地铁车站环控系统设计中气流组织方案的数值模拟

针对地铁车站环境控制系统设计中常用的几种典型气流组织方案,使用计算流体力学(CFD)的方法,采用重正化群双方程紊流模型,对待建地铁车站及其隧道内的温度场和气流速度场进行三维数值模拟,得到各种方案下的温度和气流速度分布。通过分析和比较,认为屏蔽门方案能够得到最优的站台候车环境,但会使隧道内的温度有较大的升高,且投资较大;在投资较小的3种方案中,混合回/排风方案的效果最佳,对该方案造成的站台上气流速度分布不均匀的情况提出了相应的改善措施,并对数值模拟方法在地铁车站环控系统设计中的应用进行了探讨。     

基于大断面高铁隧道的施工通风时间理论预测方法研究

为了获得隧道施工中风管出口到掌子面的距离（以下简称“风管距离”）以及风管出口风量对施工通风时间的影响规律，以郑万线机械配套施工的大断面高速铁路隧道为工程依托，采用CFD数值模拟和多项式拟合数值分析方法对1D、2D、3D、4D（D为断面当量直径）的风管距离搭配2 000、2 500、3 000、3 500 m3/min 4种风管出口风量作用下的最少通风时间进行研究。研究结果表明，施工通风时间受风管距离与风管出口风量2个因素的影响，通风时间t与风管距离x之间关系可以表示为t=ax2+bx+c的形式，且式中各项系数均可以通过多项式拟合表达为风管出口风量Q的函数，故研究可得出通风时间t与风管距离、风管出口风量间的函数关系式为t=f(Q)x2+g(Q)x+h(Q)，同时运用该公式对向家湾隧道工程实例的通风时间进行预测。研究成果为郑万线隧道机械化快速施工通风时间的确定提供了理论指导，研究揭示的规律及所采用方法对类似隧道工程施工通风时间的确定具有一定的参考价值。     

Flexible multibody simulation of automotive systems with non-modal model reduction techniques

The stiffness of the body structure of an automobile has a strong relationship with its noise, vibration, and harshness (NVH) characteristics. In this paper, the effect of the stiffness of the body structure upon ride quality is discussed with flexible multibody dynamics. In flexible multibody simulation, the local elastic deformation of the vehicle has been described traditionally with modal shape functions. Recently, linear model reduction techniques from system dynamics and mathematics came into the focus to find more sophisticated elastic shape functions. In this work, the NVH-relevant states of a racing kart are simulated, whereas the elastic shape functions are calculated with modern model reduction techniques like moment matching by projection on Krylov-subspaces, singular value decomposition-based reduction techniques, and combinations of those. The whole elastic multibody vehicle model consisting of tyres, steering, axle, etc. is considered, and an excitation with a vibration characteristics in a wide frequency range is evaluated in this paper. The accuracy and the calculation performance of those modern model reduction techniques is investigated including a comparison of the modal reduction approach.     

Tyre pressure monitoring using a dynamical model-based estimator

In the last few years, various control systems have been investigated in the automotive field with the aim of increasing the level of safety and stability, avoid roll-over, and customise handling characteristics. One critical issue connected with their integration is the lack of state and parameter information. As an example, vehicle handling depends to a large extent on tyre inflation pressure. When inflation pressure drops, handling and comfort performance generally deteriorate. In addition, it results in an increase in fuel consumption and in a decrease in lifetime. Therefore, it is important to keep tyres within the normal inflation pressure range. This paper introduces a model-based approach to estimate online tyre inflation pressure. First, basic vertical dynamic modelling of the vehicle is discussed. Then, a parameter estimation framework for dynamic analysis is presented. Several important vehicle parameters including tyre inflation pressure can be estimated using the estimated states. This method aims to work during normal driving using information from standard sensors only. On the one hand, the driver is informed about the inflation pressure and he is warned for sudden changes. On the other hand, accurate estimation of the vehicle states is available as possible input to onboard control systems.     

Prediction of ride quality of a Maglev vehicle using a full vehicle multi-body dynamic model

In magnetically levitated (Maglev) transportation systems, especially in electromagnetic suspension system (EMS) type Maglev systems, highly accurate prediction of ride quality is very important in order to reasonably relax guideway construction tolerances or constraints and stiffness while meeting the specification for ride comfort, thereby reducing guideway construction and maintenance costs. A full vehicle multi-body dynamic model is proposed, to facilitate a rigorous ride quality prediction of an EMS-type Maglev vehicle. Using the more realistic dynamic model proposed in this paper, the effects of guideway deflection limits, surface roughness, and levitation control system parameters on ride quality are studied numerically. The results obtained from the simulation studies are then used to facilitate a discussion of the trade-off between guideway smoothness and vehicle suspension. It can be expected that these studies could suggest cost-effective specifications for guideway construction tolerances and stiffness and EMS.     

Effect of the combined centre of gravity on the running safety of freight wagons

ABSTRACT

This paper presents an analysis of loaded freight wagon dynamics in curve alignments. We investigate the effects of the combined centre of gravity (CCOG) on the running safety of freight wagons and examine proper position of the CCOG. A simple wagon-rail model is implemented using the multibody dynamics software ADAMS/Rail. The simulation model is operated on curve tracks with various radii and velocities and the curving performances are evaluated. The results indicate that the CCOG can be located within a flexible and accurate range. The longitudinal offset is good for the curving performance and the permissible lateral offset should be assessed based on the curve radius and cant deficiency.     

Comparison of various double-lane change manoeuvre specifications

One of the commonly used performance measures to quantify a vehicle's handling transient dynamics is the maximum forward speed (MFS) while passing a certain specified double-lane change (DLC) manoeuvre without violating the boundary and tyre lift-off. The MFS is directly associated with the minimum curvature radius (MCR) of the vehicle centre of gravity (CG) trajectory controlled by the driver during the manoeuvre. The MCR is further affected by the vehicle dimensions to meet the boundary condition. In this study, a single heavy vehicle CG trajectory is assumed to be a combination of three straight lines and two third-order spline curves. A heavy vehicle multi-body system model established with ADAMS/Car is correlated with test data for step-steer and constant radius cornering events, and then the model is used to demonstrate that the assumptions considered in the formulation applied in this paper are valid for this specific vehicle category. The MCRs of four heavy vehicles are maximised among all the possible choices of the vehicle CG trajectory during each of five specific DLC manoeuvres, including North Atlantic Treaty Organization (Allied Vehicle Testing Publication 03-160W), International Organization for Standardization (ISO) 3888-1, ISO 3888-2, Consumer Union Short Course and Test Operations Procedure 2-2-609. The maximised MCR (MMCR), considered as the best possible choice of vehicle CG trajectories, is further solved as a function of the vehicle width and length. The results will show the sensitivity of the MMCR to the vehicle length and width, thus the impact on the vehicle transient handling dynamics. Finally, the comparison of five DLC specifications may help users to correlate a vehicle's MFS from one specification to others.     

活动断裂带地区地铁新型轨道结构动力响应研究

断裂带是一种地区性的灾害地质,断层粘滑错动是地震造成跨断层隧道结构严重破坏的主要因素。乌鲁木齐九家湾断层组中的第3条断层与地铁1号线交角约71°,三向变形,预计百年垂直最大错位量约650 mm。目前国内外常用的整体道床结构设计最大调高量一般不超过60 mm,高低和水平调整量有限,无法适应1号线活动断层的变形量。对乌鲁木齐新型轨道结构进行研究,利用有限元软件ABAQUS建立车辆-轨道-隧道有限元模型,分析新型轨道结构的动力响应特性,基于仿真结果推荐新型固化道床弹性模量取值为500 MPa,可满足乌鲁木齐地铁1号线安全运营和乘客舒适性要求。     

Bayesian calibration of mechanistic aquatic biogeochemical models and benefits for environmental management

Aquatic biogeochemical models have been an indispensable tool for addressing pressing environmental issues, e.g., understanding oceanic response to climate change, elucidation of the interplay between plankton dynamics and atmospheric CO₂ levels, and examination of alternative management schemes for eutrophication control. Their ability to form the scientific basis for environmental management decisions can be undermined by the underlying structural and parametric uncertainty. In this study, we outline how we can attain realistic predictive links between management actions and ecosystem response through a probabilistic framework that accommodates rigorous uncertainty analysis of a variety of error sources, i.e., measurement error, parameter uncertainty, discrepancy between model and natural system. Because model uncertainty analysis essentially aims to quantify the joint probability distribution of model parameters and to make inference about this distribution, we believe that the iterative nature of Bayes' Theorem is a logical means to incorporate existing knowledge and update the joint distribution as new information becomes available. The statistical methodology begins with the characterization of parameter uncertainty in the form of probability distributions, then water quality data are used to update the distributions, and yield posterior parameter estimates along with predictive uncertainty bounds. Our illustration is based on a six state variable (nitrate, ammonium, dissolved organic nitrogen, phytoplankton, zooplankton, and bacteria) ecological model developed for gaining insight into the mechanisms that drive plankton dynamics in a coastal embayment; the Gulf of Gera, Island of Lesvos, Greece. The lack of analytical expressions for the posterior parameter distributions was overcome using Markov chain Monte Carlo simulations; a convenient way to obtain representative samples of parameter values. The Bayesian calibration resulted in realistic reproduction of the key temporal patterns of the system, offered insights into the degree of information the data contain about model inputs, and also allowed the quantification of the dependence structure among the parameter estimates. Finally, our study uses two synthetic datasets to examine the ability of the updated model to provide estimates of predictive uncertainty for water quality variables of environmental management interest.     

A method to find correlations between steering feel and vehicle handling properties using a moving base driving simulator

There have been several investigations to find out how drivers experience a change in vehicle-handling behaviour. However, the hypothesis that there is a correlation between what the driver perceives and vehicle- handling properties remains to be verified. To define what people feel, the human feeling of steering systems was divided into dimensions of perception. Then 28 test drivers rated different steering system characteristics of a semi-trailer tractor combination in a moving base-driving simulator. Characteristics of the steering system differed in friction, damping, inertia and stiffness. The same steering system characteristics were also tested in accordance with international standards of vehicle-handling tests resulting in characteristic quantities. The instrumental measurements and the non-instrumental ratings were analysed with respect to correlation between each other with the help of regression analysis and neural networks. Results show that there are correlations between measurements and ratings. Moreover, it is shown that which one of the handling variables influence the different dimensions of the steering feel.