不同湍流模型下圆柱涡激振动的计算比较

为应用计算流体力学的方法模拟圆柱体的涡激振动问题,文章采用有限体积法结合两种不同的湍流模型（RNG k-ε和SST k-ω湍流模型）求解时间平均的纳维尔-斯托克斯方程（RANS）,对低质量比弹性支撑的刚性圆柱体在均匀来流中的的涡激振动问题进行了研究。计算对象参照Govardhan和Williamson的物理模型实验中的参数,通过比较两种湍流模型下圆柱体的振幅响应、频率响应及三个响应分支的水动力系数和尾涡模式,分析了两种湍流模型模拟结果的差异及原因,结果表明：RNG k-ε湍流模型和SST k-ω湍流模型的模拟结果差异很大,不论在振幅响应和频率响应上的计算上,还是对升力的谱分析上,SST k-ω模型的计算结果都更接近于真实的物理现象,并且采用SST k-ω湍流模型成功地模拟出了2P模式。因此从整体上说,SST k-ω湍流模型的模拟效果要优于RNG k-ε湍流模型。     

Campus parking supply impacts on transportation mode choice

Parking demand is a significant land-use problem in campus planning. The parking policies of universities and large corporations with facilities located in small urban areas shape the character of their campuses. These facilities will benefit from a simplified methodology to study the effects of parking availability on transportation mode mix and impacts on recruitment and staffing policies. This paper, based on a case study of North Dakota State University in the United States, introduces an analytical framework to provide planners with insights about how parking supply and demand affects campus transportation mode choice. The methodology relies only on aggregate mode choice data for the special generator zone and the average aggregate volume/capacity ratio projections for all external routes that access the zone. This reduced data requirement significantly lowers analysis cost and obviates the need for specialized modelling software and spatial network analysis tools. Results illustrate that the framework is effective for analysing mode choice changes under different scenarios of parking supply and population growth.     

无梢涡螺旋桨试验研究

本文根据螺旋桨的升力线理论,分析了螺旋桨叶梢产生梢涡的机理,通过在叶梢处的截面上安装一个与螺旋桨同轴旋转面相切的弧面封板所进行的螺旋桨敞水试验,来验证叶梢安装叶片可使叶梢不产生旋涡,减少叶梢处能量损失,得出了初步的结论。     

某型汽轮发电机组公共底座模态分析及试验

对某船用汽轮发电机组公共底座进行了模态仿真分析,并进行了模态测试。测试结果与仿真分析结果达到了吻合,说明公共底座有限元建模方法可行,有限元模型满足工程精度要求,这为进一步分析整体汽轮发电机组动力特性奠定了基础。     

12 500 DWT重吊多用途船总体设计研究

12 500 DWT多用途船是上海船舶研究设计院为德国船东开发设计的重吊多用途船。满足EEDI、压载水处理、拆船公约等最新的国际规范和环保要求,配备重型起货设备,拥有超长货舱、超大甲板面积,主要用于装运大型工程设备、重货、集装箱、干散货、谷物及危险品等。在总体布置、破舱稳性、主推进装置和节能环保措施等方面进行了研究。该船采用先进的主推进装置,选用超长两冲程G型电喷主机,配隧道式齿轮箱和轴带发电机,定距螺旋桨推进,燃油经济性优秀。     

波浪入射角度对立柱周围波面扰动特性的影响研究

基于N-S方程和连续性方程建立了三维数值波浪水池,并在该水池内对固定直立柱在不同浪向下的波浪爬升和绕射问题进行了数值模拟。为了验证数值计算的准确性,对立柱近壁面处的波浪爬升效应展开了模型试验研究,计算值与试验值吻合较好,证明了该方法的可行性。研究了入射角度的变化对立柱周围波浪爬升幅度和非线性特征的影响,同时从垂直浪向的投影面积和相对浪向的投影面形状这两个因素出发,探讨了不同浪向角下立柱周围的波浪叠加、波面放大率以及二次波峰效应,并对自由面漩涡生成特性进行了较为深入的机理性研究,可为今后进一步研究不同的入射角度下,复杂的海洋结构物周围的波浪非线性效应提供有价值的参考。     

蛇形造波机设计参数的确定

利用势函数理论计算了推波板的最大行程、单元最大负载力和负载功率。计算结果与多年来的实践经验接近。且从造波机研制完成后的性能测试结果来看,亦与预期值符合甚好。     

通过水下储能系统的蓄电池单元的流:三个接触的似花结构的球状物(英文)

An LES simulation of flow over an accumulator unit of an underwater compressed air energy storage facility was conducted. The accumulator unit consists of three touching underwater balloons arranged in a floral configuration. The structure of the flow was examined via three dimensional iso surfaces of the Q criterion. Vortical cores were observed on the leeward surface of the balloons. The swirling tube flows generated by these vortical cores were depicted through three dimensional path lines. The flow dynamics were visualized via time series snapshots of two dimensional vorticity contours perpendicular to the flow direction; revealing the turbulent swinging motions of the aforementioned shedding-swirling tube flows. The time history of the hydrodynamic loading was presented in terms of lift and drag coefficients. Drag coefficient of each individual balloon in the floral configuration was smaller than that of a single balloon. It was found that the total drag coefficient of the floral unit of three touching balloons, i.e. summation of the drag coefficients of the balloons, is not too much larger than that of a single balloon whereas it provides three times the storage capacity. In addition to its practical significance in designing appropriate foundation and supports, the instantaneous hydrodynamic loading was used to determine the frequency of the turbulent swirling-swinging motions of the shedding vortex tubes; the Strouhal number was found to be larger than that of a single sphere at the same Reynolds number.     

旋转轴超声导波激励信号发生器的研制

介绍了一种超声导波激励信号发生器的设计方法,选择扭转模态的超声导波为发生对象,通过导波分析确定设计的导波频率,并根据所需信号的特点进行设计．采用ATmega32,AD9851和DAC0832进行硬件设计并调试系统．仿真及结果表明此方法可行．     

船舶应急电站的作用及应用

本文简单地介绍船舶应急电源的作用、类型及其规范要求,并分析应急电站在船舶中的运用及操作流程。举例介绍使用康明斯柴油应急发电机和蓄电池组作为大小应急电源,并搭配JRCS应急配电板、充放电板组成应急电站。详细分析应急电站的使用条件、转换过程及操作。