关于辐流式二沉池设计计算方法的探讨

针对辐流式二沉池设计资料中存在的相关问题,从平面设计要点和竖向设计要点两方面分别对辐流式二沉池中设计流量的选定、沉淀池表面积计算、进出水口、污泥区容积计算,以及有效水深、池边水深和总池高计算等进行了探讨,并对刮(吸)泥设备和配水井的设计要点进行了相关说明.同时结合工程实践,优化平面设计参数和竖向设计参数,合理选择刮(吸)泥设备和配水井等辅助设施,能为相关技术人员提供一定的参考和借鉴意义.     

三叶片节气门进气系统的 CFD 计算和分析

以一款新型三叶片式节气门为主要研究对象，通过发动机台架试验，获得发动机稳态工况下进气歧管三维C FD计算的边界条件，选取不同转速、不同负荷率的12个有代表性的工况点，建立配置传统的单叶片节气门和三叶片节气门的进气歧管网格模型，并进行C FD计算和流场分析。结果表明：发动机处于中、高负荷时，由三叶片节气门产生的进气涡流比单叶片节气门大，且优势随节气门开度的增加而更加明显，但在低转速、小负荷的工况下，配置三叶片节气门的进气歧管内的涡流强度小于单叶片节气门。     

散装水泥运输罐车刹车过程物料流动特性研究

为探索散装水泥运输半挂车在刹车过程罐内物料的流动特性，基于FLUENT计算流体力学软件，采用欧拉-欧拉方法建立双流体模型，通过Syamlal-O＇Brien模型描述气-固曳力，对散装水泥运输半挂车在刹车过程罐内水泥的流动特性进行了数值模拟。结果表明，散装水泥运输半挂车在刹车过程中，罐内水泥向前运动，牵引车载荷高于设计载荷，对此提出通过在罐内顶部增设阻流板，可有效避免散装水泥运输半挂车在刹车过程由于载荷分布不合理而引起的一系列问题的改进措施。     

A framework for short-term traffic flow forecasting using the combination of wavelet transformation and artificial neural networks

The main objective of this paper is to develop a framework for short-term traffic flow forecasting models with high accuracy. Due to flow oscillations, the real-time information presented to the drivers through variable message signs, etc., may not be valid by the time the driver reaches the location. On the other hand, not all compartments of the flow signal are of same importance in determining its future state. A model is developed to predict the value of traffic flow in near future (next 5–35?minutes) based on the combination of wavelet transformation and artificial neural networks. This model is called the hybrid WT-ANN. Wavelet transformation is set to denoise the flow signal, i.e., filtering the unimportant fluctuations of the flow signal. Unimportant fluctuations are those that have little or no effect on the future condition of the signal. The neural network is set and trained to use previous data for predicting future flow. To implement the system, traffic data of US-101 were used from Next Generation Simulation (NGSIM). Results show that removing the noises has improved the accuracy of the prediction to a great extent. The model was used to predict the flow in three different locations on the same highway and a different highway in a different country. The model rendered highly reliable predictions. The proposed model predicts the flow of next 5?min on the same location with 2.5% Mean Absolute Percentage Error (MAPE) and of next 35?min with less than 12% MAPE. It predicts the flow on downstream locations for next 5?min with less than 8% MAPE and for the different highway with 2.3% MAPE.     

High-resolution numerical relaxation approximations to second-order macroscopic traffic flow models

A novel numerical approach for the approximation of several, widely applied, macroscopic traffic flow models is presented. A relaxation-type approximation of second-order non-equilibrium models, written in conservation or balance law form, is considered. Using the relaxation approximation, the nonlinear equations are transformed to a semi-linear diagonilizable problem with linear characteristic variables and stiff source terms. To discretize the resulting relaxation system, low- and high-resolution reconstructions in space and implicit–explicit Runge–Kutta time integration schemes are considered. The family of spatial discretizations includes a second-order MUSCL scheme and a fifth-order WENO scheme, and a detailed formulation of the scheme is presented. Emphasis is given on the WENO scheme and its performance for solving the different traffic models. To demonstrate the effectiveness of the proposed approach, extensive numerical tests are performed for the different models. The computations reported here demonstrate the simplicity and versatility of relaxation schemes as solvers for macroscopic traffic flow models.     

复合地层泥水盾构环流关键参数选择探析

为研究复合地层泥水盾构泥水环流参数选择的问题,结合狮子洋隧道盾构工程,采用泥浆临界沉淀流速计算方法计算软弱地层和软硬不均地层所需的泥浆送、排量,并运用费祥俊模型试验公式进行验算。由于复合地层地质条件的复杂性,泥水盾构环流参数的影响因素较多,结合以上计算结果分析不同地层特性对泥浆送、排量的影响。研究结果表明： 1）2种方法的泥浆送、排量计算结果相差不大,证明泥浆临界沉淀流速计算方法具有准确性和合理性; 2）在软硬不均地层进行泥水盾构施工时,应加大泥浆送、排量,以减少输送颗粒在排浆管内滑移、平动,同时减少舱内积碴和泥浆管的磨损。研究结果可为复合地层下的泥水盾构施工提供参考。     

Performance evaluation of the inside intersection median-turn lane markings on the mobility and safety performance of signalized intersections in the Philippines and Japan

Signalized intersections are one of the key elements that play a vital role at road networks. The efficiency and safety levels of intersections can affect the operational performance of the whole system. In general, turning traffic, especially median-turning, has always been considered as the most problematic movement in the operation of intersections. This becomes more critical with high turning demand where exclusive turning lanes (single or double) can be assigned to provide larger capacities for these movements and to reduce conflicts with through traffic. However, improper treatment of median-turn lanes could create cross-maneuvering behavior which may limit the expected increase in capacity and create safety issues. Median-turning lane markings are commonly provided at intersections in Japan to guide drivers while turning which is expected to reduce the conflicts among turning traffic. Meanwhile, in the Philippines, exclusive median-turn lanes are installed at intersections without proper treatment which may contribute to the low mobility and safety levels. Therefore, this study evaluated the impact of inside intersection lane markings on the operation of median-turn lanes in terms of mobility and safety. The vehicle maneuver, speed and interactions between the turning traffic were utilized as essential components for the assessment. The empirical analysis shows that conflicting trajectories were present on double turn lanes without median-turn lane markings in the Philippines, which resulted to serious conflicts among the turning vehicles and negatively influenced the turning speed and saturation flow rate of the turn lanes. On the other hand, the turn lane markings in Japan, provided a positive impact to mobility and safety of the turning lanes. Moreover, it was also found that the geometric characteristics and traffic signal phasing scheme highly affects the capacity and safety condition of signalized intersections.     

蒸汽管道孔口泄放流量工程计算方法探究

常用的蒸汽管道孔口泄放流量计算方法是借助喷管流量计算公式,公式中的进口蒸汽比体积需借助蒸汽热力性质表换算,且低过热度时绝热指数采用经验值,得到的计算值与实际有偏差,此外,传统计算式的形式较为繁琐,这些因素在一定程度上影响了其在工程中的使用。为满足工程需求,完善蒸汽管道孔口泄放流量的工程计算方法,推导出一个适用于蒸汽状态、压力参数多变,便于工程设计分析的更为简便、准确的孔口泄放流量工程计算式,式中涉及的蒸汽状态参数易于测试,采用的温度修正因子则提高了公式在低过热度下使用的准确性。同时,结合工程实例,分析此计算式的使用情况,并认为,完善后的蒸汽管道孔口泄放流量计算式将在蒸汽管道孔口泄放问题中有更为广泛的应用。     

半潜式钻井支持平台在不规则波中的时域耦合分析

基于三维势流理论和莫里森方程,运用水动力软件AQWA,计算半潜式钻井支持平台的水动力特性。同时运用时域耦合方法,计算了风、浪、流共同作用下,半潜式钻井支持平台在三种工况(迎浪、斜浪和横浪)下的运动响应及系泊系统动力响应。时域耦合分析结果验证了该钻井支持平台满足规范要求。     

大涡模拟在河道平面二维水流模拟中的初步应用

通过丁坝对水流进行控制是航道整治中常用的工程措施,丁坝附近水流呈强紊动特性,大涡模拟相对于基于雷诺方程的时均模型对涡旋有较强的捕捉能力。在直角坐标系的基础上,将大涡模拟中的亚格子应力模型(SGS模型)引入河道水流平面二维数学模型中,通过盒式滤波函数将控制方程进行滤波,大尺度量通过控制方程直接求解,小尺度量借助Smagorinsky提出的亚格子尺度应力模型进行求解。采用空间等步长的正方形网格和交替方向隐式差分法对其控制方程进行离散求解。将模型初步应用于非淹没丁坝绕流的数值模拟中,计算结果表明,该模型对湍流旋涡的捕捉和水深计算较为合理,计算精度可满足工程实践要求。