Long-term performance prediction of oscillating wings for assisting ship propulsion at actual seas

In order to raise ship energy efficiency, the possibility of wave energy recovery by a pair of coil-spring connected oscillating wings for assisting ship propulsion in waves is investigated. A frequency domain hydrodynamic model based on potential theory is established to predict the effect of the oscillating wings on the ship in regular waves, in terms of reducing wave-added resistance and improving seakeeping performance. The proposed linear model is suitable for short-term prediction based on conventional spectral analysis techniques, thus making it possible to evalute the long-term performance of oscillating wings for assisting ship propulsion at actual seas based on wave statistics. A sample containership is adopted to study the performance of the proposed concept. The results show that the oscillating wings can effectively reduce the added resistance of the ship at actual seas. The feasibility of this green ship technology is proved.     

预应力混凝土连续箱梁桥底板纵向裂缝分析

通过受力分析及有限元计算对预应力混凝土连续箱梁桥底板纵向裂缝进行研究,得出针对这些裂缝现象的可行控制方法。     

应用弱可压缩移动粒子半隐式法（WC-MPS）模拟三维溃坝流动

应用弱可压缩移动粒子半隐式法（WC-MPS）模拟了三维溃坝自由液面流动问题。该方法应用流体状态方程来快速求解流场压力,而不是求解压力Poisson方程。对于流动控制方程中的梯度项以及Laplace算子项,分别应用基于核函数加权平均的梯度算子模型以及Laplace算子模型进行处理。同时在固体边界处,通过定义边界粒子以及虚拟粒子来避免粒子数密度计算在边界处出现错误。应用该方法,对两个三维溃坝自由液面流动问题进行了模拟,并与实验结果进行了对比分析,表明两者结果较为一致。     

沈阳市富民桥引桥设计

沈阳市富民桥引桥为跨径30 m预应力混凝土连续刚构,主梁采用大悬臂斜腹板箱形断面,单箱三室等高度箱梁,桥墩采用双壁墩,桥台采用肋板式桥台.介绍引桥的主要设计及构造特点.     

体外预应力技术在城市人行天桥中的应用

随着城市道路的拓宽，人行过街天桥的跨径也相应地增大。采用体外预应力技术．可以有效地提高承载能力、改善受力状态、降低粱高，从而达到结构合理、外形美观、造价经济的效果。本文重点介绍了体外预应力体系的组成和相关的结构计算。     

城市地下综合管廊开挖方法及设计参数分析

研究目的:为给城市地下综合管廊设计提供参考,本文以成都天府新区汉州路北段地下综合管廊工程为背景,运用现场调查和数值分析方法,对不同开挖方案的基坑稳定性进行对比研究,并在此基础上给出合理的支护建议。研究结论:(1)成都天府新区地下综合管廊位于成都平原南部边缘,地层为第四系人工填土、洪坡积层和砂泥岩互层,汉州路北段长1 390. 88 m,设计三种舱类;(2)汉州路北段管廊基坑最大开挖深度为9. 3 m,位置为K 0+40,管廊类型为两舱管廊,截面尺寸为7. 6 m×3. 8 m,宜采用两级放坡方式开挖,下级边坡高度5～6 m时整体稳定性最好,黏土区最优放坡坡率为1∶1. 5,全风化基岩区为1∶0. 75,中风化基岩区为1∶0. 3;(3)对于局部工程区不满足放坡条件者,建议采用锚杆支护,锚杆长度4～6 m、间距1～2 m可取得良好的支护效果;(4)本研究成果可为现代城市地下综合管廊的工程设计提供理论指导。     

Numerical Simulation of Focused Wave and Its Uncertainty Analysis

On the basis of the transient water wave (TWW) theory, focused wave is generated in the circulating water channel. Numerical simulation of the focused wave is carried out by solving the Reynolds averaged Navier-Stokes (RANS) equations. The dynamic grid technique is adopted to simulate the motion of the wave maker, and the volume of fluid (VOF) method is used to capture the free surface of the wave. The simulation results are compared with the measured data, and good agreement is obtained. For quantitative estimation of the numerical simulation error and uncertainty, the uncertainty analysis method recommended by the International Towing Tank Conference (ITTC) procedure is performed for the simulation results of the surface elevations at different positions. Both grid-convergence and time-step-size convergence studies are conducted using three types of grids and time step sizes. The simulation results are all monotonously convergent in the verification procedure, and the validations of the simulated surface elevations with the positions at 3.5, 4.0 and 4.5m are all achieved by comparing with the validation uncertainty. It is found that the numerical simulation errors caused by the grid and time-step-size in the convergence studies have the same order of magnitude. In addition, the numerical errors and uncertainties for the surface elevations at different positions are compared and discussed in detail. This paper presents the first attempt to carry out the uncertainty analysis of the simulation of focused wave, and the effectiveness of the proposed verification and validation procedures in the uncertainty analysis is demonstrated.     

Experimental Study on Ship-Bank Interaction of Very Large Crude Carrier in Shallow Water

In order to assess the influence of ship-bank interaction on ship manoeuvring motion, planar motion mechanism (PMM) tests on a scale model of the KRISO very large crude carrier (KVLCC2) are conducted in different water depths in circulating water channel (CWC). The asymmetric hydrodynamic derivatives are defined to characterize the bank effect, and they are measured through the straight towing test with varying lateral displacements. The linear and nonlinear hydrodynamic derivatives are determined from the test data of the Fourier integral and mathematical regression model. The rudder and heading angles required at equilibrium conditions in different ship-bank distances are calculated by the manoeuvring model. The directional stability with varying ship-bank distances is studied in terms of eigenvalue analysis. Analysis based on the test results shows that the KVLCC2 model ship appears inherently unstable for keeping course in deep and shallow water conditions. When the ship-bank distance decreases, the increasing ship-bank interaction can dramatically affect some parameters of the criteria for course keeping.     

预喷与后喷参数对柴油机排放影响的试验研究

为了探究预喷射与后喷射对柴油机尾气中有害物质的影响,通过高压共轨柴油机台架试验,在不同的预喷与后喷参数下对柴油机尾气中有害物质的排放进行测试.试验结果表明:针对柴油机进行燃油预喷射可有效抑制尾气中NOx的产生,但烟度值有所升高;加入燃油后喷射后,NOx与烟度值均呈现减小趋势;随着近后喷射燃油喷射量的增加,尾气中烟度值呈...     

采用小样本统计理论的隧道围岩分类

隧道围岩级别判断存在较多的不确定影响因素,特别是各影响因素的参数信息和样本资料有限,给判断工作造成了很大的困难。利用专为小样本统计分析而提出的支持向量机方法,在分析围岩级别划分的基础上,选取隧道围岩级别划分需要考虑的9个关键因素,将这9个因素作为输入参数,同时将围岩划分为5个等级作为输出参数,建立了围岩级别判断的小样本统计模型。利用该模型对二郎山隧道的围岩级别进行测试,并与ART1神经网络和BP神经网络的结果进行对比,表明将基于小样本统计的支持向量机理论用于围岩级别判断是可行的,并且具有很好的精度。