运用车辆动态模拟装置提高东海道新干线列车的乘坐舒适性

介绍了车辆动态模拟装置在评价车辆乘坐舒适性方面的应用情况,并阐述了车辆动态模拟装置在车辆部件研发过程中的重要作用.     

Merging bus routes in Hong Kong’s central business district: Analysis and models

A significant portion of the 200,000 people working in Hong Kong’s central business district (CBD) relies on buses as their primary means of transport. During peak hours, nearly a thousand double-decker buses pour into a tiny area of 150 ha. This causes traffic congestion and air pollution. Moreover, given that the flow is uni-directional (into the CBD in the morning and out of the CBD in the afternoon), the occupancy of buses in the CBD is actually low.In this paper, we propose to reduce traffic congestion and to increase bus occupancy by merging bus routes. We describe the peculiar situation of the CBD in Hong Kong and explain the necessary conditions for the possible success of merging routes. Our analysis shows that merging will lead to an overall benefit for all parties, including government, bus operators, and passengers. The actual merging decisions, which routes to merge and at what frequencies buses should run, are determined by a mathematical model. The model also shows quantitatively the benefits of merging routes and the impacts of other factors. The procedure that we follow and the model that we adopt can be applied to other CBD.     

复杂山区地形桥址区风特性的数值模拟

为了研究复杂山区地形桥址区风场空间特性变化规律,以位于我国西南山区的绿汁江大桥为工程背景,利用FLUENT对山区地形风场特性进行数值模拟,通过36个风向工况的计算分析,得到复杂山区地形桥址区风场的空间分布特性. 结果表明:受复杂地形影响,各桥位平均风速风剖面曲线和沿主梁横桥向风速曲线差异较大,桥址区附近地形最高点以上400 m风场仍明显受地形影响;受河道大角度弯曲影响,桥址区形成类似“单向开口槽”的地形,顺河流风向的来流风受山体阻挡,各桥位处的风速低于逆河流风向,两个风向的风速差值的平均值达13.6 m/s,且各桥位风攻角以负攻角为主;峡谷突宽使谷内风场出现一定的分流,突宽区风速稍有减弱,风场的分流量有限,使得在渡过突宽段后的峡谷缩窄区,风速依旧较大.      

Numerical prediction of the dilution process and its biological impacts in CO2 ocean sequestration

 In order to investigate the biological impacts of the ocean sequestration of CO₂ (carbon dioxide), the dilution processes of CO₂ were investigated near injection points in the deep ocean. From a combined fluid-dynamics, chemical, and biological approach, a two-phase computational fluid dynamics (CFD) method with mass transfer was developed to predict droplet plume flow, the dissolution of CO₂ from droplets into seawater, and the advection–diffusion of dissolved CO₂ (DCO₂) in the deep ocean. Changes in pH due to the concentration of DCO₂ were also calculated. In addition, the isomortality concept of Auerbach et al. was incorporated to predict the lethal damage to marine organisms caused by DCO₂. The simulation results suggested that the biological impacts of CO₂ sequestration were insignificant in terms of mortality in both small-scale field experiments and the real-life cases we propose. Received: October 3, 2001 / Accepted: December 14, 2001     

A study on bubble plume behavior in stratified water

Plumes of air and carbon-dioxide (CO₂) bubbles in stratified water were studied experimentally and numerically. It is important to understand the plume behavior of droplets or bubbles in the ocean in marine environmental engineering. In sequestration of CO₂ in the ocean, liquid CO₂ is injected in the form of droplets, and thermal stratification in enclosed seas is possibly destroyed by a bubble generator. This study focuses on the relationship between intrusion depth and stratification intensity, gas flow rate, and bubble size. A desktop-sized tank was used to achieve no-background-flow conditions for salt stratification. The results from the air-bubble experiments indicated that the larger the bubble size, the smaller the intrusion depth. We also observed the behavior of CO₂ bubbles. They are different from air in that they dissolve in water and are reduced in volume. Our numerical simulation method for two-phase flow was validated by comparisons with the experiments. Received: August 13, 2001 / Accepted: October 9, 2001     

High-resolution synthetic monitoring by a 4-dimensional variational data assimilation system in the northwestern North Pacific

A data assimilation system is applied to the integrated monitoring of oceanic states in the northwestern North Pacific by combining a high resolution ocean general circulation model with an adjoint method. A comparison of assimilation results with observations shows that the system is better able to represent synoptic features of ocean circulation than do models or data alone. Furthermore, meso-scale features associated with frontal structures and eddies, which are often seen in the Kuroshio and Oyashio extension regions and the Sea of Japan, are better defined in the assimilation results. These features suggest that our 4D-VAR high-resolution data assimilation system is capable of providing time series data which satisfy the model physics and fit the observations, and hence the ocean state derived from our system has greater information content than that obtained from earlier methods.     

Test of large-eddy simulation models for homogeneous-shear turbulence in stratification

Numerical tests of various subgrid-scale (SGS) models were conducted for turbulence in thermally stratified homogeneous-shear flow at a relatively low Reynolds number. Compared with a direct numerical simulation (DNS), we found that nondynamic isotropic SGS models are not able to represent the energy spectrum very well because the energy decays considerably during the transition between an initial random stage and a stage of coherent turbulent structures. Dynamic models performed well for simulating the energy spectrum and the change of GS properties with time; anisotropy is not a necessary feature under the present simulation conditions, although one of the special features of stratified turbulence is anisotropy. This may be because the present grids for large-eddy simulation were fine enough to resolve the patches of counter-gradient heat fluxes, which play an important role in the evolution of turbulent energy in stratified turbulence. With respect to the domain-averaged values of SGS stresses, only the dynamic two-parameter mixed (DTM) model produced results of the same order of magnitude as those of filtered DNS. This is because of the terms arising from re-decomposing of the SGS stresses in the DTM model. It was also found that this incompetence in simulating the SGS stress is not necessary to simulate GS energy evolution, as is known for wall turbulence. Updated from the Japanese original (J Soc Nav Archit Jpn 2001; 190:27–39)