Sail–sail and sail–hull interaction effects of hybrid-sail assisted bulk carrier

In a previously reported study, wind tunnel experiments were undertaken to investigate the aerodynamic characteristics of hybrid-sails in isolation. Such sails are seen as providing a worthwhile reduction in the delivered power to the propeller and hence the engine generated thrust, with a corresponding reduction in the CO₂ production of diesel engine exhaust. In this paper, wind tunnel testing is used to investigate sail–sail interaction effects for two sets of four identical hybrid-sails, and the sail–hull interaction effects for the same two sets of four identical sails in the presence of a bulk carrier hullform. The analysis presented suggests that to build a sail-assisted ship requires an appreciation of the sail–sail and sail–hull interaction effects.     

Hydrographic cruises off northwest Africa: the Canary Current and the Cape Ghir region

We present hydrographic data for several sections located along the African coastline and off Cape Ghir, carried out at times of weak surface winds (October 1995 and September 1997). The main sections are near the continental slope, at mean distances between 100 and 150 km from the coastline. North of Cape Ghir (31°N) the geostrophic transport (referenced to 650 m) of North Atlantic Central Water through these sections is 3.7 and 2.0 Sv for 1995 and 1997, respectively. This confirms that a major fraction of the water transport by the Canary Current flows east, into the continental slope off northwest Africa, at latitudes above Cape Ghir. Most of this flow continues south past Cape Ghir, along the coast and probably through the eastern passages of the Canary Archipelago. A significant fraction, however, may escape through surface Ekman transport (0.3–0.5 Sv during the early fall season) and by offshore flow at Cape Ghir (1.1 Sv in September 1997, referenced to 650 m). Despite the weak winds the Cape Ghir filament was clearly visible, characterized by localized coastal upwelling associated to a cyclonic shallow structure and cold (and fresh) waters stretching offshore as a very shallow feature (50–100 m deep). The satellite images show that the surface temperature field is highly variable, in rapid response to the surface winds, always with a core region of relatively cold water and commonly with one or two associated eddies. Our results support the existence of two recirculation cells in the area: a horizontal one that connects the interior eastern boundary currents with the coastal region and a vertical one related to both wind-induced and filament upwelling. The data also show a salinity subsurface maximum at the root of the filament, linked to water inflow from northern latitudes, and a subsurface anticyclonic eddy over the Agadir canyon, likely related to the poleward slope undercurrent.     

Use of a probabilistic particle tracking model to simulate the Prestige oil spill

A probabilistic particle tracking model is used to simulate the oil dispersion after the Prestige wreckage. This oil spill constitutes a suitable benchmark to analyze the capabilities of a probabilistic model, since the time elapsed from wreckage to oil landing (12 days) is much longer than the reliability time associated with forecast winds, usually on the order of 3–4 days. The particle model can be run in two different modes: real time mode (when existing reliable wind fields for the event under scope) and in probabilistic mode (in absence of reliable wind fields but with historical fields corresponding to a similar period). The validity of the particle model is first evaluated in a hindcast way, running the Prestige case with the wind fields corresponding to the period November 19 to November 30, 2002, which were not available at the moment of the wreckage. Calculations show the accuracy of the model to provide the right impact point and timing. The probabilistic model is then used to simulate the same event by means of historical data. The region where the oil landed is shown to be the area with the highest probability to be impacted.     

A reduced-gravity model of the Catalan Sea

A reduced-gravity model is used to study the effects of the wind on the upper layer circulation in the Catalan Sea. The model parameters were set by observed features of the circulation in the basin. It is shown that the results are particularly sensitive to the open sea boundary conditions. Simulations were done using the following boundary fluxes: (i) mean values estimated by Bethoux (1980) and (ii) more recent geostrophic transports computed from hydrographic data by Font et al. (1988). The latter seem to lead to more realistic circulation patterns. The influence of seasonal winds (climatological data) on the dynamics is clear, especially during the winter.     

一种用汽油燃烧系统模拟发动机台架催化剂热老化的方法

采用通用汽车公司的快速老化程序RAT-A，分别在FOCAS燃烧系统及发动机上对催化剂在老化前和老化后的性能进行对比试验。结果表明，FOCAS燃烧系统能够对催化剂进行和发动机类似的老化。与发动机台架试验相比，FOCAS系统有明显的优点，如严格地控制空燃比使其变化幅度很小、空燃比稳定运行的范围宽、活动部件少及易操作等。     

怎样卖掉你的车

在汽车消费发达的国家，二手车消费是整个汽车消费的重要组成部分。甚至可以说，科学、合理、完善的二手车消费体制带动了整个汽车消费的发展。在今天的中国，汽车越来越多地进入了家庭，准备置换手中旧车的人也越来越多，所以《爱车》特别邀请美国二手车销售专家M.Brueggemann先生为中国的车主朋友奉献一篇精彩的文章，虽然本文充满美国社会的气息，很多技巧不能直接套用，但是先进的经验是绝对值得借鉴的。[编者按]     

内破裂的数值模拟与分析

应用气—波两相流理论，引入计算流体动力学方法中的SIMPLE（Semi—ImplictMethodforPressure－LinkedEquations）方程，并在此基础上进行改进，对压力筒内的内破裂现象进行了系统的研究。本文发展了一套不依赖于试验结果的预报方法，较之以前的理论研究结果有了长足的进展，所采用的模型与假设能用于多种内破裂状况的模拟与预报。本文对一典型的内破状态进行了数值模拟，结合物理现象对模拟结果进行了分析，并与试验作比较。分析结果以一组计算机所绘图形表示，输出结果可作为压力筒结构动力分析的基础，所研制的程序也可作为内破裂问题流—固耦合研究的一大模块。     

Improved customs inspection at a small international airport: Case study: Colombo

The present procedures for processing arriving passengers at the Colombo International Airport cause inordinte waiting times. An alternate plan, which is based on state of the art customs procedures, and which can reduce waiting times significantly while maintaining a high level of enforcement, is proposed. The present and proposed procedures are analyzed and compared with respect to passenger waiting times, using deterministic queueing theory. An optimal inspection rate of passengers by the customs service is proposed taking into account the fraction of inspected passengers, the waiting time of passengers and the cost of customs processing.     

Simulation Approach to the Effect of the Ratio Changing Speed of a Metal V-Belt CVT on the Vehicle Response

In regard to the belt and pulley system of a metal V-belt CVT, the characteristics of the ratio changing speed is obtained by experiments. It is summarized in a practical and simple experimental equation. By using this equation a simulation model is developed to analyze the response of a vehicle with a metal V-belt CVT to a rapid pulley ratio change. The simulation results are in reasonable agreements with experimental results.