VIV and galloping of single circular cylinder with surface roughness at 3.0×10≤Re≤1.2×10     

Che-Chun Chang  Michael M. Bernitsas 《Ocean Engineering》2011,38(16):1713-1732

Passive Turbulence Control (PTC) in the form of selectively distributed surface roughness is used to alter Flow Induced Motion (FIM) of a circular cylinder in a steady flow. The objective is to enhance FIM's synchronization range and amplitude, thus maximizing conversion of hydrokinetic energy into mechanical energy by oscillator in vortex-induced vibration and/or galloping. Through additional viscous damping, mechanical energy is converted to electrical harnessing clean and renewable energy from ocean/river currents. High Reynolds numbers (Re) are required to reach the high-lift TrSL3 (Transition-Shear-Layer-3) flow regime. PTC trips flow separation and energizes the boundary layer, thus inducing higher vorticity and consequently lift. Roughness location, surface coverage, and size are studied using systematic model tests with broad-field laser visualization at 3.0×10⁴<Re<1.2×10⁵ in the low-turbulence free-surface water-channel of the Marine Renewable Energy Laboratory of the University of Michigan. Test results show that 16° roughness coverage is effective in the range (10°-80°) inducing reduced vortex-induced vibration (VIV), enhanced VIV, or galloping. Range of synchronization may increase or decrease, galloping amplitude of oscillation reaches three diameters; wake structures change dramatically reaching up to ten vortices per cycle. Conversion of hydrokinetic energy to mechanical is enhanced strongly with proper PTC.  相似文献   

基于水电比拟方法的山东南四湖上级湖流场研究          下载免费PDF全文

汪嘉宁  吕红民  江文胜 《海洋与湖沼》2011,42(2):324-329

利用水电比拟方法模拟了南四湖流场结构。同时,基于HAMSOM模式,对其流场进行了数值模拟,所得结果与水电比拟结果一致,两者平均相关系数在0.94以上,表明水电比拟实验技术路线可行,流场基本结构准确。该方法适用于低流速大流场的模拟。流场结构分析表明,湖区流速在汛期为cm/s量级,非汛期仅为mm/s量级。其中,在南阳湖北部...  相似文献   

New model to determine forces at on-bottom slender pipelines     

Francesco Aristodemo  Giuseppe Roberto Tomasicchio  Paolo Veltri 《Coastal Engineering》2011

The present paper proposes a numerical model to determine horizontal and vertical components of the hydrodynamic forces on a slender submarine pipeline lying at the sea bed and exposed to non-linear waves plus a current. The new model is an extension of the Wake II type model, originally proposed for sinusoidal waves (Soedigdo et al., 1999) and for combined sinusoidal waves and currents (Sabag et al., 2000), to the case of periodic or random waves, even with a superimposed current. The Wake II type model takes into account the wake effects on the kinematic field and the time variation of drag and lift hydrodynamic coefficients. The proposed extension is based on an evolutional analysis carried out for each half period of the free stream horizontal velocity at the pipeline. An analytical expression of the wake velocity is developed starting from the Navier–Stokes and the boundary layer equations. The time variation of the drag and lift hydrodynamic coefficients is obtained using a Gaussian integration of the start-up function. A reduced scale laboratory investigation in a large wave flume has been conducted in order to calibrate the empirical parameters involved in the proposed model. Different wave and current conditions have been considered and measurements of free stream horizontal velocities and dynamic pressures on a bottom-mounted pipeline have been conducted. The comparison between experimental and numerical hydrodynamic forces shows the accuracy of the new model in evaluating the time variation of peaks and phase shifts of the horizontal and vertical wave and current induced forces.  相似文献   

阿拉善宗乃山岩体东南缘花岗岩LA-ICP-MS锆石U-Pb年龄与地球化学特征   总被引：2，自引：0，他引：2  

谢奋全  王黎栋  李琦  石朝霞  陈学兵  韦岸 《岩矿测试》2015,34(3):375-382

阿拉善宗乃山岩体东南缘分布多种类型的花岗岩,本文主要采用岩相学、激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)锆石U-Pb定年、岩石地球化学等技术手段,对宗乃山岩体东南缘岩石类型、年代学、源岩特征以及构造背景进行了研究。结果表明:岩石类型主要为碱性-钙碱性准铝质花岗岩和闪长岩;单颗粒锆石分析获得黑云母斜长花岗岩年龄为236.8±1.9 Ma~249.7±2.6 Ma,片麻状花岗岩年龄为268.1±1.1 Ma,岩体成岩时期主要为华力西晚期和印支期早期,具有多期侵入的特征。该岩体岩石源岩为I型花岗岩,源于地壳火山弧区和同碰撞区,表明由于洋壳俯冲作用,在宗乃山东南缘形成了岛弧花岗岩侵入体。LA-ICP-MS锆石U-Pb定年技术为洋壳俯冲提供了年代学约束,确定了研究区碰撞时间为早于236.8±1.9 Ma。  相似文献   

人工阶梯-深潭破坏案例与稳定性分析          下载免费PDF全文

李志威  王兆印  张晨笛  余国安  张康  漆力健 《水科学进展》2015,26(6):820-828

通过2006—2010年4个修建人工阶梯-深潭系统的治理山区河流案例,总结其治理效果和最终破坏原因.以单个阶梯为分析对象,给出其受力表达式,建立单个阶梯-深潭的简化稳定性模型,进而分析来流量和冲刷角变化对其稳定性的影响.单个阶梯的稳定性取决于关键石块粒径、河道坡降、流量和冲刷角.洪水期的洪峰流量和阶梯下游冲刷是阶梯破坏的主要原因,上游来流量增加和冲刷角越大,阶梯越易发生破坏.人工阶梯-深潭系统在洪水期的稳定性是其发挥长期治理效果的关键.  相似文献   

某铅锌尾矿库对地下水环境影响及防治措施   总被引：1，自引：0，他引：1  

任旭 《地下水》2015,(2)

铅锌尾矿的浸出液中含有重金属等对地下水环境有重要影响的污染因子。利用地下水数值模拟专业软件GMS,结合研究区水文地质条件,对不同工况下地下水环境的影响程度及范围进行模拟计算。结果表明,达到Ⅱ类工业固体废弃物处置场规定的防渗要求条件下,尾矿库运行浸出液下渗量有限(2.8 m3/d),并不会使区域地下水超出《地下水质量标准》Ⅲ类标准,而防渗层仅出现10%破损时,浸出液下渗量为(97.22 m3/d),使地下水下游方向50 m内地下水中Pb超出Ⅲ类标准,超标范围约0.0375 km2。反映出该类处置场中的防渗措施是对地下水环境保护的重要保证。  相似文献   

日喀则蛇绿岩研究中的几个问题   总被引：6，自引：4，他引：2  

张旗 《岩石学报》2015,31(1):37-46

日喀则蛇绿岩是中国最著名的蛇绿岩,但是,许多问题存在争论,许多现象没有搞清楚。文中讨论了日喀则蛇绿岩中一些重要的现象以及对目前发现的许多矛盾如何考虑的问题。例如,(1)日喀则蛇绿岩中是否存在席状岩墙群?是否存在席状岩床群?本文认为,席状岩墙群应当是存在的,因为有不对称冷凝边出现。而席状岩床群可能是有问题的,岩床作为侵入体可以出现在许多地方,但是,蛇绿岩中不可能出现席状岩床群,尤其还把它作为蛇绿岩岩石组合的一个单元。笔者认为,所谓的席状岩床群可能是席状岩流群,它不是一个独立的单元,是玄武岩单元下部的成员。(2)日喀则蛇绿岩是否统统是蛇绿岩是一个需要考虑的问题,雅鲁藏布江东西两段出现的岩石组合及其产出背景与日喀则地区的蛇绿岩明显不同,其中有些可能未必是蛇绿岩。(3)自1972年彭罗斯会议以来,蛇绿岩研究发展到现在,可能已经进入了一个关键时期。文中回顾了蛇绿岩的定义及其构造意义,指出1972年彭罗斯会议关于蛇绿岩的定义仍然是适用的。蛇绿岩可以概括为洋壳+地幔,这个洋壳来自板块扩张脊,是年轻的;这个地幔是大洋岩石圈地幔,也可能保留有古老岩石圈地幔的印记。蛇绿岩产于板块扩张脊,这是蛇绿岩构造含义的唯一解,蛇绿岩不存在多解性。(4)日喀则蛇绿岩的许多基本观点主要是法国学者提出来的,如关于岩床群的见解,慢速扩张的见解等。但是,上述见解是否都是对的是需要思考的。日喀则蛇绿岩具有得天独厚的条件,我们应当很好利用这个条件,努力把我们的研究做好,为全球蛇绿岩研究贡献我们的一份力量。  相似文献   

基于 DEM 对喀斯特地貌山地及水系信息的提取--以桂林阳朔县为例   总被引：1，自引：0，他引：1  

李飞  杨小平  郝红科 《测绘与空间地理信息》2015,(8):73-76

以30 m分辨率的SRTM－DEM数据为基础,通过GIS的空间分析功能,首先对数据进行坡度分析,通过坡度分级法将山地与平原划分,自动提取出山地的信息,再运用碎斑处理结合TM影像对结果进行修正;其次,在ArcGIS的水文分析（ Hydrology）模块下对 DEM进行数字地形分析,提取流域特征。经分析得到了研究区域的山地及河网特征信息,并与实际地形及河流水系大致吻合,改进了传统手工和野外调查为主的提取方法,初步实现了山地、水系信息的自动提取,为研究区域社会经济更好更快地发展具有一定的参考意义。  相似文献   

高山地区地形对重力测量的影响分析     

邓文彬  阿力甫·努尔买买提 《测绘科学》2015,40(7):3-7

针对高山地区地形改正研究的不足,文章以青藏高原为实例,利用快速傅里叶变换详细讨论了高山地区地形改正中质量柱模型与质量线模型对重力测量的影响。研究结果表明:青藏高原地区,地形对重力测量的影响达到毫伽量级;采用快速傅里叶变换计算地形改正时,其最佳计算阶数应为二阶;高山地区,采用质量柱模型与质量线模型进行地形改正的差异为0.1mGal量级。  相似文献   

Applying landscape-ecological concept and GIS modelling for assessing and mapping of ecological situation of mountainous landscapes (on the case of Syunik marz,Armenia)     

V.S. Muradyan  Sh.G. Asmaryan 《国际地球制图》2015,30(10):1077-1091

Regional landscape-ecological studies have acquired a special topicality as they assure efficient environmental conservation and sustainable use of natural resources. A landscape-ecological analysis was performed based on four basic integral indices: (1) ecological potential, (2) ecological stability, (3) ecological load and (4) ecological tension. The values of basic integral indices of the landscape-ecological analysis were calculated as sums of respective factors expressed in scores and multiplied by their significance reflecting coefficients. In agreement with that rule, a formula was derived of calculation of basic indices of landscape-ecological analysis. Subsequently, those factors were integrated by ‘Model Builder’ in ArcGIS applying ‘Weighted Sum’ functions. Finally, through geographic information systems modelling, maps of basic indices of landscape-ecological analysis were produced. In conclusion – ecological potential, stability, load and tension are best indicators for the assessment of the landscape-ecological situation of the studied territory.  相似文献