基于CFD方法的螺旋桨性能计算与分析

为实现快速预报螺旋桨敞水性能,并根据需要准确读取指定类型和指定位置的数据,利用FLUENT流体计算软件对螺旋桨敞水实验进行数值模拟,根据数值计算的结果绘制敞水性能曲线,并与实验结果进行比较,分别研究进速系数的变化和入射角的变化对螺旋桨性能的影响。     

冲击波和气泡脉动联合作用下加筋板的毁伤仿真研究

运用有限元程序MSC．Dytran对无限水域近场非接触爆炸冲击波和气泡脉动载荷下加筋板的毁伤进行研究,分析两种冲击载荷的不同作用方式、作用位置和毁伤效果。在此基础上分析加筋板结构和气泡脉动的相互影响,距离参数的改变对气泡中心移动方向、射流方向和射流强度的影响。并对Blake准则在弹性结构边界下的使用范围进行探讨。     

缓冲结构减缓高速铁路隧道出口微压波数值比较

研究了高速铁路隧道出口微压波产生机理,结合一维可压缩非定常不等熵空气流动理论和无限大障板圆形活塞辐射理论,应用数值计算方法研究了不同形状缓冲结构条件下高速铁路隧道出口附近微压波规律。通过对缓冲结构形状以及各种参数计算结果进行定性与定量对比,发现对于截面积变化的线型、抛物线型和不连续型缓冲结构,随着长度和端口截面积增加,隧道出口附近微压波强度衰减较大,其中不连续型缓冲结构综合效果最佳;而截面积为常量,具有开孔的缓冲结构,虽然也可较大幅度降低隧道出口附近微压波强度,但是需要综合比较才能选取最佳结构参数。     

轨道不平顺数值模拟方法

为了提高将轨道功率谱密度函数(PSD)通过数值模拟方法转换为时域样本的可靠度,分析了国内外常用的轨道不平顺数值模拟方法的模拟原理和步骤,采用计算机仿真程序模拟出各种方法生成的时域样本,并以此作为车辆垂向动力学模型的输入激励,通过数值仿真得出系统的时间-响应历程。各种模拟方法模拟结果比较表明采用各种方法模拟出的轨道不平顺时域样本是正确的,用三角级数法和逆Fourier变换法模拟出的时域样本的离散度较小,而用白噪声滤波法和二次滤波法模拟的时域样本离散度较大,因此后两种方法模拟出的轨道不平顺时域样本不宜作为研究系统时域响应时的轨道激励。     

高速公路动态交通流Elman神经网络模型

为了提高高速公路交通流建模的精度,分析了离散的高速公路动态交通流数学模型,基于Elman网络原理,建立了回归神经网络交通流模型。回归神经网络的输入层、上下文层、隐含层和输出层的节点数目分别选为8、30、30和2,采用Levenberg-Marquardt算法对回归神经网络进行训练,并对一条5路段的高速公路进行仿真。结果表明:回归神经网络平均相对误差为8.683 7×10-5,最大相对误差为4.237 1×10-4,与BP神经网络和RBF神经网络相比较,Elman回归神经网络能更好地逼近交通流数学模型,真实地描述交通流基本特性,能准确地建立动态交通流模型,适应交通状况的变化。     

利用刀补功能建立工件坐标原点

作者在数控加工与编程课程教学与实训过程中,经分析得到一种与目前教科书不同的确定工件坐标原点的方法,即利用刀补功能,建立工件坐标原点的方法。经理论分析及实搡证明,该方法简捷、准确。是值得在数控加工与教学中推广的一种方法。     

空气弹簧对车辆曲线通过性能的影响

建立了考虑左右空气弹簧垂向耦合模型的车辆系统数学模型,由理想气体的状态方程得到空气弹簧的力学方程,分析了车辆通过曲线时车辆与空气弹簧的动态特性。仿真结果表明:由于高度阀的动作,车辆在驶出曲线后各空气弹簧的压力不一致,导致车体不能回到静平衡位置;车辆以正常速度通过曲线时,车辆曲线通过动力学性能变化不大;在车辆多次通过同一种曲线的较恶劣工况时,空气弹簧内气压变化范围是一定的;增加抗侧滚刚度能明显抑制车体侧滚,从而减小空气弹簧内气压的变化量;增大空气弹簧横向跨距,并选择合适的刚度和阻尼,能使车辆驶出曲线后各空气弹簧压力接近静平衡值。     

基于ANSYS的350 km/h高速动车组用鼓形齿式联轴器的参数化建模

对350 km/h高速动车组用鼓形齿式联轴器的结构进行了分析,并采用ANSYS软件的APDL语言对其实现了参数化建模,大大方便了以后对该联轴器进行的相关分析,并且为复杂结构的建模提供了一个新的思路和方法.     

Within day rescheduling microsimulation combined with macrosimulated traffic

The concept of rescheduling is essential to activity-based modeling in order to calculate effects of both unexpected incidents and adaptation of individuals to traffic demand management measures. When collaboration between individuals is involved or timetable based public transportation modes are chosen, rescheduling becomes complex. This paper describes a new framework to investigate algorithms for rescheduling at a large scale. The framework allows to explicitly model the information flow between traffic information services and travelers. It combines macroscopic traffic assignment with microscopic simulation of agents adapting their schedules. Perception filtering is introduced to allow for traveler specific interpretation of perceived macroscopic data and for information going unnoticed; perception filters feed person specific short term predictions about the environment required for schedule adaptation. Individuals are assumed to maximize schedule utility. Initial agendas are created by the FEATHERS activity-based schedule generator for mutually independent individuals using an undisturbed loaded transportation network. The new framework allows both actor behavior and external phenomena to influence the transportation network state; individuals interpret the state changes via perception filtering and start adapting their schedules, again affecting the network via updated traffic demand. The first rescheduling mechanism that has been investigated uses marginal utility that monotonically decreases with activity duration and a monotonically converging relaxation algorithm to efficiently determine the new activity timing. The current framework implementation is aimed to support re-timing, re-location and activity re-sequencing; re-routing at the level of the individual however, requires microscopic travel simulation.     

(Unintended) Transport impacts of an energy-environment policy: The case of CNG conversion of vehicles in Dhaka

Motor vehicles are one of the major sources of air pollution in Dhaka, the capital of Bangladesh. The government took various policies to convert the petroleum vehicles on road to run on compressed natural gas (CNG), which allows both air quality improvements and energy security benefits. One of the market friendly policies to encourage the fuel switch was to increase the price differential between CNG and petrol and diesel. This has allowed a wide-scale adoption of CNG as the fuel of choice. However, several years into the policy, there is now a widespread belief among the policymakers that the CNG conversion may have increased car ownership and car travel due to their lower running costs, resulting in more congestion and a reversal of the strategy is on the cards. It is therefore important to test the hypothesis whether CNG conversion had genuinely increased car ownership and car travel in Dhaka city. This paper presents the results of a questionnaire survey and an econometric intervention analysis to understand the impact of CNG conversion on car ownership and car travel in Dhaka. Attention is also given to disentangle the self-selection and price-induced travel effects of CNG conversion. Results show that ownership did not increase, but travel of on-road vehicles increased due to the CNG policy. However, additional congestion costs are still around one half of the health benefits brought about by the policy.