12,238 research outputs found
Aeronautical Engineering: A special bibliography with indexes, supplement 67, February 1976
This bibliography lists 341 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1976
Aeronautical Engineering. A continuing bibliography, supplement 115
This bibliography lists 273 reports, articles, and other documents introduced into the NASA scientific and technical information system in October 1979
Stochastic method for in-situ damage analysis
Based on the physics of stochastic processes we present a new approach for
structural health monitoring. We show that the new method allows for an in-situ
analysis of the elastic features of a mechanical structure even for realistic
excitations with correlated noise as it appears in real-world situations. In
particular an experimental set-up of undamaged and damaged beam structures was
exposed to a noisy excitation under turbulent wind conditions. The method of
reconstructing stochastic equations from measured data has been extended to
realistic noisy excitations like those given here. In our analysis the
deterministic part is separated from the stochastic dynamics of the system and
we show that the slope of the deterministic part, which is linked to mechanical
features of the material, changes sensitively with increasing damage. The
results are more significant than corresponding changes in eigenfrequencies, as
commonly used for structural health monitoring.Comment: This paper is accepted by European Physical Journal B on November 2.
2012. 5 pages, 5 figures, 1 tabl
A Wiener-Laguerre model of VIV forces given recent cylinder velocities
Slender structures immersed in a cross flow can experience vibrations induced
by vortex shedding (VIV), which cause fatigue damage and other problems. VIV
models in engineering use today tend to operate in the frequency domain. A time
domain model would allow to capture the chaotic nature of VIV and to model
interactions with other loads and non-linearities. Such a model was developed
in the present work: for each cross section, recent velocity history is
compressed using Laguerre polynomials. The compressed information is used to
enter an interpolation function to predict the instantaneous force, allowing to
step the dynamic analysis. An offshore riser was modeled in this way: Some
analyses provided an unusually fine level of realism, while in other analyses,
the riser fell into an unphysical pattern of vibration. It is concluded that
the concept is promissing, yet that more work is needed to understand orbit
stability and related issues, in order to further progress towards an
engineering tool
Aeronautical Engineering: A continuing bibliography, supplement 120
This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980
Concept design of a fast sail assisted feeder container ship
A fast sail assisted feeder container ship concept has been developed for the 2020 container market in the South East Asian and Caribbean regions.The design presented has met the requirements of an initial economic study, with a cargo capacity of 1270 twenty-foot equivalent unit containers, meeting the predictions of container throughput derived from historical data. In determining suitable vessel dimensions, account has also been taken for port and berthing restrictions, and considering hydrodynamic performance. The vessel has been designed for a maximum speed of 25 knots, allowing it to meet the demand for trade whilst reducing the number of ships operating on the routes considered.The design development of the fast feeder concept has involved rigorous analyses in a number of areas to improve the robustness of the final design. Model testing has been key to the development of the concept, by increasing confidence in the final result. This is due to the fact that other analysis techniques are not always appropriate or accurate. Two hull forms have been developed to meet requirements whilst utilising different propulsor combinations. This has enabled evaluation of efficiency gains resulting from different hydrodynamic phenomena for each design. This includes an evaluation of the hydrodynamic performance when utilising the sail system. This has been done using a combination of model test results and data from regression analysis. The final propulsor chosen is a contra-rotating podded drive arrangement. Wind tunnel testing has been used to maximise the performance of a Multi-wing sail system by investigating the effects of wing spacing, stagger and sail-container interactions. This has led to an increase in lift coefficient of 32% from initial predictions. The savings in power requirement due to the sail system are lower than initially predicted. However, another benefit of their installation, motion damping, has been identified. Whilst this has not been fully investigated, additional fuel savings are possible as well as improved seakeeping performance.The design is shown to be environmentally sustainable when compared to existing vessels operating on the proposed routes. This is largely due to the use of low-carbon and zero-sulphur fuel (liquefied natural gas) and improvements in efficiency regarding operation. This especially relates to cargo handling and scheduling. Green house gas emissions have been predicted to fall by 42% and 40% in the two regions should the design be adopted. These savings are also due to the use of the Multi-wing sail system, which contributes to reductions in power requirement of up to 6% when the vessel operates at its lower speed of 15 knots. It is demonstrated that the fast feeder is also economically feasible, with predicted daily cost savings of 27% and 33% in the South East Asian and Caribbean regions respectively. Thus the fast feeder container ship concept is a viable solution for the future of container transhipment. <br/
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