The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Patrick Lonergan - One of the best experts on this subject based on the ideXlab platform.

  • could high speed Civil Transport Aircraft impact stratospheric and tropospheric temperatures measured by microwave sounding unit
    Journal of Geophysical Research, 1996
    Co-Authors: Kathryn Pierce Shah, David Rind, Patrick Lonergan
    Abstract:

    A radiative transfer postprocessor calculates microwave brightness temperatures Tb from climate experiments investigating supersonic Aircraft exhaust impacts with the Global Climate/Middle Atmosphere Model (GCMAM) at the NASA Goddard Institute for Space Studies. Microwave signals from the exhaust-perturbed GCMAM atmospheres are contrasted with observed interannual variability (natural “noise”) for 1982–1991 as measured by microwave sounding unit (MSU) channels across the lower troposphere, midtroposphere, and lower stratosphere. Exaggerated ozone and water vapor perturbations at supersonic cruise altitudes produce microwave signals easily detected against natural noise. Removal of ozone greenhouse action between 200 and 50 hPa cools all MSU channels with greatest Δ Tb of −8.3 K and signal-to-observed-noise (S/N) ratios above 20 in the lower stratospheric channel. Doubling middle-atmospheric water vapor above 100 hPa cools lower stratospheric Tb values by 1.5 K while warming tropospheric channels, particularly the tropopause channel. Detectable S/N ratios of 2–4 occur over the tropics and subtropics in the lower-to-middle troposphere and lower stratosphere. Realistic ozone and water vapor perturbations are based on the High-Speed Research Program/Atmospheric Effects of Stratospheric Aircraft reports. These realistic stratospheric ozone and water vapor changes produce Δ Tb signals under 0.6 K and negligible S/N ratios. The slight climatic forcings are overwhelmed by natural feedbacks of high and low cloud formation, sea ice formation, and snow coverage. Thus the modeled realistic ozone and water vapor perturbations produce small and conflicting microwave signals, undetectable against natural variability and other sources of anthropogenic climatic forcing.

  • modeled impacts of stratospheric ozone and water vapor perturbations with implications for high speed Civil Transport Aircraft
    Journal of Geophysical Research, 1995
    Co-Authors: David Rind, Patrick Lonergan
    Abstract:

    Ozone and water vapor perturbations are explored in a series of experiments with the Goddard Institute for Space Studies climate/middle atmosphere model. Large perturbations, and realistic perturbations, to stratospheric ozone and water vapor are investigated, with and without allowing sea surface temperatures to change, to illuminate the nature of the dynamic and climatic impact. Removing ozone in the lower stratosphere without allowing sea surface temperatures to change results in in situ cooling of up to 10{degrees}C in the tropical lower stratosphere, with radiative warming about half as large in the middle stratosphere. The temperature changes induce increases in tropospheric and lower stratospheric eddy energy and in the lower stratosphere residual circulation of the order of 10%. When sea surface temperatures are allowed to respond to this forcing, the global, annual-average surface air temperature cools by about 1{degrees}C as a result of the decreased ozone greenhouse capacity, reduced tropospheric water vapor, and increased cloud cover. For more realistic ozone changes, as defined in the High-Speed Research Program/Atmospheric Effects of Stratospheric Aircraft reports, the stratosphere generally cools by a few tenths degrees Celsius. In this case, the surface air temperature change is not significant, due to the conflicting influences of stratospheric ozonemore » reduction and tropospheric ozone increase, although high-latitude cooling of close to 0.5{degrees}C does occur consistently. With a more realistic increase of stratospheric water vapor of 7%, the middle atmosphere cools by 0.5{degrees}C or less, and the surface temperature change is neither significant nor consistent. Overall, the experiments emphasize that stratospheric changes affect tropospheric dynamics, and that tropospheric feedback processes and natural variability are important when assessing the climatic response to Aircraft emissions. 21 refs., 20 figs., 3 tabs.« less

Daniel P Schrage - One of the best experts on this subject based on the ideXlab platform.

  • a multilevel decomposition procedure for the preliminary wing design of a high speed Civil Transport Aircraft
    1994
    Co-Authors: Peter J Rohl, Dimitri N. Mavris, Daniel P Schrage
    Abstract:

    Presented at the 1st Industry/Acedemy Symposium on Research for Future Supersonic and Hypersonic Vehicles, Greensboro, NC, December 4-6, 1994.

  • preliminary wing design of a high speed Civil Transport Aircraft by multilevel decomposition techniques
    4th Symposium on Multidisciplinary Analysis and Optimization, 1992
    Co-Authors: Peter J Rohl, Daniel P Schrage
    Abstract:

    A multilevel decomposition approach for the preliminary design of a High Speed Civil Transport (HSCT) Aircraft wing structure is described. The wing design is decomposed into three levels. The top level uses the ACSYNT Aircraft synthesis program to generate preliminary weight, mission and performance information needed for the calculations. The optimization criterion is productivity as expressed by a productivity index for a specified mission. The second level of the system performs a basic finite element structural analysis of the wing box. The wing structure is sized for minimum weight subject to structural and aeroelastic constraints. Sensitivity derivatives are computed with respect to the top level design variables. Level 3 performs a detailed stress and buckling analysis of the wing skin panels and thus creates an updated wing weight that is passed to the top level together with the sensitivity information. The methodology will be verified using a baseline HSCT configuration derived from the NASA HiSAIR studies. Currently data acquisition and computer program installation are in progress.

William Crowther - One of the best experts on this subject based on the ideXlab platform.

  • Systems and certification issues for Civil Transport Aircraft flow control systems
    The Aeronautical Journal, 2009
    Co-Authors: S. C. Liddle, Mark Jabbal, William Crowther
    Abstract:

    The use of flow control (FC) technology on Civil Transport Aircraft is seen as a potential means of providing a step change in aerodynamic performance in the 2020 time frame. There has been extensive research into the flow physics associated with FC. This paper focuses on developing an understanding of the costs and design drivers associated with the systems needed and certification. The research method adopted is based on three research strands: 1. Study of the historical development of other disruptive technologies for Civil Transport Aircraft, 2. Analysis of the impact of legal and commercial requirements, and 3. Technological foresight based on technology trends for Aircraft currently under development. Fly by wire and composite materials are identified as two historical examples of successful implementation of disruptive new technology. Both took decades to develop, and were initially developed for military markets. The most widely studied technology similar to FC is identified as laminar flow control. Despite more than six decades of research and arguably successful operational demonstration in the 1990s this has not been successfizlly transitioned to commercial products. Significant future challenges are identified in cost effective provision of the additional systems required for environmental protection and in service monitoring of FC systems particularly where multiple distributed actuators are envisaged. FC generated noise is also seen as a significant challenge. Additional complexity introduced by FC systems must also be balanced by the commercial imperative of dispatch reliability, which may impose more stringent constraints than legal (certification) requirements. It is proposed that a key driver for future successful application of FC is the likely availability of significant electrical power generation on 787 Aircraft forwards. This increases the competitiveness of electrically driven FC systems compared with those using engine bleed air. At the current rate of progress it is unlikely FC will make a contribution to the next generation of single-aisle Aircraft due to enter service in 2015. In the longer term, there needs to be significant movement across a broad range of systems technologies before the aerodynamic benefits ofFC can be exploited.

  • an evaluation of the mass and power scaling of synthetic jet actuator flow control technology for Civil Transport Aircraft applications
    Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering, 2008
    Co-Authors: William Crowther, Luis Teia Gomes
    Abstract:

    This paper aims to develop understanding of the systems costs associated with the application of flow control systems to Civil Transport Aircraft based on the use of electrically powered synthetic jet actuators (SJAs). The study is based on the development of a low-order mass model using estimated power specific masses of generation, management, distribution, and conversion subsystems; application of existing empirical rules for application of pneumatic boundary layer mixing flow control devices to determine the required fluid power for an A320 case study application; and characterization and optimization of lab-based SJA technology to establish realistic estimates for power conversion efficiency and actuator maximum authority. The peak velocity obtained from a velocity-optimized synthetic jet actuator was 130 m/s, at a corresponding power efficiency of 7 per cent. The highest power efficiency obtained was 14 per cent, corresponding to a peak velocity of 70 m/s. The power specific mass for the overall flo...

  • systems and certification issues for Civil Transport Aircraft flow control systems
    In: 46th AIAA Aerospace Sciences Meeting and Exhibit Reno AIAA-2008-158: 46th AIAA Aerospace Sciences Meeting and Exhibit Reno AIAA-2008-158; 2008., 2008
    Co-Authors: S. C. Liddle, William Crowther
    Abstract:

    This article is placed here with permission from the Royal Aeronautical Society - Copyright @ 2009 Royal Aeronautical Society

Nikolaos Kehayas - One of the best experts on this subject based on the ideXlab platform.

  • propulsion system of jet flapped subsonic Civil Transport Aircraft design
    Journal of Aircraft, 2011
    Co-Authors: Nikolaos Kehayas
    Abstract:

    DESIGN FORUM papers range from design case studies to presentations of new methodologies to speculations about emerging design trends. They vary from 2500 to 12,000 words (where a figure or table counts as 200 words). Following informal review by the Editors, they may be published within a few months of the date of receipt. Style requirements are the same as for regular contributions (see inside back cover).

  • aeronautical technology for future subsonic Civil Transport Aircraft
    Aircraft Engineering and Aerospace Technology, 2007
    Co-Authors: Nikolaos Kehayas
    Abstract:

    Purpose – A review is attempted with the objective to indicate the most promising aeronautical technology for application to future subsonic Civil Transport Aircraft.Design/methodology/approach – A methodology is put forward, according to which direct operating costs (DOC) are examined in order to identify those that can be reduced, and, then, specific technology is assessed in relation to its efficiency in reducing these DOC, operational feasibility and cost‐effectiveness.Findings – This assessment suggests the selection of propfan and powered lift as the leading future aeronautical technology. These findings are supported by a comparison of a number of advanced technology designs.Originality/value – Provides a starting point for further investigation of advanced aeronautical technology and unconventional configurations for large subsonic Civil Transport Aircraft.

David Rind - One of the best experts on this subject based on the ideXlab platform.

  • could high speed Civil Transport Aircraft impact stratospheric and tropospheric temperatures measured by microwave sounding unit
    Journal of Geophysical Research, 1996
    Co-Authors: Kathryn Pierce Shah, David Rind, Patrick Lonergan
    Abstract:

    A radiative transfer postprocessor calculates microwave brightness temperatures Tb from climate experiments investigating supersonic Aircraft exhaust impacts with the Global Climate/Middle Atmosphere Model (GCMAM) at the NASA Goddard Institute for Space Studies. Microwave signals from the exhaust-perturbed GCMAM atmospheres are contrasted with observed interannual variability (natural “noise”) for 1982–1991 as measured by microwave sounding unit (MSU) channels across the lower troposphere, midtroposphere, and lower stratosphere. Exaggerated ozone and water vapor perturbations at supersonic cruise altitudes produce microwave signals easily detected against natural noise. Removal of ozone greenhouse action between 200 and 50 hPa cools all MSU channels with greatest Δ Tb of −8.3 K and signal-to-observed-noise (S/N) ratios above 20 in the lower stratospheric channel. Doubling middle-atmospheric water vapor above 100 hPa cools lower stratospheric Tb values by 1.5 K while warming tropospheric channels, particularly the tropopause channel. Detectable S/N ratios of 2–4 occur over the tropics and subtropics in the lower-to-middle troposphere and lower stratosphere. Realistic ozone and water vapor perturbations are based on the High-Speed Research Program/Atmospheric Effects of Stratospheric Aircraft reports. These realistic stratospheric ozone and water vapor changes produce Δ Tb signals under 0.6 K and negligible S/N ratios. The slight climatic forcings are overwhelmed by natural feedbacks of high and low cloud formation, sea ice formation, and snow coverage. Thus the modeled realistic ozone and water vapor perturbations produce small and conflicting microwave signals, undetectable against natural variability and other sources of anthropogenic climatic forcing.

  • modeled impacts of stratospheric ozone and water vapor perturbations with implications for high speed Civil Transport Aircraft
    Journal of Geophysical Research, 1995
    Co-Authors: David Rind, Patrick Lonergan
    Abstract:

    Ozone and water vapor perturbations are explored in a series of experiments with the Goddard Institute for Space Studies climate/middle atmosphere model. Large perturbations, and realistic perturbations, to stratospheric ozone and water vapor are investigated, with and without allowing sea surface temperatures to change, to illuminate the nature of the dynamic and climatic impact. Removing ozone in the lower stratosphere without allowing sea surface temperatures to change results in in situ cooling of up to 10{degrees}C in the tropical lower stratosphere, with radiative warming about half as large in the middle stratosphere. The temperature changes induce increases in tropospheric and lower stratospheric eddy energy and in the lower stratosphere residual circulation of the order of 10%. When sea surface temperatures are allowed to respond to this forcing, the global, annual-average surface air temperature cools by about 1{degrees}C as a result of the decreased ozone greenhouse capacity, reduced tropospheric water vapor, and increased cloud cover. For more realistic ozone changes, as defined in the High-Speed Research Program/Atmospheric Effects of Stratospheric Aircraft reports, the stratosphere generally cools by a few tenths degrees Celsius. In this case, the surface air temperature change is not significant, due to the conflicting influences of stratospheric ozonemore » reduction and tropospheric ozone increase, although high-latitude cooling of close to 0.5{degrees}C does occur consistently. With a more realistic increase of stratospheric water vapor of 7%, the middle atmosphere cools by 0.5{degrees}C or less, and the surface temperature change is neither significant nor consistent. Overall, the experiments emphasize that stratospheric changes affect tropospheric dynamics, and that tropospheric feedback processes and natural variability are important when assessing the climatic response to Aircraft emissions. 21 refs., 20 figs., 3 tabs.« less