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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

GCM Simulation of the Large-scale North American Monsoon Including Water Vapor Tracer Diagnostics

The geographic sources of water for the large-scale North American monsoon in a GCM are diagnosed using passive constituent tracers of regional water'sources (Water Vapor Tracers, WVT). The NASA Data Assimilation Office Finite Volume (FV) GCM was used to produce a 10-year simulation (1984 through 1993) including observed sea surface temperature. Regional and global WVT sources were defined to delineate the surface origin of water for precipitation in and around the North American i'vionsoon. The evolution of the mean annual cycle and the interannual variations of the monsoonal circulation will be discussed. Of special concern are the relative contributions of the local source (precipitation recycling) and remote sources of water vapor to the annual cycle and the interannual variation of warm season precipitation. The relationships between soil water, surface evaporation, precipitation and precipitation recycling will be evaluated.

Bosilovich, Michael G.↗
NASA NTRS2007

A Revised Method of Presenting Wavenumber-Frequency Power Spectrum Diagrams That Reveals the Asymmetric Nature of Tropical Large-scale Waves

The popular method of presenting wavenumber-frequency power spectrum diagrams for studying tropical large-scale waves in the literature is shown to give an incomplete presentation of these waves. The so-called "convectively-coupled Kelvin (mixed Rossby-gravity) waves" are presented as existing only in the symmetric (antisymmetric) component of the diagrams. This is obviously not consistent with the published composite/regression studies of "convectively-coupled Kelvin waves," which illustrate the asymmetric nature of these waves. The cause of this inconsistency is revealed in this note and a revised method of presenting the power spectrum diagrams is proposed. When this revised method is used, "convectively-coupled Kelvin waves" do show anti-symmetric components, and "convectively-coupled mixed Rossby-gravity waves (also known as Yanai waves)" do show a hint of symmetric components. These results bolster a published proposal that these waves be called "chimeric Kelvin waves," "chimeric mixed Rossby-gravity waves," etc. This revised method of presenting power spectrum diagrams offers a more rigorous means of comparing the General Circulation Models (GCM) output with observations by calling attention to the capability of GCMs in correctly simulating the asymmetric characteristics of the equatorial waves.

Chao, Winston C.↗
NASA NTRS2017

Cost-Driven Design of a Large Scale X-Plane

A conceptual design process focused on the development of a low-cost, large scale X-plane was developed as part of an internal research and development effort. One of the concepts considered for this process was the double-bubble configuration recently developed as an advanced single-aisle class commercial transport similar in size to a Boeing 737-800 or Airbus A320. The study objective was to reduce the contractor cost from contract award to first test flight to less than $100 million, and having the first flight within three years of contract award. Methods and strategies for reduced cost are discussed.

Welstead, Jason R.↗
NASA NTRS1987

Rossby waves and two-dimensional turbulence in a large-scale zonal jet

Homogeneous barotropic beta-plane turbulence is investigated, taking into account the effects of spatial inhomogeneity in the form of a zonal shear flows. Attention is given to the case of zonal flows that are barotropically stable and of larger scale than the resulting transient eddy field. Numerical simulations reveal that large-scale zonal flows alter the picture of classical beta-plane turbulence. It is found that the disturbance field penetrates to the largest scales of motion, that the larger disturbance scales show a tendency to meridional rather than zonal anisotropy, and that the initial spectral transfer rate away from an isotropic intermediate-scale source is enhanced by the shear-induced transfer associated with straining by the zonal flow.

Shepherd, Theodor G.↗
NASA NTRS1958

Aerodynamic Characteristics in Sideslip of a Large-Scale 49 deg Sweptback Wing-Body-Tail Configuration with Blowing Applied Over the Flaps and Wing Leading Edge

An investigation has been conducted in the Langley full-scale tunnel to determine the aerodynamic characteristics in sideslip of a large-scale 490 sweptback wing-body-tail configuration having wing leading- edge and flap-blowing boundary-layer control. The wing and tails had an aspect ratio of 3.5, a taper ratio of 0.3, and NACA 65AO06 airfoil sections parallel to the plane of symmetry. The tests were conducted over a range of angles of attack of about -5 deg to 28 deg for sideslip angles of 0 deg, -5.06 deg, -10.15 deg, and -15.18 deg. Lateral and longitudinal stability and control characteristics were obtained for6a minimized blowing rate. The Reynolds number of the tests was 5.2 x 10(exp 6), corresponding to a Mach number of 0.08. The results of the investigation showed that sideslip to angles of about -15 deg did not require, from a consideration of the longitudinal characteristics, blowing rates over the wing leading edge or flap greater than that established as minimum at zero sideslip. The optimum configuration was laterally and directionally stable through the complete lift-coefficient range including the stall; however, maximum lift for sideslip angles greater than about 50 was seriously limited by a deficiency of lateral control. Blowing over the leading edge of the retreating wing in sideslip at a rate greater than that established as minimum at zero sideslip was ineffective in improving the lateral control characteristics. The optimum configuration at zero sideslip had no hysteresis of the aerodynamic parameters upon recovery from stall.

McLemore, H. Clyde↗
NASA NTRS1976

Implementation of Large Scale Integrated (LSI) circuit design software

Portions of the Computer Aided Design and Test system, a collection of Large Scale Integrated (LSI) circuit design programs were modified and upgraded. Major modifications were made to the Mask Analysis Program in the form of additional operating commands and file processing options. Modifications were also made to the Artwork Interactive Design System to correct some deficiencies in the original program as well as to add several new command features related to improving the response of AIDS when dealing with large files. The remaining work was concerned with updating various programs within CADAT to incorporate the silicon on sapphire silicon gate technology.

Kuehlthau, R. L.↗
NASA NTRS1994

Engineering large-scale agent-based systems with consensus

The paper presents the consensus method for the development of large-scale agent-based systems. Systems can be developed as networks of knowledge based agents (KBA) which engage in a collaborative problem solving effort. The method provides a comprehensive and integrated approach to the development of this type of system. This includes a systematic analysis of user requirements as well as a structured approach to generating a system design which exhibits the desired functionality. There is a direct correspondence between system requirements and design components. The benefits of this approach are that requirements are traceable into design components and code thus facilitating verification. The use of the consensus method with two major test applications showed it to be successful and also provided valuable insight into problems typically associated with the development of large systems.

Bokma, A.↗
NASA NTRS2022

Turbulent Heat Flux, Downward Longwave Radiation and Large-Scale Atmospheric Circulation Associated with the Wintertime Barents-Kara Sea Extreme Sea Ice Loss Events

We investigate wintertime extreme sea ice loss events on synoptic to subseasonal time scales over the Barents-Kara Sea, where the largest sea ice variability is located. Consistent with previous studies, extreme sea ice loss events are associated with moisture intrusions over the Barents-Kara Sea, which are driven by the large-scale atmospheric circulation. In addition to the role of downward longwave radiation associated with moisture intrusions, which is emphasized by previous studies, our analysis shows strong turbulent heat fluxes are associated with extreme sea ice melting events, with both turbulent sensible and latent heat fluxes contributing, though turbulent sensible heat fluxes dominate. Our analysis also shows that these events are connected to tropical convective anomalies. A dipole pattern of convective anomalies with enhanced convection over the Maritime Continent and suppressed convection over the central to eastern Pacific is consistently detected about 6 to 10 days prior to extreme sea ice loss events. This pattern is associated with either the Madden-Julian Oscillation (MJO) or El Niño–Southern Oscillation (ENSO). Composites show that extreme sea ice loss events are connected to tropical convection via Rossby wave propagation in the midlatitudes. However, tropical convective anomalies alone are not sufficient to trigger extreme sea ice loss events, suggesting that extratropical variability likely modulates the connection between tropical convection and extreme sea ice loss events.

Turbulent heat flux↗
NASA NTRS1972

Stability regions of large-scale systems.

Using an aggregated comparison system, methods are developed for estimating regions of asymptotic stability for large-scale systems composed of interconnected, exponentially stable subsystems; in general some of these subsystems are not globally stable. Three different forms of Liapunov functions are shown to be suitable for describing the stability behavior of the aggregated system, but one form in particular (heretofore not used in this context) is found to be the most natural. Using this function, some general results are obtained.

Weissenberger, S.↗
NASA NTRS1972

Stability of large-scale systems.

The purpose of this paper is to present the results obtained in stability study of large-scale systems based upon the comparison principle and vector Liapunov functions. The exposition is essentially self-contained, with emphasis on recent innovations which utilize explicit information about the system structure. This provides a natural foundation for the stability theory of dynamic systems under structural perturbations.

Siljak, D. D.↗
NASA NTRS1973

Stability regions of large-scale systems

Using an aggregated comparison system, methods are developed for estimating regions of asymptotic stability for large-scale systems composed of interconnected, exponentially stable subsystems; in general, some of these subsystems are not globally stable. Three different forms of Liapunov functions are shown to be suitable for describing the stability behavior of the aggregated system, but one form in particular, heretofore not used in this context, is found to be the most natural. Using this function, some general results are obtained.

Weissenberger, S.↗
NASA NTRS1977

Comparison of H alpha synoptic charts with the large-scale solar magnetic field as observed at Stanford

Two methods of observing the neutral line of the large-scale photospheric magnetic field are compared: (1) neutral line positions inferred from H alpha photographs and (2) observations of the photospheric magnetic field made with low spatial resolution (3 arc min.) and high sensitivity using the Stanford magnetograph. The comparison is found to be very favorable.

Duvall, T. L., Jr.↗
NASA NTRS1977

Comparison of H-alpha synoptic charts with the large-scale solar magnetic field as observed at Stanford

Two methods of observing the neutral line of the large-scale photospheric magnetic field are compared: neutral line positions inferred from H-alpha photographs (McIntosh and Nolte, 1975) and observations of the photospheric magnetic field made with low spatial resolution (three minutes) and high sensitivity using the Stanford magnetograph. The comparison is found to be very favorable.

Duvall, T. L., Jr.↗
NASA NTRS1988

The topology of large-scale structure. II - Nonlinear evolution of Gaussian models

The evolution of non-Gaussian behavior in the large-scale universe from Gaussian initial conditions is studied. Topology measures developed in previous papers are applied to the smoothed initial, final, and biased matter distributions of cold dark matter, white noise, and massive neutrino simulations. When the smoothing length is approximately twice the mass correlation length or larger, the evolved models look like the initial conditions, suggesting that random phase hypotheses in cosmology can be tested with adequate data sets. When a smaller smoothing length is used, nonlinear effects are recovered, so nonlinear effects on topology can be detected in redshift surveys after smoothing at the mean intergalaxy separation. Hot dark matter models develop manifestly non-Gaussian behavior attributable to phase correlations, with a topology reminiscent of bubble or sheet distributions. Cold dark matter models remain Gaussian, and biasing does not disguise this.

Melott, Adrian L.↗
NASA NTRS1989

Grid sensitivity capability for large scale structures

The considerations and the resultant approach used to implement design sensitivity capability for grids into a large scale, general purpose finite element system (MSC/NASTRAN) are presented. The design variables are grid perturbations with a rather general linking capability. Moreover, shape and sizing variables may be linked together. The design is general enough to facilitate geometric modeling techniques for generating design variable linking schemes in an easy and straightforward manner. Test cases have been run and validated by comparison with the overall finite difference method. The linking of a design sensitivity capability for shape variables in MSC/NASTRAN with an optimizer would give designers a powerful, automated tool to carry out practical optimization design of real life, complicated structures.

Nagendra, Gopal K.↗