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This article presents a study on the accuracy of the numerical determination of the friction and pressure resistance coefficients
of ship hulls. The investigation was carried out for the KVLCC2 tanker at model- and full-scale Reynolds numbers. Gravity
waves were neglected, i.e., we adopted the so-called double-model flow. Single-block grids with H–O topology were adopted
for all the calculations. Three eddy viscosity models were employed: the one-equation eddy viscosity and the two-equation
models proposed by Menter and the TNT version of the two-equation k-ω model. Verification exercises were performed in sets of nearly geometrically similar grids with different densities in the
streamwise, normal, and girthwise directions. The friction and pressure resistance coefficients were calculated for different
levels of the iterative error and for computational domains of different size. The results show that on the level of grid
refinement used, it is possible to calculate the viscous resistance coefficients in H–O grids that do not match the ship contour
with a numerical uncertainty of less than 1%. The differences between the predictions of different turbulence models were
larger than the numerical uncertainty; however, these differences tended to decrease with increases in the Reynolds number.
The pressure resistance was remarkably sensitive to domain size and far-field boundary conditions. Either a large domain or
the application of a viscous–inviscid interaction procedure is needed for reliable results.
This work was presented in part at the International Conference on Computational Methods in Marine Engineering—MARINE 2007,
Barcelona, June 3–4, 2007. 相似文献
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为把好锚杆的锚固质量关,开发简便、准确的无损检测方法是当务之急。介绍锚杆质量的无损检测原理、检测方法、检测分析与判断以及工程应用实例。 相似文献
56.
The alternatives to the oil based fuels for transportation are considered and analysed. These are the synthetic fuels, made from coal, the liquid petroleum gases of propane and butane, compressed natural gas and methanol. The problems associated with the use of electric vehicles are discussed; the main problem being that of range. The possible use of hydrogen as a fuel is analysed in some detail. Since its supply can be tied directly to nuclear energy sources, rather than hydrocarbon feed stocks, it could be an alternative in the long term. The main problems of the storage of hydrogen on the vehicle and of its propensity to “back‐fire” into the engine intake are discussed. The first can be ameliorated and the second eliminated by dual fuelling; with petrol. It is advocated that the on‐board storage of hydrogen be by the use of hydrides for private cars. However, it is expected that it may be as liquid hydrogen for some forms of transport and will certainly be in this form for aircraft. 相似文献
57.
Traffic assignment is usually determined solely on the basis of minimum travel time through the network. The present study on traffic assignment has taken into account not only traffic performance but also air quality over the street. A simple model of highway air pollution is developed by considering macroscopic material balance of polluted air mass over a segment of a highway that passes through an urban area, A new traffic assignment scheme has been developed based on the air pollution model. The optimal traffic assignment obtained by the new scheme is affected significantly by meteorological conditions. 相似文献
58.
Maren L. Outwater Greg Spitz John Lobb Margaret Campbell Bhargava Sana Ram Pendyala William Woodford 《Transportation》2011,38(4):605-623
This research seeks to improve the understanding of the full range of determinants for mode choice behavior and to offer practical
solutions to practitioners on representing and distinguishing these characteristics in travel demand forecasting models. The
principal findings were that the representation of awareness of transit services is significantly different than the underlying
assumption of mode choice and forecasting models that there is perfect awareness and consideration of all modes. Furthermore,
inclusion of non-traditional transit attributes and attitudes can improve mode choice models and reduce bias constants. Additional
methods and analyses are necessary to bring these results into practice. The work is being conducted in two phases. This paper
documents the results of Phase I, which included data collection for one case study city (Salt Lake City), research and analysis
of non-traditional transit attributes in mode choice models, awareness of transit services, and recommendations for bringing
these analyses into practice. Phase II will include data collection for two additional case study cities (Chicago and Charlotte)
with minor modifications based on limitations identified in Phase I, additional analyses where Phase I results indicated a
need, and a demonstration of the research in practice for at least one case study city. 相似文献
59.
Abstract Over the past few years an unusually intense struggle over the future of the Lake Michigan fishery has occurred in the coastal communities of Racine and Kenosha. This struggle has engaged participants on the local, state, and national levels in the debate over the fishery as it is potentially impacted by the presence of environmental toxins, the rising cost of fish stocking and management, and conflicting user group demands. We describe three cases where urban sports anglers, with the assistance of university based social scientists, participated in state and city public policy decisions. After discussing this research and its policy implications, we propose a general public participation paradigm termed the Reciprocal Development Model. 相似文献
60.
Sarah L. Richardson 《Coastal management》2013,41(1-2):21-46
Abstract Urban waterfronts are increasingly the focus of revitalization efforts designed to enhance tourism and recreation. The evolution of urban waterfronts suggests that these resources experience distinct stages of introduction, growth, maturity, decline, and sometimes revitalization. In this paper the product life cycle is broadened to describe the evolution of the waterfront district of Galveston, Texas. Implications of the product life cycle model of urban waterfront revitalization pertain to public policy formation, “product”; development, and management response to different life cycle stages. 相似文献