Recent development of a jet-diffuser ejector

NASA Technical Reports Server (NTRS)

Alperin, M.; Wu, J. J.

1980-01-01

The paper considers thrust augmenting ejectors in which the processes of mixing and diffusion are partly carried out downstream of the ejector solid surfaces. A jet sheet surrounding the periphery of a widely diverging diffuser prevents separation and forms a gaseous, curved surface to provide effective diffuser ratio and additional length for mixing of primary and induced flows. Three-dimensional potential flow methods achieved a large reduction in the length of the associated solid surface; primary nozzle design further reduced the volume required by the jet-diffuser ejectors, resulting in thrust augmentation in excess of two, and an overall length of about 2 1/2 times the throat width.

Wind-Tunnel Modeling of Flow Diffusion over an Urban Complex.

DTIC Science & Technology

URBAN AREAS, *ATMOSPHERIC MOTION, *AIR POLLUTION, ATMOSPHERIC MOTION, WIND TUNNEL MODELS, HEAT, DIFFUSION , TURBULENT BOUNDARY LAYER, WIND, SKIN FRICTION, MATHEMATICAL MODELS, URBAN PLANNING, INDIANA.

Climatological observations and predicted sublimation rates at Lake Hoare, Antarctica.

USGS Publications Warehouse

Clow, G.D.; McKay, C.P.; Simmons, G.M.; Wharton, R.A.

1988-01-01

In December 1985, an automated meteorological station was established at Lake Hoare in the dry valley region of Antarctica. Here, we report on the first year-round observations available for any site in Taylor Valley. This dataset augments the year-round data obtained at Lake Vanda (Wright Valley) by winter-over crews during the late 1960s and early 1970s. The mean annual solar flux at Lake Hoare was 92 W m-2 during 1986, the mean air temperature -17.3 degrees C, and the mean 3-m wind speed 3.3 m s-1. The local climate is controlled by the wind regime during the 4-month sunless winter and by seasonal and diurnal variations in the incident solar flux during the remainder of the year. Temperature increases of 20 degrees-30 degrees C are frequently observed during the winter due to strong fo??hn winds descending from the Polar Plateau. A model incorporating nonsteady molecular diffusion into Kolmogorov-scale eddies in the interfacial layer and similarity-theory flux-profiles in the surface sublayer, is used to determine the rate of ice sublimation from the acquired meteorological data. Despite the frequent occurrence of strong winter fo??hns, the bulk of the annual ablation occurs during the summer due to elevated temperatures and persistent moderate winds. The annual ablation from Lake Hoare is estimated to have been 35.0 +/- 6.3 cm for 1986.

Effect of hemoglobin polymerization on oxygen transport in hemoglobin solutions.

PubMed

Budhiraja, Vikas; Hellums, J David

2002-09-01

The effect of hemoglobin (Hb) polymerization on facilitated transport of oxygen in a bovine hemoglobin-based oxygen carrier was studied using a diffusion cell. In high oxygen tension gradient experiments (HOTG) at 37 degrees C the diffusion of dissolved oxygen in polymerized Hb samples was similar to that in unpolymerized Hb solutions during oxygen uptake. However, in the oxygen release experiments, the transport by diffusion of dissolved oxygen was augmented by diffusion of oxyhemoglobin over a range of oxygen saturations. The augmentation was up to 30% in the case of polymerized Hb and up to 100% in the case of unpolymerized Hb solution. In experiments performed at constant, low oxygen tension gradients in the range of physiological significance, the augmentation effect was less than that in the HOTG experiments. Oxygen transport in polymerized Hb samples was approximately the same as that in unpolymerized samples over a wide range of oxygen tensions. However, at oxygen tensions lower than 30 mm Hg, there were more significant augmentation effects in unpolymerized bovine Hb samples than in polymerized Hb. The results presented here are the first accurate, quantitative measurements of effective diffusion coefficients for oxygen transport in hemoglobin-based oxygen carriers of the type being evaluated to replace red cells in transfusions. In all cases the oxygen carrier was found to have higher effective oxygen diffusion coefficients than blood.

Status of Sundstrand research

NASA Technical Reports Server (NTRS)

Bateman, Don

1991-01-01

Wind shear detection status is presented in the form of view-graphs. The following subject areas are covered: second generation detection (Q-bias, gamma bias, temperature biases, maneuvering flight modulation, and altitude modulation); third generation wind shear detection (use wind shear computation to augment flight path and terrain alerts, modulation of alert thresholds based on wind/terrain data base, incorporate wind shear/terrain alert enhancements from predictive sensor data); and future research and development.

ANALYTICAL SOLUTIONS OF THE ATMOSPHERIC DIFFUSION EQUATION WITH MULTIPLE SOURCES AND HEIGHT-DEPENDENT WIND SPEED AND EDDY DIFFUSIVITIES. (R825689C072)

EPA Science Inventory

Abstract

Three-dimensional analytical solutions of the atmospheric diffusion equation with multiple sources and height-dependent wind speed and eddy diffusivities are derived in a systematic fashion. For homogeneous Neumann (total reflection), Dirichlet (total adsorpti...

ANALYTICAL SOLUTIONS OF THE ATMOSPHERIC DIFFUSION EQUATION WITH MULTIPLE SOURCES AND HEIGHT-DEPENDENT WIND SPEED AND EDDY DIFFUSIVITIES. (R825689C048)

EPA Science Inventory

Abstract

Three-dimensional analytical solutions of the atmospheric diffusion equation with multiple sources and height-dependent wind speed and eddy diffusivities are derived in a systematic fashion. For homogeneous Neumann (total reflection), Dirichlet (total adsorpti...

Diurnal forcing of planetary atmospheres

NASA Technical Reports Server (NTRS)

Houben, Howard C.

1991-01-01

A free convection parameterization has been introduced into the Mars Planetary Boundary Layer Model (MPBL). Previously, the model would fail to generate turbulence under conditions of zero wind shear, even when statically unstable. This in turn resulted in erroneous results at the equator, for example, when the lack of Coriolis forcing allowed zero wind conditions. The underlying cause of these failures was the level 2 second-order turbulence closure scheme which derived diffusivities as algebraic functions of the Richardson number (the ratio of static stability to wind shear). In the previous formulation, the diffusivities were scaled by the wind shear--a convenient parameter since it is non-negative. This was the drawback that all diffusivities are zero under conditions of zero shear (viz., the free convection case). The new scheme tests for the condition of zero shear in conjunction with static instability and recalculates the diffusivities using a static stability scaling. The results for a simulation of the equatorial boundary layer at autumnal equinox are presented. (Note that after some wind shear is generated, the model reverts to the traditional diffusivity calculation.)

Advanced wind turbine design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jamieson, P.M.; Jaffrey, A.

1995-09-01

Garrad Hassan have a project in progress funded by the UK Department of Trade and Industry (DTI) to assess the prospects and cost benefits of advanced wind turbine design. In the course of this work, a new concept, the coned rotor design, has been developed. This enables a wind turbine system to operate in effect with variable rotor diameter augmenting energy capture in light winds and shedding loads in storm conditions. Comparisons with conventional design suggest that a major benefit in reduced cost of wind generated electricity may be possible.

Advanced wind turbine design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jamieson, P.M.; Jaffrey, A.

1997-11-01

Garrad Hassan have a project in progress funded by the U.K. Department of Trade and Industry (DTI) to assess the prospects and cost benefits of advanced wind turbine design. In the course of this work, a new concept, the coned rotor design, has been developed. This enables a wind turbine system to operate in effect with variable rotor diameter augmenting energy capture in light winds and shedding loads in storm conditions. Comparisons with conventional design suggest that a major benefit in reduced cost of wind-generated electricity may be possible.

Motion immune diffusion imaging using augmented MUSE (AMUSE) for high-resolution multi-shot EPI

PubMed Central

Guhaniyogi, Shayan; Chu, Mei-Lan; Chang, Hing-Chiu; Song, Allen W.; Chen, Nan-kuei

2015-01-01

Purpose To develop new techniques for reducing the effects of microscopic and macroscopic patient motion in diffusion imaging acquired with high-resolution multi-shot EPI. Theory The previously reported Multiplexed Sensitivity Encoding (MUSE) algorithm is extended to account for macroscopic pixel misregistrations as well as motion-induced phase errors in a technique called Augmented MUSE (AMUSE). Furthermore, to obtain more accurate quantitative DTI measures in the presence of subject motion, we also account for the altered diffusion encoding among shots arising from macroscopic motion. Methods MUSE and AMUSE were evaluated on simulated and in vivo motion-corrupted multi-shot diffusion data. Evaluations were made both on the resulting imaging quality and estimated diffusion tensor metrics. Results AMUSE was found to reduce image blurring resulting from macroscopic subject motion compared to MUSE, but yielded inaccurate tensor estimations when neglecting the altered diffusion encoding. Including the altered diffusion encoding in AMUSE produced better estimations of diffusion tensors. Conclusion The use of AMUSE allows for improved image quality and diffusion tensor accuracy in the presence of macroscopic subject motion during multi-shot diffusion imaging. These techniques should facilitate future high-resolution diffusion imaging. PMID:25762216

Direct monitoring of wind-induced pressure-pumping on gas transport in soil

NASA Astrophysics Data System (ADS)

Laemmel, Thomas; Mohr, Manuel; Schindler, Dirk; Schack-Kirchner, Helmer; Maier, Martin

2017-04-01

Gas exchange between soil and atmosphere is important for the biogeochemistry of soils and is commonly assumed to be governed by molecular diffusion. Yet a few previous field studies identified other gas transport processes such as wind-induced pressure-pumping to enhance soil-atmosphere fluxes significantly. However, since these wind-induced non-diffusive gas transport processes in soil often occur intermittently, the quantification of their contribution to soil gas emissions is challenging. To quantify the effects of wind-induced pressure-pumping on soil gas transport, we developed a method for in situ monitoring of soil gas transport. The method includes the use of Helium (He) as a tracer gas which was continuously injected into the soil. The resulting He steady-state concentration profile was monitored. Gas transport parameters of the soil were inversely modelled. We used our method during a field campaign in a well-aerated forest soil over three months. During periods of low wind speed, soil gas transport was modelled assuming diffusion as transport process. During periods of high wind speed, the previously steady diffusive He concentration profile showed temporary concentration decreases in the topsoil, indicating an increase of the effective gas transport rate in the topsoil up to 30%. The enhancement of effective topsoil soil gas diffusivity resulted from wind-induced air pressure fluctuations which are referred to as pressure-pumping. These air pressure fluctuations had frequencies between 0.1 and 0.01 Hz and amplitudes up to 10 Pa and occurred at above-canopy wind speeds greater than 5 m s-1. We could show the importance of the enhancement of the gas transport rate in relation with the wind intensity and corresponding air pressure fluctuations characteristics. We directly detected and quantified the pressure-pumping effect on gas transport in soil in a field study for the first time, and could thus validate and underpin the importance of this non-diffusive gas transport process. Our method can also be used to study other non-diffusive gas transport processes occurring in soil and snow, and their possible feedbacks or interactions with biogeochemical processes.

Experimental and Computational Investigations of Vertical Axis Wind Turbine Enclosed with Flanged Diffuser

NASA Astrophysics Data System (ADS)

Surya Raj, G.; Sangeetha, N.; Prince, M.

2018-02-01

Generation of wind energy is a must to meet out additional demand. To meet out the additional demand several long term plans were considered now being taken up for generation of energy for the fast developing industries. Detailed researches were since taken up to improve the efficiency of such vertical axis wind turbine (VAWT). In this work VAWT with diffuser and without diffuser arrangement are considered for experimental and analysis. Five diffusers were since provided around its blades of VAWT which will be placed inside a pentagon shaped fabricated structure. In this power output of the diffuser based VAWT arrangement were studied in both numerical and experimental methods and related with that of a bared VAWT. Finally, it was found that the output power of diffuser based VAWT generates approximately two times than that of bared VAWT.

LNG vapor barrier and obstacle evaluation: Wind-tunnel simulation of 1987 Falcon Spill Series. Final report, July 1987-February 1991

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, S.H.; Meroney, R.N.; Neff, D.E.

1991-03-01

Measurements of the behavior of simulated liquefied natural gas clouds dispersing over small-scale model placed in environmental wind tunnels permits evaluations of the fluid physics of dense cloud movement and dispersion in a controlled environment. A large data base on the interaction of simulated LNG plumes with the Falcon test configuration of vapor barrier fences and vortex generators was obtained. The purpose of the reported test program is to provide post-field-spill wind tunnel experiments to augment the LNG Vapor Fence Field Program data obtained during the Falcon Test Series in 1987. The goal of the program is to determine themore » probable response of a dense LNG Vapor cloud to vortex inducer obstacles and fences, examine the sensitivity of results to various scaling arguments which might augment limit, or extend the value of the field and wind-tunnel tests, and identify important details of the spill behavior which were not predicted during the pretest planning phase.« less

Comparison of QuikSCAT and GPS-Derived Ocean Surface Winds

NASA Technical Reports Server (NTRS)

Axelrad, Penina

2001-01-01

The Colorado Center for Astrodynamics has completed a study comparing ocean surface winds derived from GPS bistatic measurements with QuikSCAT wind fields. We have also compiled an extensive database of the bistatic GPS flight data collected by NASA Langley Research Center over the last several years. The GPS data are augmented with coincident data from QuikSCAT, buoys, TOPEX, and ERS.

Towards a theory of stochastic vorticity-augmentation. [tornado model

NASA Technical Reports Server (NTRS)

Liu, V. C.

1977-01-01

A new hypothesis to account for the formation of tornadoes is presented. An elementary one-dimensional theory is formulated for vorticity transfer between an ambient sheared wind and a transverse penetrating jet. The theory points out the relevant quantities to be determined in describing the present stochastic mode of vorticity augmentation.

Feasibility of Using an Augmented Immersive Virtual Reality Learning Environment to Enhance Music Conducting Skills

ERIC Educational Resources Information Center

Orman, Evelyn K.; Price, Harry E.; Russell, Christine R.

2017-01-01

Acquiring nonverbal skills necessary to appropriately communicate and educate members of performing ensembles is essential for wind band conductors. Virtual reality learning environments (VRLEs) provide a unique setting for developing these proficiencies. For this feasibility study, we used an augmented immersive VRLE to enhance eye contact, torso…

Suspended sediment diffusion mechanisms in the Yangtze Estuary influenced by wind fields

NASA Astrophysics Data System (ADS)

Wang, Lihua; Zhou, Yunxuan; Shen, Fang

2018-01-01

The complexity of suspended sediment concentration (SSC) distribution and diffusion has been widely recognized because it is influenced by sediment supply and various hydrodynamic forcing conditions that vary over space and over time. Sediment suspended by waves and transported by currents are the dominant sediment transport mechanisms in estuarine and coastal areas. However, it is unclear to what extent the SSC distribution is impacted by each hydrodynamic factor. Research on the quantitative influence of wind fields on the SSC diffusion range will contribute to a better understanding of the characteristics of sediment transport change and sedimentary geomorphic evolution. This study determined SSC from three Envisat Medium-Resolution Imaging Spectrometer acquisitions, covering the Yangtze Estuary and adjacent water area under the same season and tidal conditions but with varying wind conditions. SSC was examined based on the Semi-Empirical Radiative Transfer model, which has been well validated with the observation data. Integrating the corresponding wind field information from European Centre for Medium-Range Weather Forecasts further facilitated the discussion of wind fields affecting SSC, and in turn the influence of water and suspended sediment transportation and diffusion in the Yangtze estuarine and coastal area. The results demonstrated that the SSC present much more distinctive fluvial features in the inner estuary and wind fields are one of the major factors controlling the range of turbid water diffusion.

Persistent wind-induced enhancement of diffusive CO2 transport in a mountain forest snowpack

Treesearch

D. R. Bowling; W. J. Massman

2011-01-01

Diffusion dominates the transport of trace gases between soil and the atmosphere. Pressure gradients induced by atmospheric flow and wind interacting with topographical features cause a small but persistent bulk flow of air within soil or snow. This forcing, called pressure pumping or wind pumping, leads to a poorly quantified enhancement of gas transport beyond the...

Simulating 3D Stellar Winds and Diffuse X-ray Emissions from Gases in Non-equilibrium Ionization State

NASA Astrophysics Data System (ADS)

Long, Min; Sun, Wei; Niu, Shu; Zhou, Xin; Ji, Li

2017-08-01

We investigate the physical properties of stellar winds launched in super stellar clusters (SSCs). Chandra observations have detected the presence of diffuse X-ray emission caused by hot gas from such winds in SSCs, and provide the best probe for understanding interactions between the stellar winds and the complex nursery regions. However, the details of the origin of cluster winds, the mass and energy ejection, the formation of diffuse X-ray emission, the fraction of winds contribution to the distribution of diffuse X-ray emission still remain unclear. We developed a multiphysics hydrodynamic model including self-gravity, head conduction and performed 3D simulations with an unprecedented grid resolution due to adaptive mesh refinement (AMR) capability in a case study of NGC 3603, as a supplement to the analysis of the archived 500 ks Chandra observations. The synthetic emission will be computed by assuming the gas in a non-equilibrium ionization (NEI) state indicated by Chandra observation, not coronal ionization equilibrium (CIE) that most works assumed, by using a customized NEI calculation module based on AtomDB. The results will be compared to the Chandra observations.

An overview of current Navy programs to develop thrust augmenting ejectors

NASA Technical Reports Server (NTRS)

Green, K. A.

1979-01-01

The primary objective of Navy sponsored research in thrust augmentation is the development of an improved augmenter for V/STOL application. In support of this goal, a data base is being established to provide an accurate prediction capability for use in ejector design. A general technology development of ejectors and associated effects presently is split into the more specific areas of lift and control, since thrust augmenting ejectors may be suitable for both. Research areas examined include advanced diffuser and end wall design; advanced primary nozzles; analytic studies; augmenting reaction controls; and nozzle design.

Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH). Part 1

NASA Technical Reports Server (NTRS)

Micheletti, David A.; Baughman, Jack A.; Nelson, Gordon L.; Simmons, Gloyd A.

1997-01-01

This report documents the activities, results, conclusions and recommendations of the Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH) Project in which the use of magnetohydrodynamics (MHD) technology is investigated for its applicability to augment hypersonic wind tunnels. The long range objective of this investigation is to advance the development of ground test facilities to support the development of hypervelocity flight vehicles. The MHD accelerator adds kinetic energy directly to the wind tunnel working fluid, thereby increasing its Mach number to hypervelocity levels. Several techniques for MHD augmentation, as well as other physical characteristics of the process are studied to enhance the overall performance of hypersonic wind tunnel design. Specific recommendations are presented to improve the effectiveness of ground test facilities. The work contained herein builds on nearly four decades of research and experimentation by the aeronautics ground test and evaluation community, both foreign and domestic.

Magnetohydrodynamics Accelerator Research into Advanced Hypersonics (MARIAH). Part 2

NASA Technical Reports Server (NTRS)

Baughman, Jack A.; Micheletti, David A.; Nelson, Gordon L.; Simmons, Gloyd A.

1997-01-01

This report documents the activities, results, conclusions and recommendations of the Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH) Project in which the use of magnetohydrodynamics (MHD) technology is investigated for its applicability to augment hypersonic wind tunnels. The long range objective of this investigation is to advance the development of ground test facilities to support the development of hypervelocity flight vehicles. The MHD accelerator adds kinetic energy directly to the wind tunnel working fluid, thereby increasing its Mach number to hypervelocity levels. Several techniques for MHD augmentation, as well as other physical characteristics of the process are studied to enhance the overall performance of hypersonic wind tunnel design. Specific recommendations are presented to improve the effectiveness of ground test facilities. The work contained herein builds on nearly four decades of research and experimentation by the aeronautics ground test and evaluation community, both foreign and domestic.

Separation of Electric Fields Into Potential and Inductive Parts, and Implications for Radial Diffusion

NASA Astrophysics Data System (ADS)

Chan, A. A.; Ilie, R.; Elkington, S. R.; Albert, J.; Huie, W.

2017-12-01

It has been traditional to separate radiation belt radial-diffusion coefficients into two contributions: an "electrostatic" diffusion coefficient, which is assumed to be due to a potential (non-inductive) electric field, and an "electromagnetic" diffusion coefficient , which is assumed to be due to the combined effect of an inductive electric field and the corresponding time-dependent magnetic field. One difficulty in implementing this separation when using magnetospheric fields obtained from measurements, or from MHD simulations, is that only the total electric field is given; the separation of the electric field into potential and inductive parts is not readily available. In this work we separate the electric field using a numerical method based on the Helmholtz decomposition of the total motional electric field calculated by the BATS-R-US MHD code. The inner boundary for the electric potential is based on the Ridley Ionospheric Model solution and we assume floating boundary conditions in the solar wind. Using different idealized solar wind drivers, including a solar wind density that is oscillating at a single frequency or with a broad spectrum of frequencies, we calculate potential and inductive electric fields, electric and magnetic power spectral densities, and corresponding radial diffusion coefficients. Simulations driven by idealized solar wind conditions show a clear separation of the potential and inductive contributions to the power spectral densities and diffusion coefficients. Simulations with more realistic solar wind drivers are underway to better assess the use of electrostatic and electromagnetic diffusion coefficients in understanding ULF wave-particle interactions in Earth's radiation belts.

Magnetic Turbulence, Fast Magnetic Field line Diffusion and Small Magnetic Structures in the Solar Wind

NASA Astrophysics Data System (ADS)

Zimbardo, G.; Pommois, P.; Veltri, P.

2003-09-01

The influence of magnetic turbulence on magnetic field line diffusion has been known since the early days of space and plasma physics. However, the importance of ``stochastic diffusion'' for energetic particles has been challenged on the basis of the fact that sharp gradients of either energetic particles or ion composition are often observed in the solar wind. Here we show that fast transverse field line and particle diffusion can coexist with small magnetic structures, sharp gradients, and with long lived magnetic flux tubes. We show, by means of a numerical realization of three dimensional magnetic turbulence and by use of the concepts of deterministic chaos and turbulent transport, that turbulent diffusion is different from Gaussian diffusion, and that transport can be inhomogeneous even if turbulence homogeneously fills the heliosphere. Several diagnostics of field line transport and flux tube evolution are shown, and the size of small magnetic structures in the solar wind, like gradient scales and flux tube thickness, are estimated and compared to the observations.

Comparison of analytical and experimental performance of a wind-tunnel diffuser section

NASA Technical Reports Server (NTRS)

Shyne, R. J.; Moore, R. D.; Boldman, D. R.

1986-01-01

Wind tunnel diffuser performance is evaluated by comparing experimental data with analytical results predicted by an one-dimensional integration procedure with skin friction coefficient, a two-dimensional interactive boundary layer procedure for analyzing conical diffusers, and a two-dimensional, integral, compressible laminar and turbulent boundary layer code. Pressure, temperature, and velocity data for a 3.25 deg equivalent cone half-angle diffuser (37.3 in., 94.742 cm outlet diameter) was obtained from the one-tenth scale Altitude Wind Tunnel modeling program at the NASA Lewis Research Center. The comparison is performed at Mach numbers of 0.162 (Re = 3.097x19(6)), 0.326 (Re = 6.2737x19(6)), and 0.363 (Re = 7.0129x10(6)). The Reynolds numbers are all based on an inlet diffuser diameter of 32.4 in., 82.296 cm, and reasonable quantitative agreement was obtained between the experimental data and computational codes.

Momentum deposition on Wolf-Rayet winds: Nonisotropic diffusion with effective gray opacity

NASA Technical Reports Server (NTRS)

Gayley, Kenneth G.; Owocki, Stanley P.; Cranmer, Steven R.

1995-01-01

We derive the velocity and mass-loss rate of a steady state Wolf-Rayet (WR) wind, using a nonisotropic diffusion approximation applied to the transfer between strongly overlapping spectral lines. Following the approach of Friend & Castor (1983), the line list is assumed to approximate a statistically parameterized Poisson distribution in frequency, so that photon transport is controlled by an angle-dependent, effectively gray opacity. We show the nonisotropic diffusion approximation yields good agreement with more accurate numerical treatments of the radiative transfer, while providing analytic insight into wind driving by multiple scattering. We illustrate, in particular, that multiple radiative momentum deposition does not require that potons be repeatedly reflected across substantial distances within the spherical envelope, but indeed is greatest when photons undergo a nearly local diffusion, e.g., through scattering by many lines closely spaced in frequency. Our results reiterate the view that the so-called 'momentum problem' of Wolf-Rayet winds is better characterized as an 'opacity problem' of simply identfying enough lines. One way of increasing the number of thick lines in Wolf-Rayet winds is to transfer opacity from saturated to unsaturated lines, yielding a steeper opacity distribution than that found in OB winds. We discuss the implications of this perspective for extending our approach to W-R wind models that incorporate a more fundamental treatment of the ionization and excitation processes that determine the line opacity. In particular, we argue that developing statistical descriptions of the lines to allow an improved effective opacity for the line ensemble would offer several advantages for deriving such more fundamental W-R wind models.

Momentum deposition on Wolf-Rayet winds: Nonisotropic diffusion with effective gray opacity

NASA Astrophysics Data System (ADS)

Gayley, Kenneth G.; Owocki, Stanley P.; Cranmer, Steven R.

1995-03-01

We derive the velocity and mass-loss rate of a steady state Wolf-Rayet (WR) wind, using a nonisotropic diffusion approximation applied to the transfer between strongly overlapping spectral lines. Following the approach of Friend & Castor (1983), the line list is assumed to approximate a statistically parameterized Poisson distribution in frequency, so that photon transport is controlled by an angle-dependent, effectively gray opacity. We show the nonisotropic diffusion approximation yields good agreement with more accurate numerical treatments of the radiative transfer, while providing analytic insight into wind driving by multiple scattering. We illustrate, in particular, that multiple radiative momentum deposition does not require that photons be repeatedly reflected across substantial distances within the spherical envelope, but indeed is greatest when photons undergo a nearly local diffusion, e.g., through scattering by many lines closely spaced in frequency. Our results reiterate the view that the so-called 'momentum problem' of Wolf-Rayet winds is better characterized as an 'opacity problem' of simply identifying enough lines. One way of increasing the number of thick lines in Wolf-Rayet winds is to transfer opacity from saturated to unsaturated lines, yielding a steeper opacity distribution than that found in OB winds. We discuss the implications of this perspective for extending our approach to W-R wind models that incorporate a more fundamental treatment of the ionization and excitation processes that determine the line opacity. In particular, we argue that developing statistical descriptions of the lines to allow an improved effective opacity for the line ensemble would offer several advantages for deriving such more fundamental W-R wind models.

Chaotic gas turbine subject to augmented Lorenz equations.

PubMed

Cho, Kenichiro; Miyano, Takaya; Toriyama, Toshiyuki

2012-09-01

Inspired by the chaotic waterwheel invented by Malkus and Howard about 40 years ago, we have developed a gas turbine that randomly switches the sense of rotation between clockwise and counterclockwise. The nondimensionalized expressions for the equations of motion of our turbine are represented as a starlike network of many Lorenz subsystems sharing the angular velocity of the turbine rotor as the central node, referred to as augmented Lorenz equations. We show qualitative similarities between the statistical properties of the angular velocity of the turbine rotor and the velocity field of large-scale wind in turbulent Rayleigh-Bénard convection reported by Sreenivasan et al. [Phys. Rev. E 65, 056306 (2002)]. Our equations of motion achieve the random reversal of the turbine rotor through the stochastic resonance of the angular velocity in a double-well potential and the force applied by rapidly oscillating fields. These results suggest that the augmented Lorenz model is applicable as a dynamical model for the random reversal of turbulent large-scale wind through cessation.

SIMULATION OF WIND FIELDS OVER POINT ARGUELLO, CALIFORNIA, BY WIND-TUNNEL FLOW OVER A TOPOGRAPHIC MODEL.

DTIC Science & Technology

decay rates for diffusing tracers. The data revealed that a laminar laboratory flow may be used to simulate a turbulent field flow under conditions of...stable thermal stratification and complex terrain. In such flow conditions, diffusion is dominated by convective dispersion. (Author)

A control-volume method for analysis of unsteady thrust augmenting ejector flows

NASA Technical Reports Server (NTRS)

Drummond, Colin K.

1988-01-01

A method for predicting transient thrust augmenting ejector characteristics is presented. The analysis blends classic self-similar turbulent jet descriptions with a control volume mixing region discretization to solicit transient effects in a new way. Division of the ejector into an inlet, diffuser, and mixing region corresponds with the assumption of viscous-dominated phenomenon in the latter. Inlet and diffuser analyses are simplified by a quasi-steady analysis, justified by the assumptions that pressure is the forcing function in those regions. Details of the theoretical foundation, the solution algorithm, and sample calculations are given.

Influence of Wind Pressure on the Carbonation of Concrete

PubMed Central

Zou, Dujian; Liu, Tiejun; Du, Chengcheng; Teng, Jun

2015-01-01

Carbonation is one of the major deteriorations that accelerate steel corrosion in reinforced concrete structures. Many mathematical/numerical models of the carbonation process, primarily diffusion-reaction models, have been established to predict the carbonation depth. However, the mass transfer of carbon dioxide in porous concrete includes molecular diffusion and convection mass transfer. In particular, the convection mass transfer induced by pressure difference is called penetration mass transfer. This paper presents the influence of penetration mass transfer on the carbonation. A penetration-reaction carbonation model was constructed and validated by accelerated test results under high pressure. Then the characteristics of wind pressure on the carbonation were investigated through finite element analysis considering steady and fluctuating wind flows. The results indicate that the wind pressure on the surface of concrete buildings results in deeper carbonation depth than that just considering the diffusion of carbon dioxide. In addition, the influence of wind pressure on carbonation tends to increase significantly with carbonation depth. PMID:28793462

Influence of Wind Pressure on the Carbonation of Concrete.

PubMed

Zou, Dujian; Liu, Tiejun; Du, Chengcheng; Teng, Jun

2015-07-24

Carbonation is one of the major deteriorations that accelerate steel corrosion in reinforced concrete structures. Many mathematical/numerical models of the carbonation process, primarily diffusion-reaction models, have been established to predict the carbonation depth. However, the mass transfer of carbon dioxide in porous concrete includes molecular diffusion and convection mass transfer. In particular, the convection mass transfer induced by pressure difference is called penetration mass transfer. This paper presents the influence of penetration mass transfer on the carbonation. A penetration-reaction carbonation model was constructed and validated by accelerated test results under high pressure. Then the characteristics of wind pressure on the carbonation were investigated through finite element analysis considering steady and fluctuating wind flows. The results indicate that the wind pressure on the surface of concrete buildings results in deeper carbonation depth than that just considering the diffusion of carbon dioxide. In addition, the influence of wind pressure on carbonation tends to increase significantly with carbonation depth.

GALACTIC WINDS DRIVEN BY ISOTROPIC AND ANISOTROPIC COSMIC-RAY DIFFUSION IN DISK GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pakmor, R.; Pfrommer, C.; Simpson, C. M.

2016-06-20

The physics of cosmic rays (CRs) is a promising candidate for explaining the driving of galactic winds and outflows. Recent galaxy formation simulations have demonstrated the need for active CR transport either in the form of diffusion or streaming to successfully launch winds in galaxies. However, due to computational limitations, most previous simulations have modeled CR transport isotropically. Here, we discuss high-resolution simulations of isolated disk galaxies in a 10{sup 11} M {sub ⊙} halo with the moving-mesh code Arepo that include injection of CRs from supernovae, advective transport, CR cooling, and CR transport through isotropic or anisotropic diffusion. Wemore » show that either mode of diffusion leads to the formation of strong bipolar outflows. However, they develop significantly later in the simulation with anisotropic diffusion compared to the simulation with isotropic diffusion. Moreover, we find that isotropic diffusion allows most of the CRs to quickly diffuse out of the disk, while in the simulation with anisotropic diffusion, most CRs remain in the disk once the magnetic field becomes dominated by its azimuthal component, which occurs after ∼300 Myr. This has important consequences for the gas dynamics in the disk. In particular, we show that isotropic diffusion strongly suppresses the amplification of the magnetic field in the disk compared to anisotropic or no diffusion models. We therefore conclude that reliable simulations which include CR transport inevitably need to account for anisotropic diffusion.« less

Resolving the Origin of the Diffuse Soft X-ray Background

NASA Technical Reports Server (NTRS)

Smith, Randall K.; Foster, Adam R.; Edgar, Ricard J.; Brickhouse, Nancy S.; Sanders, Wilton T.

2012-01-01

In January 1993, the Diffuse X-ray Spectrometer (DXS) measured the first high-resolution spectrum of the diffuse soft X-ray background between 44-80A. A line-dominated spectrum characteristic of a 10(exp 6)K collisionally ionized plasma' was expected but while the observed spectrum was clearly line-dominated, no model would fit. Then in 2003 the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) launched and observed the diffuse extreme-ultraviolet (EUV) spectrum between 90- 265A. Although many emission lines were again expected; only Fe IX at 171.1A was detected. The discovery of X-rays from comets led to the realization that heavy ions (Z=6-28) in the solar wind will emit soft X-rays as the ions interact via charge exchange with neutral atoms in the heliosphere and geocorona. Using a new model for solar wind charge exchange (SWCX) emission, we show that the diffuse soft X-ray background can be understood as a combination of emission from charge exchange onto the slow and fast solar wind together with a more distant and diffuse hot (10(exp 6)K) plasma.

Augmentation of heat and mass transfer in laminar flow of suspensions: A correlation of data

NASA Astrophysics Data System (ADS)

Ahuja, Avtar S.

1980-01-01

The experimental data from literature on the augmentation of heat and gas transport in the laminar flow of suspensions of polystyrene spheres have been correlated on common coordinates. The correlation includes the influences of particle size, tube diameter and length, shear rate of flow, transport properties of diffusing species (heat or gas) in suspending liquids, and of the particle interactions on the augmentation of heat or gas transfer in flowing suspensions.

A Mars 1 Watt vortex wind energy machine

NASA Technical Reports Server (NTRS)

Ralston, Michael; Crowley, Christopher; Thomson, Ronald; Gwynne, Owen

1992-01-01

A Martian wind power generator capable of surviving impact and fulfilling the long-term (2-5 yr) low-level power requirements (1-2 W) of an unmanned surface probe is presented. Attention is given to a tornado vortex generator that was chosen on the basis of its capability to theoretically augment the available power that may be extracted for average Martian wind speeds of about 7.5 m/s. The generator offers comparable mass-to-power ratios with solar power sources.

Ion Layer Separation and Equilibrium Zonal Winds in Midlatitude Sporadic E

NASA Technical Reports Server (NTRS)

Earle, G. D.; Kane, T. J.; Pfaff, R. F.; Bounds, S. R.

2000-01-01

In-situ observations of a moderately strong mid-latitude sporadic-E layer show a separation in altitude between distinct sublayers composed of Fe(+), Mg(+), and NO(+). From these observations it is possible to estimate the zonal wind field consistent with diffusive equilibrium near the altitude of the layer. The amplitude of the zonal wind necessary to sustain the layer against diffusive effects is less than 10 meters per second, and the vertical wavelength is less than 10 km.

Wave Augmented Diffuser for Centrifugal Compressor

NASA Technical Reports Server (NTRS)

Skoch, Gary J. (Inventor); Paxson, Daniel E. (Inventor)

2001-01-01

A wave augmented diffuser for a centrifugal compressor surrounds the outlet of an impeller that rotates on a drive shaft having an axis of rotation. The impeller brings flow in in an axial direction and imparts kinetic energy to the flow discharging it in radial and tangential directions. The flow is discharged into a plurality of circumferentially disposed wave chambers. The wave chambers are periodically opened and closed by a rotary valve such that the flow through the diffuser is unsteady. The valve includes a plurality of valve openings that are periodically brought into and out of fluid communication with the wave chambers. When the wave chambers are closed, a reflected compression wave moves upstream towards the diffuser bringing the flow into the wave chamber to rest. This action recovers the kinetic energy from the flow and limits any boundary layer growth. The flow is then discharged in an axial direction through an opening in the valve plate when the valve plate is rotated to an open position. The diffuser thus efficiently raises the static pressure of the fluid and discharges an axially directed flow at a radius that is predominantly below the maximum radius of the diffuser.

Dynamic Distortion in a Short S-Shaped Subsonic Diffuser with Flow Separation. [Lewis 8 by 6 foot Supersonic Wind Tunnel

NASA Technical Reports Server (NTRS)

Stumpf, R.; Neumann, H. E.; Giamati, C. C.

1983-01-01

An experimental investigation of the time varying distortion at the diffuser exit of a subscale HiMAT forebody and inlet was conducted at Mach 0.9 in the Lewis 8 by 6 foot Supersonic Wind Tunnel. A transitory separation was detected within the subsonic diffuser. Vortex generators were installed to eliminate the flow separation. Results from a study of the instantaneous pressure variations at the diffuser exit are presented. The time unsteady total pressures at the diffuser exit are computer interpolated and presented in the form of a movie showing the transitory separation. Limited data showing the instantaneous distortion levels is also presented.

Experimental Investigations of Generalized Predictive Control for Tiltrotor Stability Augmentation

NASA Technical Reports Server (NTRS)

Nixon, Mark W.; Langston, Chester W.; Singleton, Jeffrey D.; Piatak, David J.; Kvaternik, Raymond G.; Bennett, Richard L.; Brown, Ross K.

2001-01-01

A team of researchers from the Army Research Laboratory, NASA Langley Research Center (LaRC), and Bell Helicopter-Textron, Inc. have completed hover-cell and wind-tunnel testing of a 1/5-size aeroelastically-scaled tiltrotor model using a new active control system for stability augmentation. The active system is based on a generalized predictive control (GPC) algorithm originally developed at NASA LaRC in 1997 for un-known disturbance rejection. Results of these investigations show that GPC combined with an active swashplate can significantly augment the damping and stability of tiltrotors in both hover and high-speed flight.

Magnetically advected winds

NASA Astrophysics Data System (ADS)

Contopoulos, I.; Kazanas, D.; Fukumura, K.

2017-11-01

Observations of X-ray absorption lines in magnetically driven disc winds around black hole binaries and active galactic nuclei yield a universal radial density profile ρ ∝ r-1.2 in the wind. This is in disagreement with the standard Blandford and Payne profile ρBP ∝ r-1.5 expected when the magnetic field is neither advected nor diffusing through the accretion disc. In order to account for this discrepancy, we establish a new paradigm for magnetically driven astrophysical winds according to which the large-scale ordered magnetic field that threads the disc is continuously generated by the Cosmic Battery around the inner edge of the disc and continuously diffuses outward. We obtain self-similar solutions of such magnetically advected winds (MAW) and discuss their observational ramifications.

Interdiffusion, Intrinsic Diffusion, Atomic Mobility, and Vacancy Wind Effect in γ(bcc) Uranium-Molybdenum Alloy

NASA Astrophysics Data System (ADS)

Huang, Ke; Keiser, Dennis D.; Sohn, Yongho

2013-02-01

U-Mo alloys are being developed as low enrichment uranium fuels under the Reduced Enrichment for Research and Test Reactor (RERTR) Program. In order to understand the fundamental diffusion behavior of this system, solid-to-solid pure U vs Mo diffusion couples were assembled and annealed at 923 K, 973 K, 1073 K, 1173 K, and 1273 K (650 °C, 700 °C, 800 °C, 900 °C, and 1000 °C) for various times. The interdiffusion microstructures and concentration profiles were examined via scanning electron microscopy and electron probe microanalysis, respectively. As the Mo concentration increased from 2 to 26 at. pct, the interdiffusion coefficient decreased, while the activation energy increased. A Kirkendall marker plane was clearly identified in each diffusion couple and utilized to determine intrinsic diffusion coefficients. Uranium intrinsically diffused 5-10 times faster than Mo. Molar excess Gibbs free energy of U-Mo alloy was applied to calculate the thermodynamic factor using ideal, regular, and subregular solution models. Based on the intrinsic diffusion coefficients and thermodynamic factors, Manning's formalism was used to calculate the tracer diffusion coefficients, atomic mobilities, and vacancy wind parameters of U and Mo at the marker composition. The tracer diffusion coefficients and atomic mobilities of U were about five times larger than those of Mo, and the vacancy wind effect increased the intrinsic flux of U by approximately 30 pct.

Arterial Wave Reflection and Aortic Valve Calcification in an Elderly Community-Based Cohort

PubMed Central

Sera, Fusako; Russo, Cesare; Iwata, Shinichi; Jin, Zhezhen; Rundek, Tatjana; Elkind, Mitchell S.V.; Homma, Shunichi; Sacco, Ralph L.; Di Tullio, Marco R.

2015-01-01

Background Aortic valve calcification (AVC) without stenosis is common in the elderly, is associated with cardiovascular morbidity and mortality, and may progress to aortic valve stenosis. Arterial stiffness and pulse wave reflection are important components of proximal aortic hemodynamics, but their relationship with AVC is not established. Methods To investigate the relationship of arterial wave reflection and stiffness with AVC, pulse wave analysis and AVC evaluation by echocardiography were performed in 867 participants from the Cardiovascular Abnormalities and Brain Lesions (CABL) study. Participants were divided into 4 categories based on the severity and extent of AVC: 1) none or mild focal AVC; 2) mild diffuse AVC; 3) moderate-severe focal AVC; and 4) moderate-severe diffuse AVC. Central blood pressures and pulse pressure, total arterial compliance, augmentation index, and time to wave reflection were assessed using applanation tonometry. Results Indicators of arterial stiffness and wave reflection were significantly associated with AVC severity, except for central systolic and diastolic pressures and time to reflection. After adjustment for pertinent covariates (age, sex, race/ethnicity, and eGFR), only augmentation pressure (P = .02) and augmentation index (P = .002) were associated with the severity of AVC. Multivariable logistic regression analysis revealed that augmentation pressure (odds ratio per mmHg = 1.14; 95% confidence interval, 1.02–1.27; P = .02) and augmentation index (odds ratio per percentage point = 1.07; 95% confidence interval, 1.01–1.13; P = .02) were associated with an increase risk of moderate-severe diffuse AVC, even when central blood pressure value was included in the same model. Conclusions Arterial wave reflection is associated with AVC severity, independent of blood pressure values. Increased contribution of wave reflection to central blood pressure could be involved in the process leading to AVC. PMID:25600036

Boundary Layer Model for Air Pollutant Concentrations Due to Highway Traffic

ERIC Educational Resources Information Center

Ragland, Kenneth W.; Peirce, J. Jeffrey

1975-01-01

A numerical solution of the three-dimensional steady-state diffusion equation for a finite width line source is presented. The wind speed and eddy diffusivity as a function of height above the roadway are obtained. Normalized ground level and elevated concentrations near a highway are obtained for winds perpendicular, parallel, and at 45 degrees.…

Plume meander and dispersion in a stable boundary layer

NASA Astrophysics Data System (ADS)

Hiscox, April L.; Miller, David R.; Nappo, Carmen J.

2010-11-01

Continuous lidar measurements of elevated plume dispersion and corresponding micrometeorology data are analyzed to establish the relationship between plume behavior and nocturnal boundary layer dynamics. Contrasting nights of data from the JORNADA field campaign in the New Mexico desert are analyzed. The aerosol lidar measurements were used to separate the plume diffusion (plume spread) from plume meander (displacement). Mutiresolution decomposition was used to separate the turbulence scale (<90 s) from the submesoscale (>90 s). Durations of turbulent kinetic energy stationarity and the wind steadiness were used to characterize the local scale and submesoscale turbulence. Plume meander, driven by submesoscale wind motions, was responsible for most of the total horizontal plume dispersion in weak and variable winds and strong stability. This proportion was reduced in high winds (i.e., >4 m s-1), weakly stable conditions but remained the dominant dispersion mechanism. The remainder of the plume dispersion in all cases was accounted for by internal spread of the plume, which is a small eddy diffusion process driven by turbulence. Turbulence stationarity and the wind steadiness are demonstrated to be closely related to plume diffusion and plume meander, respectively.

Comparison of model and flight test data for an augmented jet flap STOL research aircraft

NASA Technical Reports Server (NTRS)

Cook, W. L.; Whittley, D. C.

1975-01-01

Aerodynamic design data for the Augmented Jet Flap STOL Research Aircraft or commonly known as the Augmentor-Wing Jet-STOL Research Aircraft was based on results of tests carried out on a large scale research model in the NASA Ames 40- by 80-Foot Wind Tunnel. Since the model differs in some respects from the aircraft, precise correlation between tunnel and flight test is not expected, however the major areas of confidence derived from the wind tunnel tests are delineated, and for the most part, tunnel results compare favorably with flight experience. In some areas the model tests were known to be nonrepresentative so that a degree of uncertainty remained: these areas of greater uncertainty are identified, and discussed in the light of subsequent flight tests.

Long-Term Cognitive and Behavioral Therapies, Combined with Augmentative Communication, Are Related to Uncinate Fasciculus Integrity in Autism

ERIC Educational Resources Information Center

Pardini, Matteo; Elia, Maurizio; Garaci, Francesco G.; Guida, Silvia; Coniglione, Filadelfo; Krueger, Frank; Benassi, Francesca; Gialloreti, Leonardo Emberti

2012-01-01

Recent evidence points to white-matter abnormalities as a key factor in autism physiopathology. Using Diffusion Tensor Imaging, we studied white-matter structural properties in a convenience sample of twenty-two subjects with low-functioning autism exposed to long-term augmentative and alternative communication, combined with sessions of cognitive…

Climatology of Diffusion Potential Classes for Minneapolis-St. Paul.

NASA Astrophysics Data System (ADS)

Johnson, Allen B.; Baker, Donald G.

1997-12-01

This climatological study reports on the potential for atmospheric diffusion at Minneapolis-St. Paul, Minnesota, cities located in the heart of the North American continent. As such, the results can be considered typical of an urban setting within a continental climate.Data were obtained from a nearly continuous 8-yr record of vertical temperature and wind measurements made on a 152.4-m tower. Temperature lapse rates between 21.3 and 152.4 m were grouped into three stability categories: 1) isothermal-inversion, 2) subadiabatic, and 3) superadiabatic. A subdivision of each was based upon wind speeds of less than 4 m s1 and greater than or equal to 4 m s1, resulting in six classes that were examined according to wind direction, time of day, time of year and, most importantly, the associated synoptic conditions.The isothermal-inversion condition was limited to nighttime periods, especially when high pressure centers were dominant and winds were less than 4 m s1. The highest frequency of occurrence was during midsummer, while the lowest was during late fall and early winter. The subadiabatic condition was primarily a nighttime phenomenon, except for the winter season when it was also common during the day. An interesting feature of the diurnal frequencies was that a morning and evening subadiabatic peak occurred due to the transition between nighttime stable and the daytime unstable conditions. The superadiabatic condition was mainly a daytime phenomenon and dominated the early afternoon period throughout the year.The lowest diffusion potential, a result of very stable air and light winds, occurred during the nighttime period, particularly when under the influence of a high pressure center. Weak to moderate diffusion potential, found to occur with weakly stable air and light to moderate winds, was associated with the perimeter of the high pressure center and also with overcast skies near a low pressure center. This condition normally occurred during the night as well as during windy days. Moderate to high diffusion potential, resulting from superadiabatic conditions and light to moderate winds, dominated the early afternoon period. Strong nighttime ventilation was restricted to the winter season when northwesterly winds dominated the region immediately behind a cold front.

Exact diffusion constant in a lattice-gas wind-tree model on a Bethe lattice

NASA Astrophysics Data System (ADS)

Zhang, Guihua; Percus, J. K.

1992-02-01

Kong and Cohen [Phys. Rev. B 40, 4838 (1989)] obtained the diffusion constant of a lattice-gas wind-tree model in the Boltzmann approximation. The result is consistent with computer simulations for low tree concentration. In this Brief Report we find the exact diffusion constant of the model on a Bethe lattice, which turns out to be identical with the Kong-Cohen and Gunn-Ortuño results. Our interpretation is that the Boltzmann approximation is exact for this type of diffusion on a Bethe lattice in the same sense that the Bethe-Peierls approximation is exact for the Ising model on a Bethe lattice.

The electron diffusion coefficient in Jupiter's magnetosphere

NASA Technical Reports Server (NTRS)

Birmingham, T.; Northrop, T.; Baxter, R.; Hess, W.; Lojko, M.

1974-01-01

A steady-state model of Jupiter's electron radiation belt is developed. The model includes injection from the solar wind, radial diffusion, energy degradation by synchrotron radiation, and absorption at Jupiter's surface. A diffusion coefficient of the form D sub RR/R sub J squared = k times R to the m-th power is assumed, and then observed data on synchrotron radiation are used to fit the model. The free parameters determined from this fit are m = 1.95 plus or minus 0.5, k = 1.7 plus or minus 0.5 x 10 to the 9th power per sec, and the magnetic moment of injected particles equals 770 plus or minus 300 MeV/G. The value of m shows quite clearly that the diffusion is not caused by magnetic pumping by a variable solar wind or by a fluctuating convection electric field. The process might be field line exchange driven by atmospheric-ionospheric winds; our diffusion coefficient has roughly the same radial dependence but is considerably smaller in magnitude than the upper bound diffusion coefficients recently suggested for this process by Brice and McDonough (1973) and Jacques and Davis (1972).

DIFFUSION IN THE VICINITY OF STANDARD-DESIGN NUCLEAR POWER PLANTS-I. WIND-TUNNEL EVALUATION OF DIFFUSIVE CHARACTERISTICS OF A SIMULATED SUBURBAN NEUTRAL ATMOSPHERIC BOUNDARY LAYER

EPA Science Inventory

A large meteorological wind tunnel was used to simulate a suburban atmospheric boundary layer. The model-prototype scale was 1:300 and the roughness length was approximately 1.0 m full scale. The model boundary layer simulated full scale dispersion from ground-level and elevated ...

Determination of transport wind speed in the gaussian plume diffusion equation for low-lying point sources

NASA Astrophysics Data System (ADS)

Wang, I. T.

A general method for determining the effective transport wind speed, overlineu, in the Gaussian plume equation is discussed. Physical arguments are given for using the generalized overlineu instead of the often adopted release-level wind speed with the plume diffusion equation. Simple analytical expressions for overlineu applicable to low-level point releases and a wide range of atmospheric conditions are developed. A non-linear plume kinematic equation is derived using these expressions. Crosswind-integrated SF 6 concentration data from the 1983 PNL tracer experiment are used to evaluate the proposed analytical procedures along with the usual approach of using the release-level wind speed. Results of the evaluation are briefly discussed.

Air-sea fluxes of momentum and mass in the presence of wind waves

NASA Astrophysics Data System (ADS)

Zülicke, Christoph

2010-05-01

An air-sea interaction model (ASIM) is developed including the effect of wind waves on momentum and mass transfer. This includes the derivation of profiles of dissipation rate, flow speed and concentration from a certain height to a certain depth. Simplified assumptions on the turbulent closure, skin - bulk matching and the spectral wave model allow for an analytic treatment. Particular emphasis was put on the inclusion of primary (gravity) waves and secondary (capillary-gravity) waves. The model was tuned to match wall-flow theory and data on wave height and slope. Growing waves reduce the air-side turbulent stress and lead to an increasing drag coefficient. In the sea, breaking waves inject turbulent kinetic energy and accelerate the transfer. Cross-reference with data on wave-related momentum and energy flux, dissipation rate and transfer velocity was sufficient. The evaluation of ASIM allowed for the analytical calculation of bulk formulae for the wind-dependent gas transfer velocity including information on the air-side momentum transfer (drag coefficient) and the sea-side gas transfer (Dalton number). The following regimes have been identified: the smooth waveless regime with a transfer velocity proportional to (wind) × (diffusion)2-3, the primary wave regime with a wind speed dependence proportional to (wind)1-4 × (diffusion)1-2-(waveage)1-4 and the secondary wave regime including a more-than-linear wind speed dependence like (wind)15-8 × (diffusion)1-2 × (waveage)5-8. These findings complete the current understanding of air-sea interaction for medium winds between 2 and 20 m s^-1.

Heating Augmentation for Short Hypersonic Protuberances

NASA Technical Reports Server (NTRS)

Mazaheri, Alireza R.; Wood, William A.

2008-01-01

Computational aeroheating analyses of the Space Shuttle Orbiter plug repair models are validated against data collected in the Calspan University of Buffalo Research Center (CUBRC) 48 inch shock tunnel. The comparison shows that the average difference between computed heat transfer results and the data is about 9:5%. Using CFD and Wind Tunnel (WT) data, an empirical correlation for estimating heating augmentation on short hyper- sonic protuberances (k/delta < 0.33) is proposed. This proposed correlation is compared with several computed flight simulation cases and good agreement is achieved. Accordingly, this correlation is proposed for further investigation on other short hypersonic protuberances for estimating heating augmentation.

Heating Augmentation for Short Hypersonic Protuberances

NASA Technical Reports Server (NTRS)

Mazaheri, Ali R.; Wood, William A.

2008-01-01

Computational aeroheating analyses of the Space Shuttle Orbiter plug repair models are validated against data collected in the Calspan University of Buffalo Research Center (CUBRC) 48 inch shock tunnel. The comparison shows that the average difference between computed heat transfer results and the data is about 9.5%. Using CFD and Wind Tunnel (WT) data, an empirical correlation for estimating heating augmentation on short hypersonic protuberances (k/delta less than 0.3) is proposed. This proposed correlation is compared with several computed flight simulation cases and good agreement is achieved. Accordingly, this correlation is proposed for further investigation on other short hypersonic protuberances for estimating heating augmentation.

Heating Augmentation Due to Compression Pad Cavities on the Project Orion CEV Heat Shield

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

2009-01-01

An experimental study has been conducted to assess the effects of compression pad cavities on the aeroheating environment of the Project Orion CEV heat-shield. Testing was conducted in Mach 6 and Mach 10 perfect-gas wind tunnels to obtain heating measurements in and around the compression pads cavities using global phosphor thermography. Data were obtained over a wide range of Reynolds numbers that produced laminar, transitional, and turbulent flow within and downstream of the cavities. The effects of cavity dimensions on boundary-layer transition and heating augmentation levels were studied. Correlations were developed for transition onset and for the average cavity-heating augmentation.

Compression Pad Cavity Heating Augmentation on Orion Heat Shield

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

2011-01-01

An experimental study has been conducted to assess the effects of compression pad cavities on the aeroheating environment of the Project Orion Crew Exploration Vehicle heat shield. Testing was conducted in Mach 6 and 10 perfect-gas wind tunnels to obtain heating measurements in and around the compression pads cavities using global phosphor thermography. Data were obtained over a wide range of Reynolds numbers that produced laminar, transitional, and turbulent flow within and downstream of the cavities. The effects of cavity dimensions on boundary-layer transition and heating augmentation levels were studied. Correlations were developed for transition onset and for the average cavity-heating augmentation.

Effects of Wind and Freshwater on the Atlantic Meridional Overturning Circulation: Role of Sea Ice and Vertical Diffusion

NASA Astrophysics Data System (ADS)

Wang, Kun; Yang, Haijun; Dai, Haijin; Wang, Yuxing; Li, Qing

2015-04-01

Effects of wind and fresh water on the Atlantic meridional overturning circulation (AMOC) are investigated in a fully coupled climate model (CESM1.0). The AMOC can change significantly when perturbing either the wind stress or fresh water flux in the northern North Atlantic. This work pays special attention on the wind stress effect. Our model results show that the wind forcing is a crucial element in maintaining the AMOC. When the wind-stress is reduced, the vertical convection and diffusion are weakened immediately, triggering a salt deficit in the northern North Atlantic that prevents the deep water formation there. The salinity advection from the south, however, plays a contrary role to salt the upper ocean. As the AMOC weakens, the sea ice expends southward and melts, freshening the upper ocean that weakens the AMOC further. There is a positive feedback between the sea ice melting and AMOC strength, which eventually determines the AMOC strength in the reduced wind world.

Airborne detection of diffuse carbon dioxide emissions at Mammoth Mountain, California

USGS Publications Warehouse

Gerlach, T.M.; Doukas, M.P.; McGee, K.A.; Kessler, R.

1999-01-01

We report the first airborne detection of CO2 degassing from diffuse volcanic sources. Airborne measurement of diffuse CO2 degassing offers a rapid alternative for monitoring CO2 emission rates at Mammoth Mountain. CO2 concentrations, temperatures, and barometric pressures were measured at ~2,500 GPS-referenced locations during a one-hour, eleven-orbit survey of air around Mammoth Mountain at ~3 km from the summit and altitudes of 2,895-3,657 m. A volcanic CO2 anomaly 4-5 km across with CO2 levels ~1 ppm above background was revealed downwind of tree-kill areas. It contained a 1-km core with concentrations exceeding background by >3 ppm. Emission rates of ~250 t d-1 are indicated. Orographic winds may play a key role in transporting the diffusely degassed CO2 upslope to elevations where it is lofted into the regional wind system.We report the first airborne detection of CO2 degassing from diffuse volcanic sources. Airborne measurement of diffuse CO2 degassing offers a rapid alternative for monitoring CO2 emission rates at Mammoth Mountain. CO2 concentrations, temperatures, and barometric pressures were measured at approximately 2,500 GPS-referenced locations during a one-hour, eleven-orbit survey of air around Mammoth Mountain at approximately 3 km from the summit and altitudes of 2,895-3,657 m. A volcanic CO2 anomaly 4-5 km across with CO2 levels approximately 1 ppm above background was revealed downwind of tree-kill areas. It contained a 1-km core with concentrations exceeding background by >3 ppm. Emission rates of approximately 250 t d-1 are indicated. Orographic winds may play a key role in transporting the diffusely degassed CO2 upslope to elevations where it is lofted into the regional wind system.

Wind Engineering

NASA Technical Reports Server (NTRS)

1983-01-01

Dr. Jack Cermak, Director of Fluid Dynamics and Diffusion Laboratory, developed the first wind tunnel to simulate the changing temperatures, directions and velocities of natural winds. In this work, Cermak benefited from NASA technology related to what is known as the atmospheric boundary layer (ABL).

TURBULENCE IN THE SOLAR WIND MEASURED WITH COMET TAIL TEST PARTICLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeForest, C. E.; Howard, T. A.; Matthaeus, W. H.

2015-10-20

By analyzing the motions of test particles observed remotely in the tail of Comet Encke, we demonstrate that the solar wind undergoes turbulent processing enroute from the Sun to the Earth and that the kinetic energy entrained in the large-scale turbulence is sufficient to explain the well-known anomalous heating of the solar wind. Using the heliospheric imaging (HI-1) camera on board NASA's STEREO-A spacecraft, we have observed an ensemble of compact features in the comet tail as they became entrained in the solar wind near 0.4 AU. We find that the features are useful as test particles, via mean-motion analysismore » and a forward model of pickup dynamics. Using population analysis of the ensemble's relative motion, we find a regime of random-walk diffusion in the solar wind, followed, on larger scales, by a surprising regime of semiconfinement that we attribute to turbulent eddies in the solar wind. The entrained kinetic energy of the turbulent motions represents a sufficient energy reservoir to heat the solar wind to observed temperatures at 1 AU. We determine the Lagrangian-frame diffusion coefficient in the diffusive regime, derive upper limits for the small scale coherence length of solar wind turbulence, compare our results to existing Eulerian-frame measurements, and compare the turbulent velocity with the size of the observed eddies extrapolated to 1 AU. We conclude that the slow solar wind is fully mixed by turbulence on scales corresponding to a 1–2 hr crossing time at Earth; and that solar wind variability on timescales shorter than 1–2 hr is therefore dominated by turbulent processing rather than by direct solar effects.« less

A Trajectory Algorithm to Support En Route and Terminal Area Self-Spacing Concepts

NASA Technical Reports Server (NTRS)

Abbott, Terence S.

2007-01-01

This document describes an algorithm for the generation of a four dimensional aircraft trajectory. Input data for this algorithm are similar to an augmented Standard Terminal Arrival Route (STAR) with the augmentation in the form of altitude or speed crossing restrictions at waypoints on the route. Wind data at each waypoint are also inputs into this algorithm. The algorithm calculates the altitude, speed, along path distance, and along path time for each waypoint.

Doppler Lidar Vector Retrievals and Atmospheric Data Visualization in Mixed/Augmented Reality

NASA Astrophysics Data System (ADS)

Cherukuru, Nihanth Wagmi

Environmental remote sensing has seen rapid growth in the recent years and Doppler wind lidars have gained popularity primarily due to their non-intrusive, high spatial and temporal measurement capabilities. While lidar applications early on, relied on the radial velocity measurements alone, most of the practical applications in wind farm control and short term wind prediction require knowledge of the vector wind field. Over the past couple of years, multiple works on lidars have explored three primary methods of retrieving wind vectors viz., using homogeneous windfield assumption, computationally extensive variational methods and the use of multiple Doppler lidars. Building on prior research, the current three-part study, first demonstrates the capabilities of single and dual Doppler lidar retrievals in capturing downslope windstorm-type flows occurring at Arizona's Barringer Meteor Crater as a part of the METCRAX II field experiment. Next, to address the need for a reliable and computationally efficient vector retrieval for adaptive wind farm control applications, a novel 2D vector retrieval based on a variational formulation was developed and applied on lidar scans from an offshore wind farm and validated with data from a cup and vane anemometer installed on a nearby research platform. Finally, a novel data visualization technique using Mixed Reality (MR)/ Augmented Reality (AR) technology is presented to visualize data from atmospheric sensors. MR is an environment in which the user's visual perception of the real world is enhanced with live, interactive, computer generated sensory input (in this case, data from atmospheric sensors like Doppler lidars). A methodology using modern game development platforms is presented and demonstrated with lidar retrieved wind fields. In the current study, the possibility of using this technology to visualize data from atmospheric sensors in mixed reality is explored and demonstrated with lidar retrieved wind fields as well as a few earth science datasets for education and outreach activities.

Explaining CO2 fluctuations observed in snowpacks

NASA Astrophysics Data System (ADS)

Graham, Laura; Risk, David

2018-02-01

Winter soil carbon dioxide (CO2) respiration is a significant and understudied component of the global carbon (C) cycle. Winter soil CO2 fluxes can be surprisingly variable, owing to physical factors such as snowpack properties and wind. This study aimed to quantify the effects of advective transport of CO2 in soil-snow systems on the subdiurnal to diurnal (hours to days) timescale, use an enhanced diffusion model to replicate the effects of CO2 concentration depletions from persistent winds, and use a model-measure pairing to effectively explore what is happening in the field. We took continuous measurements of CO2 concentration gradients and meteorological data at a site in the Cape Breton Highlands of Nova Scotia, Canada, to determine the relationship between wind speeds and CO2 levels in snowpacks. We adapted a soil CO2 diffusion model for the soil-snow system and simulated stepwise changes in transport rate over a broad range of plausible synthetic cases. The goal was to mimic the changes we observed in CO2 snowpack concentration to help elucidate the mechanisms (diffusion, advection) responsible for observed variations. On subdiurnal to diurnal timescales with varying winds and constant snow levels, a strong negative relationship between wind speed and CO2 concentration within the snowpack was often identified. Modelling clearly demonstrated that diffusion alone was unable to replicate the high-frequency CO2 fluctuations, but simulations using above-atmospheric snowpack diffusivities (simulating advective transport within the snowpack) reproduced snow CO2 changes of the observed magnitude and speed. This confirmed that wind-induced ventilation contributed to episodic pulsed emissions from the snow surface and to suppressed snowpack concentrations. This study improves our understanding of winter CO2 dynamics to aid in continued quantification of the annual global C cycle and demonstrates a preference for continuous wintertime CO2 flux measurement systems.

Wind-US Unstructured Flow Solutions for a Transonic Diffuser

NASA Technical Reports Server (NTRS)

Mohler, Stanley R., Jr.

2005-01-01

The Wind-US Computational Fluid Dynamics flow solver computed flow solutions for a transonic diffusing duct. The calculations used an unstructured (hexahedral) grid. The Spalart-Allmaras turbulence model was used. Static pressures along the upper and lower wall agreed well with experiment, as did velocity profiles. The effect of the smoothing input parameters on convergence and solution accuracy was investigated. The meaning and proper use of these parameters are discussed for the benefit of Wind-US users. Finally, the unstructured solver is compared to the structured solver in terms of run times and solution accuracy.

Unloading Characteristics of Sand-drift in Wind-shallow Areas along Railway and the Effect of Sand Removal by Force of Wind

PubMed Central

Cheng, Jian-jun; Xin, Guo-Wei; Zhi, Ling-yan; Jiang, Fu-qiang

2017-01-01

Wind-shield walls decrease the velocity of wind-drift sand flow in transit. This results in sand accumulating in the wind-shadow zone of both windshield wall and track line, causing severe sand sediment hazard. This study reveals the characteristics of sand accumulation and the laws of wind-blown sand removal in the wind-shadow areas of three different types of windshield walls, utilizing three-dimensional numerical simulations and wind tunnel experiments and on-site sand sediment tests. The results revealed the formation of apparent vortex and acceleration zones on the leeward side of solid windshield walls. For uniform openings, the vortex area moved back and narrowed. When bottom-opening windshield walls were adopted, the track-supporting layer at the step became a conflux acceleration zone, forming a low velocity vortex zone near the track line. At high wind speeds, windshield walls with bottom-openings achieved improved sand dredging. Considering hydrodynamic mechanisms, the flow field structure on the leeward side of different types of windshield structures is a result of convergence and diffusion of fluids caused by an obstacle. This convergence and diffusion effect of air fluid is more apparent at high wind velocities, but not obvious at low wind velocities. PMID:28120915

Evaluation of observed blast loading effects on NIF x-ray diagnostic collimators.

PubMed

Masters, N D; Fisher, A; Kalantar, D; Prasad, R; Stölken, J S; Wlodarczyk, C

2014-11-01

We present the "debris wind" models used to estimate the impulsive load to which x-ray diagnostics and other structures are subject during National Ignition Facility experiments. These models are used as part of the engineering design process. Isotropic models, based on simulations or simplified "expanding shell" models, are augmented by debris wind multipliers to account for directional anisotropy. We present improvements to these multipliers based on measurements of the permanent deflections of diagnostic components: 4× for the polar direction and 2× within the equatorial plane-the latter relaxing the previous heuristic debris wind multiplier.

Development of an Apparatus for Wind Tunnel Dynamic Experiments at High-alpha

NASA Technical Reports Server (NTRS)

Pedreiro, Nelson

1997-01-01

A unique experimental apparatus that allows a wind tunnel model two degrees of freedom has been designed and built. The apparatus was developed to investigate the use of new methods to augment aircraft control in the high angle of attack regime. The model support system provides a platform in which the roll-yaw coupling at high angles of attack can be studied in a controlled environment. Active cancellation of external effects is used to provide a system in which the dynamics are dominated by the aerodynamic loads acting on the wind tunnel model.

Interpreting high time resolution galactic cosmic ray observations in a diffusive context

NASA Astrophysics Data System (ADS)

Jordan, A.; Spence, H. E.; Blake, J. B.; Shaul, D. A.

2009-12-01

We interpret galactic cosmic ray (GCR) variations near Earth within a diffusive context. The variations occur on time-/size-scales ranging from Forbush decreases (Fds), to substructure embedded within Fds, to smaller amplitude and shorter duration variations during relatively benign interplanetary conditions. We use high time resolution GCR observations from the High Sensitivity Telescope (HIST) on Polar and from the Spectrometer for INTEGRAL (SPI) and also use solar wind plasma and magnetic field observations from ACE and/or Wind. To calculate the coefficient of diffusion, we combine these datasets with a simple convection-diffusion model for relativistic charged particles in a magnetic field. We find reasonable agreement between our and previous estimates of the coefficient. We also show whether changes in the coefficient of diffusion are sufficient to explain the above GCR variations.

Softwall acoustical characteristics and measurement capabilities of the NASA Lewis 9x15 foot low speed wind tunnel

NASA Technical Reports Server (NTRS)

Rentz, P. E.

1976-01-01

Acoustical characteristics and source directionality measurement capabilities of the wind tunnel in the softwall configuration were evaluated, using aerodynamically clean microphone supports. The radius of measurement was limited by the size of the test section, instead of the 3.0 foot (1 m) limitation of the hardwall test section. The wind-on noise level in the test section was reduced 10 dB. Reflections from the microphone support boom, after absorptive covering, induced measurement errors in the lower frequency bands. Reflections from the diffuser back wall were shown to be significant. Tunnel noise coming up the diffuser was postulated as being responsible, at least partially, for the wind-on noise in the test section and settling chamber. The near field characteristics of finite-sized sources and the theoretical response of a porous strip sensor in the presence of wind are presented.

Arterial wave reflection and aortic valve calcification in an elderly community-based cohort.

PubMed

Sera, Fusako; Russo, Cesare; Iwata, Shinichi; Jin, Zhezhen; Rundek, Tatjana; Elkind, Mitchell S V; Homma, Shunichi; Sacco, Ralph L; Di Tullio, Marco R

2015-04-01

Aortic valve calcification (AVC) without stenosis is common in the elderly, is associated with cardiovascular morbidity and mortality, and may progress to aortic valve stenosis. Arterial stiffness and pulse-wave reflection are important components of proximal aortic hemodynamics, but their relationship with AVC is not established. To investigate the relationship of arterial wave reflection and stiffness with AVC, pulse wave analysis and AVC evaluation by echocardiography were performed in 867 participants from the Cardiovascular Abnormalities and Brain Lesions study. Participants were divided into four categories on the basis of the severity and extent of AVC: (1) none or mild focal AVC, (2) mild diffuse AVC, (3) moderate to severe focal AVC, and (4) moderate to severe diffuse AVC. Central blood pressures and pulse pressure, total arterial compliance, augmentation index, and time to wave reflection were assessed using applanation tonometry. Indicators of arterial stiffness and wave reflection were significantly associated with AVC severity, except for central systolic and diastolic pressures and time to reflection. After adjustment for pertinent covariates (age, sex, race/ethnicity, and estimated glomerular filtration rate), only augmentation pressure (P = .02) and augmentation index (P = .002) were associated with the severity of AVC. Multivariate logistic regression analysis revealed that augmentation pressure (odds ratio per mm Hg, 1.14; 95% confidence interval, 1.02-1.27; P = .02) and augmentation index (odds ratio per percentage point, 1.07; 95% confidence interval, 1.01-1.13; P = .02) were associated with an increased risk for moderate to severe diffuse AVC, even when central blood pressure value was included in the same model. Arterial wave reflection is associated with AVC severity, independent of blood pressure values. Increased contribution of wave reflection to central blood pressure could be involved in the process leading to AVC. Copyright © 2015 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

Anxiety sensitivity among Cambodian refugees with panic disorder: A factor analytic investigation.

PubMed

Hinton, Devon E; Pich, Vuth; Safren, Steven A; Pollack, Mark H; McNally, Richard J

2006-01-01

Among Cambodian refugees with panic disorder (N = 208), we performed two factor analyses, one with the ASI, another with an Augmented ASI (consisting of the 16-item ASI supplemented with a 9-item addendum that assesses additional Cambodian concerns about anxiety-related sensations). The principal component analysis of the ASI yielded a 3-factor solution (I, "Weak Heart Concerns"; II, "Social Concerns"; III, "Control Concerns"); the Augmented ASI, a 4-factor solution: I, "Wind Attack Concerns"; II, "Weak Heart Concerns"; III, "Social Concerns"; and IV, "Control Concerns." The item clustering within the factor solution of both the ASI and Augmented ASI illustrates the role of cultural syndromes in generating fear of mental and bodily events.

Wind effect on the Atlantic meridional overturning circulation via sea ice and vertical diffusion

NASA Astrophysics Data System (ADS)

Yang, Haijun; Wang, Kun; Dai, Haijin; Wang, Yuxing; Li, Qing

2016-06-01

Effects of wind and fresh water on the Atlantic meridional overturning circulation (AMOC) are investigated using a fully coupled climate model. The AMOC can change significantly when perturbed by either wind stress or freshwater flux in the North Atlantic. This study focuses on wind stress effect. Our model results show that the wind forcing is crucial in maintaining the AMOC. Reducing wind forcing over the ocean can cause immediately weakening of the vertical salinity diffusion and convection in the mid-high latitudes Atlantic, resulting in an enhancement of vertical salinity stratification that restrains the deep water formation there, triggering a slowdown of the thermohaline circulation. As the thermohaline circulation weakens, the sea ice expands southward and melts, providing the upper ocean with fresh water that weakens the thermohaline circulation further. The wind perturbation experiments suggest a positive feedback between sea-ice and thermohaline circulation strength, which can eventually result in a complete shutdown of the AMOC. This study also suggests that sea-ice variability may be also important to the natural AMOC variability on decadal and longer timescales.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, X.; Florinski, V.

We present a new model that couples galactic cosmic-ray (GCR) propagation with magnetic turbulence transport and the MHD background evolution in the heliosphere. The model is applied to the problem of the formation of corotating interaction regions (CIRs) during the last solar minimum from the period between 2007 and 2009. The numerical model simultaneously calculates the large-scale supersonic solar wind properties and its small-scale turbulent content from 0.3 au to the termination shock. Cosmic rays are then transported through the background, and thus computed, with diffusion coefficients derived from the solar wind turbulent properties, using a stochastic Parker approach. Ourmore » results demonstrate that GCR variations depend on the ratio of diffusion coefficients in the fast and slow solar winds. Stream interfaces inside the CIRs always lead to depressions of the GCR intensity. On the other hand, heliospheric current sheet (HCS) crossings do not appreciably affect GCR intensities in the model, which is consistent with the two observations under quiet solar wind conditions. Therefore, variations in diffusion coefficients associated with CIR stream interfaces are more important for GCR propagation than the drift effects of the HCS during a negative solar minimum.« less

Low-speed wind tunnel investigation of a semispan STOL jet transport wing body with an upper surface blown jet flap

NASA Technical Reports Server (NTRS)

Phelps, A. E., III; Letko, W.; Henderson, R. L.

1973-01-01

An investigation of the static longitudinal aerodynamic characteristics of a semispan STOL jet transport wing-body with an upper-surface blown jet flap for lift augmentation was conducted in a low-speed wind tunnel having a 12-ft octagonal test section. The semispan swept wing had an aspect ratio of 3.92 (7.84 for the full span) and had two simulated turbofan engines mounted ahead of and above the wing in a siamese pod equipped with an exhaust deflector. The purpose of the deflector was to spread the engine exhaust into a jet sheet attached to the upper surface of the wing so that it would turn downward over the flap and provide lift augmentation. The wing also had optional boundary-layer control provided by air blowing through a thin slot over a full-span plain trailing-edge flap.

High-Fidelity Thermal Radiation Models and Measurements for High-Pressure Reacting Laminar and Turbulent Flows

DTIC Science & Technology

2013-06-26

flow code used ( OpenFOAM ) to include differential diffusion and cell-based stochastic RTE solvers. The models were validated by simulation of laminar...wavenumber selection is improved about by a factor of 10. (5) OpenFOAM Improvements for Laminar Flames A laminar-diffusion combustion solver, taking into...account the effects of differential diffusion, was developed within the open source CFD package OpenFOAM [18]. In addition, OpenFOAM was augmented to take

Potential of wind power projects under the Clean Development Mechanism in India

PubMed Central

Purohit, Pallav; Michaelowa, Axel

2007-01-01

Background So far, the cumulative installed capacity of wind power projects in India is far below their gross potential (≤ 15%) despite very high level of policy support, tax benefits, long term financing schemes etc., for more than 10 years etc. One of the major barriers is the high costs of investments in these systems. The Clean Development Mechanism (CDM) of the Kyoto Protocol provides industrialized countries with an incentive to invest in emission reduction projects in developing countries to achieve a reduction in CO2 emissions at lowest cost that also promotes sustainable development in the host country. Wind power projects could be of interest under the CDM because they directly displace greenhouse gas emissions while contributing to sustainable rural development, if developed correctly. Results Our estimates indicate that there is a vast theoretical potential of CO2 mitigation by the use of wind energy in India. The annual potential Certified Emissions Reductions (CERs) of wind power projects in India could theoretically reach 86 million. Under more realistic assumptions about diffusion of wind power projects based on past experiences with the government-run programmes, annual CER volumes by 2012 could reach 41 to 67 million and 78 to 83 million by 2020. Conclusion The projections based on the past diffusion trend indicate that in India, even with highly favorable assumptions, the dissemination of wind power projects is not likely to reach its maximum estimated potential in another 15 years. CDM could help to achieve the maximum utilization potential more rapidly as compared to the current diffusion trend if supportive policies are introduced. PMID:17663772

Aerodynamic characteristics of a large-scale hybrid upper surface blown flap model having four engines

NASA Technical Reports Server (NTRS)

Carros, R. J.; Boissevain, A. G.; Aoyagi, K.

1975-01-01

Data are presented from an investigation of the aerodynamic characteristics of large-scale wind tunnel aircraft model that utilized a hybrid-upper surface blown flap to augment lift. The hybrid concept of this investigation used a portion of the turbofan exhaust air for blowing over the trailing edge flap to provide boundary layer control. The model, tested in the Ames 40- by 80-foot Wind Tunnel, had a 27.5 deg swept wing of aspect ratio 8 and 4 turbofan engines mounted on the upper surface of the wing. The lift of the model was augmented by turbofan exhaust impingement on the wind upper-surface and flap system. Results were obtained for three flap deflections, for some variation of engine nozzle configuration and for jet thrust coefficients from 0 to 3.0. Six-component longitudinal and lateral data are presented with four engine operation and with the critical engine out. In addition, a limited number of cross-plots of the data are presented. All of the tests were made with a downwash rake installed instead of a horizontal tail. Some of these downwash data are also presented.

VizieR Online Data Catalog: Solar wind 3D magnetohydrodynamic simulation (Chhiber+, 2017)

NASA Astrophysics Data System (ADS)

Chhiber, R.; Subedi, P.; Usmanov, A. V.; Matthaeus, W. H.; Ruffolo, D.; Goldstein, M. L.; Parashar, T. N.

2017-08-01

We use a three-dimensional magnetohydrodynamic simulation of the solar wind to calculate cosmic-ray diffusion coefficients throughout the inner heliosphere (2Rȯ-3au). The simulation resolves large-scale solar wind flow, which is coupled to small-scale fluctuations through a turbulence model. Simulation results specify background solar wind fields and turbulence parameters, which are used to compute diffusion coefficients and study their behavior in the inner heliosphere. The parallel mean free path (mfp) is evaluated using quasi-linear theory, while the perpendicular mfp is determined from nonlinear guiding center theory with the random ballistic interpretation. Several runs examine varying turbulent energy and different solar source dipole tilts. We find that for most of the inner heliosphere, the radial mfp is dominated by diffusion parallel to the mean magnetic field; the parallel mfp remains at least an order of magnitude larger than the perpendicular mfp, except in the heliospheric current sheet, where the perpendicular mfp may be a few times larger than the parallel mfp. In the ecliptic region, the perpendicular mfp may influence the radial mfp at heliocentric distances larger than 1.5au; our estimations of the parallel mfp in the ecliptic region at 1 au agree well with the Palmer "consensus" range of 0.08-0.3au. Solar activity increases perpendicular diffusion and reduces parallel diffusion. The parallel mfp mostly varies with rigidity (P) as P.33, and the perpendicular mfp is weakly dependent on P. The mfps are weakly influenced by the choice of long-wavelength power spectra. (2 data files).

Ionospheric Irregularities at Mars Probed by MARSIS Topside Sounding

NASA Astrophysics Data System (ADS)

Harada, Y.; Gurnett, D. A.; Kopf, A. J.; Halekas, J. S.; Ruhunusiri, S.

2018-01-01

The upper ionosphere of Mars contains a variety of perturbations driven by solar wind forcing from above and upward propagating atmospheric waves from below. Here we explore the global distribution and variability of ionospheric irregularities around the exobase at Mars by analyzing topside sounding data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument on board Mars Express. As irregular structure gives rise to off-vertical echoes with excess propagation time, the diffuseness of ionospheric echo traces can be used as a diagnostic tool for perturbed reflection surfaces. The observed properties of diffuse echoes above unmagnetized regions suggest that ionospheric irregularities with horizontal wavelengths of tens to hundreds of kilometers are particularly enhanced in the winter hemisphere and at high solar zenith angles. Given the known inverse dependence of neutral gravity wave amplitudes on the background atmospheric temperature, the ionospheric irregularities probed by MARSIS are most likely associated with plasma perturbations driven by atmospheric gravity waves. Though extreme events with unusually diffuse echoes are more frequently observed for high solar wind dynamic pressures during some time intervals, the vast majority of the diffuse echo events are unaffected by varying solar wind conditions, implying limited influence of solar wind forcing on the generation of ionospheric irregularities. Combination of remote and in situ measurements of ionospheric irregularities would offer the opportunity for a better understanding of the ionospheric dynamics at Mars.

Experimental data from coastal diffusion tests. [Smoke diffusion over coastal waters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raynor, G S; Brown, R M; SethuRaman, S

1976-10-01

Data are reported from a series of seven experiments on the diffusion of smoke plumes over northeast Atlantic Ocean coastal waters in response to wind fluctuations and other meteorological variables. A qualitative description of smoke behavior during each experiment is included and photographs of the smoke are included to illustrate the type of diffusion observed. (CH)

Design and Testing of Scaled Ejector-Diffusers for Jet Engine Test Facility Applications.

DTIC Science & Technology

1983-09-01

the test cell such that the exhaust will be vented into an augmenting tube which acts as an ejector -diffuser assembly. 11 The kinetic energy of the...OF STANDARDS-1963-A ..’I -Dy , - 77 *4********* Z 7.77- NAVAL POSTGRADUATE SCHOOL Monterey, California W I THESIS DESIGN AND TESTING OF SCALED EJECTOR ...PERIOD COVERED Design and Testing of Scaled Ejector - "flglfeerls Thesis~ Diffusers for Jet Engine Test Facility Spebr18 S. PERFORMING ORG. REPORT

The Pursuit of Profit or Prestige: What the Diffusion of MOOCs Can Tell Us about Disruptive Innovation in US Higher Education

ERIC Educational Resources Information Center

Pheatt, Lara E.

2017-01-01

Disruptive innovations are used to lower costs and augment access to high-quality, affordable higher education, but little systematic research is available on the topic. Higher education institutions use disruptive innovations to save students time and money. To understand the process of disruptive innovation, I investigated the rapid diffusion of…

Conceptual Design of a 100kW Energy Integrated Type Bi-Directional Tidal Current Turbine

NASA Astrophysics Data System (ADS)

Kim, Ki Pyoung; Ahmed, M. Rafiuddin; Lee, Young Ho

2010-06-01

The development of a tidal current turbine that can extract maximum energy from the tidal current will be extremely beneficial for supplying continuous electric power. The present paper presents a conceptual design of a 100kW energy integrated type tidal current turbine for tidal power generation. The instantaneous power density of a flowing fluid incident on an underwater turbine is proportional to the cubic power of current velocity which is approximately 2.5m/s. A cross-flow turbine, provided with a nozzle and a diffuser, is designed and analyzed. The potential advantages of ducted and diffuser-augmented turbines were taken into consideration in order to achieve higher output at a relatively low speed. This study looks at a cross-flow turbine system which is placed in an augmentation channel to generate electricity bi-directionally. The compatibility of this turbine system is verified using a commercial CFD code, ANSYSCFX. This paper presents the results of the numerical analysis in terms of pressure, streaklines, velocity vectors and performance curves for energy integrated type bi-directional tidal current turbine (BDT) with augmentation.

Design features of a low-disturbance supersonic wind tunnel for transition research at low supersonic Mach numbers

NASA Technical Reports Server (NTRS)

Wolf, Stephen W. D.; Laub, James A.; King, Lyndell S.; Reda, Daniel C.

1992-01-01

A unique, low-disturbance supersonic wind tunnel is being developed at NASA-Ames to support supersonic laminar flow control research at cruise Mach numbers of the High Speed Civil Transport (HSCT). The distinctive design features of this new quiet tunnel are a low-disturbance settling chamber, laminar boundary layers along the nozzle/test section walls, and steady supersonic diffuser flow. This paper discusses these important aspects of our quiet tunnel design and the studies necessary to support this design. Experimental results from an 1/8th-scale pilot supersonic wind tunnel are presented and discussed in association with theoretical predictions. Natural laminar flow on the test section walls is demonstrated and both settling chamber and supersonic diffuser performance is examined. The full-scale wind tunnel should be commissioned by the end of 1993.

The Martian climate and energy balance models with CO2/H2O atmospheres

NASA Technical Reports Server (NTRS)

Hoffert, M. I.

1986-01-01

The analysis begins with a seasonal energy balance model (EBM) for Mars. This is used to compute surface temperature versus x = sin(latitude) and time over the seasonal cycle. The core model also computes the evolving boundaries of the CO2 icecaps, net sublimational/condensation rates, and the resulting seasonal pressure wave. Model results are compared with surface temperature and pressure history data at Viking lander sites, indicating fairly good agreement when meridional heat transport is represented by a thermal diffusion coefficient D approx. 0.015 W/sq. m/K. Condensational wind distributions are also computed. An analytic model of Martian wind circulation is then proposed, as an extension of the EMB, which incorporates vertical wind profiles containing an x-dependent function evaluated by substitution in the equation defining the diffusion coefficient. This leads to a parameterization of D(x) and of the meridional circulation which recovers the high surface winds predicted by dynamic Mars atmosphere models (approx. 10 m/sec). Peak diffusion coefficients, D approx. 0.6 w/sq m/K, are found over strong Hadley zones - some 40 times larger than those of high-latitude baroclinic eddies. When the wind parameterization is used to find streamline patterns over Martian seasons, the resulting picture shows overturning hemispheric Hadley cells crossing the equator during solstices, and attaining peak intensities during the south summer dust storm season, while condensational winds are most important near the polar caps.

A Revised Trajectory Algorithm to Support En Route and Terminal Area Self-Spacing Concepts

NASA Technical Reports Server (NTRS)

Abbott, Terence S.

2010-01-01

This document describes an algorithm for the generation of a four dimensional trajectory. Input data for this algorithm are similar to an augmented Standard Terminal Arrival (STAR) with the augmentation in the form of altitude or speed crossing restrictions at waypoints on the route. This version of the algorithm accommodates descent Mach values that are different from the cruise Mach values. Wind data at each waypoint are also inputs into this algorithm. The algorithm calculates the altitude, speed, along path distance, and along path time for each waypoint.

THE CHANDRA X-RAY SURVEY OF PLANETARY NEBULAE (CHANPLANS): PROBING BINARITY, MAGNETIC FIELDS, AND WIND COLLISIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kastner, J. H.; Montez, R. Jr.; Rapson, V.

2012-08-15

We present an overview of the initial results from the Chandra Planetary Nebula Survey (CHANPLANS), the first systematic (volume-limited) Chandra X-Ray Observatory survey of planetary nebulae (PNe) in the solar neighborhood. The first phase of CHANPLANS targeted 21 mostly high-excitation PNe within {approx}1.5 kpc of Earth, yielding four detections of diffuse X-ray emission and nine detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within {approx}1.5 kpc that have been observed to date, we find an overall X-ray detection rate ofmore » {approx}70% for the 35 sample objects. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks-in most cases, 'hot bubbles'-formed by energetic wind collisions is detected in {approx}30%; five objects display both diffuse and point-like emission components. The presence (or absence) of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical nebulae are more likely to display X-ray emission (either point-like or diffuse) than molecule-rich, bipolar, or Ring-like nebulae. All but one of the point-like CSPNe X-ray sources display X-ray spectra that are harder than expected from hot ({approx}100 kK) central stars emitting as simple blackbodies; the lone apparent exception is the central star of the Dumbbell nebula, NGC 6853. These hard X-ray excesses may suggest a high frequency of binary companions to CSPNe. Other potential explanations include self-shocking winds or PN mass fallback. Most PNe detected as diffuse X-ray sources are elliptical nebulae that display a nested shell/halo structure and bright ansae; the diffuse X-ray emission regions are confined within inner, sharp-rimmed shells. All sample PNe that display diffuse X-ray emission have inner shell dynamical ages {approx}< 5 Multiplication-Sign 10{sup 3} yr, placing firm constraints on the timescale for strong shocks due to wind interactions in PNe. The high-energy emission arising in such wind shocks may contribute to the high excitation states of certain archetypical 'hot bubble' nebulae (e.g., NGC 2392, 3242, 6826, and 7009).« less

Hollow H II regions. II - Mechanism for wind energy dissipation and diffuse X-ray emission

NASA Astrophysics Data System (ADS)

Dorland, H.; Montmerle, T.

1987-05-01

The mechanism by which stellar-wind energy is dissipated near the shock in a hollow H II region (HHR) around a massive star is investigated theoretically, in the context of the HHR model developed by Dorland et al. (1986). The principles of nonlinear thermal conduction (especially the delocalizaton of conductive heat flux postulated for laboratory fusion plasmas) are reviewed; expressions for estimating heat fluxes are derived; a two-temperature approximation is employed to describe coupling between thermal conduction and wind-energy dissipation; and the determination of the flux-limit factor from X-ray observations is explained. The model is then applied to observational data for the Rosette nebula and Eta Car, and the results are presented graphically. The diffuse X-ray temperatures of HHRs are found to be in the range 2-16 keV and to depend uniquely on stellar-wind velocity, the value for an O star with wind velocity 2500 km/s being about 5 keV.

Modeling dynamic stall on wind turbine blades under rotationally augmented flow fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guntur, S.; Schreck, S.; Sorensen, N. N.

It is well known that airfoils under unsteady flow conditions with a periodically varying angle of attack exhibit aerodynamic characteristics different from those under steady flow conditions, a phenomenon commonly known as dynamic stall. It is also well known that the steady aerodynamic characteristics of airfoils in the inboard region of a rotating blade differ from those under steady two-dimensional (2D) flow conditions, a phenomenon commonly known as rotational augmentation. This paper presents an investigation of these two phenomena together in the inboard parts of wind turbine blades. This analysis is carried out using data from three sources: (1) themore » National Renewable Energy Laboratory’s Unsteady Aerodynamics Experiment Phase VI experimental data, including constant as well as continuously pitching blade conditions during axial operation, (2) data from unsteady Delayed Detached Eddy Simulations (DDES) carried out using the Technical University of Denmark’s in-house flow solver Ellipsys3D, and (3) data from a simplified model based on the blade element momentum method with a dynamic stall subroutine that uses rotationally augmented steady-state polars obtained from steady Phase VI experimental sequences, instead of the traditional 2D nonrotating data. The aim of this work is twofold. First, the blade loads estimated by the DDES simulations are compared to three select cases of the N sequence experimental data, which serves as a validation of the DDES method. Results show reasonable agreement between the two data in two out of three cases studied. Second, the dynamic time series of the lift and the moment polars obtained from the experiments are compared to those from the dynamic stall subroutine that uses the rotationally augmented steady polars. This allowed the differences between the stall phenomenon on the inboard parts of harmonically pitching blades on a rotating wind turbine and the classic dynamic stall representation in 2D flow to be investigated. Results from the dynamic stall subroutine indicated a good qualitative agreement between the model and the experimental data in many cases, which suggests that the current 2D dynamic stall model as used in BEM-based aeroelastic codes may provide a reasonably accurate representation of three-dimensional rotor aerodynamics when used in combination with a robust rotational augmentation model.« less

Influence of wind-induced air pressure fluctuations on topsoil gas concentrations within a Scots pine forest

NASA Astrophysics Data System (ADS)

Mohr, Manuel; Laemmel, Thomas; Maier, Martin; Schindler, Dirk

2017-04-01

Commonly it is assumed that soil gas transport is dominated by molecular diffusion. Few recent studies indicate that the atmosphere above the soil triggers non-diffusive gas transport processes in the soil, which can enhance soil gas transport and therefore soil gas efflux significantly. During high wind speed conditions, the so called pressure pumping effect has been observed: the enhancement of soil gas transport through dynamic changes in the air pressure field above the soil. However, the amplitudes and frequencies of the air pressure fluctuations responsible for pressure pumping are still uncertain. Moreover, an in situ observation of the pressure pumping effect is still missing. To investigate the pressure pumping effect, airflow measurements above and below the canopy of a Scots pine forest and high-precision relative air pressure measurements were conducted in the below-canopy space and in the soil over a measurement period of 16 weeks. To monitor the soil gas transport, a newly developed gas measurement system was used. The gas measurement system continuously injects helium as a tracer gas into the soil until a diffusive steady state is reached. With the steady state concentration profile of the tracer gas, it is possible to inversely model the gas diffusion coefficient profile of the soil. If the gas diffusion coefficient profile differed from steady state, we deduced that the soil gas transport is not only diffusive, but also influenced by non-diffusive processes. Results show that the occurrence of small air pressure fluctuations is strongly dependent on the mean above-canopy wind speed. The wind-induced air pressure fluctuations have mean amplitudes up to 10 Pa and lie in the frequency range 0.01-0.1 Hz. To describe the pumping motion of the air pressure field, the pressure pumping coefficient (PPC) was defined as the mean change in pressure per second. The PPC shows a clear quadratic dependence on mean above-canopy wind speed. Empirical modelling of the measured topsoil helium concentration demonstrated that the PPC is the most important predictor for changes in the topsoil helium concentration. Comparison of time periods with high PPC and periods of low PPC showed that the soil gas diffusion coefficient in depths between 5-10 cm increased up to 30% during periods of high PPC compared to steady state. Thus, the air pressure fluctuations observed in the atmosphere and described by the PPC penetrate into the soil and influence the topsoil gas transport.

Wind turbines acoustic measurements

NASA Astrophysics Data System (ADS)

Trematerra, Amelia; Iannace, Gino

2017-07-01

The importance of wind turbines has increased over the last few years throughout the European Community. The European energy policy guidelines state that for the year 2020 20% of all energy must be produced by alternative energy sources. Wind turbines are an important type of energy production without petrol. A wind speed in a range from 2.5 m/s to 25.0 m/s is needed. One of the obstacles to the widespread diffusion of wind turbine is noise generation. This work presents some noise measurements of wind turbines in the South of Italy, and discusses the noise problems for the people living near wind farms.

A study of the solar wind deceleration in the Earth's foreshock region

NASA Technical Reports Server (NTRS)

Zhang, T.-L.; Schwingenschuh, K.; Russell, C. T.

1995-01-01

Previous observations have shown that the solar wind is decelerated and deflected in the earth's upstream region populated by long-period waves. This deceleration is corelated with the 'diffuse' but not with the 'reflected' ion population. The speed of the solar wind may decrease tens of km/s in the foreshock region. The solar wind dynamic pressure exerted on the magnetopause may vary due to the fluctuation of the solar wind speed and density in the foreshock region. In this study, we examine this solar wind deceleration and determine how the solar wind deceleration varies in the foreshock region.

Jet Launching in Resistive GR-MHD Black Hole–Accretion Disk Systems

NASA Astrophysics Data System (ADS)

Qian, Qian; Fendt, Christian; Vourellis, Christos

2018-05-01

We investigate the launching mechanism of relativistic jets from black hole sources, in particular the strong winds from the surrounding accretion disk. Numerical investigations of the disk wind launching—the simulation of the accretion–ejection transition—have so far almost only been done for nonrelativistic systems. From these simulations we know that resistivity, or magnetic diffusivity, plays an important role for the launching process. Here we extend this treatment to general relativistic magnetohydrodynamics (GR-MHD), applying the resistive GR-MHD code rHARM. Our model setup considers a thin accretion disk threaded by a large-scale open magnetic field. We run a series of simulations with different Kerr parameter, field strength, and diffusivity level. Indeed, we find strong disk winds with, however, mildly relativistic speed, the latter most probably due to our limited computational domain. Further, we find that magnetic diffusivity lowers the efficiency of accretion and ejection, as it weakens the efficiency of the magnetic lever arm of the disk wind. As a major driving force of the disk wind we disentangle the toroidal magnetic field pressure gradient; however, magnetocentrifugal driving may also contribute. Black hole rotation in our simulations suppresses the accretion rate owing to an enhanced toroidal magnetic field pressure that seems to be induced by frame dragging. Comparing the energy fluxes from the Blandford–Znajek-driven central spine and the surrounding disk wind, we find that the total electromagnetic energy flux is dominated by the total matter energy flux of the disk wind (by a factor of 20). The kinetic energy flux of the matter outflow is comparatively small and comparable to the Blandford–Znajek electromagnetic energy flux.

Thermosolutal convection in high-aspect-ratio enclosures

NASA Technical Reports Server (NTRS)

Wang, L. W.; Chen, C. T.

1988-01-01

Convection in high-aspect-ratio rectangular enclosures with combined horizontal temperature and concentration gradients is studied experimentally. An electrochemical system is employed to impose the concentration gradients. The solutal buoyancy force either opposes or augments the thermal buoyancy force. Due to a large difference between the thermal and solutal diffusion rates the flow possesses double-diffusive characteristics. Various complex flow patterns are observed with different experimental conditions.

Impact of combustion products from Space Shuttle launches on ambient air quality

NASA Technical Reports Server (NTRS)

Dumbauld, R. K.; Bowers, J. F.; Cramer, H. E.

1974-01-01

The present work describes some multilayer diffusion models and a computer program for these models developed to predict the impact of ground clouds formed during Space Shuttle launches on ambient air quality. The diffusion models are based on the Gaussian plume equation for an instantaneous volume source. Cloud growth is estimated on the basis of measurable meteorological parameters: standard deviation of the wind azimuth angle, standard deviation of wind elevation angle, vertical wind-speed shear, vertical wind-direction shear, and depth of the surface mixing layer. Calculations using these models indicate that Space Shuttle launches under a variety of meteorological regimes at Kennedy Space Center and Vandenberg AFB are unlikely to endanger the exposure standards for HCl; similar results have been obtained for CO and Al2O3. However, the possibility that precipitation scavenging of the ground cloud might result in an acidic rain that could damage vegetation has not been investigated.

Exploring the making of a galactic wind in the starbursting dwarf irregular galaxy IC 10 with LOFAR

NASA Astrophysics Data System (ADS)

Heesen, V.; Rafferty, D. A.; Horneffer, A.; Beck, R.; Basu, A.; Westcott, J.; Hindson, L.; Brinks, E.; ChyŻy, K. T.; Scaife, A. M. M.; Brüggen, M.; Heald, G.; Fletcher, A.; Horellou, C.; Tabatabaei, F. S.; Paladino, R.; Nikiel-Wroczyński, B.; Hoeft, M.; Dettmar, R.-J.

2018-05-01

Low-mass galaxies are subject to strong galactic outflows, in which cosmic rays may play an important role; they can be best traced with low-frequency radio continuum observations, which are less affected by spectral ageing. We present a study of the nearby starburst dwarf irregular galaxy IC 10 using observations at 140 MHz with the Low-Frequency Array (LOFAR), at 1580 MHz with the Very Large Array (VLA), and at 6200 MHz with the VLA and the 100-m Effelsberg telescope. We find that IC 10 has a low-frequency radio halo, which manifests itself as a second component (thick disc) in the minor axis profiles of the non-thermal radio continuum emission at 140 and 1580 MHz. These profiles are then fitted with 1D cosmic ray transport models for pure diffusion and advection. We find that a diffusion model fits best, with a diffusion coefficient of D = (0.4-0.8) × 1026(E/GeV)0.5 cm2 s-1, which is at least an order of magnitude smaller than estimates both from anisotropic diffusion and the diffusion length. In contrast, advection models, which cannot be ruled out due to the mild inclination, while providing poorer fits, result in advection speeds close to the escape velocity of ≈ 50 km s- 1, as expected for a cosmic ray-driven wind. Our favoured model with an accelerating wind provides a self-consistent solution, where the magnetic field is in energy equipartition with both the warm neutral and warm ionized medium with an important contribution from cosmic rays. Consequently, cosmic rays can play a vital role for the launching of galactic winds in the disc-halo interface.

Preliminary design-lift/cruise fan research and technology airplane flight control system

NASA Technical Reports Server (NTRS)

Gotlieb, P.; Lewis, G. E.; Little, L. J.

1976-01-01

This report presents the preliminary design of a stability augmentation system for a NASA V/STOL research and technology airplane. This stability augmentation system is postulated as the simplest system that meets handling qualities levels for research and technology missions flown by NASA test pilots. The airplane studied in this report is a T-39 fitted with tilting lift/cruise fan nacelles and a nose fan. The propulsion system features a shaft interconnecting the three variable pitch fans and three power plants. The mathematical modeling is based on pre-wind tunnel test estimated data. The selected stability augmentation system uses variable gains scheduled with airspeed. Failure analysis of the system illustrates the benign effect of engine failure. Airplane rate sensor failure must be solved with redundancy.

The preliminary design of a lift-cruise fan airplane flight control system

NASA Technical Reports Server (NTRS)

Gotlieb, P.

1977-01-01

This paper presents the preliminary design of a stability augmentation system for a NASA V/STOL research and technology airplane. This stability augmentation system is postulated as the simplest system that meets handling-quality levels for research and technology missions flown by NASA test pilots. The airplane studied in this report is a modified T-39 fitted with tilting lift/cruise fan nacelles and a nose fan. The propulsion system features a shaft that interconnects three variable-pitch fans and three powerplants. The mathematical modeling is based on pre-wind tunnel test estimated data. The selected stability augmentation system uses variable gains scheduled with airspeed. Failure analysis of the system illustrates the benign effect of engine failure. Airplane rate sensor failure must be solved with redundancy.

A scale model wind tunnel study of dispersion in the Cleveland area. Laboratory simulation of lake breeze effects on diffusion from ground level emissions

NASA Technical Reports Server (NTRS)

Hoydysh, W. G.

1974-01-01

A wind tunnel simulation of the diffusion patterns in a sea breeze was attempted. The results indicate that the low level onshore flow was well simulated for neutral, stable, unstable, and elevated inversion conditions. Velocity, turbulence, shear stress, and temperature data were taken, and the spread of emissions from ground level sources was investigated. Comparison is made with theoretical predictions by E. Inoue and with the open, homogeneous plane field results of Pasquill. Agreement with the predictions by Inoue is good, and the comparison with Pasquill's results shows that the wind tunnel flows are shifted two categories towards more stable. The discrepancy may be explained as a matter of averaging time.

An augmented-reality edge enhancement application for Google Glass.

PubMed

Hwang, Alex D; Peli, Eli

2014-08-01

Google Glass provides a platform that can be easily extended to include a vision enhancement tool. We have implemented an augmented vision system on Glass, which overlays enhanced edge information over the wearer's real-world view, to provide contrast-improved central vision to the Glass wearers. The enhanced central vision can be naturally integrated with scanning. Google Glass' camera lens distortions were corrected by using an image warping. Because the camera and virtual display are horizontally separated by 16 mm, and the camera aiming and virtual display projection angle are off by 10°, the warped camera image had to go through a series of three-dimensional transformations to minimize parallax errors before the final projection to the Glass' see-through virtual display. All image processes were implemented to achieve near real-time performance. The impacts of the contrast enhancements were measured for three normal-vision subjects, with and without a diffuser film to simulate vision loss. For all three subjects, significantly improved contrast sensitivity was achieved when the subjects used the edge enhancements with a diffuser film. The performance boost is limited by the Glass camera's performance. The authors assume that this accounts for why performance improvements were observed only with the diffuser filter condition (simulating low vision). Improvements were measured with simulated visual impairments. With the benefit of see-through augmented reality edge enhancement, natural visual scanning process is possible and suggests that the device may provide better visual function in a cosmetically and ergonomically attractive format for patients with macular degeneration.

Surviving Hurricane Katrina: Winds of Change Transform a New Orleans Addiction Treatment Agency

ERIC Educational Resources Information Center

Toriello, Paul J.; Pedersen-Wasson, Else; Crisham, Erin M.; Ellis, Robert; Morse, Patricia; Morse, Edward V.

2007-01-01

Hurricane Katrina's impact on the operations of the largest residential, addiction treatment organization in New Orleans is described. Pre- and post-Katrina experiences are discussed and augmented with organizational performance data. Suggestions for future research are provided. (Contains 4 figures.)

Influence of wind-speed on short-duration NO2 measurements using Palmes and Ogawa passive diffusion samplers

NASA Astrophysics Data System (ADS)

Masey, Nicola; Gillespie, Jonathan; Heal, Mathew R.; Hamilton, Scott; Beverland, Iain J.

2017-07-01

We assessed the precision and accuracy of nitrogen dioxide (NO2) concentrations over 2-day, 3-day and 7-day exposure periods measured with the following types of passive diffusion samplers: standard (open) Palmes tubes; standard Ogawa samplers with commercially-prepared Ogawa absorbent pads (Ogawa[S]); and modified Ogawa samplers with absorbent-impregnated stainless steel meshes normally used in Palmes tubes (Ogawa[P]). We deployed these passive samplers close to the inlet of a chemiluminescence NO2 analyser at an urban background site in Glasgow, UK over 32 discrete measurement periods. Duplicate relative standard deviation was <7% for all passive samplers. The Ogawa[P], Ogawa[S] and Palmes samplers explained 93%, 87% and 58% of temporal variation in analyser concentrations respectively. Uptake rates for Palmes and Ogawa[S] samplers were positively and linearly associated with wind-speed (P < 0.01 and P < 0.05 respectively). Computation of adjusted uptake rates using average wind-speed observed during each sampling period increased the variation in analyser concentrations explained by Palmes and Ogawa[S] estimates to 90% and 92% respectively, suggesting that measurements can be corrected for shortening of diffusion path lengths due to wind-speed to improve the accuracy of estimates of short-term NO2 exposure. Monitoring situations where it is difficult to reliably estimate wind-speed variations, e.g. across multiple sites with different unknown exposures to local winds, and personal exposure monitoring, are likely to benefit from protection of these sampling devices from the effects of wind, for example by use of a mesh or membrane across the open end. The uptake rate of Ogawa[P] samplers was not associated with wind-speed resulting in a high correlation between estimated concentrations and observed analyser concentrations. The use of Palmes meshes in Ogawa[P] samplers reduced the cost of sampler preparation and removed uncertainty associated with the unknown manufacturing process for the commercially-prepared collection pads.

Magnetic field transfer device and method

DOEpatents

Wipf, S.L.

1990-02-13

A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180[degree] from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180[degree] from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils. 16 figs.

Magnetic field transfer device and method

DOEpatents

Wipf, Stefan L.

1990-01-01

A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180.degree. from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180.degree. from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils.

Effects of Creatine Monohydrate Augmentation on Brain Metabolic and Network Outcome Measures in Women With Major Depressive Disorder.

PubMed

Yoon, Sujung; Kim, Jieun E; Hwang, Jaeuk; Kim, Tae-Suk; Kang, Hee Jin; Namgung, Eun; Ban, Soonhyun; Oh, Subin; Yang, Jeongwon; Renshaw, Perry F; Lyoo, In Kyoon

2016-09-15

Creatine monohydrate (creatine) augmentation has the potential to accelerate the clinical responses to and enhance the overall efficacy of selective serotonin reuptake inhibitor treatment in women with major depressive disorder (MDD). Although it has been suggested that creatine augmentation may involve the restoration of brain energy metabolism, the mechanisms underlying its antidepressant efficacy are unknown. In a randomized, double-blind, placebo-controlled trial, 52 women with MDD were assigned to receive either creatine augmentation or placebo augmentation of escitalopram; 34 subjects participated in multimodal neuroimaging assessments at baseline and week 8. Age-matched healthy women (n = 39) were also assessed twice at the same intervals. Metabolic and network outcomes were measured for changes in prefrontal N-acetylaspartate and changes in rich club hub connections of the structural brain network using proton magnetic resonance spectroscopy and diffusion tensor imaging, respectively. We found MDD-related metabolic and network dysfunction at baseline. Improvement in depressive symptoms was greater in patients receiving creatine augmentation relative to placebo augmentation. After 8 weeks of treatment, prefrontal N-acetylaspartate levels increased significantly in the creatine augmentation group compared with the placebo augmentation group. Increment in rich club hub connections was also greater in the creatine augmentation group than in the placebo augmentation group. N-acetylaspartate levels and rich club connections increased after creatine augmentation of selective serotonin reuptake inhibitor treatment. Effects of creatine administration on brain energy metabolism and network organization may partly underlie its efficacy in treating women with MDD. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Altitude Performance Characteristics of Tail-pipe Burner with Variable-area Exhaust Nozzle

NASA Technical Reports Server (NTRS)

Jansen, Emmert T; Thorman, H Carl

1950-01-01

An investigation was conducted in the NACA Lewis altitude wind tunnel to determine effect of altitude and flight Mach number on performance of tail-pipe burner equipped with variable-area exhaust nozzle and installed on full-scale turbojet engine. At a given flight Mach number, with constant exhaust-gas and turbine-outlet temperatures, increasing altitude lowered the tail-pipe combustion efficiency and raised the specific fuel consumption while the augmented thrust ratio remained approximately constant. At a given altitude, increasing flight Mach number raised the combustion efficiency and augmented thrust ratio and lowered the specific fuel consumption.

Development and flight evaluation of an augmented stability active controls concept with a small tail

NASA Technical Reports Server (NTRS)

1980-01-01

Parasite drag reduction evaluation is composed of wind tunnel tests with a standard L-1011 tail and two reduced area tail configurations. Trim drag reduction is evaluated by rebalancing the airplane for relaxed static stability. This is accomplished by pumping water to tanks in the forward and aft of the airplane to acheive desired center of gravity location. Also, the L-1011 is modified to incorporate term and advanced augmented systems. By using advanced wings and aircraft relaxed static stability significant fuel savings can be realized. An airplane's dynamic stability becomes more sensitive for decreased tail size, relaxed static stability, and advanced wing configurations. Active control pitch augmentation will be used to acheive the required handling qualities. Flight tests will be performed to evaluate the pitch augmentation systems. The effect of elevator downrig on stabilizer/elevator hinge moments will be measured. For control system analysis, the normal acceleration feedback and pitch rate feedback are analyzed.

Simulations of surface winds at the Viking Lander sites using a one-level model

NASA Technical Reports Server (NTRS)

Bridger, Alison F. C.; Haberle, Robert M.

1992-01-01

The one-level model developed by Mass and Dempsey for use in predicting surface flows in regions of complex terrain was adapted to simulate surface flows at the Viking lander sites on Mars. In the one-level model, prediction equations for surface winds and temperatures are formulated and solved. Surface temperatures change with time in response to diabatic heating, horizontal advection, adiabatic heating and cooling effects, and horizontal diffusion. Surface winds can change in response to horizontal advection, pressure gradient forces, Coriolis forces, surface drag, and horizontal diffusion. Surface pressures are determined by integration of the hydrostatic equation from the surface to some reference level. The model has successfully simulated surface flows under a variety of conditions in complex-terrain regions on Earth.

Computational study: The influence of omni-directional guide vane on the flow pattern characteristic around Savonius wind turbine

NASA Astrophysics Data System (ADS)

Wicaksono, Yoga Arob; Tjahjana, D. D. D. P.

2017-01-01

Standart Savonius wind turbine have a low performance such as low coefficient of power and low coefficient of torque compared with another type of wind turbine. This phenomenon occurs because the wind stream can cause the negative pressure at the returning rotor. To solve this problem, standard Savonius combined with Omni Directional Guide Vane (ODGV) proposed. The aim of this research is to study the influence of ODGV on the flow pattern characteristic around of Savonius wind turbine. The numerical model is based on the Navier-Stokes equations with the standard k-ɛ turbulent model. This equation solved by a finite volume discretization method. This case was analyzed by commercial computational fluid dynamics solver such as SolidWorks Flow Simulations. Simulations were performed at the different wind directions; there are 0°, 30°,60° at 4 m/s wind speed. The numerical method validated with the past experimental data. The result indicated that the ODGV able to augment air flow to advancing rotor and decrease the negative pressure in the upstream of returning rotor compared to the bare Savonius wind turbine.

Cross-wind profiling based on the scattered wave scintillation in a telescope focus.

PubMed

Banakh, V A; Marakasov, D A; Vorontsov, M A

2007-11-20

The problem of wind profile reconstruction from scintillation of an optical wave scattered off a rough surface in a telescope focus plane is considered. Both the expression for the spatiotemporal correlation function and the algorithm of cross-wind velocity and direction profiles reconstruction based on the spatiotemporal spectrum of intensity of an optical wave scattered by a diffuse target in a turbulent atmosphere are presented. Computer simulations performed under conditions of weak optical turbulence show wind profiles reconstruction by the developed algorithm.

Using MLT Composition Observations to Evaluate Transport in a Comprehensive High Top Model

NASA Astrophysics Data System (ADS)

Smith, A. K.

2016-12-01

Gravity waves play an outsized role in the MLT: driving the mean meridional circulation, exerting a large degree of control over the mean winds and seasonal variations in temperature, and leading to diffusive vertical transport of heat and trace species. These waves are represented using a parameterization in the NCAR Whole Atmosphere Community Climate Model (WACCM), as in many other GCMs. To evaluate their impact, we need to consider not just the mean temperature and wind but the distributions of trace species that are affected by advection due to resolved winds and waves and diffusion associated with gravity wave dissipation. The responses of chemical species to changes in the gravity wave forcing are complex and sometimes unexpected. Transport and diffusion simultaneously affect all species and the heat and momentum budgets; subsequent interactions, and the strong dependence of reaction rates on temperature, affect the net impact of transport on the composition. In evaluating the model, we evaluate the simulations using a range of available observations of composition, including O, O3, CO, CO2, NO, NO2, OH, and H2O.

Preshock region acceleration of implanted cometary H(+) and O(+)

NASA Astrophysics Data System (ADS)

Gombosi, T. I.

1988-01-01

A self-consistent, three-fluid model of plasma transport and implanted ion acceleration in the unshocked solar wind is presented. The solar wind plasma is depleted by charge exchange with the expanding cometary exosphere, while implanted protons and heavy ions are produced by photoionization and charge transfer and lost by charge exchange. A generalized transport equation describing convection, adiabatic and diffusive velocity change, and the appropriate production terms is used to describe the evolution of the two cometary ion components, while the moments of the Boltzmann equation are used to calculate the solar wind density and pressure. The flow velocity is obtained self-consistently by combining the conservation equations of the three ion species. The results imply that second-order Fermi acceleration can explain the implanted spectra observed in the unshocked solar wind. Comparison of measured and calculated distribution indicates that spatial diffusion of implanted ions probably plays an important role in forming the energetic particle environment in the shock vicinity.

The structure of mass-loading shocks. [interaction of solar wind with cometary coma or local interstellar medium using two-fluid model

NASA Technical Reports Server (NTRS)

Zank, G. P.; Khabibrakhmanov, I. KH.; Story, T.

1993-01-01

A new two-fluid model which describes mass loading in the solar wind (e.g., the interaction of the solar wind with a cometary coma or the local interstellar medium) is presented. The self-consistent back-reaction of the mass-loaded ions is included through their effective scattering in low-frequency MHD turbulence and the invocation of a diffusive approximation. Such an approximation has the advantage of introducing self-consistent dissipation coefficients into the governing equations, thereby facilitating the investigation of the internal structure of shocks in mass-loading environments. To illustrate the utility of the new model, we consider the structure of cometary shocks in the hypersonic one-dimensional limit, finding that the incoming solar wind is slowed by both mass loading and the development of a large cometary ion pressure gradient. The shock is broadened and smoothed by the cometary ions with a thickness of the order of the cometary ion diffusion scale.

Factors of Renewable Energy Deployment and Empirical Studies of United States Wind Energy

NASA Astrophysics Data System (ADS)

Can Sener, Serife Elif

Considered essential for countries' development, energy demand is growing worldwide. Unlike conventional sources, the use of renewable energy sources has multiple benefits, including increased energy security, sustainable economic growth, and pollution reduction, in particular greenhouse gas emissions. Nevertheless, there is a considerable difference in the share of renewable energy sources in national energy portfolios. This dissertation contains a series of studies to provide an outlook on the existing renewable energy deployment literature and empirically identify the factors of wind energy generation capacity and wind energy policy diffusion in the U.S. The dissertation begins with a systematic literature review to identify drivers and barriers which could help in understanding the diverging paths of renewable energy deployment for countries. In the analysis, economic, environmental, and social factors are found to be drivers, whereas political, regulatory, technical potential and technological factors are not classified as either a driver or a barrier (i.e., undetermined). Each main category contains several subcategories, among which only national income is found to have a positive impact, whereas all other subcategories are considered undetermined. No significant barriers to the deployment of renewable energy sources are found over the analyzed period. Wind energy deployment within the states related to environmental and economic factors was seldom discussed in the literature. The second study of the dissertation is thus focused on the wind energy deployment in the United States. Wind energy is among the most promising clean energy sources and the United States has led the world in per capita newly installed generation capacity since 2000. In the second study, using a fixed-effects panel data regression analysis, the significance of a number of economic and environmental factors are investigated for 39 states from 2000 to 2015. The results suggested that the increase in economic factors is related to a significant increase in the installed wind energy capacity, whereas, the increase in environmental factors is related to a significant decrease in the installed wind capacity. The final study explores the factors of diffusion of state- and local-level wind energy support policies which are considered fundamental factors of the continuum and development of wind power in the United States. To reveal the internal determinants of state's wind energy policy diffusion, we further narrow the scope and control for the geographical region in the final study. We limit our analysis to seven neighboring Midwestern states, which are located in the center of United States wind energy corridor. Using data from 2008 to 2015, the study investigates the significance of the following internal factors: wind power potential, per capita gross state product, unemployment rate, per capita value of the agriculture sector, number of establishments in agricultural sector, and state government control. Through the addition of interaction terms, the study also considers the behavioral differences in the explanatory variables under Republican and non-Republican state governance. Our findings suggest that the economic development potential and related environmental benefits were the common motivation for state- and local-level policy makers. Lastly, technical terms and agricultural sector presence provides additional motives for the state level diffusion of wind energy policies. The findings of this dissertation are expected to contribute to the understanding of how countries and states might best stimulate and support renewable energy, and in particular wind energy, deployment.

An Augmented-Reality Edge Enhancement Application for Google Glass

PubMed Central

Hwang, Alex D.; Peli, Eli

2014-01-01

Purpose Google Glass provides a platform that can be easily extended to include a vision enhancement tool. We have implemented an augmented vision system on Glass, which overlays enhanced edge information over the wearer’s real world view, to provide contrast-improved central vision to the Glass wearers. The enhanced central vision can be naturally integrated with scanning. Methods Goggle Glass’s camera lens distortions were corrected by using an image warping. Since the camera and virtual display are horizontally separated by 16mm, and the camera aiming and virtual display projection angle are off by 10°, the warped camera image had to go through a series of 3D transformations to minimize parallax errors before the final projection to the Glass’ see-through virtual display. All image processes were implemented to achieve near real-time performance. The impacts of the contrast enhancements were measured for three normal vision subjects, with and without a diffuser film to simulate vision loss. Results For all three subjects, significantly improved contrast sensitivity was achieved when the subjects used the edge enhancements with a diffuser film. The performance boost is limited by the Glass camera’s performance. The authors assume this accounts for why performance improvements were observed only with the diffuser filter condition (simulating low vision). Conclusions Improvements were measured with simulated visual impairments. With the benefit of see-through augmented reality edge enhancement, natural visual scanning process is possible, and suggests that the device may provide better visual function in a cosmetically and ergonomically attractive format for patients with macular degeneration. PMID:24978871

Analysis of the performance of the drive system and diffuser of the Langley unitary plan wind tunnel

NASA Technical Reports Server (NTRS)

Hasel, L. E.; Stallings, R. L.

1981-01-01

A broad program was initiated at the Langley Research Center in 1973 to reduce the energy consumption of the laboratory. As a part of this program, the performance characteristics of the Unitary Plan Wind Tunnel were reexamined to determine if potential methods for incresing the operating efficiencies of the tunnel could be formulated. The results of that study are summarized. The performance characteristics of the drive system components and the variable-geometry diffuser system of the tunnel are documented and analyzed. Several potential methods for reducing the energy requirements of the facility are discussed.

A unified high-resolution wind and solar dataset from a rapidly updating numerical weather prediction model

DOE PAGES

James, Eric P.; Benjamin, Stanley G.; Marquis, Melinda

2016-10-28

A new gridded dataset for wind and solar resource estimation over the contiguous United States has been derived from hourly updated 1-h forecasts from the National Oceanic and Atmospheric Administration High-Resolution Rapid Refresh (HRRR) 3-km model composited over a three-year period (approximately 22 000 forecast model runs). The unique dataset features hourly data assimilation, and provides physically consistent wind and solar estimates for the renewable energy industry. The wind resource dataset shows strong similarity to that previously provided by a Department of Energy-funded study, and it includes estimates in southern Canada and northern Mexico. The solar resource dataset represents anmore » initial step towards application-specific fields such as global horizontal and direct normal irradiance. This combined dataset will continue to be augmented with new forecast data from the advanced HRRR atmospheric/land-surface model.« less

Predicting the weathering of fuel and oil spills: A diffusion-limited evaporation model.

PubMed

Kotzakoulakis, Konstantinos; George, Simon C

2018-01-01

The majority of the evaporation models currently available in the literature for the prediction of oil spill weathering do not take into account diffusion-limited mass transport and the formation of a concentration gradient in the oil phase. The altered surface concentration of the spill caused by diffusion-limited transport leads to a slower evaporation rate compared to the predictions of diffusion-agnostic evaporation models. The model presented in this study incorporates a diffusive layer in the oil phase and predicts the diffusion-limited evaporation rate. The information required is the composition of the fluid from gas chromatography or alternatively the distillation data. If the density or a single viscosity measurement is available the accuracy of the predictions is higher. Environmental conditions such as water temperature, air pressure and wind velocity are taken into account. The model was tested with synthetic mixtures, petroleum fuels and crude oils with initial viscosities ranging from 2 to 13,000 cSt. The tested temperatures varied from 0 °C to 23.4 °C and wind velocities from 0.3 to 3.8 m/s. The average absolute deviation (AAD) of the diffusion-limited model ranged between 1.62% and 24.87%. In comparison, the AAD of a diffusion-agnostic model ranged between 2.34% and 136.62% against the same tested fluids. Copyright © 2017 Elsevier Ltd. All rights reserved.

The dependence of cosmic ray-driven galactic winds on halo mass

NASA Astrophysics Data System (ADS)

Jacob, Svenja; Pakmor, Rüdiger; Simpson, Christine M.; Springel, Volker; Pfrommer, Christoph

2018-03-01

Galactic winds regulate star formation in disc galaxies and help to enrich the circum-galactic medium. They are therefore crucial for galaxy formation, but their driving mechanism is still poorly understood. Recent studies have demonstrated that cosmic rays (CRs) can drive outflows if active CR transport is taken into account. Using hydrodynamical simulations of isolated galaxies with virial masses between 1010 and 1013 M⊙, we study how the properties of CR-driven winds depend on halo mass. CRs are treated in a two-fluid approximation and their transport is modelled through isotropic or anisotropic diffusion. We find that CRs are only able to drive mass-loaded winds beyond the virial radius in haloes with masses below 1012 M⊙. For our lowest examined halo mass, the wind is roughly spherical and has velocities of ˜20 km s-1. With increasing halo mass, the wind becomes biconical and can reach 10 times higher velocities. The mass loading factor drops rapidly with virial mass, a dependence that approximately follows a power law with a slope between -1 and -2. This scaling is slightly steeper than observational inferences, and also steeper than commonly used prescriptions for wind feedback in cosmological simulations. The slope is quite robust to variations of the CR injection efficiency or the CR diffusion coefficient. In contrast to the mass loading, the energy loading shows no significant dependence on halo mass. While these scalings are close to successful heuristic models of wind feedback, the CR-driven winds in our present models are not yet powerful enough to fully account for the required feedback strength.

Analytic expressions for ULF wave radiation belt radial diffusion coefficients

PubMed Central

Ozeke, Louis G; Mann, Ian R; Murphy, Kyle R; Jonathan Rae, I; Milling, David K

2014-01-01

We present analytic expressions for ULF wave-derived radiation belt radial diffusion coefficients, as a function of L and Kp, which can easily be incorporated into global radiation belt transport models. The diffusion coefficients are derived from statistical representations of ULF wave power, electric field power mapped from ground magnetometer data, and compressional magnetic field power from in situ measurements. We show that the overall electric and magnetic diffusion coefficients are to a good approximation both independent of energy. We present example 1-D radial diffusion results from simulations driven by CRRES-observed time-dependent energy spectra at the outer boundary, under the action of radial diffusion driven by the new ULF wave radial diffusion coefficients and with empirical chorus wave loss terms (as a function of energy, Kp and L). There is excellent agreement between the differential flux produced by the 1-D, Kp-driven, radial diffusion model and CRRES observations of differential electron flux at 0.976 MeV—even though the model does not include the effects of local internal acceleration sources. Our results highlight not only the importance of correct specification of radial diffusion coefficients for developing accurate models but also show significant promise for belt specification based on relatively simple models driven by solar wind parameters such as solar wind speed or geomagnetic indices such as Kp. Key Points Analytic expressions for the radial diffusion coefficients are presented The coefficients do not dependent on energy or wave m value The electric field diffusion coefficient dominates over the magnetic PMID:26167440

A Trajectory Algorithm to Support En Route and Terminal Area Self-Spacing Concepts: Third Revision

NASA Technical Reports Server (NTRS)

Abbott, Terence S.

2012-01-01

This document describes an algorithm for the generation of a four dimensional trajectory. Input data for this algorithm are similar to an augmented Standard Terminal Arrival (STAR) with the augmentation in the form of altitude or speed crossing restrictions at waypoints on the route. This version of the algorithm accommodates constant radius turns and cruise altitude waypoints with calibrated airspeed, versus Mach, constraints. The algorithm calculates the altitude, speed, along path distance, and along path time for each waypoint. Wind data at each of these waypoints are also used for the calculation of ground speed and turn radius.

Transport rather than diffusion-dependent route for nitric oxide gas activity in alveolar epithelium.

PubMed

Brahmajothi, Mulugu V; Mason, S Nicholas; Whorton, A Richard; McMahon, Timothy J; Auten, Richard L

2010-07-15

The pathway by which inhaled NO gas enters pulmonary alveolar epithelial cells has not been directly tested. Although the expected mechanism is diffusion, another route is the formation of S-nitroso-L-cysteine, which then enters the cell through the L-type amino acid transporter (LAT). To determine if NO gas also enters alveolar epithelium this way, we exposed alveolar epithelial-rat type I, type II, L2, R3/1, and human A549-cells to NO gas at the air liquid interface in the presence of L- and D-cysteine+/-LAT competitors. NO gas exposure concentration dependently increased intracellular NO and S-nitrosothiol levels in the presence of L- but not D-cysteine, which was inhibited by LAT competitors, and was inversely proportional to diffusion distance. The effect of L-cysteine on NO uptake was also concentration dependent. Without preincubation with L-cysteine, NO uptake was significantly reduced. We found similar effects using ethyl nitrite gas in place of NO. Exposure to either gas induced activation of soluble guanylyl cylase in a parallel manner, consistent with LAT dependence. We conclude that NO gas uptake by alveolar epithelium achieves NO-based signaling predominantly by forming extracellular S-nitroso-L-cysteine that is taken up through LAT, rather than by diffusion. Augmenting extracellular S-nitroso-L-cysteine formation may augment pharmacological actions of inhaled NO gas. Copyright 2010 Elsevier Inc. All rights reserved.

A novel autologous scaffold for diced-cartilage grafts in dorsal augmentation rhinoplasty.

PubMed

Bullocks, Jamal M; Echo, Anthony; Guerra, Gerardo; Stal, Samuel; Yuksel, Eser

2011-08-01

Diced-cartilage grafts have been used for dorsal nasal augmentation for several years with good results. However, compounds such as Surgicel and temporalis fascia used as a wrap have inherent problems associated with them, predominantly inflammation and graft resorption. An autologous carrier could provide stabilization of cartilage grafts while avoiding the complications seen with earlier techniques. In our patients, a malleable construct was used for dorsal nasal augmentation in which autologous diced-cartilage grafts were stabilized with autologous tissue glue (ATG) created from platelet-rich plasma (platelet gel) and platelet-poor plasma (fibrin glue). A prospective analysis of 68 patients, who underwent dorsal nasal augmentation utilizing ATG and diced-cartilage grafts between 2005 and 2008, were included in the study. Although there was notable maintenance of the dorsal height, no complications occurred that required explantation over a mean follow-up of 15 months. The use of ATG to stabilize diced-cartilage grafts is a safe, reliable technique for dorsal nasal augmentation. The platelet gel provides growth factors while the fibrin glue creates a scaffold that allows stabilization and diffusion of nutrients to the cartilage graft.

RELATIVE CONTRIBUTION OF THE MAGNETIC FIELD BARRIER AND SOLAR WIND SPEED IN ICME-ASSOCIATED FORBUSH DECREASES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhaskar, Ankush; Vichare, Geeta; Subramanian, Prasad, E-mail: ankushbhaskar@gmail.com

2016-09-10

We study 50 cosmic-ray Forbush decreases (FDs) from the Oulu neutron monitor data during 1997–2005 that were associated with Earth-directed interplanetary coronal mass ejections (ICMEs). Such events are generally thought to arise due to the shielding of cosmic rays by a propagating diffusive barrier. The main processes at work are the diffusion of cosmic rays across the large-scale magnetic fields carried by the ICME and their advection by the solar wind. In an attempt to better understand the relative importance of these effects, we analyze the relationship between the FD profiles and those of the interplanetary magnetic field (B) andmore » the solar wind speed (V {sub sw}). Over the entire duration of a given FD, we find that the FD profile is generally (anti)correlated with the B and V {sub sw} profiles. This trend holds separately for the FD main and recovery phases too. For the recovery phases, however, the FD profile is highly anti-correlated with the V {sub sw} profile, but not with the B profile. While the total duration of the FD profile is similar to that of the V {sub sw} profile, it is significantly longer than that of the B profile. Using the convection–diffusion model, a significant contribution of advection by solar wind is found during the recovery phases of the FD.« less

Orientation of Anopheles gambiae (Diptera: Culicidae) to Plant-Host Volatiles in a Novel Diffusion-Cage Olfactometer

PubMed Central

Otienoburu, Philip E.; Nikbakhtzadeh, Mahmood R.; Foster, Woodbridge A.

2016-01-01

A novel diffusion-cage olfactometer tested the responses of Anopheles gambiae Giles to plant volatiles. Green-leaf volatiles are often released from cut or injured plant tissue and may alter the headspace of plants used in olfactometer assays. The diffusion-cage olfactometer is designed for use with whole, intact plants, hence giving a more realistic behavioral assay. Its simple plastic construction, ease of assembly, and accommodation to whole plants makes it a useful tool for measuring mosquito orientation to plant volatiles within large enclosures. We compared its performance to that of the more commonly used T-tube wind-tunnel olfactometer, by testing the orientation of mosquitoes to volatiles of a few prevalent plants of eastern Africa reportedly utilized by An. gambiae for sugar: Parthenium hysterophorus (Asteraceae), Ricinus communis (Euphorbiaceae), Lantana camara (Verbenaceae), and Senna occidentalis (Fabaceae). Results indicate that the diffusion-cage olfactometer is an effective alternative to conventional wind-tunnel olfactometers, to test mosquito orientation to plant volatiles under seminatural conditions. PMID:26502752

Stable dissipative optical vortex clusters by inhomogeneous effective diffusion.

PubMed

Li, Huishan; Lai, Shiquan; Qui, Yunli; Zhu, Xing; Xie, Jianing; Mihalache, Dumitru; He, Yingji

2017-10-30

We numerically show the generation of robust vortex clusters embedded in a two-dimensional beam propagating in a dissipative medium described by the generic cubic-quintic complex Ginzburg-Landau equation with an inhomogeneous effective diffusion term, which is asymmetrical in the two transverse directions and periodically modulated in the longitudinal direction. We show the generation of stable optical vortex clusters for different values of the winding number (topological charge) of the input optical beam. We have found that the number of individual vortex solitons that form the robust vortex cluster is equal to the winding number of the input beam. We have obtained the relationships between the amplitudes and oscillation periods of the inhomogeneous effective diffusion and the cubic gain and diffusion (viscosity) parameters, which depict the regions of existence and stability of vortex clusters. The obtained results offer a method to form robust vortex clusters embedded in two-dimensional optical beams, and we envisage potential applications in the area of structured light.

Super-Eddington stellar winds driven by near-surface energy deposition

NASA Astrophysics Data System (ADS)

Quataert, Eliot; Fernández, Rodrigo; Kasen, Daniel; Klion, Hannah; Paxton, Bill

2016-05-01

We develop analytic and numerical models of the properties of super-Eddington stellar winds, motivated by phases in stellar evolution when super-Eddington energy deposition (via, e.g. unstable fusion, wave heating, or a binary companion) heats a region near the stellar surface. This appears to occur in the giant eruptions of luminous blue variables (LBVs), Type IIn supernovae progenitors, classical novae, and X-ray bursts. We show that when the wind kinetic power exceeds Eddington, the photons are trapped and behave like a fluid. Convection does not play a significant role in the wind energy transport. The wind properties depend on the ratio of a characteristic speed in the problem v_crit˜ (dot{E} G)^{1/5} (where dot{E} is the heating rate) to the stellar escape speed near the heating region vesc(rh). For vcrit ≳ vesc(rh), the wind kinetic power at large radii dot{E}_w ˜ dot{E}. For vcrit ≲ vesc(rh), most of the energy is used to unbind the wind material and thus dot{E}_w ≲ dot{E}. Multidimensional hydrodynamic simulations without radiation diffusion using FLASH and one-dimensional hydrodynamic simulations with radiation diffusion using MESA are in good agreement with the analytic predictions. The photon luminosity from the wind is itself super-Eddington but in many cases the photon luminosity is likely dominated by `internal shocks' in the wind. We discuss the application of our models to eruptive mass-loss from massive stars and argue that the wind models described here can account for the broad properties of LBV outflows and the enhanced mass-loss in the years prior to Type IIn core-collapse supernovae.

Impact of Cosmic-Ray Transport on Galactic Winds

NASA Astrophysics Data System (ADS)

Farber, R.; Ruszkowski, M.; Yang, H.-Y. K.; Zweibel, E. G.

2018-04-01

The role of cosmic rays generated by supernovae and young stars has very recently begun to receive significant attention in studies of galaxy formation and evolution due to the realization that cosmic rays can efficiently accelerate galactic winds. Microscopic cosmic-ray transport processes are fundamental for determining the efficiency of cosmic-ray wind driving. Previous studies modeled cosmic-ray transport either via a constant diffusion coefficient or via streaming proportional to the Alfvén speed. However, in predominantly cold, neutral gas, cosmic rays can propagate faster than in the ionized medium, and the effective transport can be substantially larger; i.e., cosmic rays can decouple from the gas. We perform three-dimensional magnetohydrodynamical simulations of patches of galactic disks including the effects of cosmic rays. Our simulations include the decoupling of cosmic rays in the cold, neutral interstellar medium. We find that, compared to the ordinary diffusive cosmic-ray transport case, accounting for the decoupling leads to significantly different wind properties, such as the gas density and temperature, significantly broader spatial distribution of cosmic rays, and higher wind speed. These results have implications for X-ray, γ-ray, and radio emission, and for the magnetization and pollution of the circumgalactic medium by cosmic rays.

A GENERALIZED TWO-COMPONENT MODEL OF SOLAR WIND TURBULENCE AND AB INITIO DIFFUSION MEAN-FREE PATHS AND DRIFT LENGTHSCALES OF COSMIC RAYS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiengarten, T.; Fichtner, H.; Kleimann, J.

2016-12-10

We extend a two-component model for the evolution of fluctuations in the solar wind plasma so that it is fully three-dimensional (3D) and also coupled self-consistently to the large-scale magnetohydrodynamic equations describing the background solar wind. The two classes of fluctuations considered are a high-frequency parallel-propagating wave-like piece and a low-frequency quasi-two-dimensional component. For both components, the nonlinear dynamics is dominanted by quasi-perpendicular spectral cascades of energy. Driving of the fluctuations by, for example, velocity shear and pickup ions is included. Numerical solutions to the new model are obtained using the Cronos framework, and validated against previous simpler models. Comparing results frommore » the new model with spacecraft measurements, we find improved agreement relative to earlier models that employ prescribed background solar wind fields. Finally, the new results for the wave-like and quasi-two-dimensional fluctuations are used to calculate ab initio diffusion mean-free paths and drift lengthscales for the transport of cosmic rays in the turbulent solar wind.« less

A wind tunnel study of gaseous tracer dispersion in the convective boundary layer capped by a temperature inversion

NASA Astrophysics Data System (ADS)

Fedorovich, E.; Thäter, J.

Results are presented from wind tunnel simulations of gaseous pollutant dispersion in the atmospheric convective boundary layer (CBL) capped by a temperature inversion. The experiments were performed in the thermally stratified wind tunnel of the University of Karlsruhe, Germany. In the tunnel, the case of horizontally evolving, sheared CBL is reproduced. This distinguishes the employed experimental setup from the preceding laboratory and numerical CBL dispersion studies. The diffusive and mixing properties of turbulence in the studied CBL case have been found to be essentially dependent on the stage of the CBL evolution. Effects of the point source elevation on the horizontal variability of the concentration field, and on the ground level concentration as function of distance from the source have been investigated. The applicability of bottom-up/top-down diffusion concept in the simulated CBL case has been evaluated. The influence of surface wind shear and capping inversion strength on the pollutant dispersion and turbulent exchange across the CBL top has been demonstrated. The imposed positive shear across the inversion has been identified as inhibitor of the CBL growth. Comparisons of concentration patterns from the wind tunnel with water tank data are presented.

EFFECTS OF WIND SHEAR ON POLLUTION DISPERSION. (R827929)

EPA Science Inventory

Using an accurate numerical method for simulating the advection and diffusion of pollution puffs, it is demonstrated that point releases of pollution grow into a shape reflecting the vertical wind shear profile experienced by the puff within a time scale less than 4 h. Fo...

In-situ Plasma Analysis of Ion Kinetics in the Solar Wind and Hermean Magnetosphere

NASA Astrophysics Data System (ADS)

Tracy, Patrick J.

The heating of the solar wind and its interaction with the unique planetary magnetosphere of Mercury is the primary focus of this work. The first aspect of this study focused on the heavy ion population of the solar wind (A > 4 amu), and how well the signature of the heating process responsible for creating the solar wind is preserved in this heavy ion population. We found that this signature in the heavy ion population is primarily erased (thermalized) via Coulomb collisional interactions with solar wind protons. The heavy ions observed in collisionally young solar wind reveal a clear, stable dependence on mass, along with non-thermal heating that is not in agreement with current predictions based on turbulent transport and kinetic dissipation. Due to its weak magnetic dipole, the solar wind can impinge on the surface of Mercury, one of the processes contributing to the desorption of neutrals and, through ionization, ions that make up the planet's exosphere. Differentiating between surface mechanisms and analyzing magnetospheric plasma dynamics requires the quantification of a variety of ion species. A detailed forward model and a robust statistical method were created to identify new ion signatures in the measurement space of the FIPS instrument, formerly orbiting Mercury onboard the MESSENGER spacecraft. The recovery of new heavy ions species, including Al, Ne, Si, and Mg, along with tentative recoveries of S, Ar, K, and C, enable in depth studies of the plasma dynamics in the Hermean magnetosphere. The interaction of the solar wind with the bow shock of the Hermean magnetosphere leads to the creation of a foreshock region. New tools and methods were created to enable the analysis of the diffuse and Field Aligned Beam (FAB) populations in unique parameter regime of the Hermean foreshock. One result suggests that the energization process for the observed FABs can be explained by Shock Drift Acceleration, and not limited by the small spatial size of Mercury's bow shock. Analysis of diffuse populations shows that a connection time limited diffusive shock acceleration is likely responsible for the behavior of the observed energy distributions.

The Steady-State Transport of Oxygen through Hemoglobin Solutions

PubMed Central

Keller, K. H.; Friedlander, S. K.

1966-01-01

The steady-state transport of oxygen through hemoglobin solutions was studied to identify the mechanism of the diffusion augmentation observed at low oxygen tensions. A novel technique employing a platinum-silver oxygen electrode was developed to measure the effective diffusion coefficient of oxygen in steady-state transport. The measurements were made over a wider range of hemoglobin and oxygen concentrations than previously reported. Values of the Brownian motion diffusion coefficient of oxygen in hemoglobin solution were obtained as well as measurements of facilitated transport at low oxygen tensions. Transport rates up to ten times greater than ordinary diffusion rates were found. Predictions of oxygen flux were made assuming that the oxyhemoglobin transport coefficient was equal to the Brownian motion diffusivity which was measured in a separate set of experiments. The close correlation between prediction and experiment indicates that the diffusion of oxyhemoglobin is the mechanism by which steady-state oxygen transport is facilitated. PMID:5943608

Dispersion of Vapor from LNG Spills -- Simulation in a Meteorological Wind Tunnel of Spills at China Lake Naval Weapons Center, California.

DTIC Science & Technology

1979-03-01

and Diffusion Laboratory Department of Civil Engineering, , / """..,--. Colorado State University DOT-CG-75279-A) )V Fnrt Cnl lin. Colorado 80523 ype...Film Aspirating Probe ......... .. 20 3.5.2 Errors in Concentration Measurement . . 21 4.0 TEST PROGRAM RESULTS ..... ............... .. 23 4.1...Coriolis Force Viscous Diffusivity Prandtl number Pr = v/(k/P C ViThrma Diffusivity0 0 p Thermal Diffusivity Eckert number Ec = /Cpo (AT)o 5 For exact

A Semi-Analytical Model for Dispersion Modelling Studies in the Atmospheric Boundary Layer

NASA Astrophysics Data System (ADS)

Gupta, A.; Sharan, M.

2017-12-01

The severe impact of harmful air pollutants has always been a cause of concern for a wide variety of air quality analysis. The analytical models based on the solution of the advection-diffusion equation have been the first and remain the convenient way for modeling air pollutant dispersion as it is easy to handle the dispersion parameters and related physics in it. A mathematical model describing the crosswind integrated concentration is presented. The analytical solution to the resulting advection-diffusion equation is limited to a constant and simple profiles of eddy diffusivity and wind speed. In practice, the wind speed depends on the vertical height above the ground and eddy diffusivity profiles on the downwind distance from the source as well as the vertical height. In the present model, a method of eigen-function expansion is used to solve the resulting partial differential equation with the appropriate boundary conditions. This leads to a system of first order ordinary differential equations with a coefficient matrix depending on the downwind distance. The solution of this system, in general, can be expressed in terms of Peano-baker series which is not easy to compute, particularly when the coefficient matrix becomes non-commutative (Martin et al., 1967). An approach based on Taylor's series expansion is introduced to find the numerical solution of first order system. The method is applied to various profiles of wind speed and eddy diffusivities. The solution computed from the proposed methodology is found to be efficient and accurate in comparison to those available in the literature. The performance of the model is evaluated with the diffusion datasets from Copenhagen (Gryning et al., 1987) and Hanford (Doran et al., 1985). In addition, the proposed method is used to deduce three dimensional concentrations by considering the Gaussian distribution in crosswind direction, which is also evaluated with diffusion data corresponding to a continuous point source.

Carbon diffusion in molten uranium: an ab initio molecular dynamics study

NASA Astrophysics Data System (ADS)

Garrett, Kerry E.; Abrecht, David G.; Kessler, Sean H.; Henson, Neil J.; Devanathan, Ram; Schwantes, Jon M.; Reilly, Dallas D.

2018-04-01

In this work we used ab initio molecular dynamics within the framework of density functional theory and the projector-augmented wave method to study carbon diffusion in liquid uranium at temperatures above 1600 K. The electronic interactions of carbon and uranium were described using the local density approximation (LDA). The self-diffusion of uranium based on this approach is compared with literature computational and experimental results for liquid uranium. The temperature dependence of carbon and uranium diffusion in the melt was evaluated by fitting the resulting diffusion coefficients to an Arrhenius relationship. We found that the LDA calculated activation energy for carbon was nearly twice that of uranium: 0.55 ± 0.03 eV for carbon compared to 0.32 ± 0.04 eV for uranium. Structural analysis of the liquid uranium-carbon system is also discussed.

Theoretical Investigation Leading to Energy Storage in Atomic and Molecular Systems

DTIC Science & Technology

1990-12-01

can be calculated in a single run. 21 j) Non-gradient optimization of basis function exponents is possible. The source code can be modified to carry...basis. The 10s3p/5s3p basis consists of the 9s/4s contraction of Siegbahn and Liu (Reference 91) augmented by a diffuse s-type function ( exponent ...vibrational modes. Introduction of diffuse basis functions and optimization of the d-orbital exponents have a small but important effect on the

Methodology of shell structure reinforcement layout optimization

NASA Astrophysics Data System (ADS)

Szafrański, Tomasz; Małachowski, Jerzy; Damaziak, Krzysztof

2018-01-01

This paper presents an optimization process of a reinforced shell diffuser intended for a small wind turbine (rated power of 3 kW). The diffuser structure consists of multiple reinforcement and metal skin. This kind of structure is suitable for optimization in terms of selection of reinforcement density, stringers cross sections, sheet thickness, etc. The optimisation approach assumes the reduction of the amount of work to be done between the optimization process and the final product design. The proposed optimization methodology is based on application of a genetic algorithm to generate the optimal reinforcement layout. The obtained results are the basis for modifying the existing Small Wind Turbine (SWT) design.

THE EFFECT OF DIFFUSION ON THE PARTICLE SPECTRA IN PULSAR WIND NEBULAE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vorster, M. J.; Moraal, H., E-mail: 12792322@nwu.ac.za

2013-03-01

A possible way to calculate particle spectra as a function of position in pulsar wind nebulae is to solve a Fokker-Planck transport equation. This paper presents numerical solutions to the transport equation with the processes of convection, diffusion, adiabatic losses, and synchrotron radiation included. In the first part of the paper, the steady-state version of the transport equation is solved as a function of position and energy. This is done to distinguish the various effects of the aforementioned processes on the solutions to the transport equation. The second part of the paper deals with a time-dependent solution to the transportmore » equation, specifically taking into account the effect of a moving outer boundary. The paper highlights the fact that diffusion can play a significant role in reducing the amount of synchrotron losses, leading to a modification in the expected particle spectra. These modified spectra can explain the change in the photon index of the synchrotron emission as a function of position. The solutions presented in this paper are not limited to pulsar wind nebulae, but can be applied to any similar central source system, e.g., globular clusters.« less

Solar-wind/magnetospheric dynamos: MHD-scale collective entry of the solar wind energy, momentum and mass into the magnetosphere

NASA Technical Reports Server (NTRS)

Song, Yan; Lysak, Robert L.

1992-01-01

A quasi open MHD (Magnetohydrodynamic) scale anomalous transport controlled boundary layer model is proposed, where the MHD collective behavior of magnetofluids (direct dynamo effect, anomalous viscous interaction and anomalous diffusion of the mass and the magnetic field) plays the main role in the conversion of the Solar Wind (SW) kinetic and magnetic energy into electromagnetic energy in the Magnetosphere (MSp). The so called direct and indirect dynamo effects are based on inductive and purely dissipative energy conversion, respectively. The self organization ability of vector fields in turbulent magnetofluids implies an inductive response of the plasma, which leads to the direct dynamo effect. The direct dynamo effect describes the direct formation of localized field aligned currents and the transverse Alfven waves and provides a source for MHD scale anomalous diffusivity and viscosity. The SW/MSp coupling depends on the dynamo efficiency.

Quantitative Analysis of Diffusion-Weighted Imaging for Diagnosis of Puerperal Breast Abscess After Polyacrylamide Hydrogel Augmentation Mammoplasty: Compared with Other Conventional Modalities.

PubMed

Liu, Lihua; Long, Miaomiao; Wang, Junping; Liu, Ning; Ge, Xihong; Hu, Zhandong; Shen, Wen

2015-02-01

Puerperal breast abscess after polyacrylamide hydrogel (PAAG) augmentation mammoplasty can induce breast auto-inflation resulting in serious consequences. Mammography, ultrasound, and conventional MRI are poor at detecting related PAAG abnormality histologically. We evaluated the value of diffusion-weighted imaging (DWI) in the quantitative analysis of puerperal PAAG abscess after augmentation mammoplasty. This was a retrospective study, and a waiver for informed consent was granted. Sixteen puerperal women with breast discomfort underwent conventional breast non-enhanced MRI and axial DWI using a 3T MR scanner. Qualitative analysis of the signal intensity on DWI and conventional sequences was performed. The apparent diffusion coefficient (ADC) values of the affected and contralateral normal PAAG cysts were measured quantitatively. Paired t test was used to evaluate whether there was significant difference. Both affected and normal PAAG cysts showed equal signal intensity on conventional T1WI and fat saturation T2WI, which were not helpful in detecting puerperal PAAG abscess. However, the affected PAAG cysts had a significantly decreased ADC value of 1.477 ± 0.332 × 10(-3)mm(2)/s and showed obvious hypo-intensity on the ADC map and increased signal intensity on DWI compared with the ADC value of 2.775 ± 0.233 × 10(-3)mm(2)/s of the contralateral normal PAAG cysts. DWI and quantitative measurement of ADC values are of great value for the diagnosis of puerperal PAAG abscess. Standardized MRI should be suggested to these puerperal women with breast discomfort or just for the purpose of check up. DWI should be selected as the essential MRI sequence.

Atmospheric response in aurora experiment: Observations of E and F region neutral winds in a region of postmidnight diffuse aurora

NASA Technical Reports Server (NTRS)

Larsen, M. F.; Marshall, T. R.; Mikkelsen, I. S.; Emery, B. A.; Christensen, A.; Kayser, D.; Hecht, J.; Lyons, L.; Walterscheid, R.

1995-01-01

The goal of the Atmospheric Response in Aurora (ARIA) experiment carried out at Poker Flat, Alaska, on March 3, 1992, was to determine the response of the neutral atmosphere to the long-lived, large-scale forcing that is characteristic of the diffuse aurora in the post midnight sector. A combination of chemical release rocket wind measurements, instrumented rocket composition measurements, and ground-based optical measurements were used to characterize the response of the neutral atmosphere. The rocket measurements were made at the end of a 90-min period of strong Joule heating. We focus on the neutral wind measurements made with the rocket. The forcing was determined by running the assimilated mapping of ionospheric electrodynamics (AMIE) analysis procedure developed at the National Center for Atmospheric Research. The winds expected at the latitude and longitude of the experiment were calculated using the spectral thermospheric general circulation model developed at the Danish Meteorological Institute. Comparisons of the observations and the model suggest that the neutral winds responded strongly in two height ranges. An eastward wind perturbation of approximately 100 m/s developed between 140 and 200 km altitude with a peak near 160 km. A southwestward wind with peak magnitude of approximately 150 m/s developed near 115 km altitude. The large amplitude winds at the lower altitude are particularly surprising. They appear to be associated with the upward propagating semidiurnal tide. However, the amplitude is much larger than predicted by any of the tidal models, and the shear found just below the peak in the winds was nominally unstable with a Richardson number of approximately 0.08.

Computational Study of Separating Flow in a Planar Subsonic Diffuser

NASA Technical Reports Server (NTRS)

DalBello, Teryn; Dippold, Vance, III; Georgiadis, Nicholas J.

2005-01-01

A computational study of the separated flow through a 2-D asymmetric subsonic diffuser has been performed. The Wind Computational Fluid Dynamics code is used to predict the separation and reattachment behavior for an incompressible diffuser flow. The diffuser inlet flow is a two-dimensional, turbulent, and fully-developed channel flow with a Reynolds number of 20,000 based on the centerline velocity and the channel height. Wind solutions computed with the Menter SST, Chien k-epsilon, Spalart-Allmaras and Explicit Algebraic Reynolds Stress turbulence models are compared with experimentally measured velocity profiles and skin friction along the upper and lower walls. In addition to the turbulence model study, the effects of grid resolution and use of wall functions were investigated. The grid studies varied the number of grid points across the diffuser and varied the initial wall spacing from y(sup +) = 0.2 to 60. The wall function study assessed the applicability of wall functions for analysis of separated flow. The SST and Explicit Algebraic Stress models provide the best agreement with experimental data, and it is recommended wall functions should only be used with a high level of caution.

Investigation of Perforated Convergent-divergent Diffusers with Initial Boundary Layer

NASA Technical Reports Server (NTRS)

Weinstein, Maynard I

1950-01-01

An experimental investigation was made at Mach number 1.90 of the performance of a series of perforated convergent-divergent supersonic diffusers operating with initial boundary layer, which was induced and controlled by lengths of cylindrical inlets affixed to the diffusers. Supercritical mass-flow and peak total-pressure recoveries were decreased slightly by use of the longest inlets (4 inlet diameters in length). Combinations of cylindrical inlets, perforated diffusers, and subsonic diffuser were evaluated as simulated wind tunnels having second throats. Comparisons with noncontracted configurations of similar scale indicated conservatively computed power reductions of 25 percent.

Modeling of sediment transport in a saltwater lake with supplemental sandy freshwater.

PubMed

Liang, Li; Deng, Yun; Li, Ran; Li, Jia

2018-06-22

Considering the highly complex flow structure of saltwater lakes during freshwater supplementation, a three-dimensional numerical model was developed to simulate suspended sediment transport in saltwater lakes. The model was validated using measurements of the salinity and sediment concentration during a pumping test at Yamdrok Lake. The simulation results were in quantitative agreement with the measured data. The observed and simulated results also indicated that the wind stress and vertical salinity gradient have a significant influence on salinity and sediment transport in a saltwater lake. The validated model was then used to predict and analyze the contributions of wind, the supplement flow rate and salinity stratification to the sediment transport process in Yamdrok Lake during continuous river water supplementation. The simulation results showed that after the sandy river water was continuously discharged into the saltwater lake, the lateral diffusion trends of the sediment exhibited three stages: linear growth in the inflow direction, logarithmic growth in the wind direction, and stabilization. Furthermore, wind was the dominant factor in driving the lake flow pattern and sediment transport. Specifically, wind can effectively reduce the area of the sediment diffusion zone by increasing the lateral sediment carrying and dilution capacities. The effect of inflow on the lake current is negligible, but the extent of the sediment turbidity zone mainly depends on the inflow. Reducing the inflow discharge can decrease the area of the sediment turbidity zone to proportions that far exceed the proportions of inflow discharge reductions. In addition, the high-salinity lake water can support the supplemented freshwater via buoyancy forces, which weaken vertical mixing and sediment settlement and increase lake currents and sediment diffusion near the surface.

Calculations of the cosmic ray modulation in interplanetary space taking into account the possible dependence of the transport travel for the scattering of the particles and of the velocity of the solar winds on the angles they make with the helioequator plane: The case of isotropic diffusion

NASA Technical Reports Server (NTRS)

Dorman, L. I.; Kobilinski, Z.

1975-01-01

The modulation of galactic cosmic rays is studied by the magnetic heterogeneities stream on the assumption that the diffusion coefficient is reduced whereas the solar wind velocity is increased with the growth of the angle between the sun's rotation axis and the direction of solar plasma motion. The stationary plane problem of isotropic diffusion is solved as it applies to two cases: (1) with due account of particle retardation by the antiphermium mechanism; and (2) without an account of the above mechanism. This problem is solved by the grid method in the polar coordinate system. The results of the calculations are followed by a discussion of the method of solution and of the errors.

Jupiter's outer atmosphere.

NASA Technical Reports Server (NTRS)

Brice, N. M.

1973-01-01

The current state of the theory of Jupiter's outer atmosphere is briefly reviewed. The similarities and dissimilarities between the terrestrial and Jovian upper atmospheres are discussed, including the interaction of the solar wind with the planetary magnetic fields. Estimates of Jovian parameters are given, including magnetosphere and auroral zone sizes, ionospheric conductivity, energy inputs, and solar wind parameters at Jupiter. The influence of the large centrifugal force on the cold plasma distribution is considered. The Jovian Van Allen belt is attributed to solar wind particles diffused in toward the planet by dynamo electric fields from ionospheric neutral winds, and the consequences of this theory are indicated.

Low-Speed Wind-Tunnel Investigation to Determine the Aerodynamic Characteristics of a Rectangular Wing Equipped with a Full-Span and an Inboard Half-Span Jet-Augmented Flap Deflected 55 deg

NASA Technical Reports Server (NTRS)

Gainer, Thomas G.

1959-01-01

An investigation to determine the aerodynamic characteristics of a rectangular wing equipped with a full-span and an inboard half-span jet-augmented flap has been made in the Langley 300 MPH 7- by 10-foot tunnel. The wing had an aspect ratio of 8.3 and a thickness-chord ratio of 0.167. A jet of air was blown backward through a small gap, tangentially to the upper surface of a round trailing edge, and was separated from the trailing edge by a very small flap at an angle of 55 deg with respect to the wing-chord plane. The results of the investigation showed that the ratio of total lift to jet-reaction lift for the wing was about 35 percent less for the half-span jet-augmented flap than for the full-span jet-augmented flap. The reduction of the span of the jet-augmented flap from full to half span reduced the maximum value of jet-circulation lift coefficient that could be produced from about 6.8 to a value of about 2.2. The half-span jet- augmented flap gave thrust recoveries considerably poorer than those obtained with the full-span jet-augmented flap. Large nose-down pitching- moment coefficients were produced by the half-span flap, with the greater part of these being the result of the larger jet reactions required to produce a given lift for the half-spin flap compared with that required for the full-span flap.

Wind influence on a coastal buoyant outflow

NASA Astrophysics Data System (ADS)

Whitney, Michael M.; Garvine, Richard W.

2005-03-01

This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the direction of Kelvin wave propagation) as a slender buoyancy-driven coastal current. Downwelling favorable winds augment this down-shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy-driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along-shelf flow is in a wind-driven or buoyancy-driven state. Ws is the ratio of the wind-driven and buoyancy-driven along-shelf velocities. Wind influence on across-shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind-driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high-river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy-driven most of the time (∣Ws∣ < 1 on average). Wind events, however, overwhelm the buoyancy-driven flow (∣Ws∣ > 1) several times during the high-discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across-shelf plume structure is more sensitive to wind influence than the along-shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.

Small wind systems field evaluation. Volume I. Program description. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dodge, D.M.; Liske, C.

1982-07-01

A Field Evaluation Program (FEP) was developed in 1978 to assist in the commercialization process for small wind systems. The program is described, and a description is provided of the institutional issues and barriers encountered and measures taken to assist the state and local governments in resolving them. Barriers were found to involve not only government regulations, but also the distribution of costs and benefits of wind technology and the rate of diffusion of knowledge about wind technology. The availability of capital to finance the production and purchase of wind machines, and the training of qualified dealers and service personnelmore » were also considerable problem areas. (LEW)« less

Entrainment and thrust augmentation in pulsatile ejector flows

NASA Technical Reports Server (NTRS)

Sarohia, V.; Bernal, L.; Bui, T.

1981-01-01

This study comprised direct thrust measurements, flow visualization by use of a spark shadowgraph technique, and mean and fluctuating velocity measurements with a pitot tube and linearized constant temperature hot-wire anemometry respectively. A gain in thrust of as much as 10 to 15% was observed for the pulsatile ejector flow as compared to the steady flow configuration. From the velocity profile measurements, it is concluded that this enhanced augmentation for pulsatile flow as compared to a nonpulsatile one was accomplished by a corresponding increased entrainment by the primary jet flow. It is also concluded that the augmentation and total entrainment by a constant area ejector critically depends upon the inlet geometry of the ejector. Experiments were performed to evaluate the influence of primary jet to ejector area ratio, ejector length, and presence of a diffuser on pulsatile ejector performance.

Experimental Investigation of Project Orion Crew Exploration Vehicle Aeroheating in AEDC Tunnel 9

NASA Technical Reports Server (NTRS)

Hollis, Brian R.; Horvath, Thomas J.; Berger, Karen T.; Lillard, Randolph P.; Kirk, Benjamin S.; Coblish, Joseph J.; Norris, Joseph D.

2008-01-01

An investigation of the aeroheating environment of the Project Orion Crew Entry Vehicle has been performed in the Arnold Engineering Development Center Tunnel 9. The goals of this test were to measure turbulent heating augmentation levels on the heat shield and to obtain high-fidelity heating data for assessment of computational fluid dynamics methods. Laminar and turbulent predictions were generated for all wind tunnel test conditions and comparisons were performed with the data for the purpose of helping to define uncertainty margins for the computational method. Data from both the wind tunnel test and the computational study are presented herein.

Free-flight investigation of forebody blowing for stability and control

NASA Technical Reports Server (NTRS)

Brandon, Jay M.; Simon, James M.; Owens, D. Bruce; Kiddy, Jason S.

1996-01-01

A free-flight wind-tunnel investigation was conducted on a generic fighter model with forebody pneumatic vortex control for high angle-of-attack directional control. This is believed to be the first flight demonstration of a forebody blowing concept integrated into a closed-loop flight control system for stability augmentation and control. The investigation showed that the static wind tunnel estimates of the yaw control available generally agreed with flight results. The control scheme for the blowing nozzles consisted of an on/off control with a deadband. Controlled flight was obtained for the model using forebody blowing for directional control to beyond 45 deg. angle of attack.

Low-speed aerodynamic characteristics of a generic forward-swept-wing aircraft

NASA Technical Reports Server (NTRS)

Ross, J. C.; Matarazzo, A. D.

1982-01-01

Low-speed wind-tunnel tests were performed on a generic forward-swept-wing aircraft model in the 7- by 10-Foot Wind Tunnel (No. 2) at Ames Research Center. The effects of various configurational changes and control-surface deflections on the performance of the model were measured. Six-component force measurements were augmented by flow-visualization photographs, using both surface oil-flow and tufts. It was found that the tendency toward premature root separation on the forward-swept wing could be reduced by use of either canards or leading-edge wing strakes and that differential canard deflections can be used to produce a direct side-force control.

A simple predictive model for the structure of the oceanic pycnocline

PubMed

Gnanadesikan

1999-03-26

A simple theory for the large-scale oceanic circulation is developed, relating pycnocline depth, Northern Hemisphere sinking, and low-latitude upwelling to pycnocline diffusivity and Southern Ocean winds and eddies. The results show that Southern Ocean processes help maintain the global ocean structure and that pycnocline diffusion controls low-latitude upwelling.

A GENERALIZED MATHEMATICAL SCHEME TO ANALYTICALLY SOLVE THE ATMOSPHERIC DIFFUSION EQUATION WITH DRY DEPOSITION. (R825689C072)

EPA Science Inventory

Abstract

A generalized mathematical scheme is developed to simulate the turbulent dispersion of pollutants which are adsorbed or deposit to the ground. The scheme is an analytical (exact) solution of the atmospheric diffusion equation with height-dependent wind speed a...

The multinomial simulation algorithm for discrete stochastic simulation of reaction-diffusion systems.

PubMed

Lampoudi, Sotiria; Gillespie, Dan T; Petzold, Linda R

2009-03-07

The Inhomogeneous Stochastic Simulation Algorithm (ISSA) is a variant of the stochastic simulation algorithm in which the spatially inhomogeneous volume of the system is divided into homogeneous subvolumes, and the chemical reactions in those subvolumes are augmented by diffusive transfers of molecules between adjacent subvolumes. The ISSA can be prohibitively slow when the system is such that diffusive transfers occur much more frequently than chemical reactions. In this paper we present the Multinomial Simulation Algorithm (MSA), which is designed to, on the one hand, outperform the ISSA when diffusive transfer events outnumber reaction events, and on the other, to handle small reactant populations with greater accuracy than deterministic-stochastic hybrid algorithms. The MSA treats reactions in the usual ISSA fashion, but uses appropriately conditioned binomial random variables for representing the net numbers of molecules diffusing from any given subvolume to a neighbor within a prescribed distance. Simulation results illustrate the benefits of the algorithm.

Carbon diffusion in molten uranium: an ab initio molecular dynamics study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garrett, Kerry E.; Abrecht, David G.; Kessler, Sean H.

In this work we used ab initio molecular dynamics (AIMD) within the framework of density functional theory (DFT) and the projector-augmented wave (PAW) method to study carbon diffusion in liquid uranium at temperatures above 1600 K. The electronic interactions of carbon and uranium were described using the local density approximation (LDA). The self-diffusion of uranium based on this approach is compared with literature computational and experimental results for liquid uranium. The temperature dependence of carbon and uranium diffusion in the melt was evaluated by fitting the resulting diffusion coefficients to an Arrhenius relationship. We found that the LDA calculated activationmore » energy for carbon was nearly twice that of uranium: 0.55±0.03 eV for carbon compared to 0.32±0.04 eV for uranium. Structural analysis of the liquid uranium-carbon system is also discussed.« less

Augmented Adaptive Control of a Wind Turbine in the Presence of Structural Modes

NASA Technical Reports Server (NTRS)

Frost, Susan A.; Balas, Mark J.; Wright, Alan D.

2010-01-01

Wind turbines operate in highly turbulent environments resulting in aerodynamic loads that can easily excite turbine structural modes, potentially causing component fatigue and failure. Two key technology drivers for turbine manufacturers are increasing turbine up time and reducing maintenance costs. Since the trend in wind turbine design is towards larger, more flexible turbines with lower frequency structural modes, manufacturers will want to develop methods to operate in the presence of these modes. Accurate models of the dynamic characteristics of new wind turbines are often not available due to the complexity and expense of the modeling task, making wind turbines ideally suited to adaptive control. In this paper, we develop theory for adaptive control with rejection of disturbances in the presence of modes that inhibit the controller. We use this method to design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed wind turbine operating in Region 3. The objective of the adaptive pitch controller is to regulate generator speed, accommodate wind gusts, and reduce the interference of certain structural modes in feedback. The control objective is accomplished by collectively pitching the turbine blades. The adaptive pitch controller for Region 3 is compared in simulations with a baseline classical Proportional Integrator (PI) collective pitch controller.

Effects of Solar Wind Conditions on the Plasma Wake Within a Polar Crater: Preliminary Results

NASA Technical Reports Server (NTRS)

Zimmerman, M. I.; Farrell, W. M.; Stubbs, T. J.

2011-01-01

As the solar wind sweeps horizontally past a shadowed lunar crater it simultaneously diffuses toward the surface through an ambipolar process, forming a plasma wake (e.g., Figure 1). Importantly, the resulting electric field structure diverts solar wind protons toward the cold crater floor where they may represent a source of surficial hydrogen. We present a handful of two-dimensional kinetic simulations exploring the range of wake structures and surface particle fluxes possible under various background plasma conditions.

Cosmic ray acceleration in magnetic circumstellar bubbles

NASA Astrophysics Data System (ADS)

Zirakashvili, V. N.; Ptuskin, V. S.

2018-03-01

We consider the diffusive shock acceleration in interstellar bubbles created by powerful stellar winds of supernova progenitors. Under the moderate stellar wind magnetization the bubbles are filled by the strongly magnetized low density gas. It is shown that the maximum energy of particles accelerated in this environment can exceed the "knee" energy in the observable cosmic ray spectrum.

Construction of the 40x80 Foot Wind Tunnel at Ames.

NASA Image and Video Library

1943-07-07

Looking South from inside the diffuser of the 40x80 foot wind tunnel at NACA's Ames Research Center. Construction began in late 1941, the mammoth construction task sorely taxing the resources of the new center. Two and a half years later, in dune 1944, the 40 x 80-foot full-scale tunnel went into operation.

Translational diffusion coefficients of volatile compounds in various aqueous solutions at low and subzero temperatures.

PubMed

Covarrubias-Cervantes, Marco; Champion, Dominique; Debeaufort, Frédéric; Voilley, Andrée

2005-08-24

Translational diffusion coefficients (D(12)) of volatile compounds were measured in model media with the profile concentration method. The influence of sample temperature (from 25 to -10 degrees C) was studied on translational diffusion in sucrose or maltodextrin solutions at various concentrations. Results show that diffusivity of volatile compounds in sucrose solutions is controlled by temperature, molecule size, and the viscosity of the liquid phase as expected with the Stokes-Einstein equation; moreover, physicochemical interactions between volatile compounds and the medium are determinant for diffusion estimation. At negative temperature, the winding path induced by an ice crystal content of >70% lowered volatile compound diffusion. On the contrary, no influence on translational diffusion coefficients was observed for lower ice content.

Solar Wind Implantation into Lunar Regolith II: Monte Carlo Simulations of Hydrogen Retention in a Surface with Defects and the Hydrogen (H, H2) Exosphere

NASA Technical Reports Server (NTRS)

Tucker, O. J.; Farrell, W. M.; Killen, R. M.; Hurley, D. M.

2018-01-01

Recently, the near-infrared observations of the OH veneer on the lunar surface by the Moon Mineralogy Mapper (M3) have been refined to constrain the OH content to 500-750 parts per million (ppm). The observations indicate diurnal variations in OH up to 200 ppm possibly linked to warmer surface temperatures at low latitude. We examine the M3 observations using a statistical mechanics approach to model the diffusion of implanted H in the lunar regolith. We present results from Monte Carlo simulations of the diffusion of implanted solar wind H atoms and the subsequently derived H and H2 exospheres.

Lagrangian numerical methods for ocean biogeochemical simulations

NASA Astrophysics Data System (ADS)

Paparella, Francesco; Popolizio, Marina

2018-05-01

We propose two closely-related Lagrangian numerical methods for the simulation of physical processes involving advection, reaction and diffusion. The methods are intended to be used in settings where the flow is nearly incompressible and the Péclet numbers are so high that resolving all the scales of motion is unfeasible. This is commonplace in ocean flows. Our methods consist in augmenting the method of characteristics, which is suitable for advection-reaction problems, with couplings among nearby particles, producing fluxes that mimic diffusion, or unresolved small-scale transport. The methods conserve mass, obey the maximum principle, and allow to tune the strength of the diffusive terms down to zero, while avoiding unwanted numerical dissipation effects.

Potential for wind extraction from 4D-Var assimilation of aerosols and moisture

NASA Astrophysics Data System (ADS)

Zaplotnik, Žiga; Žagar, Nedjeljka

2017-04-01

We discuss the potential of the four-dimensional variational data assimilation (4D-Var) to retrieve the unobserved wind field from observations of atmospheric tracers and the mass field through internal model dynamics and the multivariate relationships in the background-error term for 4D-Var. The presence of non-linear moist dynamics makes the wind retrieval from tracers very difficult. On the other hand, it has been shown that moisture observations strongly influence both tropical and mid-latitude wind field in 4D-Var. We present an intermediate complexity model that describes nonlinear interactions between the wind, temperature, aerosols and moisture including their sinks and sources in the framework of the so-called first baroclinic mode atmosphere envisaged by A. Gill. Aerosol physical processes, which are included in the model, are the non-linear advection, diffusion and sources and sinks that exist as dry and wet deposition and diffusion. Precipitation is parametrized according to the Betts-Miller scheme. The control vector for 4D-Var includes aerosols, moisture and the three dynamical variables. The former is analysed univariately whereas wind field and mass field are analysed in a multivariate fashion taking into account quasi-geostrophic and unbalanced dynamics. The OSSE type of studies are performed for the tropical region to assess the ability of 4D-Var to extract wind-field information from the time series of observations of tracers as a function of the flow nonlinearity, the observations density and the length of the assimilation window (12 hours and 24 hours), in dry and moist environment. Results show that the 4D-Var assimilation of aerosols and temperature data is beneficial for the wind analysis with analysis errors strongly dependent on the moist processes and reliable background-error covariances.

Material transport in a wind and buoyancy forced mixed layer

NASA Astrophysics Data System (ADS)

Mensa, J. A.; Özgökmen, T.; Poje, A. C.; Imberger, J.

2016-02-01

Flows in the upper ocean mixed layer are responsible for the transport and dispersion of biogeochemical tracers, phytoplankton and buoyant pollutants, such as hydrocarbons from an oil spill. Material dispersion in mixed layer flows subject to diurnal buoyancy forcing and weak winds (|u10|=5ms-1) are investigated using a non-hydrostatic model. Both purely buoyancy-forced and combined wind- and buoyancy-forced flows are sampled using passive tracers, as well as 2D and 3D particles to explore characteristics of horizontal and vertical dispersion. It is found that the surface tracer patterns are determined by the convergence zones created by convection cells within a time scale of just a few hours. For pure convection, the results displayed the classic signature of Rayleigh-Benard cells. When combined with a wind stress, the convective cells become anisotropic in that the along-wind length scale gets much larger than the cross-wind scale. Horizontal relative dispersion computed by sampling the flow fields using both 2D and 3D passive particles is found to be consistent with the Richardson regime. Relative dispersion is an order of magnitude higher and 2D surface releases transition to Richardson regime faster in the wind-forced case. We also show that the buoyancy-forced case results in significantly lower amplitudes of scale-dependent horizontal relative diffusivity, kD(l), than those reported by Okubo (1970), while the wind- and buoyancy forced case shows a good agreement with Okubo's diffusivity amplitude, and scaling consistent with Richardson's 4/3rd law, kD(l) l4/3. The modelling results provide a framework for measuring material dispersion by mixed layer flow in future observational programs.

Material transport in a convective surface mixed layer under weak wind forcing

NASA Astrophysics Data System (ADS)

Mensa, Jean A.; Özgökmen, Tamay M.; Poje, Andrew C.; Imberger, Jörg

2015-12-01

Flows in the upper ocean mixed layer are responsible for the transport and dispersion of biogeochemical tracers, phytoplankton and buoyant pollutants, such as hydrocarbons from an oil spill. Material dispersion in mixed layer flows subject to diurnal buoyancy forcing and weak winds (| u10 | = 5m s-1) are investigated using a non-hydrostatic model. Both purely buoyancy-forced and combined wind- and buoyancy-forced flows are sampled using passive tracers, as well as 2D and 3D particles to explore characteristics of horizontal and vertical dispersion. It is found that the surface tracer patterns are determined by the convergence zones created by convection cells within a time scale of just a few hours. For pure convection, the results displayed the classic signature of Rayleigh-Benard cells. When combined with a wind stress, the convective cells become anisotropic in that the along-wind length scale gets much larger than the cross-wind scale. Horizontal relative dispersion computed by sampling the flow fields using both 2D and 3D passive particles is found to be consistent with the Richardson regime. Relative dispersion is an order of magnitude higher and 2D surface releases transition to Richardson regime faster in the wind-forced case. We also show that the buoyancy-forced case results in significantly lower amplitudes of scale-dependent horizontal relative diffusivity, kD(ℓ), than those reported by Okubo (1970), while the wind- and buoyancy-forced case shows a good agreement with Okubo's diffusivity amplitude, and the scaling is consistent with Richardson's 4/3rd law, kD ∼ ℓ4/3. These modeling results provide a framework for measuring material dispersion by mixed layer flows in future observational programs.

Diffusion in coastal and harbour zones, effects of Waves,Wind and Currents

NASA Astrophysics Data System (ADS)

Diez, M.; Redondo, J. M.

2009-04-01

As there are multiple processes at different scales that produce turbulent mixing in the ocean, thus giving a large variation of horizontal eddy diffusivities, we use a direct method to evaluate the influence of different ambient parameters such as wave height and wind on coastal dispersion. Measurements of the diffusivity are made by digital processing of images taken from from video recordings of the sea surface near the coast. The use of image analysis allows to estimate both spatial and temporal characteristics of wave fields, surface circulation and mixing in the surf zone, near Wave breakers and inside Harbours. The study of near-shore dispersion [1], with the added complexity of the interaction between wave fields, longshore currents, turbulence and beach morphology, needs detailed measurements of simple mixing processes to compare the respective influences of forcings at different scales. The measurements include simultaneous time series of waves, currents, wind velocities from the studied area. Cuantitative information from the video images is accomplished using the DigImage video processing system [3], and a frame grabber. The video may be controlled by the computer, allowing, remote control of the processing. Spectral analysis on the images has also used n order to estimate dominant wave periods as well as the dispersion relations of dominant instabilities. The measurements presented here consist mostly on the comarison of difussion coeficients measured by evaluating the spread of blobs of dye (milk) as well as by measuring the separation between different buoys released at the same time. We have used a techniques, developed by Bahia(1997), Diez(1998) and Bezerra(2000)[1-3] to study turbulent diffusion by means of digital processing of images taken from remote sensing and video recordings of the sea surface. The use of image analysis allows to measure variations of several decades in horizontal diffusivity values, the comparison of the diffusivities between different sites is not direct and a good understanding of the dominant mixing processes is needed. There is an increase of diffusivity with wave height but only for large Wave Reynolds numbers. Other important factors are wind speed and tidal currents. The horizontal diffusivity shows a marked anisotropy as a function of wave height and distance from the coast. The measurements were performed under a variety of weather conditions conditional sampling has been used to identify the different influences of the environmental agents on the actual effective horizontal diffusion[4]. [1] Bahia E. (1998) "Un estudio numerico experimental de la dispersion de contaminantes en aguas costeras, PhD Tesis UPC, Barcelona. [2] Bezerra M.O., (2000) "Diffusion de contaminantes en la costa. , PhD Tesis Uni. De Barcelona, Barcelona. [3] Diez M. (1998) "Estudio de la Hidrodinamica de la zona de rompientes mediante el analisis digital de imagenes. Master Thesis, UPC, Barcelona. [4] Artale V., Boffetta G., Celani A., Cencini M. and Vulpiani A., 1997, "Dispersion of passive tracers in closed basins: Beyond the diffusion coefficient", Physics of Fluids, vol 9, pp 3162-1997

Study of the effect of wind speed on evaporation from soil through integrated modeling of the atmospheric boundary layer and shallow subsurface.

PubMed

Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan M; Illangasekare, Tissa

2014-01-01

In an effort to develop methods based on integrating the subsurface to the atmospheric boundary layer to estimate evaporation, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model was tested using experimental data to study the effect of wind speed on evaporation. The model consists of the coupled equations of mass conservation for two-phase flow in porous medium with single-phase flow in the free-flow domain under nonisothermal, nonequilibrium phase change conditions. In this model, the evaporation rate and soil surface temperature and relative humidity at the interface come directly from the integrated model output. To experimentally validate numerical results, we developed a unique test system consisting of a wind tunnel interfaced with a soil tank instrumented with a network of sensors to measure soil-water variables. Results demonstrated that, by using this coupling approach, it is possible to predict the different stages of the drying process with good accuracy. Increasing the wind speed increases the first stage evaporation rate and decreases the transition time between two evaporative stages (soil water flow to vapor diffusion controlled) at low velocity values; then, at high wind speeds the evaporation rate becomes less dependent on the wind speed. On the contrary, the impact of wind speed on second stage evaporation (diffusion-dominant stage) is not significant. We found that the thermal and solute dispersion in free-flow systems has a significant influence on drying processes from porous media and should be taken into account.

Study of the effect of wind speed on evaporation from soil through integrated modeling of the atmospheric boundary layer and shallow subsurface

PubMed Central

Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan M; Illangasekare, Tissa

2014-01-01

In an effort to develop methods based on integrating the subsurface to the atmospheric boundary layer to estimate evaporation, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model was tested using experimental data to study the effect of wind speed on evaporation. The model consists of the coupled equations of mass conservation for two-phase flow in porous medium with single-phase flow in the free-flow domain under nonisothermal, nonequilibrium phase change conditions. In this model, the evaporation rate and soil surface temperature and relative humidity at the interface come directly from the integrated model output. To experimentally validate numerical results, we developed a unique test system consisting of a wind tunnel interfaced with a soil tank instrumented with a network of sensors to measure soil-water variables. Results demonstrated that, by using this coupling approach, it is possible to predict the different stages of the drying process with good accuracy. Increasing the wind speed increases the first stage evaporation rate and decreases the transition time between two evaporative stages (soil water flow to vapor diffusion controlled) at low velocity values; then, at high wind speeds the evaporation rate becomes less dependent on the wind speed. On the contrary, the impact of wind speed on second stage evaporation (diffusion-dominant stage) is not significant. We found that the thermal and solute dispersion in free-flow systems has a significant influence on drying processes from porous media and should be taken into account. PMID:25309005

The effects of vortex structure and vortex translation on the tropical cyclone boundary layer wind field

NASA Astrophysics Data System (ADS)

Williams, Gabriel J.

2015-03-01

The effects of vortex translation and radial vortex structure in the distribution of boundary layer winds in the inner core of mature tropical cyclones are examined using a high-resolution slab model and a multilevel model. It is shown that the structure and magnitude of the wind field (and the corresponding secondary circulation) depends sensitively on the radial gradient of the gradient wind field above the boundary layer. Furthermore, it is shown that vortex translation creates low wave number asymmetries in the wind field that rotate anticyclonically with height. A budget analysis of the steady state wind field for both models was also performed in this study. Although the agradient force drives the evolution of the boundary layer wind field for both models, it is shown that the manner in which the boundary layer flow responds to this force differs between the two model representations. In particular, the inner core boundary layer flow in the slab model is dominated by the effects of horizontal advection and horizontal diffusion, leading to the development of shock structures in the model. Conversely, the inner core boundary layer flow in the multilevel model is primarily influenced by the effects of vertical advection and vertical diffusion, which eliminates shock structures in this model. These results further indicate that special care is required to ensure that qualitative applications from slab models are not unduly affected by the neglect of vertical advection. This article was corrected on 31 MAR 2015. See the end of the full text for details.

Spectral Analysis and Computation of Effective Diffusivities for Steady Random Flows

DTIC Science & Technology

2016-04-28

even in the motion of sea ice floes influenced by winds and ocean currents. The long time, large scale behavior of such systems is equivalent to an...flow plays a key role in many important processes in the global climate system [55] and Earth’s ecosys- tems [14]. Advection of geophysical fluids...HOMOGENIZATION OF THE ADVECTION-DIFFUSION EQUATION The dispersion of a cloud of passive scalars with density φ diffusing with molecular dif- fusivity ε and

Effect of air turbulence on gas transport in soil; comparison of approaches

NASA Astrophysics Data System (ADS)

Pourbakhtiar, Alireza; Papadikis, Konstantinos; Poulsen, Tjalfe; Bridge, Jonathan; Wilkinson, Stephen

2017-04-01

Greenhouse gases are playing the key role in global warming. Soil is a source of greenhouse gases such as methane (CH4). Radon (Rn) which is a radioactive gas can emit form subsurface into the atmosphere and leads to health concerns in urban areas. Temperature, humidity, air pressure and vegetation of soil can affect gas emissions inside soil (Oertel et al., 2016). It's shown in many cases that wind induced fluctuations is an important factor in transport of gas through soil and other porous media. An example is: landfill gas emissions (Poulsen et al., 2001). We applied an experimental equipment for measuring controlled air turbulence on gas transport in soil in relation to the depth of sample. Two approaches for measurement of effect of wind turbulence on gas transport were applied and compared. Experiments were carried out with diffusion of CO2 and air as tracer gases with average vertical wind speeds of 0 to 0.83 m s-1. In approach A, Six different sample thicknesses from 5 to 30 cm were selected and total of 4 different wind conditions with different speed and fluctuations were applied. In approach B, a sample with constant depth was used. Five oxygen sensors were places inside sample at different depths. Total of 111 experiments were carried out. Gas transport is described by advection-dispersion equation. Gas transport is quantified as a dispersion coefficient. Oxygen breakthrough curves as a function of distance to the surface of the sample exposed to wind were derived numerically with an explicit forward time, central space finite-difference based model to evaluate gas transport. We showed that wind turbulence-induced fluctuations is an important factor in gas transport that can increase gas transport with average of 45 times more than molecular diffusion under zero wind condition. Comparison of two strategies for experiments, indicated that, constant deep samples (Approach B) are more reliable for measurement of gas transport under influence of wind turbulence. They are more similar to natural conditions and also the lower layers of soil are affecting the diffusion and dispersion coefficients of soil in the upper layers. Power spectrum density is calculated for all the all wind conditions to determine strength vibration of all the wind speeds and its relation to gas transport. Differential pressure for different wind conditions are measured at two sides of samples. References Oertel, C., Matschullat, J., Zurba, K., Zimmermann, F. & Erasmi, S. 2016. Greenhouse gas emissions from soils—A review. Chemie der Erde - Geochemistry, 76, 327-352. Poulsen, T.G., Christophersen, M., Moldrup, P. & Kjeldsen, P. 2001. Modeling lateral gas transport in soil adjacent to old landfill. Journal of Environmental Engineering (ASCE), 127, 145-153.

Augmented Visual Experience of Simulated Solar Phenomena

NASA Astrophysics Data System (ADS)

Tucker, A. O., IV; Berardino, R. A.; Hahne, D.; Schreurs, B.; Fox, N. J.; Raouafi, N.

2017-12-01

The Parker Solar Probe (PSP) mission will explore the Sun's corona, studying solar wind, flares and coronal mass ejections. The effects of these phenomena can impact the technology that we use in ways that are not readily apparent, including affecting satellite communications and power grids. Determining the structure and dynamics of corona magnetic fields, tracing the flow of energy that heats the corona, and exploring dusty plasma near the Sun to understand its influence on solar wind and energetic particle formation requires a suite of sensors on board the PSP spacecraft that are engineered to observe specific phenomena. Using models of these sensors and simulated observational data, we can visualize what the PSP spacecraft will "see" during its multiple passes around the Sun. Augmented reality (AR) technologies enable convenient user access to massive data sets. We are developing an application that allows users to experience environmental data from the point of view of the PSP spacecraft in AR using the Microsoft HoloLens. Observational data, including imagery, magnetism, temperature, and density are visualized in 4D within the user's immediate environment. Our application provides an educational tool for comprehending the complex relationships of observational data, which aids in our understanding of the Sun.

A high spatial resolution X-ray and Hα study of hot gas in the halos of star-forming disk galaxies -- testing feedback models

NASA Astrophysics Data System (ADS)

Strickland, D. K.; Heckman, T. M.; Colbert, E. J. M.; Hoopes, C. G.; Weaver, K. A.

2002-12-01

We present arcsecond resolution Chandra X-ray and ground-based optical Hα imaging of a sample of ten edge-on star-forming disk galaxies (seven starburst and three ``normal'' spiral galaxies), a sample which covers the full range of star-formation intensity found in disk galaxies. The X-ray observations make use of the unprecented spatial resolution of the Chandra X-ray observatory to robustly remove X-ray emission from point sources, and hence obtain the X-ray properties of the diffuse thermal emission alone. This data has been combined with existing, comparable-resolution, ground-based Hα imaging. We compare these empirically-derived diffuse X-ray properties with various models for the generation of hot gas in the halos of star-forming galaxies: supernova feedback-based models (starburst-driven winds, galactic fountains), cosmologically-motivated accretion of the IGM and AGN-driven winds. SN feedback models best explain the observed diffuse X-ray emission. We then use the data to test basic, but fundamental, aspects of wind and fountain theories, e.g. the critical energy required for disk "break-out." DKS is supported by NASA through Chandra Postdoctoral Fellowship Award Number PF0-10012.

The True Color of Yogi: An Accurate Method for Removing Diffuse Illumination from Multispectral Images of Mars

NASA Technical Reports Server (NTRS)

Stoker, Carol R.; Rages, Kathy

2002-01-01

We correct spectra of Yogi to remove diffuse illumination and show that the part of Yogi facing the wind is less red than other faces of the rock. Our method eliminates ambiguity in interpreting spectra obtained under Mars illumination conditions. Additional information is contained in the original extended abstract.

Tidal influences on vertical diffusion and diurnal variability of ozone in the mesosphere

NASA Technical Reports Server (NTRS)

Bjarnason, Gudmundur G.; Solomon, Susan; Garcia, Rolando R.

1987-01-01

Possible dynamical influences on the diurnal behavior of ozone are investigated. A time dependent one-dimensional photochemical model is developed for this purpose; all model calculations are made at 70 deg N during summer. It is shown that the vertical diffusion can vary as much as 1 order of magnitude within a day as a result of large changes in the zonal wind induced by atmospheric thermal tides. It is found that by introducing a dissipation time scale for turbulence produced by breaking gravity waves, the agreement with Poker Flat echo data is improved. Comparisons of results from photochemical model calculations, where the vertical diffusion is a function of height only, with those in which the vertical diffusion coefficient is changing in time show large differences in the diurnal behavior of ozone between 70 and 90 km. By including the dynamical effect, much better agreement with the Solar Mesosphere Explorers data is obtained. The results are, however, sensitive to the background zonally averaged wind. The influence of including time-varying vertical diffusion coefficient on the OH densities is also large, especially between 80 and 90 km. This suggests that dynamical effects are important in determining the diurnal behavior of the airglow emission from the Meinel bands.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Wind profile recovery from intensity fluctuations of a laser beam reflected in a turbulent atmosphere

NASA Astrophysics Data System (ADS)

Banakh, V. A.; Marakasov, D. A.

2008-04-01

An algorithm for the wind profile recovery from spatiotemporal spectra of a laser beam reflected in a turbulent atmosphere is presented. The cases of a spherical wave incident on a diffuse reflector of finite size and a spatially limited beam reflected from an infinite random surface are considered.

Magnetic pumping of the solar wind

NASA Astrophysics Data System (ADS)

Egedal, Jan; Lichko, Emily; Daughton, William

2015-11-01

The transport of matter and radiation in the solar wind and terrestrial magnetosphere is a complicated problem involving competing processes of charged particles interacting with electric and magnetic fields. Given the rapid expansion of the solar wind, it would be expected that superthermal electrons originating in the corona would cool rapidly as a function of distance to the Sun. However, this is not observed, and various models have been proposed as candidates for heating the solar wind. In the compressional pumping mechanism explored by Fisk and Gloeckler particles are accelerated by random compressions by the interplanetary wave turbulence. This theory explores diffusion due to spatial non-uniformities and provides a mechanism for redistributing particle. For investigation of a related but different heating mechanism, magnetic pumping, in our work we include diffusion of anisotropic features that develops in velocity space. The mechanism allows energy to be transferred to the particles directly from the turbulence. Guided by kinetic simulations a theory is derived for magnetic pumping. At the heart of this work is a generalization of the Parker Equation to capture the role of the pressure anisotropy during the pumping process. Supported by NASA grant NNX15AJ73G.

The formation of rings and gaps in magnetically coupled disc-wind systems: ambipolar diffusion and reconnection

NASA Astrophysics Data System (ADS)

Suriano, Scott S.; Li, Zhi-Yun; Krasnopolsky, Ruben; Shang, Hsien

2018-06-01

Radial substructures in circumstellar discs are now routinely observed by Atacama Large Millimeter/submillimeter Array. There is also growing evidence that disc winds drive accretion in such discs. We show through 2D (axisymmetric) simulations that rings and gaps develop naturally in magnetically coupled disc-wind systems on the scale of tens of au, where ambipolar diffusion (AD) is the dominant non-ideal magnetohydrodynamic effect. In simulations where the magnetic field and matter are moderately coupled, the disc remains relatively laminar with the radial electric current steepened by AD into a thin layer near the mid-plane. The toroidal magnetic field sharply reverses polarity in this layer, generating a large magnetic torque that drives fast accretion, which drags the poloidal field into a highly pinched radial configuration. The reconnection of this pinched field creates magnetic loops where the net poloidal magnetic flux (and thus the accretion rate) is reduced, yielding dense rings. Neighbouring regions with stronger poloidal magnetic fields accrete faster, forming gaps. In better magnetically coupled simulations, the so-called avalanche accretion streams develop continuously near the disc surface, rendering the disc-wind system more chaotic. Nevertheless, prominent rings and gaps are still produced, at least in part, by reconnection, which again enables the segregation of the poloidal field and the disc material similar to the more diffusive discs. However, the reconnection is now driven by the non-linear growth of magnetorotational instability channel flows. The formation of rings and gaps in rapidly accreting yet laminar discs has interesting implications for dust settling and trapping, grain growth, and planet formation.

On the X-ray temperature of hot gas in diffuse nebulae

NASA Astrophysics Data System (ADS)

Toalá, J. A.; Arthur, S. J.

2018-05-01

X-ray emitting diffuse nebulae around hot stars are observed to have soft-band temperatures in the narrow range [1-3]× 106 K, independent of the stellar wind parameters and the evolutionary stage of the central star. We discuss the origin of this X-ray temperature for planetary nebulae (PNe), Wolf-Rayet nebulae (WR) and interstellar wind bubbles around hot young stars in our Galaxy and the Magellanic Clouds. We calculate the differential emission measure (DEM) distributions as a function of temperature from previously published simulations and combine these with the X-ray emission coefficient for the 0.3-2.0 keV band to estimate the X-ray temperatures. We find that all simulated nebulae have DEM distributions with steep negative slopes, which is due to turbulent mixing at the interface between the hot shocked stellar wind and the warm photoionized gas. Sharply peaked emission coefficients act as temperature filters and emphasize the contribution of gas with temperatures close to the peak position, which coincides with the observed X-ray temperatures for the chemical abundance sets we consider. Higher metallicity nebulae have lower temperature and higher luminosity X-ray emission. We show that the second temperature component found from spectral fitting to X-ray observations of WR nebulae is due to a significant contribution from the hot shocked stellar wind, while the lower temperature principal component is dominated by nebular gas. We suggest that turbulent mixing layers are the origin of the soft X-ray emission in the majority of diffuse nebulae.

On the X-ray temperature of hot gas in diffuse nebulae

NASA Astrophysics Data System (ADS)

Toalá, J. A.; Arthur, S. J.

2018-07-01

X-ray-emitting diffuse nebulae around hot stars are observed to have soft-band temperatures in the narrow range [1-3] × 106K, independent of the stellar wind parameters and the evolutionary stage of the central star. We discuss the origin of this X-ray temperature for planetary nebulae, Wolf-Rayet (WR) nebulae, and interstellar wind bubbles around hot young stars in our Galaxy and the Magellanic Clouds. We calculate the differential emission measure (DEM) distributions as a function of temperature from previously published simulations and combine these with the X-ray emission coefficient for the 0.3-2.0 keV band to estimate the X-ray temperatures. We find that all simulated nebulae have DEM distributions with steep negative slopes, which is due to turbulent mixing at the interface between the hot shocked stellar wind and the warm photoionized gas. Sharply peaked emission coefficients act as temperature filters and emphasize the contribution of gas with temperatures close to the peak position, which coincides with the observed X-ray temperatures for the chemical abundance sets we consider. Higher metallicity nebulae have lower temperature and higher luminosity X-ray emission. We show that the second temperature component found from spectral fitting to X-ray observations of WR nebulae is due to a significant contribution from the hot shocked stellar wind, while the lower temperature principal component is dominated by nebular gas. We suggest that turbulent mixing layers are the origin of the soft X-ray emission in the majority of diffuse nebulae.

Heating Augmentation in Laminar Flow Due to Heat-Shield Cavities on the Project Orion CEV

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

2008-01-01

An experimental study has been conducted to assess the effects of compression pad cavities on the aeroheating environment of the Project Orion CEV heat-shield at laminar conditions. Testing was conducted in Mach 6 and Mach 10 perfect-gas wind tunnels to obtain heating measurements on and around the compression pads using global phosphor thermography. Consistent trends in heating augmentation levels were observed in the data and correlations of average and maximum heating at the cavities were formulated in terms of the local boundary-layer parameters and cavity dimensions. Additional heating data from prior testing of Genesis and Mars Science Laboratory models were also examined to extend the parametric range of cavity heating correlations.

Design and test of a prototype scale ejector wing

NASA Technical Reports Server (NTRS)

Mefferd, L. A.; Alden, R. E.; Bevilacqua, P. M.

1979-01-01

A two dimensional momentum integral analysis was used to examine the effect of changing inlet area ratio, diffuser area ratio, and the ratio of ejector length to width. A relatively wide range of these parameters was considered. It was found that for constant inlet area ratio the augmentation increases with the ejector length, and for constant length: width ratio the augmentation increases with inlet area ratio. Scale model tests were used to verify these trends and to examine th effect of aspect ratio. On the basis of these results, an ejector configuration was selected for fabrication and testing at a scale representative of an ejector wing aircraft. The test ejector was powered by a Pratt-Whitney F401 engine developing approximately 12,000 pounds of thrust. The results of preliminary tests indicate that the ejector develops a thrust augmentation ratio better than 1.65.

Stereoscopic augmented reality with pseudo-realistic global illumination effects

NASA Astrophysics Data System (ADS)

de Sorbier, Francois; Saito, Hideo

2014-03-01

Recently, augmented reality has become very popular and has appeared in our daily life with gaming, guiding systems or mobile phone applications. However, inserting object in such a way their appearance seems natural is still an issue, especially in an unknown environment. This paper presents a framework that demonstrates the capabilities of Kinect for convincing augmented reality in an unknown environment. Rather than pre-computing a reconstruction of the scene like proposed by most of the previous method, we propose a dynamic capture of the scene that allows adapting to live changes of the environment. Our approach, based on the update of an environment map, can also detect the position of the light sources. Combining information from the environment map, the light sources and the camera tracking, we can display virtual objects using stereoscopic devices with global illumination effects such as diffuse and mirror reflections, refractions and shadows in real time.

Double-diffusive layers in the Adriatic Sea

NASA Astrophysics Data System (ADS)

Carniel, Sandro; Sclavo, Mauro; Kantha, Lakshmi; Prandke, Hartmut

2008-01-01

A microstructure profiler was deployed to make turbulence measurements in the upper layers of the southern Adriatic Sea in the Mediterranean during the Naval Research Laboratory (NRL) DART06A (Dynamics of the Adriatic in Real Time) winter cruise in March 2006. Measurements in the Po river plume along the Italian coast near the Gargano promontory displayed classic double-diffusive layers and staircase structures resulting from the relatively colder and fresher wintertime Po river outflow water masses overlying warmer and more saline water masses from the Adriatic Sea. We report here on the water mass and turbulence structure measurements made both in the double-diffusive interfaces and the adjoining mixed layers in the water columns undergoing double-diffusive convection (DDC). This dataset augments the relatively sparse observations available hitherto on the diffusive layer type of DDC. Measured turbulence diffusivities are consistent with those from earlier theoretical and experimental formulations, suggesting that the wintertime Po river plume is a convenient and easily accessible place to study double diffusive convective processes of importance to mixing in the interior of many regions of the global oceans.

Study of controlled diffusion stator blading. 1. Aerodynamic and mechanical design report

NASA Technical Reports Server (NTRS)

Canal, E.; Chisholm, B. C.; Lee, D.; Spear, D. A.

1981-01-01

Pratt & Whitney Aircraft is conducting a test program for NASA in order to demonstrate that a controlled-diffusion stator provides low losses at high loadings and Mach numbers. The technology has shown great promise in wind tunnel tests. Details of the design of the controlled diffusion stator vanes and the multiple-circular-arc rotor blades are presented. The stage, including stator and rotor, was designed to be suitable for the first-stage of an advanced multistage, high-pressure compressor.

Turbulent diffusion with memories and intrinsic shear

NASA Technical Reports Server (NTRS)

Tchen, C. M.

1974-01-01

The first part of the present theory is devoted to the derivation of a Fokker-Planck equation. The eddies smaller than the hydrodynamic scale of the diffusion cloud form a diffusivity, while the inhomogeneous, bigger eddies give rise to a nonuniform migratory drift. This introduces an eddy-induced shear which reflects on the large-scale diffusion. The eddy-induced shear does not require the presence of a permanent wind shear and is intrinsic to the diffusion. Secondly, a transport theory of diffusivity is developed by the method of repeated-cascade and is based upon a relaxation of a chain of memories with decreasing information. The full range of diffusion consists of inertia, composite, and shear subranges, for which variance and eddy diffusivities are predicted. The coefficients are evaluated. Comparison with experiments in the upper atmosphere and oceans is made.

Wind direction variability in Afternoon and Sunset Turbulence

NASA Astrophysics Data System (ADS)

Nilsson, Erik; Lothon, Marie; Lohou, Fabienne; Mahrt, Larry

2014-05-01

Understanding wind direction (WD) variability better is important for several reasons. Air pollution models need information about how variable wind direction is in different conditions (Davies and Thomson 1999). Accurate predictions of dispersion are important for human health and safety and allow for adaptation planning (Nagle et al. 2011). Other applications include horizontal diffusion, efficiency and fatigue of wind machines and air-sea interaction (Mahrt 2011). Most studies of wind direction variability have focused on nocturnal conditions because of greater variability in light winds. Modelling WD variability in transition periods when both mean wind speed and variance of the wind components are in a state of change can, however, also be very challenging and has not been the focus of earlier studies. The evening transitioning to the nocturnal boundary layer can play an important role in the diffusion process of pollutants and scalars emitted at surface and transported within the atmosphere. The Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign that took place in southern France in June and July 2011 focused on the decaying turbulence of the late afternoon boundary layer and related issues (Lothon et al. 2012). We analyse field measurements from BLLAST to investigate WD variability in the evening transition period. Standard deviations of horizontal wind direction fluctuations in the lowest 60 m of the boundary layer have been examined for dependence on mean wind speed, higher order moments and averaging time. Measurement results are interpreted using measured and idealized probability density functions of horizontal wind vectors. These are also used to develop analytical functions describing how WD variability depends on wind speed, variance and other controlling factors in the atmospheric boundary layer. References: Davies B.M., Thomson D.J., 1999. Comparison of some parameterizations of wind direction variability with observations, Atmospheric Enviroment 33, 4909-4917. Lothon M. et al., 2012. The Boundary-Layer Late Afternoon and Sunset Turbulence field experiment, Proc. of the 20th Symposium on Boundary-Layers and Turbulence, 7-13 July, Boston, MA, USA. Mahrt L., 2011. Surface Wind Direction Variability, Journal of Applied Meteorology and Climatology 50. 144-152. Nagle J.C., 2011. Adapting to Pollution, Research Roundtable on Climate Change, Adaptation, and Enviromental Law, Northwestern Law Searle Center, Legal and Regulatory Studies 7-18 April, IL, USA.

Study of aerodynamic technology for VSTOL fighter/attack aircraft, phase 1

NASA Technical Reports Server (NTRS)

Driggers, H. H.

1978-01-01

A conceptual design study was performed of a vertical attitude takeoff and landing (VATOL) fighter/attack aircraft. The configuration has a close-coupled canard-delta wing, side two-dimensional ramp inlets, and two augmented turbofan engines with thrust vectoring capability. Performance and sensitivities to objective requirements were calculated. Aerodynamic characteristics were estimated based on contractor and NASA wind tunnel data. Computer simulations of VATOL transitions were performed. Successful transitions can be made, even with series post-stall instabilities, if reaction controls are properly phased. Principal aerodynamic uncertainties identified were post-stall aerodynamics, transonic aerodynamics with thrust vectoring and inlet performance in VATOL transition. A wind tunnel research program was recommended to resolve the aerodynamic uncertainties.

Characteristics of the Langley 8-foot Transonic Tunnel with Slotted Test Section

NASA Technical Reports Server (NTRS)

Wright, Ray H; Ritchie, Virgil S; Pearson, Albin O

1958-01-01

A large wind tunnel, approximately 8 feet in diameter, has been converted to transonic operation by means of slots in the boundary extending in the direction of flow. The usefulness of such a slotted wind tunnel, already known with respect to the reduction of the subsonic blockage interference and the production of continuously variable supersonic flows, has been augmented by devising a slot shape with which a supersonic test region with excellent flow quality could be produced. Experimental locations of detached shock waves ahead of axially symmetric bodies at low supersonic speeds in the slotted test section agreed satisfactorily with predictions obtained by use of existing approximate methods.

Diffusion-plus-drift models for the mass leakage from centrifugal magnetospheres of magnetic hot-stars

NASA Astrophysics Data System (ADS)

Owocki, Stanley P.; Cranmer, Steven R.

2018-03-01

In the subset of luminous, early-type stars with strong, large-scale magnetic fields and moderate to rapid rotation, material from the star's radiatively driven stellar wind outflow becomes trapped by closed magnetic loops, forming a centrifugally supported, corotating magnetosphere. We present here a semi-analytic analysis of how this quasi-steady accumulation of wind mass can be balanced by losses associated with a combination of an outward, centrifugally driven drift in the region beyond the Kepler co-rotation radius, and an inward/outward diffusion near this radius. We thereby derive scaling relations for the equilibrium spatial distribution of mass, and the associated emission measure for observational diagnostics like Balmer line emission. We discuss the potential application of these relations for interpreting surveys of the emission line diagnostics for OB stars with centrifugally supported magnetospheres. For a specific model of turbulent field-line-wandering rooted in surface motions associated with the iron opacity bump, we estimate values for the associated diffusion and drift coefficients.

Ducted turbine theory with right angled ducts

NASA Astrophysics Data System (ADS)

McLaren-Gow, S.; Jamieson, P.; Graham, J. M. R.

2014-06-01

This paper describes the use of an inviscid approach to model a ducted turbine - also known as a diffuser augmented turbine - and a comparison of results with a particular one-dimensional theory. The aim of the investigation was to gain a better understanding of the relationship between a real duct and the ideal diffuser, which is a concept that is developed in the theory. A range of right angled ducts, which have a rim for a 90° exit angle, were modelled. As a result, the performance of right angled ducts has been characterised in inviscid flow. It was concluded that right angled ducts cannot match the performance of their associated ideal diffuser and that the optimum rotor loading for these turbines varies with the duct dimensions.

On turbulent diffusion of magnetic fields and the loss of magnetic flux from stars

NASA Technical Reports Server (NTRS)

Vainshtein, Samuel I.; Rosner, Robert

1991-01-01

The turbulent diffusion of magnetic fields in astrophysical objects, and the processes leading to magnetic field flux loss from such objects are discussed with attention to the suppression of turbulent diffusion by back-reaction of magnetic fields on small spatial scales, and on the constraint imposed on magnetic flux loss by flux-freezing within stars. Turbulent magnetic diffusion can be suppressed even for very weak large-scale magnetic fields, so that 'standard' turbulent diffusion is incapable of significant magnetic flux destruction within a star. Finally, magnetic flux loss via winds is shown to be generally ineffective, no matter what the value of the effective magnetic Reynolds number is.

Stellar Wind Retention and Expulsion in Massive Star Clusters

NASA Astrophysics Data System (ADS)

Naiman, J. P.; Ramirez-Ruiz, E.; Lin, D. N. C.

2018-05-01

Mass and energy injection throughout the lifetime of a star cluster contributes to the gas reservoir available for subsequent episodes of star formation and the feedback energy budget responsible for ejecting material from the cluster. In addition, mass processed in stellar interiors and ejected as winds has the potential to augment the abundance ratios of currently forming stars, or stars which form at a later time from a retained gas reservoir. Here we present hydrodynamical simulations that explore a wide range of cluster masses, compactnesses, metallicities and stellar population age combinations in order to determine the range of parameter space conducive to stellar wind retention or wind powered gas expulsion in star clusters. We discuss the effects of the stellar wind prescription on retention and expulsion effectiveness, using MESA stellar evolutionary models as a test bed for exploring how the amounts of wind retention/expulsion depend upon the amount of mixing between the winds from stars of different masses and ages. We conclude by summarizing some implications for gas retention and expulsion in a variety of compact (σv ≳ 20 kms-1) star clusters including young massive star clusters (105 ≲ M/M⊙ ≲ 107, age ≲ 500 Myrs), intermediate age clusters (105 ≲ M/M⊙ ≲ 107, age ≈ 1 - 4 Gyrs), and globular clusters (105 ≲ M/M⊙ ≲ 107, age ≳ 10 Gyrs).

Cosmic Ray Acceleration by a Versatile Family of Galactic Wind Termination Shocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bustard, Chad; Zweibel, Ellen G.; Cotter, Cory, E-mail: bustard@wisc.edu

2017-01-20

There are two distinct breaks in the cosmic ray (CR) spectrum: the so-called “knee” around 3 × 10{sup 15} eV and the so-called “ankle” around 10{sup 18} eV. Diffusive shock acceleration (DSA) at supernova remnant (SNR) shock fronts is thought to accelerate galactic CRs to energies below the knee, while an extragalactic origin is presumed for CRs with energies beyond the ankle. CRs with energies between 3 × 10{sup 15} and 10{sup 18} eV, which we dub the “shin,” have an unknown origin. It has been proposed that DSA at galactic wind termination shocks, rather than at SNR shocks, maymore » accelerate CRs to these energies. This paper uses the galactic wind model of Bustard et al. to analyze whether galactic wind termination shocks may accelerate CRs to shin energies within a reasonable acceleration time and whether such CRs can subsequently diffuse back to the Galaxy. We argue for acceleration times on the order of 100 Myr rather than a few billion years, as assumed in some previous works, and we discuss prospects for magnetic field amplification at the shock front. Ultimately, we generously assume that the magnetic field is amplified to equipartition. This formalism allows us to obtain analytic formulae, applicable to any wind model, for CR acceleration. Even with generous assumptions, we find that very high wind velocities are required to set up the necessary conditions for acceleration beyond 10{sup 17} eV. We also estimate the luminosities of CRs accelerated by outflow termination shocks, including estimates for the Milky Way wind.« less

Super-Eddington stellar winds: unifying radiative-enthalpy versus flux-driven models

NASA Astrophysics Data System (ADS)

Owocki, Stanley P.; Townsend, Richard H. D.; Quataert, Eliot

2017-12-01

We derive semi-analytic solutions for optically thick, super-Eddington stellar winds, induced by an assumed steady energy addition Δ {\\dot{E}} concentrated around a near-surface heating radius R in a massive star of central luminosity L*. We show that obtaining steady wind solutions requires both that the resulting total luminosity L_o = L_\\ast + Δ {\\dot{E}} exceed the Eddington luminosity, Γo ≡ Lo/LEdd > 1, and that the induced mass-loss rate be such that the 'photon-tiring' parameter, m ≡ {\\dot{M}} GM/R L_o ≤ 1-1/Γ _o, ensuring the luminosity is sufficient to overcome the gravitational potential GM/R. Our analysis unifies previous super-Eddington wind models that either: (1) assumed a direct radiative flux-driving without accounting for the advection of radiative enthalpy that can become important in such an optically thick flow; or (2) assumed that such super-Eddington outflows are adiabatic, neglecting the effects of the diffusive radiative flux. We show that these distinct models become applicable in the asymptotic limits of small versus large values of mΓo, respectively. By solving the coupled differential equations for radiative diffusion and wind momentum, we obtain general solutions that effectively bridge the behaviours of these limiting models. Two key scaling results are for the terminal wind speed to escape speed, which is found to vary as v_∞^2/v_esc^2 = Γ _o/(1+m Γ _o) -1, and for the final observed luminosity Lobs, which for all allowed steady-solutions with m < 1 - 1/Γo exceeds the Eddington luminosity, Lobs > LEdd. Our super-Eddington wind solutions have potential applicability for modelling phases of eruptive mass-loss from massive stars, classical novae, and the remnants of stellar mergers.

Experimental study of thin film sensor networks for wind turbine blade damage detection

NASA Astrophysics Data System (ADS)

Downey, A.; Laflamme, S.; Ubertini, F.; Sauder, H.; Sarkar, P.

2017-02-01

Damage detection of wind turbine blades is difficult due to their complex geometry and large size, for which large deployment of sensing systems is typically not economical. A solution is to develop and deploy dedicated sensor networks fabricated from inexpensive materials and electronics. The authors have recently developed a novel skin-type strain gauge for measuring strain over very large surfaces. The skin, a type of large-area electronics, is constituted from a network of soft elastomeric capacitors. The sensing system is analogous to a biological skin, where local strain can be monitored over a global area. In this paper, we propose the utilization of a dense network of soft elastomeric capacitors to detect, localize, and quantify damage on wind turbine blades. We also leverage mature off-the-shelf technologies, in particular resistive strain gauges, to augment such dense sensor network with high accuracy data at key locations, therefore constituting a hybrid dense sensor network. The proposed hybrid dense sensor network is installed inside a wind turbine blade model, and tested in a wind tunnel to simulate an operational environment. Results demonstrate the ability of the hybrid dense sensor network to detect, localize, and quantify damage.

Molecular Diagnostics of Diffusive Boundary Layers

NASA Astrophysics Data System (ADS)

Rawlings, J. M. C.; Hartquist, T. W.

1997-10-01

We have examined the chemistry in thin (<~0.01 pc) boundary layers between dark star-forming cores and warm, shocked T Tauri winds on the assumption that turbulence-driven diffusion occurs within them. The results indicate that emissions from C+, CH, OH, H2O and the J = 6 --> 5 transition of CO, among others, may serve as diagnostics of the boundary layers.

Evolution and Growth Competition of Salt Fingers in Saline Lake with Slight Wind Shear

NASA Astrophysics Data System (ADS)

Yang, Ray-Yeng; Hwung, Hwung-Hweng; Shugan, Igor

2010-05-01

Since the discover of double-diffusive convection by Stommel, Arons & Blanchard (1956), 'evidence has accumulated for the widespread presence of double-diffusion throughout the ocean' and for its 'significant effects on global water-mass structure and the thermohaline convection' (Schmitt, 1998). The salt-fingering form of double-diffusion has particularly attracted interest because of salt-finger convection being now widely recognized as an important mechanism for mixing heat and salt both vertically and laterally in the ocean and saline lake. In oceanographic situations or saline lake where salt fingers may be an important mechanism for the transport of heat and salt in the vertical, velocity shears may also be present. Salt finger convection is analogous to Bénard convection in that the kinetic energy of the motions is obtained from the potential energy stored in the unstable distribution of a stratifying component. On the basis of the thermal analogy it is of interest to discover whether salt fingers are converted into two-dimensional sheets by the wind shear, and how the vertical fluxes of heat and salt are changed by the wind shear. Salt finger convection under the effect of steady wind shear is theoretically examined in this paper. The evolution of developing in the presence of a vertical density gradient disturbance and the horizontal Couette flow is considered near the onset of salt fingers in the saline lake under a moderate rate of wind shear. We use velocity as the basic variable and solve the pressure Poisson equation in terms of the associated Green function. Growth competition between the longitudinal rolls (LR) and the transverse rolls (TR), whose axes are respectively in the direction parallel to and perpendicular to the Couette flow, is investigated by the weakly nonlinear analysis of coupled-mode equations. The results show that the TR mode is characterized in some range of the effective Rayleigh number, and that the stability is dominated by the LR mode in the system. KEY WORDS: evolution, saline lake, salt finger convection, wind shear, growth competition, longitudinal rolls, transverse rolls, coupled-mode equations.

The role of government in the development and diffusion of renewable energy technologies: Wind power in the United States, California, Denmark and Germany, 1970--2000

NASA Astrophysics Data System (ADS)

Sawin, Janet Laughlin

2001-07-01

This dissertation seeks to determine the role of government policy in advancing the development and diffusion of renewable energy technologies, and to determine if specific policies or policy types are more effective than others in achieving these ends. This study analyzes legislation, regulations, research and development (R&D) programs and their impacts on wind energy in California, the rest of the United States, Denmark and Germany, from 1970 through 2000. These countries (and state) were chosen because each has followed a very different path and has adopted wind energy at different rates. Demand for energy, particularly electricity, is rising rapidly worldwide. Renewable energy technologies could meet much of the world's future demand for electricity without the national security, environmental and social costs of conventional technologies. But renewables now play only a minor role in the electric generation systems of most countries. According to conventional economic theory, renewable energy will achieve greater market penetration once it is cost-competitive with conventional generation. This dissertation concludes, however, that government policy is the most significant causal variable in determining the development and diffusion of wind energy technology. Policy is more important for bringing wind energy to maturity than a nation's wind resource potential, wealth, relative differences in electricity prices, or existing infrastructure. Further, policy is essential for enabling a technology to succeed in the marketplace once it is cost-competitive. Policies can affect a technology's perceived, or real, costs; they can reduce risks or increase the availability and affordability of capital; appropriate and consistent policies can eliminate barriers to wind technology. To be adopted on a large scale, renewables require effective, appropriate and, above all, consistent policies that are legislated with a long-term view toward advancing a technology and an industry. Inconsistent policy is economically costly and creates cycles of boom and bust, making it impossible to build a strong domestic industry. To be effective, policy must place priority on demand creation rather than government R&D; it must create a market, establish turbine standards and siting criteria, require data collection and dissemination, facilitate grid access, establish price guarantees, and enable stakeholder participation.

Wind-US Flow Calculations for the M2129 S-Duct Using Structured and Unstructured Grids

NASA Technical Reports Server (NTRS)

Mohler, Stanley R., Jr.

2003-01-01

Computational Fluid Dynamics (CFD) flow solutions for the M2129 diffusing S-duct with and without vane effectors were computed by the Wind-US flow solver. Both structured and unstructured 3-D grids were used. Without vane effectors, the duct exhibited massive flow separation in both experiment and CFD. With vane effectors installed, the flow remained attached and aerodynamic losses were reduced. Total pressure recovery and distortion near the duct outlet were computed from the solutions and compared favorably to experimental values. These calculations are part of a validation effort for the Wind-US code. They also provide an example case to aid engineers in learning to use the Wind-US software.

Constraints on Wave Drag Parameterization Schemes for Simulating the Quasi-Biennial Oscillation. Part I: Gravity Wave Forcing.

NASA Astrophysics Data System (ADS)

Campbell, Lucy J.; Shepherd, Theodore G.

2005-12-01

Parameterization schemes for the drag due to atmospheric gravity waves are discussed and compared in the context of a simple one-dimensional model of the quasi-biennial oscillation (QBO). A number of fundamental issues are examined in detail, with the goal of providing a better understanding of the mechanism by which gravity wave drag can produce an equatorial zonal wind oscillation. The gravity wave driven QBOs are compared with those obtained from a parameterization of equatorial planetary waves. In all gravity wave cases, it is seen that the inclusion of vertical diffusion is crucial for the descent of the shear zones and the development of the QBO. An important difference between the schemes for the two types of waves is that in the case of equatorial planetary waves, vertical diffusion is needed only at the lowest levels, while for the gravity wave drag schemes it must be included at all levels. The question of whether there is downward propagation of influence in the simulated QBOs is addressed. In the gravity wave drag schemes, the evolution of the wind at a given level depends on the wind above, as well as on the wind below. This is in contrast to the parameterization for the equatorial planetary waves in which there is downward propagation of phase only. The stability of a zero-wind initial state is examined, and it is determined that a small perturbation to such a state will amplify with time to the extent that a zonal wind oscillation is permitted.

Net energy payback and CO2 emissions from three midwestern wind farms: An update

USGS Publications Warehouse

White, S.W.

2006-01-01

This paper updates a life-cycle net energy analysis and carbon dioxide emissions analysis of three Midwestern utility-scale wind systems. Both the Energy Payback Ratio (EPR) and CO2 analysis results provide useful data for policy discussions regarding an efficient and low-carbon energy mix. The EPR is the amount of electrical energy produced for the lifetime of the power plant divided by the total amount of energy required to procure and transport the materials, build, operate, and decommission the power plants. The CO2 analysis for each power plant was calculated from the life-cycle energy input data. A previous study also analyzed coal and nuclear fission power plants. At the time of that study, two of the three wind systems had less than a full year of generation data to project the life-cycle energy production. This study updates the analysis of three wind systems with an additional four to eight years of operating data. The EPR for the utility-scale wind systems ranges from a low of 11 for a two-turbine system in Wisconsin to 28 for a 143-turbine system in southwestern Minnesota. The EPR is 11 for coal, 25 for fission with gas centrifuge enriched uranium and 7 for gaseous diffusion enriched uranium. The normalized CO2 emissions, in tonnes of CO2 per GW eh, ranges from 14 to 33 for the wind systems, 974 for coal, and 10 and 34 for nuclear fission using gas centrifuge and gaseous diffusion enriched uranium, respectively. ?? Springer Science+Business Media, LLC 2007.

Molecular Diagnostics of Diffusive Boundary Layers

NASA Astrophysics Data System (ADS)

Rawlings, J. M. C.; Hartquist, T. W.

1995-11-01

We have assessed the role of diffusion in determining chemical abundances in molecular interface regions. Chemical models have been developed which include the appropriate diffusion terms and that are appropriate to a narrow diffusion region (˜0.01pc) that may exist at the interface between a dark core and a hot, shocked T-Tauri wind. We have assumed pressure balance throughout and have calculated the chemical abundances as functions of time and position through the interface. The results show that significant enhancements of detectable molecules/transitions are expected (e.g. CO J=6→5, OH and CH). Using a realistic value of the diffusion coefficient a diffusive region of dimension 0.01pc may be established within about 104 years. In general it seems likely that diffusion processes are highly significant on these and smaller lengthscales.

Cylindrical diffuser performance using a truncated plug nozzle

NASA Technical Reports Server (NTRS)

Galanga, F. L.; Mueller, T. J.

1976-01-01

Cylindrical diffuser performance for a truncated plug nozzle without external flow was tested in a blowdown wind tunnel. The nozzle was designed for an exit Mach number of 1.9 and the plug was conical in shape from the throat and converged to the axis of symmetry at an angle of 10 degrees. The diffuser section was fashioned into two 13.97 cm lengths to facilitate boring of the duct diameter and to allow for testing of two different duct lengths. A slotted hypotube was installed in the base of the diffuser to measure pressure distribution down the centerline of the diffuser. The data obtained included: the typical centerline and sidewall pressure ratio variation along the diffuser, cell pressure ratio vs overall pressure ratio for long and short diffusers and a comparison of minimum experimental cell pressure ratio vs area ratio.

Evaluation of candidate working fluid formulations for the electrothermal-chemical wind tunnel

NASA Technical Reports Server (NTRS)

Akyurtlu, Jale F.; Akyurtlu, Ates

1993-01-01

A new hypersonic test facility which can simulate conditions typical of atmospheric flight at Mach numbers up to 20 is currently under study at the NASA/LaRC Hypersonic Propulsion Branch. In the proposed research, it was suggested that a combustion augmented electrothermal wind tunnel concept may be applied to the planned hypersonic testing facility. The purpose of the current investigation is to evaluate some candidate working fluid formulations which may be used in the chemical-electrothermal wind. The efforts in the initial phase of this research were concentrated on acquiring the code used by GASL to model the electrothermal wind tunnel and testing it using the conditions of GASL simulation. The early version of the general chemical kinetics code (GCKP84) was obtained from NASA and the latest updated version of the code (LSENS) was obtained from the author Dr. Bittker. Both codes are installed on a personal computer with a 486 25 MHz processor and 16 Mbyte RAM. Since the available memory was not sufficient to debug LSENS, for the current work GCKP84 was used.

Special relativity effects for space-based coherent lidar experiments

NASA Technical Reports Server (NTRS)

Raogudimetla, V. S.

1994-01-01

There is a great need to develop a system that can measure accurately atmospheric wind profiles because an accurate data of wind profiles in the atmosphere constitutes single most input for reliable simulations of global climate numerical methods. Also such data helps us understand atmospheric circulation and climate dynamics better. Because of this need for accurate wind measurements, a space-based Laser Atmospheric Winds Sounder (LAWS) is being designed at MSFC to measure wind profiles in the lower atmosphere of the earth with an accuracy of 1 m/s at lower altitudes to 5m/s at higher altitudes. This system uses an orbiting spacecraft with a pulsed laser source and measures the Doppler shift between the transmitted and received frequencies to estimate the atmospheric wind velocities. If a significant return from the ground (sea) is possible, the spacecraft speed and height are estimated from it and these results and the Doppler shift are then used to estimate the wind velocities in the atmosphere. It is expected that at the proposed wavelengths, there will be enough backscatter from the aerosols but there may no be significant return from the ground. So a coherent (heterodyne) detection system is being proposed for signal processing because it can provide high signal to noise ratio and sensitivity and thus make the best use of low ground return. However, for a heterodyne detection scheme to provide the best results, it is important that the receiving aperture be aligned properly for the proposed wind sounder, this amounts to only a few microradians tolerance in alignment. It is suspected that the satellite motion relative to the ground may introduce errors in the order of a few microradians because of special relativity. Hence, the problem of laser scattering off a moving fixed target when the source and receiver are moving, which was not treated in the past in the literature, was analyzed in the following, using relativistic electrodynamics and applied to the case of the space-based coherent lidar, assuming flat ground. Here an interest in developing analytical expression for the location of the receiving point for the return with respect to the satellite, receiving angle and Doppler shift in frequency and amount of tip, all as measured in the satellite moving coordinate system and the diffuse scattering angle at the ground which does not require any compensation. All the three cases of retro-reflection, specular reflection and diffuse scattering by the ground should be treated though retro-reflection and diffuse scattering are more important.

Surface wind mixing in the Regional Ocean Modeling System (ROMS)

NASA Astrophysics Data System (ADS)

Robertson, Robin; Hartlipp, Paul

2017-12-01

Mixing at the ocean surface is key for atmosphere-ocean interactions and the distribution of heat, energy, and gases in the upper ocean. Winds are the primary force for surface mixing. To properly simulate upper ocean dynamics and the flux of these quantities within the upper ocean, models must reproduce mixing in the upper ocean. To evaluate the performance of the Regional Ocean Modeling System (ROMS) in replicating the surface mixing, the results of four different vertical mixing parameterizations were compared against observations, using the surface mixed layer depth, the temperature fields, and observed diffusivities for comparisons. The vertical mixing parameterizations investigated were Mellor- Yamada 2.5 level turbulent closure (MY), Large- McWilliams- Doney Kpp (LMD), Nakanishi- Niino (NN), and the generic length scale (GLS) schemes. This was done for one temperate site in deep water in the Eastern Pacific and three shallow water sites in the Baltic Sea. The model reproduced the surface mixed layer depth reasonably well for all sites; however, the temperature fields were reproduced well for the deep site, but not for the shallow Baltic Sea sites. In the Baltic Sea, the models overmixed the water column after a few days. Vertical temperature diffusivities were higher than those observed and did not show the temporal fluctuations present in the observations. The best performance was by NN and MY; however, MY became unstable in two of the shallow simulations with high winds. The performance of GLS nearly as good as NN and MY. LMD had the poorest performance as it generated temperature diffusivities that were too high and induced too much mixing. Further observational comparisons are needed to evaluate the effects of different stratification and wind conditions and the limitations on the vertical mixing parameterizations.

Model structure of a cosmic-ray mediated stellar or solar wind

NASA Technical Reports Server (NTRS)

Lee, M. A.; Axford, W. I.

1988-01-01

An idealized hydrodynamic model is presented for the mediation of a free-streaming stellar wind by galactic cosmic rays or energetic particles accelerated at the stellar wind termination shock. The spherically-symmetric stellar wind is taken to be cold; the only body force is the cosmic ray pressure gradient. The cosmic rays are treated as a massless fluid with an effective mean diffusion coefficient k proportional to radial distance r. The structure of the governing equations is investigated both analytically and numerically. Solutions for a range of values of k are presented which describe the deceleration of the stellar wind and a transition to nearly incompressible flow and constant cosmic ray pressure at large r. In the limit of small k the transition steepens to a strong stellar wind termination shock. For large k the stellar wind is decelerated gradually with no shock transition. It is argued that the solutions provide a simple model for the mediation of the solar wind by interstellar ions as both pickup ions and the cosmic ray anomalous component which together dominate the pressure of the solar wind at large r.

NACA Conference on Turbojet-Engine Thrust-Augmentation Research - a Compilation of the Papers Presented by NACA Staff Members

DTIC Science & Technology

1948-10-28

N . E. Harvey, Lt. Col. J. A. Hartman, E. P. Hildestad, H. L. Eolbrook, G. E, Hopkins, Lt. Comdr. L. A...velocity and diffuser efficiency on augmentation. 1041A H oo \\=> K H n w E-i O 33 1.6 1.4 E-i co !=> Pi E-i § 1.0 o 1.2 .8...xutm E"H N 1 DO E-i O £3 E-i DO £) E-H o ^ 00 :=> ex E-t Co o Is i.5 i.O .5 :.0 ,5 2 - 750 40G <C < CD-1 T Q lg 3800°

Low Drag Airfoil Design Utilizing Passive Laminar Flow and Coupled Diffusion Control Techniques.

DTIC Science & Technology

1980-09-01

number and real flow environment Influence on transition are pre- sented. Examination of wind tunnel scaling Influences and real flow environ- ment...effects on the ATC/lamlnar airfoil performance are discussed and summarized for typical low turbulence tunnels ,(e.g., the NASA-Ames 12 foot pressure tunnel ...35 5.0 WIND TUNNEL VALIDATION ASSESSMENT --------------------- 42 5.1 TEST FACILITY EVALUATION ------------------------- 42 5.2

A nonlinear equation for ionic diffusion in a strong binary electrolyte

PubMed Central

Ghosal, Sandip; Chen, Zhen

2010-01-01

The problem of the one-dimensional electro-diffusion of ions in a strong binary electrolyte is considered. The mathematical description, known as the Poisson–Nernst–Planck (PNP) system, consists of a diffusion equation for each species augmented by transport owing to a self-consistent electrostatic field determined by the Poisson equation. This description is also relevant to other important problems in physics, such as electron and hole diffusion across semiconductor junctions and the diffusion of ions in plasmas. If concentrations do not vary appreciably over distances of the order of the Debye length, the Poisson equation can be replaced by the condition of local charge neutrality first introduced by Planck. It can then be shown that both species diffuse at the same rate with a common diffusivity that is intermediate between that of the slow and fast species (ambipolar diffusion). Here, we derive a more general theory by exploiting the ratio of the Debye length to a characteristic length scale as a small asymptotic parameter. It is shown that the concentration of either species may be described by a nonlinear partial differential equation that provides a better approximation than the classical linear equation for ambipolar diffusion, but reduces to it in the appropriate limit. PMID:21818176

Solar Wind Strahl Broadening by Self-Generated Plasma Waves

NASA Technical Reports Server (NTRS)

Pavan, J.; Vinas, A. F.; Yoon, P. H.; Ziebell, L. F.; Gaelzer, R.

2013-01-01

This Letter reports on the results of numerical simulations which may provide a possible explanation for the strahl broadening during quiet solar conditions. The relevant processes involved in the broadening are due to kinetic quasi-linear wave-particle interaction. Making use of static analytical electron distribution in an inhomogeneous field, it is found that self-generated electrostatic waves at the plasma frequency, i.e., Langmuir waves, are capable of scattering the strahl component, resulting in energy and pitch-angle diffusion that broadens its velocity distribution significantly. The present theoretical results provide an alternative or complementary explanation to the usual whistler diffusion scenario, suggesting that self-induced electrostatic waves at the plasma frequency might play a key role in broadening the solar wind strahl during quiet solar conditions.

Solar wind physics

NASA Technical Reports Server (NTRS)

1972-01-01

A double-chambered gas proportional counter was constructed to detect and identify solar wind ions after acceleration by a high voltage power supply. It was determined that the best method of detecting deuterium in the solar wind is to use a tritium target as proposed for IMP H and J. The feasibility of detecting H(+) and He(+) ions of interstellar origin is considered. A program is described to carry out ground-based astronomical observations of faint, diffuse optical emission lines from interstellar gas. Hydrogen and oxygen emission lines from galactic sources were detected and the galactic and geocoronal H alpha and beta lines were clearly resolved.

Peak-locking error reduction by birefringent optical diffusers

NASA Astrophysics Data System (ADS)

Kislaya, Ankur; Sciacchitano, Andrea

2018-02-01

The use of optical diffusers for the reduction of peak-locking errors in particle image velocimetry is investigated. The working principle of the optical diffusers is based on the concept of birefringence, where the incoming rays are subject to different deflections depending on the light direction and polarization. The performances of the diffusers are assessed via wind tunnel measurements in uniform flow and wall-bounded turbulence. Comparison with best-practice image defocusing is also conducted. It is found that the optical diffusers yield an increase of the particle image diameter up to 10 µm in the sensor plane. Comparison with reference measurements showed a reduction of both random and systematic errors by a factor of 3, even at low imaging signal-to-noise ratio.

Disentangling X-Ray Emission Processes in Vela-Like Pulsars

NASA Technical Reports Server (NTRS)

Gaensler, Bryan; Mushotzky, Richard (Technical Monitor)

2003-01-01

We present a deep observation with the X-Ray Multimirror Mission of PSR B1823-13, a young pulsar with similar properties to the Vela pulsar. We detect two components to the X-ray emission associated with PSR B1823-13: an elongated core of extent 30 min immediately surrounding the pulsar embedded in a fainter, diffuse component of emission 5 sec in extent, seen only on the southern side of the pulsar. The pulsar itself is not detected, either as a point source or through its pulsations. Both components of the X-ray emission are well fitted by a power-law spectrum, with photon index Gamma approx. 1.6 and X-ray luminosity (0.5-10 keV) L(sub X) approx. 9 x 10(exp 32) ergs/s for the core and Gamma approx. 2.3 and L(sub X) approx. 3 x 10(exp 33) ergs/s for the diffuse emission, for a distance of 4 kpc. We interpret both components of emission as corresponding to a pulsar wind nebula, which we designate G18.0-0.7. We argue that the core region represents the wind termination shock of this nebula, while the diffuse component indicates the shocked downstream wind. We propose that the asymmetric morphology of the diffuse emission with respect to the pulsar is the result of a reverse shock from an associated supernova remnant, which has compressed and distorted the pulsar-powered nebula. Such an interaction might be typical for pulsars at this stage in their evolution. The associated supernova remnant is not detected directly, most likely being too faint to be seen in existing X-ray and radio observations.

Atmospheric dispersion of natural carbon dioxide emissions on Vulcano Island, Italy

NASA Astrophysics Data System (ADS)

Granieri, D.; Carapezza, M. L.; Barberi, F.; Ranaldi, M.; Ricci, T.; Tarchini, L.

2014-07-01

La Fossa quiescent volcano and its surrounding area on the Island of Vulcano (Italy) are characterized by intensive, persistent degassing through both fumaroles and diffuse soil emissions. Periodic degassing crises occur, with marked increase in temperature and steam and gas output (mostly CO2) from crater fumaroles and in CO2 soil diffuse emission from the crater area as well as from the volcano flanks and base. The gas hazard of the most inhabited part of the island, Vulcano Porto, was investigated by simulating the CO2 dispersion in the atmosphere under different wind conditions. The DISGAS (DISpersion of GAS) code, an Eulerian model based on advection-diffusion equations, was used together with the mass-consistent Diagnostic Wind Model. Numerical simulations were validated by measurements of air CO2 concentration inside the village and along the crater's rim by means of a Soil CO2 Automatic Station and a Tunable Diode Laser device. The results show that in the village of Vulcano Porto, the CO2 air concentration is mostly due to local soil degassing, while the contribution from the crater gas emission is negligible at the breathing height for humans and always remains well below the lowest indoor CO2 concentration threshold recommended by the health authorities (1000 ppm). Outdoor excess CO2 maxima up to 200 ppm above local background CO2 air concentration are estimated in the center of the village and up to 100 ppm in other zones. However, in some ground excavations or in basements the health code threshold can be exceeded. In the crater area, because of the combined effect of fumaroles and diffuse soil emissions, CO2 air concentrations can reach 5000-7000 ppm in low-wind conditions and pose a health hazard for visitors.

Adsorbate Diffusion on Transition Metal Nanoparticles

DTIC Science & Technology

2015-01-01

different sizes and shapes using density functional theory calculations. We show that nanoparticles bind adsorbates more strongly than the...structure theoretical methods, a quantitative study with accurate density functional theory (DFT) calculations is still missing. Here, we perform a...functional theory . The projector augmented wave (PAW) potentials29,30 were used for electron- ion interactions and the generalized gradient approximation

Studying Solar Wind Properties Around CIRs and Their Effects on GCR Modulation

NASA Astrophysics Data System (ADS)

Ghanbari, K.; Florinski, V. A.

2017-12-01

Corotating interaction region (CIR) events occur when a fast solar wind stream overtakes slow solar wind, forming a compression region ahead and a rarefaction region behind in the fast solar wind. Usually this phenomena occurs along with a crossing of heliospheric current sheet which is the surface separating solar magnetic fields of opposing polarities. In this work, the solar plasma data provided by the ACE science center are utilized to do a superposed epoch analysis on solar parameters including proton density, proton temperature, solar wind speed and solar magnetic field in order to study how the variations of these parameters affect the modulation of galactic cosmic rays. Magnetic fluctuation variances in different parts a of CIR are computed and analyzed using similar techniques in order to understand the cosmic-ray diffusive transport in these regions.

Augmented Articles: The Future of Peer-Reviewed Publications?

NASA Astrophysics Data System (ADS)

Madura, Thomas Ignatius; Clementel, Nicola; Gull, Theodore R.

2015-08-01

The predominance of 2D figures and animations in the literature is clearly driven by the need to display data in a classic paper-journal format. However, there is no real reason that researchers should be limited to 2D graphics when presenting their results in peer-reviewed publications. This is especially true since all major astrophysical journals are now published online. So-called ‘augmented articles’ are possible, in which 3D interactive models, images, sound, and video can be included directly within an Adobe Portable Document Format (PDF) article. The inclusion of 3D interactive models in the astrophysics literature is slowly becoming popular, and several journals now fully support the inclusion of 3D interactive figures and movies. I present examples of recently published augmented articles in astronomy (e.g. Madura et al. 2015, arXiv:1503.00716) and discuss their perceived benefits and limitations. Such articles may become the norm in astronomy as data and numerical simulations increasingly become multidimensional (see http://www.technologyreview.com/view/535796/astronomers-create-3-d-printed-model-of-colliding-stellar-winds/).

Design and Analysis of Horizontal Axial Flow Motor Shroud

NASA Astrophysics Data System (ADS)

Wang, Shiming; Shen, Yu

2018-01-01

The wind turbine diffuser can increase the wind energy utilization coefficient of the wind turbine, and the addition of the shroud to the horizontal axis wind turbine also plays a role of accelerating the flow of the condensate. First, the structure of the shroud was designed and then modeled in gambit. The fluent software was used to establish the mathematical model for simulation. The length of the shroud and the opening angle of the shroud are analyzed to determine the best shape of the shroud. Then compared the efficiency with or without the shroud, through the simulation and the experiment of the water tank, it is confirmed that the horizontal axis of the shroud can improve the hydrodynamic performance.

Experimental Measurement of RCS Jet Interaction Effects on a Capsule Entry Vehicle

NASA Technical Reports Server (NTRS)

Buck, Gregory M.; Watkins, A. Neal; Danehy, Paul M.; Inman, Jennifer A.; Alderfer, David W.; Dyakonov, Artem A.

2008-01-01

An investigation was made in NASA Langley Research Center s 31-Inch Mach 10 Tunnel to determine the effects of reaction-control system (RCS) jet interactions on the aft-body of a capsule entry vehicle. The test focused on demonstrating and improving advanced measurement techniques that would aid in the rapid measurement and visualization of jet interaction effects for the Orion Crew Exploration Vehicle while providing data useful for developing engineering models or validation of computational tools used to assess actual flight environments. Measurements included global surface imaging with pressure and temperature sensitive paints and three-dimensional flow visualization with a scanning planar laser induced fluorescence technique. The wind tunnel model was fabricated with interchangeable parts for two different aft-body configurations. The first, an Apollo-like configuration, was used to focus primarily on the forward facing roll and yaw jet interactions which are known to have significant aft-body heating augmentation. The second, an early Orion Crew Module configuration (4-cluster jets), was tested blowing only out of the most windward yaw jet, which was expected to have the maximum heating augmentation for that configuration. Jet chamber pressures and tunnel flow conditions were chosen to approximate early Apollo wind tunnel test conditions. Maximum heating augmentation values measured for the Apollo-like configuration (>10 for forward facing roll jet and 4 for yaw jet) using temperature sensitive paint were shown to be similar to earlier experimental results (Jones and Hunt, 1965) using a phase change paint technique, but were acquired with much higher surface resolution. Heating results for the windward yaw jet on the Orion configuration had similar augmentation levels, but affected much less surface area. Numerical modeling for the Apollo-like yaw jet configuration with laminar flow and uniform jet outflow conditions showed similar heating patterns, qualitatively, but also showed significant variation with jet exit divergence angle, with as much as 25 percent variation in heat flux intensity for a 10 degree divergence angle versus parallel outflow. These results along with the fabrication methods and advanced measurement techniques developed will be used in the next phase of testing and evaluation for the updated Orion RCS configuration.

Modeling the key factors that could influence the diffusion of CO2 from a wellbore blowout in the Ordos Basin, China.

PubMed

Li, Qi; Shi, Hui; Yang, Duoxing; Wei, Xiaochen

2017-02-01

Carbon dioxide (CO 2 ) blowout from a wellbore is regarded as a potential environment risk of a CO 2 capture and storage (CCS) project. In this paper, an assumed blowout of a wellbore was examined for China's Shenhua CCS demonstration project. The significant factors that influenced the diffusion of CO 2 were identified by using a response surface method with the Box-Behnken experiment design. The numerical simulations showed that the mass emission rate of CO 2 from the source and the ambient wind speed have significant influence on the area of interest (the area of high CO 2 concentration above 30,000 ppm). There is a strong positive correlation between the mass emission rate and the area of interest, but there is a strong negative correlation between the ambient wind speed and the area of interest. Several other variables have very little influence on the area of interest, e.g., the temperature of CO 2 , ambient temperature, relative humidity, and stability class values. Due to the weather conditions at the Shenhua CCS demonstration site at the time of the modeled CO 2 blowout, the largest diffusion distance of CO 2 in the downwind direction did not exceed 200 m along the centerline. When the ambient wind speed is in the range of 0.1-2.0 m/s and the mass emission rate is in the range of 60-120 kg/s, the range of the diffusion of CO 2 is at the most dangerous level (i.e., almost all Grade Four marks in the risk matrix). Therefore, if the injection of CO 2 takes place in a region that has relatively low perennial wind speed, special attention should be paid to the formulation of pre-planned, emergency measures in case there is a leakage accident. The proposed risk matrix that classifies and grades blowout risks can be used as a reference for the development of appropriate regulations. This work may offer some indicators in developing risk profiles and emergency responses for CO 2 blowouts.

Can Winds Driven by Active Galactic Nuclei Account for the Extragalactic Gamma-Ray and Neutrino Backgrounds?

NASA Astrophysics Data System (ADS)

Liu, Ruo-Yu; Murase, Kohta; Inoue, Susumu; Ge, Chong; Wang, Xiang-Yu

2018-05-01

Various observations are revealing the widespread occurrence of fast and powerful winds in active galactic nuclei (AGNs) that are distinct from relativistic jets, likely launched from accretion disks and interacting strongly with the gas of their host galaxies. During the interaction, strong shocks are expected to form that can accelerate nonthermal particles to high energies. Such winds have been suggested to be responsible for a large fraction of the observed extragalactic gamma-ray background (EGB) and the diffuse neutrino background, via the decay of neutral and charged pions generated in inelastic pp collisions between protons accelerated by the forward shock and the ambient gas. However, previous studies did not properly account for processes such as adiabatic losses that may reduce the gamma-ray and neutrino fluxes significantly. We evaluate the production of gamma rays and neutrinos by AGN-driven winds in detail by modeling their hydrodynamic and thermal evolution, including the effects of their two-temperature structure. We find that they can only account for less than ∼30% of the EGB flux, as otherwise the model would violate the independent upper limit derived from the diffuse isotropic gamma-ray background. If the neutrino spectral index is steep with Γ ≳ 2.2, a severe tension with the isotropic gamma-ray background would arise as long as the winds contribute more than 20% of the IceCube neutrino flux in the 10–100 TeV range. At energies ≳ 100 TeV, we find that the IceCube neutrino flux may still be accountable by AGN-driven winds if the spectral index is as small as Γ ∼ 2.0–2.1.

Global Evolution of an Accretion Disk with a Net Vertical Field: Coronal Accretion, Flux Transport, and Disk Winds

NASA Astrophysics Data System (ADS)

Zhu, Zhaohuan; Stone, James M.

2018-04-01

We report results from global ideal MHD simulations that study thin accretion disks (with thermal scale height H/R = 0.1 and 0.05) threaded by net vertical magnetic fields. Our computations span three orders of magnitude in radius, extend all the way to the pole, and are evolved for more than 1000 innermost orbits. We find that (1) inward accretion occurs mostly in the upper magnetically dominated regions of the disk at z ∼ R, similar to predictions from some previous analytical work and the “coronal accretion” flows found in GRMHD simulations. (2) A quasi-static global field geometry is established in which flux transport by inflows at the surface is balanced by turbulent diffusion. The resulting field is strongly pinched inwards at the surface. A steady-state advection–diffusion model, with a turbulent magnetic Prandtl number of order unity, reproduces this geometry well. (3) Weak unsteady disk winds are launched beyond the disk corona with the Alfvén radius R A /R 0 ∼ 3. Although the surface inflow is filamentary and the wind is episodic, we show that the time-averaged properties are well-described by steady-wind theory. Even with strong fields, β 0 = 103 at the midplane initially, only 5% of the angular momentum transport is driven by the wind, and the wind mass flux from the inner decade of the radius is only ∼0.4% of the mass accretion rate. (4) Within the disk, most of the accretion is driven by the Rϕ stress from the MRI and global magnetic fields. Our simulations have many applications to astrophysical accretion systems.

Lidar Measurements of On-Shore Wind Diffusion

NASA Technical Reports Server (NTRS)

Brown, R. M.; Michael, P.; Raynor, G.

1973-01-01

The concept to place electric power generating stations on the oceans off the coast of the United States has instilled new efforts in research for improved understanding of the diffusion properties of the atmosphere in the ocean-air interface. The Atomic Energy Commission has instigated a program by the Meteorology Group at Brookhaven National Laboratory to investigate the low level, on-shore wind systems that dominate many of the coastal regions. Analytical techniques and specialized instrumentation from previous studies at Brookhaven are being used in this new program. The Brookhaven Lidar system is used to measure some of the physical properties of the oil-fog plume originating from a portable smoke generator on a boat off the coast. The oil-fog plume is used as a tracer which can be observed, photographed and measured to determine the diffusive power of the atmosphere associated with the ocean-air interface and the discontinuities found in the ocean-land boundary. This paper will describe the program rather briefly and the oil-fog scattering measurements that have been made with the Lidar system.

XMM-Newton Observations of Solar Wind Charge Exchange Emission

NASA Technical Reports Server (NTRS)

Snowden, S. L.; Collier, M. R.; Kuntz, K. D.

2004-01-01

We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by O VII and O VIII lines at 0.57 keV and 0.65 keV, O VIII (and possibly Fe XVII) lines at approximately 0.8 keV, Ne IX lines at approximately 0.92 keV, and Mg XI lines at approximately 1.35 keV. This spectrum is consistent with what is expected from charge exchange emission between the highly ionized solar wind and either interstellar neutrals in the heliosphere or material from Earth's exosphere. The emission is clearly seen as a low-energy ( E less than 1.5 keV) spectral enhancement in one of a series of observations of the Hubble Deep Field North. The X-ray enhancement is concurrent with an enhancement in the solar wind measured by the ACE satellite. The solar wind enhancement reaches a flux level an order of magnitude more intense than typical fluxes at 1 AU, and has ion ratios with significantly enhanced higher ionization states. Whereas observations of the solar wind plasma made at a single point reflect only local conditions which may only be representative of solar wind properties with spatial scales ranging from less than half of an Earth radii (approximately 10 s) to 100 Earth radii, X-ray observations of solar wind charge exchange are remote sensing measurements which may provide observations which are significantly more global in character. Besides being of interest in its own right for studies of the solar system, this emission can have significant consequences for observations of more cosmological objects. It can provide emission lines at zero redshift which are of particular interest (e.g., O VII and O VIII) in studies of diffuse thermal emission, and which can therefore act as contamination in objects which cover the entire detector field of view. We propose the use of solar wind monitoring data, such as from the ACE and Wind spacecraft, as a diagnostic to screen for such possibilities.

On the origin of jets from disc-accreting magnetized stars

NASA Astrophysics Data System (ADS)

Lovelace, Richard V. E.; Romanova, Marina M.; Lii, Patrick; Dyda, Sergei

2014-09-01

A brief review of the origin of jets from disc-accreting rotating magnetized stars is given. In most models, the interior of the disc is characterized by a turbulent viscosity and magnetic diffusivity ("alpha" discs) whereas the coronal region outside the disc is treated using ideal magnetohydrodynamics (MHD). Extensive MHD simulations have established the occurrence of long-lasting outflows in the case of both slowly and rapidly rotating stars. (1) Slowly rotating stars exhibit a new type of outflow, conical winds. Conical winds are generated when stellar magnetic flux is bunched up by the inward motion of the accretion disc. Near their region of origin, the winds have a thin conical shell shape with half opening angle of ˜30°. At large distances, their toroidal magnetic field collimates the outflow forming current carrying, matter dominated jets. These winds are predominantly magnetically and not centrifugally driven. About 10-30% of the disc matter from the inner disc is launched in the conical wind. Conical winds may be responsible for episodic as well as long lasting outflows in different types of stars. (2) Rapidly rotating stars in the "propeller regime" exhibit two-component outflows. One component is similar to the matter dominated conical wind, where a large fraction of the disc matter may be ejected in this regime. The second component is a high-velocity, low-density magnetically dominated axial jet where matter flows along the open polar field lines of the star. The axial jet has a mass flux of about 10% that of the conical wind, but its energy flux, due to the Poynting flux, can be as large as for the conical wind. The jet's magnetically dominated angular momentum flux causes the star to spin down rapidly. Propeller-driven outflows may be responsible for protostellar jets and their rapid spin-down. When the artificial requirement of symmetry about the equatorial plane is dropped, the conical winds are found to come alternately from one side of the disc and then the other, even for the case where the stellar magnetic field is a centered axisymmetric dipole. Recent MHD simulations of disc accretion to rotating stars in the propeller regime have been done with no turbulent viscosity and no diffusivity. The strong turbulence observed is due to the magneto-rotational instability. This turbulence drives accretion in the disc and leads to episodic conical winds and jets.

Characterization of Synthetic Aperture Radar Image Features of the Ocean as a Function of Wind Speed and High Frequency Radar Products

DTIC Science & Technology

2012-06-01

virtual augmentation of the antenna size to the equivalent distance travelled by the...Portugal 7. Instituto Hidrografico - Biblioteca Portuguese Navy, Instituto Hidrografico Lisbon, Portugal 8. Escola Naval - CINAV Base Naval...de Lisboa, 2810-001 Alfeite Almada, Portugal 9. Escola Naval - Biblioteca Base Naval de Lisboa, 2810-001 Alfeite Almada, Portugal 10. LT Ricardo Vicente Portuguese Navy, Instituto Hidrografico Lisbon, Portugal

Bayesian Hierarchical Models to Augment the Mediterranean Forecast System

DTIC Science & Technology

2010-09-30

In part 2 (Bonazzi et al., 2010), the impact of the ensemble forecast methodology based on MFS-Wind-BHM perturbations is documented. Forecast...absence of dt data stage inputs, the forecast impact of MFS-Error-BHM is neutral. Experiments are underway now to introduce dt back into the MFS-Error...BHM and quantify forecast impacts at MFS. MFS-SuperEnsemble-BHM We have assembled all needed datasets and completed algorithmic development

The dynamic inducer as a cost-effective wind turbine system

NASA Astrophysics Data System (ADS)

Gyatt, G.; Zalay, A.

The efficacy of dynamic inducer tip vanes, short airfoil sections attached perpendicularly at the outer end of wind turbine rotors, were investigated analytically and experimentally. The airfoil section is oriented to lift toward the center of the rotor, thereby forcing a greater flow toward the center of the actuator disk. Also, since the vortex shed by one tip vane posterior edge is exactly opposite in sign to the vortex produced at the anterior edge of the immediately preceeding vane, a synchronous state arises wherein drag on the tip vanes is eliminated. A numerical model was developed for the wind turbine power coefficient in a synchronous state. The simulation indicated that more kinetic energy than present in the actuator disk alone can be captured. Design features of the blades and fairing are described. Dynamic inducer WECS were projected to cost 20% less than equivalent conventional horizontal axis machines, while power augmentation can approach 70%, thus exceeding the Betz limit.

Effect of screens in wide-angle diffusers

NASA Technical Reports Server (NTRS)

Schubauer, G B; Spangenberg, W G

1949-01-01

An experimental investigation at low airspeeds was made of the filling effect observed when a screen or similar resistance is placed across a diffuser. The filling effect is found to be real in that screens can prevent separation or restore separated flow in diffusers even of extreme divergence and to depend principally on screen location and pressure-drop coefficient of the screen. Results are given for three different diffusers of circular cross section with a variety of screen arrangements. Effects of single screens and multiple screens are shown. The mechanics of the filling effect is explained, and possible efficiencies are discussed. Results of arrangements of multiple screens in wide-angle diffusers are given to show a possible application to damping screens as used in wind tunnels to reduce turbulence. (author)

X-Ray Investigation of the Diffuse Emission around Plausible γ-Ray Emitting Pulsar Wind Nebulae in Kookaburra Region

NASA Astrophysics Data System (ADS)

Kishishita, Tetsuichi; Bamba, Aya; Uchiyama, Yasunobu; Tanaka, Yasuyuki; Takahashi, Tadayuki

2012-05-01

We report on the results from Suzaku X-ray observations of the radio complex region called Kookaburra, which includes two adjacent TeV γ-ray sources HESS J1418-609 and HESS J1420-607. The Suzaku observation revealed X-ray diffuse emission around a middle-aged pulsar PSR J1420-6048 and a plausible pulsar wind nebula (PWN) Rabbit with elongated sizes of σX = 1farcm66 and σX = 1farcm49, respectively. The peaks of the diffuse X-ray emission are located within the γ-ray excess maps obtained by H.E.S.S. and the offsets from the γ-ray peaks are 2farcm8 for PSR J1420-6048 and 4farcm5 for Rabbit. The X-ray spectra of the two sources were well reproduced by absorbed power-law models with Γ = 1.7-2.3. The spectral shapes tend to become softer according to the distance from the X-ray peaks. Assuming the one-zone electron emission model as the first-order approximation, the ambient magnetic field strengths of HESS J1420-607 and HESS J1418-609 can be estimated as 3 μG and 2.5 μG, respectively. The X-ray spectral and spatial properties strongly support that both TeV sources are PWNe, in which electrons and positrons accelerated at termination shocks of the pulsar winds are losing their energies via the synchrotron radiation and inverse Compton scattering as they are transported outward.

Solar Wind Implantation into Lunar Regolith: Hydrogen Retention in a Surface with Defects

NASA Technical Reports Server (NTRS)

Farrell, W. M.; Hurley, D. M.; Zimmerman, M. I.

2014-01-01

Solar wind protons are implanted directly into the top 100 nm of the lunar near-surface region, but can either quickly diffuse out of the surface or be retained, depending upon surface temperature and the activation energy, U, associated with the implantation site. In this work, we explore the distribution of activation energies upon implantation and the associated hydrogen-retention times; this for comparison with recent observation of OH on the lunar surface. We apply a Monte Carlo approach: for simulated solar wind protons at a given local time, we assume a distribution of U values with a central peak, U(sub c) and width, U(sub w), and derive the fraction retained for long periods in the near-surface. We find that surfaces characterized by a distribution with predominantly large values of U (greater than 1 eV) like that expected at defect sites will retain implanted H (to likely form OH). Surfaces with the distribution predominantly at small values of U (less than 0.2 eV) will quickly diffuse away implanted H. However, surfaces with a large portion of activation energies between 0.3 eV less than U less than 0.9 eV will tend to be H-retentive in cool conditions but transform into H-emissive surfaces when warmed (as when the surface rotates into local noon). These mid-range activation energies give rise to a diurnal effect with diffusive loss of H at noontime.

Energetic Particle Transport across the Mean Magnetic Field: Before Diffusion

NASA Astrophysics Data System (ADS)

Laitinen, T.; Dalla, S.

2017-01-01

Current particle transport models describe the propagation of charged particles across the mean field direction in turbulent plasmas as diffusion. However, recent studies suggest that at short timescales, such as soon after solar energetic particle (SEP) injection, particles remain on turbulently meandering field lines, which results in nondiffusive initial propagation across the mean magnetic field. In this work, we use a new technique to investigate how the particles are displaced from their original field lines, and we quantify the parameters of the transition from field-aligned particle propagation along meandering field lines to particle diffusion across the mean magnetic field. We show that the initial decoupling of the particles from the field lines is slow, and particles remain within a Larmor radius from their initial meandering field lines for tens to hundreds of Larmor periods, for 0.1-10 MeV protons in turbulence conditions typical of the solar wind at 1 au. Subsequently, particles decouple from their initial field lines and after hundreds to thousands of Larmor periods reach time-asymptotic diffusive behavior consistent with particle diffusion across the mean field caused by the meandering of the field lines. We show that the typical duration of the prediffusive phase, hours to tens of hours for 10 MeV protons in 1 au solar wind turbulence conditions, is significant for SEP propagation to 1 au and must be taken into account when modeling SEP propagation in the interplanetary space.

Lift Augmentation on a Delta Wing via Leading Edge Fences and the Gurney Flap

NASA Technical Reports Server (NTRS)

Buchholz, Mark D.; Tso, Jin

1993-01-01

Wind tunnel tests have been conducted on two devices for the purpose of lift augmentation on a 60 deg delta wing at low speed. Lift, drag, pitching moment, and surface pressures were measured. Detailed flow visualization was also obtained. Both the leading edge fence and the Gurney flap are shown to increase lift. The fences and flap shift the lift curve by as much as 5 deg and 10 deg, respectively. The fences aid in trapping vortices on the upper surface, thereby increasing suction. The Gurney flap improves circulation at the trailing edge. The individual influences of both devices are roughly additive, creating high lift gain. However, the lower lift to drag ratio and the precipitation of vortex burst caused by the fences, and the nose down pitching moment created by the flap are also significant factors.

The capacity credit of grid-connected photovoltaic systems

NASA Astrophysics Data System (ADS)

Alsema, E. A.; van Wijk, A. J. M.; Turkenburg, W. C.

The capacity credit due photovoltaic (PV) power plants if integrated into the Netherlands grid was investigated, together with an estimate of the total allowable penetration. An hourly simulation was performed based on meteorological data from five stations and considering tilted surfaces, the current grid load pattern, and the load pattern after PV-power augmentation. The reliability of the grid was assessed in terms of a loss of load probability analysis, assuming power drops were limited to 1 GW. A projected tolerance for 2.5 GW of PV power was calculated. Peak demands were determined to be highest in winter, contrary to highest insolation levels; however, daily insolation levels coincided with daily peak demands. Combining the PV input with an equal amount of wind turbine power production was found to augment the capacity credit for both at aggregate outputs of 2-4 GW.

A Flight Investigation of the STOL Characteristics of an Augmented Jet Flap STOL Research Aircraft

NASA Technical Reports Server (NTRS)

Quigley, H. C.; Innis, R. C.; Grossmith, S.

1974-01-01

The flight test program objectives are: (1) To determine the in-flight aerodynamic, performance, and handling qualities of a jet STOL aircraft incorporating the augmented jet flap concept; (2) to compare the results obtained in flight with characteristics predicted from wind tunnel and simulator test results; (3) to contribute to the development of criteria for design and operation of jet STOL transport aircraft; and (4) to provide a jet STOL transport aircraft for STOL systems research and development. Results obtained during the first 8 months of proof-of-concept flight testing of the aircraft in STOL configurations are reported. Included are a brief description of the aircraft, fan-jet engines, and systems; a discussion of the aerodynamic, stability and control, and STOL performance; and pilot opinion of the handling qualities and operational characteristics.

Recent developments in ejector technology in the Air Force: An overview

NASA Technical Reports Server (NTRS)

Nagaraja, K. S.

1979-01-01

Basic and applied studies in thrust augmentation conducted at the Aerospace Research Laboratory at Wright-Patterson AFB which led to an effective configuration of the jet flap diffuser ejector, are reviewed. A method for compressible ejector flow analysis, developed in support of the preliminary design of an ejector thrust aircraft, is discussed and applied to single- and two-stage ejectors.

Gradient Augmented Level Set Method for Two Phase Flow Simulations with Phase Change

NASA Astrophysics Data System (ADS)

Anumolu, C. R. Lakshman; Trujillo, Mario F.

2016-11-01

A sharp interface capturing approach is presented for two-phase flow simulations with phase change. The Gradient Augmented Levelset method is coupled with the two-phase momentum and energy equations to advect the liquid-gas interface and predict heat transfer with phase change. The Ghost Fluid Method (GFM) is adopted for velocity to discretize the advection and diffusion terms in the interfacial region. Furthermore, the GFM is employed to treat the discontinuity in the stress tensor, velocity, and temperature gradient yielding an accurate treatment in handling jump conditions. Thermal convection and diffusion terms are approximated by explicitly identifying the interface location, resulting in a sharp treatment for the energy solution. This sharp treatment is extended to estimate the interfacial mass transfer rate. At the computational cell, a d-cubic Hermite interpolating polynomial is employed to describe the interface location, which is locally fourth-order accurate. This extent of subgrid level description provides an accurate methodology for treating various interfacial processes with a high degree of sharpness. The ability to predict the interface and temperature evolutions accurately is illustrated by comparing numerical results with existing 1D to 3D analytical solutions.

Development of an analytical Lagrangian model for passive scalar dispersion in low-wind speed meandering conditions

NASA Astrophysics Data System (ADS)

Stefanello, M. B.; Degrazia, G. A.; Mortarini, L.; Buligon, L.; Maldaner, S.; Carvalho, J. C.; Acevedo, O. C.; Martins, L. G. N.; Anfossi, D.; Buriol, C.; Roberti, D.

2018-02-01

Describing the effects of wind meandering motions on the dispersion of scalars is a challenging task, since this type of flow represents a physical state characterized by multiple scales. In this study, a Lagrangian stochastic diffusion model is derived to describe scalar transport during the horizontal wind meandering phenomenon that occurs within a planetary boundary layer. The model is derived from the linearization of the Langevin equation, and it employs a heuristic functional form that represents the autocorrelation function of meandering motion. The new solutions, which describe the longitudinal and lateral wind components, were used to simulate tracer experiments that were performed in low-wind speed conditions. The results of the comparison indicate that the new model can effectively reproduce the observed concentrations of the contaminants, and therefore, it can satisfactorily describe enhanced dispersion effects due to the presence of meandering.

The X-ray-emitting trail of the nearby pulsar PSR1929 + 10

NASA Technical Reports Server (NTRS)

Wang, Q. D.; Li, Zhi-Yun; Begelman, Mitchell C.

1993-01-01

The paper reports the detection by the Rosat satellite of a nebula associated with the nearby pulsar PSR1929 + 10, which is of a type different from the pulsar-wind nebulae produced by direct interaction of the relativistic wind from older pulsars with the interstellar medium (ISM) (Blandorf et al., 1973). The PSR1929 + 10 nebula appears as a linear diffuse X-ray feature in the direction opposite to the pulsar's proper motion, with the pulsar wind confined by the ram-pressure arising from the high velocity of the pulsar through the ISM. This results in a trail of relativistic electrons with enhanced emissions of synchrotron radiation.

Urban renewal based wind environment at pedestrian level in high-density and high-rise urban areas in Sai Ying Pun, Hong Kong

NASA Astrophysics Data System (ADS)

Yao, J. W.; Zheng, J. Y.; Zhao, Y.; Shao, Y. H.; Yuan, F.

2017-11-01

In high-density and high-rise urban areas, pedestrian level winds contribute to improve comfort, safety and diffusion of heat in urban areas. Outdoor wind study is extremely vital and a prerequisite in high-density cities considering that the immediate pedestrian level wind environment is fundamentally impacted by the presence of a series of high-rise buildings. In this paper, the research site of Sai Ying Pun in Hong Kong will be analysed in terms of geography, climate and urban morphology, while the surrounding natural ventilation has also been simulated by the wind tunnel experiment Computational Fluid Dynamics (CFD). It has found that, the existing problems in this district are the contradiction between planning control and commercial interests, which means some areas around tall buildings are not benefit to the residents because of the unhealthy wind environment. Therefore, some recommendation of urban renewal strategy has been provided.

Topological Origins of the Slow Solar Wind

NASA Technical Reports Server (NTRS)

Antiochos, Spiro

2008-01-01

Although the slow solar wind has been studied for decades with both in situ and remote sensing observations, its origin is still a matter of intense debate. In the standard quasi-steady model, the slow wind is postulated to originate near coronal hole boundaries that define topologically well-behaved separatrices between open and closed field regions. In the interchange model, on the other hand, the slow wind is postulated to originate on open flux that is dynamically diffusing throughout the seemingly closed-field corona. We argue in favor of the quasi-steady scenario and propose that the slow wind is due to two effects: First, the open-closed boundary is highly complex due to the complexity of the photospheric flux distribution. Second, this boundary is continuously driven by the transport of magnetic helicity from the closed field region into the open. The implications of this model for the structure and dynamics of the corona and slow wind are discussed, and observational tests of the mode

Wave Augmented Diffusers for Centrifugal Compressors

NASA Technical Reports Server (NTRS)

Paxson, Daniel E.; Skoch, Gary J.

1998-01-01

A conceptual device is introduced which would utilize unsteady wave motion to slow and turn flows in the diffuser section of a centrifugal compressor. The envisioned device would substantially reduce the size of conventional centrifugal diffusers by eliminating the relatively large ninety degree bend needed to turn the flow from the radial/tangential to the axial direction. The bend would be replaced by a wall and the flow would instead exit through a series of rotating ports located on a disk, adjacent to the diffuser hub, and fixed to the impeller shaft. The ports would generate both expansion and compression waves which would rapidly transition from the hub/shroud (axial) direction to the radial/tangential direction. The waves would in turn induce radial/tangential and axial flow. This paper presents a detailed description of the device. Simplified cycle analysis and performance results are presented which were obtained using a time accurate, quasi-one-dimensional CFD code with models for turning, port flow conditions, and losses due to wall shear stress. The results indicate that a periodic wave system can be established which yields diffuser performance comparable to a conventional diffuser. Discussion concerning feasibility, accuracy, and integration follow.

Galactic wind X-ray heating of the intergalactic medium during the Epoch of Reionization

NASA Astrophysics Data System (ADS)

Meiksin, Avery; Khochfar, Sadegh; Paardekooper, Jan-Pieter; Dalla Vecchia, Claudio; Kohn, Saul

2017-11-01

The diffuse soft X-ray emissivity from galactic winds is computed during the Epoch of Reionization (EoR). We consider two analytic models, a pressure-driven wind and a superbubble model, and a 3D cosmological simulation including gas dynamics from the First Billion Years (FiBY) project. The analytic models are normalized to match the diffuse X-ray emissivity of star-forming galaxies in the nearby Universe. The cosmological simulation uses physically motivated star formation and wind prescriptions, and includes radiative transfer corrections. The models and the simulation all are found to produce sufficient heating of the intergalactic medium to be detectable by current and planned radio facilities through 21 cm measurements during the EoR. While the analytic models predict a 21 cm emission signal relative to the cosmic microwave backgroundsets in by ztrans ≃ 8-10, the predicted signal in the FiBY simulation remains in absorption until reionization completes. The 21 cm absorption differential brightness temperature reaches a minimum of ΔT ≃ -130 to -200 mK, depending on model. Allowing for additional heat from high-mass X-ray binaries pushes the transition to emission to ztrans ≃ 10-12, with shallower absorption signatures having a minimum of ΔT ≃ -110 to -140 mK. The 21 cm signal may be a means of distinguishing between the wind models, with the superbubble model favouring earlier reheating. While an early transition to emission may indicate X-ray binaries dominate the reheating, a transition to emission as early as ztrans > 12 would suggest the presence of additional heat sources.

Effects of massive wind power integration on short-term water resource management in central Chile - a grid-wide study

NASA Astrophysics Data System (ADS)

Haas, J.; Olivares, M. A.; Palma, R.

2013-12-01

In central Chile, water from reservoirs and streams is mainly used for irrigation and power generation. Hydropower reservoirs operation is particularly challenging because: i) decisions at each plant impact the entire power system, and ii) the existence of large storage capacity implies inter-temporal ties. An Independent System Operator (ISO) decides the grid-wide optimal allocation of water for power generation, under irrigation-related constraints. To account for the long-term opportunity cost of water, a future cost function is determined and used in the short term planning. As population growth and green policies demand increasing levels of renewable energy in power systems, deployment of wind farms and solar plants is rising quickly. However, their power output is highly fluctuating on short time scales, affecting the operation of power plants, particularly those fast responding units as hydropower reservoirs. This study addresses these indirect consequences of massive introduction of green energy sources on reservoir operations. Short-term reservoir operation, under different wind penetration scenarios, is simulated using a replica of Chile's ISO's scheduling optimization tools. Furthermore, an ongoing study is exploring the potential to augment the capacity the existing hydro-power plants to better cope with the balancing needs due to a higher wind power share in the system. As reservoir releases determine to a great extent flows at downstream locations, hourly time series of turbined flows for 24-hour periods were computed for selected combinations between new wind farms and increased capacity of existing hydropower plants. These time series are compiled into subdaily hydrologic alteration (SDHA) indexes (Zimmerman et al, 2010). The resulting sample of indexes is then analyzed using duration curves. Results show a clear increase in the SDHA for every reservoir of the system as more fluctuating renewables are integrated into the system. High-fluctuation events become more frequent. While the main load-following reservoirs are very susceptible to even small levels of additional wind power, the remaining withstand greater amounts before producing a significant SDHA. The additional effect of augmented installed capacity of existing hydropower plants on the SDHA is modest. The increase in SDHA calls for alternative operational constraints beyond the current practice based exclusively on minimum instream flows. Previous research by this group has shown the potential of maximum ramping rates constraints to efficiently achieve improvement in the SDHA. This alternative is being studied as part of a project currently in progress. This may contribute to make hydropower projects more socially acceptable and environmentally sound.

An Investigation of Flow over High Roughness. Task I: Study of Airflow in Simulated Temperature and Tropical Forest Canopies, Fort Huachuca.

DTIC Science & Technology

ATMOSPHERIC MOTION, TREES), (*AEROSOLS, DIFFUSION ), TROPICAL REGIONS, SIMULATION, ATMOSPHERIC TEMPERATURE, TURBULENT BOUNDARY LAYER, ROUGHNESS, FORESTRY, ATMOSPHERE MODELS, WIND TUNNELS, COLORADO, MILITARY FACILITIES

Diffuse-Interface Capturing Methods for Compressible Two-Phase Flows

NASA Astrophysics Data System (ADS)

Saurel, Richard; Pantano, Carlos

2018-01-01

Simulation of compressible flows became a routine activity with the appearance of shock-/contact-capturing methods. These methods can determine all waves, particularly discontinuous ones. However, additional difficulties may appear in two-phase and multimaterial flows due to the abrupt variation of thermodynamic properties across the interfacial region, with discontinuous thermodynamical representations at the interfaces. To overcome this difficulty, researchers have developed augmented systems of governing equations to extend the capturing strategy. These extended systems, reviewed here, are termed diffuse-interface models, because they are designed to compute flow variables correctly in numerically diffused zones surrounding interfaces. In particular, they facilitate coupling the dynamics on both sides of the (diffuse) interfaces and tend to the proper pure fluid-governing equations far from the interfaces. This strategy has become efficient for contact interfaces separating fluids that are governed by different equations of state, in the presence or absence of capillary effects, and with phase change. More sophisticated materials than fluids (e.g., elastic-plastic materials) have been considered as well.

Renewable Energy for Rural Economic Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartman, Cathy L.; Stafford, Edwin R.

When Renewable Energy for Rural Economic Development (RERED) began in 2005, Utah had no commercial wind power projects in operation. Today, the state hosts two commercial wind power plants, the Spanish Fork Wind Project and the Milford Wind Corridor Project, totaling 324 megawatts (MW) of wind capacity. Another project in San Juan County is expected to break ground very soon, and two others, also in San Juan County, are in the approval process. RERED has played a direct role in advancing wind power (and other renewable energy and clean technology innovations) in Utah through its education outreach and research/publication initiatives.more » RERED has also witnessed and studied some of the persistent barriers facing wind power development in communities across Utah and the West, and its research expanded to examine the diffusion of other energy efficiency and clean technology innovations. RERED leaves a legacy of publications, government reports, and documentary films and educational videos (archived at www.cleantech.usu.edu) to provide important insights for entrepreneurs, policymakers, students, and citizens about the road ahead for transitioning society onto a cleaner, more sustainable future.« less

Observations From the Coupled Boundary Layer Air-Sea Transfer Experiment in Hurricanes

NASA Astrophysics Data System (ADS)

Black, P. G.

2006-12-01

The CBLAST field program conducted from 2002-2004 has shown that the wind speed range for which turbulent momentum and moisture exchange coefficients have been derived based upon direct flux measurements has been extended by 30 and 60 percent, respectively, from airborne observations in Hurricanes Fabian and Isabel in 2003. The drag coefficient (CD) values derived from CBLAST momentum flux measurements show CD becoming invariant with wind speed near a 23 ms-1 threshold rather than a hurricane-force threshold near 33 ms-1. Values above 23 ms-1 are lower than previous open ocean measurements. The Dalton number estimates (CE) derived from CBLAST moisture flux measurements are shown to be invariant with wind speed to 30 ms-1, in approximate agreement with previous measurements at lower winds. These observations imply a CE/CD ratio of approximately 0.7, suggesting that additional energy sources are necessary for hurricanes to achieve their maximum potential intensity. Two such additional mechanisms for augmented moisture flux in the boundary layer might be 1) augmented wave breaking by short-crested, fetch limited waves suggested by whitecap aerial coverage measurements, and 2) sea spray at high winds suggested by laboratory spray source function measurements. Linear coherent features in the hurricane boundary layer are a third mechanism, observed during CBLAST 2002 aircraft measurements, to have wavelengths of 0.9 to 1.2 km. Linear features of the same wavelength range were observed in nearly-concurrent RADARSAT Synthetic Aperture Radar (SAR) imagery. Arrays of drifting buoys and subsurface floats were successfully deployed ahead of Hurricanes Fabian (2003) and Frances (2004): 16 (6) and 38 (14) drifters (floats). Two types of surface drifters and three types of floats provided observations of surface and subsurface oceanic currents, temperature, salinity, gas exchange, bubble concentrations and surface wave spectra to a depth of 200 m on a continuous basis before, during and after storm passage. Float observations indicated deepening of the mixed layer from 40 to 120 m in approximately 8 hr with a corresponding decrease in SST in the right-rear quadrant of 3.2 ºC in 11 hr, roughly one-half inertial period. Strong inertial currents with a peak amplitude of 1.5 ms-1 were observed. Vertical structure showed the critical Richardson number was reached sporadically during the mixed-layer deepening event, suggesting shear-induced mixing as a prominent mechanism during storm passage.

Radial diffusion comparing a THEMIS statistical model with geosynchronous measurements as the outer boundary

NASA Astrophysics Data System (ADS)

Li, Z.; Hudson, M. K.; Chen, Y.

2013-12-01

The outer boundary energetic electron flux is used as a driver in radial diffusion calculations, and its precise determination is critical to the solution. A new model was proposed recently based on THEMIS measurements to express the boundary flux as three fit functions of solar wind parameters in a response window, that depend on energy and which solar parameter is used: speed, density, or both (Shin and Lee, 2013). The Dartmouth radial diffusion model has been run using LANL geosynchronous satellite measurements as the outer boundary for a one-month interval in July to August 2004 and the calculated phase space density (PSD) is compared with GPS measurements at the GPS orbit (L=4.16), at magnetic equatorial plane crossings, as a test of the model. We also used the outer boundary generated from the Shin and Lee model and examined this boundary condition by computing the error relative to the simulation using a LANL geosynchronous spacecraft data-driven outer boundary. The calculation shows that there is overestimation and underestimation at different times, however the new boundary condition can be used to drive the radial diffusion model generally, producing the phase space density increase and dropout during a storm with a relatively small error. Having this new method based on a solar wind parametrized data set, we can run the radial diffusion model for storms when particle measurements are not available at the outer boundary. We chose the Whole Heliosphere Interval (WHI) as an example and compared the result with MHD/test-particle simulations (Hudson et al., 2012), obtaining much better agreement with PSD based on GPS measurements at L=4.16 using the diffusion model, which incorporates atmospheric losses.

Vortex-augmented cooling tower-windmill combination

DOEpatents

McAllister, Jr., John E.

1985-01-01

A cooling tower for cooling large quantities of effluent water from a production facility by utilizing natural wind forces includes the use of a series of helically directed air inlet passages extending outwardly from the base of the tower to introduce air from any direction in a swirling vortical pattern while the force of the draft created in the tower makes it possible to place conventional power generating windmills in the air passages to provide power as a by-product.

Studies of Transitional Flow, Unsteady Separation Phenomena and Particle Induced Augmentation Heating on Ablated Nose Tips.

DTIC Science & Technology

1975-10-01

63 29 Variation of Profile Shape with Time for Axisyinmetric Camphor Models 63 30 The Development of Ablated Nose Shapes Over Which Flow...ablation tests using camphor models and inferred from downrange observation of full scale flight missions. Regions of gross instability on nose...been verified in wind tunnel tests of camphor models where shapes similar to those shown on Figure 29 can be developed under transitional conditions

Vortex-augmented cooling tower - windmill combination

DOEpatents

McAllister, J.E. Jr.

1982-09-02

A cooling tower for cooling large quantities of effluent water from a production facility by utilizing natural wind forces includes the use of a series of helically directed air inlet passages extending outwardly from the base of the tower to introduce air from any direction in a swirling vortical pattern while the force of the draft created in the tower makes it possible to place conventional power generating windmills in the air passage to provide power as a by-product.

Plasma Diffusion in Self-Consistent Fluctuations

NASA Technical Reports Server (NTRS)

Smets, R.; Belmont, G.; Aunai, N.

2012-01-01

The problem of particle diffusion in position space, as a consequence ofeleclromagnetic fluctuations is addressed. Numerical results obtained with a self-consistent hybrid code are presented, and a method to calculate diffusion coefficient in the direction perpendicular to the mean magnetic field is proposed. The diffusion is estimated for two different types of fluctuations. The first type (resuiting from an agyrotropic in itiai setting)is stationary, wide band white noise, and associated to Gaussian probability distribution function for the magnetic fluctuations. The second type (result ing from a Kelvin-Helmholtz instability) is non-stationary, with a power-law spectrum, and a non-Gaussian probabi lity distribution function. The results of the study allow revisiting the question of loading particles of solar wind origin in the Earth magnetosphere.

Dynamic wake model with coordinated pitch and torque control of wind farms for power tracking

NASA Astrophysics Data System (ADS)

Shapiro, Carl; Meyers, Johan; Meneveau, Charles; Gayme, Dennice

2017-11-01

Control of wind farm power production, where wind turbines within a wind farm coordinate to follow a time-varying power set point, is vital for increasing renewable energy participation in the power grid. Previous work developed a one-dimensional convection-diffusion equation describing the advection of the velocity deficit behind each turbine (wake) as well the turbulent mixing of the wake with the surrounding fluid. Proof-of-concept simulations demonstrated that a receding horizon controller built around this time-dependent model can effectively provide power tracking services by modulating the thrust coefficients of individual wind turbines. In this work, we extend this model-based controller to include pitch angle and generator torque control and the first-order dynamics of the drive train. Including these dynamics allows us to investigate control strategies for providing kinetic energy reserves to the grid, i.e. storing kinetic energy from the wind in the rotating mass of the wind turbine rotor for later use. CS, CM, and DG are supported by NSF (ECCS-1230788, CMMI 1635430, and OISE-1243482, the WINDINSPIRE project). JM is supported by ERC (ActiveWindFarms, 306471). This research was conducted using computational resources at MARCC.

Simulation of Helium-3 Extraction from Lunar Ilmenite

NASA Technical Reports Server (NTRS)

Kuhlman, K. R.; Kulcinski, G. L.; Schmitt, H. H.

2004-01-01

Knowledge of the trapping mechanisms and diffusion characteristics of solar-wind implanted isotopes in the minerals of the lunar regolith will enable the optimization of the processes to extract solar wind gases from regolith particles. Extraction parameters include the temperature and duration of extraction, particle size, and gas yield. Diffusion data will increase the efficiency and profitability of future mining ventures. This data will also assist in optimizing the evaluations of various potential mining sites based on remote sensing data. For instance, if magnesian ilmenite (Mg,Fel.,Ti03) is found to retain He better than stoichiometric ilmenite (FeTi03), remote sensing data for Mg could be considered in addition to Ti and maturity data. The context of the currently discussed work is the mining of helium-3 for potential use as a fuel for fusion energy generation. However, the potential resources deposited by the solar wind include hydrogen (and derived water), helium-4, nitrogen and carbon. Implantation experiments such as those performed for helium isotopes in ilmenite are important for the optimized extraction of these additional resources. These experiments can easily be reproduced for most elements or isotopes of interest.

Study on gas diffusion emitted from different height of point source.

PubMed

Yassin, Mohamed F

2009-01-01

The flow and dispersion of stack-gas emitted from different elevated point source around flow obstacles in an urban environment have been investigated, using computational fluid dynamics models (CFD). The results were compared with the experimental results obtained from the diffusion wind tunnel under different conditions of thermal stability (stable, neutral or unstable). The flow and dispersion fields in the boundary layer in an urban environment were examined with different flow obstacles. Gaseous pollutant was discharged in the simulated boundary layer over the flat area. The CFD models used for the simulation were based on the steady-state Reynolds-Average Navier-Stoke equations (RANS) with kappa-epsilon turbulence models; standard kappa-epsilon and RNG kappa-epsilon models. The flow and dispersion data measured in the wind tunnel experiments were compared with the results of the CFD models in order to evaluate the prediction accuracy of the pollutant dispersion. The results of the CFD models showed good agreement with the results of the wind tunnel experiments. The results indicate that the turbulent velocity is reduced by the obstacles models. The maximum dispersion appears around the wake region of the obstacles.

Recent Developments in the Radiation Belt Environment Model

NASA Technical Reports Server (NTRS)

Fok, M.-C.; Glocer, A.; Zheng, Q.; Horne, R. B.; Meredith, N. P.; Albert, J. M.; Nagai, T.

2010-01-01

The fluxes of energetic particles in the radiation belts are found to be strongly controlled by the solar wind conditions. In order to understand and predict the radiation particle intensities, we have developed a physics-based Radiation Belt Environment (RBE) model that considers the influences from the solar wind, ring current and plasmasphere. Recently, an improved calculation of wave-particle interactions has been incorporated. In particular, the model now includes cross diffusion in energy and pitch-angle. We find that the exclusion of cross diffusion could cause significant overestimation of electron flux enhancement during storm recovery. The RBE model is also connected to MHD fields so that the response of the radiation belts to fast variations in the global magnetosphere can be studied.Weare able to reproduce the rapid flux increase during a substorm dipolarization on 4 September 2008. The timing is much shorter than the time scale of wave associated acceleration.

Interstellar Pickup Ion Acceleration in the Turbulent Magnetic Field at the Solar Wind Termination Shock Using a Focused Transport Approach

NASA Astrophysics Data System (ADS)

Ye, Junye; le Roux, Jakobus A.; Arthur, Aaron D.

2016-08-01

We study the physics of locally born interstellar pickup proton acceleration at the nearly perpendicular solar wind termination shock (SWTS) in the presence of a random magnetic field spiral angle using a focused transport model. Guided by Voyager 2 observations, the spiral angle is modeled with a q-Gaussian distribution. The spiral angle fluctuations, which are used to generate the perpendicular diffusion of pickup protons across the SWTS, play a key role in enabling efficient injection and rapid diffusive shock acceleration (DSA) when these particles follow field lines. Our simulations suggest that variation of both the shape (q-value) and the standard deviation (σ-value) of the q-Gaussian distribution significantly affect the injection speed, pitch-angle anisotropy, radial distribution, and the efficiency of the DSA of pickup protons at the SWTS. For example, increasing q and especially reducing σ enhances the DSA rate.

Experimental Evaluation of Turning Vane Designs for High-speed and Coupled Fan-drive Corners of 0.1-scale Model of NASA Lewis Research Center's Proposed Altitude Wind Tunnel

NASA Technical Reports Server (NTRS)

Gelder, Thomas F.; Moore, Royce D.; Shyne, Rickey J.; Boldman, Donald R.

1987-01-01

Two turning vane designs were experimentally evaluated for the fan-drive corner (corner 2) coupled to an upstream diffuser and the high-speed corner (corner 1) of the 0.1 scale model of NASA Lewis Research Center's proposed Altitude Wind Tunnel. For corner 2 both a controlled-diffusion vane design (vane A4) and a circular-arc vane design (vane B) were studied. The corner 2 total pressure loss coefficient was about 0.12 with either vane design. This was about 25 percent less loss than when corner 2 was tested alone. Although the vane A4 design has the advantage of 20 percent fewer vanes than the vane B design, its vane shape is more complex. The effects of simulated inlet flow distortion on the overall losses for corner 1 or 2 were small.

Evaluation of the NASA Ames no. 1 7 by 10 foot wind tunnel as an acoustic test facility

NASA Technical Reports Server (NTRS)

Wilby, J. F.; Scharton, T. D.

1975-01-01

Measurements were made in the no. 1 7'x10' wind tunnel at NASA Ames Research Center, with the objectives of defining the acoustic characteristics and recommending minimum cost treatments so that the tunnel can be converted into an acoustic research facility. The results indicate that the noise levels in the test section are due to (a) noise generation in the test section, associated with the presence of solid bodies such as the pitot tube, and (b) propagation of acoustic energy from the fan. A criterion for noise levels in the test section is recommended, based on low-noise microphone support systems. Noise control methods required to meet the criterion include removal of hardware items for the test section and diffuser, improved design of microphone supports, and installation of acoustic treatment in the settling chamber and diffuser.

Gas exchange across the air-sea interface

NASA Astrophysics Data System (ADS)

Hasse, L.; Liss, P. S.

1980-10-01

The physics of gas exchange at the air-sea interface are reviewed. In order to describe the transfer of gases in the liquid near the boundary, a molecular plus eddy diffusivity concept is used, which has been found useful for smooth flow over solid surfaces. From consideration of the boundary conditions, a similar dependence of eddy diffusivity on distance from the interface can be derived for the flow beneath a gas/liquid interface, at least in the absence of waves. The influence of waves is then discussed. It is evident from scale considerations that the effect of gravity waves is small. It is known from wind tunnel work that capillary waves enhance gas transfer considerably. The existing hypotheses are apparently not sufficient to explain the observations. Examination of field data is even more frustrating since the data do not show the expected increase of gas exchange with wind speed.

Observations at the planet Mercury by the plasma electron experiment - Mariner 10

NASA Technical Reports Server (NTRS)

Ogilvie, K. W.; Scudder, J. D.; Vasyliunas, V. M.; Hartle, R. E.; Siscoe, G. L.

1977-01-01

Two nightside encounters with Mercury's magnetosphere by Mariner 10 revealed bow shock and magnetosheath signatures in the plasma electron data that are entirely consistent with the geometry expected for an interaction between a planet-centered magnetic dipole and the solar wind. The geometrically determined distance between the planet's center and the solar wind stagnation point is 1.4 plus or minus 0.1 R sub M. Both diffuse and sharp shock crossings were observed on the two magnetosphere encounters.

Vertical profile of tritium concentration in air during a chronic atmospheric HT release.

PubMed

Noguchi, Hiroshi; Yokoyama, Sumi

2003-03-01

The vertical profiles of tritium gas and tritiated water concentrations in air, which would have an influence on the assessment of tritium doses as well as on the environmental monitoring of tritium, were measured in a chronic tritium gas release experiment performed in Canada in 1994. While both of the profiles were rather uniform during the day because of atmospheric mixing, large gradients of the profiles were observed at night. The gradient coefficients of the profiles were derived from the measurements. Correlations were analyzed between the gradient coefficients and meteorological conditions: solar radiation, wind speed, and turbulent diffusivity. It was found that the solar radiation was highly correlated with the gradient coefficients of tritium gas and tritiated water profiles and that the wind speed and turbulent diffusivity showed weaker correlations with those of tritiated water profiles. A one-dimensional tritium transport model was developed to analyze the vertical diffusion of tritiated water re-emitted from the ground into the atmosphere. The model consists of processes of tritium gas deposition to soil including oxidation into tritiated water, reemission of tritiated water, dilution of tritiated water in soil by rain, and vertical diffusion of tritiated water in the atmosphere. The model accurately represents the accumulation of tritiated water in soil water and the time variations and vertical profiles of tritiated water concentrations in air.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laitinen, T.; Dalla, S., E-mail: tlmlaitinen@uclan.ac.uk

Current particle transport models describe the propagation of charged particles across the mean field direction in turbulent plasmas as diffusion. However, recent studies suggest that at short timescales, such as soon after solar energetic particle (SEP) injection, particles remain on turbulently meandering field lines, which results in nondiffusive initial propagation across the mean magnetic field. In this work, we use a new technique to investigate how the particles are displaced from their original field lines, and we quantify the parameters of the transition from field-aligned particle propagation along meandering field lines to particle diffusion across the mean magnetic field. Wemore » show that the initial decoupling of the particles from the field lines is slow, and particles remain within a Larmor radius from their initial meandering field lines for tens to hundreds of Larmor periods, for 0.1–10 MeV protons in turbulence conditions typical of the solar wind at 1 au. Subsequently, particles decouple from their initial field lines and after hundreds to thousands of Larmor periods reach time-asymptotic diffusive behavior consistent with particle diffusion across the mean field caused by the meandering of the field lines. We show that the typical duration of the prediffusive phase, hours to tens of hours for 10 MeV protons in 1 au solar wind turbulence conditions, is significant for SEP propagation to 1 au and must be taken into account when modeling SEP propagation in the interplanetary space.« less

The Born-again Planetary Nebula A78: An X-Ray Twin of A30

NASA Astrophysics Data System (ADS)

Toalá, J. A.; Guerrero, M. A.; Todt, H.; Hamann, W.-R.; Chu, Y.-H.; Gruendl, R. A.; Schönberner, D.; Oskinova, L. M.; Marquez-Lugo, R. A.; Fang, X.; Ramos-Larios, G.

2015-01-01

We present the XMM-Newton discovery of X-ray emission from the planetary nebula (PN) A78, the second born-again PN detected in X-rays apart from A30. These two PNe share similar spectral and morphological characteristics: they harbor diffuse soft X-ray emission associated with the interaction between the H-poor ejecta and the current fast stellar wind and a point-like source at the position of the central star (CSPN). We present the spectral analysis of the CSPN, using for the first time an NLTE code for expanding atmospheres that takes line blanketing into account for the UV and optical spectra. The wind abundances are used for the X-ray spectral analysis of the CSPN and the diffuse emission. The X-ray emission from the CSPN in A78 can be modeled by a single C VI emission line, while the X-ray emission from its diffuse component is better described by an optically thin plasma emission model with a temperature of kT = 0.088 keV (T ≈ 1.0 × 106 K). We estimate X-ray luminosities in the 0.2-2.0 keV energy band of L X, CSPN = (1.2 ± 0.3) × 1031 erg s-1 and L X, DIFF = (9.2 ± 2.3) × 1030 erg s-1 for the CSPN and diffuse components, respectively.

Selected advanced aerodynamic and active control concepts development

NASA Technical Reports Server (NTRS)

1981-01-01

A task for the Energy Efficient Transport program conducted: (1) The design and wind tunnel development of high-aspect-ratio supercritical wings, investigating the cruise speed regime and also high-lift. (2) The preliminary design and evaluation of an aircraft combining a high-aspect-ratio supercritical wing with a winglet. (3) Active Controls: The determination of criteria, configuration, and flying qualities associated with augmented longitudinal stability of a level likely to be acceptable for the next generation transport; and the design of a practical augmentation system. The baseline against which the work was performed and evaluated was the Douglas DC-X-200 twin engine derivative of the DC-10 transport. The supercritical wing development showed that the cruise and buffet requirements could be achieved and that the wing could be designed to realize a sizable advantage over today's technology. Important advances in high lift performance were shown. The design study of an aircraft with supercritical wing and winglet suggested advantages in weight and fuel economy could be realized. The study of augmented stability, conducted with the aid of a motion base simulator, concluded that a negative static margin was acceptable for the baseline unaugmented aircraft.

Investigation of water vapor motion winds from geostationary satellites

NASA Technical Reports Server (NTRS)

Velden, Christopher S.; Nieman, Steven J.; Wanzong, Steven

1994-01-01

Water vapor imagery from geostationary satellites has been available for over a decade. These data are used extensively by operational analysts and forecasters, mainly in a qualitative mode (Weldon and Holmes 1991). In addition to qualitative applications, motions deduced in animated water vapor imagery can be used to infer wind fields in cloudless regimes, thereby augmenting the information provided by cloud-drift wind vectors. Early attempts at quantifying the data by tracking features in water vapor imagery met with modest success (Stewart et al. 1985; Hayden and Stewart 1987). More recently, automated techniques have been developed and refined, and have resulted in upper-level wind observations comparable in quality to current operational cloud-tracked winds (Laurent 1993). In a recent study by Velden et al. (1993) it was demonstrated that wind sets derived from Meteosat-3 (M-3) water vapor imagery can provide important environmental wind information in data void areas surrounding tropical cyclones, and can positively impact objective track forecasts. M-3 was repositioned to 75W by the European Space Agency in 1992 in order to provide complete coverage of the Atlantic Ocean. Data from this satellite are being transmitted to the U.S. for operational use. Compared with the current GOES-7 (G-7) satellite (positioned near 112W), the M-3 water vapor channel contains a superior horizontal resolution (5 km vs. 16 km ). In this paper, we examine wind sets derived using automated procedures from both GOES-7 and Meteosat-3 full disk water vapor imagery in order to assess this data as a potentially important source of large-scale wind information. As part of a product demonstration wind sets were produced twice a day at CIMSS during a six-week period in March and April (1994). These data sets are assessed in terms of geographic coverage, statistical accuracy, and meteorological impact through preliminary results of numerical model forecast studies.

Applicability of steady models for hot-star winds

NASA Technical Reports Server (NTRS)

Owocki, Stanley P.; Poe, Clint H.; Castor, John I.

1990-01-01

Non-Sobolev models of radiatively driven stellar winds based on a pure-absorption approximation do not have a well-defined steady state. Here the implications of this for flow time-dependence are examined, showing that, under such circumstances, instabilities in the flow attain an absolute character that leads to intrinsic variability. In this case, steady solutions are inherently inapplicable because they do not represent physically realizable states. However, for actual hot-star winds, driving is principally by scattering, not pure absorption. In practice, the relatively weak force associated with slight asymmetries in the diffuse, scattered radiation field may play a crucial role in breaking the solution degeneracy and reducing the instability from an absolute to an advective character.

Numerical Study of Flow Augmented Thermal Management for Entry and Re-Entry Environments

NASA Technical Reports Server (NTRS)

Cheng, Gary C.; Neroorkar, Kshitij D.; Chen, Yen-Sen; Wang, Ten-See; Daso, Endwell O.

2007-01-01

The use of a flow augmented thermal management system for entry and re-entr environments is one method for reducing heat and drag loads. This concept relies on jet penetration from supersonic and hypersonic counterflowing jets that could significantly weaken and disperse the shock-wave system of the spacecraft flow field. The objective of this research effort is to conduct parametric studies of the supersonic flow over a 2.6% scale model of the Apollo capsule, with and without the counterflowing jet, using time-accurate and steady-state computational fluid dynamics simulations. The numerical studies, including different freestream Mach number angle of attack counterflowing jet mass flow rate, and nozzle configurations, were performed to examine their effect on the drag and beat loads and to explore the counternowing jet condition. The numerical results were compared with the test data obtained from transonic blow-down wind-tunnel experiments conducted independently at NASA MSFC.

Lift augmentation on a delta wing via leading edge fences and the Gurney flap. M.S. Thesis

NASA Technical Reports Server (NTRS)

Buchholz, Mark D.

1992-01-01

Wind tunnel tests were conducted on two devices for the purpose of lift augmentation on a 60 deg delta wing at low speed. Lift, drag, pitching moment, and surface pressures were measured. Detailed flow visualization was also obtained. Both the leading edge fence and the Gurney flap are shown to increase lift. The fences and flap shift the lift curve as much as 5 deg and 10 deg, respectively. The fences aid in trapping vortices on the upper surface, thereby increasing suction. The Gurney flap improves circulation at the trailing edge. The individual influences of both devices are roughly additive, creating high lift gain. However, the lower lift to drag ratio and the precipitation of vortex burst caused by the fences, and the nose down pitching moment created by the flap are also significant factors.

Experimental Investigation of Roughness Effects on Transition Onset and Turbulent Heating Augmentation on a Hemisphere at Mach 6 and Mach 10

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

2017-01-01

An experimental investigation of the effects of distributed surface roughness on boundary-layer transition and turbulent heating has been conducted. Hypersonic wind tunnel testing was performed using hemispherical models with surface roughness patterns simulating those produced by heat shield ablation. Global aeroheating and transition onset data were obtained using phosphor thermography at Mach 6 and Mach 10 over a range of roughness heights and free stream Reynolds numbers sufficient to produce laminar, transitional and turbulent flow. Upstream movement of the transition onset location and increasing heating augmentation over predicted smooth-wall levels were observed with both increasing roughness heights and increasing free stream Reynolds numbers. The experimental heating data are presented herein, as are comparisons to smooth-wall heat transfer distributions from computational flow-field simulations. The transition onset data are also tabulated, and correlations of these data are presented.

A Tunable Terahertz Detector based on Self-Assembled Plasmonic Structure on a GaAs 2-Dimensional Electron Gas

NASA Astrophysics Data System (ADS)

Biradar, Anandrao Shesherao

The presented work in this report is about Real time Estimation of wind and analyzing current wind correction algorithm in commercial off the shelf Autopilot board. The open source ArduPilot Mega 2.5 (APM 2.5) board manufactured by 3D Robotics is used. Currently there is lot of development being done in the field of Unmanned Aerial Systems (UAVs), various aerial platforms and corresponding; autonomous systems for them. This technology has advanced to such a stage that UAVs can be used for specific designed missions and deployed with reliability. But in some areas like missions requiring high maneuverability with greater efficiency is still under research area. This would help in increasing reliability and augmenting range of UAVs significantly. One of the problems addressed through this thesis work is, current autopilot systems have algorithm that handles wind by attitude correction with appropriate Crab angle. But the real time wind vector (direction) and its calculated velocity is based on geometrical and algebraic transformation between ground speed and air speed vectors. This method of wind estimation and prediction, many a times leads to inaccuracy in attitude correction. The same has been proved in the following report with simulation and actual field testing. In later part, new ways to tackle while flying windy conditions have been proposed.

Development of a short length combustor for a supersonic cruise turbofan engine using a 90 deg sector of a full annulus

NASA Technical Reports Server (NTRS)

Clements, T. R.

1972-01-01

A performance development program has been conducted on a short length, double-annular, ram-induction combustor. The combustor was designed for a large augmented turbofan engine capable of sustained flight speeds up to Mach 3.0. Performance tests were conducted at an inlet temperature and Mach number simulating engine sea level takeoff conditions. At the design temperature rise of 1600 F, combustion efficiency was 100%, pattern factor was 0.20, and combined diffuser-combustor pressure loss was 4.4% or 1.12 times the diffuser inlet velocity head. A temperature rise in excess of 2400 F with a combustion efficiency of 94% was demonstrated.

The calculation of transport properties in quantum liquids using the maximum entropy numerical analytic continuation method: Application to liquid para-hydrogen

PubMed Central

Rabani, Eran; Reichman, David R.; Krilov, Goran; Berne, Bruce J.

2002-01-01

We present a method based on augmenting an exact relation between a frequency-dependent diffusion constant and the imaginary time velocity autocorrelation function, combined with the maximum entropy numerical analytic continuation approach to study transport properties in quantum liquids. The method is applied to the case of liquid para-hydrogen at two thermodynamic state points: a liquid near the triple point and a high-temperature liquid. Good agreement for the self-diffusion constant and for the real-time velocity autocorrelation function is obtained in comparison to experimental measurements and other theoretical predictions. Improvement of the methodology and future applications are discussed. PMID:11830656

Taylor dispersion in wind-driven current

NASA Astrophysics Data System (ADS)

Li, Gang; Wang, Ping; Jiang, Wei-Quan; Zeng, Li; Li, Zhi; Chen, G. Q.

2017-12-01

Taylor dispersion associated with wind-driven currents in channels, shallow lakes and estuaries is essential to hydrological environmental management. For solute dispersion in a wind-driven current, presented in this paper is an analytical study of the evolution of concentration distribution. The concentration moments are intensively derived for an accurate presentation of the mean concentration distribution, up to the effect of kurtosis. The vertical divergence of concentration is then deduced by Gill's method of series expansion up to the fourth order. Based on the temporal evolution of the vertical concentration distribution, the dispersion process in the wind-driven current is concretely characterized. The uniform shear leads to a special symmetrical distribution of mean concentration free of skewness. The non-uniformity of vertical concentration is caused by convection and smeared out gradually by the effect of diffusion, but fails to disappear even at large times.

Nebula Models of Non-Equilibrium Mineralogy: Wark-Lovering Rims

NASA Technical Reports Server (NTRS)

Cuzzi, J. N.; Petaev, M.; Krot, A. N.

2005-01-01

Introduction: The meteorite record contains several examples of minerals that would not persist if allowed to come to equilibrium with a cooling gas of solar composition. This includes all minerals in CAIs and AOAs. Their survival is generally ascribed to physical removal of the object from the gas (isolation into a large parent object, or ejection by a stellar wind), but could also result from outward radial diffusion into cooler regions, which we discuss here. Accretion of CAIs into planetesimals has also been relied on to preserve them against loss into the sun. However, this suggestion faces several objections. Simple outward diffusion in turbulence has recently been modeled in some detail, and can preserve CAIs against loss into the sun [2]. Naturally, outward radial diffusion in turbulence is slower than immediate ejection by a stellar wind, which occurs on an orbital timescale. Here we ask whether these different transport mechanisms can be distinguished by nonequilibrium mineralogy, which provides a sort of clock. Our application here is to one aspect of CAI mineralogy - the Wark-Lovering rims (WLR); even more specifically, to alteration of one layer in the WLR sequence from melilite (Mel) to anorthite (An).

A search for thermospheric composition perturbations due to vertical winds

NASA Astrophysics Data System (ADS)

Krynicki, Matthew P.

The thermosphere is generally in hydrostatic equilibrium, with winds blowing horizontally along stratified constant-pressure surfaces, driven by the dayside-to-nightside pressure gradient. A marked change in this paradigm resulted after Spencer et al. [1976] reported vertical wind measurements of 80 m·s-1 from analyses of AE-C satellite data. It is now established that the thermosphere routinely supports large-magnitude (˜30-150 m·s-1) vertical winds at auroral latitudes. These vertical winds represent significant departure from hydrostatic and diffusive equilibrium, altering locally---and potentially globally---the thermosphere's and ionosphere's composition, chemistry, thermodynamics and energy budget. Because of their localized nature, large-magnitude vertical wind effects are not entirely known. This thesis presents ground-based Fabry-Perot Spectrometer OI(630.0)-nm observations of upper-thermospheric vertical winds obtained at Inuvik, NT, Canada and Poker Flat, AK. The wind measurements are compared with vertical displacement estimates at ˜104 km2 horizontal spatial scales determined from a new modification to the electron transport code of Lummerzheim and Lilensten [1994] as applied to FUV-wavelength observations by POLAR spacecraft's Ultraviolet Imager [Torr et al. , 1995]. The modification, referred to as the column shift, simulates vertical wind effects such as neutral transport and disruption of diffusive equilibrium by vertically displacing the Hedin [1991] MSIS-90 [O2]/[N2] and [O]/([N2]+[O2]) mixing ratios and subsequently redistributing the O, O2, and N 2 densities used in the transport code. Column shift estimates are inferred from comparisons of UVI OI(135.6)-nm auroral observations to their corresponding modeled emission. The modeled OI(135.6)-nm brightness is determined from the modeled thermospheric response to electron precipitation and estimations of the energy flux and characteristic energy of the precipitation, which are inferred from UVI-observed Lyman-Birge-Hopfield N2 emissions in two wavelength ranges. Two-dimensional column shift maps identify the spatial morphology of thermospheric composition perturbations associated with auroral forms relative to the model thermosphere. Case-study examples and statistical analyses of the column shift data sets indicate that column shifts can be attributed to vertical winds. Unanticipated limitations associated with modeling of the OI(135.6)-nm auroral emission make absolute column shift estimates indeterminate. Insufficient knowledge of thermospheric air-parcel time histories hinders interpretations of point-to-point time series comparisons between column shifts and vertical winds.

Reconstruction of stochastic temporal networks through diffusive arrival times

NASA Astrophysics Data System (ADS)

Li, Xun; Li, Xiang

2017-06-01

Temporal networks have opened a new dimension in defining and quantification of complex interacting systems. Our ability to identify and reproduce time-resolved interaction patterns is, however, limited by the restricted access to empirical individual-level data. Here we propose an inverse modelling method based on first-arrival observations of the diffusion process taking place on temporal networks. We describe an efficient coordinate-ascent implementation for inferring stochastic temporal networks that builds in particular but not exclusively on the null model assumption of mutually independent interaction sequences at the dyadic level. The results of benchmark tests applied on both synthesized and empirical network data sets confirm the validity of our algorithm, showing the feasibility of statistically accurate inference of temporal networks only from moderate-sized samples of diffusion cascades. Our approach provides an effective and flexible scheme for the temporally augmented inverse problems of network reconstruction and has potential in a broad variety of applications.

Modeling Demic and Cultural Diffusion: An Introduction.

PubMed

Fort, Joaquim; Crema, Enrico R; Madella, Marco

2015-07-01

Identifying the processes by which human cultures spread across different populations is one of the most topical objectives shared among different fields of study. Seminal works have analyzed a variety of data and attempted to determine whether empirically observed patterns are the result of demic and/or cultural diffusion. This special issue collects articles exploring several themes (from modes of cultural transmission to drivers of dispersal mechanisms) and contexts (from the Neolithic in Europe to the spread of computer programming languages), which offer new insights that will augment the theoretical and empirical basis for the study of demic and cultural diffusion. In this introduction we outline the state of art in the modeling of these processes, briefly discuss the pros and cons of two of the most commonly used frameworks (equation-based models and agent-based models), and summarize the significance of each article in this special issue.

Reconstruction of stochastic temporal networks through diffusive arrival times

PubMed Central

Li, Xun; Li, Xiang

2017-01-01

Temporal networks have opened a new dimension in defining and quantification of complex interacting systems. Our ability to identify and reproduce time-resolved interaction patterns is, however, limited by the restricted access to empirical individual-level data. Here we propose an inverse modelling method based on first-arrival observations of the diffusion process taking place on temporal networks. We describe an efficient coordinate-ascent implementation for inferring stochastic temporal networks that builds in particular but not exclusively on the null model assumption of mutually independent interaction sequences at the dyadic level. The results of benchmark tests applied on both synthesized and empirical network data sets confirm the validity of our algorithm, showing the feasibility of statistically accurate inference of temporal networks only from moderate-sized samples of diffusion cascades. Our approach provides an effective and flexible scheme for the temporally augmented inverse problems of network reconstruction and has potential in a broad variety of applications. PMID:28604687

Combined effect of boundary layer recirculation factor and stable energy on local air quality in the Pearl River Delta over southern China.

PubMed

Li, Haowen; Wang, Baomin; Fang, Xingqin; Zhu, Wei; Fan, Qi; Liao, Zhiheng; Liu, Jian; Zhang, Asi; Fan, Shaojia

2018-03-01

Atmospheric boundary layer (ABL) has a significant impact on the spatial and temporal distribution of air pollutants. In order to gain a better understanding of how ABL affects the variation of air pollutants, atmospheric boundary layer observations were performed at Sanshui in the Pearl River Delta (PRD) region over southern China during the winter of 2013. Two types of typical ABL status that could lead to air pollution were analyzed comparatively: weak vertical diffusion ability type (WVDAT) and weak horizontal transportation ability type (WHTAT). Results show that (1) WVDAT was featured by moderate wind speed, consistent wind direction, and thick inversion layer at 600~1000 m above ground level (AGL), and air pollutants were restricted in the low altitudes due to the stable atmospheric structure; (2) WHTAT was characterized by calm wind, varied wind direction, and shallow intense ground inversion layer, and air pollutants accumulated in locally because of strong recirculation in the low ABL; (3) recirculation factor (RF) and stable energy (SE) were proved to be good indicators for horizontal transportation ability and vertical diffusion ability of the atmosphere, respectively. Combined utilization of RF and SE can be very helpful in the evaluation of air pollution potential of the ABL. Air quality data from ground and meteorological data collected from radio sounding in Sanshui in the Pearl River Delta showed that local air quality was poor when wind reversal was pronounced or temperature stratification state was stable. The combination of horizontal and vertical transportation ability of the local atmosphere should be taken into consideration when evaluating local environmental bearing capacity for air pollution.

Low-Temperature Thermochronology of Borehole and Surface Samples From the Wind River and Beartooth Laramide Ranges, Wyoming and Montana, USA

NASA Astrophysics Data System (ADS)

Peyton, S. L.; Reiners, P. W.

2007-12-01

We dated borehole and surface samples from the Wind River and Beartooth Laramide-age, basement-cored uplifts of the Rocky Mountain foreland using the apatite (U-Th)/He (AHe) system. Comparison of these results to previously published apatite fission-track (AFT) data along with the incorporation of new He diffusion models (Shuster et al., 2006), reveals several new insights into, and poses new interpretational challenges for, the shallow exhumation histories of these ranges. Deep (2.2-2.8 km below surface) borehole samples from the Wind River Range have AHe ages of 9-12 Ma, and suggest at least 600 m of rapid exhumation during the Miocene. Shallower samples range from 35-66 Ma and are consistent with exhumation of a fossil partial retention zone. Previously-published apatite fission track (AFT) data from the same borehole show at least 2 km of rapid exhumation at ~45-38 Ma at depths where AHe ages are 9-50 Ma. This contrasts with the AHe ages which show slow exhumation between 12-66 Ma and have a trend on an age-elevation plot that appears to cut across the AFT age trend. Forward modeling of the cooling ages of these data using well-constrained thermal histories and conventional Durango apatite He diffusion data cannot explain these coupled AFT-AHe age-elevation relationships. However, modeling using diffusion kinetics of the Shuster et al. radiation-damage trapping model can explain the observed age trends, including the apparent presence of a 45-38 Ma exhumation event in the AFT data and its absence in the AHe data. In the model the shallow samples do not reach high enough temperatures for annealing of accumulated radiation damage, so He is trapped and ages are much older than predicted by conventional diffusion models. Previously-published AFT data from the Beartooth Range also show a large Laramide-age exhumation event, dated at 57-52 Ma. Similar to our observations from the Wind River Range, this event is not represented in our AHe results from borehole samples, which instead show slow cooling between at least 63-10 Ma. The trapping model predicts that the observed AHe age of a single apatite grain will be proportional to its effective Uranium content (eU), a proxy for radiation damage. Multiple single-grain replicates from a sample from the Wind River borehole are consistent with this, showing a strong correlation with eU. Although the trapping-diffusion model explains the coupled AFT-AHe data of borehole samples, surface samples from the Fremont Peak area in the Wind River Range have AHe ages that are older than the corresponding previously-published AFT ages over the 1.2 km elevation traverse sampled. AFT ages show ~1 km of rapid exhumation at ~62-58 Ma; corresponding AHe ages are as much as 20 Myr older. Although the radiation damage trapping model predicts that some AHe ages may be older than the corresponding AFT ages, thermal- diffusion forward models cannot explain these large age differences over such a large sampling interval, even if trapping model kinetic parameters are varied by 5%. Thus, discrepancies in AFT and AHe ages of these surficial samples remain problematic. The thermal histories required to approximate the borehole data require burial up to the end of the Cretaceous of ~3-4 km followed by at least two phases of cooling and exhumation. The first and larger cooling event of several tens of degrees (~3-4 km of exhumation) occurred during the Paleocene-Eocene, followed by a smaller cooling event of a few tens of degrees (~1 km of exhumation) during the Miocene.

Shelf-Slope Exchanges near Submarine Canyons in the Southern Mid-Atlantic Bight

NASA Astrophysics Data System (ADS)

Wang, H.; Gong, D.

2016-02-01

Shelf-slope exchange processes are major physical drivers of biological productivity near the shelf-break. Observations from two Slocum ocean gliders in Fall 2013 are used to explore the driving mechanisms of cross-shelf-slope exchanges near Norfolk Canyon and Washington Canyon in the southern Mid-Atlantic Bight. Offshore excursion of bottom "cold pool" water, and shoreward intrusion of slope water at surface layer and thermocline depth occurred during northeasterly along-shelf winds. The saline intrusions of surface slope water resided between the cold pool and surface shelf water, and reached the bottom on the outer and mid-shelf, while the offshore excursion of cold pool water was found between the surface and intermediate slope-water over the canyon. Ekman transport calculation shows wind-driven cross-shelf transport can partially explain this interleaving pattern of intrusions. Scaling analysis of double diffusive processes demonstrate that they also likely played a role in the cross-shelf-slope exchange. A unique canyon upwelling event was captured in and around Washington Canyon during a period of southwesterly along-shelf wind and along-shelf flow to the northeast. The water mass distributions and isopycnal responses in both along-canyon and cross-canyon transects are consistent with scaling analysis and numerical studies of canyon upwelling. Temperature-Salinity properties of water masses in the canyon suggest active mixing between shelf and slope water masses near the canyon head. These results point to the importance of wind, double diffusion, and canyon topography on shelf-slope exchange in the MAB.

A study of space shuttle plumes in the lower thermosphere

NASA Astrophysics Data System (ADS)

Meier, R. R.; Stevens, Michael H.; Plane, John M. C.; Emmert, J. T.; Crowley, G.; Azeem, I.; Paxton, L. J.; Christensen, A. B.

2011-12-01

During the space shuttle main engine burn, some 350 t of water vapor are deposited at between 100 and 115 km. Subsequent photodissociation of water produces large plumes of atomic hydrogen that can expand rapidly and extend for thousands of kilometers. From 2002 to 2007, the Global Ultraviolet Imager (GUVI) on NASA's Thermosphere Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite imaged many of these hydrogen plumes at Lyman α (121.567 nm) while viewing in the nadir. The images reveal rapid plume expansion and occasional very fast transport to both north and south polar regions. Some plumes persist for up to 6 d. Near-simultaneous direct detections of water vapor were made with the Sounding of the Atmosphere with Broadband Emission Radiometry (SABER) instrument, also on TIMED. We compare the spreading of the hydrogen plume with a two-dimensional model that includes photodissociation as well as both vertical and horizontal diffusion. Molecular diffusion appears to be sufficient to account for the horizontal expansion, although wind shears and turbulent mixing may also contribute. We compare the bulk motion of the observed plumes with wind climatologies derived from satellite observations. The plumes can move much faster than predictions of wind climatologies. But dynamical processes not contained in wind climatologies, such as the quasi-two-day wave, can account for at least some of the high speed observations. The plume phenomena raise a number of important questions about lower thermospheric and mesospheric processes, ranging from dynamics and chemistry to polar mesospheric cloud formation and climatology.

Patterns of weak, near-surface winds at Melbourne, Australia

NASA Astrophysics Data System (ADS)

Tapp, R. G.

1985-12-01

Up to 30 months of near-surface anemograph records have been examined from 13 locations in and near Melbourne, Australia, to determine the wind patterns which existed during prolonged periods of light winds (at least 3 hours at 2 m s-1 or less). A coherent katabatic wind system was found to develop in at least part of the monitored region on approximately 30% of nights. The flow broadly followed the slope of the basin surrounding the city, with a strong flow down the main river valley, and was partly reinforced by a land breeze in bayside areas. Other valleys also acted as channels for these winds. The general tendency of these katabatic winds was to converge towards the central business district and the northern part of Port Phillip Bay adjacent to the city centre. Where winds from different directions interacted, one of the winds dominated or successive replacement occurred causing the wind direction to vary considerably during a period. There were indications that in the presence of low-level stability with a synoptic gradient wind between east and north, the gradient flow may be deflected around the major topographic barrier to the northeast of the city. The existence of such a situation would have major implications in terms of air quality due to the possibility of pollutants being recirculated in conditions when vertical diffusion was very limited.

ACTIVE GALACTIC NUCLEUS OBSCURATION FROM WINDS: FROM DUSTY INFRARED-DRIVEN TO WARM AND X-RAY PHOTOIONIZED

PubMed Central

Dorodnitsyn, A.; Kallman, T.

2016-01-01

We present calculations of AGN winds at ~parsec scales, along with the associated obscuration. We take into account the pressure of infrared radiation on dust grains and the interaction of X-rays from a central black hole with hot and cold plasma. Infrared radiation (IR) is incorporated in radiation-hydrodynamic simulations adopting the flux-limited diffusion approximation. We find that in the range of X-ray luminosities L=0.05 – 0.6Ledd, the Compton-thick part of the flow (aka torus) has an opening angle of approximately 72° – 75° regardless of the luminosity. At L ≳ 0.1 the outflowing dusty wind provides the obscuration with IR pressure playing a major role. The global flow consists of two phases: the cold flow at inclinations θ ≳ 70° and a hot, ionized wind of lower density at lower inclinations. The dynamical pressure of the hot wind is important in shaping the denser IR supported flow. At luminosities ≤0.1Ledd episodes of outflow are followed by extended periods when the wind switches to slow accretion. PMID:27642184

Indispensable finite time corrections for Fokker-Planck equations from time series data.

PubMed

Ragwitz, M; Kantz, H

2001-12-17

The reconstruction of Fokker-Planck equations from observed time series data suffers strongly from finite sampling rates. We show that previously published results are degraded considerably by such effects. We present correction terms which yield a robust estimation of the diffusion terms, together with a novel method for one-dimensional problems. We apply these methods to time series data of local surface wind velocities, where the dependence of the diffusion constant on the state variable shows a different behavior than previously suggested.

Can molecular diffusion explain Space Shuttle plume spreading?

NASA Astrophysics Data System (ADS)

Meier, R. R.; Plane, John M. C.; Stevens, Michael H.; Paxton, L. J.; Christensen, A. B.; Crowley, G.

2010-04-01

The satellite-borne Global Ultraviolet Imager (GUVI) has produced more than 20 images of NASA Space Shuttle main engine plumes in the lower thermosphere. These reveal atomic hydrogen and, by inference, water vapor transport over hemispherical-scale distances with speeds much faster than expected from models of thermospheric wind motions. Furthermore, the hydrogen plumes expand rapidly. We find rates that exceed the horizontal diffusion speed at nominal plume altitudes of 104-112 km. Kelley et al. (2009) have proposed a 2-D turbulence mechanism to explain the observed spreading rates (and rapid advection) of the plumes. But upon further investigation, we conclude that H atom diffusion can indeed account for the observed expansion rates by recognizing that vertical diffusion quickly conveys atoms to higher altitudes where horizontal diffusion is much more rapid. We also find evidence for H atom production directly during the Shuttle's main engine burn.

An experimental evaluation of S-duct inlet-diffuser configurations for turboprop offset gearbox applications

NASA Technical Reports Server (NTRS)

Mcdill, Paul L.

1986-01-01

A test program, utilizing a large scale model, was run in the NASA Lewis Research Center 10- by 10-ft wind tunnel to examine the influence on performance of design parameters of turboprop S-duct inlet/diffuser systems. The parametric test program investigated inlet lip thickness, inlet/diffuser cross-sectional geometry, throat design Mach number, and shaft fairing shape. The test program was run at angles of attack to 15 deg and tunnel Mach numbers to 0.35. Results of the program indicate that current design techniques can be used to design inlet/diffuser systems with acceptable total pressure recovery, but several of the design parameters, notably lip thickness (contraction ratio) and shaft fairing cross section, must be optimized to prevent excessive distortion at the compressor face.

Depletion of solar wind plasma near a planetary boundary

NASA Technical Reports Server (NTRS)

Zwan, B. J.; Wolf, R. A.

1976-01-01

A mathematical model is presented that describes the squeezing of solar wind plasma out along interplanetary magnetic field lines in the region between the bow shock and the effective planetary boundary (in the case of the earth, the magnetopause). In the absence of local magnetic merging the squeezing process should create a 'depletion layer', a region of very low plasma density just outside the magnetopause. Numerical solutions are obtained for the dimensionless magnetohydrodynamic equations describing this depletion process for the case where the solar wind magnetic field is perpendicular to the solar wind flow direction. For the case of the earth, the theory predicts that the density should be reduced by a factor exceeding 2 in a layer about 700-1300 km thick if the Alfven Mach number in the solar wind, is equal to 8. Scaling of the model calculations to Venus and Mars suggests layer thicknesses about 1/10 and 1/15 those of the earth, respectively, neglecting diffusion and ionospheric effects.

Implementation and Validation of the Chien k-epsilon Turbulence Model in the Wind Navier-Stokes Code

NASA Technical Reports Server (NTRS)

Yoder, Dennis A.; Georgiadis, Nicholas J.

1999-01-01

The two equation k-epsilon turbulence model of Chien has been implemented in the WIND Navier-Stokes flow solver. Details of the numerical solution algorithm, initialization procedure, and stability enhancements are described. Results obtained with this version of the model are compared with those from the Chien k-epsilon model in the NPARC Navier-Stokes code and from the WIND SST model for three validation cases: the incompressible flow over a smooth flat plate, the incompressible flow over a backward facing step, and the shock-induced flow separation inside a transonic diffuser. The k-epsilon model results indicate that the WIND model functions very similarly to that in NPARC, though the WIND code appears to he slightly more accurate in the treatment of the near-wall region. Comparisons of the k-epsilon model results with those from the SST model were less definitive, as each model exhibited strengths and weaknesses for each particular case.

Development of the NASA-Ames low disturbance supersonic wind tunnel for transition research up to Mach 2.5

NASA Technical Reports Server (NTRS)

Wolf, Stephen W. D.; Laub, James A.; King, Lyndell S.; Reda, Daniel C.

1992-01-01

A unique, low-disturbance supersonic wind tunnel is being developed at NASA-Ames to support supersonic laminar flow control research at cruise Mach numbers of the High Speed Civil Transport (HSCT). The distinctive aerodynamic features of this new quiet tunnel will be a low-disturbance settling chamber, laminar boundary layers on the nozzle walls and steady supersonic diffuser flow. Furthermore, this new wind tunnel will operate continuously at uniquely low compression ratios (less than unity). This feature allows an existing non-specialist compressor to be used as a major part of the drive system. In this paper, we highlight activities associated with drive system development, the establishment of natural laminar flow on the test section walls, and instrumentation development for transition detection. Experimental results from an 1/8th-scale model of the supersonic wind tunnel are presented and discussed in association with theoretical predictions. Plans are progressing to build the full-scale wind tunnel by the end of 1993.

Progress Report for the Joint Services Electronics Program

DTIC Science & Technology

1991-06-30

AIGaAs MODFET layers. Both wet etching and reactive ion etching have been used to fabricate the channels. The CAIBE method will also be investigated in...potential for fabricating nanometer scale device structures through surface modification of various types. Using this JSEP research as a foundation...Kerkhoven, "Calculation of velocity overshoot in submicron devices using an augmented drift-diffusion model," Solid-State Electron. (to appear). (JSEP/NSF

Space Shuttle Main Engine structural analysis and data reduction/evaluation. Volume 6: Primary nozzle diffuser analysis

NASA Technical Reports Server (NTRS)

Foley, Michael J.

1989-01-01

The primary nozzle diffuser routes fuel from the main fuel valve on the Space Shuttle Main Engine (SSME) to the nozzle coolant inlet mainfold, main combustion chamber coolant inlet mainfold, chamber coolant valve, and the augmented spark igniters. The diffuser also includes the fuel system purge check valve connection. A static stress analysis was performed on the diffuser because no detailed analysis was done on this part in the past. Structural concerns were in the area of the welds because approximately 10 percent are in areas inaccessible by X-ray testing devices. Flow dynamics and thermodynamics were not included in the analysis load case. Constant internal pressure at maximum SSME power was used instead. A three-dimensional, finite element method was generated using ANSYS version 4.3A on the Lockheed VAX 11/785 computer to perform the stress computations. IDEAS Supertab on a Sun 3/60 computer was used to create the finite element model. Rocketdyne drawing number RS009156 was used for the model interpretation. The flight diffuser is denoted as -101. A description of the model, boundary conditions/load case, material properties, structural analysis/results, and a summary are included for documentation.

Designing for diffusion: how can we increase uptake of cancer communication innovations?

PubMed

Dearing, James W; Kreuter, Matthew W

2010-12-01

The best innovations in cancer communication do not necessarily achieve uptake by researchers, public health and clinical practitioners, and policy makers. This paper describes design activities that can be applied and combined for the purpose of spreading effective cancer communication innovations. A previously developed Push-Pull-Infrastructure Model is used to organize and highlight the types of activities that can be deployed during the design phase of innovations. Scientific literature about the diffusion of innovations, knowledge utilization, marketing, public health, and our experiences in working to spread effective practices, programs, and policies are used for this purpose. Attempts to broaden the reach, quicken the uptake, and facilitate the use of cancer communication innovations can apply design activities to increase the likelihood of diffusion. Some simple design activities hold considerable promise for improving dissemination and subsequent diffusion. Augmenting current dissemination practices with evidence-based concepts from diffusion science, marketing science, and knowledge utilization hold promise for improving results by eliciting greater market pull. Inventors and change agencies seeking to spread cancer communication innovations can experience more success by explicit consideration of design activities that reflect an expanded version of the Push-Pull-Infrastructure Model. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Designing for Diffusion: How Can We Increase Uptake of Cancer Communication Innovations?

PubMed Central

Dearing, James W.; Kreuter, Matthew W.

2010-01-01

Objective The best innovations in cancer communication do not necessarily achieve uptake by researchers, public health and clinical practitioners, and policy makers. This paper describes design activities that can be applied and combined for the purpose of spreading effective cancer communication innovations. Methods A previously developed Push-Pull-Infrastructure Model is used to organize and highlight the types of activities that can be deployed during the design phase of innovations. Scientific literature about the diffusion of innovations, knowledge utilization, marketing, public health, and our experiences in working to spread effective practices, programs, and policies are used for this purpose. Results Attempts to broaden the reach, quicken the uptake, and facilitate the use of cancer communication innovations can apply design activities to increase the likelihood of diffusion. Some simple design activities hold considerable promise for improving dissemination and subsequent diffusion. Conclusion Augmenting current dissemination practices with evidence-based concepts from diffusion science, marketing science, and knowledge utilization hold promise for improving results by eliciting greater market pull. Practice Implications Inventors and change agencies seeking to spread cancer communication innovations can experience more success by explicit consideration of design activities that reflect an expanded version of the Push-Pull-Infrastructure Model. PMID:21067884

Mechanisms of Ocean Heat Uptake

NASA Astrophysics Data System (ADS)

Garuba, Oluwayemi

An important parameter for the climate response to increased greenhouse gases or other radiative forcing is the speed at which heat anomalies propagate downward in the ocean. Ocean heat uptake occurs through passive advection/diffusion of surface heat anomalies and through the redistribution of existing temperature gradients due to circulation changes. Atlantic meridional overturning circulation (AMOC) weakens in a warming climate and this should slow the downward heat advection (compared to a case in which the circulation is unchanged). However, weakening AMOC also causes a deep warming through the redistributive effect, thus increasing the downward rate of heat propagation compared to unchanging circulation. Total heat uptake depends on the combined effect of these two mechanisms. Passive tracers in a perturbed CO2 quadrupling experiments are used to investigate the effect of passive advection and redistribution of temperature anomalies. A new passive tracer formulation is used to separate ocean heat uptake into contributions due to redistribution and passive advection-diffusion of surface heating during an ocean model experiment with abrupt increase in surface temperature. The spatial pattern and mechanisms of each component are examined. With further experiments, the effects of surface wind, salinity and temperature changes in changing circulation and the resulting effect on redistribution in the individual basins are isolated. Analysis of the passive advection and propagation path of the tracer show that the Southern ocean dominates heat uptake, largely through vertical and horizontal diffusion. Vertical diffusion transports the tracer across isopycnals down to about 1000m in 100 years in the Southern ocean. Advection is more important in the subtropical cells and in the Atlantic high latitudes, both with a short time scale of about 20 years. The shallow subtropical cells transport the tracer down to about 500m along isopycnal surfaces, below this vertical diffusion takes over transport in the tropics; in the Atlantic, the MOC transports heat as deep 2000m in about 30 years. Redistributive surface heat uptake alters the total amount surface heat uptake among the basins. Compared to the passive-only heat uptake, which is about the same among the basins, redistribution nearly doubles the surface heat input into the Atlantic but makes smaller increases in the Indian and Pacific oceans for a net global increase of about 25%, in the perturbation experiment with winds unchanged. The passive and redistributive heat uptake components are further distributed among the basins through the global conveyor belt. The Pacific gains twice the surface heat input into it through lateral transport from the other two basins, as a result, the Atlantic and Pacific gain similar amounts of heat even though surface heat input is in the Atlantic is much bigger. Of this heat transport, most of the passive component comes from the Indian and the redistributive component comes from the Atlantic. Different surface forcing perturbation gives different circulation change pattern and as a result yield different redistributive uptake. Ocean heat uptake is more sensitive to wind forcing perturbation than to thermohaline forcing perturbation. About 2% reduction in subtropical cells transport and southern ocean transport, in the wind-change perturbation experiment, resulted in about 10% reduction in the global ocean heat uptake of wind-unchanged experiment. The AMOC weakened by about 35% and resulted in a 25% increase in passive heat uptake in the wind-unchanged experiment. Surface winds weakening reduces heat uptake by warming the reservoir surface temperatures, while MOC weakening increases heat input by a cooling reservoir surface temperatures. Thermohaline forcing perturbation is combination of salinity and temperature perturbations, both weaken the AMOC, however, they have opposite redistributive effects. Ocean surface freshening gives positive redistributive effect, while surface temperature increase gives negative redistributive effect on heat uptake. The salinity effect dominates the redistributive effect for thermohaline perturbation.

Computational analysis of vertical axis wind turbine arrays

NASA Astrophysics Data System (ADS)

Bremseth, J.; Duraisamy, K.

2016-10-01

Canonical problems involving single, pairs, and arrays of vertical axis wind turbines (VAWTs) are investigated numerically with the objective of understanding the underlying flow structures and their implications on energy production. Experimental studies by Dabiri (J Renew Sustain Energy 3, 2011) suggest that VAWTs demand less stringent spacing requirements than their horizontal axis counterparts and additional benefits may be obtained by optimizing the placement and rotational direction of VAWTs. The flowfield of pairs of co-/counter-rotating VAWTs shows some similarities with pairs of cylinders in terms of wake structure and vortex shedding. When multiple VAWTs are placed in a column, the extent of the wake is seen to spread further downstream, irrespective of the direction of rotation of individual turbines. However, the aerodynamic interference between turbines gives rise to regions of excess momentum between the turbines which lead to significant power augmentations. Studies of VAWTs arranged in multiple columns show that the downstream columns can actually be more efficient than the leading column, a proposition that could lead to radical improvements in wind farm productivity.

Hydraulic Characteristics of the Lower Snake River during Periods of Juvenile Fall Chinook Salmon Migration, 2002-2006 Final Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, C.; Dibrani, B.; Richmond, M.

2006-01-01

This report documents a four-year study to assess hydraulic conditions in the lower Snake River. The work was conducted for the Bonneville Power Administration, U.S. Department of Energy, by the Pacific Northwest National Laboratory. Cold water released from the Dworshak Reservoir hypolimnion during mid- to late-summer months cools the Clearwater River far below equilibrium temperature. The volume of released cold water augments the Clearwater River, and the combined total discharge is on the order of the Snake River discharge when the two rivers meet at their confluence near the upstream edge of Lower Granite Reservoir. With typical temperature differences betweenmore » the Clearwater and Snake rivers of 10 C or more during July and August, the density difference between the two rivers during summer flow augmentation periods is sufficient to stratify Lower Granite Reservoir as well as the other three reservoirs downstream. Because cooling of the river is desirable for migrating juvenile fall Chinook salmon (Oncorhynchus tshawytscha) during this same time period, the amount of mixing and cold water entrained into Lower Granite Reservoir's epilimnion at the Clearwater/Snake River confluence is of key biological importance. Data collected during this project indicates the three reservoirs downstream of Lower Granite also stratify as direct result of flow augmentation from Dworshak Reservoir. These four reservoirs are also heavily influenced by wind forcing at the water's surface and during periods of low river discharge often behave like a two-layer lake. During these periods of stratification, lower river discharge, and wind forcing, the water in the upper layer of the reservoir is held in place or moves slightly upstream. This upper layer is also exposed to surface heating and may warm up to temperatures close to equilibrium temperature. The thickness (depth) of this upper warm layer and its direction of travel may be of key biological importance to juvenile fall Chinook salmon. This report describes field data collection, modeling, and analysis of hydrodynamic and temperature conditions in the Lower Granite Reservoir during the summer flow augmentation periods of 2002, 2003, and 2004. Although temperature, and hence density, differences during flow augmentation periods between the Clearwater and Snake rivers were approximately equal (7-12 C) for all four years, the discharge ratio varied which resulted in significant differences in entrainment of cooler Clearwater River water into the Lower Granite Reservoir epilimnion. However, as a direct result of system management, Lower Granite Dam tailrace temperatures were maintained near 20 C during all years. Primary differences in the other three lower Snake River reservoirs were therefore a result of meteorological conditions and dam operations, which produced variations in wind setup and surface heating. Circulation patterns in all four lower Snake River reservoirs were numerically simulated for periods of 2002, 2003, 2004, and 2005 using CE-QUAL-W2. Simulation results show that these models are capable of matching diurnal and long-term temperature and velocity changes in the reservoirs. In addition, the confluence zone of the Clearwater and Snake rivers was modeled using the three-dimensional non-hydrostatic model Flow3D. Once calibrated and validated, the reservoir models were used to investigate downstream impacts of alternative reservoir operation schemes, such as increasing or decreasing the ratio of Clearwater to Snake river discharge. Simulation results were linked with the particle tracking model FINS to develop reservoir-integrated metrics that varied due to these alternative operation schemes. Findings indicate that significant alterations in water temperature throughout the lower Snake River are possible by altering hypolimnetic discharges from Dworshak Reservoir, which may also impact the behavior of migrating juvenile fall Chinook salmon during periods of flow augmentation.« less

Geomorphic Effects of Gravel Augmentation and Bank Re-erosion on the Old Rhine River Downstream From The Kembs Dam (France, Germany)

NASA Astrophysics Data System (ADS)

Chardon, V.; Laurent, S.; Piegay, H.; Arnaud, F.; Houssier, J.; Serouilou, J.; Clutier, A.

2017-12-01

The Old Rhine is a 50 km by-passed reach downstream from the Kembs diversion dam in the Alsacian plain (France/Germany). It has been impacted by engineering works since the 19th century. This reach exhibits poor ecological functionalities due to severe geomorphological alterations (e.g., channel bed stabilization, narrowing, degradation and armoring, sediment deficit). In the frame of the Kembs power plant relicensing (2010), Électricité de France has undertaken two gravel augmentations (18 000 and 30 000 m3) and three controlled bank erosions following riprap protection removal over 300 m bank length to enhance bedload transport and habitat diversification. A first pilot gravel augmentation was also implemented in 2010 (23 000 m3). A geomorphological monitoring based on bedload tracking, grain size analyses and topo-bathymetric surveys has been performed on the three gravel augmentation reaches and one of the controlled bank erosion sites to assess the efficiency and sustainability of these actions (2010-2017). Results show that augmented gravels are entrained for a Q2 flood. Gravels moved several hundred meters for moderate floods and up to one kilometer for more intense floods (Q15), while sediment deposition mainly diffused within the channel. Morphological and grain size diversification, including sediment refinement, are still relatively limited following gravel augmentation. Furthermore, sediment armoring reestablished once the sediment wave moved more downstream, after only four to six years, due to the stability and the narrowness of the channel but also by the absence of upstream bedload supply. Habitat diversification was higher on the controlled bank erosion site thanks to the presence of two artificial groynes, even though eroded sediment volumes were lower than expected (less than 1500m3 for a Q15 flood). This monitoring demonstrates gravel augmentations are not sufficient to really diversify geomorphological conditions of the Old Rhine. Channel enlargements by controlled bank erosion and other actions should be carried out downstream from gravel augmentations to create channel geometry conditions promoting bar development and habitat diversification.

Carolina Offshore Wind Integration Case Study: Phases I and II Final Technical Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fallon, Christopher; Piper, Orvane; Hazelip, William

2015-04-30

Duke Energy performed a phase 1 study to assess the impact of offshore wind development in the waters off the coasts of North Carolina and South Carolina. The study analyzed the impacts to the Duke Energy Carolinas electric power system of multiple wind deployment scenarios. Focusing on an integrated utility system in the Carolinas provided a unique opportunity to assess the impacts of offshore wind development in a region that has received less attention regarding renewables than others in the US. North Carolina is the only state in the Southeastern United States that currently has a renewable portfolio standard (RPS)more » which requires that 12.5% of the state’s total energy requirements be met with renewable resources by 2021. 12.5% of the state’s total energy requirements in 2021 equates to approximately 17,000 GWH of energy needed from renewable resources. Wind resources represent one of the ways to potentially meet this requirement. The study builds upon and augments ongoing work, including a study by UNC to identify potential wind development sites and the analysis of impacts to the regional transmission system performed by the NCTPC, an Order 890 planning entity of which DEC is a member. Furthermore, because the region does not have an independent system operator (ISO) or regional transmission organization (RTO), the study will provide additional information unique to non-RTO/ISO systems. The Phase 2 study builds on the results of Phase 1 and investigates the dynamic stability of the electrical network in Task 4, the operating characteristics of the wind turbines as they impact operating reserve requirements of the DEC utility in Task 5, and the production cost of integrating the offshore wind resources into the DEC generation fleet making comparisons to future planned operation without the addition of the wind resources in Task 6.« less

Lateral diffusion of inositol 1,4,5-trisphosphate receptor type 1 in Purkinje cells is regulated by calcium and actin filaments.

PubMed

Fukatsu, Kazumi; Bannai, Hiroko; Inoue, Takafumi; Mikoshiba, Katsuhiko

2010-09-01

Inositol 1,4,5-trisphosphate receptor type 1 (IP(3) R1) is an intracellular Ca(2+) release channel that plays crucial roles in the functions of Purkinje cells. The dynamics of IP(3) R1 on the endoplasmic reticulum membrane and the distribution of IP(3) R1 in neurons are thought to be important for the spatial regulation of Ca(2+) release. In this study, we analyzed the lateral diffusion of IP(3) R1 in Purkinje cells in cerebellar slice cultures using fluorescence recovery after photobleaching. In the dendrites of Purkinje cells, IP(3) R1 showed lateral diffusion with an effective diffusion constant of approximately 0.30 μm(2) /s, and the diffusion of IP(3) R1 was negatively regulated by actin filaments. We found that actin filaments were also involved in the regulation of IP(3) R1 diffusion in the spine of Purkinje cells. Glutamate or quisqualic acid stimulation, which activates glutamate receptors and leads to a Ca(2+) transient in Purkinje cells, decreased the diffusion of IP(3) R1 and increased the density of actin in spines. These findings indicate that the neuronal activity-dependent augmentation of actin contributes to the stabilization of IP(3) R1 in spines. © 2010 The Authors. Journal Compilation © 2010 International Society for Neurochemistry.

Experimental damage detection of wind turbine blade using thin film sensor array

NASA Astrophysics Data System (ADS)

Downey, Austin; Laflamme, Simon; Ubertini, Filippo; Sarkar, Partha

2017-04-01

Damage detection of wind turbine blades is difficult due to their large sizes and complex geometries. Additionally, economic restraints limit the viability of high-cost monitoring methods. While it is possible to monitor certain global signatures through modal analysis, obtaining useful measurements over a blade's surface using off-the-shelf sensing technologies is difficult and typically not economical. A solution is to deploy dedicated sensor networks fabricated from inexpensive materials and electronics. The authors have recently developed a novel large-area electronic sensor measuring strain over very large surfaces. The sensing system is analogous to a biological skin, where local strain can be monitored over a global area. In this paper, we propose the utilization of a hybrid dense sensor network of soft elastomeric capacitors to detect, localize, and quantify damage, and resistive strain gauges to augment such dense sensor network with high accuracy data at key locations. The proposed hybrid dense sensor network is installed inside a wind turbine blade model and tested in a wind tunnel to simulate an operational environment. Damage in the form of changing boundary conditions is introduced into the monitored section of the blade. Results demonstrate the ability of the hybrid dense sensor network, and associated algorithms, to detect, localize, and quantify damage.

Towards uncovering the structure of power fluctuations of wind farms

NASA Astrophysics Data System (ADS)

Liu, Huiwen; Jin, Yaqing; Tobin, Nicolas; Chamorro, Leonardo P.

2017-12-01

The structure of the turbulence-driven power fluctuations in a wind farm is fundamentally described from basic concepts. A derived tuning-free model, supported with experiments, reveals the underlying spectral content of the power fluctuations of a wind farm. It contains two power-law trends and oscillations in the relatively low- and high-frequency ranges. The former is mostly due to the turbulent interaction between the flow and the turbine properties, whereas the latter is due to the advection between turbine pairs. The spectral wind-farm scale power fluctuations ΦP exhibit a power-law decay proportional to f-5 /3 -2 in the region corresponding to the turbulence inertial subrange and at relatively large scales, ΦP˜f-2 . Due to the advection and turbulent diffusion of large-scale structures, a spectral oscillation exists with the product of a sinusoidal behavior and an exponential decay in the frequency domain.

Towards uncovering the structure of power fluctuations of wind farms.

PubMed

Liu, Huiwen; Jin, Yaqing; Tobin, Nicolas; Chamorro, Leonardo P

2017-12-01

The structure of the turbulence-driven power fluctuations in a wind farm is fundamentally described from basic concepts. A derived tuning-free model, supported with experiments, reveals the underlying spectral content of the power fluctuations of a wind farm. It contains two power-law trends and oscillations in the relatively low- and high-frequency ranges. The former is mostly due to the turbulent interaction between the flow and the turbine properties, whereas the latter is due to the advection between turbine pairs. The spectral wind-farm scale power fluctuations Φ_{P} exhibit a power-law decay proportional to f^{-5/3-2} in the region corresponding to the turbulence inertial subrange and at relatively large scales, Φ_{P}∼f^{-2}. Due to the advection and turbulent diffusion of large-scale structures, a spectral oscillation exists with the product of a sinusoidal behavior and an exponential decay in the frequency domain.

Solution of the Fokker-Planck equation in a wind turbine array boundary layer

NASA Astrophysics Data System (ADS)

Melius, Matthew S.; Tutkun, Murat; Cal, Raúl Bayoán

2014-07-01

Hot-wire velocity signals from a model wind turbine array boundary layer flow wind tunnel experiment are analyzed. In confirming Markovian properties, a description of the evolution of the probability density function of velocity increments via the Fokker-Planck equation is attained. Solution of the Fokker-Planck equation is possible due to the direct computation of the drift and diffusion coefficients from the experimental measurement data which were acquired within the turbine canopy. A good agreement is observed in the probability density functions between the experimental data and numerical solutions resulting from the Fokker-Planck equation, especially in the far-wake region. The results serve as a tool for improved estimation of wind velocity within the array and provide evidence that the evolution of such a complex and turbulent flow is also governed by a Fokker-Planck equation at certain scales.

Plasma sheet density dependence on Interplanetary Magnetic Field and Solar Wind properties: statistical study using 9+ year of THEMIS data

NASA Astrophysics Data System (ADS)

Nykyri, K.; Chu, C.; Dimmock, A. P.

2017-12-01

Previous studies have shown that plasma sheet in tenuous and hot during southward IMF, whereas northward IMF conditions are associated with cold, dense plasma. The cold, dense plasma sheet (CDPS) has strong influence on magnetospheric dynamics. Closer to Earth, the CDPS could be formed via double high-latitude reconnection, while at increasing tailward distance reconnection, diffusion and kinetic Alfven waves in association with Kelvin-Helmholtz Instability are suggested as dominant source for cold-dense plasma sheet formation. In this paper we present statistical correlation study between Solar Wind, Magnetosheath and Plasma sheet properties using 9+ years of THEMIS data in aberrated GSM frame, and in a normalized coordinate system that takes into account the changes of the magnetopause and bow shock location with respect to changing solar wind conditions. We present statistical results of the plasma sheet density dependence on IMF orientation and other solar wind properties.

Evaluation of flow quality in two large NASA wind tunnels at transonic speeds

NASA Technical Reports Server (NTRS)

Harvey, W. D.; Stainback, P. C.; Owen, F. K.

1980-01-01

Wind tunnel testing of low drag airfoils and basic transition studies at transonic speeds are designed to provide high quality aerodynamic data at high Reynolds numbers. This requires that the flow quality in facilities used for such research be excellent. To obtain a better understanding of the characteristics of facility disturbances and identification of their sources for possible facility modification, detailed flow quality measurements were made in two prospective NASA wind tunnels. Experimental results are presented of an extensive and systematic flow quality study of the settling chamber, test section, and diffuser in the Langley 8 foot transonic pressure tunnel and the Ames 12 foot pressure wind tunnel. Results indicate that the free stream velocity and pressure fluctuation levels in both facilities are low at subsonic speeds and are so high as to make it difficult to conduct meaningful boundary layer control and transition studies at transonic speeds.

U.S. Geographic Analysis of the Cost of Hydrogen from Electrolysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saur, G.; Ainscough, C.

2011-12-01

This report summarizes U.S. geographic analysis of the cost of hydrogen from electrolysis. Wind-based water electrolysis represents a viable path to renewably-produced hydrogen production. It might be used for hydrogen-based transportation fuels, energy storage to augment electricity grid services, or as a supplement for other industrial hydrogen uses. This analysis focuses on the levelized production, costs of producing green hydrogen, rather than market prices which would require more extensive knowledge of an hourly or daily hydrogen market. However, the costs of hydrogen presented here do include a small profit from an internal rate of return on the system. The costmore » of renewable wind-based hydrogen production is very sensitive to the cost of the wind electricity. Using differently priced grid electricity to supplement the system had only a small effect on the cost of hydrogen; because wind electricity was always used either directly or indirectly to fully generate the hydrogen. Wind classes 3-6 across the U.S. were examined and the costs of hydrogen ranged from $3.74kg to $5.86/kg. These costs do not quite meet the 2015 DOE targets for central or distributed hydrogen production ($3.10/kg and $3.70/kg, respectively), so more work is needed on reducing the cost of wind electricity and the electrolyzers. If the PTC and ITC are claimed, however, many of the sites will meet both targets. For a subset of distributed refueling stations where there is also inexpensive, open space nearby this could be an alternative to central hydrogen production and distribution.« less

The effects of thermospheric winds and chemistry in the diurnal variations of thermospheric species

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Harris, I.

1977-01-01

The reported investigation considers on the basis of a theoretical model, the diurnal variations of the thermospheric composition (H, He, O, O2, and Ar) in terms of thermal expansion with diffusive equilibrium and transport effects associated with thermospheric winds, chemistry, and exospheric flow. The theoretical results are compared with satellite composition data which indicate that the fundamental diurnal tide can be reasonably well understood. It is found that winds are only important for molecular oxygen below 180 km, while thermal expansion due to the larger mass is relatively more important for O2 than for O. Distinct from O, photodissociation and in particular photoionization of O2 are very significant for molecular oxygen.

Aerodynamic design guidelines and computer program for estimation of subsonic wind tunnel performance

NASA Technical Reports Server (NTRS)

Eckert, W. T.; Mort, K. W.; Jope, J.

1976-01-01

General guidelines are given for the design of diffusers, contractions, corners, and the inlets and exits of non-return tunnels. A system of equations, reflecting the current technology, has been compiled and assembled into a computer program (a user's manual for this program is included) for determining the total pressure losses. The formulation presented is applicable to compressible flow through most closed- or open-throat, single-, double-, or non-return wind tunnels. A comparison of estimated performance with that actually achieved by several existing facilities produced generally good agreement.

Dynamic Response of Ramjet Inlets to Downstream Perturbations.

DTIC Science & Technology

1983-01-31

NDC -00784 UNCLASSIFIED N98814-8R-C-8481 F/S 26/4 NL EIIIIIIIII-EIIhIIIIIIIIE EllhlhllllhhI *lfl gi IIDi w,. . , 2 9,- * .t .C- 0- . 1-" "L/" wo 1. I...dual-throat model configured as a small supersonic wind tunnel . References to a diffuser in the task statements reflect these initial ideas. However, it...determination of UB requires a wind tunnel test or possibly a free jet experiment with a large jet diameter compared to the model size. 1 5 17 4 4 4~,d

Effect of chemical heat release in a temporally evolving mixing layer

NASA Technical Reports Server (NTRS)

Higuera, F. J.; Moser, R. D.

1994-01-01

Two-dimensional numerical simulations of a temporally evolving mixing layer with an exothermic infinitely fast diffusion flame between two unmixed reactants have been carried out in the limit of zero Mach number to study the effect of the heat release on the early stages of the evolution of the flow. Attention has been directed to relatively large values of the oxidizer-to-fuel mass stoichiometric ratio typical of hydrocarbon flames, and initial vorticity distributions thicker than the temperature and species distributions have been chosen to mimic the situation at the outlet of a jet. The results show that, during the stages of the evolution covered by the present simulations, enhancement of combustion occurs by local stretching of the flame without much augmentation of its area. The rate of product generation depends strongly on the initial conditions, which suggests the possibility of controlling the combustion by acting on the flow. Rollup and vortex amalgamation still occur in these reacting flows but are very much affected by the production of new vorticity by baroclinic torques. These torques lead to counter rotating vortex pairs around the flame and, more importantly, in thin layers of light fluid that leave the vicinity of the flame when the Kelvin-Helmholtz instability begins to develop. Propelled by the vortex pairs, these layers wind around, split on reaching high pressure regions, and originate new vortex pairs in a process that ends up building large-scale vortices with a vorticity distribution more complex than for a constant density fluid.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karr, Dale G.; Yu, Bingbin; Sirnivas, Senu

To create long-term solutions for offshore wind turbines in a variety of environmental conditions, CAE tools are needed to model the design-driving loads that interact with an offshore wind turbine system during operation. This report describes our efforts in augmenting existing CAE tools used for offshore wind turbine analysis with a new module that can provide simulation capabilities for ice loading on the system. This augmentation was accomplished by creating an ice-loading module coupled to FAST8, the CAE tool maintained by the NREL for simulating land-based and offshore wind turbine dynamics. The new module includes both static and dynamic icemore » loading that can be applied during a dynamic simulation of the response of an offshore wind turbine. The ice forces can be prescribed, or influenced by the structure’s compliant response, or by the dynamics of both the structure and the ice floe. The new module covers ice failure modes of spalling, buckling, crushing, splitting, and bending. The supporting structure of wind turbines can be modeled as a vertical or sloping form at the waterline. The Inward Battered Guide Structure (IBGS) foundation designed by Keystone Engineering for the Great Lakes was used to study the ice models coupled to FAST8. The IBGS foundation ice loading simulations in FAST8 were compared to the baseline simulation case without ice loading. The ice conditions reflecting those from Lake Huron at Port Huron and Lake Michigan at North Manitou were studied under near rated wind speed of 12 m/s for the NREL 5-MW reference turbine. Simulations were performed on ice loading models 1 through 4 and ice model 6 with their respective sub-models. The purpose of ice model 5 is to investigate ice loading on sloping structures such as ice-cones on a monopile and is not suitable for multi-membered jacketed structures like the IBGS foundation. The key response parameters from the simulations, shear forces and moments from the tower base and IBGS foundation base, were compared. Ice models 1 and 6 do not significantly affect the tower fore-aft shear and moment. However, ice model 2 (dynamic analyses), model 3 (random ice loading), and model 4 (multiple ice failure zone loading) show increased effect on the tower fore-aft shear and moment with significant effect from ice model 3.1. In general ice loading creates large reaction forces and moments at the base of the IBGS foundation; the largest occurred in model 1.1 (steady creep ice indentation loading) followed by model 3.1 (random creep ice indentation loading). In general the power production from the ice loading cases had little deviation from the baseline case without ice loading. For ultimate limit state (ULS), ice model 1.1 ice and 3.1 appear to be the ice most critical models to consider at an early stage of design. Ice model 4 is an important tool for assessing structural fatigue.« less

The ionizing effect of low-energy cosmic rays from a class II object on its protoplanetary disc

NASA Astrophysics Data System (ADS)

Rodgers-Lee, D.; Taylor, A. M.; Ray, T. P.; Downes, T. P.

2017-11-01

We investigate the ionizing effect of low-energy cosmic rays (CRs) from a young star on its protoplanetary disc (PPD). We consider specifically the effect of ∼3 GeV protons injected at the inner edge of the PPD. An increase in the ionization fraction as a result of these CRs could allow the magnetorotational instability to operate in otherwise magnetically dead regions of the disc. For the typical values assumed we find an ionization rate of ζCR ∼ 10-17 s-1 at 1 au. The transport equation is solved by treating the propagation of the CRs as diffusive. We find for increasing diffusion coefficients the CRs penetrate further in the PPD, while varying the mass density profile of the disc is found to have little effect. We investigate the effect of an energy spectrum of CRs. The influence of a disc wind is examined by including an advective term. For advective wind speeds between 1 and 100 km s-1 diffusion dominates at all radii considered here (out to 10 au) for reasonable diffusion coefficients. Overall, we find that low-energy CRs can significantly ionize the mid-plane of PPDs out to ∼1 au. By increasing the luminosity or energy of the CRs, within plausible limits, their radial influence could increase to ∼2 au at the mid-plane but it remains challenging to significantly ionize the mid-plane further out.

Numerical modeling on air quality in an urban environment with changes of the aspect ratio and wind direction.

PubMed

Yassin, Mohamed F

2013-06-01

Due to heavy traffic emissions within an urban environment, air quality during the last decade becomes worse year by year and hazard to public health. In the present work, numerical modeling of flow and dispersion of gaseous emissions from vehicle exhaust in a street canyon were investigated under changes of the aspect ratio and wind direction. The three-dimensional flow and dispersion of gaseous pollutants were modeled using a computational fluid dynamics (CFD) model which was numerically solved using Reynolds-averaged Navier-Stokes (RANS) equations. The diffusion flow field in the atmospheric boundary layer within the street canyon was studied for different aspect ratios (W/H=1/2, 3/4, and 1) and wind directions (θ=90°, 112.5°, 135°, and 157.5°). The numerical models were validated against wind tunnel results to optimize the turbulence model. The numerical results agreed well with the wind tunnel results. The simulation demonstrated that the minimum concentration at the human respiration height within the street canyon was on the windward side for aspect ratios W/H=1/2 and 1 and wind directions θ=112.5°, 135°, and 157.5°. The pollutant concentration level decreases as the wind direction and aspect ratio increase. The wind velocity and turbulence intensity increase as the aspect ratio and wind direction increase.

Special relativity corrections for space-based lidars.

PubMed

Gudimetla, V S; Kavaya, M J

1999-10-20

The theory of special relativity is used to analyze some of the physical phenomena associated with space-based coherent Doppler lidars aimed at Earth and the atmosphere. Two important cases of diffuse scattering and retroreflection by lidar targets are treated. For the case of diffuse scattering, we show that for a coaligned transmitter and receiver on the moving satellite, there is no angle between transmitted and returned radiation. However, the ray that enters the receiver does not correspond to a retroreflected ray by the target. For the retroreflection case there is misalignment between the transmitted ray and the received ray. In addition, the Doppler shift in the frequency and the amount of tip for the receiver aperture when needed are calculated. The error in estimating wind because of the Doppler shift in the frequency due to special relativity effects is examined. The results are then applied to a proposed space-based pulsed coherent Doppler lidar at NASA's Marshall Space Flight Center for wind and aerosol backscatter measurements. The lidar uses an orbiting spacecraft with a pulsed laser source and measures the Doppler shift between the transmitted and the received frequencies to determine the atmospheric wind velocities. We show that the special relativity effects are small for the proposed system.

Special Relativity Corrections for Space-Based Lidars

NASA Technical Reports Server (NTRS)

RaoGudimetla, Venkata S.; Kavaya, Michael J.

1999-01-01

The theory of special relativity is used to analyze some of the physical phenomena associated with space-based coherent Doppler lidars aimed at Earth and the atmosphere. Two important cases of diffuse scattering and retroreflection by lidar targets are treated. For the case of diffuse scattering, we show that for a coaligned transmitter and receiver on the moving satellite, there is no angle between transmitted and returned radiation. However, the ray that enters the receiver does not correspond to a retroreflected ray by the target. For the retroreflection case there is misalignment between the transmitted ray and the received ray. In addition, the Doppler shift in the frequency and the amount of tip for the receiver aperture when needed are calculated, The error in estimating wind because of the Doppler shift in the frequency due to special relativity effects is examined. The results are then applied to a proposed space-based pulsed coherent Doppler lidar at NASA's Marshall Space Flight Center for wind and aerosol backscatter measurements. The lidar uses an orbiting spacecraft with a pulsed laser source and measures the Doppler shift between the transmitted and the received frequencies to determine the atmospheric wind velocities. We show that the special relativity effects are small for the proposed system.

Medium-energy electrons and heavy ions in Jupiter's magnetosphere - Effects of lower hybrid wave-particle interactions

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1986-01-01

A theory of medium-energy (about keV) electrons and heavy ions in Jupiter's magnetosphere is presented. Lower hybrid waves are generated by the combined effects of a ring instability of neutral wind pickup ions and the modified two-stream instability associated with transport of cool Iogenic plasma. The quasi-linear energy diffusion coefficient for lower hybrid wave-particle interactions is evaluated, and several solutions to the diffusion equation are given. Calculations based on measured wave properties show that the noise substantially modifies the particle distribution functions. The effects are to accelerate superthermal ions and electrons to keV energies and to thermalize the pickup ions on time scales comparable to the particle residence time. The S(2+)/S(+) ratio at medium energies is a measure of the relative contribution from Iogenic thermal plasma and neutral wind ions, and this important quantity should be determined from future measurements. The theory also predicts a preferential acceleration of heavy ions with an accleration time that scales inversely with the root of the ion mass. Electrons accelerated by the process contribute to further reionization of the neutral wind by electron impact, thus providing a possible confirmation of Alfven's critical velocity effect in the Jovian magnetosphere.

Transport governs flow-enhanced cell tethering through L-selectin at threshold shear.

PubMed

Yago, Tadayuki; Zarnitsyna, Veronika I; Klopocki, Arkadiusz G; McEver, Rodger P; Zhu, Cheng

2007-01-01

Flow-enhanced cell adhesion is a counterintuitive phenomenon that has been observed in several biological systems. Flow augments L-selectin-dependent adhesion by increasing the initial tethering of leukocytes to vascular surfaces and by strengthening their subsequent rolling interactions. Tethering or rolling might be influenced by physical factors that affect the formation or dissociation of selectin-ligand bonds. We recently demonstrated that flow enhanced rolling of L-selectin-bearing microspheres or neutrophils on P-selectin glycoprotein ligand-1 by force decreased bond dissociation. Here, we show that flow augmented tethering of these microspheres or cells to P-selectin glycoprotein ligand-1 by three transport mechanisms that increased bond formation: sliding of the sphere bottom on the surface, Brownian motion, and molecular diffusion. These results elucidate the mechanisms for flow-enhanced tethering through L-selectin.

Integrated Flight/Structural Mode Control for Very Flexible Aircraft Using L1 Adaptive Output Feedback Controller

NASA Technical Reports Server (NTRS)

Che, Jiaxing; Cao, Chengyu; Gregory, Irene M.

2012-01-01

This paper explores application of adaptive control architecture to a light, high-aspect ratio, flexible aircraft configuration that exhibits strong rigid body/flexible mode coupling. Specifically, an L(sub 1) adaptive output feedback controller is developed for a semi-span wind tunnel model capable of motion. The wind tunnel mount allows the semi-span model to translate vertically and pitch at the wing root, resulting in better simulation of an aircraft s rigid body motion. The control objective is to design a pitch control with altitude hold while suppressing body freedom flutter. The controller is an output feedback nominal controller (LQG) augmented by an L(sub 1) adaptive loop. A modification to the L(sub 1) output feedback is proposed to make it more suitable for flexible structures. The new control law relaxes the required bounds on the unmatched uncertainty and allows dependence on the state as well as time, i.e. a more general unmatched nonlinearity. The paper presents controller development and simulated performance responses. Simulation is conducted by using full state flexible wing models derived from test data at 10 different dynamic pressure conditions. An L(sub 1) adaptive output feedback controller is designed for a single test point and is then applied to all the test cases. The simulation results show that the L(sub 1) augmented controller can stabilize and meet the performance requirements for all 10 test conditions ranging from 30 psf to 130 psf dynamic pressure.

Coupling of Outward Radial Diffusion and Losses at the Magnetopause in the Outer Radiation Belt

NASA Astrophysics Data System (ADS)

Castillo Tibocha, A. M.; Shprits, Y.; Drozdov, A.; Kellerman, A. C.; Aseev, N.

2017-12-01

Sudden dropouts observed in relativistic electron fluxes within the radiation belts are one the most studied and yet poorly understood features of the dynamics of radiation belts. A number of physical processes contributing to these dropout events are triggered by solar wind drivers. Magnetopause losses are one of the most effective mechanisms involved here and usually occur when drifting particles reach the boundary or when inward motion of the magnetopause crosses closed particle drift shells. In both cases, particles are rapidly transported into interplanetary space generating sharp gradients in electron PSD that will promote further outward radial diffusion of particles due to adiabatic transport and the influence of outward ULF waves. Studies suggest that the coupling of these two mechanisms explains nearly all the depletion of MeV electrons observed in the outer region of the radiation belts (L*>5). In this study, we present a simple approach to model electron losses at the magnetopause and outward radial diffusion in the outer radiation belt during geomagnetic storm time. Measured upstream solar wind parameters were used to calculate the radial distance of the subsolar point as proposed by Shue et al. (1997), which was defined as the radial extent of our assumed dipole field configuration. Radial diffusion was modelled using the empirical Kp-dependent DLL [Brautigam and Albert, JGR 2000] diffusion coefficient, which is included in the 3D Versatile Electron Radiation Belt (VERB) code. Simulations of geomagnetic storms were performed in order to evaluate the effects of the integrated mechanisms and the results were compared with Van Allen probe satellite data. Our simulation results reproduce well the observed loss at the magnetopause and electron depletion in the outer radiation belt.

ULF Wave Analysis and Radial Diffusion Calculation Using a Global MHD Model for the 17 March 2015 Storm and Comparison with the 17 March 2013 Storm

NASA Astrophysics Data System (ADS)

Li, Z.; Hudson, M.; Paral, J.; Wiltberger, M. J.; Boyd, A. J.; Turner, D. L.

2016-12-01

The 17 March 2015 `St. Patrick's Day Storm' is the largest geomagnetic storm to date of Solar Cycle 24, with a Dst of -223 nT. The magnetopause moved inside geosynchronous orbit under high solar wind dynamic pressure and strong southward IMF Bz causing loss, however a subsequent drop in pressure allowed for rapid rebuilding of the radiation belts. Local heating has been modeled by other groups for this and the 17 March 2013 storm, only slightly weaker and showing a similar effect on electrons: first a rapid dropout due to inward motion of the magnetopause followed by rapid increase in flux above the pre-storm level and an even greater slow increase likely due to radial diffusion. The latter can be seen in temporal evolution of the electron phase space density measured by the Energetic Particle, Composition, and Thermal Plasma Suite (ECT) instrument on Van Allen Probes. Using the Lyon-Fedder-Mobarry global MHD model driven by upstream solar wind measurements with the Magneotsphere-Ionosphere Coupler (MIX), we have simulated both `St. Patrick's Day'events, analyzing LFM electric and magnetic fields to calculate radial diffusion coefficients. These coefficients have been implemented in a radial diffusion code using the measured electron phase space density profile following the local heating and as the outer boundary condition for subsequent temporally evolution over the next 12 days, beginning 18 March 2015. Agreement with electron phase space density at 1000 MeV/G measured by the MagEIS component of the ECT instrument on Van Allen Probes (30 keV - 4 MeV) was much improved using radial diffusion coefficients from the MHD simulations relative to coefficients parametrized by a global geomagnetic activity index.

Next-generation prognostic assessment for diffuse large B-cell lymphoma

PubMed Central

Staton, Ashley D; Kof, Jean L; Chen, Qiushi; Ayer, Turgay; Flowers, Christopher R

2015-01-01

Current standard of care therapy for diffuse large B-cell lymphoma (DLBCL) cures a majority of patients with additional benefit in salvage therapy and autologous stem cell transplant for patients who relapse. The next generation of prognostic models for DLBCL aims to more accurately stratify patients for novel therapies and risk-adapted treatment strategies. This review discusses the significance of host genetic and tumor genomic alterations seen in DLBCL, clinical and epidemiologic factors, and how each can be integrated into risk stratification algorithms. In the future, treatment prediction and prognostic model development and subsequent validation will require data from a large number of DLBCL patients to establish sufficient statistical power to correctly predict outcome. Novel modeling approaches can augment these efforts. PMID:26289217

Next-generation prognostic assessment for diffuse large B-cell lymphoma.

PubMed

Staton, Ashley D; Koff, Jean L; Chen, Qiushi; Ayer, Turgay; Flowers, Christopher R

2015-01-01

Current standard of care therapy for diffuse large B-cell lymphoma (DLBCL) cures a majority of patients with additional benefit in salvage therapy and autologous stem cell transplant for patients who relapse. The next generation of prognostic models for DLBCL aims to more accurately stratify patients for novel therapies and risk-adapted treatment strategies. This review discusses the significance of host genetic and tumor genomic alterations seen in DLBCL, clinical and epidemiologic factors, and how each can be integrated into risk stratification algorithms. In the future, treatment prediction and prognostic model development and subsequent validation will require data from a large number of DLBCL patients to establish sufficient statistical power to correctly predict outcome. Novel modeling approaches can augment these efforts.

A computational study of radiation and gravity effect on temperature and soot formation in a methane air co-flow diffusion flame

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhowal, Arup Jyoti, E-mail: arupjyoti.bhowal@heritageit.edu; Mandal, Bijan Kumar, E-mail: bkm375@yahoo.co.in

An effort has been made for a quantitative assessment of the soot formed under steady state in a methane air co flow diffusion flame by a numerical simulation at normal gravity and at lower gravity levels of 0.5 G, 0.1 G and 0.0001 G (microgravity). The peak temperature at microgravity is reduced by about 50 K than that at normal gravity level. There is an augmentation of soot formation at lower gravity levels. Peak value at microgravity multiplies by a factor of ∼7 of that at normal gravity. However, if radiation is not considered, soot formation is found to bemore » much more.« less

Buoyancy forcing and the MOC: insights from experiments, simulations and global models

NASA Astrophysics Data System (ADS)

White, B. L.; Passaggia, P. Y.; Zemskova, V.

2017-12-01

The driving forces behind the Meridional Overturning Circulation (MOC) have been widely debated, with wind-driven upwelling, surface buoyancy fluxes due to heating/cooling/freshwater input, and vertical diffusion due to turbulent mixing all thought to play significant roles. To explore the specific role of buoyancy forcing we present results from experiments and simulations of Horizontal Convection (HC), where a circulation is driven by differential buoyancy forcing applied along a horizontal surface. We interpret these results using energy budgets based on the local Available Potential Energy framework introduced in [Scotti and White, J. Fluid Mech., 2014]. We first describe HC experiments driven by the diffusion of salt in water across membranes localized at the surface, at Schmidt numbers {Sc}≈ 610 and Rayleigh numbers in the range 1012 < Ra=Δ b L3/(ν κ ) < 1017, where ν is the kinematic viscosity of water, κ is the diffusion coefficient of salt, L=[.5,2,5]m is the length of the different tanks and Δ b=g(ρ salt}-ρ {fresh}/ρ_{fresh is the reduced gravity difference. We show that the scaling follows a Nu ˜ Ra1/4 type scaling recently theorized by Shishkina et; al. (2016). We then present numerical results for rotating horizontal convection with a zonally re-entrant channel to represent the Southern Ocean branch of the MOC. While the zonal wind stress profile is important to the spatial pattern of the circulation, perhaps surprisingly, the energy budget shows only a weak dependence on the magnitude of the wind input, suggesting that surface APE generation by buoyancy forcing is dominant in driving the overturning circulation.

Photochemistry, mixing and transport in Jupiter's stratosphere constrained by Cassini

NASA Astrophysics Data System (ADS)

Hue, V.; Hersant, F.; Cavalié, T.; Dobrijevic, M.; Sinclair, J. A.

2018-06-01

In this work, we aim at constraining the diffusive and advective transport processes in Jupiter's stratosphere, using Cassini/CIRS observations published by Nixon et al. (2007,2010). The Cassini-Huygens flyby of Jupiter on December 2000 provided the highest spatially resolved IR observations of Jupiter so far, with the CIRS instrument. The IR spectrum contains the fingerprints of several atmospheric constituents and allows probing the tropospheric and stratospheric composition. In particular, the abundances of C2H2 and C2H6, the main compounds produced by methane photochemistry, can be retrieved as a function of latitude in the pressure range at which CIRS is sensitive to. CIRS observations suggest a very different meridional distribution for these two species. This is difficult to reconcile with their photochemical histories, which are thought to be tightly coupled to the methane photolysis. While the overall abundance of C2H2 decreases with latitude, C2H6 becomes more abundant at high latitudes. In this work, a new 2D (latitude-altitude) seasonal photochemical model of Jupiter is developed. The model is used to investigate whether the addition of stratospheric transport processes, such as meridional diffusion and advection, are able to explain the latitudinal behavior of C2H2 and C2H6. We find that the C2H2 observations are fairly well reproduced without meridional diffusion. Adding meridional diffusion to the model provides an improved agreement with the C2H6 observations by flattening its meridional distribution, at the cost of a degradation of the fit to the C2H2 distribution. However, meridional diffusion alone cannot produce the observed increase with latitude of the C2H6 abundance. When adding 2D advective transport between roughly 30 mbar and 0.01 mbar, with upwelling winds at the equator and downwelling winds at high latitudes, we can, for the first time, reproduce the C2H6 abundance increase with latitude. In parallel, the fit to the C2H2 distribution is degraded. The strength of the advective winds needed to reproduce the C2H6 abundances is particularly sensitive to the value of the meridional eddy diffusion coefficient. The coupled fate of these methane photolysis by-products suggests that an additional process is missing in the model. Ion-neutral chemistry was not accounted for in this work and might be a good candidate to solve this issue.

Benchmark calculations of excess electrons in water cluster cavities: balancing the addition of atom-centered diffuse functions versus floating diffuse functions.

PubMed

Zhang, Changzhe; Bu, Yuxiang

2016-09-14

Diffuse functions have been proved to be especially crucial for the accurate characterization of excess electrons which are usually bound weakly in intermolecular zones far away from the nuclei. To examine the effects of diffuse functions on the nature of the cavity-shaped excess electrons in water cluster surroundings, both the HOMO and LUMO distributions, vertical detachment energies (VDEs) and visible absorption spectra of two selected (H2O)24(-) isomers are investigated in the present work. Two main types of diffuse functions are considered in calculations including the Pople-style atom-centered diffuse functions and the ghost-atom-based floating diffuse functions. It is found that augmentation of atom-centered diffuse functions contributes to a better description of the HOMO (corresponding to the VDE convergence), in agreement with previous studies, but also leads to unreasonable diffuse characters of the LUMO with significant red-shifts in the visible spectra, which is against the conventional point of view that the more the diffuse functions, the better the results. The issue of designing extra floating functions for excess electrons has also been systematically discussed, which indicates that the floating diffuse functions are necessary not only for reducing the computational cost but also for improving both the HOMO and LUMO accuracy. Thus, the basis sets with a combination of partial atom-centered diffuse functions and floating diffuse functions are recommended for a reliable description of the weakly bound electrons. This work presents an efficient way for characterizing the electronic properties of weakly bound electrons accurately by balancing the addition of atom-centered diffuse functions and floating diffuse functions and also by balancing the computational cost and accuracy of the calculated results, and thus is very useful in the relevant calculations of various solvated electron systems and weakly bound anionic systems.

Evaluation of the polyurethane foam (PUF) disk passive air sampler: Computational modeling and experimental measurements

NASA Astrophysics Data System (ADS)

May, Andrew A.; Ashman, Paul; Huang, Jiaoyan; Dhaniyala, Suresh; Holsen, Thomas M.

2011-08-01

Computational fluid dynamics (CFD) simulations coupled with wind tunnel-experiments were used to determine the sampling rate (SR) of the widely used polyurethane foam (PUF) disk passive sampler. In the wind-tunnel experiments, water evaporation rates from a water saturated PUF disk installed in the sampler housing were determined by measuring weight loss over time. In addition, a modified passive sampler designed to collect elemental mercury (Hg 0) with gold-coated filters was used. Experiments were carried out at different wind speeds and various sampler angles. The SRs obtained from wind-tunnel experiments were compared to those obtained from the field by scaling the values by the ratios of air diffusivities. Three-dimensional (3D) CFD simulations were also used to generate SRs for both polychlorinated biphenyls (PCBs) and Hg 0. Overall, the modeled and measured SRs agree well and are consistent with the values obtained from field studies. As previously observed, the SRs increased linearly with increasing wind speed. In addition, it was determined that the SR was strongly dependent on the angle of the ambient wind. The SRs increased when the base was tilted up pointing into the wind and when the base was tilted down (i.e., such that the top of the sampler was facing the wind) the SR decreased initially and then increased. The results suggest that there may be significant uncertainty in concentrations obtained from passive sampler measurements without knowledge of wind speed and wind angle relative to the sampler.

Wind-driving protostellar accretion discs - I. Formulation and parameter constraints

NASA Astrophysics Data System (ADS)

Königl, Arieh; Salmeron, Raquel; Wardle, Mark

2010-01-01

We study a model of weakly ionized, protostellar accretion discs that are threaded by a large-scale, ordered magnetic field and power a centrifugally driven wind. We consider the limiting case where the wind is the main repository of the excess disc angular momentum and generalize the radially localized disc model of Wardle & Königl, which focused on the ambipolar diffusion regime, to other field diffusivity regimes, notably Hall and Ohm. We present a general formulation of the problem for nearly Keplerian, vertically isothermal discs using both the conductivity-tensor and the multifluid approaches and simplify it to a normalized system of ordinary differential equations in the vertical space coordinate. We determine the relevant parameters of the problem and investigate, using the vertical-hydrostatic-equilibrium approximation and other simplifications, the parameter constraints on physically viable solutions for discs in which the neutral particles are dynamically well coupled to the field already at the mid-plane. When the charged particles constitute a two-component ion-electron plasma, one can identify four distinct sub-regimes in the parameter domain where the Hall diffusivity dominates and three sub-regimes in the Ohm-dominated domain. Two of the Hall sub-regimes can be characterized as being ambipolar diffusion-like and two as being Ohm-like: the properties of one member of the first pair of sub-regimes are identical to those of the ambipolar diffusion regime, whereas one member of the second pair has the same characteristics as one of the Ohm sub-regimes. All the Hall sub-regimes have Brb/|Bφb| (ratio of radial-to-azimuthal magnetic field amplitudes at the disc surface) >1, whereas in two Ohm sub-regimes this ratio is <1. When the two-component plasma consists, instead, of positively and negatively charged grains of equal mass, the entire Hall domain and one of the Ohm sub-regimes with Brb/|Bφb| < 1 disappear. All viable solutions require the mid-plane neutral-ion momentum exchange time to be shorter than the local orbital time. We also infer that vertical magnetic squeezing always dominates over gravitational tidal compression in this model. In a follow-up paper we will present exact solutions that test the results of this analysis in the Hall regime.

VALDRIFT 1.0: A valley atmospheric dispersion model with deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allwine, K.J.; Bian, X.; Whiteman, C.D.

1995-05-01

VALDRIFT version 1.0 is an atmospheric transport and diffusion model for use in well-defined mountain valleys. It is designed to determine the extent of ddft from aedal pesticide spraying activities, but can also be applied to estimate the transport and diffusion of various air pollutants in valleys. The model is phenomenological -- that is, the dominant meteorological processes goveming the behavior of the valley atmosphere are formulated explicitly in the model, albeit in a highly parameterized fashion. The key meteorological processes treated are: (1) nonsteady and nonhomogeneous along-valley winds and turbulent diffusivities, (2) convective boundary layer growth, (3) inversion descent,more » (4) noctumal temperature inversion breakup, and (5) subsidence. The model is applicable under relatively cloud-free, undisturbed synoptic conditions and is configured to operate through one diumal cycle for a single valley. The inputs required are the valley topographical characteristics, pesticide release rate as a function of time and space, along-valley wind speed as a function of time and space, temperature inversion characteristics at sunrise, and sensible heat flux as a function of time following sunrise. Default values are provided for certain inputs in the absence of detailed observations. The outputs are three-dimensional air concentration and ground-level deposition fields as a function of time.« less

Bulk properties and velocity distributions of water group ions at Comet Halley - Giotto measurements

NASA Astrophysics Data System (ADS)

Coates, A. J.; Wilken, B.; Johnstone, A. D.; Jockers, K.; Glassmeier, K.-H.; Huddleston, D. E.

1990-07-01

In the region upstream of Comet Halley, pickup heavy ions of cometary origin were directly observed by the implanted ion spectrometer on Giotto. Diffusion of this population in pitch angle and in energy, during the approach to the comet and on the outbound leg is discussed. The two data sets are compared and qualitative ideas on scattering timescales are inferred. In addition the bulk parameters of these distributions have been computed and a comparison of the observed speed in the solar wind frame and the observed density with expectations is presented. Pitch angle scattering occurs more slowly than expected with filled shells appearing at 2,500,000 km, and significant energy diffusion does not occur until the bow shock region. Also the shell distributions downstream of the shock flow at the bispherical bulk speed (related to the Alfven speed) along the magnetic field with respect to the solar wind in accordance with conservation of energy between the pickup ions and the wave turbulence.

A theoretical study of the global F region for June solstice, solar maximum, and low magnetic activity

NASA Technical Reports Server (NTRS)

Sojka, J. J.; Schunk, R. W.

1985-01-01

A time-dependent, three-dimensional, multi-ion model of the ionospheric F region at 120-800 km altitude is presented. Account is taken of field-aligned diffusion, cross-field electrodynamic drifts in equatorial and high latitude regions, interhemispheric flow, thermospheric winds, polar wind escape, energy-dependent chemical reactions and neutral composition changes. Attention is also given to the effects of ion production by solar EUV radiation and auroral precipitation, thermal conduction, diffusion-thermal heat flow, local heating and cooling processes, offsets between the geomagnetic and geographic poles, and bending of field lines near the magnetic equator. The model incorporates all phenomena described by previous models and can be applied to tracing magnetic storm and substorm disturbances from high to low latitudes on a global scale. Sample results are provided for ionospheric features during a June solstice, the solar maximum and in a period of low geomagnetic activity. The model will eventually be used to study coupled ionosphere-thermosphere activity.

Uncertainty of Videogrammetric Techniques used for Aerodynamic Testing

NASA Technical Reports Server (NTRS)

Burner, A. W.; Liu, Tianshu; DeLoach, Richard

2002-01-01

The uncertainty of videogrammetric techniques used for the measurement of static aeroelastic wind tunnel model deformation and wind tunnel model pitch angle is discussed. Sensitivity analyses and geometrical considerations of uncertainty are augmented by analyses of experimental data in which videogrammetric angle measurements were taken simultaneously with precision servo accelerometers corrected for dynamics. An analysis of variance (ANOVA) to examine error dependence on angle of attack, sensor used (inertial or optical). and on tunnel state variables such as Mach number is presented. Experimental comparisons with a high-accuracy indexing table are presented. Small roll angles are found to introduce a zero-shift in the measured angles. It is shown experimentally that. provided the proper constraints necessary for a solution are met, a single- camera solution can he comparable to a 2-camera intersection result. The relative immunity of optical techniques to dynamics is illustrated.

Adaptive Control Using Residual Mode Filters Applied to Wind Turbines

NASA Technical Reports Server (NTRS)

Frost, Susan A.; Balas, Mark J.

2011-01-01

Many dynamic systems containing a large number of modes can benefit from adaptive control techniques, which are well suited to applications that have unknown parameters and poorly known operating conditions. In this paper, we focus on a model reference direct adaptive control approach that has been extended to handle adaptive rejection of persistent disturbances. We extend this adaptive control theory to accommodate problematic modal subsystems of a plant that inhibit the adaptive controller by causing the open-loop plant to be non-minimum phase. We will augment the adaptive controller using a Residual Mode Filter (RMF) to compensate for problematic modal subsystems, thereby allowing the system to satisfy the requirements for the adaptive controller to have guaranteed convergence and bounded gains. We apply these theoretical results to design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed wind turbine that has minimum phase zeros.

Wind-tunnel studies of advanced cargo aircraft concepts. [leading edge vortex flaps for drag reduction

NASA Technical Reports Server (NTRS)

Rao, D. M.; Goglia, G. L.

1981-01-01

Accomplishments in vortex flap research are summarized. A singular feature of the vortex flap is that, throughout the range of angle of attack range, the flow type remains qualitatively unchanged. Accordingly, no large or sudden change in the aerodynamic characteristics, as happens when forcibly maintained attached flow suddenly reverts to separation, will occur with the vortex flap. Typical wind tunnel test data are presented which show the drag reduction potential of the vortex flap concept applied to a supersonic cruise airplane configuration. The new technology offers a means of aerodynamically augmenting roll-control effectiveness on slender wings at higher angles of attack by manipulating the vortex flow generated from leading edge separation. The proposed manipulator takes the form of a flap hinged at or close to the leading edge, normally retracted flush with the wing upper surface to conform to the airfoil shape.

Ensemble-based simultaneous state and parameter estimation for treatment of mesoscale model error: A real-data study

NASA Astrophysics Data System (ADS)

Hu, Xiao-Ming; Zhang, Fuqing; Nielsen-Gammon, John W.

2010-04-01

This study explores the treatment of model error and uncertainties through simultaneous state and parameter estimation (SSPE) with an ensemble Kalman filter (EnKF) in the simulation of a 2006 air pollution event over the greater Houston area during the Second Texas Air Quality Study (TexAQS-II). Two parameters in the atmospheric boundary layer parameterization associated with large model sensitivities are combined with standard prognostic variables in an augmented state vector to be continuously updated through assimilation of wind profiler observations. It is found that forecasts of the atmosphere with EnKF/SSPE are markedly improved over experiments with no state and/or parameter estimation. More specifically, the EnKF/SSPE is shown to help alleviate a near-surface cold bias and to alter the momentum mixing in the boundary layer to produce more realistic wind profiles.

Three decades of Martian surface changes

USGS Publications Warehouse

Geissler, P.E.

2005-01-01

The surface of Mars has changed dramatically during the three decades spanned by spacecraft exploration. Comparisons of Mars Global Surveyor images with Viking and Mariner 9 pictures suggest that more than one third of Mars' surface area has brightened or darkened by at least 10%. Such albedo changes could produce significant effects on solar heating and the global circulation of winds across the planet. All of the major changes took place in areas of moderate to high thermal inertia and rock abundance, consistent with burial of rocky surfaces by thin dust layers deposited during dust storms and subsequent exposure of the rocky surfaces by aeolian erosion. Several distinct mechanisms contribute to aeolian erosion on Mars. Prevailing winds dominate erosion at low latitudes, producing diffuse albedo boundaries and elongated wind streaks generally oriented in the direction of southern summer winds. Dust devils darken the mid to high latitudes from 45 to 70 degrees during the summer seasons, forming irregular albedo patterns consisting of dark linear tracks. Dust storms produce regional albedo variations with distinct but irregular margins. Dark sand duties in southern high latitudes appear to be associated with regional darkening that displays diffuse albedo boundaries. No surface changes were observed to repeat regularly on an annual basis, but many of the changes took place in areas that alternate episodically between high- and low-albedo states as thin mantles of dust are deposited and later stripped off. Hence the face of Mars remains recognizable after a century of telescopic observations, in spite of the enormous extent of alteration that has taken place during the era of spacecraft exploration.

Study of atmospheric diffusion using LANDSAT

NASA Technical Reports Server (NTRS)

Torsani, J. A.; Viswanadham, Y.

1982-01-01

The parameters of diffusion patterns of atmospheric pollutants under different conditions were investigated for use in the Gaussian model for calculation of pollution concentration. Value for the divergence pattern of concentration distribution along the Y axis were determined using LANDSAT images. Multispectral scanner images of a point source plume having known characteristics, wind and temperature data, and cloud cover and solar elevation data provided by LANDSAT, were analyzed using the 1-100 system for image analysis. These measured values are compared with pollution transport as predicted by the Pasquill-Gifford, Juelich, and Hoegstroem atmospheric models.

Dataset from chemical gas sensor array in turbulent wind tunnel.

PubMed

Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Huerta, Ramón

2015-06-01

The dataset includes the acquired time series of a chemical detection platform exposed to different gas conditions in a turbulent wind tunnel. The chemo-sensory elements were sampling directly the environment. In contrast to traditional approaches that include measurement chambers, open sampling systems are sensitive to dispersion mechanisms of gaseous chemical analytes, namely diffusion, turbulence, and advection, making the identification and monitoring of chemical substances more challenging. The sensing platform included 72 metal-oxide gas sensors that were positioned at 6 different locations of the wind tunnel. At each location, 10 distinct chemical gases were released in the wind tunnel, the sensors were evaluated at 5 different operating temperatures, and 3 different wind speeds were generated in the wind tunnel to induce different levels of turbulence. Moreover, each configuration was repeated 20 times, yielding a dataset of 18,000 measurements. The dataset was collected over a period of 16 months. The data is related to "On the performance of gas sensor arrays in open sampling systems using Inhibitory Support Vector Machines", by Vergara et al.[1]. The dataset can be accessed publicly at the UCI repository upon citation of [1]: http://archive.ics.uci.edu/ml/datasets/Gas+sensor+arrays+in+open+sampling+settings.

AGN Obscuration from Winds: From Dusty Infrared-Driven to Warm and X-Ray Photoionized

NASA Technical Reports Server (NTRS)

Dorodnitsyn, A.; Kallman, T.

2012-01-01

We present calculations of AGN winds at approximate parsec scales, along with the associated obscuration. We take into account the pressure of infrared radiation on dust grains and the interaction of X-rays from a central black hole with hot and cold plasma. Infrared radiation (IR) is incorporated in radiation-hydrodynamic simulations adopting the flux-limited diffusion approximation. We find that in the range of X-ray luminosities L=0.05 - 0.6L(sub Edd) the Compton-thick part of the flow (aka torus) has an opening angle of approximately 72? -75? regardless of the luminosity. At L 0.1 the outflowing dusty wind provides the obscuration with IR pressure playing a major role. The global flow consists of two phases: the cold flow at inclinations (theta) greater than or approximately 70? and a hot, ionized wind of lower density at lower inclinations. The dynamical pressure of the hot wind is important in shaping the denser IR supported flow. At luminosities less than or equal to 0.1L(sub Edd) episodes of outflow are followed by extended periods when the wind switches to slow accretion.

A comparison of ultrasound-augmented and conventional leaching of silver from sintering dust using acidic thiourea.

PubMed

Chang, Jun; Zhang, Er-Dong; Zhang, Li-Bo; Peng, Jin-Hui; Zhou, Jun-Wen; Srinivasakannan, C; Yang, Chang-Jiang

2017-01-01

In the process of steel manufacture, up to ten millions of tons of sintering dust (SD) are produced annually in China, which contain noble metals such as Ag. Therefore, recovery of silver (Ag) from SD could be a potential economic and environmental activity. The purpose of this article is to generate information about reaction kinetics of silver leaching with thiourea from SD, comparing the conventional and ultrasonic-augment leaching. The effects of various control parameters such as the ultrasound power, particle size, leaching temperature and thiourea concentration on leaching rate of silver were studied. The results showed 89% silver recovery for conventional process against 95% for ultrasound assisted leaching. The ultrasonic wave increased the leaching rate and shorten the reaction time. The rate controlling step was analyzed using shrinking core model and the rate controlling step is identified to be the diffusion through the product layer in both conventional and ultrasonic-augment leaching processes. The activation energies were estimated to be 28.01kJ/mol and 18.19kJ/mol, and the reaction order were 0.89 and 0.71, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

Analysis of Compression Pad Cavities for the Orion Heatshield

NASA Technical Reports Server (NTRS)

Thompson, Richard A.; Lessard, Victor R.; Jentink, Thomas N.; Zoby, Ernest V.

2009-01-01

Current results of a program for analysis of the compression pad cavities on the Orion heatshield are reviewed. The program was supported by experimental tests, engineering modeling, and applied computations with an emphasis on the latter presented in this paper. The computational tools and approach are described along with calculated results for wind tunnel and flight conditions. Correlations of the computed results are shown which can produce a credible prediction of heating augmentation due to cavity disturbances. The models developed for use in preliminary design of the Orion heatshield are presented.

Oakland Harbor. Deep-Draft Navigation Improvements. Design Memorandum Number 1, General Design and Final Supplement 1 to the Environmental Impact Statement, Alameda County, California.

DTIC Science & Technology

1988-03-01

presentations to the Panal , the Department of the Navy’s restrictions on submarine operating areas were mentioned, iniating that the Nxwy opposed...impacts of dredged material disposal and/or till gaps in data. Panal .fUtrugtgra and Oranh~AtaoAin The panel is comprised of five representatives from 2A...riverine inflow is the low and prevailing winds from the west or northwest are augmented by daily pressure gradient induced movement of air due to solar

9x15 Low Speed Wind Tunnel Acoustic Improvements

NASA Technical Reports Server (NTRS)

Stark, David; Stephens, David

2016-01-01

The 9- by 15-Foot Low Speed Wind Tunnel (9x15 LSWT) at NASA Glenn Research Center was built in 1969 in the return leg of the 8- by 6-Foot Supersonic Wind Tunnel (8x6 SWT). The 8x6 SWT was completed in 1949 and acoustically treated to mitigate community noise issues in 1950. This treatment included the addition of a large muffler downstream of the 8x6 SWT test section and diffuser. The 9x15 LSWT was designed for performance testing of VSTOL aircraft models, but with the addition of the current acoustic treatment in 1986 the tunnel has been used principally for acoustic and performance testing of aircraft propulsions systems. The present document describes an anticipated acoustic upgrade to be completed in 2017.

9- by 15-Foot Low Speed Wind Tunnel Acoustic Improvements Expanded Overview

NASA Technical Reports Server (NTRS)

Stephens, David

2016-01-01

The 9- by 15-Foot Low Speed Wind Tunnel (9x15 LSWT) at NASA Glenn Research Center was built in 1969 in the return leg of the 8- by 6-Foot Supersonic Wind Tunnel (8x6 SWT). The 8x6 SWT was completed in 1949 and acoustically treated to mitigate community noise issues in 1950. This treatment included the addition of a large muffler downstream of the 8x6 SWT test section and diffuser. The 9x15 LSWT was designed for performance testing of V/STOL aircraft models, but with the addition of the current acoustic treatment in 1986 the tunnel been used principally for acoustic and performance testing of aircraft propulsion systems. The present document describes an anticipated acoustic upgrade to be completed in 2017.

ION INJECTION AT QUASI-PARALLEL SHOCKS SEEN BY THE CLUSTER SPACECRAFT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johlander, A.; Vaivads, A.; Khotyaintsev, Yu. V.

2016-01-20

Collisionless shocks in space plasma are known to be capable of accelerating ions to very high energies through diffusive shock acceleration (DSA). This process requires an injection of suprathermal ions, but the mechanisms producing such a suprathermal ion seed population are still not fully understood. We study acceleration of solar wind ions resulting from reflection off short large-amplitude magnetic structures (SLAMSs) in the quasi-parallel bow shock of Earth using in situ data from the four Cluster spacecraft. Nearly specularly reflected solar wind ions are observed just upstream of a SLAMS. The reflected ions are undergoing shock drift acceleration (SDA) andmore » obtain energies higher than the solar wind energy upstream of the SLAMS. Our test particle simulations show that solar wind ions with lower energy are more likely to be reflected off the SLAMS, while high-energy ions pass through the SLAMS, which is consistent with the observations. The process of SDA at SLAMSs can provide an effective way of accelerating solar wind ions to suprathermal energies. Therefore, this could be a mechanism of ion injection into DSA in astrophysical plasmas.« less

Forecast and Specification of Radiation Belt Electrons Based on Solar Wind Measurements

NASA Astrophysics Data System (ADS)

Li, X.; Barker, A.; Burin Des Roziers, E.

2003-12-01

Relativistic electrons in the Earth's magnetosphere are of considerable practical importance because of their effect on spacecraft and because of their radiation hazard to astronauts who perform extravehicular activity. The good correlation between solar wind velocity and MeV electron fluxes at geosynchronous orbit has long been established. We have developed a radial diffusion model, using solar wind parameters as the only input, to reproduce the variation of the MeV electrons at geosynchronous orbit. Based on this model, we have constructed a real-time model that forecasts one to two days in advance the daily averaged >2 MeV electron flux at geosynchronous orbit using real-time solar wind data from ACE. The forecasts from this model are available on the web in real time. A natural extension of our current model is to create a system for making quantitative forecasts and specifications of radiation belt electrons at different radial distances and different local times based on the solar wind conditions. The successes and obstacles associated with this extension will be discussed in this presentation.

Galactic cosmic-ray mediation of a spherical solar wind flow. 1: The steady state cold gas hydrodynamical approximation

NASA Technical Reports Server (NTRS)

Le Roux, J. A.; Ptuskin, V. S.

1995-01-01

Realistic models of the outer heliosphere should consider that the interstellar cosmic-ray pressure becomes comparable to pressures in the solar wind at distances more than 100 AU from the Sun. The cosmic-ray pressure dynamically affects solar wind flow through deceleration. This effect, which occurs over a scale length of the order of the effective diffusion length at large radial distances, has important implications for cosmic-ray modulation and acceleration. As a first step toward solution of this nonlinear problem, a steady state numerical model was developed for a relatively cold spherical solar wind flow which encounters the confining isotropic pressure of the surrounding Galactic medium. This pressure is assumed to be dominated by energetic particles (Galactic cosmic rays). The system of equations, which are solved self-consistently, includes the relevant hydrodynamical equations for the solar wind flow and the spherical cosmic-ray transport equation. To avoid the closure parameter problem of the two-fluid model, the latter equation is solved for the energy-dependent cosmic-ray distribution function.

Enhanced air dispersion modelling at a typical Chinese nuclear power plant site: Coupling RIMPUFF with two advanced diagnostic wind models.

PubMed

Liu, Yun; Li, Hong; Sun, Sida; Fang, Sheng

2017-09-01

An enhanced air dispersion modelling scheme is proposed to cope with the building layout and complex terrain of a typical Chinese nuclear power plant (NPP) site. In this modelling, the California Meteorological Model (CALMET) and the Stationary Wind Fit and Turbulence (SWIFT) are coupled with the Risø Mesoscale PUFF model (RIMPUFF) for refined wind field calculation. The near-field diffusion coefficient correction scheme of the Atmospheric Relative Concentrations in the Building Wakes Computer Code (ARCON96) is adopted to characterize dispersion in building arrays. The proposed method is evaluated by a wind tunnel experiment that replicates the typical Chinese NPP site. For both wind speed/direction and air concentration, the enhanced modelling predictions agree well with the observations. The fraction of the predictions within a factor of 2 and 5 of observations exceeds 55% and 82% respectively in the building area and the complex terrain area. This demonstrates the feasibility of the new enhanced modelling for typical Chinese NPP sites. Copyright © 2017 Elsevier Ltd. All rights reserved.

REPRESENTATION OF ATMOSPHERIC MOTION IN MODELS OF REGIONAL-SCALE AIR POLLUTION

EPA Science Inventory

A method is developed for generating ensembles of wind fields for use in regional scale (1000 km) models of transport and diffusion. The underlying objective is a methodology for representing atmospheric motion in applied air pollution models that permits explicit treatment of th...

A hybrid formulation for the numerical simulation of condensed phase explosives

NASA Astrophysics Data System (ADS)

Michael, L.; Nikiforakis, N.

2016-07-01

In this article we present a new formulation and an associated numerical algorithm, for the simulation of combustion and transition to detonation of condensed-phase commercial- and military-grade explosives, which are confined by (or in general interacting with one or more) compliant inert materials. Examples include confined rate-stick problems and interaction of shock waves with gas cavities or solid particles in explosives. This formulation is based on an augmented Euler approach to account for the mixture of the explosive and its products, and a multi-phase diffuse interface approach to solve for the immiscible interaction between the mixture and the inert materials, so it is in essence a hybrid (augmented Euler and multi-phase) model. As such, it has many of the desirable features of the two approaches and, critically for our applications of interest, it provides the accurate recovery of temperature fields across all components. Moreover, it conveys a lot more physical information than augmented Euler, without the complexity of full multi-phase Baer-Nunziato-type models or the lack of robustness of augmented Euler models in the presence of more than two components. The model can sustain large density differences across material interfaces without the presence of spurious oscillations in velocity and pressure, and it can accommodate realistic equations of state and arbitrary (pressure- or temperature-based) reaction-rate laws. Under certain conditions, we show that the formulation reduces to well-known augmented Euler or multi-phase models, which have been extensively validated and used in practice. The full hybrid model and its reduced forms are validated against problems with exact (or independently-verified numerical) solutions and evaluated for robustness for rate-stick and shock-induced cavity collapse case-studies.

Launch Method for Kites in Low-Wind or No-Wind Conditions

NASA Technical Reports Server (NTRS)

Bland, Geoffrey; Miles, Ted

2012-01-01

Airborne observations using lightweight camera systems are desirable for a variety of applications. This system was contemplated as a method to provide a simple remote sensing aerial platform. Kites have been successfully employed for aerial observations, but have historically required natural wind or towing to become airborne. This new method negates this requirement, and widens the applicability of kites for carrying instrumentation. Applicability is primarily limited by the space available on the ground for launching. The innovation is a method for launching kites in low-wind or no-wind conditions. This method will enable instrumentation to be carried aloft using simple (or complex) kite-based systems, to obtain observations from an aerial perspective. This technique will provide access to altitudes of 100 meters or more over any area normally suited for kite flying. The duration of any observation is dependent on wind strength; however, the initial altitude is relatively independent. The system does not require any electrical or combustion-based elements. This technology was developed to augment local-scale airborne measurement capabilities suitable for Earth science research, agricultural productivity, and environmental observations. The method represents an extension of techniques often used in aeronautical applications for launching fixed-wing aircraft, such as sailplanes, using mechanical means not incorporated in the aircraft itself. The innovation consists of an elastic cord (for propulsive force), a tether extension (optional, for additional height), and the kite (instrumentation optional). Operation of the system is accomplished by fixing the elastic cord to ground (or equivalent), attaching the cord with/or without a tether extension to the kite, tensioning the system to store energy, and releasing the kite. The kite will climb until energy is dissipated.

Experimental wind tunnel study of a smart sensing skin for condition evaluation of a wind turbine blade

NASA Astrophysics Data System (ADS)

Downey, Austin; Laflamme, Simon; Ubertini, Filippo

2017-12-01

Condition evaluation of wind turbine blades is difficult due to their large size, complex geometry and lack of economic and scalable sensing technologies capable of detecting, localizing, and quantifying faults over a blade’s global area. A solution is to deploy inexpensive large area electronics over strategic areas of the monitored component, analogous to sensing skin. The authors have previously proposed a large area electronic consisting of a soft elastomeric capacitor (SEC). The SEC is highly scalable due to its low cost and ease of fabrication, and can, therefore, be used for monitoring large-scale components. A single SEC is a strain sensor that measures the additive strain over a surface. Recently, its application in a hybrid dense sensor network (HDSN) configuration has been studied, where a network of SECs is augmented with a few off-the-shelf strain gauges to measure boundary conditions and decompose the additive strain to obtain unidirectional surface strain maps. These maps can be analyzed to detect, localize, and quantify faults. In this work, we study the performance of the proposed sensing skin at conducting condition evaluation of a wind turbine blade model in an operational environment. Damage in the form of changing boundary conditions and cuts in the monitored substrate are induced into the blade. An HDSN is deployed onto the interior surface of the substrate, and the blade excited in a wind tunnel. Results demonstrate the capability of the HDSN and associated algorithms to detect, localize, and quantify damage. These results show promise for the future deployment of fully integrated sensing skins deployed inside wind turbine blades for condition evaluation.

Mars vertical axis wind machines: The design of a tornado vortex machine for use on Mars

NASA Technical Reports Server (NTRS)

Carlin, Daun; Dyhr, Amy; Kelly, Jon; Schmirler, J. Eric; Carlin, Mike; Hong, Won E.; Mahoney, Kamin

1994-01-01

Ever since Viking 1 and 2 landed on the surface of Mars in the summer of 1976, man has yearned to go back. But before man steps foot upon the surface of Mars, unmanned missions such as the Martian Soft Lander and Martian Subsurface Penetrator will precede him. Alternative renewable power sources must be developed to supply the next generation of surface exploratory spacecraft, since RTG's, solar cells, and long-life batteries all have their significant drawbacks. One such alternative is to take advantage of the unique Martian atmospheric conditions by designing a small scale, Martian wind power generator, capable of surviving impact and fulfilling the long term (2-5 years), low-level power requirements (1-2 Watts) of an unmanned surface probe. After investigation of several wind machines, a tornado vortex generator was chosen based upon its capability of theoretically augmenting and increasing the available power that may be extracted from average Martian wind speeds of approximately 7.5 m/s. The Martian Tornado Vortex Wind Generator stands 1 meter high and has a diameter of 0.5 m. Martian winds enter the base and shroud of the Tornado Vortex Generator at 7.5 m/s and are increased to an exit velocity of 13.657 m/s due to the vortex that is created. This results in a rapid pressure drop of 4.56 kg/s(exp 2) m across the vortex core which aids in producing a net power output of 1.1765 Watts. The report contains the necessary analysis and requirements needed to feasibly operate a low-level powered, unmanned, Martian surface probe.

System identification for precision control of a wingsailed GPS-guided catamaran

NASA Astrophysics Data System (ADS)

Elkaim, Gabriel Hugh

This thesis details the Atlantis project, whose aim is the design, development, and experimental testing of an autonomous wind-propelled marine craft. Functionally, such a vehicle is the marine equivalent of an unmanned aerial vehicle (UAV), and would serve similar purposes. The Atlantis project has been able to demonstrate an advance in control precision of a wind-propelled marine vehicle from typical commercial autopilot accuracy of 100 meters to an accuracy of better than one meter with a prototype based on a modified Prindle-19 light catamaran. The project involves substantial innovations in three areas: wind-propulsion system, overall system architecture, and sensors. The wind-propulsion system is a rigid wing-sail mounted vertically on bearings, mass balanced to allow free rotation in azimuth about a stub-mast. Aerodynamic torque about the stub-mast is trimmed using a flying tail mounted on booms aft of the wing. This arrangement allows the wing-sail to automatically attain the optimum angle to the wind, and weathervane into gusts without inducing large heeling moments. The sensor system uses differential Global Positioning System (DGPS) augmented by a low-cost attitude system based on accelerometer- and magnetometer-triads for position and velocity measurements. Accurate attitude determination is required to create a synthetic position sensor that is located at the center-of-gravity (c.g.) of the boat, rather than at the Global Positioning System (GPS) antenna location. A high-performance estimator/controller was implemented and tested on the full-scale prototype. The identified controllers were able to perform remarkably well, in the presence of wind and waves, tracking the desired line to within 0.3 meters (˜1 foot).

Mars vertical axis wind machines: The design of a tornado vortex machine for use on Mars

NASA Astrophysics Data System (ADS)

Carlin, Daun; Dyhr, Amy; Kelly, Jon; Schmirler, J. Eric; Carlin, Mike; Hong, Won E.; Mahoney, Kamin; Ralston, Michael

1994-06-01

Ever since Viking 1 and 2 landed on the surface of Mars in the summer of 1976, man has yearned to go back. But before man steps foot upon the surface of Mars, unmanned missions such as the Martian Soft Lander and Martian Subsurface Penetrator will precede him. Alternative renewable power sources must be developed to supply the next generation of surface exploratory spacecraft, since RTG's, solar cells, and long-life batteries all have their significant drawbacks. One such alternative is to take advantage of the unique Martian atmospheric conditions by designing a small scale, Martian wind power generator, capable of surviving impact and fulfilling the long term (2-5 years), low-level power requirements (1-2 Watts) of an unmanned surface probe. After investigation of several wind machines, a tornado vortex generator was chosen based upon its capability of theoretically augmenting and increasing the available power that may be extracted from average Martian wind speeds of approximately 7.5 m/s. The Martian Tornado Vortex Wind Generator stands 1 meter high and has a diameter of 0.5 m. Martian winds enter the base and shroud of the Tornado Vortex Generator at 7.5 m/s and are increased to an exit velocity of 13.657 m/s due to the vortex that is created. This results in a rapid pressure drop of 4.56 kg/s(exp 2) m across the vortex core which aids in producing a net power output of 1.1765 Watts. The report contains the necessary analysis and requirements needed to feasibly operate a low-level powered, unmanned, Martian surface probe.

Influences of wind and precipitation on different-sized particulate matter concentrations (PM2.5, PM10, PM2.5-10)

NASA Astrophysics Data System (ADS)

Zhang, Boen; Jiao, Limin; Xu, Gang; Zhao, Suli; Tang, Xin; Zhou, Yue; Gong, Chen

2018-06-01

Though it is recognized that meteorology has a great impact on the diffusion, accumulation and transport of air pollutants, few studies have investigated the impacts on different-sized particulate matter concentrations. We conducted a systematic comparative analysis and used the framework of generalized additive models (GAMs) to explore the influences of critical meteorological parameters, wind and precipitation, on PM2.5, PM10 and PM2.5-10 concentrations in Wuhan during 2013-2016. Overall, results showed that the impacts of wind and precipitation on different-sized PM concentrations are significantly different. The fine PM concentrations decreased gradually with the increase of wind speed, while coarse PM concentrations would increase due to dust resuspension under strong wind. Wind direction exerts limited influence on coarse PM concentrations. Wind speed was linearly correlated with log-transformed PM2.5 concentrations, but nonlinearly correlated with log-transformed PM10 and PM2.5-10 concentrations. We also found the PM2.5 and PM2.5-10 concentrations decreased by nearly 60 and 15% when the wind speed was up to 6 m/s, respectively, indicating a stronger negative impact of wind-speed on fine PM than coarse PM. The scavenging efficiency of precipitation on PM2.5-10 was over twice as high as on PM2.5. Our findings may help to understand the impacts of meteorology on different PM concentrations as well as discriminate and forecast variation in particulate matter concentrations.

The role of turbulent mixing in wind turbine wake recovery and wind array performance

NASA Astrophysics Data System (ADS)

Fruh, Wolf-Gerrit; Creech, Angus; Maguire, Eoghan

2014-05-01

The effect of wind turbine wakes in large offshore wind energy arrays can be a substantial factor in affecting the performance of turbines inside the array. Turbulent mixing plays a key role in the wake recovery, having a significant effect on the length over which the wake is strong enough to affect the performance other turbines significantly. We aim to highlight how turbulence affects wind turbine wakes, first by examining a high resolution CFD model of a single turbine wake validated by LIDAR measurements [1], and secondly with a much larger CFD simulation of Lillgrund offshore wind farm, validated with SCADA data [2]. By comparing the decay rates behind single turbines in environments of different surrounding surface features, ranging from ideal free-slip wind tunnels to mixed-vegetation hills, we suggest that the decay rate of turbine wakes are enhanced by free-stream turbulence, created by topography and ground features. In the context of Lillgrund wind farm, observations and computational results suggest that the wakes created by the turbines in the leading row facing the wind decay much slower than those in second row, or further into the turbine array. This observation can be explained by the diffusive action of upwind turbulence breaking up the wake generated by a turbine rotor. Angus CW Creech, Wolf-Gerrit Früh, Peter Clive (2012). Actuator volumes and hradaptive methods for threedimensional simulation of wind turbine wakes and performance. Wind Energy Vol.15, 847 - 863. Angus C.W. Creech, Wolf-Gerrit Früh, A. Eoghan Maguire (2013). High-resolution CFD modelling of Lillgrund Wind farm. Renewable Energies and Power Quality Journal, Vol. 11

Turbulent kinetics of a large wind farm and their impact in the neutral boundary layer

DOE PAGES

Na, Ji Sung; Koo, Eunmo; Munoz-Esparza, Domingo; ...

2015-12-28

High-resolution large-eddy simulation of the flow over a large wind farm (64 wind turbines) is performed using the HIGRAD/FIRETEC-WindBlade model, which is a high-performance computing wind turbine–atmosphere interaction model that uses the Lagrangian actuator line method to represent rotating turbine blades. These high-resolution large-eddy simulation results are used to parameterize the thrust and power coefficients that contain information about turbine interference effects within the wind farm. Those coefficients are then incorporated into the WRF (Weather Research and Forecasting) model in order to evaluate interference effects in larger-scale models. In the high-resolution WindBlade wind farm simulation, insufficient distance between turbines createsmore » the interference between turbines, including significant vertical variations in momentum and turbulent intensity. The characteristics of the wake are further investigated by analyzing the distribution of the vorticity and turbulent intensity. Quadrant analysis in the turbine and post-turbine areas reveals that the ejection motion induced by the presence of the wind turbines is dominant compared to that in the other quadrants, indicating that the sweep motion is increased at the location where strong wake recovery occurs. Regional-scale WRF simulations reveal that although the turbulent mixing induced by the wind farm is partly diffused to the upper region, there is no significant change in the boundary layer depth. The velocity deficit does not appear to be very sensitive to the local distribution of turbine coefficients. However, differences of about 5% on parameterized turbulent kinetic energy were found depending on the turbine coefficient distribution. Furthermore, turbine coefficients that consider interference in the wind farm should be used in wind farm parameterization for larger-scale models to better describe sub-grid scale turbulent processes.« less

The interplay between star formation and the nuclear environment of our Galaxy: deep X-ray observations of the Galactic centre Arches and Quintuplet clusters

NASA Astrophysics Data System (ADS)

Wang, Q. Daniel; Dong, Hui; Lang, Cornelia

2006-09-01

The Galactic centre (GC) provides a unique laboratory for a detailed examination of the interplay between massive star formation and the nuclear environment of our Galaxy. Here, we present a 100-ks Chandra Advanced CCD Imaging Spectrometer (ACIS) observation of the Arches and Quintuplet star clusters. We also report on a complementary mapping of the dense molecular gas near the Arches cluster made with the Owens Valley Millimeter Array. We present a catalogue of 244 point-like X-ray sources detected in the observation. Their number-flux relation indicates an overpopulation of relatively bright X-ray sources, which are apparently associated with the clusters. The sources in the core of the Arches and Quintuplet clusters are most likely extreme colliding wind massive star binaries. The diffuse X-ray emission from the core of the Arches cluster has a spectrum showing a 6.7-keV emission line and a surface intensity profile declining steeply with radius, indicating an origin in a cluster wind. In the outer regions near the Arches cluster, the overall diffuse X-ray enhancement demonstrates a bow shock morphology and is prominent in the Fe Kα 6.4-keV line emission with an equivalent width of ~1.4 keV. Much of this enhancement may result from an ongoing collision between the cluster and the adjacent molecular cloud, which have a relative velocity >~120km-1. The older and less-compact Quintuplet cluster contains much weaker X-ray sources and diffuse emission, probably originating from low-mass stellar objects as well as a cluster wind. However, the overall population of these objects, constrained by the observed total diffuse X-ray luminosities, is substantially smaller than expected for both clusters, if they have normal Miller & Scalo initial mass functions. This deficiency of low-mass objects may be a manifestation of the unique star formation environment of the GC, where high-velocity cloud-cloud and cloud-cluster collisions are frequent.

Thrust Augmenting Ejectors

DTIC Science & Technology

1975-06-01

approximately four . Presently referred to as the hypermixing nozzle (See Figure 37). d. Alternating exit nozzle - same as c, but the elemental aspect ratio...UL 0 Reynolds number, defined as R . In addition, due to the double symmetry about the y and z axes, the analysis will treat only one quadrant of the...in the duct of diffuser. Then from the conservation of mass A~x Atx) where A(x) g(x) tl(x) is the streamwise area distribution in one quadrant

Diminutive Porcelain Ascending Aorta With Supravalvular Aortic Stenosis.

PubMed

Houmsse, Mustafa; McDavid, Asia; Kilic, Ahmet

2018-05-01

This report describes the case of a 49-year-old man with a medical history significant for congenital aortic stenosis. The patient presented with progressive shortness of breath and decreased stamina and was found to have a concentric, diminutive porcelain ascending aorta with diffuse supravalvular aortic stenosis. We describe treatment with an aortic root augmentation and Bentall procedure using hypothermic circulatory arrest. Copyright © 2018 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

An evaluation and assessment of flow quality in selected NASA wind tunnels

NASA Technical Reports Server (NTRS)

Harvey, W. D.; Stainback, P. C.; Owen, F. K.

1983-01-01

Tests have been conducted in a number of NASA wind tunnels to measure disturbance levels and spectra in their respective settling chambers, test sections, and diffusers to determine the sources of their disturbances. The present data supplements previous results in other NASA tunnels and adds to the ongoing acquisition of a disturbance level data base. The present results also serve to explain flow related sources which cause relatively large disturbance amplitudes at discrete frequencies. The installation of honeycomb, screens, and acoustic baffles in or upstream of the settling chamber can significantly reduce the disturbance levels.

The Use of Steady and Unsteady Detonation Waves for Propulsion Systems

NASA Technical Reports Server (NTRS)

Adelman, Henry G.; Menees, Gene P.; Cambier, Jean-Luc; Bowles, Jeffrey V.; Cavolowsky, John A. (Technical Monitor)

1995-01-01

Detonation wave enhanced supersonic combustors such as the Oblique Detonation Wave Engine (ODWE) are attractive propulsion concepts for hypersonic flight. These engines utilize detonation waves to enhance fuel-air mixing and combustion. The benefits of wave combustion systems include shorter and lighter engines which require less cooling and generate lower internal drag. These features allow air-breathing operation at higher Mach numbers than the diffusive burning scramjet delaying the need for rocket engine augmentation. A comprehensive vehicle synthesis code has predicted the aerodynamic characteristics and structural size and weight of a typical single-stage-to-orbit vehicle using an ODWE. Other studies have focused on the use of unsteady or pulsed detonation waves. For low speed applications, pulsed detonation engines (PDE) have advantages in low weight and higher efficiency than turbojets. At hypersonic speeds, the pulsed detonations can be used in conjunction with a scramjet type engine to enhance mixing and provide thrust augmentation.

Advection-diffusion model for the simulation of air pollution distribution from a point source emission

NASA Astrophysics Data System (ADS)

Ulfah, S.; Awalludin, S. A.; Wahidin

2018-01-01

Advection-diffusion model is one of the mathematical models, which can be used to understand the distribution of air pollutant in the atmosphere. It uses the 2D advection-diffusion model with time-dependent to simulate air pollution distribution in order to find out whether the pollutants are more concentrated at ground level or near the source of emission under particular atmospheric conditions such as stable, unstable, and neutral conditions. Wind profile, eddy diffusivity, and temperature are considered in the model as parameters. The model is solved by using explicit finite difference method, which is then visualized by a computer program developed using Lazarus programming software. The results show that the atmospheric conditions alone influencing the level of concentration of pollutants is not conclusive as the parameters in the model have their own effect on each atmospheric condition.

Turbulent vertical diffusivity in the sub-tropical stratosphere

NASA Astrophysics Data System (ADS)

Pisso, I.; Legras, B.

2008-02-01

Vertical (cross-isentropic) mixing is produced by small-scale turbulent processes which are still poorly understood and paramaterized in numerical models. In this work we provide estimates of local equivalent diffusion in the lower stratosphere by comparing balloon borne high-resolution measurements of chemical tracers with reconstructed mixing ratio from large ensembles of random Lagrangian backward trajectories using European Centre for Medium-range Weather Forecasts analysed winds and a chemistry-transport model (REPROBUS). We focus on a case study in subtropical latitudes using data from HIBISCUS campaign. An upper bound on the vertical diffusivity is found in this case study to be of the order of 0.5 m2 s-1 in the subtropical region, which is larger than the estimates at higher latitudes. The relation between diffusion and dispersion is studied by estimating Lyapunov exponents and studying their variation according to the presence of active dynamical structures.

Retrospective and prospective analysis of policy incentives for wind power in Portugal

NASA Astrophysics Data System (ADS)

Pena Cabra, Ivonne A.

Concerns over climate change impacts, goals to increase environmental sustainability, and questions about the reliability of fuel supply have led several countries to pursue the goal of increasing the share of renewable energy sources in their electricity grid. Portugal is one of the leading countries for wind electricity generation. Wind diffusion in Portugal started in the early 2000's and in 2013 wind electricity generation accounted for more than 24% (REN 2013b). The large share of wind in Portuguese electricity production is a consequence of European Union (E.U.) mandates and national policies, mainly feed-in tariffs. Discussions on the appropriate policy design and level of incentive to promote renewable energy adoption and meet further renewable capacity goals are ongoing in Portugal, namely in what concerns the level and duration of feed-in tariffs that should be provided to independent power producers. This, in turn, raises the question of whether the past feed-in tariff levels were well designed to achieve the goals of a larger penetration of renewables in the Portuguese grid. The policies to induce wind adoption have led to a growth in wind installed capacity and share of electricity generated by wind in Portugal from less than 1% in 2000 to approximately 24% in 2013, but questions arise on their cost-effectiveness and whether alternative policy designs would have led to the same goal. The Portuguese wind feed-in tariffs are a guaranteed incentive which has varied between 85- 180/MWh over the last 20 years (ERSE 2011), and remained approximately constant since 2001 at $101/MWh. They are currently guaranteed for 20 years of production or 44GWh of electricity generation per MW installed (Diario da Republica 2013) - the longest period among countries with high wind electricity share. They do not incorporate any digression rate besides inflation, and are guaranteed for every unit of electricity fed to the grid. There are no power plants that have already been decommissioned despite being in operation for more than 20 years, favoring from new, detailed and hard-to-follow agreements in the legislation. All wind parks that are currently in operation have received feed-in tariffs since they connected to the grid, and are expected to keep receiving them at least until December 2019, and up to December 2036 - depending on year of connection and agreement under the most recent legislation (Diario da Republica 2013). The 2020 renewable energy goals in Portugal include having 6.8 GW of installed wind capacity, which implies the connection of 2 GW in the next years. If no further grid investments are made and wind capacity increases up to 100 MW to the connection point that we analyze, total annual electricity spill is likely to range the 20% to 40%. If the connection grid policy is designed to allow for wind spill, already 'occupied' connection points will be available to new entrants, lowering the total investment costs for new wind parks and increasing their profitability. This thesis is divided in three main parts: a first introductory section, a retrospective study of wind power in Portugal and a prospective analysis of the Portuguese wind power sector. The introductory section is a brief overview of the global renewable status, described in Chapter 1. Chapter 2 and Chapter 3 compile a retrospective study of wind power and the policies that have incentivized wind diffusion. We include in the discussion some references to the future wind power goals, but the results and policy recommendations are directed towards the existing connected wind power capacity. (Abstract shortened by UMI.).

THE BORN-AGAIN PLANETARY NEBULA A78: AN X-RAY TWIN OF A30

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toalá, J. A.; Guerrero, M. A.; Marquez-Lugo, R. A.

We present the XMM-Newton discovery of X-ray emission from the planetary nebula (PN) A78, the second born-again PN detected in X-rays apart from A30. These two PNe share similar spectral and morphological characteristics: they harbor diffuse soft X-ray emission associated with the interaction between the H-poor ejecta and the current fast stellar wind and a point-like source at the position of the central star (CSPN). We present the spectral analysis of the CSPN, using for the first time an NLTE code for expanding atmospheres that takes line blanketing into account for the UV and optical spectra. The wind abundances aremore » used for the X-ray spectral analysis of the CSPN and the diffuse emission. The X-ray emission from the CSPN in A78 can be modeled by a single C VI emission line, while the X-ray emission from its diffuse component is better described by an optically thin plasma emission model with a temperature of kT = 0.088 keV (T ≈ 1.0 × 10{sup 6} K). We estimate X-ray luminosities in the 0.2-2.0 keV energy band of L {sub X,} {sub CSPN} = (1.2 ± 0.3) × 10{sup 31} erg s{sup –1} and L {sub X,} {sub DIFF} = (9.2 ± 2.3) × 10{sup 30} erg s{sup –1} for the CSPN and diffuse components, respectively.« less

Some considerations about Gaussian basis sets for electric property calculations

NASA Astrophysics Data System (ADS)

Arruda, Priscilla M.; Canal Neto, A.; Jorge, F. E.

Recently, segmented contracted basis sets of double, triple, and quadruple zeta valence quality plus polarization functions (XZP, X = D, T, and Q, respectively) for the atoms from H to Ar were reported. In this work, with the objective of having a better description of polarizabilities, the QZP set was augmented with diffuse (s and p symmetries) and polarization (p, d, f, and g symmetries) functions that were chosen to maximize the mean dipole polarizability at the UHF and UMP2 levels, respectively. At the HF and B3LYP levels of theory, electric dipole moment and static polarizability for a sample of molecules were evaluated. Comparison with experimental data and results obtained with a similar size basis set, whose diffuse functions were optimized for the ground state energy of the anion, was done.

Small particle transport across turbulent nonisothermal boundary layers

NASA Technical Reports Server (NTRS)

Rosner, D. E.; Fernandez De La Mora, J.

1982-01-01

The interaction between turbulent diffusion, Brownian diffusion, and particle thermophoresis in the limit of vanishing particle inertial effects is quantitatively modeled for applications in gas turbines. The model is initiated with consideration of the particle phase mass conservation equation for a two-dimensional boundary layer, including the thermophoretic flux term directed toward the cold wall. A formalism of a turbulent flow near a flat plate in a heat transfer problem is adopted, and variable property effects are neglected. Attention is given to the limit of very large Schmidt numbers and the particle concentration depletion outside of the Brownian sublayer. It is concluded that, in the parameter range of interest, thermophoresis augments the high Schmidt number mass-transfer coefficient by a factor equal to the product of the outer sink and the thermophoretic suction.

Solar wind noble gases and nitrogen in metal from lunar soil 68501

NASA Technical Reports Server (NTRS)

Becker, Richard H.; Pepin, Robert O.

1994-01-01

Noble gases and N were analyzed in handpicked metal separates from lunar soil 68501 by a combination of step-wise combustions and pyrolyses. Helium and Ne were found to be unfractionated with respect to one another when normalized to solar abundances, for both the bulk sample and for all but the highest temperature steps. However, they are depleted relative to Ar, Kr and Xe by at least a factor of 5. The heavier gases exhibit mass-dependent fractionation relative to solar system abundance ratios but appear unfractionated, both in the bulk metal and in early temperature steps, when compared to relative abundances derived from lunar ilmenite 71501 by chemical etching, recently put forward as representing the abundance ratios in solar wind. Estimates of the contribution of solar energetic particles (SEP) to the originally implanted solar gases, derived from a basic interpretation of He and Ne isotopes, yield values of about 10%. Analysis of the Ar isotopes requires a minimum of 20% SEP, and Kr isotopes, using our preferred composition for solar wind Kr, yield a result that overlaps both these values. It is possible to reconcile the data from these gases if significant loss of solar wind Ar, Kr and presumably Xe has occurred relative to the SEP component, most likely by erosive processes that are mass independent, although mass-dependent losses (Ar greater than Kr greater than Xe) cannot be excluded. If such losses did occur, the SEP contribution to the solar implanted gases must have been no more than a few percent. Nitrogen is a mixture of indigenous meteoritic N, whose isotopic composition is inferred to be relatively light, and implanted solar N, which has probably undergone diffusive redistribution and fractionation. If the heavy noble gases have not undergone diffusive loss, then N/Ar in the solar wind can be inferred to be at least several times the accepted solar ratio. The solar wind N appears, even after correction for fractionation effects, to have a minimum delta N-15 value equal to or greater than +150% and a more probable value equal to or greater than +200%.

Prediction of AL and Dst Indices from ACE Measurements Using Hybrid Physics/Black-Box Techniques

NASA Astrophysics Data System (ADS)

Spencer, E.; Rao, A.; Horton, W.; Mays, L.

2008-12-01

ACE measurements of the solar wind velocity, IMF and proton density is used to drive a hybrid Physics/Black- Box model of the nightside magnetosphere. The core physics is contained in a low order nonlinear dynamical model of the nightside magnetosphere called WINDMI. The model is augmented by wavelet based nonlinear mappings between the solar wind quantities and the input into the physics model, followed by further wavelet based mappings of the model output field aligned currents onto the ground based magnetometer measurements of the AL index and Dst index. The black box mappings are introduced at the input stage to account for uncertainties in the way the solar wind quantities are transported from the ACE spacecraft at L1 to the magnetopause. Similar mappings are introduced at the output stage to account for a spatially and temporally varying westward auroral electrojet geometry. The parameters of the model are tuned using a genetic algorithm, and trained using the large geomagnetic storm dataset of October 3-7 2000. It's predictive performance is then evaluated on subsequent storm datasets, in particular the April 15-24 2002 storm. This work is supported by grant NSF 7020201

Blended-Wing-Body Transonic Aerodynamics: Summary of Ground Tests and Sample Results

NASA Technical Reports Server (NTRS)

Carter, Melissa B.; Vicroy, Dan D.; Patel, Dharmendra

2009-01-01

The Blended-Wing-Body (BWB) concept has shown substantial performance benefits over conventional aircraft configuration with part of the benefit being derived from the absence of a conventional empennage arrangement. The configuration instead relies upon a bank of trailing edge devices to provide control authority and augment stability. To determine the aerodynamic characteristics of the aircraft, several wind tunnel tests were conducted with a 2% model of Boeing's BWB-450-1L configuration. The tests were conducted in the NASA Langley Research Center's National Transonic Facility and the Arnold Engineering Development Center s 16-Foot Transonic Tunnel. Characteristics of the configuration and the effectiveness of the elevons, drag rudders and winglet rudders were measured at various angles of attack, yaw angles, and Mach numbers (subsonic to transonic speeds). The data from these tests will be used to develop a high fidelity simulation model for flight dynamics analysis and also serve as a reference for CFD comparisons. This paper provides an overview of the wind tunnel tests and examines the effects of Reynolds number, Mach number, pitch-pause versus continuous sweep data acquisition and compares the data from the two wind tunnels.

What water isotopes tell us about water cycle responses to climate change

NASA Astrophysics Data System (ADS)

Raudzens Bailey, A.; Singh, H. A.; Nusbaumer, J. M.; Dee, S.; Blossey, P. N.; Posmentier, E. S.

2017-12-01

The water cycle is expected to respond strongly to rising global temperatures. Models predict regional imbalances in evaporation and precipitation will intensify, resulting in a slowing of the large-scale circulation. This slowing will extend the moisture length scale by increasing the amount of time water resides in the atmosphere. However, verifying these changes observationally is challenging. Isotope ratios in water vapor and precipitation represent an integrated record of moisture's journey from evaporative source to precipitation sink. Consequently, they provide a unique opportunity to identify changes in moisture length scale associated with shifts in regional hydrologic balance. Leveraging satellite retrievals, box models, climate simulations, and in situ data, this presentation demonstrates how water isotope ratios can be used to estimate water cycle changes over the historical period and into the future. These changes are closely linked to variations in the divergence of atmospheric moisture fluxes, which result from variations in specific humidity, wind direction, and wind speed. This presentation highlights the extent to which isotopic measurements allow us to track changes in the dynamic, or wind-driven, component of moisture transport and to investigate whether remote moisture contributions are becoming increasingly important in augmenting local precipitation.

Thermosphere-Ionosphere Fe/Fe+ (TIFe) Layers and Their Coupling with Geomagnetic Storms and Solar Wind

NASA Astrophysics Data System (ADS)

Chu, X.; Xu, Z.; Zhao, J.; Yu, Z.; Knipp, D. J.; Kilcommons, L. M.; Chen, C.; Fong, W.; Barry, I. F.; Hartinger, M.

2016-12-01

The discovery of thermospheric neutral Fe layers by lidar observations in Antarctica has opened a new door to explore the space-atmosphere interactions with ground-based instruments, especially in the least understood but crucially important altitude range of 100-200 km. These neutral metal layers provide excellent tracers for modern resonance lidars to measure the neutral wind and temperature directly, complementing the radar measurements of the ionosphere and the magnetometer measurements of the geomagnetic field. Even more exciting, the neutral metal layers in the thermosphere provide a natural laboratory to test our fundamental understandings of the atmosphere-ionosphere-magnetosphere (AIM) coupling and processes. The stunning Fe layer event on 28 May 2011 with clear gravity wave signatures has been simulated successfully with the University of Colorado Thermosphere-Ionosphere Fe/Fe+ (TIFe) model, confirming the theoretical hypothesis that such thermospheric Fe layers are produced through the neutralization of converged Fe+layers. Over 5.5 years of lidar observations at McMurdo have revealed many more cases with variety of patterns - besides the `gravity wave' patterns, there are `diffusive' patterns with both upward and downward phase progressions of Fe layers, and `superposition' patterns with both gravity wave signature and diffusive background. Surprisingly, these Fe layer events exhibit close correlations with geomagnetic storms. They also correspond to remarkable activity of extreme solar wind events, e.g., high-speed stream (HSS) and coronal mass ejection (CME), etc. This paper conducts a systematic investigation of the coupling among TIFe layers, geomagnetic storms, solar wind and IMF via combining ground-based lidar, magnetometer, and SuperDARN data with DMSP, ACE and WIND satellite data along with the TIFe model simulations. We aim to quantitatively determine the relationship between TIFe and magnetic storms, and explore the mechanisms responsible for such correlations. The new insights gained through this investigation will certainly advance our understandings of the AIM coupling processes, especially the neutral atmosphere responses to geomagnetic storms and solar activity.

Turbulent Structures in a Pine Forest with a Deep and Sparse Trunk Space: Stand and Edge Regions

NASA Astrophysics Data System (ADS)

Dupont, Sylvain; Irvine, Mark R.; Bonnefond, Jean-Marc; Lamaud, Eric; Brunet, Yves

2012-05-01

Forested landscapes often exhibit large spatial variability in vertical and horizontal foliage distributions. This variability may affect canopy-atmosphere exchanges through its action on the development of turbulent structures. Here we investigate in neutral stratification the turbulent structures encountered in a maritime pine forest characterized by a high, dense foliated layer associated with a deep and sparse trunk space. Both stand and edge regions are considered. In situ measurements and the results of large-eddy simulations are used and analyzed together. In stand conditions, far from the edge, canopy-top structures appear strongly damped by the dense crown layer. Turbulent wind fluctuations within the trunk space, where the momentum flux vanishes, are closely related to these canopy-top structures through pressure diffusion. Consequently, autocorrelation and spectral analyses are not quite appropriate to characterize the vertical scale of coherent structures in this type of canopy, as pressure diffusion enhances the actual scale of structures. At frequencies higher than those associated with canopy-top structures, wind fluctuations related to wake structures developing behind tree stems are observed within the trunk space. They manifest themselves in wind velocity spectra as secondary peaks in the inertial subrange region, confirming the hypothesis of spectral short-cuts in vegetation canopies. In the edge region specific turbulent structures develop just below the crown layer, in addition to canopy-top structures. They are generated by the wind shear induced by the sub-canopy wind jet that forms at the edge. These structures provide a momentum exchange mechanism similar to that observed at the canopy top but in the opposite direction and with a lower magnitude. They may develop as in plane mixing-layer flows, with some perturbations induced by canopy-top structures. Wake structures are also observed within the trunk space in the edge region.

The time variability of Jupiter's synchrotron radiation

NASA Astrophysics Data System (ADS)

Bolton, Scott Jay

1991-02-01

The time variability of the Jovian synchrotron emission is investigated by analyzing radio observations of Jupiter at decimetric wavelengths. The observations are composed from two distinct sets of measurements addressing both short term (days to weeks) and long term (months to years) variability. The study of long term variations utilizes a set of measurements made several times each month with the NASA Deep Space Network (DNS) antennas operating at 2295 MHz (13.1 cm). The DSN data set, covering 1971 through 1985, is compared with a set of measurements of the solar wind from a number of Earth orbiting spacecraft. The analysis indicates a maximum correlation between the synchrotron emission and the solar wind ram pressure with a two year time lag. Physical mechanisms affecting the synchrotron emission are discussed with an emphasis on radial diffusion. Calculations are performed that suggest the correlation is consistent with inward adiabatic diffusion of solar wind particles driven by Brice's model of ionospheric neutral wind convection (Brice 1972). The implication is that the solar wind could be a source of particles of Jupiter's radiation belts. The investigation of short term variability focuses on a three year Jupiter observing program using the University of California's Hat Creek radio telescope operating at 1400 MHz (21 cm). Measurements are made every two days during the months surrounding opposition. Results from the three year program suggest short term variability near the 10-20 percent level but should be considered inconclusive due to scheduling and observational limitations. A discussion of magneto-spheric processes on short term timescales identifies wave-particle interactions as a candidate source. Further analysis finds that the short term variations could be related to whistler mode wave-particles interactions in the radiation belts associated with atmospheric lightning on Jupiter. However, theoretical calculations on wave particle interactions imply thought if whistler mode waves are to interact with the synchrotron emitting electrons.

Solar Drivers of 11-yr and Long-Term Cosmic Ray Modulation

NASA Technical Reports Server (NTRS)

Cliver, E. W.; Richardson, I. G.; Ling, A. G.

2011-01-01

In the current paradigm for the modulation of galactic cosmic rays (GCRs), diffusion is taken to be the dominant process during solar maxima while drift dominates at minima. Observations during the recent solar minimum challenge the pre-eminence of drift: at such times. In 2009, the approx.2 GV GCR intensity measured by the Newark neutron monitor increased by approx.5% relative to its maximum value two cycles earlier even though the average tilt angle in 2009 was slightly larger than that in 1986 (approx.20deg vs. approx.14deg), while solar wind B was significantly lower (approx.3.9 nT vs. approx.5.4 nT). A decomposition of the solar wind into high-speed streams, slow solar wind, and coronal mass ejections (CMEs; including postshock flows) reveals that the Sun transmits its message of changing magnetic field (diffusion coefficient) to the heliosphere primarily through CMEs at solar maximum and high-speed streams at solar minimum. Long-term reconstructions of solar wind B are in general agreement for the approx. 1900-present interval and can be used to reliably estimate GCR intensity over this period. For earlier epochs, however, a recent Be-10-based reconstruction covering the past approx. 10(exp 4) years shows nine abrupt and relatively short-lived drops of B to < or approx.= 0 nT, with the first of these corresponding to the Sporer minimum. Such dips are at variance with the recent suggestion that B has a minimum or floor value of approx.2.8 nT. A floor in solar wind B implies a ceiling in the GCR intensity (a permanent modulation of the local interstellar spectrum) at a given energy/rigidity. The 30-40% increase in the intensity of 2.5 GV electrons observed by Ulysses during the recent solar minimum raises an interesting paradox that will need to be resolved.

Chandra Reveals the X-ray Glint in the Cat's Eye

NASA Astrophysics Data System (ADS)

Chu, Y.-H.; Guerrero, M. A.; Gruendl, R. A.; Kaler, J. B.; Williams, R. M.

2000-12-01

The Cat's Eye Nebula, also known as NGC 6543, has perhaps the most intriguing and complex morphology among planetary nebulae (PNe). It is a known X-ray source, but previous observations were unable to resolve the distribution of the X-rays. Recent Chandra ACIS-S observations of the Cat's Eye clearly resolved the X-ray emission into a point source at the central star and diffuse emission confined within the central elliptical shell and two lobes along the major axis. Analyses of the spectra of the central shell and the two lobes show that the hot gas in the Cat's Eye has temperatures of ~1.6x106 K and that its abundances are similar to those of the fast stellar wind and not those of the nebula. The spectral variations among these regions can be explained by different amounts of absorption through the nebula along the line of sight. It is puzzling that the X-ray-emitting gas appears to be comprised of mostly stellar wind material yet its temperature is much lower than expected for an adiabatically shocked stellar wind. Extremely efficient cooling mechanisms are needed. The study of X-ray emission from the Cat's Eye will help us understand why most PNe do not have detectable diffuse X-ray emission, and thus provide insights on the formation and evolution of PNe. This work is supported by the CXC grant number GO0-1004X.

Spatially-Dependent Modelling of Pulsar Wind Nebula G0.9+0.1

NASA Astrophysics Data System (ADS)

van Rensburg, C.; Krüger, P. P.; Venter, C.

2018-03-01

We present results from a leptonic emission code that models the spectral energy distribution of a pulsar wind nebula by solving a Fokker-Planck-type transport equation and calculating inverse Compton and synchrotron emissivities. We have created this time-dependent, multi-zone model to investigate changes in the particle spectrum as they traverse the pulsar wind nebula, by considering a time and spatially-dependent B-field, spatially-dependent bulk particle speed implying convection and adiabatic losses, diffusion, as well as radiative losses. Our code predicts the radiation spectrum at different positions in the nebula, yielding the surface brightness versus radius and the nebular size as function of energy. We compare our new model against more basic models using the observed spectrum of pulsar wind nebula G0.9+0.1, incorporating data from H.E.S.S. as well as radio and X-ray experiments. We show that simultaneously fitting the spectral energy distribution and the energy-dependent source size leads to more stringent constraints on several model parameters.

Non-thermal Processes in Colliding-wind Massive Binaries: the Contribution of Simbol-X to a Multiwavelength Investigation

NASA Astrophysics Data System (ADS)

De Becker, Michaël; Blomme, Ronny; Micela, Giusi; Pittard, Julian M.; Rauw, Gregor; Romero, Gustavo E.; Sana, Hugues; Stevens, Ian R.

2009-05-01

Several colliding-wind massive binaries are known to be non-thermal emitters in the radio domain. This constitutes strong evidence for the fact that an efficient particle acceleration process is at work in these objects. The acceleration mechanism is most probably the Diffusive Shock Acceleration (DSA) process in the presence of strong hydrodynamic shocks due to the colliding-winds. In order to investigate the physics of this particle acceleration, we initiated a multiwavelength campaign covering a large part of the electromagnetic spectrum. In this context, the detailed study of the hard X-ray emission from these sources in the SIMBOL-X bandpass constitutes a crucial element in order to probe this still poorly known topic of astrophysics. It should be noted that colliding-wind massive binaries should be considered as very valuable targets for the investigation of particle acceleration in a similar way as supernova remnants, but in a different region of the parameter space.

Spatially dependent modelling of pulsar wind nebula G0.9+0.1

NASA Astrophysics Data System (ADS)

van Rensburg, C.; Krüger, P. P.; Venter, C.

2018-07-01

We present results from a leptonic emission code that models the spectral energy distribution of a pulsar wind nebula by solving a Fokker-Planck-type transport equation and calculating inverse Compton and synchrotron emissivities. We have created this time-dependent, multizone model to investigate changes in the particle spectrum as they traverse the pulsar wind nebula, by considering a time and spatially dependent B-field, spatially dependent bulk particle speed implying convection and adiabatic losses, diffusion, as well as radiative losses. Our code predicts the radiation spectrum at different positions in the nebula, yielding the surface brightness versus radius and the nebular size as function of energy. We compare our new model against more basic models using the observed spectrum of pulsar wind nebula G0.9+0.1, incorporating data from H.E.S.S. as well as radio and X-ray experiments. We show that simultaneously fitting the spectral energy distribution and the energy-dependent source size leads to more stringent constraints on several model parameters.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stagg, Alan K; Yoon, Su-Jong

This report describes the Consortium for Advanced Simulation of Light Water Reactors (CASL) work conducted for completion of the Thermal Hydraulics Methods (THM) Level 3 Milestone THM.CFD.P11.02: Hydra-TH Extensions for Multispecies and Thermosolutal Convection. A critical requirement for modeling reactor thermal hydraulics is to account for species transport within the fluid. In particular, this capability is needed for modeling transport and diffusion of boric acid within water for emergency, reactivity-control scenarios. To support this need, a species transport capability has been implemented in Hydra-TH for binary systems (for example, solute within a solvent). A species transport equation is solved formore » the species (solute) mass fraction, and both thermal and solutal buoyancy effects are handled with specification of a Boussinesq body force. Species boundary conditions can be specified with a Dirichlet condition on mass fraction or a Neumann condition on diffusion flux. To enable enhanced species/fluid mixing in turbulent flow, the molecular diffusivity for the binary system is augmented with a turbulent diffusivity in the species transport calculation. The new capabilities are demonstrated by comparison of Hydra-TH calculations to the analytic solution for a thermosolutal convection problem, and excellent agreement is obtained.« less

Impact of AGN and nebular emission on the estimation of stellar properties of galaxies

NASA Astrophysics Data System (ADS)

Cardoso, Leandro Saul Machado

The aim of this PhD thesis is to apply tools from stochastic modeling to wind power, speed and direction data, in order to reproduce their empirically observed statistical features. In particular, the wind energy conversion process is modeled as a Langevin process, which allows to describe its dynamics with only two coefficients, namely the drift and the diffusion coefficients. Both coefficients can be directly derived from collected time-series and this so-called Langevin method has proved to be successful in several cases. However, the application to empirical data subjected to measurement noise sources in general and the case of wind turbines in particular poses several challenges and this thesis proposes methods to tackle them. To apply the Langevin method it is necessary to have data that is both stationary and Markovian, which is typically not the case. Moreover, the available time-series are often short and have missing data points, which affects the estimation of the coefficients. This thesis proposes a new methodology to overcome these issues by modeling the original data with a Markov chain prior to the Langevin analysis. The latter is then performed on data synthesized from the Markov chain model of wind data. Moreover, it is shown that the Langevin method can be applied to low sample rate wind data, namely 10-minute average data. The method is then extended in two different directions. First, to tackle non-stationary data sets. Wind data often exhibits daily patterns due to the solar cycle and this thesis proposes a method to consider these daily patterns in the analysis of the timeseries. For that, a cyclic Markov model is developed for the data synthesis step and subsequently, for each time of the day, a separate Langevin analysis of the wind energy conversion system is performed. Second, to resolve the dynamical stochastic process in the case it is spoiled by measurement noise. When working with measurement data a challenge can be posed by the quality of the data in itself. Often measurement devices add noise to the time-series that is different from the intrinsic noise of the underlying stochastic process and can even be time-correlated. This spoiled data, analyzed with the Langevin method leads to distorted drift and diffusion coefficients. This thesis proposes a direct, parameter-free way to extract the Langevin coefficients as well as the parameters of the measurement noise from spoiled data. Put in a more general context, the method allows to disentangle two superposed independent stochastic processes. Finally, since a characteristic of wind energy that motivates this stochastic modeling framework is the fluctuating nature of wind itself, several issues raise when it comes to reserve commitment or bidding on the liberalized energy market. This thesis proposes a measure to quantify the risk-returnratio that is associated to wind power production conditioned to a wind park state. The proposed state of the wind park takes into account data from all wind turbines constituting the park and also their correlations at different time lags. None

A high resolution WRF model for wind energy forecasting

NASA Astrophysics Data System (ADS)

Vincent, Claire Louise; Liu, Yubao

2010-05-01

The increasing penetration of wind energy into national electricity markets has increased the demand for accurate surface layer wind forecasts. There has recently been a focus on forecasting the wind at wind farm sites using both statistical models and numerical weather prediction (NWP) models. Recent advances in computing capacity and non-hydrostatic NWP models means that it is possible to nest mesoscale models down to Large Eddy Simulation (LES) scales over the spatial area of a typical wind farm. For example, the WRF model (Skamarock 2008) has been run at a resolution of 123 m over a wind farm site in complex terrain in Colorado (Liu et al. 2009). Although these modelling attempts indicate a great hope for applying such models for detailed wind forecasts over wind farms, one of the obvious challenges of running the model at this resolution is that while some boundary layer structures are expected to be modelled explicitly, boundary layer eddies into the inertial sub-range can only be partly captured. Therefore, the amount and nature of sub-grid-scale mixing that is required is uncertain. Analysis of Liu et al. (2009) modelling results in comparison to wind farm observations indicates that unrealistic wind speed fluctuations with a period of around 1 hour occasionally occurred during the two day modelling period. The problem was addressed by re-running the same modelling system with a) a modified diffusion constant and b) two-way nesting between the high resolution model and its parent domain. The model, which was run with horizontal grid spacing of 370 m, had dimensions of 505 grid points in the east-west direction and 490 points in the north-south direction. It received boundary conditions from a mesoscale model of resolution 1111 m. Both models had 37 levels in the vertical. The mesoscale model was run with a non-local-mixing planetary boundary layer scheme, while the 370 m model was run with no planetary boundary layer scheme. It was found that increasing the diffusion constant caused damping of the unrealistic fluctuations, but did not completely solve the problem. Using two-way nesting also mitigated the unrealistic fluctuations significantly. It can be concluded that for real case LES modelling of wind farm circulations, care should be taken to ensure the consistency between the mesoscale weather forcing and LES models to avoid exciting spurious noise along the forcing boundary. The development of algorithms that adequately model the sub-grid-scale mixing that cannot be resolved by LES models is an important area for further research. References Liu, Y. Y._W. Liu, W. Y.Y. Cheng, W. Wu, T. T. Warner and K. Parks, 2009: Simulating intra-farm wind variations with the WRF-RTFDDA-LES modeling system. 10th WRF Users' Workshop, Boulder, C, USA. June 23 - 26, 2009. Skamarock, W., J. Dudhia, D.O. Gill, D.M. Barker, M.G.Duda, X-Y. Huang, W. Wang and J.G. Powers, A Description of the Advanced Research WRF version 3, NCAR Technical Note TN-475+STR, NCAR, Boulder, Colorado, 2008.

Wind Prediction Accuracy for Air Traffic Management Decision Support Tools

NASA Technical Reports Server (NTRS)

Cole, Rod; Green, Steve; Jardin, Matt; Schwartz, Barry; Benjamin, Stan

2000-01-01

The performance of Air Traffic Management and flight deck decision support tools depends in large part on the accuracy of the supporting 4D trajectory predictions. This is particularly relevant to conflict prediction and active advisories for the resolution of conflicts and the conformance with of traffic-flow management flow-rate constraints (e.g., arrival metering / required time of arrival). Flight test results have indicated that wind prediction errors may represent the largest source of trajectory prediction error. The tests also discovered relatively large errors (e.g., greater than 20 knots), existing in pockets of space and time critical to ATM DST performance (one or more sectors, greater than 20 minutes), are inadequately represented by the classic RMS aggregate prediction-accuracy studies of the past. To facilitate the identification and reduction of DST-critical wind-prediction errors, NASA has lead a collaborative research and development activity with MIT Lincoln Laboratories and the Forecast Systems Lab of the National Oceanographic and Atmospheric Administration (NOAA). This activity, begun in 1996, has focussed on the development of key metrics for ATM DST performance, assessment of wind-prediction skill for state of the art systems, and development/validation of system enhancements to improve skill. A 13 month study was conducted for the Denver Center airspace in 1997. Two complementary wind-prediction systems were analyzed and compared to the forecast performance of the then standard 60 km Rapid Update Cycle - version 1 (RUC-1). One system, developed by NOAA, was the prototype 40-km RUC-2 that became operational at NCEP in 1999. RUC-2 introduced a faster cycle (1 hr vs. 3 hr) and improved mesoscale physics. The second system, Augmented Winds (AW), is a prototype en route wind application developed by MITLL based on the Integrated Terminal Wind System (ITWS). AW is run at a local facility (Center) level, and updates RUC predictions based on an optimal interpolation of the latest ACARS reports since the RUC run. This paper presents an overview of the study's results including the identification and use of new large mor wind-prediction accuracy metrics that are key to ATM DST performance.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Na, Ji Sung; Koo, Eunmo; Munoz-Esparza, Domingo

High-resolution large-eddy simulation of the flow over a large wind farm (64 wind turbines) is performed using the HIGRAD/FIRETEC-WindBlade model, which is a high-performance computing wind turbine–atmosphere interaction model that uses the Lagrangian actuator line method to represent rotating turbine blades. These high-resolution large-eddy simulation results are used to parameterize the thrust and power coefficients that contain information about turbine interference effects within the wind farm. Those coefficients are then incorporated into the WRF (Weather Research and Forecasting) model in order to evaluate interference effects in larger-scale models. In the high-resolution WindBlade wind farm simulation, insufficient distance between turbines createsmore » the interference between turbines, including significant vertical variations in momentum and turbulent intensity. The characteristics of the wake are further investigated by analyzing the distribution of the vorticity and turbulent intensity. Quadrant analysis in the turbine and post-turbine areas reveals that the ejection motion induced by the presence of the wind turbines is dominant compared to that in the other quadrants, indicating that the sweep motion is increased at the location where strong wake recovery occurs. Regional-scale WRF simulations reveal that although the turbulent mixing induced by the wind farm is partly diffused to the upper region, there is no significant change in the boundary layer depth. The velocity deficit does not appear to be very sensitive to the local distribution of turbine coefficients. However, differences of about 5% on parameterized turbulent kinetic energy were found depending on the turbine coefficient distribution. Furthermore, turbine coefficients that consider interference in the wind farm should be used in wind farm parameterization for larger-scale models to better describe sub-grid scale turbulent processes.« less

Centrifugally driven winds from protostellar accretion discs - I. Formulation and initial results

NASA Astrophysics Data System (ADS)

Nolan, C. A.; Salmeron, R.; Federrath, C.; Bicknell, G. V.; Sutherland, R. S.

2017-10-01

Protostellar discs play an important role in star formation, acting as the primary mass reservoir for accretion on to young stars and regulating the extent to which angular momentum and gas is released back into stellar nurseries through the launching of powerful disc winds. In this study, we explore how disc structure relates to the properties of the wind-launching region, mapping out the regions of protostellar discs where wind launching could be viable. We combine a series of 1.5D semi-analytic, steady-state, vertical disc-wind solutions into a radially extended 1+1.5D model, incorporating all three diffusion mechanisms (Ohm, Hall and ambipolar). We observe that the majority of mass outflow via disc winds occurs over a radial width of a fraction of an astronomical unit, with outflow rates attenuating rapidly on either side. We also find that the mass accretion rate, magnetic field strength and surface density profile each have significant effects on both the location of the wind-launching region and the ejection/accretion ratio \\dot{M}_out/\\dot{M}_in. Increasing either the accretion rate or the magnetic field strength corresponds to a shift of the wind-launching region to smaller radii and a decrease in \\dot{M}_out/\\dot{M}_in, while increasing the surface density corresponds to launching regions at larger radii with increased \\dot{M}_out/\\dot{M}_in. Finally, we discover a class of disc winds containing an ineffective launching configuration at intermediate radii, leading to two radially separated regions of wind launching and diminished \\dot{M}_out/\\dot{M}_in. We find that the wind locations and ejection/accretion ratio are consistent with current observational and theoretical estimates.

Evaluation of the WRF-Urban Modeling System Coupled to Noah and Noah-MP Land Surface Models Over a Semiarid Urban Environment

NASA Astrophysics Data System (ADS)

Salamanca, Francisco; Zhang, Yizhou; Barlage, Michael; Chen, Fei; Mahalov, Alex; Miao, Shiguang

2018-03-01

We have augmented the existing capabilities of the integrated Weather Research and Forecasting (WRF)-urban modeling system by coupling three urban canopy models (UCMs) available in the WRF model with the new community Noah with multiparameterization options (Noah-MP) land surface model (LSM). The WRF-urban modeling system's performance has been evaluated by conducting six numerical experiments at high spatial resolution (1 km horizontal grid spacing) during a 15 day clear-sky summertime period for a semiarid urban environment. To assess the relative importance of representing urban surfaces, three different urban parameterizations are used with the Noah and Noah-MP LSMs, respectively, over the two major cities of Arizona: Phoenix and Tucson metropolitan areas. Our results demonstrate that Noah-MP reproduces somewhat better than Noah the daily evolution of surface skin temperature and near-surface air temperature (especially nighttime temperature) and wind speed. Concerning the urban areas, bulk urban parameterization overestimates nighttime 2 m air temperature compared to the single-layer and multilayer UCMs that reproduce more accurately the daily evolution of near-surface air temperature. Regarding near-surface wind speed, only the multilayer UCM was able to reproduce realistically the daily evolution of wind speed, although maximum winds were slightly overestimated, while both the single-layer and bulk urban parameterizations overestimated wind speed considerably. Based on these results, this paper demonstrates that the new community Noah-MP LSM coupled to an UCM is a promising physics-based predictive modeling tool for urban applications.

Wind driven vertical transport in a vegetated, wetland water column with air-water gas exchange

NASA Astrophysics Data System (ADS)

Poindexter, C.; Variano, E. A.

2010-12-01

Flow around arrays of cylinders at low and intermediate Reynolds numbers has been studied numerically, analytically and experimentally. Early results demonstrated that at flow around randomly oriented cylinders exhibits reduced turbulent length scales and reduced diffusivity when compared to similarly forced, unimpeded flows (Nepf 1999). While horizontal dispersion in flows through cylinder arrays has received considerable research attention, the case of vertical dispersion of reactive constituents has not. This case is relevant to the vertical transfer of dissolved gases in wetlands with emergent vegetation. We present results showing that the presence of vegetation can significantly enhance vertical transport, including gas transfer across the air-water interface. Specifically, we study a wind-sheared air-water interface in which randomly arrayed cylinders represent emergent vegetation. Wind is one of several processes that may govern physical dispersion of dissolved gases in wetlands. Wind represents the dominant force for gas transfer across the air-water interface in the ocean. Empirical relationships between wind and the gas transfer coefficient, k, have been used to estimate spatial variability of CO2 exchange across the worlds’ oceans. Because wetlands with emergent vegetation are different from oceans, different model of wind effects is needed. We investigated the vertical transport of dissolved oxygen in a scaled wetland model built inside a laboratory tank equipped with an open-ended wind tunnel. Plastic tubing immersed in water to a depth of approximately 40 cm represented emergent vegetation of cylindrical form such as hard-stem bulrush (Schoenoplectus acutus). After partially removing the oxygen from the tank water via reaction with sodium sulfite, we used an optical probe to measure dissolved oxygen at mid-depth as the tank water re-equilibrated with the air above. We used dissolved oxygen time-series for a range of mean wind speeds to estimate the gas transfer coefficient, k, for both a vegetated condition and a control condition (no cylinders). The presence of cylinders in the tank substantially increased the rate of the gas transfer. For the highest wind speed, the gas transfer coefficient was several times higher when cylinders were present compared to when they were not. The gas transfer coefficient for the vegetated condition also proved sensitive to wind speed, increasing markedly with increasing mean wind speeds. Profiles of dissolved oxygen revealed well-mixed conditions in the bulk water column following prolonged air-flow above the water surface, suggesting application of the thin-film model is appropriate. The enhanced gas exchange observed might be explained by increased turbulent kinetic energy within the water column and the anisotropy of the cylinder array, which constrains horizontal motions more than vertical motions. Improved understanding of gas exchange in vegetated water columns may be of particularly use to investigations of carbon fluxes and soil accretion in wetlands. Reference: Nepf, H. (1999), Drag, turbulence, and diffusion in flow through emergent vegetation, Water Resour. Res., 35(2), 479-489.

Highlights of theoretical progress related to the International Magnetospheric Study

NASA Technical Reports Server (NTRS)

Hill, T. W.

1982-01-01

U.S. theoretical research efforts have addressed three areas within the International Magnetospheric Study. The first, solar wind/magnetosphere interaction, is presently concerned with the suggestion that magnetic merging may predominantly occur near the polar cusps rather than near the subsolar point. Mechanisms have been proposed for noncollisional diffusion of solar wind plasma across the closed magnetopause entailed by such a phenomenon. The second area considers the importance to magnetotail dynamics of a continuous source of solar wind plasma, and of sporadic plasma loss associated with an unsteady convection cycle. In the third area, the electrodynamic magnetosphere/ionosphere interaction, an advanced state has been reached in the understanding of the relevant physics, with respect both to coupling in the subauroral region and the large scale structure of auroral zone electric fields parallel, and perpendicular to, the magnetic field.

The influence of geometry and draught shields on the performance of passive samplers.

PubMed

Hofschreuder, P; van der Meulen, W; Heeres, P; Slanina, S

1999-04-01

Passive samplers provide an excellent opportunity to perform indicative measurements or establish a dense network of measuring sites. A drawback compared with conventional active measuring methods is the larger spread of results. This variation can, to a large extent, be attributed to the influence of temperature, sampler geometry and wind on sampling results. A proper design of sampler geometry and optimum choice of draught shield can reduce the influence of wind velocity on a badge type sampler to less than 10%. Wire mesh screens prove to be inadequate in damping turbulence. Filters give good results. Attention should be paid to the size and isolation value of the walls of the sampler to prevent thermal updrafts occurring within the sampler. Tube type samplers are less influenced by wind, provided that turbulence is prevented from influencing diffusion within the sampler.

Energy balance constraints on gravity wave induced eddy diffusion in the mesosphere and lower thermosphere

NASA Technical Reports Server (NTRS)

Strobel, D. F.; Apruzese, J. P.; Schoeberl, M. R.

1985-01-01

The constraints on turbulence improved by the mesospheric heat budget are reexamined, and the sufficiency of the theoretical evidence to support the hypothesis that the eddy Prandtl number is greater than one in the mesosphere is considered. The mesopause thermal structure is calculated with turbulent diffusion coefficients commonly used in chemical models and deduced from mean zonal wind deceleration. It is shown that extreme mesopause temperatures of less than 100 K are produced by the large net cooling. The results demonstrate the importance of the Prandtl number for mesospheric turbulence.

Auroral Acceleration, Solar Wind Driving, and Substorm Triggering (Invited)

NASA Astrophysics Data System (ADS)

Newell, P. T.; Liou, K.

2010-12-01

We use a data base of 4861 substorms identified by global UV images to investigate the substorm cycle dependence of various types of aurora, and to obtain new results on substorm triggering by external driving. Although all types of aurora increase at substorm onset, broadband (Alfvénic) aurora shows a particular association with substorms, and, especially, substorm onset. While diffuse electron and monoenergetic auroral precipitating power rises by 79% and 90% respectively following an onset, broadband aurora rises by 182%. In the first 10-15 minutes following onset, the power associated with Alfvénic acceleration is comparable to monoenergetic acceleration (also called “inverted-V” events). In general, this is not the case prior to onset, or indeed, during recovery. The rise time of the electron diffuse aurora following onset is much slower, about 50 minutes, and thus presumably extends into recovery. We also re-investigate the issue of solar wind triggering of substorms by considering not just changes in the solar wind prior to onset, but how the pattern of changes differs from random and comparable epochs. We verify that a preonset reduction of solar wind driving (“northward turning” in the simplest case of IMF Bz) holds for the superposed epoch mean of the ensemble. Moreover, this reduction is not the result of a small number of substorms with large changes. The reduction starts about 20 min prior to substorm onset, which, although a longer delay than previously suggested, is appropriate given the various propagation time delays involved. Next, we compare the IMF to random solar wind conditions. Not surprisingly, solar wind driving prior to onset averages somewhat higher than random. Although about a quarter of substorms occur for steady northward IMF conditions, more general coupling functions such as the Kan-Lee electric field, the Borovosky function, or our dΦMP/dt, show very few substorms occur following weak dayside merging. We assembled a data base of solar wind times with slightly elevated conditions, chosen to resemble the integrated driving typical before substorm onsets, but otherwise randomly occuring. We looked at how the IMF subsequently changed after these random elevations, compared to the changes preceding substorms. It turns out that mere reversion to the mean leads to a “northward turning” after the imposed selection criterion end. Thus (slightly generalizing the view of Morley and Freeman), substorms require solar wind driving which produces dayside merging, but external triggering is probably insignificant.

Experimental evaluation of two turning vane designs for fan drive corner of 0.1-scale model of NASA Lewis Research Center's proposed altitude wind tunnel

NASA Technical Reports Server (NTRS)

Boldman, Donald R.; Moore, Royce D.; Shyne, Rickey J.

1987-01-01

Two turning vane designs were experimentally evaluated for corner 2 of a 0.1 scale model of the NASA Lewis Research Center's proposed Altitude Wind Tunnel (AWT). Corner 2 contained a simulated shaft fairing for a fan drive system to be located downstream of the corner. The corner was tested with a bellmouth inlet followed by a 0.1 scale model of the crossleg diffuser designed to connect corners 1 and 2 of the AWT. Vane A was a controlled-diffusion airfoil shape; vane B was a circular-arc airfoil shape. The A vanes were tested in several arrangements which included the resetting of the vane angle by -5 degrees or the removal of the outer vane. The lowest total pressure loss for vane A configuration was obtained at the negative reset angle. The loss coefficient increased slightly with the Mach number, ranging from 0.165 to 0.175 with a loss coefficient of 0.170 at the inlet design Mach number of 0.24. Removal of the outer vane did not alter the loss. Vane B loss coefficients were essentially the same as those for the reset vane A configurations. The crossleg diffuser loss coefficient was 0.018 at the inlet design Mach number of 0.33.

Research Needs for Wind Resource Characterization

NASA Astrophysics Data System (ADS)

Schreck, S. J.; Lundquist, J. K.; Shaw, W. J.

2008-12-01

Currently, wind energy provides about 1 percent of U.S. electricity generation. A recent analysis by DOE, NREL, and AWEA showed the feasibility of expanding U.S. wind energy capacity to 20 percent, comprising approximately 300 gigawatts. Though not a prediction of the future, this represents a plausible scenario for U.S. wind energy. To exploit these opportunities, a workshop on Research Needs for Wind Resource Characterization was held during January 2008. This event was organized on behalf of two DOE organizations; the Office of Biological and Environmental Research and the Office of Energy Efficiency and Renewable Energy. Over 120 atmospheric science and wind energy researchers attended the workshop from industry, academia, and federal laboratories in North America and Europe. Attendees identified problems that could impede achieving the 20 percent wind scenario and formulated research recommendations to attack these problems. Findings were structured into four focus areas: 1) Turbine Dynamics, 2) Micrositing and Array Effects, 3) Mesoscale Processes, and 4) Climate Effects. In the Turbine Dynamics area, detailed characterizations of inflows and turbine flow fields were deemed crucial to attaining accuracy levels in aerodynamics loads required for future designs. To address the complexities inherent in this area, an incremental approach involving hierarchical computational modeling and detailed measurements was recommended. Also recommended was work to model extreme and anomalous atmospheric inflow events and aerostructural responses of turbines to these events. The Micrositing and Array Effects area considered improved wake models important for large, multiple row wind plants. Planetary boundary layer research was deemed necessary to accurately determine inflow characteristics in the presence of atmospheric stability effects and complex surface characteristics. Finally, a need was identified to acquire and exploit large wind inflow data sets, covering heights to 200 meters and encompassing spatial and temporal resolution ranges unique to wind energy. The Mesoscale Processes area deemed improved understanding of mesoscale and local flows crucial to providing enhanced model outputs for wind energy production forecasts and wind plant siting. Modeling approaches need to be developed to resolve spatial scales in the 100 to 1000 meter range, a notable gap in current capabilities. Validation of these models will require new instruments and observational strategies, including augmented analyses of existing measurements. In the Climate Effects area, research was recommended to understand historical trends in wind resource variability. This was considered a prerequisite for improved predictions of future wind climate and resources, which would enable reliable wind resource estimation for future planning. Participants also considered it important to characterize interactions between wind plants and climates through modeling and observations that suitably emphasize atmospheric boundary layer dynamics. High-penetration wind energy deployment represents a crucial and attainable U.S. strategic objective. Achieving the 20 percent wind scenario will require an unprecedented ability for characterizing large wind turbines arrayed in gigawatt wind plants and extracting elevated energy levels from the atmosphere. DOE national laboratories, with industry and academia, represents a formidable capability for attaining these objectives.

A potential-energy surface study of the 2A1 and low-lying dissociative states of the methoxy radical

NASA Technical Reports Server (NTRS)

Jackels, C. F.

1985-01-01

Accurate, ab initio quantum chemical techniques are applied in the present study of low lying bound and dissociative states of the methoxy radical at C3nu conformations, using a double zeta quality basis set that is augmented with polarization and diffuse functions. Excitation energy estimates are obtained for vertical excitation, vertical deexcitation, and system origin. The rate of methoxy photolysis is estimated to be too small to warrant its inclusion in atmospheric models.

Scientists Find X Rays from Stellar Winds That May Play Significant Role in Galactic Evolution

NASA Astrophysics Data System (ADS)

2001-09-01

Colorful star-forming regions that have captivated stargazers since the advent of the telescope 400 years ago contain gas thousands of times more energetic than previously recognized, powered by colliding stellar winds. This multimillion-degree gas radiated as X rays is one of the long-sought sources of energy and elements in the Milky Way galaxy's interstellar medium. A team led by Leisa Townsley, a senior research associate in astronomy and astrophysics at Penn State University, uncovered this wind phenomenon in the Rosette Nebula, a stellar nursery. With the Chandra X-ray Observatory, the team found that the most massive stars in the nebula produce winds that slam into each other, create violent shocks, and infuse the region with 6-million-degree gas. The findings are presented in Washington, D.C., today at a conference entitled "Two Years of Science with Chandra." "A ghostly glow of diffuse X-ray emission pervades the Rosette Nebula and perhaps many other similar star-forming regions throughout the Galaxy," said Townsley. "We now have a new view of the engine lighting the beautiful Rosette Nebula and new evidence for how the interstellar medium may be energized." Townsley and her colleagues created a striking X-ray panorama of the Rosette Molecular Cloud from four images with Chandra's Advanced CCD Imaging Spectrometer. This is a swath of the sky nearly 100 light years across sprayed with hundreds of X-ray-emitting young stars. In one corner of the Rosette Molecular Cloud lies the Rosette Nebula, called an "H II region" because the hydrogen gas there has been stripped of its electrons due to the strong ultraviolet radiation from its young stars. This region, about 5,000 light years away in the constellation Monoceros, the Unicorn, has long been a favorite among amateur astronomers. The wispy, colorful display is visible with small telescopes. The Chandra survey reveals, for the first time, 6-million-degree gas at the center of the Rosette Nebula, occupying a volume of about 3,000 cubic light years. Fueling the fury are a handful of massive type-O and type-B stars at the core of the nebula, the most massive members of a populous "OB association" that also includes hundreds of lower- mass stars. Rosette Nebula Optical/X-ray Composite Press Image and Caption "Until this observation, no one really knew where the energy of the powerful OB stellar winds goes," said Eric Feigelson, professor of astronomy and astrophysics at Penn State and a co-investigator in the study. "Theorists have speculated about this for decades, and we now see with Chandra the heat from the winds slamming into the cooler gas." Earlier X-ray telescopes did not have the resolution to differentiate between point sources and diffuse emission in the Rosette Nebula to the extent that Chandra has. Chandra imaged over 300 individual young stars in the Rosette Nebula, plus hundreds more in the Rosette Molecular Cloud. "We were able to identify the faint, diffuse radiation by subtracting out these point sources and looking at what was left over," explains team member Patrick Broos, a research assistant in astronomy and astrophysics at Penn State. The diffuse emission is not likely to be from supernova remnants left over from exploded stars because the Rosette Nebula is too young to have produced these, according to You- Hua Chu, of the University of Illinois at Urbana-Champaign. Rather, the diffuse emission must be related to the way the stellar winds from OB associations dissipate their energy. Understanding the detailed processes involved will rely on front-line research done in the laboratory on energy transport in very hot gases, according to Thierry Montmerle, of the Centre d'Etudes de Saclay in France. Chu and Montmerle have joined the research team to help interpret the Chandra results. The observations were made with Chandra's Advanced CCD Imaging Spectrometer, which was conceived and developed for NASA by Penn State and Massachusetts Institute of Technology under the leadership of Gordon Garmire, the Evan Pugh Professor of Astronomy and Astrophysics at Penn State.

The highly ionized, high-velocity gas in NGC 6231

NASA Astrophysics Data System (ADS)

Massa, Derck

2017-02-01

It is well known that clusters of massive stars are influenced by the presence of strong winds, that they are sources of diffuse X-rays from shocked gas, and that this gas can be vented into the surrounding region or the halo through the champagne effect. However, the details of how these different environments interact and evolve are far from complete. This paper attributes the broad C IVλλ1500 absorption features (extending to -1900 km s-1) that are seen in the spectra of main sequence B stars in NGC 6231 to gas in the cluster environment and not the B stars themselves. It is shown that the presence of a WC star, WR 79, in the cluster makes this gas detectable because its wind enriches the cluster gas with carbon. Given the available data, it is not clear whether the absorbing gas is simply the far wind of WR 79 or a collective cluster wind enriched by carbon from the wind of WR 79. If it is simply due to the wind, then this wind must flow, unimpeded for more than 2 pc, suggesting that the inner region of the cluster is nearly devoid of obstructing material. If it is actually a collective wind from the cluster, then we could be witnessing an important stage of galactic feedback. In either case, the observations provide a unique and significant piece to the puzzle of how massive, open clusters evolve.

AGN Obscuration Through Dusty Infrared Dominated Flows. 1; Radiation-Hydrodynamics Solution for the Wind

NASA Technical Reports Server (NTRS)

Dorodnitsyn, A.; Bisnovatyi-Kogan. G. S.; Kallman, T.

2011-01-01

We construct a radiation-hydrodynamics model for the obscuring toroidal structure in active galactic nuclei. In this model the obscuration is produced at parsec scale by a dense, dusty wind which is supported by infrared radiation pressure on dust grains. To find the distribution of radiation pressure, we numerically solve the 2D radiation transfer problem in a flux limited diffusion approximation. We iteratively couple the solution with calculations of stationary 1D models for the wind, and obtain the z-component of the velocity. Our results demonstrate that for AGN luminosities greater than 0.1 L(sub edd) external illumination can support a geometrically thick obscuration via outflows driven by infrared radiation pressure. The terminal velocity of marginally Compton-thin models (0.2 < tau(sub T) < 0.6), is comparable to or greater than the escape velocity. In Compton thick models the maximum value of the vertical component of the velocity is lower than the escape velocity, suggesting that a significant part of our torus is in the form of failed wind. The results demonstrate that obscuration via normal or failed infrared-driven winds is a viable option for the AGN torus problem and AGN unification models. Such winds can also provide an important channel for AGN feedback.

Modelling the impact of wind stress and river discharge on Danshuei River plume

USGS Publications Warehouse

Liu, W.-C.; Chen, W.-B.; Cheng, R.T.; Hsu, M.-H.

2008-01-01

A three-dimensional, time-dependent, baroclinic, hydrodynamic and salinity model, UnTRIM, was performed and applied to the Danshuei River estuarine system and adjacent coastal sea in northern Taiwan. The model forcing functions consist of tidal elevations along the open boundaries and freshwater inflows from the main stream and major tributaries in the Danshuei River estuarine system. The bottom friction coefficient was adjusted to achieve model calibration and verification in model simulations of barotropic and baroclinic flows. The turbulent diffusivities were ascertained through comparison of simulated salinity time series with observations. The model simulation results are in qualitative agreement with the available field data. The validated model was then used to investigate the influence of wind stress and freshwater discharge on Dasnhuei River plume. As the absence of wind stress, the anticyclonic circulation is prevailed along the north to west coast. The model results reveal when winds are downwelling-favorable, the surface low-salinity waters are flushed out and move to southwest coast. Conversely, large amounts of low-salinity water flushed out the Danshuei River mouth during upwelling-favorable winds, as the buoyancy-driven circulation is reversed. Wind stress and freshwater discharge are shown to control the plume structure. ?? 2007 Elsevier Inc. All rights reserved.

Active Galactic Nucleus Obscuration from Winds: From Dusty Infrared-Driven to Warm and X-Ray Photoionized

NASA Technical Reports Server (NTRS)

Dorodnitsyn, Anton V.; Kallman, Timothy R.

2012-01-01

We present calculations of active galactic nucleus winds at approx.parsec scales along with the associated obscuration. We take into account the pressure of infrared radiation on dust grains and the interaction of X-rays from a central black hole with hot and cold plasma. Infrared radiation (IR) is incorporated in radiation-hydrodynamic simulations adopting the flux-limited diffusion approximation. We find that in the range of X-ray luminosities L = 0.05-0.6 L(sub Edd), the Compton-thick part of the flow (aka torus) has an opening angle of approximately 72deg - 75deg regardless of the luminosity. At L > or approx. 0.1, the outflowing dusty wind provides the obscuration with IR pressure playing a major role. The global flow consists of two phases: the cold flow at inclinations (theta) > or approx.70deg and a hot, ionized wind of lower density at lower inclinations. The dynamical pressure of the hot wind is important in shaping the denser IR-supported flow. At luminosities < or = 0.1 L(sub Edd) episodes of outflow are followed by extended periods when the wind switches to slow accretion. Key words: acceleration of particles . galaxies: active . hydrodynamics . methods: numerical Online-only material: color figures

Integration of Wind Turbines with Compressed Air Energy Storage

NASA Astrophysics Data System (ADS)

Arsie, I.; Marano, V.; Rizzo, G.; Moran, M.

2009-08-01

Some of the major limitations of renewable energy sources are represented by their low power density and intermittent nature, largely depending upon local site and unpredictable weather conditions. These problems concur to increase the unit costs of wind power, so limiting their diffusion. By coupling storage systems with a wind farm, some of the major limitations of wind power, such as a low power density and an unpredictable nature, can be overcome. After an overview on storage systems, the Compressed Air Energy Storage (CAES) is analyzed, and the state of art on such systems is discussed. A Matlab/Simulink model of a hybrid power plant consisting of a wind farm coupled with CAES is then presented. The model has been successfully validated starting from the operating data of the McIntosh CAES Plant in Alabama. Time-series neural network-based wind speed forecasting are employed to determine the optimal daily operation strategy for the storage system. A detailed economic analysis has been carried out: investment and maintenance costs are estimated based on literature data, while operational costs and revenues are calculated according to energy market prices. As shown in the paper, the knowledge of the expected available energy is a key factor to optimize the management strategies of the proposed hybrid power plant, allowing to obtain environmental and economic benefits.

Performance Characteristics of Plane-Wall Two-Dimensional Diffusers

NASA Technical Reports Server (NTRS)

Reid, Elliott G

1953-01-01

Experiments have been made at Stanford University to determine the performance characteristics of plane-wall, two-dimensional diffusers which were so proportioned as to insure reasonable approximation of two-dimensional flow. All of the diffusers had identical entrance cross sections and discharged directly into a large plenum chamber; the test program included wide variations of divergence angle and length. During all tests a dynamic pressure of 60 pounds per square foOt was maintained at the diffuser entrance and the boundary layer there was thin and fully turbulent. The most interesting flow characteristics observed were the occasional appearance of steady, unseparated, asymmetric flow - which was correlated with the boundary-layer coalescence - and the rapid deterioration of flow steadiness - which occurred as soon as the divergence angle for maximum static pressure recovery was exceeded. Pressure efficiency was found to be controlled almost exclusively by divergence angle, whereas static pressure recovery was markedly influenced by area ratio (or length) as well as divergence angle. Volumetric efficiency. diminished as area ratio increased, and at a greater rate with small lengths than with large ones. Large values of the static-pressure-recovery coefficient were attained only with long diffusers of large area ratio; under these conditions pressure efficiency was high and. volumetric efficiency low. Auxiliary tests with asymmetric diffusers demonstrated that longitudinal pressure gradient, rather than wall divergence angle, controlled flow separation. Others showed that the addition of even a short exit duct of uniform section augmented pressure recovery. Finally, it was found that the installation of a thin, central, longitudinal partition suppressed flow separation in short diffusers and thereby improved pressure recovery

DIFFUSION IN THE VICINITY OF STANDARD-DESIGN NUCLEAR POWER PLANTS--II: WIND-TUNNEL EVALUATION OF BUILDING-WAKE CHARACTERISTICS

EPA Science Inventory

Laboratory experiments were conducted to simulate radiopollutant effluents released to the atmosphere from two standard-design nuclear power plants. The main objective of the study was to compare the dispersion in the wakes of the plants with that in a simulated atmospheric bound...

Thermal Infrared Signatures and Heat Fluxes of Sea Foam

DTIC Science & Technology

2015-01-13

4 air flow 0.5 m 0.5 m MWIR LWIR FTIR Pitot tube and Temperature air diffuser 1 m EO foam IR H20 vapor analyzer Heat...verify this, we measured velocity profiles with a pitot tube over 5 water and foam surfaces spanning our range of tested wind speeds. The profiles (not

Accounting for magnetic diffusion in core flow inversions from geomagnetic secular variation

NASA Astrophysics Data System (ADS)

Amit, Hagay; Christensen, Ulrich R.

2008-12-01

We use numerical dynamos to investigate the possible role of magnetic diffusion at the top of the core. We find that the contribution of radial magnetic diffusion to the secular variation is correlated with that of tangential magnetic diffusion for a wide range of control parameters. The correlation between the two diffusive terms is interpreted in terms of the variation in the strength of poloidal flow along a columnar flow tube. The amplitude ratio of the two diffusive terms is used to estimate the probable contribution of radial magnetic diffusion to the secular variation at Earth-like conditions. We then apply a model where radial magnetic diffusion is proportional to tangential diffusion to core flow inversions of geomagnetic secular variation data. We find that including magnetic diffusion does not change dramatically the global flow but some significant local variations appear. In the non frozen-flux core flow models (termed `diffusive'), the hemispherical dichotomy between the active Atlantic and quiet Pacific is weaker, a cyclonic vortex below North America emerges and the vortex below Asia is stronger. Our results have several important geophysical implications. First, our diffusive flow models contain some flow activity at low latitudes in the Pacific, suggesting a local balance between magnetic field advection and diffusion in that region. Second, the cyclone below North America in our diffusive flows reconciles the difference between mantle-driven thermal wind predictions and frozen-flux core flow models, and is consistent with the prominent intense magnetic flux patch below North America in geomagnetic field models. Finally, we hypothesize that magnetic diffusion near the core surface plays a larger role in the geomagnetic secular variation than usually assumed.

Rossby wave activity in a two-dimensional model - Closure for wave driving and meridional eddy diffusivity

NASA Technical Reports Server (NTRS)

Hitchman, Matthew H.; Brasseur, Guy

1988-01-01

A parameterization of the effects of Rossby waves in the middle atmosphere is proposed for use in two-dimensional models. By adding an equation for conservation of Rossby wave activity, closure is obtained for the meridional eddy fluxes and body force due to Rossby waves. Rossby wave activity is produced in a climatological fashion at the tropopause, is advected by a group velocity which is determined solely by model zonal winds, and is absorbed where it converges. Absorption of Rossby wave activity causes both an easterly torque and an irreversible mixing of potential vorticity, represented by the meridional eddy diffusivity, K(yy). The distribution of Rossby wave driving determines the distribution of K(yy), which is applied to all of the chemical constituents. This provides a self-consistent coupling of the wave activity with the winds, tracer distributions and the radiative field. Typical winter stratospheric values for K(yy) of 2 million sq m/sec are obtained. Poleward tracer advection is enhanced and meridional tracer gradients are reduced where Rossby wave activity is absorbed in the model.

Dissecting Diffuse X-ray Emission in 30 Doradus with T-ReX

NASA Astrophysics Data System (ADS)

Townsley, Leisa K.; Broos, Patrick

2017-08-01

30 Doradus (the Tarantula Nebula) offers us a microscope on starburst astrophysics, having endured 25 Myrs of the birth and death of the most massive stars known. Across 30 Dor's 250-pc extent, stellar winds and supernovae have carved its ISM into an amazing display of arcs, pillars, and bubbles. For over 40 years, we have also known that 30 Dor is a bright X-ray emitter, so its familiar stars and cold ISM structures suffer irradiation by multi-million-degree plasmas. The 2-Ms Chandra X-ray Visionary Project ``The Tarantula -- Revealed by X-rays'' (T-ReX) exploits Chandra's fine spatial resolution and the ACIS-I field of view to study ISM interfaces on 1--10 pc scales across the entire 30 Dor complex. Here we give preliminary results from ongoing analyses of these data, focusing on the diffuse X-ray emission. Massive star winds and cavity supernovae over the millenia have contributed to a broad mix of X-ray-emitting plasmas and absorbing columns, showing that 30 Dor's hot ISM is just as complex and confusing as that seen at colder temperatures.

Fast diffusion kurtosis imaging (DKI) with Inherent COrrelation-based Normalization (ICON) enhances automatic segmentation of heterogeneous diffusion MRI lesion in acute stroke.

PubMed

Zhou, Iris Yuwen; Guo, Yingkun; Igarashi, Takahiro; Wang, Yu; Mandeville, Emiri; Chan, Suk-Tak; Wen, Lingyi; Vangel, Mark; Lo, Eng H; Ji, Xunming; Sun, Phillip Zhe

2016-12-01

Diffusion kurtosis imaging (DKI) has been shown to augment diffusion-weighted imaging (DWI) for the definition of irreversible ischemic injury. However, the complexity of cerebral structure/composition makes the kurtosis map heterogeneous, limiting the specificity of kurtosis hyperintensity to acute ischemia. We propose an Inherent COrrelation-based Normalization (ICON) analysis to suppress the intrinsic kurtosis heterogeneity for improved characterization of heterogeneous ischemic tissue injury. Fast DKI and relaxation measurements were performed on normal (n = 10) and stroke rats following middle cerebral artery occlusion (MCAO) (n = 20). We evaluated the correlations between mean kurtosis (MK), mean diffusivity (MD) and fractional anisotropy (FA) derived from the fast DKI sequence and relaxation rates R 1 and R 2 , and found a highly significant correlation between MK and R 1 (p < 0.001). We showed that ICON analysis suppressed the intrinsic kurtosis heterogeneity in normal cerebral tissue, enabling automated tissue segmentation in an animal stroke model. We found significantly different kurtosis and diffusivity lesion volumes: 147 ± 59 and 180 ± 66 mm 3 , respectively (p = 0.003, paired t-test). The ratio of kurtosis to diffusivity lesion volume was 84% ± 19% (p < 0.001, one-sample t-test). We found that relaxation-normalized MK (RNMK), but not MD, values were significantly different between kurtosis and diffusivity lesions (p < 0.001, analysis of variance). Our study showed that fast DKI with ICON analysis provides a promising means of demarcation of heterogeneous DWI stroke lesions. Copyright © 2016 John Wiley & Sons, Ltd.

The Metal Content of Dwarf Starburst Winds: Results from Chandra Observations of NGC 1569

NASA Astrophysics Data System (ADS)

Martin, Crystal L.; Kobulnicky, Henry A.; Heckman, Timothy M.

2002-08-01

We present deep Chandra spectral imaging of the dwarf starburst galaxy NGC 1569. The unprecedented spatial resolution allows us to spatially identify the components of the integrated X-ray spectrum. Fitted spectral models require an intrinsic absorption component and higher metal abundances than previous studies indicated. Our results provide the first direct evidence for metal-enriched winds from dwarf starburst galaxies. We identify 14 X-ray point sources in NGC 1569. Most have properties consistent with those of high-mass X-ray binaries, but one is a steep-spectrum radio source that is probably a supernova remnant. The X-ray luminosity of NGC 1569 is dominated by diffuse, thermal emission from the disk (0.7 keV) and bipolar halo (0.3 keV). Photoelectric absorption from the inclined H I disk hardens the X-ray spectrum on the northern side of the disk relative to the southern side. Requiring the fitted absorption column to match the H I column measured at 21 cm implies that the metallicity of the H I disk is significantly less than solar but greater than 0.1 Zsolar. Hence, much of the H I is enriched to levels comparable to the metallicity of the H II regions [O/H=0.2(O/H)solar]. The X-ray color variations in the halo are inconsistent with a free-streaming wind and probably reveal the location of shocks created by the interaction of the wind with a gaseous halo. The X-ray spectrum of the diffuse gas presents strong emission lines from α-process elements. Fitted models require α-element abundances greater than 0.25 Zα,solar and ratios of α-elements to iron 2-4 times higher than the solar ratio. The best fit to the spectrum is obtained with solar mass fractions for the α-elements, 1.0 Zα,solar, but a degeneracy between the metallicity and the spectral normalization prevents us from deriving an upper limit on the wind metallicity from the X-ray spectrum alone. We argue, however, that abundances larger than 2.0 Zα,solar pose awkward implications for the dynamical evolution of the wind based on our knowledge of the starburst properties. For consistency with our best-fitting abundances, the mass of interstellar gas entrained in the wind must be about 9 times the mass of stellar ejecta in the wind. Most of the oxygen carried by the wind comes from the stellar ejecta rather than entrained interstellar gas. The estimated mass of oxygen in the hot wind, 34,000 Msolar, is similar to the oxygen yield of the current starburst. Apparently the wind carries nearly all the metals ejected by the starburst. These metals appear destined to contribute to the enrichment of the intergalactic medium. Much of the nucleosynthesis in NGC 1569 must have occurred during less violent periods of star formation, however, because our measurements imply that the neutral gas disk holds at least 5 times more oxygen than wind. Based on observations obtained with the Chandra X-Ray Observatory.

DXL: A Sounding Rocket Mission for the Study of Solar Wind Charge Exchange and Local Hot Bubble X-Ray Emission

NASA Technical Reports Server (NTRS)

Galeazzi, M.; Prasai, K.; Uprety, Y.; Chiao, M.; Collier, M. R.; Koutroumpa, D.; Porter, F. S.; Snowden, S.; Cravens, T.; Robertson, I.;

Analytical modeling of circuit aerodynamics in the new NASA Lewis wind tunnel

NASA Technical Reports Server (NTRS)

Towne, C. E.; Povinelli, L. A.; Kunik, W. G.; Muramoto, K. K.; Hughes, C. E.; Levy, R.

1985-01-01

Rehabilitation and extention of the capability of the altitude wind tunnel (AWT) was analyzed. The analytical modeling program involves the use of advanced axisymmetric and three dimensional viscous analyses to compute the flow through the various AWT components. Results for the analytical modeling of the high speed leg aerodynamics are presented; these include: an evaluation of the flow quality at the entrance to the test section, an investigation of the effects of test section bleed for different model blockages, and an examination of three dimensional effects in the diffuser due to reentry flow and due to the change in cross sectional shape of the exhaust scoop.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Emanuela Barzi et al.1

Nb{sub 3}Sn is the superconductor most used in the R and D of high field accelerator magnets by either the wind and react or the react and wind technique. In order to program the low temperature steps of the heat treatment, the growth kinetics of Cu-Sn intermetallics was investigated as a function of duration and temperature. The diffusion constants of {eta}, {var_epsilon} and {delta} phases between 150 and 550 C were evaluated using Cu-Sn model samples. Statistical and systematic errors were thoroughly evaluated for an accurate data analysis. Next the behavior of Internal Tin and Modified Jelly Roll Nb{sub 3}Snmore » composites was compared with the model predictions.« less

Diffuse reflectance of the ocean - The theory of its augmentation by chlorophyll a fluorescence at 685 nm

NASA Technical Reports Server (NTRS)

Gordon, H. R.

1979-01-01

The radiative transfer equation is modified to include the effect of fluorescent substances and solved in the quasi-single scattering approximation for a homogeneous ocean containing fluorescent particles with wavelength independent quantum efficiency and a Gaussian shaped emission line. The results are applied to the in vivo fluorescence of chlorophyll a (in phytoplankton) in the ocean to determine if the observed quantum efficiencies are large enough to explain the enhancement of the ocean's diffuse reflectance near 685 nm in chlorophyll rich waters without resorting to anomalous dispersion. The computations indicate that the required efficiencies are sufficiently low to account completely for the enhanced reflectance. The validity of the theory is further demonstrated by deriving values for the upwelling irradiance attenuation coefficient at 685 nm which are in close agreement with the observations.

ULF wave analysis and radial diffusion calculation using a global MHD model for the 17 March 2013 and 2015 storms

NASA Astrophysics Data System (ADS)

Li, Zhao; Hudson, Mary; Patel, Maulik; Wiltberger, Michael; Boyd, Alex; Turner, Drew

2017-07-01

The 17 March 2015 St. Patrick's Day Storm is the largest geomagnetic storm to date of Solar Cycle 24, with a Dst of -223 nT. The magnetopause moved inside geosynchronous orbit under high solar wind dynamic pressure and strong southward interplanetary magnetic field Bz causing loss; however, a subsequent drop in pressure allowed for rapid rebuilding of the radiation belts. The 17 March 2013 storm also shows similar effects on outer zone electrons: first, a rapid dropout due to inward motion of the magnetopause followed by rapid increase in flux above the prestorm level early in the recovery phase and a slow increase over the next 12 days. These phases can be seen in temporal evolution of the electron phase space density measured by the Energetic Particle, Composition, and Thermal Plasma Suite (ECT) instruments on Van Allen Probes. Using the Lyon-Fedder-Mobarry global MHD model driven by upstream solar wind measurements, we simulated both St. Patrick's Day 2013 and 2015 events, analyzing Lyon-Fedder-Mobarry electric and magnetic fields to calculate radial diffusion coefficients. These coefficients have been implemented in a radial diffusion code, using the measured electron phase space density following the local heating as the initial radial profile and outer boundary condition for subsequent temporal evolution over the next 12 days, beginning 18 March. Agreement with electron phase space density at 1000 MeV/G measured by the MagEIS component of the ECT instrument suite on Van Allen Probes was much improved using radial diffusion coefficients from the MHD simulations relative to coefficients parameterized by a global geomagnetic activity index.

Observational study on the concentration distributions of SO{sub 2} and NO{sub 2} in Dhaka, Bangladesh under severe air pollution condition in winter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azad, A.K.; Kitada, T.

1996-12-31

Dhaka is the capital and the biggest city of Bangladesh, and is expanding very rapidly. Emissions from heavy traffic and many small industries and commercial complexes, newly developed in and around the city, are polluting the air of Dhaka city. The air pollution is severe especially in winter due to adverse meteorological conditions such as low wind speed and dry, stably-stratified air, which restricts the mixing height to low levels and prevent dispersion of pollutants. But so far no study of air pollution of Dhaka city has been done. We have first measured SO{sub 2} and NO{sub 2} concentrations inmore » Dhaka city in a large scale and derived their spatial distributions over Dhaka. Molecular diffusion tubes, which do not require power sources and are produced at low cost, have been used to measure the concentration distributions of SO{sub 2} and NO{sub 2} at 64 sites in Dhaka city and its suburbs during the period of December-January of 1995-96. The diffusion tube samplers were calibrated using 6 automated air pollution monitoring stations in Aichi-prefecture, Japan. The calibration curve and the distribution of the concentration data acquired by automatic measurement instrument at each location showed that the error range of measurements with the molecular diffusion tube samplers was 2-27%. The samples were analyzed using ion-chromatography and spectrophotometer to determine the concentrations of SO{sub 2} and NO{sub 2} respectively. The contamination of unexposed tubes under field conditions was determined and the value of the blank test was subtracted from the measurements of the diffusion tube samplers. The effects of wind turbulence and temperature were reduced using polyflon filters.« less

Cell-centered high-order hyperbolic finite volume method for diffusion equation on unstructured grids

NASA Astrophysics Data System (ADS)

Lee, Euntaek; Ahn, Hyung Taek; Luo, Hong

2018-02-01

We apply a hyperbolic cell-centered finite volume method to solve a steady diffusion equation on unstructured meshes. This method, originally proposed by Nishikawa using a node-centered finite volume method, reformulates the elliptic nature of viscous fluxes into a set of augmented equations that makes the entire system hyperbolic. We introduce an efficient and accurate solution strategy for the cell-centered finite volume method. To obtain high-order accuracy for both solution and gradient variables, we use a successive order solution reconstruction: constant, linear, and quadratic (k-exact) reconstruction with an efficient reconstruction stencil, a so-called wrapping stencil. By the virtue of the cell-centered scheme, the source term evaluation was greatly simplified regardless of the solution order. For uniform schemes, we obtain the same order of accuracy, i.e., first, second, and third orders, for both the solution and its gradient variables. For hybrid schemes, recycling the gradient variable information for solution variable reconstruction makes one order of additional accuracy, i.e., second, third, and fourth orders, possible for the solution variable with less computational work than needed for uniform schemes. In general, the hyperbolic method can be an effective solution technique for diffusion problems, but instability is also observed for the discontinuous diffusion coefficient cases, which brings necessity for further investigation about the monotonicity preserving hyperbolic diffusion method.

Major Pathways to Electron Distribution Function Formation in Regions of Diffuse Aurora

NASA Technical Reports Server (NTRS)

Khazanov, George V.; Sibeck, David G.; Zesta, Eftyhia

2017-01-01

This paper discusses the major pathways of electron distribution function formation in the region of diffuse aurora. The diffuse aurora accounts for about of 75% of the auroral energy precipitating into the upper atmosphere, and its origin has been the subject of much discussion. We show that an earthward stream of precipitating electrons initially injected from the Earth's plasma sheet via wave-particle interactions degrades in the atmosphere toward lower energies and produces secondary electrons via impact ionization of the neutral atmosphere. These electrons of magnetospheric origin are then reflected back into the magnetosphere along closed dipolar magnetic field lines, leading to a series of reflections and consequent magnetospheric interactions that greatly augment the initially precipitating flux at the upper ionospheric boundary (700-800 km). To date this, systematic magnetosphere-ionosphere coupling element has not been included in auroral research models, and, as we demonstrate in this article, has a dramatic effect (200-300%) on the formation of the precipitating fluxes that result in the diffuse aurora. It is shown that wave-particle interaction processes that drive precipitating fluxes in the region of diffuse aurora from the magnetospheric altitudes are only the first step in the formation of electron precipitation at ionospheric altitudes, and they cannot be separated from the atmospheric collisional machine that redistributes and transfers their energy inside the magnetosphere-ionosphere-atmosphere coupling system.

Major pathways to electron distribution function formation in regions of diffuse aurora

NASA Astrophysics Data System (ADS)

Khazanov, George V.; Sibeck, David G.; Zesta, Eftyhia

2017-04-01

This paper discusses the major pathways of electron distribution function formation in the region of diffuse aurora. The diffuse aurora accounts for about of 75% of the auroral energy precipitating into the upper atmosphere, and its origin has been the subject of much discussion. We show that an earthward stream of precipitating electrons initially injected from the Earth's plasma sheet via wave-particle interactions degrades in the atmosphere toward lower energies and produces secondary electrons via impact ionization of the neutral atmosphere. These electrons of magnetospheric origin are then reflected back into the magnetosphere along closed dipolar magnetic field lines, leading to a series of reflections and consequent magnetospheric interactions that greatly augment the initially precipitating flux at the upper ionospheric boundary (700-800 km). To date this, systematic magnetosphere-ionosphere coupling element has not been included in auroral research models, and, as we demonstrate in this article, has a dramatic effect (200-300%) on the formation of the precipitating fluxes that result in the diffuse aurora. It is shown that wave-particle interaction processes that drive precipitating fluxes in the region of diffuse aurora from the magnetospheric altitudes are only the first step in the formation of electron precipitation at ionospheric altitudes, and they cannot be separated from the atmospheric "collisional machine" that redistributes and transfers their energy inside the magnetosphere-ionosphere-atmosphere coupling system.

Diffused sunlight driven highly synergistic pathway for complete mineralization of organic contaminants using reduced graphene oxide supported photocatalyst.

PubMed

Babu, Sundaram Ganesh; Ramalingam Vinoth; Neppolian, Bernaurdshaw; Dionysiou, Dionysios D; Ashokkumar, Muthupandian

2015-06-30

Diffused sunlight is found to be an effective light source for the efficient degradation and mineralization of organic pollutant (methyl orange as a probe) by sono-photocatalytic degradation using reduced graphene oxide (rGO) supported CuO-TiO2 photocatalyst. The prepared catalysts are characterized by XRD, XPS, UV-vis DRS, PL, photoelectrochemical, SEM-EDS and TEM. A 10 fold synergy is achieved for the first time by combining sonochemical and photocatalytic degradation under diffused sunlight. rGO loading augments the activity of bare CuO-TiO2 more than two fold. The ability of rGO in storing, transferring, and shuttling electrons at the heterojunction between TiO2 and CuO facilitates the separation of photogenerated electron-hole pairs, as evidenced by the photoluminescence results. The complete mineralization of MO and the by-products within a short span of time is confirmed by TOC analysis. Further, hydroxyl radical mediated degradation under diffused sunlight is confirmed by LC-MS. This system shows similar activity for the degradation of methylene blue and 4-chlorophenol indicating the versatility of the catalyst for the degradation of various pollutants. This investigation is likely to open new possibilities for the development of highly efficient diffused sunlight driven TiO2 based photocatalysts for the complete mineralization of organic contaminants. Copyright © 2015 Elsevier B.V. All rights reserved.

Physics-based agent to simulant correlations for vapor phase mass transport.

PubMed

Willis, Matthew P; Varady, Mark J; Pearl, Thomas P; Fouse, Janet C; Riley, Patrick C; Mantooth, Brent A; Lalain, Teri A

2013-12-15

Chemical warfare agent simulants are often used as an agent surrogate to perform environmental testing, mitigating exposure hazards. This work specifically addresses the assessment of downwind agent vapor concentration resulting from an evaporating simulant droplet. A previously developed methodology was used to estimate the mass diffusivities of the chemical warfare agent simulants methyl salicylate, 2-chloroethyl ethyl sulfide, di-ethyl malonate, and chloroethyl phenyl sulfide. Along with the diffusivity of the chemical warfare agent bis(2-chloroethyl) sulfide, the simulant diffusivities were used in an advection-diffusion model to predict the vapor concentrations downwind from an evaporating droplet of each chemical at various wind velocities and temperatures. The results demonstrate that the simulant-to-agent concentration ratio and the corresponding vapor pressure ratio are equivalent under certain conditions. Specifically, the relationship is valid within ranges of measurement locations relative to the evaporating droplet and observation times. The valid ranges depend on the relative transport properties of the agent and simulant, and whether vapor transport is diffusion or advection dominant. Published by Elsevier B.V.

Evaluation of diffuse-illumination holographic cinematography in a flutter cascade

NASA Technical Reports Server (NTRS)

Decker, A. J.

1986-01-01

Since 1979, the Lewis Research Center has examined holographic cinematography for three-dimensional flow visualization. The Nd:YAG lasers used were Q-switched, double-pulsed, and frequency-doubled, operating at 20 pulses per second. The primary subjects for flow visualization were the shock waves produced in two flutter cascades. Flow visualization was by diffuse-illumination, double-exposure, and holographic interferometry. The performances of the lasers, holography, and diffuse-illumination interferometry are evaluated in single-window wind tunnels. The fringe-contrast factor is used to evaluate the results. The effects of turbulence on shock-wave visualization in a transonic flow are discussed. The depth of field for visualization of a turbulent structure is demonstrated to be a measure of the relative density and scale of that structure. Other items discussed are the holographic emulsion, tests of coherence and polarization, effects of windows and diffusers, hologram bleaching, laser configurations, influence and handling of specular reflections, modes of fringe localization, noise sources, and coherence requirements as a function of the pulse energy. Holography and diffuse illumination interferometry are also reviewed.

Diffusive shock acceleration at non-relativistic highly oblique shocks

NASA Astrophysics Data System (ADS)

Meli, Athina; Biermann, P. L.

2004-10-01

Our aim here is to evaluate the rate of the maximum energy and the acceleration rate that Cosmic Rays (CRs) acquire in the non-relativistic diffusive shock acceleration as it could apply during their lifetime in various astrophysical sites. We examine numerically (using Monte Carlo simulations) the effect of the diffusion coefficients on the energy gain and the acceleration rate, by testing the role between the obliquity of the magnetic field at the shock normal, and the significance of both perpendicular cross-field diffusion and parallel diffusion coefficients to the aceleration rate. We find (and justify previous analytical work -Jokipii 1987) that in highly oblique shocks the smaller the perpendicular diffusion gets compared to the parallel diffusion coefficient values, the greater the energy gain of the CRs to be obtained. An explanation of the Cosmic Ray Spectrum in High Energies, between 1015 and 1018eV is claimed, as we estimate the upper limit of energy that CRs could gain in plausible astrophysical regimes; interpreted by the scenario of CRs which are injected by three different kind of sources, (i) supernovae (SN) which explode into the interstellar medium (ISM), (ii) Red Supergiants (RSG), and (iii) Wolf-Rayet stars (WR), where the two latter explode into their pre-SN winds Biermann (2001); Sina (2001).

EMMI-Electric solar wind sail facilitated Manned Mars Initiative

NASA Astrophysics Data System (ADS)

Janhunen, Pekka; Merikallio, Sini; Paton, Mark

2015-08-01

The novel propellantless electric solar wind sail concept promises efficient low thrust transportation in the Solar System outside Earth's magnetosphere. Combined with asteroid mining to provide water and synthetic cryogenic rocket fuel in orbits of Earth and Mars, possibilities for affordable continuous manned presence on Mars open up. Orbital fuel and water enable reusable bidirectional Earth-Mars vehicles for continuous manned presence on Mars and allow smaller fuel fraction of spacecraft than what is achievable by traditional means. Water can also be used as radiation shielding of the manned compartment, thus reducing the launch mass further. In addition, the presence of fuel in the orbit of Mars provides the option for an all-propulsive landing, thus potentially eliminating issues of heavy heat shields and augmenting the capability of pinpoint landing. With this E-sail enabled scheme, the recurrent cost of continuous bidirectional traffic between Earth and Mars might ultimately approach the recurrent cost of running the International Space Station, ISS.

Chloroquine diphosphate bearing dextran nanoparticles augmented drug delivery and overwhelmed drug resistance in Plasmodium falciparum parasites.

PubMed

Kashyap, Aman; Kaur, Rupinder; Baldi, Ashish; Jain, Upendra Kumar; Chandra, Ramesh; Madan, Jitender

2018-07-15

Chloroquine diphosphate (CHQ) is primarily used for the treatment of Plasmodium falciparum malaria at the dose of 500mg orally or 10mg/kg parenterally. However, point mutations in Plasmodiumfalciparum chloroquine resistance transporter (PfCRT) protein and Plasmodium falciparum multidrug resistance protein 1 (Pfmdr1) localized in digestive vacuole membrane, are responsible for CHQ resistance. Therefore, in present investigation, dextran nanoparticles bearing chloroquine diphosphate (CHQ-DEX-NPs) were formulated by solvent diffusion method of size below 70nm with zeta-potential of -20.1±3.2mV. FT-IR, DSC and PXRD techniques confirmed the successful loading of drug in nanomatrix system with amorphous attributes. In vitro drug release analysis indicated the Higuchi pattern with diffusion controlled drug release. The IC 50 of CHQ-DEX-NPs in sensitive (3D7) and resistant (RKL9) Plasmodium falciparum strains was estimated to be 0.031-μg/ml and 0.13-μg/ml significantly lower than 0.059-μg/ml and 0.36-μg/ml of CHQ. The augmented therapeutic efficacy of CHQ-DEX-NPs may be credited to deposition of tailored nanoparticles in food vacuoles of malaria parasites owing to the affinity of parasite towards DEX that consequently lower the drug resistance and improved the therapeutic index. In conclusion, CHQ-DEX-NPs must be evaluated under a set of stringent in vivo parameters to establish its therapeutic efficacy in preclinical model. Copyright © 2018 Elsevier B.V. All rights reserved.

Impact of Virtual and Augmented Reality Based on Intraoperative Magnetic Resonance Imaging and Functional Neuronavigation in Glioma Surgery Involving Eloquent Areas.

PubMed

Sun, Guo-Chen; Wang, Fei; Chen, Xiao-Lei; Yu, Xin-Guang; Ma, Xiao-Dong; Zhou, Ding-Biao; Zhu, Ru-Yuan; Xu, Bai-Nan

2016-12-01

The utility of virtual and augmented reality based on functional neuronavigation and intraoperative magnetic resonance imaging (MRI) for glioma surgery has not been previously investigated. The study population consisted of 79 glioma patients and 55 control subjects. Preoperatively, the lesion and related eloquent structures were visualized by diffusion tensor tractography and blood oxygen level-dependent functional MRI. Intraoperatively, microscope-based functional neuronavigation was used to integrate the reconstructed eloquent structure and the real head and brain, which enabled safe resection of the lesion. Intraoperative MRI was used to verify brain shift during the surgical process and provided quality control during surgery. The control group underwent surgery guided by anatomic neuronavigation. Virtual and augmented reality protocols based on functional neuronavigation and intraoperative MRI provided useful information for performing tailored and optimized surgery. Complete resection was achieved in 55 of 79 (69.6%) glioma patients and 20 of 55 (36.4%) control subjects, with average resection rates of 95.2% ± 8.5% and 84.9% ± 15.7%, respectively. Both the complete resection rate and average extent of resection differed significantly between the 2 groups (P < 0.01). Postoperatively, the rate of preservation of neural functions (motor, visual field, and language) was lower in controls than in glioma patients at 2 weeks and 3 months (P < 0.01). Combining virtual and augmented reality based on functional neuronavigation and intraoperative MRI can facilitate resection of gliomas involving eloquent areas. Copyright © 2016 Elsevier Inc. All rights reserved.

Fusion of a FBG-based health monitoring system for wind turbines with a fiber-optic lightning detection system

NASA Astrophysics Data System (ADS)

Krämer, Sebastian G. M.; Wiesent, Benjamin; Müller, Mathias S.; Puente León, Fernando; Méndez Hernández, Yarú

2008-04-01

Wind turbine blades are made of composite materials and reach a length of more than 42 meters. Developments for modern offshore turbines are working on about 60 meters long blades. Hence, with the increasing height of the turbines and the remote locations of the structures, health monitoring systems are becoming more and more important. Therefore, fiber-optic sensor systems are well-suited, as they are lightweight, immune against electromagnetic interference (EMI), and as they can be multiplexed. Based on two separately existing concepts for strain measurements and lightning detection on wind turbines, a fused system is presented. The strain measurement system is based on a reflective fiber-Bragg-grating (FBG) network embedded in the composite structure of the blade. For lightning detection, transmissive &fiber-optic magnetic field sensors based on the Faraday effect are used to register the lightning parameters and estimate the impact point. Hence, an existing lightning detection system will be augmented, due to the fusion, by the capability to measure strain, temperature and vibration. Load, strain, temperature and impact detection information can be incorporated into the turbine's monitoring or SCADA system and remote controlled by operators. Data analysis techniques allow dynamic maintenance scheduling to become a reality, what is of special interest for the cost-effective maintenance of large offshore or badly attainable onshore wind parks. To prove the feasibility of this sensor fusion on one optical fiber, interferences between both sensor systems are investigated and evaluated.

Winds and tides of Ligeia Mare, with application to the drift of the proposed time TiME (Titan Mare Explorer) capsule

NASA Astrophysics Data System (ADS)

Lorenz, Ralph D.; Tokano, Tetsuya; Newman, Claire E.

2012-01-01

We use two independent General Circulation Models (GCMs) to estimate surface winds at Titan’s Ligeia Mare (78° N, 250° W), motivated by a proposed mission to land a floating capsule in this ∼500 km hydrocarbon sea. The models agree on the overall magnitude (∼0.5-1 m/s) and seasonal variation (strongest in summer) of windspeeds, but details of seasonal and diurnal variation of windspeed and direction differ somewhat, with the role of surface exchanges being more significant than that of gravitational tides in the atmosphere. We also investigate the tidal dynamics in the sea using a numerical ocean dynamics model: assuming a rigid lithosphere, the tidal amplitude is up to ∼0.8 m. Tidal currents are overall proportional to the reciprocal of depth-with an assumed central depth of 300 m, the characteristic tidal currents are ∼1 cm/s, with notable motions being a slosh between Ligeia’s eastern and western lobes, and a clockwise flow pattern. We find that a capsule will drift at approximately one tenth of the windspeed, unless measures are adopted to augment the drag areas above or below the waterline. Thus motion of a floating capsule is dominated by the wind, and is likely to be several km per Earth day, a rate that will be readily measured from Earth by radio navigation methods. In some instances, the wind vector rotates diurnally such that the drift trajectory is epicyclic.

Cosmic Ray Acceleration from Multiple Galactic Wind Shocks

NASA Astrophysics Data System (ADS)

Cotter, Cory; Bustard, Chad; Zweibel, Ellen

2018-01-01

Cosmic rays still have an unknown origin. Many mechanisms have been suggested for their acceleration including quasars, pulsars, magnetars, supernovae, supernova remnants, and galactic termination shocks. The source of acceleration may be a mixture of these and a different mixture in different energy regimes. Using numerical simulations, we investigate multiple shocks in galactic winds as potential cosmic rays sources. By having shocks closer to the parent galaxy, more particles may diffuse back to the disk instead of being blown out in the wind, as found in Bustard, Zweibel, and Cotter (2017, ApJ) and also Merten, Bustard, Zweibel, and Tjus (to be submitted to ApJ). Specifically, this flux of cosmic rays could contribute to the unexplained "shin" region between the well-known "knee" and "ankle" of the cosmic ray spectrum. We would like to acknowledge support from the National Science Foundation (NSF) Graduate Research Fellowship Program under grant No. DGE-125625 and NSF grant No. AST-1616037.

Use of 3D Printing for Custom Wind Tunnel Fabrication

NASA Astrophysics Data System (ADS)

Gagorik, Paul; Bates, Zachary; Issakhanian, Emin

2016-11-01

Small-scale wind tunnels for the most part are fairly simple to produce with standard building equipment. However, the intricate bell housing and inlet shape of an Eiffel type wind tunnel, as well as the transition from diffuser to fan in a rectangular tunnel can present design and construction obstacles. With the help of 3D printing, these shapes can be custom designed in CAD models and printed in the lab at very low cost. The undergraduate team at Loyola Marymount University has built a custom benchtop tunnel for gas turbine film cooling experiments. 3D printing is combined with conventional construction methods to build the tunnel. 3D printing is also used to build the custom tunnel floor and interchangeable experimental pieces for various experimental shapes. This simple and low-cost tunnel is a custom solution for specific engineering experiments for gas turbine technology research.

Dynamical influences on thermospheric composition: implications for semi-empirical models

NASA Astrophysics Data System (ADS)

Sutton, E. K.; Solomon, S. C.

2014-12-01

The TIE-GCM was recently augmented to include helium and argon, two approximately inert species that can be used as tracers of dynamics in the thermosphere. The former species is treated as a major species due to its large abundance near the upper boundary. The effects of exospheric transport are also included in order to simulate realistic seasonal and latitudinal helium distributions. The latter species is treated as a classical minor species, imparting absolutely no forces on the background atmosphere. In this study, we examine the interplay of the various dynamical terms - i.e. background circulation, molecular and Eddy diffusion - as they drive departures from the distributions that would be expected under the assumption of diffusive equilibrium. As this has implications on the formulation of all empirical thermospheric models, we use this understanding to address the following questions: (1) how do errors caused by the assumption of diffusive equilibrium manifest within empirical models of the thermosphere? and (2) where and when does an empirical model's output disagree with its underlying datasets due to the inherent limitations of said model's formulation?

Markov Chain Monte Carlo in the Analysis of Single-Molecule Experimental Data

NASA Astrophysics Data System (ADS)

Kou, S. C.; Xie, X. Sunney; Liu, Jun S.

2003-11-01

This article provides a Bayesian analysis of the single-molecule fluorescence lifetime experiment designed to probe the conformational dynamics of a single DNA hairpin molecule. The DNA hairpin's conformational change is initially modeled as a two-state Markov chain, which is not observable and has to be indirectly inferred. The Brownian diffusion of the single molecule, in addition to the hidden Markov structure, further complicates the matter. We show that the analytical form of the likelihood function can be obtained in the simplest case and a Metropolis-Hastings algorithm can be designed to sample from the posterior distribution of the parameters of interest and to compute desired estiamtes. To cope with the molecular diffusion process and the potentially oscillating energy barrier between the two states of the DNA hairpin, we introduce a data augmentation technique to handle both the Brownian diffusion and the hidden Ornstein-Uhlenbeck process associated with the fluctuating energy barrier, and design a more sophisticated Metropolis-type algorithm. Our method not only increases the estimating resolution by several folds but also proves to be successful for model discrimination.

Diffusive shock acceleration - Acceleration rate, magnetic-field direction and the diffusion limit

NASA Technical Reports Server (NTRS)

Jokipii, J. R.

1992-01-01

This paper reviews the concept of diffusive shock acceleration, showing that the acceleration of charged particles at a collisionless shock is a straightforward consequence of the standard cosmic-ray transport equation, provided that one treats the discontinuity at the shock correctly. This is true for arbitrary direction of the upstream magnetic field. Within this framework, it is shown that acceleration at perpendicular or quasi-perpendicular shocks is generally much faster than for parallel shocks. Paradoxically, it follows also that, for a simple scattering law, the acceleration is faster for less scattering or larger mean free path. Obviously, the mean free path can not become too large or the diffusion limit becomes inapplicable. Gradient and curvature drifts caused by the magnetic-field change at the shock play a major role in the acceleration process in most cases. Recent observations of the charge state of the anomalous component are shown to require the faster acceleration at the quasi-perpendicular solar-wind termination shock.

Unsteady Sail Dynamics in Olympic Class Sailboats

NASA Astrophysics Data System (ADS)

Williamson, Charles; Schutt, Riley

2016-11-01

Unsteady sailing techniques have evolved in competitive sailboat fleets, in cases where the relative weight of the sailor is sufficient to impart unsteady motions to the boat and sails. We will discuss three types of motion that are used by athletes to propel their boats on an Olympic race course faster than using the wind alone. In all of our cases, body weight movements induce unsteady sail motion, increasing driving force and speed through the water. In this research, we explore the dynamics of an Olympic class Laser sailboat equipped with a GPS, IMU, wind sensor, and a 6-GoPro camera array. We shall briefly discuss "sail flicking", whereby the helmsman periodically rolls the sail into the apparent wind, at an angle which is distinct from classical heave (in our case, the oscillations are not normal to the apparent flow). We also demonstrate "roll tacking", where there are considerable advantages to rolling the boat during such a maneuver, especially in light wind. In both of the above examples from on-the-water studies, corresponding experiments using a towing tank exhibit increases in the driving force, associated with the formation of strong vortex pairs into the flow. Finally, we focus on a technique known as "S-curving" in the case where the boat sails downwind. In contrast to the previous cases, it is drag force rather than lift force that the sailor is trying to maximise as the boat follows a zig-zag trajectory. The augmented apparent wind strength due to the oscillatory sail motion, and the growth of strong synchronised low-pressure wake vortices on the low-pressure side of the sail, contribute to the increase in driving force, and velocity-made-good downwind.

Non-hoop winding effect on bonding temperature of laser assisted tape winding process

NASA Astrophysics Data System (ADS)

Zaami, Amin; Baran, Ismet; Akkerman, Remko

2018-05-01

One of the advanced methods for production of thermoplastic composite methods is laser assisted tape winding (LATW). Predicting the temperature in LATW process is very important since the temperature at nip-point (bonding line through width) plays a pivotal role in a proper bonding and hence the mechanical performance. Despite the hoop-winding where the nip-point is the straight line, non-hoop winding includes a curved nip-point line. Hence, the non-hoop winding causes somewhat a different power input through laser-rays and-reflections and consequently generates unknown complex temperature profile on the curved nip-point line. Investigating the temperature at the nip-point line is the point of interest in this study. In order to understand this effect, a numerical model is proposed to capture the effect of laser-rays and their reflections on the nip-point temperature. To this end, a 3D optical model considering the objects in LATW process is considered. Then, the power distribution (absorption and reflection) from the optical analysis is used as an input (heat flux distribution) for the thermal analysis. The thermal analysis employs a fully-implicit advection-diffusion model to calculate the temperature on the surfaces. The results are examined to demonstrate the effect of winding direction on the curved nip-point line (tape width) which has not been considered in literature up to now. Furthermore, the results can be used for designing a better and more efficient setup in the LATW process.

Some remarks on the design of transonic tunnels with low levels of flow unsteadiness

NASA Technical Reports Server (NTRS)

Mabey, D. G.

1976-01-01

The principal sources of flow unsteadiness in the circuit of a transonic wind tunnel are presented. Care must be taken to avoid flow separations, acoustic resonances and large scale turbulence. Some problems discussed are the elimination of diffuser separations, the aerodynamic design of coolers and the unsteadiness generated in ventilated working sections.

On The Origin Of Two-Shell Supernova Remnants

NASA Astrophysics Data System (ADS)

Gvaramadze, Vasilii

2007-07-01

The proper motion of massive stars could cause them to explode far from the geometric centers of their wind-driven bubbles and thereby could affect the symmetry of the resulting diffuse supernova remnants (SNRs). We use this fact to explain the origin of SNRs consisting of two partially overlapping shells (e.g. Cygnus Loop, 3C 400.2, etc.).

The viability of photovoltaics on the Martian surface

NASA Technical Reports Server (NTRS)

Gaier, James R.; Perez-Davis, Marla E.

1994-01-01

The viability of photovoltaics (PV) on the Martian surface may be determined by their ability to withstand significant degradation in the Martian environment. Probably the greatest threat is posed by fine dust particles which are continually blown about the surface of the planet. In an effort to determine the extent of the threat, and to investigate some abatement strategies, a series of experiments were conducted in the Martian Surface Wind Tunnel (MARSWIT) at NASA Ames Research Center. The effects of dust composition, particle size, wind velocity, angle of attack, and protective coatings on the transmittance of light through PV coverglass were determined. Both initially clear and initially dusted samples were subjected both to clear winds and simulated dust storms in the MARSWIT. It was found that wind velocity, particle size, and angle of attack are important parameters affecting occlusion of PV surfaces, while dust composition and protective coatings were not. Neither induced turbulence nor direct current biasing up to 200 volts were effective abatement techniques. Abrasion diffused the light impinging on the PV cells, but did not reduce total coverglass transmittance by more than a few percent.

Supernova shock breakout through a wind

NASA Astrophysics Data System (ADS)

Balberg, Shmuel; Loeb, Abraham

2011-06-01

The breakout of a supernova shock wave through the progenitor star's outer envelope is expected to appear as an X-ray flash. However, if the supernova explodes inside an optically thick wind, the breakout flash is delayed. We present a simple model for estimating the conditions at shock breakout in a wind based on the general observable quantities in the X-ray flash light curve; the total energy EX, and the diffusion time after the peak, tdiff. We base the derivation on the self-similar solution for the forward-reverse shock structure expected for an ejecta plowing through a pre-existing wind at large distances from the progenitor's surface. We find simple quantitative relations for the shock radius and velocity at breakout. By relating the ejecta density profile to the pre-explosion structure of the progenitor, the model can also be extended to constrain the combination of explosion energy and ejecta mass. For the observed case of XRO08109/SN2008D, our model provides reasonable constraints on the breakout radius, explosion energy and ejecta mass, and predicts a high shock velocity which naturally accounts for the observed non-thermal spectrum.

Low rate loading-induced convection enhances net transport into the intervertebral disc in vivo.

PubMed

Gullbrand, Sarah E; Peterson, Joshua; Mastropolo, Rosemarie; Roberts, Timothy T; Lawrence, James P; Glennon, Joseph C; DiRisio, Darryl J; Ledet, Eric H

2015-05-01

The intervertebral disc primarily relies on trans-endplate diffusion for the uptake of nutrients and the clearance of byproducts. In degenerative discs, diffusion is often diminished by endplate sclerosis and reduced proteoglycan content. Mechanical loading-induced convection has the potential to augment diffusion and enhance net transport into the disc. The ability of convection to augment disc transport is controversial and has not been demonstrated in vivo. To determine if loading-induced convection can enhance small molecule transport into the intervertebral disc in vivo. Net transport was quantified via postcontrast enhanced magnetic resonance imaging (MRI) into the discs of the New Zealand white rabbit lumbar spine subjected to in vivo cyclic low rate loading. Animals were administered the MRI contrast agent gadodiamide intravenously and subjected to in vivo low rate loading (0.5 Hz, 200 N) via a custom external loading apparatus for either 2.5, 5, 10, 15, or 20 minutes. Animals were then euthanized and the lumbar spines imaged using postcontrast enhanced MRI. The T1 constants in the nucleus, annulus, and cartilage endplates were quantified as a measure of gadodiamide transport into the loaded discs compared with the adjacent unloaded discs. Microcomputed tomography was used to quantify subchondral bone density. Low rate loading caused the rapid uptake and clearance of gadodiamide in the nucleus compared with unloaded discs, which exhibited a slower rate of uptake. Relative to unloaded discs, low rate loading caused a maximum increase in transport into the nucleus of 16.8% after 5 minutes of loading. Low rate loading increased the concentration of gadodiamide in the cartilage endplates at each time point compared with unloaded levels. Results from this study indicate that forced convection accelerated small molecule uptake and clearance in the disc induced by low rate mechanical loading. Low rate loading may, therefore, be therapeutic to the disc as it may enhance the nutrient uptake and waste product clearance. Copyright © 2015 Elsevier Inc. All rights reserved.

The SILCC project - III. Regulation of star formation and outflows by stellar winds and supernovae

NASA Astrophysics Data System (ADS)

Gatto, Andrea; Walch, Stefanie; Naab, Thorsten; Girichidis, Philipp; Wünsch, Richard; Glover, Simon C. O.; Klessen, Ralf S.; Clark, Paul C.; Peters, Thomas; Derigs, Dominik; Baczynski, Christian; Puls, Joachim

2017-04-01

We study the impact of stellar winds and supernovae on the multiphase interstellar medium using three-dimensional hydrodynamical simulations carried out with FLASH. The selected galactic disc region has a size of (500 pc)2 × ±5 kpc and a gas surface density of 10 M⊙ pc-2. The simulations include an external stellar potential and gas self-gravity, radiative cooling and diffuse heating, sink particles representing star clusters, stellar winds from these clusters that combine the winds from individual massive stars by following their evolution tracks, and subsequent supernova explosions. Dust and gas (self-) shielding is followed to compute the chemical state of the gas with a chemical network. We find that stellar winds can regulate star (cluster) formation. Since the winds suppress the accretion of fresh gas soon after the cluster has formed, they lead to clusters that have lower average masses (102-104.3 M⊙) and form on shorter time-scales (10-3-10 Myr). In particular, we find an anticorrelation of cluster mass and accretion time-scale. Without winds, the star clusters easily grow to larger masses for ˜5 Myr until the first supernova explodes. Overall, the most massive stars provide the most wind energy input, while objects beginning their evolution as B-type stars contribute most of the supernova energy input. A significant outflow from the disc (mass loading ≳1 at 1 kpc) can be launched by thermal gas pressure if more than 50 per cent of the volume near the disc mid-plane can be heated to T > 3 × 105 K. Stellar winds alone cannot create a hot volume-filling phase. The models that are in best agreement with observed star formation rates drive either no outflows or weak outflows.

Solar Wind Ablation of Terrestrial Planet Atmospheres

NASA Technical Reports Server (NTRS)

Moore, Thomas Earle; Fok, Mei-Ching H.; Delcourt, Dominique C.

2009-01-01

Internal plasma sources usually arise in planetary magnetospheres as a product of stellar ablation processes. With the ignition of a new star and the onset of its ultraviolet and stellar wind emissions, much of the volatiles in the stellar system undergo a phase transition from gas to plasma. Condensation and accretion into a disk is replaced by radiation and stellar wind ablation of volatile materials from the system- Planets or smaller bodies that harbor intrinsic magnetic fields develop an apparent shield against direct stellar wind impact, but UV radiation still ionizes their gas phases, and the resulting internal plasmas serve to conduct currents to and from the central body along reconnected magnetic field linkages. Photoionization and thermalization of electrons warms the ionospheric topside, enhancing Jeans' escape of super-thermal particles, with ambipolar diffusion and acceleration. Moreover, observations and simulations of auroral processes at Earth indicate that solar wind energy dissipation is concentrated by the geomagnetic field by a factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Thus internal plasmas enable coupling with the plasma, neutral gas and by extension, the entire body. The stellar wind is locally loaded and slowed to develop the required power. The internal source plasma is accelerated and heated, inflating the magnetosphere as it seeks escape, and is ultimately blown away in the stellar wind. Bodies with little sensible atmosphere may still produce an exosphere of sputtered matter when exposed to direct solar wind impact. Bodies with a magnetosphere and internal sources of plasma interact more strongly with the stellar wind owing to the magnetic linkage between the two created by reconnection.

Motion of charged particles normal to an irregular magnetic field. [astrophysical plasmas

NASA Technical Reports Server (NTRS)

Jokipii, J. R.

1975-01-01

The motion is analyzed of charged particles in a fluctuating magnetic field which varies only in directions normal to its mean direction, such as that which would be generated by an ensemble of magnetosonic waves propagating normal to an ambient magnetic field. The appropriate generalization of gradient-drift motion is derived in terms of the power spectrum of the magnetic fluctuations, and an effective spatial diffusion coefficient is obtained. Several special cases are considered, including a Gaussian power spectrum, a power-law spectrum with a cutoff, and a general power-law spectrum. A possible magnitude is calculated for the spatial diffusion coefficient of the solar wind.

A Simple Method for High-Lift Propeller Conceptual Design

NASA Technical Reports Server (NTRS)

Patterson, Michael; Borer, Nick; German, Brian

2016-01-01

In this paper, we present a simple method for designing propellers that are placed upstream of the leading edge of a wing in order to augment lift. Because the primary purpose of these "high-lift propellers" is to increase lift rather than produce thrust, these props are best viewed as a form of high-lift device; consequently, they should be designed differently than traditional propellers. We present a theory that describes how these props can be designed to provide a relatively uniform axial velocity increase, which is hypothesized to be advantageous for lift augmentation based on a literature survey. Computational modeling indicates that such propellers can generate the same average induced axial velocity while consuming less power and producing less thrust than conventional propeller designs. For an example problem based on specifications for NASA's Scalable Convergent Electric Propulsion Technology and Operations Research (SCEPTOR) flight demonstrator, a propeller designed with the new method requires approximately 15% less power and produces approximately 11% less thrust than one designed for minimum induced loss. Higher-order modeling and/or wind tunnel testing are needed to verify the predicted performance.

Power consumption analysis DBD plasma ozone generator

NASA Astrophysics Data System (ADS)

Nur, M.; Restiwijaya, M.; Muchlisin, Z.; Susan, I. A.; Arianto, F.; Widyanto, S. A.

2016-11-01

Studies on the consumption of energy by an ozone generator with various constructions electrodes of dielectric barrier discharge plasma (DBDP) reactor has been carried out. This research was done to get the configuration of the reactor, that is capable to produce high ozone concentrations with low energy consumption. BDBP reactors were constructed by spiral- cylindrical configuration, plasma ozone was generated by high voltage AC voltage up to 25 kV and maximum frequency of 23 kHz. The reactor consists of an active electrode in the form of a spiral-shaped with variation diameter Dc, and it was made by using copper wire with diameter Dw. In this research, we variated number of loops coil windings N as well as Dc and Dw. Ozone concentrations greater when the wire's diameter Dw and the diameter of the coil windings applied was greater. We found that impedance greater will minimize the concentration of ozone, in contrary to the greater capacitance will increase the concentration of ozone. The ozone concentrations increase with augmenting of power. Maximum power is effective at DBD reactor spiral-cylinder is on the Dc = 20 mm, Dw = 1.2 mm, and the number of coil windings N = 10 loops with the resulting concentration is greater than 20 ppm and it consumes energy of 177.60 watts

Neural Flight Control System

NASA Technical Reports Server (NTRS)

Gundy-Burlet, Karen

2003-01-01

The Neural Flight Control System (NFCS) was developed to address the need for control systems that can be produced and tested at lower cost, easily adapted to prototype vehicles and for flight systems that can accommodate damaged control surfaces or changes to aircraft stability and control characteristics resulting from failures or accidents. NFCS utilizes on a neural network-based flight control algorithm which automatically compensates for a broad spectrum of unanticipated damage or failures of an aircraft in flight. Pilot stick and rudder pedal inputs are fed into a reference model which produces pitch, roll and yaw rate commands. The reference model frequencies and gains can be set to provide handling quality characteristics suitable for the aircraft of interest. The rate commands are used in conjunction with estimates of the aircraft s stability and control (S&C) derivatives by a simplified Dynamic Inverse controller to produce virtual elevator, aileron and rudder commands. These virtual surface deflection commands are optimally distributed across the aircraft s available control surfaces using linear programming theory. Sensor data is compared with the reference model rate commands to produce an error signal. A Proportional/Integral (PI) error controller "winds up" on the error signal and adds an augmented command to the reference model output with the effect of zeroing the error signal. In order to provide more consistent handling qualities for the pilot, neural networks learn the behavior of the error controller and add in the augmented command before the integrator winds up. In the case of damage sufficient to affect the handling qualities of the aircraft, an Adaptive Critic is utilized to reduce the reference model frequencies and gains to stay within a flyable envelope of the aircraft.

Influence of the bound polymer layer on nanoparticle diffusion in polymer melts

DOE PAGES

Griffin, Philip J.; Bocharova, Vera; Middleton, L. Robert; ...

2016-09-23

We measure the center-of-mass diffusion of silica nanoparticles (NPs) in entangled poly(2-vinylpyridine) (P2VP) melts using Rutherford backscattering spectrometry. While these NPs are well within the size regime where enhanced, nonhydrodynamic NP transport is theoretically predicted and has been observed experimentally (2R NP/d tube ≈ 3, where 2R NP is the NP diameter and d tube is the tube diameter), we find that the diffusion of these NPs in P2VP is in fact well-described by the hydrodynamic Stokes–Einstein relation. The effective NP diameter 2R eff is significantly larger than 2R NP and strongly dependent on P2VP molecular weight, consistent with themore » presence of a bound polymer layer on the NP surface with thickness h eff ≈ 1.1R g. Our results show that the bound polymer layer significantly augments the NP hydrodynamic size in polymer melts with attractive polymer–NP interactions and effectively transitions the mechanism of NP diffusion from the nonhydrodynamic to hydrodynamic regime, particularly at high molecular weights where NP transport is expected to be notably enhanced. Lastly, these results provide the first experimental demonstration that hydrodynamic NP transport in polymer melts requires particles of size ≳5d tube, consistent with recent theoretical predictions.« less

High-Dimensional Intrinsic Interpolation Using Gaussian Process Regression and Diffusion Maps

DOE PAGES

Thimmisetty, Charanraj A.; Ghanem, Roger G.; White, Joshua A.; ...

2017-10-10

This article considers the challenging task of estimating geologic properties of interest using a suite of proxy measurements. The current work recast this task as a manifold learning problem. In this process, this article introduces a novel regression procedure for intrinsic variables constrained onto a manifold embedded in an ambient space. The procedure is meant to sharpen high-dimensional interpolation by inferring non-linear correlations from the data being interpolated. The proposed approach augments manifold learning procedures with a Gaussian process regression. It first identifies, using diffusion maps, a low-dimensional manifold embedded in an ambient high-dimensional space associated with the data. Itmore » relies on the diffusion distance associated with this construction to define a distance function with which the data model is equipped. This distance metric function is then used to compute the correlation structure of a Gaussian process that describes the statistical dependence of quantities of interest in the high-dimensional ambient space. The proposed method is applicable to arbitrarily high-dimensional data sets. Here, it is applied to subsurface characterization using a suite of well log measurements. The predictions obtained in original, principal component, and diffusion space are compared using both qualitative and quantitative metrics. Considerable improvement in the prediction of the geological structural properties is observed with the proposed method.« less

High-Dimensional Intrinsic Interpolation Using Gaussian Process Regression and Diffusion Maps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thimmisetty, Charanraj A.; Ghanem, Roger G.; White, Joshua A.

This article considers the challenging task of estimating geologic properties of interest using a suite of proxy measurements. The current work recast this task as a manifold learning problem. In this process, this article introduces a novel regression procedure for intrinsic variables constrained onto a manifold embedded in an ambient space. The procedure is meant to sharpen high-dimensional interpolation by inferring non-linear correlations from the data being interpolated. The proposed approach augments manifold learning procedures with a Gaussian process regression. It first identifies, using diffusion maps, a low-dimensional manifold embedded in an ambient high-dimensional space associated with the data. Itmore » relies on the diffusion distance associated with this construction to define a distance function with which the data model is equipped. This distance metric function is then used to compute the correlation structure of a Gaussian process that describes the statistical dependence of quantities of interest in the high-dimensional ambient space. The proposed method is applicable to arbitrarily high-dimensional data sets. Here, it is applied to subsurface characterization using a suite of well log measurements. The predictions obtained in original, principal component, and diffusion space are compared using both qualitative and quantitative metrics. Considerable improvement in the prediction of the geological structural properties is observed with the proposed method.« less

A Diffuse Interface Model with Immiscibility Preservation

PubMed Central

Tiwari, Arpit; Freund, Jonathan B.; Pantano, Carlos

2013-01-01

A new, simple, and computationally efficient interface capturing scheme based on a diffuse interface approach is presented for simulation of compressible multiphase flows. Multi-fluid interfaces are represented using field variables (interface functions) with associated transport equations that are augmented, with respect to an established formulation, to enforce a selected interface thickness. The resulting interface region can be set just thick enough to be resolved by the underlying mesh and numerical method, yet thin enough to provide an efficient model for dynamics of well-resolved scales. A key advance in the present method is that the interface regularization is asymptotically compatible with the thermodynamic mixture laws of the mixture model upon which it is constructed. It incorporates first-order pressure and velocity non-equilibrium effects while preserving interface conditions for equilibrium flows, even within the thin diffused mixture region. We first quantify the improved convergence of this formulation in some widely used one-dimensional configurations, then show that it enables fundamentally better simulations of bubble dynamics. Demonstrations include both a spherical bubble collapse, which is shown to maintain excellent symmetry despite the Cartesian mesh, and a jetting bubble collapse adjacent a wall. Comparisons show that without the new formulation the jet is suppressed by numerical diffusion leading to qualitatively incorrect results. PMID:24058207

Simple stochastic model for El Niño with westerly wind bursts

PubMed Central

Thual, Sulian; Majda, Andrew J.; Chen, Nan; Stechmann, Samuel N.

2016-01-01

Atmospheric wind bursts in the tropics play a key role in the dynamics of the El Niño Southern Oscillation (ENSO). A simple modeling framework is proposed that summarizes this relationship and captures major features of the observational record while remaining physically consistent and amenable to detailed analysis. Within this simple framework, wind burst activity evolves according to a stochastic two-state Markov switching–diffusion process that depends on the strength of the western Pacific warm pool, and is coupled to simple ocean–atmosphere processes that are otherwise deterministic, stable, and linear. A simple model with this parameterization and no additional nonlinearities reproduces a realistic ENSO cycle with intermittent El Niño and La Niña events of varying intensity and strength as well as realistic buildup and shutdown of wind burst activity in the western Pacific. The wind burst activity has a direct causal effect on the ENSO variability: in particular, it intermittently triggers regular El Niño or La Niña events, super El Niño events, or no events at all, which enables the model to capture observed ENSO statistics such as the probability density function and power spectrum of eastern Pacific sea surface temperatures. The present framework provides further theoretical and practical insight on the relationship between wind burst activity and the ENSO. PMID:27573821

Investigating the role of wind in generating surface currents over the slope area of the Laptev Sea, Arctic Ocean

NASA Astrophysics Data System (ADS)

Patteson, R. N.

2017-12-01

Mixing mechanisms of the Arctic Ocean have profound impacts on sea ice, global ocean dynamics, and arctic communities. This project used a two-year long time series of ocean current velocities collected from eight moorings located on the Eurasian basin, as well as ERA-interim wind data, to compare and assess relationships between current and wind velocities at different depths. Determining the strength of these correlations will further scientific understanding of the degree to which wind influences mixing, with implications for heat flux, diffusion, and sea ice changes. Using statistical analysis, I calculated whether a significant relationship between wind velocity and ocean currents existed beginning at the surface level ( 50m) .The final correlation values, ranging from R = 0.11 to R = 0.28, indicated a weak relationship between wind velocity and ocean currents at the surface for all eight mooring sites. The results for the surface depth imply that correlation likely decreases with increasing depths, and thus further testing of deeper depth levels was unnecessary. This finding suggests that there is another dominant factor at play in the ocean; we postulate that topography exerts a significant influence on subsurface mixing. This study highlights the need for further research of the different mechanisms and their importance in influencing the dynamic structure of the ocean.

A computational study of thrust augmenting ejectors based on a viscous-inviscid approach

NASA Technical Reports Server (NTRS)

Lund, Thomas S.; Tavella, Domingo A.; Roberts, Leonard

1987-01-01

A viscous-inviscid interaction technique is advocated as both an efficient and accurate means of predicting the performance of two-dimensional thrust augmenting ejectors. The flow field is subdivided into a viscous region that contains the turbulent jet and an inviscid region that contains the ambient fluid drawn into the device. The inviscid region is computed with a higher-order panel method, while an integral method is used for the description of the viscous part. The strong viscous-inviscid interaction present within the ejector is simulated in an iterative process where the two regions influence each other en route to a converged solution. The model is applied to a variety of parametric and optimization studies involving ejectors having either one or two primary jets. The effects of nozzle placement, inlet and diffuser shape, free stream speed, and ejector length are investigated. The inlet shape for single jet ejectors is optimized for various free stream speeds and Reynolds numbers. Optimal nozzle tilt and location are identified for various dual-ejector configurations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shahidehpour, Mohammad

Integrating 20% or more wind energy into the system and transmitting large sums of wind energy over long distances will require a decision making capability that can handle very large scale power systems with tens of thousands of buses and lines. There is a need to explore innovative analytical and implementation solutions for continuing reliable operations with the most economical integration of additional wind energy in power systems. A number of wind integration solution paths involve the adoption of new operating policies, dynamic scheduling of wind power across interties, pooling integration services, and adopting new transmission scheduling practices. Such practicesmore » can be examined by the decision tool developed by this project. This project developed a very efficient decision tool called Wind INtegration Simulator (WINS) and applied WINS to facilitate wind energy integration studies. WINS focused on augmenting the existing power utility capabilities to support collaborative planning, analysis, and wind integration project implementations. WINS also had the capability of simulating energy storage facilities so that feasibility studies of integrated wind energy system applications can be performed for systems with high wind energy penetrations. The development of WINS represents a major expansion of a very efficient decision tool called POwer Market Simulator (POMS), which was developed by IIT and has been used extensively for power system studies for decades. Specifically, WINS provides the following superiorities; (1) An integrated framework is included in WINS for the comprehensive modeling of DC transmission configurations, including mono-pole, bi-pole, tri-pole, back-to-back, and multi-terminal connection, as well as AC/DC converter models including current source converters (CSC) and voltage source converters (VSC); (2) An existing shortcoming of traditional decision tools for wind integration is the limited availability of user interface, i.e., decision results are often text-based demonstrations. WINS includes a powerful visualization tool and user interface capability for transmission analyses, planning, and assessment, which will be of great interest to power market participants, power system planners and operators, and state and federal regulatory entities; and (3) WINS can handle extended transmission models for wind integration studies. WINS models include limitations on transmission flow as well as bus voltage for analyzing power system states. The existing decision tools often consider transmission flow constraints (dc power flow) alone which could result in the over-utilization of existing resources when analyzing wind integration. WINS can be used to assist power market participants including transmission companies, independent system operators, power system operators in vertically integrated utilities, wind energy developers, and regulatory agencies to analyze economics, security, and reliability of various options for wind integration including transmission upgrades and the planning of new transmission facilities. WINS can also be used by industry for the offline training of reliability and operation personnel when analyzing wind integration uncertainties, identifying critical spots in power system operation, analyzing power system vulnerabilities, and providing credible decisions for examining operation and planning options for wind integration. Researches in this project on wind integration included (1) Development of WINS; (2) Transmission Congestion Analysis in the Eastern Interconnection; (3) Analysis of 2030 Large-Scale Wind Energy Integration in the Eastern Interconnection; (4) Large-scale Analysis of 2018 Wind Energy Integration in the Eastern U.S. Interconnection. The research resulted in 33 papers, 9 presentations, 9 PhD degrees, 4 MS degrees, and 7 awards. The education activities in this project on wind energy included (1) Wind Energy Training Facility Development; (2) Wind Energy Course Development.« less

Eigensolution analysis of spectral/hp continuous Galerkin approximations to advection-diffusion problems: Insights into spectral vanishing viscosity

NASA Astrophysics Data System (ADS)

Moura, R. C.; Sherwin, S. J.; Peiró, J.

2016-02-01

This study addresses linear dispersion-diffusion analysis for the spectral/hp continuous Galerkin (CG) formulation in one dimension. First, numerical dispersion and diffusion curves are obtained for the advection-diffusion problem and the role of multiple eigencurves peculiar to spectral/hp methods is discussed. From the eigencurves' behaviour, we observe that CG might feature potentially undesirable non-smooth dispersion/diffusion characteristics for under-resolved simulations of problems strongly dominated by either convection or diffusion. Subsequently, the linear advection equation augmented with spectral vanishing viscosity (SVV) is analysed. Dispersion and diffusion characteristics of CG with SVV-based stabilization are verified to display similar non-smooth features in flow regions where convection is much stronger than dissipation or vice-versa, owing to a dependency of the standard SVV operator on a local Péclet number. First a modification is proposed to the traditional SVV scaling that enforces a globally constant Péclet number so as to avoid the previous issues. In addition, a new SVV kernel function is suggested and shown to provide a more regular behaviour for the eigencurves along with a consistent increase in resolution power for higher-order discretizations, as measured by the extent of the wavenumber range where numerical errors are negligible. The dissipation characteristics of CG with the SVV modifications suggested are then verified to be broadly equivalent to those obtained through upwinding in the discontinuous Galerkin (DG) scheme. Nevertheless, for the kernel function proposed, the full upwind DG scheme is found to have a slightly higher resolution power for the same dissipation levels. These results show that improved CG-SVV characteristics can be pursued via different kernel functions with the aid of optimization algorithms.

Experimental Study of Hypersonic Inflatable Aerodynamic Decelerator (HIAD) Aeroshell with Axisymmetric Surface Deflection Patterns

NASA Technical Reports Server (NTRS)

Hollis, Brian R.; Hollingsworth, Kevin E.

2017-01-01

A wind tunnel test program was conducted to obtain aeroheating environment data on Hypersonic Inflatable Aerodynamic Decelerator aeroshells with flexible thermal protection systems. Data were obtained on a set of rigid wind tunnel models with surface deflection patterns of various heights that simulated a range of potential in-flight aeroshell deformations. Wind tunnel testing was conducted at Mach 6 at unit Reynolds numbers from 2.1 × 10(exp 6)/ft to 8.3 × 10(exp 6)/ft and angles of attack from 0 deg to 18 deg. Boundary-layer transition onset and global surface heating distribution measurements were performed using phosphor thermography and flow field images were obtained through schlieren photography. Surface deflections were found to both promote early transition of the boundary layer and to augment heating levels for both laminar and turbulent flows. A complimentary computational flow field study was also performed to provide heating predictions for comparison with the measurements as well as boundary layer flow field properties for use in correlating the data. Correlations of the wind tunnel data were developed to predict deflection effects on boundary layer transition and surface heating and were applied to both the wind tunnel test conditions and to the trajectory of NASA's successful IRVE-3 flight test. In general, the correlations produced at least qualitative agreement with the wind tunnel data, although the heating levels were underpredicted for some of the larger surface deflections. For the flight conditions, the correlations suggested that peak heating levels on the leeward side conical flank of the IRVE-3 vehicle may have exceeded those at nose for times late in the trajectory after the peak heating time point. However, the flight estimates were based on a conservative assumption of surface deflection magnitude (i.e., larger) than likely was produced in flight.

Verification of reflectance models in turbid waters

NASA Technical Reports Server (NTRS)

Tanis, F. J.; Lyzenga, D. R.

1981-01-01

Inherent optical parameters of very turbid waters were used to evaluate existing water reflectance models. Measured upwelling radiance spectra and Monte Carlo simulations of the radiative transfer equations were compared with results from models based upon two flow, quasi-single scattering, augmented isotropic scattering, and power series approximation. Each model was evaluated for three separate components of upwelling radiance: (1) direct sunlight; (2) diffuse skylight; and (3) internally reflected light. Limitations of existing water reflectance models as applied to turbid waters and possible applications to the extraction of water constituent information are discussed.

Rational engineering correlations of diffusional and inertial particle deposition behavior in non-isothermal forced convection environments

NASA Technical Reports Server (NTRS)

Rosner, D. E.; Gokoglu, S. A.; Israel, R.

1982-01-01

A multiparameter correlation approach to the study of particle deposition rates in engineering applications is discussed with reference to two specific examples, one dealing with thermophoretically augmented small particle convective diffusion and the other involving larger particle inertial impaction. The validity of the correlations proposed here is demonstrated through rigorous computations including all relevant phenomena and interactions. Such representations are shown to minimize apparent differences between various geometric, flow, and physicochemical parameters, allowing many apparently different physicochemical situations to be described in a unified way.

Pulsar Wind Nebulae inside Supernova Remnants as Cosmic-Ray PeVatrons

NASA Astrophysics Data System (ADS)

Ohira, Yutaka; Kisaka, Shota; Yamazaki, Ryo

2018-07-01

We propose that cosmic ray PeVatrons are pulsar wind nebulae (PWNe) inside supernova remnants (SNRs). The PWN initially expands into the freely expanding stellar ejecta. Then, the PWN catches up with the shocked region of the SNR, where particles can be slightly accelerated by the back and forth motion between the PWN and the SNR, and some particles diffuse into the PWN. Afterwards the PWN is compressed by the SNR, where the particles in the PWN are accelerated by the adiabatic compression. Using a Monte Carlo simulation, we show that particles accelerated by the SNR to 0.1 PeV can be reaccelerated to 1 PeV until the end of the PWN compression.

Pulsar Wind Nebulae inside Supernova Remnants as Cosmic-Ray PeVatrons

NASA Astrophysics Data System (ADS)

Ohira, Yutaka; Kisaka, Shota; Yamazaki, Ryo

2018-05-01

We propose that cosmic-ray PeVatrons are pulsar wind nebulae (PWNe) inside supernova remnants (SNRs). The PWN initially expands into the freely expanding stellar ejecta. Then, the PWN catches up with the shocked region of the SNR, where particles can be slightly accelerated by the back and forth motion between the PWN and the SNR, and some particles diffuse into the PWN. Afterwards the PWN is compressed by the SNR, where the particles in the PWN are accelerated by the adiabatic compression. Using a Monte Carlo simulation, we show that particles accelerated by the SNR to 0.1 PeV can be reaccelerated to 1 PeV until the end of the PWN compression.

What can be Learned from X-ray Spectroscopy Concerning Hot Gas in Local Bubble and Charge Exchange Processes?

NASA Technical Reports Server (NTRS)

Snowden, Steve

2007-01-01

What can be learned from x-ray spectroscopy in observing hot gas in local bubble and charge exchange processes depends on spectral resolution, instrumental grasp, instrumental energy band, signal-to-nose, field of view, angular resolution and observatory location. Early attempts at x-ray spectroscopy include ROSAT; more recently, astronomers have used diffuse x-ray spectrometers, XMM Newton, sounding rocket calorimeters, and Suzaku. Future observations are expected with calorimeters on the Spectrum Roentgen Gamma mission, and the Solar Wind Charge Exchange (SWCX). The Geospheric SWCX may provide remote sensing of the solar wind and magnetosheath and remote observations of solar CMEs moving outward from the sun.

Viscosity and diffusivity in melts: from unary to multicomponent systems

NASA Astrophysics Data System (ADS)

Chen, Weimin; Zhang, Lijun; Du, Yong; Huang, Baiyun

2014-05-01

Viscosity and diffusivity, two important transport coefficients, are systematically investigated from unary melt to binary to multicomponent melts in the present work. By coupling with Kaptay's viscosity equation of pure liquid metals and effective radii of diffusion species, the Sutherland equation is modified by taking the size effect into account, and further derived into an Arrhenius formula for the convenient usage. Its reliability for predicting self-diffusivity and impurity diffusivity in unary liquids is then validated by comparing the calculated self-diffusivities and impurity diffusivities in liquid Al- and Fe-based alloys with the experimental and the assessed data. Moreover, the Kozlov model was chosen among various viscosity models as the most reliable one to reproduce the experimental viscosities in binary and multicomponent melts. Based on the reliable viscosities calculated from the Kozlov model, the modified Sutherland equation is utilized to predict the tracer diffusivities in binary and multicomponent melts, and validated in Al-Cu, Al-Ni and Al-Ce-Ni melts. Comprehensive comparisons between the calculated results and the literature data indicate that the experimental tracer diffusivities and the theoretical ones can be well reproduced by the present calculations. In addition, the vacancy-wind factor in binary liquid Al-Ni alloys with the increasing temperature is also discussed. What's more, the calculated inter-diffusivities in liquid Al-Cu, Al-Ni and Al-Ag-Cu alloys are also in excellent agreement with the measured and theoretical data. Comparisons between the simulated concentration profiles and the measured ones in Al-Cu, Al-Ce-Ni and Al-Ag-Cu melts are further used to validate the present calculation method.

An Eulerian/Lagrangian coupling procedure for three-dimensional vortical flows

NASA Technical Reports Server (NTRS)

Felici, Helene M.; Drela, Mark

1993-01-01

A coupled Eulerian/Lagrangian method is presented for the reduction of numerical diffusion observed in solutions of 3D vortical flows using standard Eulerian finite-volume time-marching procedures. A Lagrangian particle tracking method, added to the Eulerian time-marching procedure, provides a correction of the Eulerian solution. In turn, the Eulerian solution is used to integrate the Lagrangian state-vector along the particles trajectories. While the Eulerian solution ensures the conservation of mass and sets the pressure field, the particle markers describe accurately the convection properties and enhance the vorticity and entropy capturing capabilities of the Eulerian solver. The Eulerian/Lagrangian coupling strategies are discussed and the combined scheme is tested on a constant stagnation pressure flow in a 90 deg bend and on a swirling pipe flow. As the numerical diffusion is reduced when using the Lagrangian correction, a vorticity gradient augmentation is identified as a basic problem of this inviscid calculation.

The Dynamics of Helium and its Impact on the Upper Thermosphere

NASA Astrophysics Data System (ADS)

Sutton, E. K.; Thayer, J. P.; Wang, W.; Solomon, S. C.; Schmidt, F.

2015-12-01

The TIE-GCM was recently augmented to include helium and argon, two approximately inert species that can be used as tracers of dynamics in the thermosphere. The former species is treated as a major species due to its large abundance near the upper boundary. The effects of exospheric transport are also included in order to simulate realistic seasonal and latitudinal helium distributions. The latter species is treated as a classical minor species, imparting absolutely no forces on the background atmosphere. In this study, we examine the interplay of the various dynamical terms - i.e. background circulation, molecular and Eddy diffusion - as they drive departures from the distributions that would be expected under assumptions of diffusive equilibrium. As this has implications on the formulation of all semi-empirical thermospheric models, we use this understanding to identify the conditions under which helium can significantly affect nowcasts and forecasts of neutral density.

Control strategy on the double-diffusive convection in a nanofluid layer with internal heat generation

NASA Astrophysics Data System (ADS)

Mokhtar, N. F. M.; Khalid, I. K.; Siri, Z.; Ibrahim, Z. B.; Gani, S. S. A.

2017-10-01

The influences of feedback control and internal heat source on the onset of Rayleigh-Bénard convection in a horizontal nanofluid layer is studied analytically due to Soret and Dufour parameters. The confining boundaries of the nanofluid layer (bottom boundary-top boundary) are assumed to be free-free, rigid-free, and rigid-rigid, with a source of heat from below. Linear stability theory is applied, and the eigenvalue solution is obtained numerically using the Galerkin technique. Focusing on the stationary convection, it is shown that there is a positive thermal resistance in the presence of feedback control on the onset of double-diffusive convection, while there is a positive thermal efficiency in the existence of internal heat generation. The possibilities of suppress or augment of the Rayleigh-Bénard convection in a nanofluid layer are also discussed in detail.

Two-dimensional wave patterns of spreading depolarization: Retracting, re-entrant, and stationary waves

NASA Astrophysics Data System (ADS)

Dahlem, Markus A.; Graf, Rudolf; Strong, Anthony J.; Dreier, Jens P.; Dahlem, Yuliya A.; Sieber, Michaela; Hanke, Wolfgang; Podoll, Klaus; Schöll, Eckehard

2010-06-01

We present spatio-temporal characteristics of spreading depolarizations (SD) in two experimental systems: retracting SD wave segments observed with intrinsic optical signals in chicken retina, and spontaneously occurring re-entrant SD waves that repeatedly spread across gyrencephalic feline cortex observed by laser speckle flowmetry. A mathematical framework of reaction-diffusion systems with augmented transmission capabilities is developed to explain the emergence and transitions between these patterns. Our prediction is that the observed patterns are reaction-diffusion patterns controlled and modulated by weak nonlocal coupling such as long-range, time-delayed, and global coupling. The described spatio-temporal characteristics of SD are of important clinical relevance under conditions of migraine and stroke. In stroke, the emergence of re-entrant SD waves is believed to worsen outcome. In migraine, retracting SD wave segments cause neurological symptoms and transitions to stationary SD wave patterns may cause persistent symptoms without evidence from noninvasive imaging of infarction.

LES-based generation of high-frequency fluctuation in wind turbulence obtained by meteorological model

NASA Astrophysics Data System (ADS)

Tamura, Tetsuro; Kawaguchi, Masaharu; Kawai, Hidenori; Tao, Tao

2017-11-01

The connection between a meso-scale model and a micro-scale large eddy simulation (LES) is significant to simulate the micro-scale meteorological problem such as strong convective events due to the typhoon or the tornado using LES. In these problems the mean velocity profiles and the mean wind directions change with time according to the movement of the typhoons or tornadoes. Although, a fine grid micro-scale LES could not be connected to a coarse grid meso-scale WRF directly. In LES when the grid is suddenly refined at the interface of nested grids which is normal to the mean advection the resolved shear stresses decrease due to the interpolation errors and the delay of the generation of smaller scale turbulence that can be resolved on the finer mesh. For the estimation of wind gust disaster the peak wind acting on buildings and structures has to be correctly predicted. In the case of meteorological model the velocity fluctuations have a tendency of diffusive variation without the high frequency component due to the numerically filtering effects. In order to predict the peak value of wind velocity with good accuracy, this paper proposes a LES-based method for generating the higher frequency components of velocity and temperature fields obtained by meteorological model.

Transient-state mechanisms of wind-induced burrow ventilation.

PubMed

Turner, J Scott; Pinshow, Berry

2015-01-15

Burrows are common animal habitations, yet living in a burrow presents physiological challenges for its inhabitants because the burrow isolates them from sources and sinks for oxygen, carbon dioxide, water vapor and ammonia. Conventionally, the isolation is thought to be overcome by either diffusion gas exchange within the burrow or some means of capturing wind energy to power steady or quasi-steady bulk flows of air through it. Both are examples of what may be called 'DC' models, namely steady to quasi-steady flows powered by steady to quasi-steady winds. Natural winds, however, are neither steady nor quasi-steady, but are turbulent, with a considerable portion of the energy contained in so-called 'AC' (i.e. unsteady) components, where wind velocity varies chaotically and energy to power gas exchange is stored in some form. Existing DC models of burrow gas exchange do not account for this potentially significant source of energy for ventilation. We present evidence that at least two AC mechanisms operate to ventilate both single-opening burrows (of the Cape skink, Trachylepis capensis) and double-opening model burrows (of Sundevall's jird, Meriones crassus). We propose that consideration of the physiological ecology and evolution of the burrowing habit has been blinkered by the long neglect of AC ventilation. © 2015. Published by The Company of Biologists Ltd.

Data-driven RANS for simulations of large wind farms

NASA Astrophysics Data System (ADS)

Iungo, G. V.; Viola, F.; Ciri, U.; Rotea, M. A.; Leonardi, S.

2015-06-01

In the wind energy industry there is a growing need for real-time predictions of wind turbine wake flows in order to optimize power plant control and inhibit detrimental wake interactions. To this aim, a data-driven RANS approach is proposed in order to achieve very low computational costs and adequate accuracy through the data assimilation procedure. The RANS simulations are implemented with a classical Boussinesq hypothesis and a mixing length turbulence closure model, which is calibrated through the available data. High-fidelity LES simulations of a utility-scale wind turbine operating with different tip speed ratios are used as database. It is shown that the mixing length model for the RANS simulations can be calibrated accurately through the Reynolds stress of the axial and radial velocity components, and the gradient of the axial velocity in the radial direction. It is found that the mixing length is roughly invariant in the very near wake, then it increases linearly with the downstream distance in the diffusive region. The variation rate of the mixing length in the downstream direction is proposed as a criterion to detect the transition between near wake and transition region of a wind turbine wake. Finally, RANS simulations were performed with the calibrated mixing length model, and a good agreement with the LES simulations is observed.

Local ensemble transform Kalman filter for ionospheric data assimilation: Observation influence analysis during a geomagnetic storm event

NASA Astrophysics Data System (ADS)

Durazo, Juan A.; Kostelich, Eric J.; Mahalov, Alex

2017-09-01

We propose a targeted observation strategy, based on the influence matrix diagnostic, that optimally selects where additional observations may be placed to improve ionospheric forecasts. This strategy is applied in data assimilation observing system experiments, where synthetic electron density vertical profiles, which represent those of Constellation Observing System for Meteorology, Ionosphere, and Climate/Formosa satellite 3, are assimilated into the Thermosphere-Ionosphere-Electrodynamics General Circulation Model using the local ensemble transform Kalman filter during the 26 September 2011 geomagnetic storm. During each analysis step, the observation vector is augmented with five synthetic vertical profiles optimally placed to target electron density errors, using our targeted observation strategy. Forecast improvement due to assimilation of augmented vertical profiles is measured with the root-mean-square error (RMSE) of analyzed electron density, averaged over 600 km regions centered around the augmented vertical profile locations. Assimilating vertical profiles with targeted locations yields about 60%-80% reduction in electron density RMSE, compared to a 15% average reduction when assimilating randomly placed vertical profiles. Assimilating vertical profiles whose locations target the zonal component of neutral winds (Un) yields on average a 25% RMSE reduction in Un estimates, compared to a 2% average improvement obtained with randomly placed vertical profiles. These results demonstrate that our targeted strategy can improve data assimilation efforts during extreme events by detecting regions where additional observations would provide the largest benefit to the forecast.