the modern windmills feature a wind turbine electricity generator located directly at the top of their rotor towers.

  18. Wind Resource Maps (Postcard)

    SciTech Connect

    Not Available

    2011-07-01

    The U.S. Department of Energy's Wind Powering America initiative provides high-resolution wind maps and estimates of the wind resource potential that would be possible from development of the available windy land areas after excluding areas unlikely to be developed. This postcard is a marketing piece that stakeholders can provide to interested parties; it will guide them to Wind Powering America's online wind energy resource maps.

  19. Wind Power Outlook 2004

    SciTech Connect

    anon.

    2004-01-01

    The brochure, expected to be updated annually, provides the American Wind Energy Association's (AWAE's) up-to-date assessment of the wind industry. It provides a summary of the state of wind power in the U.S., including the challenges and opportunities facing the industry. It provides summary information on the growth of the industry, policy-related factors such as the federal wind energy production tax credit status, comparisons with natural gas, and public views on wind energy.

  20. An Icelandic wind atlas

    NASA Astrophysics Data System (ADS)

    Nawri, Nikolai; Nína Petersen, Gudrun; Bjornsson, Halldór; Arason, Þórður; Jónasson, Kristján

    2013-04-01

    While Iceland has ample wind, its use for energy production has been limited. Electricity in Iceland is generated from renewable hydro- and geothermal source and adding wind energy has not be considered practical or even necessary. However, adding wind into the energy mix is becoming a more viable options as opportunities for new hydro or geothermal power installation become limited. In order to obtain an estimate of the wind energy potential of Iceland a wind atlas has been developed as a part of the Nordic project "Improved Forecast of Wind, Waves and Icing" (IceWind). The atlas is based on mesoscale model runs produced with the Weather Research and Forecasting (WRF) Model and high-resolution regional analyses obtained through the Wind Atlas Analysis and Application Program (WAsP). The wind atlas shows that the wind energy potential is considerable. The regions with the strongest average wind are nevertheless impractical for wind farms, due to distance from road infrastructure and power grid as well as harsh winter climate. However, even in easily accessible regions wind energy potential in Iceland, as measured by annual average power density, is among the highest in Western Europe. There is a strong seasonal cycle, with wintertime power densities throughout the island being at least a factor of two higher than during summer. Calculations show that a modest wind farm of ten medium size turbines would produce more energy throughout the year than a small hydro power plants making wind energy a viable additional option.

  1. Electrostatic ion cyclotron velocity shear instability

    NASA Technical Reports Server (NTRS)

    Lemons, D. S.; Winske, D.; Gary, S. P.

    1992-01-01

    A local electrostatic dispersion equation is derived for a shear flow perpendicular to an ambient magnetic field, which includes all kinetic effects and involves only one important parameter. The dispersion equation is cast in the form of Gordeyev integrals and is solved numerically. Numerical solutions indicate that an ion cyclotron instability is excited. The instability occurs roughly at multiples of the ion cyclotron frequency (modified by the shear), with the growth rate or the individual harmonics overlapping in the wavenumber. At large values of the shear parameter, the instability is confined to long wavelengths, but at smaller shear, a second distinct branch at shorter wavelengths also appears. The properties of the instability obtained are compared with those obtained in the nonlocal limit by Ganguli et al. (1985, 1988).

  2. Mesoscale Elucidation of Biofilm Shear Behavior

    E-print Network

    Barai, Pallab; Mukherjee, Partha P

    2015-01-01

    Formation of bacterial colonies as biofilm on the surface/interface of various objects has the potential to impact not only human health and disease but also energy and environmental considerations. Biofilms can be regarded as soft materials, and comprehension of their shear response to external forces is a key element to the fundamental understanding. A mesoscale model has been presented in this article based on digitization of a biofilm microstructure. Its response under externally applied shear load is analyzed. Strain stiffening type behavior is readily observed under high strain loads due to the unfolding of chains within soft polymeric substrate. Sustained shear loading of the biofilm network results in strain localization along the diagonal direction. Rupture of the soft polymeric matrix can potentially reduce the intercellular interaction between the bacterial cells. Evolution of stiffness within the biofilm network under shear reveals two regions: a) initial increase in stiffness due to strain stiffe...

  3. Immiscible blend morphology after shear and elongation

    NASA Astrophysics Data System (ADS)

    Batch, Gibson L.; Trifkovic, Milana; Hedegaard, Aaron; Macosko, Christopher W.

    2015-05-01

    This work examines the role of shear and extensional strain on immiscible blend morphology, namely domain size, orientation, and co-continuity. The domain size reduces with surface tension similar to what is observed with isolated droplets. The domain size is shown to increase with shear strain due to coalescence. Hence the best mixing is found with low shear strains, i.e. low rates of shear and short durations of time. Extensional strain (extrusion draw ratio DR) reduces phase width and thickness with a DR-0.5 dependence, suggesting the transformation to a fibrilar morphology. The critical draw ratio for morphology transformation is approximately 7, in agreement with observations by Grace for droplet breakup in elongation. Fibrilar morphology is also consistent with a large increase in strain-to-break in the drawn film and with observed creep and optical scattering behavior.

  4. Influence of magnetic shear on impurity transport

    SciTech Connect

    Nordman, H.; Fueloep, T.; Candy, J.; Strand, P.; Weiland, J.

    2007-05-15

    The magnetic shear dependence of impurity transport in tokamaks is studied using a quasilinear fluid model for ion temperature gradient (ITG) and trapped electron (TE) mode driven turbulence in the collisionless limit and the results are compared with nonlinear gyrokinetic results using GYRO [J. Candy and R. E. Waltz, J. Comput. Phys 186, 545 (2003)]. It is shown that the impurity transport is sensitive to the magnetic shear, in particular for weak, negative, and large positive shear where a strong reduction of the effective impurity diffusivity is obtained. The fluid and gyrokinetic results are in qualitative agreement, with the gyrokinetic diffusivities typically a factor 2 larger than the fluid diffusivities. The steady state impurity profiles in source-free plasmas are found to be considerably less peaked than the electron density profiles for moderate shear. Comparisons between anomalous and neoclassical transport predictions are performed for ITER-like profiles [R. Aymar, P. Barabaschi, and Y. Shimomura, Plasma Phys. Controlled Fusion 44, 519 (2002)].

  5. The effect of shear on neurodegeneration 

    E-print Network

    Triyoso, Dina Handayani

    1998-01-01

    induced neurodegeneration was established in order to elucidate the mechanism of neurodegeneration in glaucomas hydrocephalus and head injury. The model consisted of a differentiated human neuroblastoma cell line, SH-SY5Y, which was exposed to shear...

  6. Shear lag in truss core sandwich beams

    E-print Network

    Roberts, Ryan (Ryan M.)

    2005-01-01

    An experimental study was conducted to investigate the possible influence of shear lag in the discrepancy between the theoretical and measured stiffness of truss core sandwich beams. In previous studies, the measured values ...

  7. Shear Flow induced Electrical Current Generation

    NASA Astrophysics Data System (ADS)

    Ohl, Claus-Dieter; Gonzalez Avila, Silvestre Roberto; Song, Chaolong; Dung, Luong Trung

    2013-11-01

    Electro-osmotic flows are driven by an electric potential difference along a channel where the driving force is acting very close to the boundary at the electric double layer (EDL). The charge separation within the EDL gives rise to an electric current. Conversely, one may expect that a strong shear flow can induce an electric current that could be picked up with electrodes and a closed circuit. Previous experiments relied on a steady free jet at a nozzle exit driven by a strong pressure gradient. Here we utilize a laser induced cavitation bubble near an electrode equipped surface to generate strong shear from the impinging jet. Correlation of high-speed recordings of the spreading jet with current measurements reveals that the shear stress is causing the electric current. We make an attempt to calibrate this sensor in a better defined shear flow within a microfluidic channel.

  8. Periodic Exponential Shear of Complex Fluids

    E-print Network

    Chirag Kalelkar; Gareth McKinley

    2012-05-31

    We define a class of flows with exponential kinematics termed Periodic Exponential Shear (PES) flow which involve periodic exponential stretching of fluid elements along with their rotation. We exhibit analytical and numerical results for PES flow by using the Oldroyd-B model for viscoelastic fluids. We calculate the growth in the shear and the normal stresses analytically as well as demonstrate that repeated application of the flow leads to stable oscillatory shear and normal stresses. We define a material function applicable to a periodic, unsteady shear flow and show numerically that this material function exhibits deformation-rate thickening behavior for viscoelastic fluids subject to PES flow. We demonstrate the feasibility of PES flow by presenting preliminary experimental results from a controlled-strain rate rheometer, using a Newtonian mineral oil.

  9. Particle acceleration in astrophysical shear flows

    E-print Network

    Frank M. Rieger; Peter Duffy

    2005-01-10

    We consider the acceleration of particles due to a velocity shear in relativistic astrophysical flows. The basic physical picture and the formation of power law momentum spectra is discussed for a non-relativistic velocity field using a microscopic approach. We identify possible sites for shear acceleration in relativistic astrophysical jets and analyze their associated acceleration timescales. It is shown in particular that for a mean scattering time $\\tau$ scaling with the gyro-radius, the acceleration timescale for gradual shear scales in the same manner as the synchrotron cooling timescale, so that losses may no longer be able to stop the acceleration once it has started to work efficiently. Finally, the possible role of shear acceleration is discussed with reference to the relativistic jet in the quasar 3C~273.

  10. Shear thinning behavior of linear polymer melts under shear flow via nonequilibrium molecular dynamics

    NASA Astrophysics Data System (ADS)

    Xu, Xiaolei; Chen, Jizhong; An, Lijia

    2014-05-01

    The properties of both untangled and entangled linear polymer melts under shear flow are studied by nonequilibrium molecular dynamics simulations. The results reveal that the dependence of shear viscosity ? on shear rate dot{? }, expressed by ? ˜ dot{? }^{-n}, exhibits three distinct regimes. The first is the well-known Newtonian regime, namely, ? independent of shear rate at small shear rates dot{? }? 0^{-1}), the shear dependence of viscosity exhibits a crossover at a critical shear rate dot{? }c dividing this regime into two different regimes, shear thinning regime I (ST-I) and II (ST-II), respectively. In the ST-I regime (? ^{-1}_0dot{? }c) a universal power law ? ˜ dot{? }^{-0.37} is found for considered chain lengths. Furthermore, the longer the polymer chain is, the smaller the shear viscosity for a given shear rate in the ST-II regime. The simulation also shows that a characteristic chain length, below which dot{? }c will be equal to ? 0^{-1}, lies in the interval 30 < N < 50. For all considered chain lengths in the ST-II regime, we also find that the first and second normal stress differences N1 and N2 follow power laws of N1 ˜ dot{? }^{2/3} and N2 ˜ dot{? }^{0.82}, respectively; the orientation resistance parameter mG follows the relation mG ˜ dot{? }^{0.75} and the tumbling frequency ftb follows f_{tb} ˜ dot{? }^{0.75}. These results imply that the effects of entanglement on the shear dependences of these properties may be negligible in the ST-II regime. These findings may shed some light on the nature of shear thinning in flexible linear polymer melts.

  11. Wind effect on diurnal thermally driven flow in vegetated nearshore of a lake

    NASA Astrophysics Data System (ADS)

    Lin, Y. T.

    2014-12-01

    In this study, a highly idealized model is developed to discuss the interplay of diurnal heating/cooling induced buoyancy and wind stress on thermally driven flow over a vegetated slope. Since the model is linear, the horizontal velocity components can be broken into buoyancy-driven and surface wind-driven parts. Due to the presence of rooted emergent vegetation, the circulation strength even under the surface wind condition is still significantly reduced, and the transient (adjustment) stage for the initial conditions is shorter than that without vegetation. The flow in shallows is dominated by a viscosity/buoyancy balance as the case without wind, while the effect of wind stress is limited to the upper layer in deep water. In the lower layer of deep regions, vegetative drag is prevailing except the near bottom regions, where viscosity dominates. Under the unidirectional wind condition, a critical dimensionless shear stress to stop the induced flow can be found and is a function of horizontal location . For the periodic wind condition, if the two forcing mechanisms work in concert, the circulation magnitude can be increased. For the case where buoyancy and wind shear stress act against each other, the circulation strength is reduced and its structure becomes more complex. However, the flow magnitudes near the bottom for and are comparable because surface wind almost has no influence.

  12. Shear viscosity of degenerate electron matter

    E-print Network

    P. S. Shternin

    2008-03-27

    We calculate the partial electron shear viscosity $\\eta_{ee}$ limited by electron-electron collisions in a strongly degenerate electron gas taking into account the Landau damping of transverse plasmons. The Landau damping strongly suppresses $\\eta_{ee}$ in the domain of ultrarelativistic degenerate electrons and modifies its %asymptotic temperature behavior. The efficiency of the electron shear viscosity in the cores of white dwarfs and envelopes of neutron stars is analyzed.

  13. Shear-stabilized emulsion flooding process

    SciTech Connect

    Carpenter, C.W.; Reed, R.L.

    1982-06-29

    Additional amounts of crude oil are recovered from a subterranean formation by flooding with a translucent emulsion comprising an upper- or middle-phase microemulsion as an external phase and a polymer-containing brine solution as an internal phase. The translucent emulsion tends to coalesce into its component phases under conditions of no shear, but is stabilized by low shears such as those imposed on fluids flowing through a subterranean formation.

  14. Measurement of shear impedances of viscoelastic fluids

    SciTech Connect

    Sheen, Shuh-Haw; Chien, Hual-Te; Raptis, A.C.

    1996-12-31

    Shear-wave reflection coefficients from a solid/fluid interface are derived for non-Newtonian fluids that can be described by Maxwell, Voigt, and power-law fluid models. Based on model calculations, we have identified the measurable effects on the reflection coefficients due to fluid non-Newtonian behavior. The models are used to interpret the viscosity data obtained by a technique based on shear impedance measurement.

  15. 4-D ultrafast shear-wave imaging.

    PubMed

    Gennisson, Jean-Luc; Provost, Jean; Deffieux, Thomas; Papadacci, Clément; Imbault, Marion; Pernot, Mathieu; Tanter, Mickael

    2015-06-01

    Over the last ten years, shear wave elastography (SWE) has seen considerable development and is now routinely used in clinics to provide mechanical characterization of tissues to improve diagnosis. The most advanced technique relies on the use of an ultrafast scanner to generate and image shear waves in real time in a 2-D plane at several thousands of frames per second. We have recently introduced 3-D ultrafast ultrasound imaging to acquire with matrix probes the 3-D propagation of shear waves generated by a dedicated radiation pressure transducer in a single acquisition. In this study, we demonstrate 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration. A 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system was designed to perform 4-D shear-wave imaging. A matrix phased array was used to generate and control in 3-D the shear waves inside the medium using the acoustic radiation force. The same matrix array was used with 3-D coherent plane wave compounding to perform high-quality ultrafast imaging of the shear wave propagation. Volumetric ultrafast acquisitions were then beamformed in 3-D using a delay-and-sum algorithm. 3-D volumetric maps of the shear modulus were reconstructed using a time-of-flight algorithm based on local multiscale cross-correlation of shear wave profiles in the three main directions using directional filters. Results are first presented in an isotropic homogeneous and elastic breast phantom. Then, a full 3-D stiffness reconstruction of the breast was performed in vivo on healthy volunteers. This new full 3-D ultrafast ultrasound system paves the way toward real-time 3-D SWE. PMID:26067040

  16. Shear dispersion in dense granular flows

    DOE PAGESBeta

    Christov, Ivan C.; Stone, Howard A.

    2014-04-18

    We formulate and solve a model problem of dispersion of dense granular materials in rapid shear flow down an incline. The effective dispersivity of the depth-averaged concentration of the dispersing powder is shown to vary as the Péclet number squared, as in classical Taylor–Aris dispersion of molecular solutes. An extension to generic shear profiles is presented, and possible applications to industrial and geological granular flows are noted.

  17. Wind energy offers considerable promise

    E-print Network

    Langendoen, Koen

    Wind energy offers considerable promise: the wind itself is free, wind power is clean, we must develop new sources of energy. One of these sources, wind energy, offers considerable promise: the wind itself is free, wind power is clean, and it is inexhaustible. In recent years, research on wind

  18. Wind energy offers considerable promise

    E-print Network

    Langendoen, Koen

    Wind energy offers considerable promise: the wind itself is free, wind power is clean sources of energy. One of these sources, wind energy, offers considerable promise: the wind itself is free, wind power is clean, and it is inexhaustible. In recent years, research on wind energy has accelerated

  19. Could Crop Roughness Impact the Wind Resource at Agriculturally Productive Wind Farm Sites?

    NASA Astrophysics Data System (ADS)

    Vanderwende, B. J.; Lundquist, J. K.

    2014-12-01

    The high concentration of both large-scale agriculture and wind power production in the United States Midwest region raises new questions concerning the interaction of the two activities. For instance, it is known from internal boundary layer theory that changes in the roughness of the land-surface resulting from crop choices could modify the momentum field aloft. Upward propagation of such an effect might impact the properties of the winds encountered by modern turbines, which typically span a layer from about 40 to 120 meters above the surface. As direct observation of such interaction would require impractical interference in the planting schedules of farmers, we use numerical modeling to quantify the magnitude of crop-roughness effects. To simulate a collocated farm and turbine array, we use version 3.4.1 of the Weather Research and Forecasting model (WRF). The hypothetical farm is inserted near the real location of the 2013 Crop Wind Energy Experiment (CWEX). Reanalyses provide representative initial and boundary conditions. A month-long period spanning August 2013 is used to evaluate the differences in flows above corn (maize) and soybean crops at the mature, reproductive stage. Simulations are performed comparing the flow above each surface regime, both in the absence and presence of a wind farm, which consists of a parameterized 11x11 array of 1.8 MW Vestas V90 turbines. Appreciable differences in rotor-layer wind speeds emerge. The use of soybeans results in an increase in wind speeds and a corresponding reduction in rotor-layer shear when compared to corn. Despite the turbulent nature of flow within a wind farm, high stability reduces the impact of crop roughness on the flow aloft, particularly in the upper portion of the rotor disk. We use these results to estimate the economic impact of crop selection on wind power producers.

  20. The benefit of wind atlases in wind energy and their verification

    NASA Astrophysics Data System (ADS)

    Bethke, Julia; Kampmeyer, Jens; Mengelkamp, Heinz-Theo

    2014-05-01

    1 INTRODUCTION Wind atlases such as reanalysis data and downscaled data sets are widely used in the wind energy sector, e.g. for long-term correlation of short-term measurements or initial site search. Due to the financial impact of statements derived from wind atlases, their verification is of high importance. Here, different wind atlases are verified in-depth with numerous certified high-quality mast measurements covering a broad range of heights up to 200 m. In contrast to the commonly used weather stations, high masts allow for an evaluation of vertical profiles and atmospheric stability. The following questions will be addressed: What are wind atlases? How well are they performing? Which benefit do wind atlases have in wind energy? 2 APPROACH The performance of commonly used reanalysis data, e.g. MERRA, ERA-Interim, and two data sets downscaled from MERRA reanalysis data is investigated. The first downscaled data set is derived by the mesoscale model MM5 and has a spatial and temporal resolution of 20 km and 10 min, respectively. The second downscaled data set is derived by the WRF model and has a spatial and temporal resolution of 3 km and 10 min, respectively. Certified high-quality measurements of 45 met masts with 160 anemometers covering a range of complexity types, measurement heights between 30 m and 200 m and a time period of 2 years are compared to the wind atlases. Hourly values are analysed. 3 RESULTS The correlation with hourly measurements of wind speed is very good for all data sets. Correlation increases with decreasing terrain complexity. Wind directions are also met very well by all data sets. The frequency distributions of wind speed and therefore, the Weibull parameters are reproduced very well by the downscaled data sets for a broad range of velocities, however underestimating higher velocities. MERRA generally strongly overestimates wind speed. Diurnal and annual cycles as well as vertical profiles are reproduced more accurately by the downscaled data sets than by reanalysis data. Thereby, the WRF based atlas performs best, especially in complex terrain and forest areas. One outstanding result is that the downscaled wind atlases are able to simulate the change of the vertical wind shear during the course of the day and thus, atmospheric stability quite well. In general, the performance of all wind atlases weakens for areas with higher complexity and increased roughness (e.g. forests). For offshore sites an underestimation of the level of wind speed is observed. 4 CONCLUSION Correlations with wind speed and wind direction are high, indicating that all wind atlases are suitable for long-term correlation. However, the downscaled data sets yield an overall better performance when it comes to detailed analysis. This suggests that they are more appropriate for applications where the absolute value is important, e.g. the initial estimation of the wind potential, energy loss calculations or the calculation of revenues regarding changing electricity rates. Thus, value is added by downscaling from reanalysis data. Furthermore, we see an improvement from MM5 to WRF and higher spatial resolutions, especially in complex terrain and forest areas.

  1. Shear banding in soft glassy materials

    E-print Network

    Suzanne M. Fielding

    2014-08-20

    Many soft materials, including foams, dense emulsions, micro gel bead suspensions, star polymers, dense packing of surfactant onion micelles, and textured morphologies of liquid crystals, share the basic "glassy" features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike.

  2. Behavior of Tilted Angle Shear Connectors

    PubMed Central

    Khorramian, Koosha; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N. H.

    2015-01-01

    According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type. PMID:26642193

  3. Behavior of Tilted Angle Shear Connectors.

    PubMed

    Khorramian, Koosha; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N H

    2015-01-01

    According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type. PMID:26642193

  4. Wall shear stress in collapsed tubes

    NASA Astrophysics Data System (ADS)

    Naili, S.; Ribreau, C.

    1999-01-01

    A small flexural wall rigidity brings unique features to cross-sectional shapes and blood flow within veins, which are characterised by a non-uniform hemodynamical environment acting upon endothelial cells. Velocity fields and related wall shear stress were numerically determined for a large number of conditions, assuming a fully developed, steady, incompressible laminar flow through an uniform smooth pipe with a constant cross-section. It was shown that the flatness greatly influences the resulting distribution of the wall shear stresses along the lumen perimeter. For instance, under a steady longitudinal pressure gradient at about 500 Pascal per meter inside a constant oval-shaped tube, with a lumen perimeter of the order of 5 × 10^{-2} meter, the maximum wall shear stress is found at about 2 Pascal where the local curvature is minimal. On the other hand, the minimal wall shear stress of the order of 1 Pascal is found where the local curvature is maximal. Clear indications have been reported showing that the hemodynamical wall shear stress does alter endothelial cell morphology and orientation. These results are being used for developing an experimental set-up in order to locally map out the characteristic shear stresses looking for endothelial shape modifications whenever a viscous fluid flow is applied.

  5. Accurate shear measurement with faint sources

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Luo, Wentao; Foucaud, Sebastien

    2015-01-01

    For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys.

  6. Shear induced structures in crystallizing cocoa butter

    NASA Astrophysics Data System (ADS)

    Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.

    2004-03-01

    Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.

  7. Cosmology with cosmic shear observations: a review.

    PubMed

    Kilbinger, Martin

    2015-07-01

    Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as the implications for cosmology. We then conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations. PMID:26181770

  8. Cosmology with cosmic shear observations: a review

    NASA Astrophysics Data System (ADS)

    Kilbinger, Martin

    2015-07-01

    Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as the implications for cosmology. We then conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations.

  9. Analysis of shear banding in twelve materials

    NASA Astrophysics Data System (ADS)

    Batra, R. C.; Kim, C. H.

    The problem of the initiation and growth of shear bands in 12 different materials, namely, OFHC copper, Cartridge brass, Nickel 200, Armco IF (interstitial free) iron, Carpenter electric iron, 1006 steel, 2024-T351 aluminum, 7039 aluminum, low alloy steel, S-7 tool steel, Tungsten alloy, and Depleted Uranium (DU -0.75 Ti) is studied with the objectives of finding out when a shear band initiates, and upon what parameters does the band width depend. The nonlinear coupled partial differential equations governing the overall simple shearing deformations of a thermally softening viscoplastic block are analyzed. It is assumed that the thermomechanical response of these materials can be adequately represented by the Johnson-Cook law, and the only inhomogeneity present in the block is the variation in its thickness. The effect of the defect size on the initiation and subsequent growth of the band is also studied. It is found that, for each one of these 12 materials, the deformation has become nonhomogeneous by the time the maximum shear stress occurs. Also the band width, computed when the shear stress has dropped to 85 percent of its peak value, does not correlate well with the thermal conductivity of the material. The band begins to grow rapidly when the shear stress has dropped to 90 percent of its maximum value.

  10. Vandenberg Air Force Base Upper Level Wind Launch Weather Constraints

    NASA Technical Reports Server (NTRS)

    Shafer, Jaclyn A.; Wheeler, Mark M.

    2012-01-01

    The 30th Operational Support Squadron Weather Flight (30 OSSWF) provides comprehensive weather services to the space program at Vandenberg Air Force Base (VAFB) in California. One of their responsibilities is to monitor upper-level winds to ensure safe launch operations of the Minuteman III ballistic missile. The 30 OSSWF tasked the Applied Meteorology Unit (AMU) to analyze VAFB sounding data with the goal of determining the probability of violating (PoV) their upper-level thresholds for wind speed and shear constraints specific to this launch vehicle, and to develop a tool that will calculate the PoV of each constraint on the day of launch. In order to calculate the probability of exceeding each constraint, the AMU collected and analyzed historical data from VAFB. The historical sounding data were retrieved from the National Oceanic and Atmospheric Administration Earth System Research Laboratory archive for the years 1994-2011 and then stratified into four sub-seasons: January-March, April-June, July-September, and October-December. The maximum wind speed and 1000-ft shear values for each sounding in each subseason were determined. To accurately calculate the PoV, the AMU determined the theoretical distributions that best fit the maximum wind speed and maximum shear datasets. Ultimately it was discovered that the maximum wind speeds follow a Gaussian distribution while the maximum shear values follow a lognormal distribution. These results were applied when calculating the averages and standard deviations needed for the historical and real-time PoV calculations. In addition to the requirements outlined in the original task plan, the AMU also included forecast sounding data from the Rapid Refresh model. This information provides further insight for the launch weather officers (LWOs) when determining if a wind constraint violation will occur over the next few hours on day of launch. The interactive graphical user interface (GUI) for this project was developed in Microsoft Excel using Visual Basic for Applications. The GUI displays the critical sounding data easily and quickly for the LWOs on day of launch. This tool will replace the existing one used by the 30 OSSWF, assist the LWOs in determining the probability of exceeding specific wind threshold values, and help to improve the overall upper winds forecast for the launch customer.

  11. Magnetized stratified rotating shear waves

    NASA Astrophysics Data System (ADS)

    Salhi, A.; Lehner, T.; Godeferd, F.; Cambon, C.

    2012-02-01

    We present a spectral linear analysis in terms of advected Fourier modes to describe the behavior of a fluid submitted to four constraints: shear (with rate S), rotation (with angular velocity ?), stratification, and magnetic field within the linear spectral theory or the shearing box model in astrophysics. As a consequence of the fact that the base flow must be a solution of the Euler-Boussinesq equations, only radial and/or vertical density gradients can be taken into account. Ertel's theorem no longer is valid to show the conservation of potential vorticity, in the presence of the Lorentz force, but a similar theorem can be applied to a potential magnetic induction: The scalar product of the density gradient by the magnetic field is a Lagrangian invariant for an inviscid and nondiffusive fluid. The linear system with a minimal number of solenoidal components, two for both velocity and magnetic disturbance fields, is eventually expressed as a four-component inhomogeneous linear differential system in which the buoyancy scalar is a combination of solenoidal components (variables) and the (constant) potential magnetic induction. We study the stability of such a system for both an infinite streamwise wavelength (k1=0, axisymmetric disturbances) and a finite one (k1?0, nonaxisymmetric disturbances). In the former case (k1=0), we recover and extend previous results characterizing the magnetorotational instability (MRI) for combined effects of radial and vertical magnetic fields and combined effects of radial and vertical density gradients. We derive an expression for the MRI growth rate in terms of the stratification strength, which indicates that purely radial stratification can inhibit the MRI instability, while purely vertical stratification cannot completely suppress the MRI instability. In the case of nonaxisymmetric disturbances (k1?0), we only consider the effect of vertical stratification, and we use Levinson's theorem to demonstrate the stability of the solution at infinite vertical wavelength (k3=0): There is an oscillatory behavior for ?>1+|K2/k1|, where ?=St is a dimensionless time and K2 is the radial component of the wave vector at ?=0. The model is suitable to describe instabilities leading to turbulence by the bypass mechanism that can be relevant for the analysis of magnetized stratified Keplerian disks with a purely azimuthal field. For initial isotropic conditions, the time evolution of the spectral density of total energy (kinetic + magnetic + potential) is considered. At k3=0, the vertical motion is purely oscillatory, and the sum of the vertical (kinetic + magnetic) energy plus the potential energy does not evolve with time and remains equal to its initial value. The horizontal motion can induce a rapid transient growth provided K2/k1?1. This rapid growth is due to the aperiodic velocity vortex mode that behaves like Kh/kh where kh(?)=[k12+(K2-k1?)2]1/2 and Kh=kh(0). After the leading phase (?>K2/k1?1), the horizontal magnetic energy and the horizontal kinetic energy exhibit a similar (oscillatory) behavior yielding a high level of total energy. The contribution to energies coming from the modes k1=0 and k3=0 is addressed by investigating the one-dimensional spectra for an initial Gaussian dense spectrum. For a magnetized Keplerian disk with a purely vertical field, it is found that an important contribution to magnetic and kinetic energies comes from the region near k1=0. The limit at k1=0 of the streamwise one-dimensional spectra of energies, or equivalently, the streamwise two-dimensional (2D) energy, is then computed. The comparison of the ratios of these 2D quantities with their three-dimensional counterparts provided by previous direct numerical simulations shows a quantitative agreement.

  12. Microstructural and Rheological Evolution of a Mantle Shear Zone

    E-print Network

    Skemer, Philip

    Microstructural and Rheological Evolution of a Mantle Shear Zone PHILIP SKEMER1 *, JESSICA M of a high-strain mantle shear zone from the Josephine Peridotite, SW Oregon, USA. The goal of this study. The shear zone we investigated exhibits higher strain and greater localization than previously studied shear

  13. Relation between ordering and shear thinning in colloidal suspensions

    E-print Network

    Dinner, Aaron

    ) Colloidal suspensions exhibit shear thinning and shear thickening. The most common interpretation of these phenomena identifies layering of the fluid perpendicular to the shear gradient as the driverRelation between ordering and shear thinning in colloidal suspensions Xinliang Xu1 , Stuart A. Rice

  14. Q. J. R. Meteorol. Soc. (2004), 130, pp. 120 Using mesocale model winds for correcting wind-drift errors in radar

    E-print Network

    Reading, University of

    2004-01-01

    vertical profile of reflectivity shear fall streak wind drift 1. Introduction Operational radars around-drift errors in radar estimates of surface rainfall By MARION P. MITTERMAIER , ROBIN J. HOGAN and ANTHONY J For operational radars at middle and high latitudes even the lowest beam of a scan sequence may be above

  15. Experimental assessment of air permeability in a concrete shear wall subjected to simulated seismic loading

    SciTech Connect

    Girrens, S.P.; Farrar, C.R.

    1991-07-01

    A safety concern for the proposed Special Nuclear Materials Laboratory (SNML) facility at the Los Alamos National Laboratory was air leakage from the facility if it were to experience a design basis earthquake event. To address this concern, a study was initiated to estimate air leakage, driven by wind-generated pressure gradients, from a seismically damaged concrete structure. This report describes a prototype experiment developed and performed to measure the air permeability in a reinforced concrete shear wall, both before and after simulated seismic loading. A shear wall test structure was fabricated with standard 4000-psi concrete mix. Static load-cycle testing was used to simulate earthquake loading. Permeability measurements were made by pressurizing one side of the shear wall above atmospheric conditions and recording the transient pressure decay. As long as the structure exhibited linear load displacement response, no variation in the air permeability was detected. However, experimental results indicate that the air permeability in the shear wall increased by a factor of 40 after the wall had been damaged (cracked). 17 figs., 8 tabs.

  16. Self-organization of ULF electromagnetic wave structures in the shear flow driven dissipative ionosphere

    NASA Astrophysics Data System (ADS)

    Aburjania, G.; Chargazia, K.; Kharshiladze, O.; Zimbardo, G.

    2014-08-01

    This work is devoted to investigation of nonlinear dynamics of planetary electromagnetic (EM) ultra-low-frequency wave (ULFW) structures in the rotating dissipative ionosphere in the presence of inhomogeneous zonal wind (shear flow). Planetary EM ULFW appears as a result of interaction of the ionospheric medium with the spatially inhomogeneous geomagnetic field. The shear flow driven wave perturbations effectively extract energy of the shear flow increasing own amplitude and energy. These perturbations undergo self organization in the form of the nonlinear solitary vortex structures due to nonlinear twisting of the perturbation's front. Depending on the features of the velocity profiles of the shear flows the nonlinear vortex structures can be either monopole vortices, or dipole vortex, or vortex streets and vortex chains. From analytical calculation and plots we note that the formation of stationary nonlinear vortex structure requires some threshold value of translation velocity for both non-dissipation and dissipation complex ionospheric plasma. The space and time attenuation specification of the vortices is studied. The characteristic time of vortex longevity in dissipative ionosphere is estimated. The long-lived vortices transfer the trapped medium particles, energy and heat. Thus they represent structural elements of turbulence in the ionosphere.

  17. Q-Winds satellite hurricane wind retrievals and H*Wind comparisons

    E-print Network

    Hennon, Christopher C.

    1 Q-Winds satellite hurricane wind retrievals and H*Wind comparisons Pet Laupattarakasem and W This paper presents a new hurricane ocean vector wind (OVW) product known as Q-Winds produced from the SeaWinds for tropical cyclones. SeaWinds OVW retrievals are presented for ten hurricane passes with near

  18. The Effect of Wind-Turbine Wakes on Summertime US Midwest Atmospheric Wind Profiles as Observed with Ground-Based Doppler Lidar

    NASA Astrophysics Data System (ADS)

    Rhodes, Michael E.; Lundquist, Julie K.

    2013-07-01

    We examine the influence of a modern multi-megawatt wind turbine on wind and turbulence profiles three rotor diameters (D) downwind of the turbine. Light detection and ranging (lidar) wind-profile observations were collected during summer 2011 in an operating wind farm in central Iowa at 20-m vertical intervals from 40 to 220 m above the surface. After a calibration period during which two lidars were operated next to each other, one lidar was located approximately 2D directly south of a wind turbine; the other lidar was moved approximately 3D north of the same wind turbine. Data from the two lidars during southerly flow conditions enabled the simultaneous capture of inflow and wake conditions. The inflow wind and turbulence profiles exhibit strong variability with atmospheric stability: daytime profiles are well-mixed with little shear and strong turbulence, while nighttime profiles exhibit minimal turbulence and considerable shear across the rotor disk region and above. Consistent with the observations available from other studies and with wind-tunnel and large-eddy simulation studies, measurable reductions in wake wind-speeds occur at heights spanning the wind turbine rotor (43-117 m), and turbulent quantities increase in the wake. In generalizing these results as a function of inflow wind speed, we find the wind-speed deficit in the wake is largest at hub height or just above, and the maximum deficit occurs when wind speeds are below the rated speed for the turbine. Similarly, the maximum enhancement of turbulence kinetic energy and turbulence intensity occurs at hub height, although observations at the top of the rotor disk do not allow assessment of turbulence in that region. The wind shear below turbine hub height (quantified here with the power-law coefficient) is found to be a useful parameter to identify whether a downwind lidar observes turbine wake or free-flow conditions. These field observations provide data for validating turbine-wake models and wind-tunnel observations, and for guiding assessments of the impacts of wakes on surface turbulent fluxes or surface temperatures downwind of turbines.

  19. Analysis of vector wind change with respect to time for Cape Kennedy, Florida

    NASA Technical Reports Server (NTRS)

    Adelfang, S. I.

    1978-01-01

    Multivariate analysis was used to determine the joint distribution of the four variables represented by the components of the wind vector at an initial time and after a specified elapsed time is hypothesized to be quadravariate normal; the fourteen statistics of this distribution, calculated from 15 years of twice-daily rawinsonde data are presented by monthly reference periods for each month from 0 to 27 km. The hypotheses that the wind component changes with respect to time is univariate normal, that the joint distribution of wind component change with respect to time is univariate normal, that the joint distribution of wind component changes is bivariate normal, and that the modulus of vector wind change is Rayleigh are tested by comparison with observed distributions. Statistics of the conditional bivariate normal distributions of vector wind at a future time given the vector wind at an initial time are derived. Wind changes over time periods from 1 to 5 hours, calculated from Jimsphere data, are presented. Extension of the theoretical prediction (based on rawinsonde data) of wind component change standard deviation to time periods of 1 to 5 hours falls (with a few exceptions) within the 95 percentile confidence band of the population estimate obtained from the Jimsphere sample data. The joint distributions of wind change components, conditional wind components, and 1 km vector wind shear change components are illustrated by probability ellipses at the 95 percentile level.

  20. Shear banding in large amplitude oscillatory shear (LAOStrain and LAOStress) of polymers and wormlike micelles

    E-print Network

    Katherine A. Carter; John M. Girkin; Suzanne M. Fielding

    2015-10-01

    We investigate theoretically shear banding in large amplitude oscillatory shear (LAOS) of polymers and wormlike micelles. In LAOStrain we find banding at low frequencies and sufficiently high strain rate amplitudes in fluids for which the underlying constitutive curve of shear stress as a function of shear rate is non-monotonic. This is the direct analogue of quasi steady state banding seen in slow strain rate sweeps along the flow curve. At higher frequencies and sufficiently high strain amplitudes we report a different but related phenomenon, which we call `elastic' shear banding. This is associated with an overshoot in the elastic (Lissajous-Bowditch) curve of stress as a function of strain. We suggest that this may arise widely even in fluids that have a monotonic underlying constitutive curve, and so do not show steady state banding under a steadily applied shear flow. In LAOStress we report banding in fluids that shear thin strongly enough to have either a negatively, or weakly positively, sloping region in the underlying constitutive curve, noting again that fluids in the latter category do not display steady state banding in a steadily applied flow. This banding is triggered in each half cycle as the stress magnitude transits the region of weak slope in an upward direction, such that the fluid effectively yields. Our numerics are performed in the Rolie-poly model of polymeric fluids, but we also provide arguments suggesting that our results should apply more widely. Besides banding in the shear rate profile, which can be measured by velocimetry, we also predict banding in the shear and normal stress components, measurable by birefringence. As a backdrop to understanding the new results on shear banding in LAOS, we also briefly review earlier work on banding in other time-dependent protocols, focusing in particular on shear startup and step stress.

  1. Auto-acoustic compaction in steady shear flows: Experimental evidence for suppression of shear dilatancy by internal

    E-print Network

    granular medium, and formulate an empirical model for the steady state thickness of a shear-zone in which is the strain rate, and p is the confining (normal) pressure. The shear rate profile in boundary driven flowsAuto-acoustic compaction in steady shear flows: Experimental evidence for suppression of shear

  2. Shear Flows and Shear Viscosity in a Two-Dimensional Yukawa System (Dusty Plasma) V. Nosenko* and J. Goree

    E-print Network

    Goree, John

    Shear Flows and Shear Viscosity in a Two-Dimensional Yukawa System (Dusty Plasma) V. Nosenko* and J 21 May 2004; published 7 October 2004) The shear viscosity of a two-dimensional liquid-state dusty. By fitting the particle velocity profiles in the shear flow to a Navier-Stokes model, the kinematic viscosity

  3. Wind Power Career Chat

    SciTech Connect

    L. Flowers

    2011-01-01

    This document will teach students about careers in the wind energy industry. Wind energy, both land-based and offshore, is expected to provide thousands of new jobs in the next several decades. Wind energy companies are growing rapidly to meet America's demand for clean, renewable, and domestic energy. These companies need skilled professionals. Wind power careers will require educated people from a variety of areas. Trained and qualified workers manufacture, construct, operate, and manage wind energy facilities. The nation will also need skilled researchers, scientists, and engineers to plan and develop the next generation of wind energy technologies.

  4. Wind energy information guide

    SciTech Connect

    1996-04-01

    This book is divided into nine chapters. Chapters 1--8 provide background and annotated references on wind energy research, development, and commercialization. Chapter 9 lists additional sources of printed information and relevant organizations. Four indices provide alphabetical access to authors, organizations, computer models and design tools, and subjects. A list of abbreviations and acronyms is also included. Chapter topics include: introduction; economics of using wind energy; wind energy resources; wind turbine design, development, and testing; applications; environmental issues of wind power; institutional issues; and wind energy systems development.

  5. Wind power today

    SciTech Connect

    1998-04-01

    This publication highlights initiatives of the US DOE`s Wind Energy Program. 1997 yearly activities are also very briefly summarized. The first article describes a 6-megawatt wind power plant installed in Vermont. Another article summarizes technical advances in wind turbine technology, and describes next-generation utility and small wind turbines in the planning stages. A village power project in Alaska using three 50-kilowatt turbines is described. Very brief summaries of the Federal Wind Energy Program and the National Wind Technology Center are also included in the publication.

  6. Molecular Dynamics Simulation of Shear Moduli for Coulomb Crystals

    E-print Network

    C. J. Horowitz; J. Hughto

    2008-12-15

    Torsional (shear) oscillations of neutron stars may have been observed in quasiperiodic oscillations of Magnetar Giant Flares. The frequencies of these modes depend on the shear modulus of neutron star crust. We calculate the shear modulus of Coulomb crystals from molecular dynamics simulations. We find that electron screening reduces the shear modulus by about 10% compared to previous Ogata et al. results. Our MD simulations can be extended to calculate the effects of impurities and or polycrystalline structures on the shear modulus.

  7. Rapid injection of near-inertial shear into the stratified upper ocean at an Antarctic Circumpolar Current front

    NASA Astrophysics Data System (ADS)

    Forryan, Alexander; Naveira Garabato, Alberto C.; Polzin, Kurt L.; Waterman, Stephanie

    2015-05-01

    The impact on the upper ocean of the passage of a short, intense storm over a Southern Ocean site, in proximity to an Antarctic Circumpolar Current front, is characterized. The storm causes a wind-induced deepening of the mixed layer and generates an inertial current. Immediate poststorm observations indicate a mixed layer extending to approximately 50 m depth. Subsequent measurements show the upper ocean to have restratified, injecting near-inertial shear in stratified waters within 1 day of the storm's passage. This time scale for the development of near-inertial shear is 1 order of magnitude shorter than that predicted by the ? dispersion paradigm. The observed rapid changes in upper ocean stratification point to the existence of an as yet undocumented, efficient mechanism for injection of near-inertial shear into the stratified ocean that is in turn associated with enhanced turbulence and mixing.

  8. Dependence of Wind Turbine Curves on Atmospheric Stability Regimes - An Analysis of a West Coast North American Tall Wind Farm

    SciTech Connect

    Wharton, S; Lundquist, J K; Sharp, J; Zulauf, M

    2009-08-24

    Tall wind turbines, with hub heights at 80 m or above, can extract large amounts of energy from the atmosphere because they are likely to encounter higher wind speeds, but they face challenges given the complex nature of wind flow in the boundary layer. Depending on whether the boundary layer is stable, convective or neutral, mean wind speed (U) and turbulence ({sigma}{sub U}) may vary greatly across the tall turbine swept area (40 m to 120 m). This variation can cause a single turbine to produce difference amounts of power during time periods of identical hub height wind speeds. The study examines the influence that atmospheric mixing or stability has on power output at a West Coast North American wind farm. They first examine the accuracy and applicability of two, relatively simple stability parameters, the wind shear-exponent, {alpha}, and the turbulence intensity, I{sub u}, against the physically-based, Obukhov length, L, to describe the wind speed and turbulence profiles in the rotor area. In general, the on-site stability parameters {alpha} and I{sub u} are in high agreement with the off-site, L stability scale parameter. Next, they divide the measurement period into five stability classes (strongly stable, stable, neutral, convective, and strongly convective) to discern stability-effects on power output. When only the mean wind speed profile is taken into account, the dependency of power output on boundary layer stability is only subtly apparent. When turbulence intensity I{sub u} is considered, the power generated for a given wind speed is twenty percent higher during strongly stable conditions than during strongly convective conditions as observed in the spring and summer seasons at this North American wind farm.

  9. Shear Layer Refraction Corrections for Off-Axis Sources in a Jet Flow

    NASA Astrophysics Data System (ADS)

    MORFEY, C. L.; JOSEPH, P. F.

    2001-01-01

    A set of equations is derived for converting acoustic measurements taken in a free-jet flight simulation facility, such as the U.K. Noise Test Facility at Pyestock or the French CEPRA-19 wind tunnel at Saclay, to equivalent farfield flight conditions. The equations are based on the high-frequency geometrical acoustics approximation, whose application in the present context was justified in early studies by Morfey and Tester in 1977 and by Amiet in 1978. However, the present work differs by allowing the source to be positioned off the jet centreline, anywhere within the flight stream. The flight stream jet is modelled as an axisymmetric parallel shear flow, with a shear layer thickness which is small compared with the jet diameter. The model also permits the microphone to be located anywhere outside the flow, arbitrarily close to the open jet. The consequences of off-axis source location are illustrated by numerical calculations.

  10. 2008 Wind Energy Projects, Wind Powering America (Poster)

    SciTech Connect

    Not Available

    2009-01-01

    The Wind Powering America program produces a poster at the end of every calendar year that depicts new U.S. wind energy projects. The 2008 poster includes the following projects: Stetson Wind Farm in Maine; Dutch Hill Wind Farm in New York; Grand Ridge Wind Energy Center in Illinois; Hooper Bay, Alaska; Forestburg, South Dakota; Elbow Creek Wind Project in Texas; Glacier Wind Farm in Montana; Wray, Colorado; Smoky Hills Wind Farm in Kansas; Forbes Park Wind Project in Massachusetts; Spanish Fork, Utah; Goodland Wind Farm in Indiana; and the Tatanka Wind Energy Project on the border of North Dakota and South Dakota.

  11. Influence of shear heating on microstructurally defined plate boundary shear zones

    NASA Astrophysics Data System (ADS)

    Platt, John P.

    2015-10-01

    In plate-boundary scale ductile shear zones defined by microstructural weakening, shear heating may lead to a temperature increase over 5 m.y. of up to 80 °C just below the brittle ductile transition, up to 120 °C just below the Moho, and to thermal boundary zones tens of km wide on either side of the shear zone. Where rock strength is highest, shear zones are narrow (?1 km), and thermal gradients within the shear zone itself are low, so there is no tendency for increased localization. Heating results in thermal weakening, but this is partly offset by grain growth related to the decrease in stress. In shear zones of the order of 10 km width, shear stress, strain rate, and hence heat generation are lower, and thermal gradients are insufficient to cause additional strain localization. Temperature increases in the mid-crust are of the order of 10 °C, insufficient to cause partial melting or an increase in metamorphic grade. In the upper mantle, shear zones may be 50 km or more wide, and the temperature increase is less than 20 °C in 5 m.y., but temperature differences between center and margin may enhance the strain rate at the center by up to 18%.

  12. Shear with comminution of a granular material: Microscopic deformations outside the shear band

    E-print Network

    Schmittbuhl, Jean

    ´dex, France Received 27 March 2003; published 23 July 2003 A correlation imaging velocimetry technique this shear band and observed a rich dynamics of large and intermittent mechanical clusters up to 50 particles is observed, indicative of a slow decoupling between the shear band and the rest of the sample. This slow

  13. Divergent Shear Thinning and Shear Thickening Behavior of Supramolecular Polymer Networks in Semidilute Entangled Polymer Solutions

    PubMed Central

    Xu, Donghua; Liu, Chen-Yang; Craig, Stephen L.

    2011-01-01

    The steady shear behavior of metallo-supramolecular polymer networks formed by bis-Pd(II) cross-linkers and semidilute entangled solutions of poly(4-vinylpyridine) (PVP) in dimethyl sulfoxide (DMSO) or N,N-dimethyl formamide (DMF) is reported. The steady shear behavior of the networks depends on the dissociation rate and association rate of the cross-linkers, the concentration of cross-linkers, and the concentration of the polymer solution. The divergent steady shear behavior—shear thinning versus shear thickening—of samples with identical structure but different cross-linker dynamics (J. Phys. Chem. Lett. 2010, 1, 1683-1686) is further explored in this paper. The divergent steady shear behavior for networks with different cross-linkers is connected to a competition between different time scales: the average time that a cross-linker remains open (?1) and the local relaxation time of a segment of polymer chain (?segment). When ?1 is larger than ?segment, shear thickening is observed. When ?1 is smaller than ?segment, only shear thinning is observed. PMID:21547008

  14. Wave-current interaction in coastal waters: Effects on the bottom-shear stress

    NASA Astrophysics Data System (ADS)

    Rosales, P.; Ocampo-Torres, F. J.; Osuna, P.; Monbaliu, J.; Padilla-Hernández, R.

    Computer simulations of wave and current fields in the southern North Sea were made with a coupled-models system to study the influence of wave-current interactions on the bottom-shear stress in coastal waters. A third-generation wave-spectral model is coupled with a tide-surge model, which provides current and water level information to take into account wave-current interactions, to calculate the bottom stress. Two different expressions for bottom friction are used; one derived from the JONSWAP experiment, and a second given by Christoffersen and Jonsson that takes into account wave-current interaction at the bottom. The coupled-models system is applied to four nested grids to achieve fine spatial resolution near the Belgium coast. Two events of moderate to high waves are analyzed. Those two events are associated with different wind regimes; SW winds for the first period and NW for the second. The calculations of bottom-shear stress when taking into account wave-current interactions are compared with reference runs where only waves are considered to calculate the energy dissipation at the bottom. Small differences in the bottom-shear stress results are observed mainly related to the water-level variation caused by tides, when coupled and uncoupled runs using the JONSWAP expression were compared. However, when wave-current interactions are taken into account using the expression of Christoffersen and Jonsson, the calculated maximum bottom stress is usually doubled for coupled-model runs compared to the reference runs. The results clearly show that the formulation of the bottom-friction dissipation that accounts for the effect of wave-current interaction has quite a significant effect on the determination of the bottom-shear stress.

  15. User's guide for a personal computer model of turbulence at a wind turbine rotor

    SciTech Connect

    Connell, J.R.; Powell, D.C.; Gower, G.L.

    1989-08-01

    This document is primarily (1) a user's guide for the personal computer (PC) version of the code for the PNL computational model of the rotationally sampled wind speed (RODASIM11) and (2) a brief guide to the growing literature on the subject of rotationally sampled turbulence, from which the model is derived. The model generates values of turbulence experienced by single points fixed in the rotating frame of reference of an arbitrary wind turbine blade. The character of the turbulence depends on the specification of mean wind speed, the variance of turbulence, the crosswind and along-wind integral scales of turbulence, mean wind shear, and the hub height, radius, and angular speed of rotation of any point at which wind fluctuation is to be calculated. 13 refs., 4 figs., 4 tabs.

  16. Residential Wind Power

    E-print Network

    Willis, Gary

    2011-12-16

    This research study will explore the use of residential wind power and associated engineering and environmental issues. There is various wind power generating devices available to the consumer. The study will discuss the dependencies of human...

  17. Solar Wind Five

    NASA Technical Reports Server (NTRS)

    Neugebauer, M. (editor)

    1983-01-01

    Topics of discussion were: solar corona, MHD waves and turbulence, acceleration of the solar wind, stellar coronae and winds, long term variations, energetic particles, plasma distribution functions and waves, spatial dependences, and minor ions.

  18. After the Wind Storm 

    E-print Network

    Unknown

    2011-09-05

    Accidents and hazards continue to plague the construction industry. One often overlooked hazard to workers is the potential for flying debris and materials during high winds. This research was designed to evaluate the wind velocity required...

  19. WindWaveFloat

    SciTech Connect

    Weinstein, Alla

    2011-11-01

    Presentation from the 2011 Water Peer Review includes in which principal investigator Alla Weinstein discusses project progress in development of a floating offshore wind structure - the WindFloat - and incorporation therin of a Spherical Wave Energy Device.

  20. Bats and Wind Energy

    USGS Multimedia Gallery

    USGS biologist Paul Cryan examines the carcass of a hoary bat (Lasiurus cinereus) found beneath a wind turbine. By examining the casualties, biologists hope to learn more about why migratory bats are so susceptible to wind turbines. ...

  1. Wind Energy Facility

    USGS Multimedia Gallery

    Wind energy facility in the Northeastern United States. An unexpected number of dead bats began appearing beneath industrial-scale wind turbines in North America and Europe during the past 10 years....

  2. Direct shear loading leads to failure of generator bolts, rotor

    SciTech Connect

    Flanagan, P.J.; Knittel, D. )

    1993-02-01

    Direct shear loading can result in the failure of bolts clamping the rotor flange to the shaft flange of a hydroelectric generator. Such was the case at the California Department of Water Resources 440-MW Gianelli Pumping-Generating Plant. The incident occurred July 5, 1991, when operators were bringing Unit 1 into service for generation. Tremendous forces on one of the unit's two rotors sheared ten 3 1/2-inch-diameter spider flange assembly bolts (ASTM A193-B16 steel) on the rotor, deforming bolt holes in both the spider flange and the shaft flange. The flanges, which allow the generator to transmit power through friction, rubbed and galled before the unit came to rest. The sudden shock load also slightly twisted the spider of the rotor, which during normal operation turns at 120 revolutions per minute at head of 190 to 245 feet. During normal operation, operators open a butterfly valve, allowing water to rush from a penstock to turn an impeller, which is connected to the generator rotor. Each of the plant's eight units is equipped with two rotors mounted on the same shaft. As the butterfly valve is gradually opened, speed of the unit increases. When the generator rotor is spinning at 90 percent of synchronous speed, the main unit breaker closes, energizing the stator windings with 13,800 volts. This rapidly accelerates the generator to approximately 98 percent of synchronous speed. The field breaker then closes, energizing the rotor poles with DC current. The rotor current reaches full strength in 2 to 5 seconds. During this time, the poles on the rotor are attempting to fall into step with the stator's rotating magnetic field.

  3. Solid state coherent laser radar wind-field measurement systems

    NASA Astrophysics Data System (ADS)

    Huffaker, Robert M.; Reveley, Paul A.

    1997-05-01

    Diode-pumped solid-state pulsed coherent laser radar systems have recently been developed at Coherent Technologies, Inc., for the remote measurement of atmospheric wind fields. Flash- lamp pumped systems have been utilized since 1990 for obtaining wind field measurements. These flash-lamp pumped lidar systems have been applied to wind profiling, aircraft wake vortex measurements, airport wind shear and gust front monitoring, and military cargo air drops and many other applications. The diode-pumped coherent lidar systems currently available are capable of near turnkey operation. The Tm:YAG laser transceivers operate at 2.02 microns with output pulse energies of 1 t 10 mJ with PRFs of 1,000 to 100 Hz respectively. Range resolution of 30 - 75 m are typical. A real-time lidar signal processor has also been developed for collecting and analyzing laser radar (lidar) data. The signal processor is based on a commercial PC architecture and offers a real-time data acquisition, analysis, display, recording and playback environment. Wind measurements and overall system performance results are presented. Wind measurement performance, for a variety of applications, are presented using the flashlamp and diode pumped coherent lidars including measured wind profiles from ground and on aircraft, wake vortex tracking results, and example flows over mountain terrain.

  4. Piezoelectric energy harvesting through shear mode operation

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Sodano, Henry A.

    2015-05-01

    Piezoelectric materials are excellent candidates for use in energy harvesting applications due to their high electromechanical coupling properties that enable them to convert input mechanical energy into useful electric power. The electromechanical coupling coefficient of the piezoelectric material is one of the most significant parameters affecting energy conversion and is dependent on the piezoelectric mode of operation. In most piezoceramics, the d15 piezoelectric shear coefficient is the highest coefficient compared to the commonly used axial and transverse modes that utilize the d33 and the d31 piezoelectric strain coefficients. However, complicated electroding methods and challenges in evaluating the performance of energy harvesting devices operating in the shear mode have slowed research in this area. The shear deformation of a piezoelectric layer can be induced in a vibrating sandwich beam with a piezoelectric core. Here, a model based on Timoshenko beam theory is developed to predict the electric power output from a cantilever piezoelectric sandwich beam under base excitations. It is shown that the energy harvester operating in the shear mode is able to generate ?50% more power compared to the transverse mode for a numerical case study. Reduced models of both shear and transverse energy harvesters are obtained to determine the optimal load resistance in the system and perform an efficiency comparison between two models with fixed and adaptive resistances.

  5. Review article: Cosmology with cosmic shear observations

    E-print Network

    Kilbinger, Martin

    2014-01-01

    Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as ...

  6. Granular Shear Flow in Varying Gravitational Environments

    NASA Astrophysics Data System (ADS)

    Murdoch, N.; Rozitis, B.; Green, S. F.; de Lophem, T.-L.; Michel, P.; Losert, W.

    2016-01-01

    Despite their very low surface gravities, asteroids exhibit a number of different geological processes involving granular matter. Understanding the response of this granular material subject to external forces in microgravity conditions is vital to the design of a successful asteroid sub-surface sampling mechanism, and in the interpretation of the fascinating geology on an asteroid. We have designed and flown a Taylor-Couette shear cell to investigate granular flow due to rotational shear forces under the conditions of parabolic flight microgravity. The experiments occur under weak compression. First, we present the technical details of the experimental design with particular emphasis on how the equipment has been specifically designed for the parabolic flight environment. Then, we investigate how a steady state granular flow induced by rotational shear forces differs in varying gravitational environments. We find that the effect of constant shearing on the granular material, in a direction perpendicular to the effective acceleration, does not seem to be strongly influenced by gravity. This means that shear bands can form in the presence of a weak gravitational field just as on Earth.

  7. Pressure-shear experiments on granular materials.

    SciTech Connect

    Reinhart, William Dodd; Thornhill, Tom Finley, III; Vogler, Tracy John; Alexander, C. Scott

    2011-10-01

    Pressure-shear experiments were performed on granular tungsten carbide and sand using a newly-refurbished slotted barrel gun. The sample is a thin layer of the granular material sandwiched between driver and anvil plates that remain elastic. Because of the obliquity, impact generates both a longitudinal wave, which compresses the sample, and a shear wave that probes the strength of the sample. Laser velocity interferometry is employed to measure the velocity history of the free surface of the anvil. Since the driver and anvil remain elastic, analysis of the results is, in principal, straightforward. Experiments were performed at pressures up to nearly 2 GPa using titanium plates and at higher pressure using zirconium plates. Those done with the titanium plates produced values of shear stress of 0.1-0.2 GPa, with the value increasing with pressure. On the other hand, those experiments conducted with zirconia anvils display results that may be related to slipping at an interface and shear stresses mostly at 0.1 GPa or less. Recovered samples display much greater particle fracture than is observed in planar loading, suggesting that shearing is a very effective mechanism for comminution of the grains.

  8. Nonmonotonic flow curves of shear thickening suspensions

    NASA Astrophysics Data System (ADS)

    Mari, Romain; Seto, Ryohei; Morris, Jeffrey F.; Denn, Morton M.

    2015-05-01

    The discontinuous shear thickening (DST) of dense suspensions is a remarkable phenomenon in which the viscosity can increase by several orders of magnitude at a critical shear rate. It has the appearance of a first-order phase transition between two hypothetical "states" that we have recently identified as Stokes flows with lubricated or frictional contacts, respectively. Here we extend the analogy further by means of stress-controlled simulations and show the existence of a nonmonotonic steady-state flow curve analogous to a nonmonotonic equation of state. While we associate DST with an S -shaped flow curve, at volume fractions above the shear jamming transition the frictional state loses flowability and the flow curve reduces to an arch, permitting the system to flow only at small stresses. Whereas a thermodynamic transition leads to phase separation in the coexistence region, we observe a uniform shear flow all along the thickening transition. A stability analysis suggests that uniform shear may be mechanically stable for the small Reynolds numbers and system sizes in a rheometer.

  9. Dynamics of Discontinuous Shear Thickening suspensions

    NASA Astrophysics Data System (ADS)

    Brown, Eric

    2015-03-01

    Concentrated suspensions of hard particles such as cornstarch in water exhibit Discontinuous Shear Thickening, in which an increasing shear rate drives a transition from liquid- to solid-like mechanical behavior. In steady-state shear this phenomena is a result of a dynamic version of jamming in which forces are transmitted along particle contact networks that span to system boundaries and repeatedly form and break up. Several dynamic phenomena observed in such suspensions have long been assumed to be a consequence of this shear thickening, but cannot be explained as a direct result of shear thickening; for example a uniquely strong impact response which allows a person to run on the fluid surface. We perform experiments in which a concentrated suspension is subjected to transient impact. We find that the strong impact response is due a short-lived jammed contact network spanning to the boundaries and a delay time required for this dynamically jammed region to propagate to the boundary. The resulting ability of this system-spanning solid-like region to support loads can explain the ability of a person to run on the surface of these fluids. This delay before a solid-like response may also explain several other dynamic phenomena observed in these fluids.

  10. Ultrasonic characterization of shear thickening suspensions

    NASA Astrophysics Data System (ADS)

    Johnson, Benjamin Lenihan

    This dissertation describes the characterization of an inherently inhomogeneous medium capable of shear thickening. An aqueous suspension of cornstarch represents an important exemplar of such physical systems. The physics underlying the behavior of such shear thickening suspensions is incompletely understood. Characterization of these suspensions may provide valuable clues into the underlying mechanisms that result in shear thickening behavior. The goal of this thesis is to characterize the acoustic properties of suspensions of cornstarch in density-matched cesium chloride aqueous solutions. A review of the literature indicated that almost no information concerning the ultrasonic characteristics of suspensions of starches had been reported other than studies monitoring the gelatinization of starches not relevant to the shear stiffening of ungelatinized suspensions. Each chapter began with a discussion and validation of the specific experimental techniques and methods of analysis necessary for each type of measurement. Ultrasonic measurement of the group velocity, the frequency-dependent attenuation properties, the frequency-dependent phase velocity, and the frequency-dependent backscatter properties of the suspensions of cornstarch are reported. Initially counterintuitive results including negative (phase velocity) dispersion and a decrease in the measured backscatter coefficient with increasing particle concentration are understood in terms of widely accepted physical models. In sum, these studies represent an advancement of the understanding of the physics underlying the interaction between ultrasound and suspensions and lay the groundwork for future studies probing the physics of the shear thickening.

  11. Colloidal Aggregate Structure under Shear by USANS

    NASA Astrophysics Data System (ADS)

    Chatterjee, Tirtha; van Dyk, Antony K.; Ginzburg, Valeriy V.; Nakatani, Alan I.

    2015-03-01

    Paints are complex formulations of polymeric binders, inorganic pigments, dispersants, surfactants, colorants, rheology modifiers, and other additives. A commercially successful paint exhibits a desired viscosity profile over a wide shear rate range from 10-5 s-1 for settling to >104 s-1 for rolling, and spray applications. Understanding paint formulation structure is critical as it governs the paint viscosity profile. However, probing paint formulation structure under shear is a challenging task due to the formulation complexity containing structures with different hierarchical length scales and their alterations under the influence of an external flow field. In this work mesoscale structures of paint formulations under shear are investigated using Ultra Small-Angle Neutron Scattering (rheo-USANS). Contrast match conditions were utilized to independently probe the structure of latex binder particle aggregates and the TiO2 pigment particle aggregates. Rheo-USANS data revealed that the aggregates are fractal in nature and their self-similarity dimensions and correlations lengths depend on the chemistry of the binder particles, the type of rheology modifier present and the shear stress imposed upon the formulation. These results can be explained in the framework of diffusion and reaction limited transient aggregates structure evolution under simple shear.

  12. Wind Energy Markets, 2. edition

    SciTech Connect

    2007-11-15

    The report provides an overview of the global market for wind energy, including a concise look at wind energy development in key markets including installations, government incentives, and market trends. Topics covered include: an overview of wind energy including the history of wind energy production and the current market for wind energy; key business drivers of the wind energy market; barriers to the growth of wind energy; key wind energy trends and recent developments; the economics of wind energy, including cost, revenue, and government subsidy components; regional and national analyses of major wind energy markets; and, profiles of key wind turbine manufacturers.

  13. Atmospheric Stability Impacts on Power Curves of Tall Wind Turbines - An Analysis of a West Coast North American Wind Farm

    SciTech Connect

    Wharton, S; Lundquist, J K

    2010-02-22

    Tall wind turbines, with hub heights at 80 m or above, can extract large amounts of energy from the atmosphere because they are likely to encounter higher wind speeds, but they face challenges given the complex nature of wind flow and turbulence at these heights in the boundary layer. Depending on whether the boundary layer is stable, neutral, or convective, the mean wind speed, direction, and turbulence properties may vary greatly across the tall turbine swept area (40 to 120 m AGL). This variability can cause tall turbines to produce difference amounts of power during time periods with identical hub height wind speeds. Using meteorological and power generation data from a West Coast North American wind farm over a one-year period, our study synthesizes standard wind park observations, such as wind speed from turbine nacelles and sparse meteorological tower observations, with high-resolution profiles of wind speed and turbulence from a remote sensing platform, to quantify the impact of atmospheric stability on power output. We first compare approaches to defining atmospheric stability. The standard, limited, wind farm operations enable the calculation only of a wind shear exponent ({alpha}) or turbulence intensity (I{sub U}) from cup anemometers, while the presence at this wind farm of a SODAR enables the direct observation of turbulent kinetic energy (TKE) throughout the turbine rotor disk. Additionally, a nearby research meteorological station provided observations of the Obukhov length, L, a direct measure of atmospheric stability. In general, the stability parameters {alpha}, I{sub U}, and TKE are in high agreement with the more physically-robust L, with TKE exhibiting the best agreement with L. Using these metrics, data periods are segregated by stability class to investigate power performance dependencies. Power output at this wind farm is highly correlated with atmospheric stability during the spring and summer months, while atmospheric stability exerts little impact on power output during the winter and autumn periods. During the spring and summer seasons, power output for a given wind speed was significantly higher during stable conditions and significantly lower during strongly convective conditions: power output differences approached 20% between stable and convective regimes. The dependency of stability on power output was apparent only when both turbulence and the shape of the wind speed profile were considered. Turbulence is one of the mechanisms by which atmospheric stability affects a turbine's power curve at this particular site, and measurements of turbulence can yield actionable insights into wind turbine behavior.

  14. The winds of change

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind-based power generation has been growing steadily in the United States and around the world, and this growth will continue—and accelerate—in the future, as the following background statistics demonstrate. The U.S. wind industry installed 8,358 megawatts (MW) of new wind generating capacity in 20...

  15. NATIONAL WIND TECHNOLOGY CENTER

    E-print Network

    NATIONAL WIND TECHNOLOGY CENTER 35 YEARS OF INNOVATION Leading theWay to a Clean Energy FutureRenewableEnergy,operatedbytheAllianceforSustainableEnergy,LLC. #12;The NWTC goes to great lengths--and heights-- to help wind turbine manufacturers develop advanced.S. Department of Energy (DOE) National Wind Technology Center (NWTC) at the National Renewable Energy Laboratory

  16. CONGRESSIONAL BRIEFING Offshore Wind

    E-print Network

    Firestone, Jeremy

    CONGRESSIONAL BRIEFING Offshore Wind Lessons Learned from Europe: Reducing Costs and Creating Jobs Thursday, June 12, 2014 Capitol Visitors Center, Room SVC 215 Enough offshore wind capacity to power six the past decade. What has Europe learned that is applicable to a U.S. effort to deploy offshore wind off

  17. Energy from the Wind

    ERIC Educational Resources Information Center

    Pelka, David G.; And Others

    1978-01-01

    The large-scale generation of electrical power by wind turbine fields is discussed. It is shown that the maximum power that can be extracted by a wind turbine is 16/27 of the power available in the wind. (BB)

  18. Large wind turbine generators

    NASA Technical Reports Server (NTRS)

    Thomas, R. L.; Donovon, R. M.

    1978-01-01

    The development associated with large wind turbine systems is briefly described. The scope of this activity includes the development of several large wind turbines ranging in size from 100 kW to several megawatt levels. A description of the wind turbine systems, their programmatic status and a summary of their potential costs is included.

  19. Wind Economic Development (Postcard)

    SciTech Connect

    Not Available

    2011-08-01

    The U.S. Department of Energy's Wind Powering America initiative provides information on the economic development benefits of wind energy. This postcard is a marketing piece that stakeholders can provide to interested parties; it will guide them to the economic development benefits section on the Wind Powering America website.

  20. Wind farm electrical system

    DOEpatents

    Erdman, William L.; Lettenmaier, Terry M.

    2006-07-04

    An approach to wind farm design using variable speed wind turbines with low pulse number electrical output. The output of multiple wind turbines are aggregated to create a high pulse number electrical output at a point of common coupling with a utility grid network. Power quality at each individual wind turbine falls short of utility standards, but the aggregated output at the point of common coupling is within acceptable tolerances for utility power quality. The approach for aggregating low pulse number electrical output from multiple wind turbines relies upon a pad mounted transformer at each wind turbine that performs phase multiplication on the output of each wind turbine. Phase multiplication converts a modified square wave from the wind turbine into a 6 pulse output. Phase shifting of the 6 pulse output from each wind turbine allows the aggregated output of multiple wind turbines to be a 24 pulse approximation of a sine wave. Additional filtering and VAR control is embedded within the wind farm to take advantage of the wind farm's electrical impedence characteristics to further enhance power quality at the point of common coupling.

  1. Wind Power Now!

    ERIC Educational Resources Information Center

    Inglis, David Rittenhouse

    1975-01-01

    The government promotes and heavily subsidizes research in nuclear power plants. Federal development of wind power is slow in comparison even though much research with large wind-electric machines has already been conducted. Unless wind power programs are accelerated it will not become a major energy alternative to nuclear power. (MR)

  2. Power from the Wind

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2004-01-01

    Wind energy is the fastest-growing renewable energy source in the world. Over the last 20 years, the wind industry has done a very good job of engineering machines, improving materials, and economies of production, and making this energy source a reality. Like all renewable energy forms, wind energy's successful application is site specific. Also,…

  3. Wind power outlook 2006

    SciTech Connect

    anon.

    2006-04-15

    This annual brochure provides the American Wind Energy Association's up-to-date assessment of the wind industry in the United States. This 2006 general assessment shows positive signs of growth, use and acceptance of wind energy as a vital component of the U.S. energy mix.

  4. High-shear-rate capillary viscometer for inkjet inks

    SciTech Connect

    Wang Xi; Carr, Wallace W.; Bucknall, David G.; Morris, Jeffrey F.

    2010-06-15

    A capillary viscometer developed to measure the apparent shear viscosity of inkjet inks at high apparent shear rates encountered during inkjet printing is described. By using the Weissenberg-Rabinowitsch equation, true shear viscosity versus true shear rate is obtained. The device is comprised of a constant-flow generator, a static pressure monitoring device, a high precision submillimeter capillary die, and a high stiffness flow path. The system, which is calibrated using standard Newtonian low-viscosity silicone oil, can be easily operated and maintained. Results for measurement of the shear-rate-dependent viscosity of carbon-black pigmented water-based inkjet inks at shear rates up to 2x10{sup 5} s{sup -1} are discussed. The Cross model was found to closely fit the experimental data. Inkjet ink samples with similar low-shear-rate viscosities exhibited significantly different shear viscosities at high shear rates depending on particle loading.

  5. A dynamic jamming point for shear thickening suspensions

    NASA Astrophysics Data System (ADS)

    Brown, Eric; Jaeger, Heinrich

    2008-11-01

    Densely packed suspensions can shear thicken, in which the viscosity increases with shear rate. We performed rheometry measurements on two model systems: corn starch in water and glass spheres in oils. In both systems we observed shear thickening up to a critical packing fraction ?c (=0.55 for spherical grains) above which the flow abruptly transitions to shear thinning. The viscosity and yield stress diverge as power laws at ?c. Extrapolating the dynamic ranges of shear rate and stress in the shear thickening regime up to ?c suggests a finite change in shear stress with zero change in shear rate. This is a dynamic analog to the jamming point with a yield stress at zero shear rate.

  6. Relation between ordering and shear thinning in colloidal suspensions.

    PubMed

    Xu, Xinliang; Rice, Stuart A; Dinner, Aaron R

    2013-03-01

    Colloidal suspensions exhibit shear thinning and shear thickening. The most common interpretation of these phenomena identifies layering of the fluid perpendicular to the shear gradient as the driver for the observed behavior. However, studies of the particle configurations associated with shear thinning and thickening cast doubt on that conclusion and leave unsettled whether these nonequilibrium phenomena are caused primarily by correlated particle motions or by changes in particle packing structure. We report the results of stokesian dynamics simulations of suspensions of hard spheres that illuminate the relation among the suspension viscosity, shear rate, and particle configuration. Using a recently introduced sampling technique for nonequilibrium systems, we show that shear thinning can be decoupled from layering, thereby eliminating layering as the driver for shear thinning. In contrast, we find that there is a strong correlation between shear thinning and a two-particle measure of the shear stress. Our results are consistent with a recent experimental study. PMID:23431185

  7. Iosipescu shear properties of graphite fabric/epoxy composite laminates

    NASA Technical Reports Server (NTRS)

    Walrath, D. E.; Adams, D. F.

    1985-01-01

    The Iosipescu shear test method is used to measure the in-plane and interlaminar shear properties of four T300 graphite fabric/934 epoxy composite materials. Different weave geometries tested include an Oxford weave, a 5-harness satin weave, an 8-harness satin weave, and a plain weave with auxiliary warp yarns. Both orthogonal and quasi-isotropic layup laminates were tested. In-plane and interlaminar shear properties are obtained for laminates of all four fabric types. Overall, little difference in shear properties attributable to the fabric weave pattern is observed. The auxiliary warp material is significantly weaker and less stiff in interlaminar shear parallel to its fill direction. A conventional strain gage extensometer is modified to measure shear strains for use with the Iosipescu shear test. While preliminary results are encouraging, several design iterations failed to produce a reliable shear transducer prototype. Strain gages are still the most reliable shear strain transducers for use with this test method.

  8. THE EVOLUTION OF THE TWIST SHEAR AND DIP SHEAR DURING X-CLASS FLARE OF 2006 DECEMBER 13: HINODE OBSERVATIONS

    SciTech Connect

    Gosain, Sanjay; Venkatakrishnan, P.

    2010-09-10

    The non-potentiality of solar magnetic fields is traditionally measured in terms of a magnetic shear angle, i.e., the angle between the observed and potential field azimuths. Here, we introduce another measure of the shear that has not been previously studied in solar active regions, i.e., the one that is associated with the inclination angle of the magnetic field. This form of the shear, which we call 'dip shear', can be calculated by taking the difference between the observed and the potential field inclination. In this Letter, we study the evolution of the dip shear as well as the conventional twist shear in a {delta}-sunspot using high-resolution vector magnetograms from the Hinode space mission. We monitor these shears in a penumbral region located close to a flaring site during 2006 December 12 and 13. It is found that (1) the penumbral area close to the flaring site shows a high value of the twist shear and dip shear as compared with other parts of the penumbra, (2) after the flare, the value of the dip shear drops in this region while the twist shear tends to increase, (3) the dip shear and twist shear are correlated such that pixels with a large twist shear also tend to exhibit a large dip shear, and (4) the correlation between the twist shear and dip shear is tighter after the flare. The present study suggests that monitoring the twist shear alone during the flare is not sufficient, but we need to monitor it together with the dip shear.

  9. Shear Viscosity of a Hot Pion Gas

    E-print Network

    Robert Lang; Norbert Kaiser; Wolfram Weise

    2012-09-04

    The shear viscosity of an interacting pion gas is studied using the Kubo formalism as a microscopic description of thermal systems close to global equilibrium. We implement the skeleton expansion in order to approximate the retarded correlator of the viscous part of the energy-momentum tensor. After exploring this in $g\\phi^4$ theory we show how the skeleton expansion can be consistently applied to pions in chiral perturbation theory. The shear viscosity $\\eta$ is determined by the spectral width, or equivalently, the mean free path of pions in the heat bath. We derive a new analytical result for the mean free path which is well-conditioned for numerical evaluation and discuss the temperature and pion-mass dependence of the mean free path and the shear viscosity. The ratio $\\eta/s$ of the interacting pion gas exceeds the lower bound $1/4\\pi$ from AdS/CFT correspondence.

  10. Shear viscosity in magnetized neutron star crust

    E-print Network

    Ofengeim, D D

    2015-01-01

    The electron shear viscosity due to Coulomb scattering of degenerate electrons by atomic nuclei throughout a magnetized neutron star crust is calculated. The theory is based on the shear viscosity coefficient calculated neglecting magnetic fields but taking into account gaseous, liquid and solid states of atomic nuclei, multiphonon scattering processes, and finite sizes of the nuclei albeit neglecting the effects of electron band structure. The effects of strong magnetic fields are included in the relaxation time approximation with the effective electron relaxation time taken from the field-free theory. The viscosity in a magnetized matter is described by five shear viscosity coefficients. They are calculated and their dependence on the magnetic field and other parameters of dense matter is analyzed. Possible applications and open problems are outlined.

  11. Measuring shear modulus of individual fibers

    NASA Astrophysics Data System (ADS)

    Behlow, Herbert; Saini, Deepika; Oliviera, Luciana; Skove, Malcolm; Rao, Apparao

    2014-03-01

    Fiber technology has advanced to new heights enabling tailored mechanical properties. For reliable fiber applications their mechanical properties must be well characterized at the individual fiber level. Unlike the tensile modulus, which can be well studied in a single fiber, the present indirect and dynamic methods of measuring the shear properties of fibers suffer from various disadvantages such as the interaction between fibers and the influence of damping. In this talk, we introduce a quasi-static method to directly measure the shear modulus of a single micron-sized fiber. Our simple and inexpensive setup yields a shear modulus of 16 and 2 GPa for a single IM7 carbon fiber and a Kevlar fiber, respectively. Furthermore, our setup is also capable of measuring the creep, hysteresis and the torsion coefficient, and examples of these will be presented.

  12. Athermal analogue of sheared dense Brownian suspensions

    E-print Network

    M. Trulsson; M. Bouzid; J. Kurchan; E. Clement; P. Claudin; B. Andreotti

    2015-06-30

    The rheology of dense Brownian suspensions of hard spheres is investigated numerically beyond the low shear rate Newtonian regime. We analyze an athermal analogue of these suspensions, with an effective logarithmic repulsive potential representing the vibrational entropic forces. We show that both systems present the same rheology without adjustable parameters. Moreover, all rheological responses display similar Herschel-Bulkley relations once the shear stress and the shear rate are respectively rescaled by a characteristic stress scale and by a microscopic reorganization time-scale, both related to the normal confining pressure. This pressure-controlled approach, originally developed for granular flows, reveals a striking physical analogy between the colloidal glass transition and granular jamming.

  13. Athermal analogue of sheared dense Brownian suspensions

    NASA Astrophysics Data System (ADS)

    Trulsson, Martin; Bouzid, Mehdi; Kurchan, Jorge; Clément, Eric; Claudin, Philippe; Andreotti, Bruno

    2015-07-01

    The rheology of dense Brownian suspensions of hard spheres is investigated numerically beyond the low-shear-rate Newtonian regime. We analyze an athermal analogue of these suspensions, with an effective logarithmic repulsive potential representing the vibrational entropic forces. We show that both systems present the same rheology without adjustable parameters. Moreover, all rheological responses display similar Herschel-Bulkley relations once the shear stress and the shear rate are respectively rescaled by a characteristic stress scale and by a microscopic reorganization time scale, both related to the normal confining pressure. This pressure-controlled approach, originally developed for granular flows, reveals a striking physical analogy between the colloidal glass transition and granular jamming.

  14. Strength of Footing with Punching Shear Preventers

    PubMed Central

    Lee, Sang-Sup; Moon, Jiho; Park, Keum-Sung; Bae, Kyu-Woong

    2014-01-01

    The punching shear failure often governs the strength of the footing-to-column connection. The punching shear failure is an undesirable failure mode, since it results in a brittle failure of the footing. In this study, a new method to increase the strength and ductility of the footing was proposed by inserting the punching shear preventers (PSPs) into the footing. The validation and effectiveness of PSP were verified through a series of experimental studies. The nonlinear finite element analysis was then performed to demonstrate the failure mechanism of the footing with PSPs in depth and to investigate the key parameters that affect the behavior of the footing with PSPs. Finally, the design recommendations for the footing with PSPs were suggested. PMID:25401141

  15. Undulatory Swimming in Shear-thinning Fluids

    NASA Astrophysics Data System (ADS)

    Shen, Xiaoning; Gagnon, David; Arratia, Paulo

    2012-11-01

    Many fluids in which microorganisms move, feed, and reproduce possess shear-rate dependent viscosity behavior (e.g. shear-thinning). Such fluids include wet soil, clay suspension, mucus, and gels. In this talk, we experimentally investigate the effects of shear-rate dependent viscosity on the swimming behavior of the nematode Caenorhabditis elegans using velocimetry and tracking methods. Here, aqueous solutions of xanthan gum, which is a rod-like stiff polymer, are used with concentrations varying from the semi-dilute to the concentrated regime. The data is compared to swimming in simple, Newtonian fluids. We find that the nematode swims at an approximately constant speed in the semi-dilute regime. Surprisingly, the nematode exhibits 40% increases in swimming speed once immersed in a concentrated solution. The enhancement in swimming speed seems to be related to the dynamics of rod-like polymer networks formed in concentrated solutions. This work was supported by NSF-CAREER (CBET)-0954084.

  16. Pressure anisotropy generation in a magnetized plasma configuration with a shear flow velocity

    E-print Network

    De Camillis, S; Califano, F; Pegoraro, F

    2015-01-01

    The nonlinear evolution of the Kelvin Helmholtz instability in a magnetized plasma with a perpendicular flow close to, or in, the supermagnetosonic regime can produce a significant parallel-to-perpendicular pressure anisotropy. This anisotropy, localized inside the flow shear region, can make the configuration unstable either to the mirror or to the firehose instability and, in general, can affect the development of the KHI. The interface between the solar wind and the Earth's magnetospheric plasma at the magnetospheric equatorial flanks provides a relevant setting for the development of this complex nonlinear dynamics.

  17. Shear banding in soft glassy materials

    NASA Astrophysics Data System (ADS)

    Fielding, S. M.

    2014-10-01

    Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic ‘glassy’ features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike.

  18. The many faces of shear Alfven waves

    SciTech Connect

    Gekelman, W.; Vincena, S.; Van Compernolle, B.; Morales, G. J.; Maggs, J. E.; Pribyl, P.; Carter, T. A.

    2011-05-15

    One of the fundamental waves in magnetized plasmas is the shear Alfven wave. This wave is responsible for rearranging current systems and, in fact all low frequency currents in magnetized plasmas are shear waves. It has become apparent that Alfven waves are important in a wide variety of physical environments. Shear waves of various forms have been a topic of experimental research for more than fifteen years in the large plasma device (LAPD) at UCLA. The waves were first studied in both the kinetic and inertial regimes when excited by fluctuating currents with transverse dimension on the order of the collisionless skin depth. Theory and experiment on wave propagation in these regimes is presented, and the morphology of the wave is illustrated to be dependent on the generation mechanism. Three-dimensional currents associated with the waves have been mapped. The ion motion, which closes the current across the magnetic field, has been studied using laser induced fluorescence. The wave propagation in inhomogeneous magnetic fields and density gradients is presented as well as effects of collisions and reflections from boundaries. Reflections may result in Alfvenic field line resonances and in the right conditions maser action. The waves occur spontaneously on temperature and density gradients as hybrids with drift waves. These have been seen to affect cross-field heat and plasma transport. Although the waves are easily launched with antennas, they may also be generated by secondary processes, such as Cherenkov radiation. This is the case when intense shear Alfven waves in a background magnetoplasma are produced by an exploding laser-produced plasma. Time varying magnetic flux ropes can be considered to be low frequency shear waves. Studies of the interaction of multiple ropes and the link between magnetic field line reconnection and rope dynamics are revealed. This manuscript gives us an overview of the major results from these experiments and provides a modern prospective for the earlier studies of shear Alfven waves.

  19. Shear banding in soft glassy materials.

    PubMed

    Fielding, S M

    2014-10-01

    Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic 'glassy' features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike. PMID:25303030

  20. Optimisation of Shear Strengthened Reinforced Concrete Beams

    E-print Network

    Yapa, Hiran D.; Lees, Janet M.

    2014-05-21

    associated with flexural failure Vmax, Vmin velocity limits Vt velocity at the tth iteration v shear stress vci shear stress along the crack w crack width wIF inertia factor X distance from support Xrange range Xt position at the tth iteration xopt_algo, yopt... due to increased loading, corrosion of the internal steel reinforcement and less conservative designs based on earlier design codes (Lees et al., 2002). A lack of strength leads to the need either to impose weight limits, to strengthen the structure...

  1. Enhancing Rotational Diffusion Using Oscillatory Shear

    NASA Astrophysics Data System (ADS)

    Leahy, Brian D.; Cheng, Xiang; Ong, Desmond C.; Liddell-Watson, Chekesha; Cohen, Itai

    2013-05-01

    Taylor dispersion—shear-induced enhancement of translational diffusion—is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced for anisotropic particles in oscillatory shear. This enhancement arises from variations in the particle’s rotation (Jeffery orbit) and depends on the strain amplitude, rate, and particle aspect ratio in a manner that is distinct from the translational diffusion. This separate tunability of translational and rotational diffusion opens the door to new techniques for controlling positions and orientations of suspended anisotropic colloids.

  2. Shear viscosity coefficient of liquid lanthanides

    SciTech Connect

    Patel, H. P. Thakor, P. B. Prajapati, A. V.; Sonvane, Y. A.

    2015-05-15

    Present paper deals with the computation of shear viscosity coefficient (?) of liquid lanthanides. The effective pair potential v(r) is calculated through our newly constructed model potential. The Pair distribution function g(r) is calculated from PYHS reference system. To see the influence of local field correction function, Hartree (H), Tailor (T) and Sarkar et al (S) local field correction function are used. Present results are compared with available experimental as well as theoretical data. Lastly, we found that our newly constructed model potential successfully explains the shear viscosity coefficient (?) of liquid lanthanides.

  3. Shear Viscosity of a Unitary Fermi Gas

    E-print Network

    Gabriel Wlaz?owski; Piotr Magierski; Joaquín E. Drut

    2012-07-12

    We present the first ab initio determination of the shear viscosity eta of the Unitary Fermi Gas, based on finite temperature quantum Monte Carlo calculations and the Kubo linear-response formalism. We determine the temperature dependence of the shear viscosity to entropy density ratio eta/s. The minimum of eta/s appears to be located above the critical temperature for the superfluid-to-normal phase transition with the most probable value being eta/s approx 0.2 hbar/kB, which almost saturates the Kovtun-Son-Starinets universal value hbar/(4 pi kB).

  4. Asymmetric velocity correlations in shearing media

    E-print Network

    Peter Olsson

    2010-05-11

    A model of soft frictionless disks in two dimensions at zero temperature is simulated with a shearing dynamics to study various kinds of asymmetries in sheared systems. We examine both single particle properties, the spatial velocity correlation function, and a correlation function designed to separate clockwise and counter-clockwise rotational fields from one another. Among the rich and interesting behaviors we find that the velocity correlation along the two different diagonals corresponding to compression and dilation, respectively, are almost identical and, furthermore, that a feature in one of the correlation functions is directly related to irreversible plastic events.

  5. Energetic particle acceleration in shear layers

    E-print Network

    M. Ostrowski

    1999-11-05

    A plasma velocity shear layer and/or a tangential flow discontinuity provide conditions allowing for energetic particle acceleration. We review such acceleration processes acting both in non-relativistic and in relativistic flows. In heliospheric conditions shear layers can provide particles with energies compatible with the observed values (from several keV up to MeV), while in relativistic extragalactic jets proton energies even in excess of 10^{19} eV can be obtained. Application of the discussed theory to particular astrophysical objects is severely limited by inadequate knowledge of local physical conditions.

  6. Shear-flow Effects in Open Traps

    SciTech Connect

    Beklemishev, A. D.

    2008-11-01

    Interaction between shear flows and plasma instabilities and turbulence in open traps can lead to improved confinement both in experiments and in simulations. Shear flows, driven by biasing end-plates and limiters or by off-axis electron heating, in combination with the finite-larmor-radius (FLR) effects are shown to be efficient in confining plasmas even with unstable flute modes. Interpretation of the observed effects as the ''vortex confinement,'' i.e., confinement of the plasma core in the dead-flow zone of the driven vortex, is shown to agree well with simulations.

  7. Continuum stress characteristics inside shear bands

    NASA Astrophysics Data System (ADS)

    Tordesillas, Antoinette; Peters, John F.; Shi, Jingyu

    2013-06-01

    A defining aspect of the large strain, fully developed plastic flow regime, or "critical state", for granular materials undergoing localized failure is the continual growth of new force chains amidst collapse by buckling of old force chains in the persistent shear band. This paper explores the constitutive response inside shear bands, in particular, the birth-death evolution of force chains for a Cosserat medium, whereby closure relationships for stresses and couple stresses satisfy the isostatic condition, albeit in a spatiotemporal average sense only. The continuum stress-equilibrium relations comprise a hyperbolic system of partial differential equations giving rise to characteristic lines referred to in the literature as stress chains.

  8. Optimization of Wind Turbine Airfoils/Blades and Wind Farm Layouts

    NASA Astrophysics Data System (ADS)

    Chen, Xiaomin

    Shape optimization is widely used in the design of wind turbine blades. In this dissertation, a numerical optimization method called Genetic Algorithm (GA) is applied to address the shape optimization of wind turbine airfoils and blades. In recent years, the airfoil sections with blunt trailing edge (called flatback airfoils) have been proposed for the inboard regions of large wind-turbine blades because they provide several structural and aerodynamic performance advantages. The FX, DU and NACA 64 series airfoils are thick airfoils widely used for wind turbine blade application. They have several advantages in meeting the intrinsic requirements for wind turbines in terms of design point, off-design capabilities and structural properties. This research employ both single- and multi-objective genetic algorithms (SOGA and MOGA) for shape optimization of Flatback, FX, DU and NACA 64 series airfoils to achieve maximum lift and/or maximum lift to drag ratio. The commercially available software FLUENT is employed for calculation of the flow field using the Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a two-equation Shear Stress Transport (SST) turbulence model and a three equation k-kl-o turbulence model. The optimization methodology is validated by an optimization study of subsonic and transonic airfoils (NACA0012 and RAE 2822 airfoils). In this dissertation, we employ DU 91-W2-250, FX 66-S196-V1, NACA 64421, and Flat-back series of airfoils (FB-3500-0050, FB-3500-0875, and FB-3500-1750) and compare their performance with S809 airfoil used in NREL Phase II and III wind turbines; the lift and drag coefficient data for these airfoils sections are available. The output power of the turbine is calculated using these airfoil section blades for a given B and lambda and is compared with the original NREL Phase II and Phase III turbines using S809 airfoil section. It is shown that by a suitable choice of airfoil section of HAWT blade, the power generated by the turbine can be significantly increased. Parametric studies are also conducted by varying the turbine diameter. In addition, a simplified dynamic inflow model is integrated into the BEM theory. It is shown that the improved BEM theory has superior performance in capturing the instantaneous behavior of wind turbines due to the existence of wind turbine wake or temporal variations in wind velocity. The dissertation also considers the Wind Farm layout optimization problem using a genetic algorithm. Both the Horizontal --Axis Wind Turbines (HAWT) and Vertical-Axis Wind Turbines (VAWT) are considered. The goal of the optimization problem is to optimally position the turbines within the wind farm such that the wake effects are minimized and the power production is maximized. The reasonably accurate modeling of the turbine wake is critical in determination of the optimal layout of the turbines and the power generated. For HAWT, two wake models are considered; both are found to give similar answers. For VAWT, a very simple wake model is employed. Finally, some preliminary investigation of shape optimization of 3D wind turbine blades at low Reynolds numbers is conducted. The optimization employs a 3D straight untapered wind turbine blade with cross section of NACA 0012 airfoils as the geometry of baseline blade. The optimization objective is to achieve maximum Cl/Cd as well as maximum Cl. The multi-objective genetic algorithm is employed together with the commercially available software FLUENT for calculation of the flow field using the Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a one-equation Sparlart-Allmaras turbulence model. The results show excellent performance of the optimized wind turbine blade and indicate the feasibility of optimization on real wind turbine blades with more complex shapes in the future. (Abstract shortened by UMI.)

  9. Hydrodynamic and contact contributions to shear thickening in colloidal suspensions

    E-print Network

    Neil Y. C. Lin; Ben M. Guy; Michiel Hermes; Chris Ness; Jin Sun; Wilson C. K. Poon; Itai Cohen

    2015-09-09

    Shear thickening is a widespread phenomenon in suspension flow that, despite sustained study, is still the subject of much debate. The longstanding view that shear thickening is due to hydrodynamic clusters has been challenged by recent theory and simulations suggesting that contact forces dominate, not only in discontinuous, but also in continuous shear thickening. Here, we settle this dispute using shear reversal experiments on micron-sized silica and latex colloidal particles to measure directly the hydrodynamic and contact force contributions to shear thickening. We find that contact forces dominate even continuous shear thickening. Computer simulations show that these forces most likely arise from frictional interactions.

  10. Analysis of shear test method for composite laminates

    NASA Technical Reports Server (NTRS)

    Bergner, H. W., Jr.; Davis, J. G., Jr.; Herakovich, C. T.

    1977-01-01

    An elastic plane stress finite element analysis of the stress distributions in four flat test specimens for in-plane shear response of composite materials subjected to mechanical or thermal loads is presented. The shear test specimens investigated include: slotted coupon, cross beam, losipescu, and rail shear. Results are presented in the form of normalized shear contour plots for all three in-plane stess components. It is shown that the cross beam, losipescu, and rail shear specimens have stress distributions which are more than adequate for determining linear shear behavior of composite materials. Laminate properties, core effects, and fixture configurations are among the factors which were found to influence the stress distributions.

  11. Two-Phase Shear Band Structures at Uniform Stress

    NASA Astrophysics Data System (ADS)

    Britton, Melanie M.; Callaghan, Paul T.

    1997-06-01

    Using NMR microscopy we measure the velocity distribution for a wormlike surfactant solution in the gap of a small angle cone-and-plate rheometer. This system, cetylpyridinium chloride/sodium salicylate 100 mM/60 mM, exhibits biphasic shear band structure when the applied shear rate exceeds the critical rate of strain beyond which a plateau is observed in the shear stress. The structure is characterized by two low/high shear interfaces and the region of high shear evolves by increasing width as the average gap shear is increased.

  12. Hydrodynamic and contact contributions to shear thickening in colloidal suspensions

    E-print Network

    Lin, Neil Y C; Hermes, Michiel; Ness, Chris; Sun, Jin; Poon, Wilson C K; Cohen, Itai

    2015-01-01

    Shear thickening is a widespread phenomenon in suspension flow that, despite sustained study, is still the subject of much debate. The longstanding view that shear thickening is due to hydrodynamic clusters has been challenged by recent theory and simulations suggesting that contact forces dominate, not only in discontinuous, but also in continuous shear thickening. Here, we settle this dispute using shear reversal experiments on micron-sized silica and latex colloidal particles to measure directly the hydrodynamic and contact force contributions to shear thickening. We find that contact forces dominate even continuous shear thickening. Computer simulations show that these forces most likely arise from frictional interactions.

  13. Shear-induced conformation change in ?-crystalline nylon6

    NASA Astrophysics Data System (ADS)

    Arabnejad, Saeid; Manzhos, Sergei; He, Chaobin; Shim, V. P. W.

    2014-12-01

    A study of shear deformation of ?-crystalline nylon6 is undertaken, using dispersion-corrected density functional theory. The shear stress-strain relationship and shear strength for interlayer shear deformation are computed. A conformation change induced by shear is identified along twinning deformation, whereby the conformation of chains, specifically the location of non-H-bonded hydrogen atoms, changes continuously. This paves a way for the modulation of properties of this group of materials by small shear deformation, if the non-H-bonded hydrogens are chemically substituted to form non-equivalent conformations when deformed.

  14. Wind Turbine Structural Dynamics

    NASA Technical Reports Server (NTRS)

    Miller, D. R. (editor)

    1978-01-01

    A workshop on wind turbine structural dynamics was held to review and document current United States work on the dynamic behavior of large wind turbines, primarily of the horizontal-axis type, and to identify and discuss other wind turbine configurations that may have lower cost and weight. Information was exchanged on the following topics: (1) Methods for calculating dynamic loads; (2) Aeroelasticity stability (3) Wind loads, both steady and transient; (4) Critical design conditions; (5) Drive train dynamics; and (6) Behavior of operating wind turbines.

  15. Wind energy systems

    NASA Astrophysics Data System (ADS)

    Richardson, R. D.; McNerney, Gerald M.

    1993-03-01

    Wind energy has matured to a level of development where it is ready to become a generally accepted utility generation technology. A brief discussion of this development is presented, and the operating and design principles are discussed. Alternative designs for wind turbines and the tradeoffs that must be considered are briefly compared. Development of a wind energy system and the impacts on the utility network including frequency stability, voltage stability, and power quality are discussed. The assessment of wind power station economics and the key economic factors that determine the economic viability of a wind power plant are presented.

  16. Wind energy applications guide

    SciTech Connect

    anon.

    2001-01-01

    The brochure is an introduction to various wind power applications for locations with underdeveloped transmission systems, from remote water pumping to village electrification. It includes an introductory section on wind energy, including wind power basics and system components and then provides examples of applications, including water pumping, stand-alone systems for home and business, systems for community centers, schools, and health clinics, and examples in the industrial area. There is also a page of contacts, plus two specific example applications for a wind-diesel system for a remote station in Antarctica and one on wind-diesel village electrification in Russia.

  17. Shear wave mapping of skeletal muscle using shear wave wavefront reconstruction based on ultrasound color flow imaging

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Yoshiki; Yamamoto, Atsushi; Kasahara, Toshihiro; Iijima, Tomohiro; Yuminaka, Yasushi

    2015-07-01

    We have proposed a quantitative shear wave imaging technique for continuous shear wave excitation. Shear wave wavefront is observed directly by color flow imaging using a general-purpose ultrasonic imaging system. In this study, the proposed method is applied to experiments in vivo, and shear wave maps, namely, the shear wave phase map, which shows the shear wave propagation inside the medium, and the shear wave velocity map, are observed for the skeletal muscle in the shoulder. To excite the shear wave inside the skeletal muscle of the shoulder, a hybrid ultrasonic wave transducer, which combines a small vibrator with an ultrasonic wave probe, is adopted. The shear wave velocity of supraspinatus muscle, which is measured by the proposed method, is 4.11 ± 0.06 m/s (N = 4). This value is consistent with those obtained by the acoustic radiation force impulse method.

  18. Acute shear stress direction dictates adherent cell remodeling and verifies shear profile of spinning disk assays

    NASA Astrophysics Data System (ADS)

    Fuhrmann, Alexander; Engler, Adam J.

    2015-02-01

    Several methods have been developed to quantify population level changes in cell attachment strength given its large heterogeneity. One such method is the rotating disk chamber or ‘spinning disk’ in which a range of shear forces are applied to attached cells to quantify detachment force, i.e. attachment strength, which can be heterogeneous within cell populations. However, computing the exact force vectors that act upon cells is complicated by complex flow fields and variable cell morphologies. Recent observations suggest that cells may remodel their morphology and align during acute shear exposure, but contrary to intuition, shear is not orthogonal to the radial direction. Here we theoretically derive the magnitude and direction of applied shear and demonstrate that cells, under certain physiological conditions, align in this direction within minutes. Shear force magnitude is also experimentally verified which validates that for spread cells shear forces and not torque or drag dominate in this assay, and demonstrates that the applied force per cell area is largely independent of initial morphology. These findings suggest that direct quantified comparison of the effects of shear on a wide array of cell types and conditions can be made with confidence using this assay without the need for computational or numerical modeling.

  19. Quantification of Shear-Induced Platelet Activation: High Shear Stresses for Short Exposure Time.

    PubMed

    Ding, Jun; Chen, Zengsheng; Niu, Shuqiong; Zhang, Jiafeng; Mondal, Nandan K; Griffith, Bartley P; Wu, Zhongjun J

    2015-07-01

    Thrombosis and thromboembolism are the life-threatening clinical complications for patients supported or treated with prosthetic cardiovascular devices. The high mechanical shear stress within these devices is believed to be the major contributing factor to cause platelet activation (PA) and function alteration, leading to thrombotic events. There have been limited quantitative data on how the high mechanical shear stress causes platelet activation. In this study, shear-induced PA in the ranges of well-defined shear stress and exposure time relevant to cardiovascular devices was quantitatively characterized for human blood using two novel flow-through Couette-type blood shearing devices. Four markers of platelet activation-surface P-selectin (CD62p), platelet-derived microparticles (PMPs), platelet-monocyte aggregation (PMA), and soluble P-selectin-were measured by flow cytometry and enzyme-linked immunosorbent assay (ELISA), respectively. The results indicated that PA induced by high shear stresses with short exposure time could be reliably detected with surface P-selectin, and, to a lesser extent, PMPs rather than soluble P-selectin. It was also verified that PMA can be a highly sensitive indirect marker of platelet activation. The quantitative relationship between percentage of activated platelets indicated by surface P-selectin expression and shear stress/exposure time follows well the power law functional form. The coefficients of the power law models of PA based on surface P-selectin expression were derived. PMID:25808300

  20. Shear Wave Propagation Across Filled Joints with the Effect of Interfacial Shear Strength

    NASA Astrophysics Data System (ADS)

    Li, J. C.; Liu, T. T.; Li, H. B.; Liu, Y. Q.; Liu, B.; Xia, X.

    2015-07-01

    The thin-layer interface model for filled joints is extended to analyze shear wave propagation across filled rock joints when the interfacial shear strength between the filling material and the rocks is taken into account. During the wave propagation process, the two sides of the filled joint are welded with the adjacent rocks first and slide on each other when the shear stress on the joint is greater than the interfacial shear strength. By back analysis, the relation between the shear stress and the relative tangential deformation of the filled joints is obtained from the present approach, which is shown as a cycle parallelogram. Comparison between the present approach and the existing method based on the zero-thickness interface model indicates that the present approach is efficient to analyze shear wave propagation across rock joints with slippery behavior. The calculation results show that the slippery behavior of joints is related to the interfacial failure. In addition, the interaction between the shear stress wave and the two sides of the filling joint influences not only the wave propagation process but also the dynamic response of the filled joint.

  1. Laboratory study of fabric development in shearing till: The importance of effective pressure and shearing rate

    NASA Astrophysics Data System (ADS)

    Jacobson, William R.; Hooyer, Thomas S.

    2015-12-01

    Herein we present data on the shearing rate (glacier velocity) and effective pressure (difference between the ice-overburden pressure and pore-water pressure) in the development of magnetic fabric (anisotropy of magnetic susceptibility) using a rotary ring-shear device. A Wisconsin-age basal till was used in the experiments and deformed to its critical state at shear strains as high as 93. We also present data from hysteresis and high temperature susceptibility experiments to identify the magnetic carrier in the basal till. Results showed little change in fabric strength when varying the shearing rate in the speed range of 110-860 m year- 1. Moreover, the effective pressure tests also showed an inconsistency in fabric between 30 and 150 kPa; however, a slight strengthening effect was documented. Thus, the k1 magnetic fabric strength is independent of the shearing rate and effective pressure. This suggests that the fabric strength upon these variables cannot be used as a benchmark for estimating shear deformation to the geological record. The k1 fabric strength in this study; however, remained consistent with respect to other till particle fabric methods (e.g., sand and pebble) in which the same conclusion was drawn; all particles align parallel to the direction of shear and plunge mildly up glacier.

  2. Ultrasound velocimetry in a shear-thickening wormlike micellar solution: Evidence for the coexistence of radial and vorticity shear bands

    NASA Astrophysics Data System (ADS)

    Herle, V.; Manneville, S.; Fischer, P.

    2008-05-01

    We carried out pointwise local velocity measurements on 40mM cetylpyridinium chloride-sodium salicylate (CPyCl-NaSal) wormlike micellar solution using high-frequency ultrasound velocimetry in a Couette shear cell. The studied wormlike solution exhibits Newtonian, shear-thinning and shear-thickening rheological behavior in a stress-controlled environment. Previous rheology, flow visualization and small-angle light/neutron scattering experiments in the shear-thickening regime of this system showed the presence of stress-driven alternating transparent and turbid rings or vorticity bands along the axis of the Couette geometry. Through local velocity measurements we observe a homogeneous flow inside the 1mm gap of the Couette cell in the shear-thinning (stress-plateau) region. Only when the solution is sheared beyond the critical shear stress (shear-thickening regime) in a stress-controlled experiment, we observe inhomogeneous flow characterized by radial or velocity gradient shear bands with a highly sheared band near the rotor and a weakly sheared band near the stator of the Couette geometry. Furthermore, fast measurements performed in the shear-thickening regime to capture the temporal evolution of local velocities indicate coexistence of both radial and vorticity shear bands. However the same measurements carried out in shear rate controlled mode of the rheometer do not show such rheological complexity.

  3. Theory for modeling the equatorial evening ionosphere and the origin of the shear in the horizontal plasma flow

    SciTech Connect

    Haerendel, G.; Eccles, J.V.; Cakir, S. )

    1992-02-01

    Companion papers in this series present (1) the role of equatorial E region postsunset ionosphere, (2) the origin of horizontal plasma shear flow in the postsunset equatorial ionosphere (this paper), (3) the Colored Bubbles experiments results, and (4) computer simulations of artificial initiation of plasma density depletions (bubbles) in the equatorial ionosphere. Within this paper, equations describing the time evolution of the equatorial ionosphere are developed using flux tube integrated and flux tube weighted quantities which model the chemistry, dynamics, and electrodynamics of the equatorial ionosphere. The resulting two-dimensional set of equations can be used to investigate equatorial ionosphere. The resulting two-dimensional set of equations can be used to investigate equatorial electric fields neglecting small-scale phenomena ({lambda} < 1 km). An immediate result derived from the integrated current equations is an equation describing the physics of the shear in the horizontal flow of the equatorial plasma during the evening hours. The profile of the horizontal flow has three important contributing terms relating to the neutral wind dynamo, Hall conduction, and the equatorial electrojet current divergence. Using a one-dimensional model of the velocity shear equation and the integrated ionosphere transport equations, a time history of the development of the shear feature during postsunset hours is presented. The one-dimensional model results are compared to the velocity shear measurements from the Colored Bubbles experiments.

  4. Piezoelectric wind turbine

    NASA Astrophysics Data System (ADS)

    Kishore, Ravi Anant; Priya, Shashank

    2013-03-01

    In past few years, there has been significant focus towards developing small scale renewable energy based power sources for powering wireless sensor nodes in remote locations such as highways and bridges to conduct continuous health monitoring. These prior efforts have led to the development of micro-scale solar modules, hydrogen fuel cells and various vibration based energy harvesters. However, the cost effectiveness, reliability, and practicality of these solutions remain a concern. Harvesting the wind energy using micro-to-small scale wind turbines can be an excellent solution in variety of outdoor scenarios provided they can operate at few miles per hour of wind speed. The conventional electromagnetic generator used in the wind mills always has some cogging torque which restricts their operation above certain cut-in wind speed. This study aims to develop a novel piezoelectric wind turbine that utilizes bimorph actuators for electro-mechanical energy conversion. This device utilizes a Savonius rotor that is connected to a disk having magnets at the periphery. The piezoelectric actuators arranged circumferentially around the disk also have magnets at the tip which interacts with the magnetic field of the rotating disk and produces cyclical deflection. The wind tunnel experiments were conducted between 2-12 mph of wind speeds to characterize and optimize the power output of the wind turbine. Further, testing was conducted in the open environment to quantify the response to random wind gusts. An attempt was made towards integration of the piezoelectric wind turbine with the wireless sensor node.

  5. Analyzing the Effects of Temporal Wind Patterns on the Value ofWind-Generated Electricity at Different Sites in California and theNorthwest

    SciTech Connect

    Fripp, Matthias; Wiser, Ryan

    2006-05-31

    Wind power production varies on a diurnal and seasonal basis. In this report, we use wind speed data modeled by TrueWind Solutions, LLC (now AWS Truewind) to assess the effects of wind timing on the value of electric power from potential wind farm locations in California and the Northwest. (Data from this dataset are referred to as ''TrueWind data'' throughout this report.) The intra-annual wind speed variations reported in the TrueWind datasets have not previously been used in published work, however, so we also compare them to a collection of anemometer wind speed measurements and to a limited set of actual wind farm production data. The research reported in this paper seeks to answer three specific questions: (1) How large of an effect can the temporal variation of wind power have on the value of wind in different wind resource areas? (2) Which locations are affected most positively or negatively by the seasonal and diurnal timing of wind speeds? (3) How compatible are wind resources in the Northwest and California with wholesale power prices and loads in either region? The latter question is motivated by the fact that wind power projects in the Northwest could sell their output into California (and vice versa), and that California has an aggressive renewable energy policy that may ultimately yield such imports. Based on our research, we reach three key conclusions. (1) Temporal patterns have a moderate impact on the wholesale market value of wind power and a larger impact on the capacity factor during peak hours. The best-timed wind power sites have a wholesale market value that is up to 4 percent higher than the average market price, while the worst-timed sites have a market value that is up to 11 percent below the average market price. The best-timed wind sites could produce as much as 30-40 percent more power during peak hours than they do on average during the year, while the worst timed sites may produce 30-60 percent less power during peak hours. (2) Northwestern markets appear to be well served by Northwestern wind and poorly served by California wind; results are less clear for California markets. Both the modeled TrueWind data and the anemometer data indicate that many Northwestern wind sites are reasonably well-matched to the Northwest's historically winter-peaking wholesale electricity prices and loads, while most California sites are poorly matched to these prices and loads. However, the TrueWind data indicate that most California and Northwestern wind sites are poorly matched to California's summer-afternoon-peaking prices and loads, while the anemometer data suggest that many of these same sites are well matched to California's wholesale prices and loads. (3) TrueWind and anemometer data agree about wind speeds in most times and places, but disagree about California's summer afternoon wind speeds: The TrueWind data indicate that wind speeds at sites in California's coastal mountains and some Northwestern locations dip deeply during summer days and stay low through much of the afternoon. In contrast, the anemometer data indicate that winds at these sites begin to rise during the afternoon and are relatively strong when power is needed most. At other times and locations, the two datasets show good agreement. This disagreement may be due in part to time-varying wind shear between the anemometer heights (20-25m) and the TrueWind reference height (50m or 70m), but may also be due to modeling errors or data collection inconsistencies.

  6. Wind tower service lift

    DOEpatents

    Oliphant, David; Quilter, Jared; Andersen, Todd; Conroy, Thomas

    2011-09-13

    An apparatus used for maintaining a wind tower structure wherein the wind tower structure may have a plurality of legs and may be configured to support a wind turbine above the ground in a better position to interface with winds. The lift structure may be configured for carrying objects and have a guide system and drive system for mechanically communicating with a primary cable, rail or other first elongate member attached to the wind tower structure. The drive system and guide system may transmit forces that move the lift relative to the cable and thereby relative to the wind tower structure. A control interface may be included for controlling the amount and direction of the power into the guide system and drive system thereby causing the guide system and drive system to move the lift relative to said first elongate member such that said lift moves relative to said wind tower structure.

  7. Wind energy conversion system

    DOEpatents

    Longrigg, Paul (Golden, CO)

    1987-01-01

    The wind energy conversion system includes a wind machine having a propeller connected to a generator of electric power, the propeller rotating the generator in response to force of an incident wind. The generator converts the power of the wind to electric power for use by an electric load. Circuitry for varying the duty factor of the generator output power is connected between the generator and the load to thereby alter a loading of the generator and the propeller by the electric load. Wind speed is sensed electro-optically to provide data of wind speed upwind of the propeller, to thereby permit tip speed ratio circuitry to operate the power control circuitry and thereby optimize the tip speed ratio by varying the loading of the propeller. Accordingly, the efficiency of the wind energy conversion system is maximized.

  8. Bifurcation and stability in a model of moist convection in a shearing environment

    NASA Technical Reports Server (NTRS)

    Shirer, H. N.

    1980-01-01

    The truncated spectral system (model I) of shallow moist two-dimensional convection discussed by Shirer and Dutton (1979) is expanded to eleven coefficients (model II) in order to include a basic wind. Cloud streets, the atmospheric analog of the solutions to model II, are typically observed in an environment containing a shearing basic motion field. Analysis of the branching behavior of solutions to mode II shows that, if the basic wind direction varies with height, very complex temporal behavior is possible as the modified Rayleigh number HR is increased sufficiently. The first convective solution is periodic, corresponding to a cloud band that propagates downwind; but secondary branching to a two-dimensional torus can occur for larger values of HR. Orientation band formulas are derived whose predictions generally agree with the results of previous studies.

  9. A Numerical Study of Hurricane Erin (2001). Part II; Shear and the Organization of Eyewall Vertical Motion

    NASA Technical Reports Server (NTRS)

    Braun, Scott A.; Wu, Liguang

    2006-01-01

    A high-resolution numerical simulation of Hurricane Erin (2001) is used to examine the organization of vertical motion in the eyewall and how that organization responds to a large and rapid increase in the environmental vertical wind shear and subsequent decrease in shear. During the early intensification period, prior to the onset of significant shear, the upward motion in the eyewall was concentrated in small-scale convective updrafts that formed in association with regions of concentrated vorticity (herein termed mesovortices) with no preferred formation region in the eyewall. Asymmetric flow within the eye was weak. As the shear increased, an azimuthal wavenumber 1 asymmetry in storm structure developed with updrafts tending to form on the downshear to downshear-left side of the eyewall. Continued intensification of the shear led to increasing wavenumber 1 asymmetry, large vortex tilt, and a change in eyewall structure and vertical motion organization. During this time, the eyewall structure was dominated by a vortex couplet with a cyclonic (anticyclonic) vortex on the downtilt-left (downtilt-right) side of the eyewall and strong asymmetric flow across the eye that led to strong mixing of eyewall vorticity into the eye. Upward motion was concentrated over an azimuthally broader region on the downtilt side of the eyewall, upstream of the cyclonic vortex, where low-level environmental inflow converged with the asymmetric outflow from the eye. As the shear diminished, the vortex tilt and wavenumber 1 asymmetry decreased, while the organization of updrafts trended back toward that seen during the weak shear period.

  10. Peak Wind Tool for General Forecasting

    NASA Technical Reports Server (NTRS)

    Barrett, Joe H., III

    2010-01-01

    The expected peak wind speed of the day is an important forecast element in the 45th Weather Squadron's (45 WS) daily 24-Hour and Weekly Planning Forecasts. The forecasts are used for ground and space launch operations at the Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS). The 45 WS also issues wind advisories for KSC/CCAFS when they expect wind gusts to meet or exceed 25 kt, 35 kt and 50 kt thresholds at any level from the surface to 300 ft. The 45 WS forecasters have indicated peak wind speeds are challenging to forecast, particularly in the cool season months of October - April. In Phase I of this task, the Applied Meteorology Unit (AMU) developed a tool to help the 45 WS forecast non-convective winds at KSC/CCAFS for the 24-hour period of 0800 to 0800 local time. The tool was delivered as a Microsoft Excel graphical user interface (GUI). The GUI displayed the forecast of peak wind speed, 5-minute average wind speed at the time of the peak wind, timing of the peak wind and probability the peak speed would meet or exceed 25 kt, 35 kt and 50 kt. For the current task (Phase II ), the 45 WS requested additional observations be used for the creation of the forecast equations by expanding the period of record (POR). Additional parameters were evaluated as predictors, including wind speeds between 500 ft and 3000 ft, static stability classification, Bulk Richardson Number, mixing depth, vertical wind shear, temperature inversion strength and depth and wind direction. Using a verification data set, the AMU compared the performance of the Phase I and II prediction methods. Just as in Phase I, the tool was delivered as a Microsoft Excel GUI. The 45 WS requested the tool also be available in the Meteorological Interactive Data Display System (MIDDS). The AMU first expanded the POR by two years by adding tower observations, surface observations and CCAFS (XMR) soundings for the cool season months of March 2007 to April 2009. The POR was expanded again by six years, from October 1996 to April 2002, by interpolating 1000-ft sounding data to 100-ft increments. The Phase II developmental data set included observations for the cool season months of October 1996 to February 2007. The AMU calculated 68 candidate predictors from the XMR soundings, to include 19 stability parameters, 48 wind speed parameters and one wind shear parameter. Each day in the data set was stratified by synoptic weather pattern, low-level wind direction, precipitation and Richardson Number, for a total of 60 stratification methods. Linear regression equations, using the 68 predictors and 60 stratification methods, were created for the tool's three forecast parameters: the highest peak wind speed of the day (PWSD), 5-minute average speed at the same time (A WSD), and timing of the PWSD. For PWSD and A WSD, 30 Phase II methods were selected for evaluation in the verification data set. For timing of the PWSD, 12 Phase\\I methods were selected for evaluation. The verification data set contained observations for the cool season months of March 2007 to April 2009. The data set was used to compare the Phase I and II forecast methods to climatology, model forecast winds and wind advisories issued by the 45 WS. The model forecast winds were derived from the 0000 and 1200 UTC runs of the 12-km North American Mesoscale (MesoNAM) model. The forecast methods that performed the best in the verification data set were selected for the Phase II version of the tool. For PWSD and A WSD, linear regression equations based on MesoNAM forecasts performed significantly better than the Phase I and II methods. For timing of the PWSD, none of the methods performed significantly bener than climatology. The AMU then developed the Microsoft Excel and MIDDS GUls. The GUIs display the forecasts for PWSD, AWSD and the probability the PWSD will meet or exceed 25 kt, 35 kt and 50 kt. Since none of the prediction methods for timing of the PWSD performed significantly better thanlimatology, the tool no longer displays this predictand. The Excel and MIDDS GUIs display forecas

  11. Dynamic Modes of Red Blood Cells in Oscillatory Shear Flow

    E-print Network

    Hiroshi Noguchi

    2010-06-12

    The dynamics of red blood cells (RBCs) in oscillatory shear flow was studied using differential equations of three variables: a shape parameter, the inclination angle $\\theta$, and phase angle $\\phi$ of the membrane rotation. In steady shear flow, three types of dynamics occur depending on the shear rate and viscosity ratio. i) tank-treading (TT): $\\phi$ rotates while the shape and $\\theta$ oscillate. ii) tumbling (TB): $\\theta$ rotates while the shape and $\\phi$ oscillate. iii) intermediate motion: both $\\phi$ and $\\theta$ rotate synchronously or intermittently. In oscillatory shear flow, RBCs show various dynamics based on these three motions. For a low shear frequency with zero mean shear rate, a limit-cycle oscillation occurs, based on the TT or TB rotation at a high or low shear amplitude, respectively. This TT-based oscillation well explains recent experiments. In the middle shear amplitude, RBCs show an intermittent or synchronized oscillation. As shear frequency increases, the vesicle oscillation becomes delayed with respect to the shear oscillation. At a high frequency, multiple limit-cycle oscillations coexist. For a high mean shear rate with small shear oscillation, the shape and $\\theta$ oscillate in the TT motion but only one attractor exists even at high shear frequencies. The measurement of these oscillatory modes is a promising tool for quantifying the viscoelasticity of RBCs and synthetic capsules.

  12. Theory of activated-rate processes under shear with application to shear-induced aggregation of colloids

    E-print Network

    Alessio Zaccone; Daniele Gentili; Hua Wu; Massimo Morbidelli

    2010-02-24

    Using a novel approximation scheme within the convective diffusion (two body Smoluchowski) equation framework, we unveil the shear-driven aggregation mechanism at the origin of structure-formation in sheared colloidal systems. The theory, verified against numerics and experiments, explains the induction time followed by explosive (irreversible) rise of viscosity observed in charge-stabilized colloidal and protein systems under steady shear. The Arrhenius-type equation with shear derived here, extending Kramers theory in the presence of shear, is the first analytical result clearly showing the important role of shear-drive in activated-rate processes as they are encountered in soft condensed matter.

  13. Structural changes in the currents and fields of the equatorial electrojet due to zonal and meridional winds

    SciTech Connect

    Anandarao, B.G.; Raghavarao, R. )

    1987-03-01

    The authors describe calculations of the effects of zonal and meridional winds on the equatorial electrojet vis-a-vis the observed features by solving the electrodynamic equations. Vertical shears in the zonal winds can cause significant changes in the electrojet beyond about 2{degree} latitude. At the magnetic equator these changes are less than about 10%. The width (latitudinal) and the thickness (altitudinal) of the jet are changed by as much as 100% by these shears. When the width is decreased, the intensity of the current densities in meridional plane is increased. Steady (not varying with altitude) zonal winds are ineffective. These results are discussed in comparison with those of earlier authors. Meridional winds cause substantial cross-equatorial currents leading to considerable asymmetry in the distribution of the electrojet current density as inferred by the ground-base and rocket-borne magnetometers. The electrojet center is shifted to about 0.5{degree} south of the equator by a steady northward wind of speed 100 m/s. The deviations in the magnitude of the electrojet current produced by the meridional winds are significant only beyond {plus minus}2{degree} off the equator. Structures in the vertical profiles of the eastward current density observed by rocket-borne magnetometers a few degrees off the equator can be accounted for by the zonal wind shears.

  14. Yaw dynamics of a horizontal axis wind turbine

    NASA Astrophysics Data System (ADS)

    Kirchhoff, R.; Cromack, D.; Cohen, R.

    The dynamics of horizontal axis wind turbine response in yaw are analyzed. A model is explored consisting of an ellipsoidal nacelle, a rigid pole, no wind shear, and zero coning in the rotor blades. The torque applied to the nacelle and the rotor blades, due to gyroscopic, Coriolis, and damping forces are considered linearly. A coordinate system for the moment of inertia and the angular acceleration is devised, and the pressures on each blade (3 blades in the study) are integrated. The possibility of a coupling between the wind speed and the lowest natural frequency is suggested, and experiments with a non-rigid tower are indicated to examine a configuration where Coriolis forces may dominate.

  15. Aeroacoustics of subsonic turbulent shear flows

    NASA Technical Reports Server (NTRS)

    Goldstein, Marvin E.

    1987-01-01

    Sound generation in turbulent shear flows is examined. The emphasis is on simultaneous calculation of the turbulent flow along with the resulting sound generation rather than the alternative acoustic analogy approach. The first part of the paper is concerned with solid surface interaction. The second part concentrates on the sound generated by turbulence interacting with itself.

  16. Hydrodynamic Modeling and the QGP Shear Viscosity

    E-print Network

    Huichao Song

    2012-07-10

    In this article, we will briefly review the recent progress on hydrodynamic modeling and the extraction of the quark-gluon plasma (QGP) specific shear viscosity with an emphasis on results obtained from the hybrid model VISHNU that couples viscous hydrodynamics for the macroscopic expansion of the QGP to the hadron cascade model for the microscopic evolution of the late hadronic stage.

  17. Shear viscosity of a nonperturbative gluon plasma

    E-print Network

    Dmitri Antonov

    2012-02-10

    Shear viscosity is evaluated within a model of the gluon plasma, which is based entirely on the stochastic nonperturbative fields. We consider two types of excitations of such fields, which are characterized by the thermal correlation lengths ~ 1/(g^2 T) and ~ 1/(g^4 T), where "g" is the finite-temperature Yang-Mills coupling. Excitations of the first type correspond to the genuine nonperturbative stochastic Yang-Mills fields, while excitations of the second type mimic the known result for the shear viscosity of the perturbative Yang-Mills plasma. We show that the excitations of the first type produce only an O(g^{10})-correction to this result. Furthermore, a possible interference between excitations of these two types yields a somewhat larger, O(g^7), correction to the leading perturbative Yang-Mills result. Our analysis is based on the Fourier transformed Euclidean Kubo formula, which represents an integral equation for the shear spectral density. This equation is solved by seeking the spectral density in the form of the Lorentzian Ans\\"atze, whose widths are defined by the two thermal correlation lengths and by their mean value, which corresponds to the said interference between the two types of excitations. Thus, within one and the same formalism, we reproduce the known result for the shear viscosity of the perturbative Yang-Mills plasma, and account for possible nonperturbative corrections to it.

  18. THE SHEARING BEHAVIOUR OF A SUGAR AGGREGATE

    E-print Network

    Bolton, Malcolm

    of sugar crystals from molasses in several steps. Although continuous centrifuges have recently beenTHE SHEARING BEHAVIOUR OF A SUGAR AGGREGATE Catherine A. Davy1 , M. D. Bolton2 , N. A. Fleck2, UK #12;Abstract To better understand the behaviour of sugar within industrial centrifuges or silos

  19. Vane shear test for cohesionless soils

    NASA Astrophysics Data System (ADS)

    Park, Sung-Sik; An, Zhou; Ye, Sung-Ryol; Lee, Sae-Byeok; Chae, Kyung-Hyeon

    2015-04-01

    The vane shear test (VST) is a simple and rapid testing method for determining the undrained shear strength of cohesive soils. It has not been applied for granular soils because the failure surface was irregular and hardly determined due to their cohesionless property. In this study, the VST was used to determine the shear strength of cohesionless soils such as sand. A small laboratory vane with 5 cm in diameter and 10 cm in height was inserted into sand within pressurized cell. When the vane rotates within sand, a failure surface can be assumed to be cylindrical shape because the sand is pressurized with loading frame. Dry Nakdong River sand was prepared for loose and dense conditions in the cell and the axial pressure of 50, 100, and 200 kPa was applied on the surface of sand. The relationship between measured torque and resistant force along cylindrical shape due to friction of sand was derived and the internal friction angle of sand was determined for loose and dense conditions. It was possible for the VST to determine the shear strength of sand under confined condition.

  20. BOUNDARY SHEAR STRESS ALONG VEGETATED STREAMBANKS

    EPA Science Inventory

    This research is intended to improve our understanding of the role of riparian vegetation in stream morphology by evaluating the effects of vegetation on boundary shear stress, providing insight to the type and density of vegetation required for streambank stability. The resu...