Study on One—Dimensional Model of Traffic Flow with Stochastic Deceleration via Lattice Boltzmann Method

One-dimensional traffic model was studied with the consideration of stochastic deceleration by using the lattice Boltzmannmethod.The evolution equation for vehicle density was derived,which has the form of the Burgers equation exhibiting the effect of viscosity corresponding to the deceleration.The simulation with the model shows that the variation of vehicle density in space tends to a periodic one,which implies the existence of kinematic waves in the 1D traffic flow and coincides with theoretical prediction.     

颗粒在流体中相互作用的晶格玻尔兹曼方法模拟

运用晶格玻尔兹曼方法研究了两个颗粒在Poiseuille流中的运动行为.分析了颗粒直径和管道直径之比d/D对颗粒相互作用的影响;讨论了颗粒的水平距离、颗粒的平衡位置与颗粒直径之间的关系.研究发现当d/D小于0.5时,颗粒的水平距离稳定在4.2倍的颗粒直径左右.研究对于理解多颗粒系统中颗粒之间的相互作用等具有一定的价值.     

用神经网络方法对高速公路交通流控制模型中的参数进行辨识

从高速公路交通流的宏观、动态特征出发，首先给出了交通流控制和仿真中常用的宏观、动态、确定性交通流模型，并利用神经网络的方法对模型中的参数进行辨识．从而获得能比较准确描述交通流真实行为的模型，以此来解决高速公路交通的最优控制问题．     

基于改进支持向量机模型的交通拥堵情况预测

随着机动车数量的迅猛增加,城市交通拥堵状况日益严峻,城市道路拥堵严重影响着居民的日常工作和生活,因此研究道路拥堵程度,以及对道路拥堵变化进行预测则显得尤为重要。为此,构建一个基于拥堵指标的MM-SVR模型,在考虑下一时段可能到达路段的潜在车流量情况下,对道路拥堵情况进行深入探究。首先,融合速度、区域内交通流量构建道路拥堵程度指标,然后基于历史数据构建将马尔科夫链与支持向量机预测相结合的MM-SVR模型对道路拥堵进行预测,以向前[n]阶状态的交通流量和速度作为输入量,将道路拥堵程度指标作为输出量。在实例验证中,使用广州市某片区的实时交通流数据对模型效果进行评测,并且使用SVR以及Adaboosting模型进行对比实验。实验结果表明,该模型无论是在拟合优度还是预测误差上均优于对比模型,在实时反映交通流拥堵情况方面有着良好表现。     

基于诱导信息的交通堵塞路径流量转移模型

以UE均衡分配为前提,根据个别路段出现突发性交通堵塞的程度来发布诱导信息,并以此为依据分析出行者新的路径选择行为,从而建立路径流量转移模型,通过堵塞路径的流量转移来获取最优的交通分配新模式.     

车道被占用对城市道路通行能力影响的传统交通流模型

以2013年全国大学生数学建模竞赛A题为背景,利用传统交通流模型研究车道被占用对城市道路通行能力影响.首先进行模型假设;其次建立模型和求解模型,以车流波动理论建立传统交通流模型,分析车流排队与消散的过程以及集结波与消散波的传播方式,得到车辆排队长度x以及事故消散时间T＊的表达式;最后通过模型检验,说明模型具有一定的稳定性和鲁棒性.     

High velocity flow simulation using lattice Boltzmann method with no-free-parameter dissipation scheme

A finite difference lattice Boltzmann method of second-order accuracy in time is developed based on non-oscillatory scheme with no-free-parameter dissipation (NND) difference scheme in this paper. The NND lattice Boltzmann method is used to simulate high-speed flows by constructing a new equilibrium distribution function of the lattice Boltzmann method.Compared with a variation of lattice Boltzmann method developed by Qu, et al., the present method can capture shock waves and handle oscillations of high velocity flows accurately in larger time steps and in shorter computing time. Numerical results indicate the correctness and capability of simulating shock wave interactions of the NND lattice Boltzmann method.     

基于遗传算法的交通量平衡分配预测

本文介绍了现有交通分配模型,并分析了现有模型的局限性,提出了基于遗传算法的交通量平衡分配预测模型,并给出了算例对所提模型进行了验证。     

小波神经网络在短时交通流预测中的应用

研究了小波神经网络对于预测短时交通流的适应性,提出了利用小波神经网络的特性建立短时交通流预测模型;并利用苏州市某交叉口实测交通流量,运用小波神经网络建立了非线性回归预测模型,结果证明预测是可靠的,有助于城市交通流动态参数的预测,可为 ITS 的构建提供数据支持     

微通道中甲醇蒸汽重整反应过程的LBM模拟

采用格子-Boltzmann方法对平行平板间甲醇水蒸气重整反应过程进行模拟,其中包括反应、对流、扩散。模拟中假设化学反应对流场没有影响,流场、温度场和组分场可分别利用演化方程进行求解,利用多尺度技术可分别将演化方程回归到对应的宏观方程。在低Ma的条件下格子-Boltzmann方法模拟的结果与传统Navier-Stokes方程数值计算结果进行对比,吻合得较好,证明了格子-Boltzmann方法的可靠性。     

潜水一维非稳定流方程的数值求解与工程应用

针对潜水一维非稳定流方程,先分别采用分离变量法和有限差分法进行求解,然后对比解析解结果,讨论显式差分法和隐式差分法的求解精度,最后将研究成果应用在某基坑降水水位预测中。研究结果表明:采用分离变量法可有效求解一类边界下潜水一维非稳定流方程;在相同密度网格剖分下,显式差分法较隐式差分法的求解精度要高,但显式差分法对网格剖分要求较高,实际应用时可根据计算精度以及计算效率等要求综合选用求解方法。     

一种基于深度学习的夜间车流量检测方法

当车流量较少时,降低路灯亮度可以达到能源节约目的。为此,采用深度学习中的R-FCN目标检测网络完成夜间车辆检测任务。R-FCN网络相比传统深度学习网络,不仅是基于区域推荐模型的网络,而且引入了平移变化特性,所以对目标检测效果更好。为了占用更少硬件资源,缩小模型规模,采用ShuffleNet通道分组与组间通信机制,压缩原始残差网络。同时,对NMS（非极大值抑制）算法进行修改,从而可以更好地筛选重叠目标,降低网络漏检率。实验结果表明,该方法准确率较高,在UA-DETRAC数据集的夜间图片检测中精度最高可达到90.89%。     

Numerical simulation of wind flow fields around buildings using the lattice Boltzmann method

This paper presents the simulation results of the wind environment around a single high-rise building and that around two tall buildings in tandem arrangement by using the lattice Boltzmann method with an aim to understand the ventilation issues around high-rise buildings in an urban environment. We analyzed the velocity distribution around the buildings and performed numericl simulations to reveal the formation and evolution law of the complex vortex system around the high-rise buildings. Numerical simulation results manifest a periodicity phenamenon in the process of the vortex evolution. For the case of two high-rise buildings, wind velocity in the space between the two buildings is very small, which is nearly a silent regime. Wind velocity above the front building is relatively larger and the maximum wind velocity is approximately 2.5 times the incoming wind velocity. The numerical results can be used in layout planning of high-rise residential buildings to create better environment for ventilation purpose in an urban area.     

Simulation of two-phase flows of a droplet impacting on a liquid film with an improved lattice Boltzmann model

Based on the lattice Boltzmann method (LBM), an improved pseudo-potential model, combined with a method of adding force term, is used to simulate the two-phase flows caused by a liquid droplet impacting on a liquid film. In this model, the different phases are treated as one fluid, and the interfaces between the vapor and liquid phases can be obtained by density value of the fluid. This variant of the LBM allows one to obtain the densities of vapor and liquid with high accuracy. The model is validated by an example of phase separation. The early stage of the impact of droplet on liquid film is simulated, and the results are qualitatively consistent with physical phenomena.     

Performance investigation of 2D lattice Boltzmann simulation of forces on a circular cylinder

The lattice Boltzmann method (LBM) is employed to simulate the uniform flow past a circular cylinder. The performance of the two-dimensional LBM model on the prediction of force coefficients and vortex shedding frequency is investigated. The local grid refinement technique and second-order boundary condition for curved walls are applied in the calculations. It is found that the calculated vortex shedding frequency, drag coefficient and lift coefficient are consistent with experimental results at Reynolds nu...     

粘性层流流体速度分布的数值计算方法

介绍了如何运用数值计算方法来求解粘性层流流体的速度分布,通过坐标系转化理论、连续性方程、Navier-Stokes方程导出有关速度的非线性微分方程,运用数值计算方法分别对对称性速度流体和非对称性速度流体进行数值求解,其结果对深入了解粘性流体运动的基本规律有着重要的现实意义。     

Burgers方程的超离散化及其应用

从交通流模型中导出Burgers方程.方程通过自变量以及因变量的离散化得到超离散Burgers方程.并且在适当的条件下成为Burgers元胞自动机.应用Burgers元胞自动机研究一雏初等交通流模型.     

基于诱导信息的交通流动力学特征与非线性密度波研究

In this dissertation,based on the existing macro- scopic and microscopic models for traffic flow,several improved mathematical models in accordance with the rapid development of intelligent transportation system (ITS) are proposed,and the corresponding theoretical analysis and numerical simulation are performed.In     

穿越主路多车道混合车流的通行能力

本文以可接受间隙理论为基础 ,利用概率论方法 ,对以 1型车 ,2型车 ,… ,r型车等r种代表车型组成的混合车流进行分析 .建立了无信号交叉口支路混合车流穿越主路m条车道 ,每一车道的交通流车头时距服从不同强度的M3分布的通行能力模型 ,发展了无信号交叉口单一车型、单一车道车流理想条件的通行能力理论 .     

格构锚杆边坡支护优化设计及计算方法研究

结合实际工程案例研究了格构锚杆边坡支护优化设计的方法和步骤,使用条分法计算了边坡加固前后的安全系数,并提出了采用安全系数控制的格构锚杆边坡支护的优化设计方法,建立了一套针对格构锚杆边坡支护优化设计的设计体系。