CFD simulation of propeller and rudder performance when using additional thrust fins

To analyse a possible way to improve the propulsion performance of ships,the unstructured grid and the Reynolds Average Navier-Stokes equations were used to calculate the performance of a propeller and rudder fitted with additional thrust fins in the viscous flow field.The computational fluid dynamics software FLUENT was used to simulate the thrust and torque coefficient as a function of the advance coefficient of propeller and the thrust efficiency of additional thrust fins. The pressure and velocity flow behind the propeller was calculated. The geometrical nodes of the propeller were constituted by FORTRAN program and the NUMBS method was used to create a configuration of the propeller,which was then used by GAMMBIT to generate the calculation model. The thrust efficiency of fins was calculated as a function of the number of additional fins and the attack angles. The results of the calculations agree fairly well with experimental data,which shows that the viscous flow solution we present is useful in simulating the performance of propellers and rudders with additional fins.     

基于Flexsim的混流生产线生产顺序仿真

阐述了混流生产线的生产顺序问题。基于Flexsim对某订单需求下混流生产线不同生产顺序进行仿真。简要介绍了Flexsim在混流生产线建模仿真过程中的基本步骤和关键技术。通过对仿真结果的分析,得出该订单需求下合理的生产顺序。     

螺旋气门的结构优化及对无节气门汽油机燃烧性能的影响

由于进气方式的改变,气道喷射式无节气门汽油机中小负荷时泵气损失显著降低,但燃烧性能却明显恶化.为改善其燃烧性能,本文中设计了一种在进气过程中能产生较强进气涡流的螺旋气门,并使用仿真软件STAR-CCM+对螺旋气门的主要结构参数进行了优化.在稳流气道试验台上测量其进气涡流比和流量系数,证明该螺旋气门在开启升程较小时能产生...     

GB 38900-2020机动车安全技术检验项目和方法解析

文章总结了GB38900-2020与GB21861-2014、GB 18565-2016关于车辆安全技术检验项目和方法上的主要差异。包括标准名称、检验方法、检验要求、结果判定、检验项目等,希望能为相关人员提供参考。     

新能源汽车消费者充电行为习惯及配套设施使用现状分析

文章主要研究新能源汽车消费者充电习惯和行为特征,并探索不同城市级别、不同意识形态和不同充电设施消费者充电行为差异性。通过分析和对比,挖掘不同新能源汽车消费者充电特点,以及在充电过程中的主要困难和不便,一方面为新能源汽车企业了解消费者充电行为提供参考,另一方面为充电设施的完善和改进提供方向。此外,在分析消费者充电现状的同时,还进一步了解其对充电配套设施的需求和期望,为未来充电设施布局指明方向。     

高铁夕发朝至列车开行与天窗设置协同优化

高速铁路夕发朝至列车开行与天窗设置存在动态影响关系,将两者进行协同优化有助于满足旅客夜间出行需求,提升铁路运力资源配置.?以通道型高速铁路为对象,在分析高速铁路夕发朝至列车与天窗设置影响关系的基础上,以高速铁路夕发朝至列车总的旅行时间最少和高速铁路夕发朝至列车的开行对既有列车运行图的影响最小为目标,建立了列车开行模式未...     

Using satellite observations of ocean color to categorize the dispersal patterns of river-borne substances in the Gaoping (Kaoping) River, Shelf and Canyon system

Mapping the water constituents from remotely sensed ocean color data enables a better understanding of the dispersal patterns of river-borne substances in the Gaoping (formerly spelled Kaoping) River, Shelf and Canyon (KPRSC) system. Based on twelve MODIS-Aqua images in the KPRSC region taken in 2005, we apply a newly developed GA-SA approach to derive maps of chlorophyll-a concentration (Chl-a), colored dissolved organic matter (CDOM) and non-algal particle/detritus/mineral (NAP). The results demonstrated that the different characteristics of Chl-a, CDOM and NAP make them ideal tracers for observing large-scale dispersal patterns. With ancillary information of averaged daily precipitation, the daily wind field obtained from QuikSCAT (Quick Scatterometer), and the 8-day composite of the temperature field obtained from MODIS-Aqua, we categorized the surface dispersal patterns as coastal, northwestward and frontal patterns. Also, for the first time, we observed a sudden increase of biomass on a large scale from a pair of ocean color images taken over only a 2-day interval. Another remarkable feature is the interaction between the southeastward flow and the intrusion of the Kuroshio Branch, resulting in complicated patterns with various scales of vortex structures and current fronts. The observed features could be used for model validation of the flow field of the KPRSC system.     

Comparison between a reanalyzed product by 3-dimensional variational assimilation technique and observations in the Ulleung Basin of the East/Japan Sea

Reanalyzed products from a MOM3-based East Sea Regional Ocean Model with a 3-dimentional variational data assimilation module (DA-ESROM), have been compared with the observed hydrographic and current datasets in the Ulleung Basin (UB) of the East/Japan Sea (EJS). Satellite-borne sea surface temperature and sea surface height data, and in-situ temperature profiles have been assimilated into the DA-ESROM. The performance of the DA-ESROM appears to be efficient enough to be used in an operational ocean forecast system.Comparing with the results from Mitchell et al. [Mitchell, D. A., Watts, D. R., Wimbush, M., Teague, W.J., Tracey, K. L., Book, J. W., Chang, K.-I., Suk, M.-S., Yoon, J.-H., 2005a. Upper circulation patterns in the Ulleung Basin. Deep-Sea Res. II, 52, 1617-1638.], the DA-ESROM fairly well simulates the high variability of the Ulleung Warm Eddy and Dok Cold Eddy as well as the branching of the Tsushima Warm Current in the UB. The overall root-mean-square error between 100 m temperature field reproduced by the DA-ESROM and the observed 100-dbar temperature field is 2.1 °C, and the spatially averaged grid-to-grid correlation between the two temperature fields is high with a mean value of 0.79 for the inter-comparison period.The DA-ESROM reproduces the development of strong southward North Korean Cold Current (NKCC) in summer consistent with the observational results, which is thought to be an improvement of the previous numerical models in the EJS. The reanalyzed products show that the NKCC is about 35 km wide, and flows southward along the Korean coast from spring to summer with maximum monthly mean volume transport of about 0.8 Sv in August–September.     

基于fluent的大中型永磁电机端部流场和温度场计算

基于CFD流体计算软件fluent,对大型永磁电机定子端部通风结构和流动区域进行了分析,确定了三维流体场的求解域,建立了包括散热器和风扇在内的定子端部模型,给出了求解域内的边界条件并且进行了计算和分析;优化了通风结构。得到了端部温度场的分布规律,该结果对电机设计人员的通风通风系统和绝缘结构的设计提供了理论依据。     

模糊专家系统在舰艇无源干扰中的应用研究

针对现代海战特点,提出了一种基于模糊专家系统的舰艇无源干扰系统结构,详细地阐述了舰艇无源干扰系统的体系结构和工作过程,充分利用专家经验和干扰方式数学模型,体现了定性分析与定量计算的特点.该研究对未来海战中干扰设备的布放决策具有一定的指导意义.