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Transportation - In the online published article, in figure 2 a value is missing in column 4. The correct figure is given in this correction. The original article has been corrected. 相似文献
3.
Transportation - Carpooling has potential as an alternative mode of school transportation along with other viable options, especially at a time when technology continues to increase our reliance... 相似文献
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A panel method is described for calculating potential flow around near-surface submarines. The method uses Havelock sources which automatically satisfy the linearized free-surface boundary condition. Outputs from the method include pressure field, pressure drag, wave resistance, vertical force, trim moment and wave pattern. Comparisons are made with model tests for wave resistance of Series 58 and DARPA SUBOFF hulls, as well as with wave resistance, lift force and trim moment of three length-to-diameter variants of the DSTO Joubert submarine hull. It is found that the Havelock source panel method is capable of determining with reasonable accuracy wave resistance, vertical force and trim moment for submarine hulls. Further experimental data are required in order to assess the accuracy of the method for pressure field and wave pattern prediction. The method is implemented in the computer code “HullWave” and offers potential advantages over RANS-CFD codes in terms of speed, simplicity and robustness. 相似文献
5.
The scale effect leads to large discrepancies between the wake fields of model-scale and actual ships, and causes differences in cavitation performance and exciting forces tests in predicting the performance of actual ships. Therefore, when test data from ship models are directly applied to predict the performance of actual ships, test results must be subjected to empirical corrections. This study proposes a method for the reverse design of the hull model. Compared to a geometrically similar hull model, the wake field generated by the modified model is closer to that of an actual ship. A non- geometrically similar model of a Korean Research Institute of Ship and Ocean Engineering (KRISO)’s container ship (KCS) was designed. Numerical simulations were performed using this model, and its results were compared with full-scale calculation results. The deformation method of getting the wake field of full-scale ships by the non-geometrically similar model is applied to the KCS successfully. 相似文献
6.
In this paper, vibration characteristics of the structure in the finite fluid domain are analyzed using a coupled finite element method. The added mass matrix is calculated with finite element method (FEM) by 8-node acoustic fluid elements. Vibration characteristics of the structure in finite fluid domain are calculated combining structure FEM mass matrix. By writing the relevant programs, numerical analysis on vibration characteristics of a submerged cantilever rectangular plate in finite fluid domain and loaded ship model is performed. A modal identification experiment for the loaded ship model in air and in water is conducted and the experiment results verify the reliability of the numerical analysis. The numerical method can be used for further research on vibration characteristics and acoustic radiation problems of the structure in the finite fluid domain. 相似文献
7.
To deal with the effect of compressible fluids on the supercavitating flow over the subsonic disk cavitator of a projectile, a finite volume method is formulated based on the ideal compressible potential theory. By using the continuity equation and Tait state equation as well as Riabouchinsky closure model, an “inverse problem” solution is presented for the supercavitating flow. According to the impenetrable condition on the surface of supercavity, a new iterative method for the supercavity shape is designed to deal with the effect of compressibility on the supercavity shape, pressure drag coefficient and density field. By this method, the very low cavitation number can be computed. The calculated results agree well with the experimental data and empirical formula. At the subsonic condition, the fluid compressibility will make supercavity length and radius increase. The supercavity expands, but remains spheroid. The effect on the first 1/3 part of supercavity is not obvious. The drag coefficient of projectile increases as the cavitation number or Mach number increases. With Mach number increasing, the compressibility is more and more significant. The compressibility must be considered as far as the accurate calculation of supercavitating flow is concerned. 相似文献
8.
There is much need for autonomous underwater vehicles (AUVs) for inspection and mapping purposes. Most conventional AUVs use torpedo-shaped single-rigid hull, b... 相似文献
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The effects of the temperature, salinity, and fluid type on the acoustic characteristics of turbulent flow around a circular cylinder were numerically investiga... 相似文献
10.
In contrast with reviews of values of time and price elasticities, the literature contains little by way of detailed reviews
of travel time based choice and demand elasticities. This paper reports the most extensive meta-analysis of time-based demand
elasticities yet undertaken, supplemented with a review of literature not previously in the public domain. The meta-analysis
is based upon 427 direct elasticities covering travel time, generalised journey time (GJT) and service headway and drawn from
69 UK studies. The elasticities are found to vary, as expected, across attributes, and quite strong effects have been detected
according to distance. We provide interesting insights into the relationship between long and short run elasticities and elasticities
obtained from static models and choice models based on actual and hypothetical preferences. Significantly, the results seem
to indicate that the duration for the long run demand impact to work through depends upon the periodicity of the model estimated.
There is little variation apparent by journey purpose, source of the evidence, nor over time or by region/flow type, whilst
travel time elasticities for high speed rail are not materially different from conventional contexts. The findings support
some official elasticity recommendations and conventions but challenge others, and can be used to provide time-based elasticities
where none exist or to assess new empirical evidence. 相似文献