不同数值积分方式对海洋结构物疲劳裂纹扩展模拟结果的影响

海洋结构物的疲劳寿命预报是当前的研究热点,文章根据第二作者率领的课题组提出的海洋结构物疲劳寿命预报统一方法比较了疲劳裂纹扩展模拟的三种数值积分方法：逐周数值积分法、△N积分法和△a积分法,并分析了每种方法的适用条件。随后,以中心表面裂纹承受单向交变拉伸载荷的平板为例,分别运用三种方法计算了裂纹扩展寿命和最终裂纹尺寸。同时,研究了△N和△a取值不同对结果的影响。最后,综合考虑计算耗时和计算结果精度,给出了△N积分法和△a积分法的建议值,即△N/N≤1.0%,△a≤0.1 mm。     

高桩码头异常靠泊有限元仿真模拟

船舶大型化、靠泊作业频繁、管理漏洞以及某些不可抗力因素造成异常靠泊事故时有发生。目前,码头在异常靠泊情况下的受力及位移特性尚不明确,损伤评估缺乏理论基础,为使现场检测更有针对性,利用ANSYS有限元结构分析软件建立了受损码头的数学模型,考虑了桩土间相互作用及橡胶护舷对碰撞的缓冲作用。将模型碰撞损伤结果与码头实际受损情况进行对比,简要分析了碰撞中部分结构受力极值的相对关系和位移情况。结果表明：在该碰撞实例条件下,模型运行基本可反映异常靠泊发生时高桩码头结构损伤情况。     

波浪中船舶操纵性预报

为实现对全回转桨船操纵性的预报,根据船舶分离型运动模型的建模方法,考虑全回转桨在水平面上周转的灵活性与受力的特殊性,着重分析双桨受力,建立适用于全回转对转桨船模的MMG操纵运动数学模型;模拟船模进行PMM运动,求得水动力导数并采用四阶龙格-库塔法对操纵性常微分方程进行求解;对某工程船在静水中的回转运动和Z形操纵运动进行数值仿真预报,并将预报结果与自航模操纵性试验结果进行对比。结果表明,两者吻合度较高,验证了针对全回转对转桨船模所建立的船舶运动数学模型的有效性,可为全回转桨船的操纵性预报提供一种较为可靠且行之有效的方法。     

仿真技术在舰船动力装置生命周期中的应用研究

  目的  在充分分析舰船动力装置总体设计研究现状的基础上,指出现有动力装置设计方法中存在缺乏从多学科耦合角度进行仿真和优化,从而制约设计质量提高的问题,有必要开展动力装置多学科集成优化理论、方法及关键技术研究。  方法  建立舰船动力装置多学科集成优化设计系统框架,并对动力装置多学科优化技术、现代设计工具技术、协同仿真、支撑环境、设计软件开发等关键技术进行深入研究。  结果  给出了有效的解决方案。  结论  研究成果能为开展舰船主动力装置多学科集成设计优化提供一定的参考,同时为舰船动力装置设计水平的提高奠定一定的基础。     

小水线面双体船耐波性能CFD不确定度分析

  目的  为了提高航海模拟器中小水线面双体船（SWATH）的模拟精度,更好地掌握此类船舶的操纵特性,  方法  根据SWATH船型的运动特点,在MMG三自由度模型的基础上,较为完整地计入耦合的纵荡、横荡、艏摇、横摇及纵摇运动,建立SWATH的五自由度运动数学模型。基于此应用模型建立SWATH的实船数学模型,对该数学模型进行微分求解,仿真模拟SWATH的旋回运动、Z形运动,并进行定性分析。  结果  分析显示：仿真模拟结果符合SWATH操纵运动原理及实际运动特征,验证了数学模型的准确性。  结论  该模型可真实反映实船的运动规律,可应用于航海模拟器中。     

Assessment of energy-saving techniques in direct-current-electrified mass transit systems

Railway rapid transit systems are key stones for the sustainability of mass transit in developed countries. The overwhelming majority of these railway systems are direct-current (DC) electrified and several energy-saving techniques have been proposed in the literature for these systems. The use of regenerative-braking in trains is generally recognised as the main tool to improve the efficiency of DC-electrified mass transit railway systems but the energy recovered in braking cannot always be handled efficiently, above all in low traffic-density situations. Several emerging technologies as energy storage systems or reversible traction substations have the potential for making it possible to efficiently use train-braking. However, a systematic evaluation of their effect is missing in the literature.In this paper, a deep, rigorous and comprehensive study on the factors which affect energy issues in a DC-electrified mass transit railway system is carried out. This study clarifies what the actual potential is for energy saving in each situation. Then, a methodology to asses several energy-saving techniques to improve energy efficiency in DC-electrified mass transit systems is presented, constituting the main contribution of this paper. This methodology has been conceived to help operators in assessing the effect of railway-infrastructure emerging technologies in transit systems, so making it possible to shape planning, capacity, etc. It is stepped out in three basic movements. First of all, a traffic-density scan analysis is conducted in order to clarify the effect of the headway on system behaviour. Secondly, several traffic-density scenarios are simulated for a set of infrastructure-expanded cases. Finally, annual energy saving is evaluated by applying a realistic operation timetable. This methodology has been applied to a case study in Madrid Metro (Spain) to illustrate the steps of its application and the effect of several energy-saving techniques on this specific system. Results confirm that regenerative braking generally leads to an important increase of system energy efficiency – especially at high traffic-density scenarios. It has also been proved that infrastructure improvements can also contribute to energy savings and their contributions are more significant at low traffic densities. Annual energy results have been obtained, which may lead to investment decisions by carrying out an appropriate economic assessment based on cost analysis.The main results of the study presented here are likely to apply to other electric traction systems, at least qualitatively.     

沿程磁处理管道输油实验研究

南海原油密度大、含蜡量高,对南海原油采用沿程磁处理,可降低聚集度,从而达到降黏输送的作用.为进一步研究磁处理对油品有降黏效果,使用仿真软件模拟磁铁摆放得到磁感应强度分布,再通过搭建沿程磁处理输油实验管道,以南海原油为介质进行实验研究.将有无磁处理的压力数据进行对比,并结合使用流变仪测定的油品黏度变化,综合分析得出使用2...     

长距离密闭输油管道的水击数值模拟

在长距离密闭输油管道中间泵站断电停运的情况下,采用特征线法对全线压力变化情况进行了数值模拟。结果表明:越是靠近下游的泵站停运后,越能更快地形成越站输送,出现进站压力小于泵吸入压力的时间越晚,管道的最大压力越大,管道出现液柱分离的机会越小等。     

A generic data assimilation framework for vehicle trajectory reconstruction on signalized urban arterials using particle filters

With trajectory data, a complete microscopic and macroscopic picture of traffic flow operations can be obtained. However, trajectory data are difficult to observe over large spatiotemporal regions—particularly in urban contexts—due to practical, technical and financial constraints. The next best thing is to estimate plausible trajectories from whatever data are available. This paper presents a generic data assimilation framework to reconstruct such plausible trajectories on signalized urban arterials using microscopic traffic flow models and data from loops (individual vehicle passages and thus vehicle counts); traffic control data; and (sparse) travel time measurements from whatever source available. The key problem we address is that loops suffer from miss- and over-counts, which result in unbounded errors in vehicle accumulations, rendering trajectory reconstruction highly problematic. Our framework solves this problem in two ways. First, we correct the systematic error in vehicle accumulation by fusing the counts with sparsely available travel times. Second, the proposed framework uses particle filtering and an innovative hierarchical resampling scheme, which effectively integrates over the remaining error distribution, resulting in plausible trajectories. The proposed data assimilation framework is tested and validated using simulated data. Experiments and an extensive sensitivity analysis show that the proposed method is robust to errors both in the model and in the measurements, and provides good estimations for vehicle accumulation and vehicle trajectories with moderate sensor quality. The framework does not impose restrictions on the type of microscopic models used and can be naturally extended to include and estimate additional trajectory attributes such as destination and path, given data are available for assimilation.     

The speed control effect of highway tunnel sidewall markings based on color and temporal frequency

The low‐luminance monotonous environment in the middle section of highway tunnels offers few reference points and is prone to cause severe visual illusion. Thus, drivers tend to underestimate their driving speed, which can induce speeding behaviors that result in rear‐end collisions. Therefore, discovering low‐cost methods of traffic engineering that reduce this visual illusion and ensure a steady driving speed is an important challenge for current highway tunnel operations. This study analyzes the effects of sidewall markings in typical highway tunnels, specifically observing how their colors and temporal frequencies affect the driver's speed perception in a low‐luminance condition. A three‐dimensional model of the middle section of highway tunnels was built in a driving simulator. Psychophysical tests of speed perception were carried out by the method of limits. The precision of the simulation model was then checked by comparing the results to field test data. The simulation tests studied the stimulus of subjectively equal speed and reaction time in relation to sidewall markings in different colors (red–white combined, yellow–white combined, and blue–white combined). Furthermore, based on the optimal color, the effects of sidewall marking with different temporal frequencies (0.4, 0.8, 1.2, 2, 4, 8, 12, 16, and 32 Hz) on the speed perception of drivers were also analyzed. The test results reveal that the color and temporal frequency of sidewall marking have a significant impact on the driver's stimulus of subjectively equal speed and reaction time. The subjects have the highest speed overestimation and an easy speed judgment with the red–white combined sidewall marking. Within the temporal frequency range of 4.45–7.01 Hz, the subjects have a certain degree of speed overestimation (less than 20%), and the speed perception is sensitive to the temporal frequency changes. Copyright © 2016 John Wiley & Sons, Ltd.