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Search Results: 1 - 10 of 10237 matches for " 亚临界雷诺数 "
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亚临界区雷诺数下圆柱绕流场电磁力控制数值研究
尹纪富,尤云祥,李巍
海洋工程 , 2014,
Abstract: 在亚临界区雷诺数下,采用脱体涡模拟方法对弱电解质中电磁力作用下圆柱绕流场及其升阻力特性进行了数值模拟与分析。结果表明,电磁力可以提高圆柱体边界层内的流体动能,延缓圆柱体近壁面流动分离,减弱绕流场中流向和展向大尺度涡的强度,减小圆柱体阻力及其升力脉动幅值;当电磁力作用参数大于某个临界值后,流动分离角消失,在圆柱体尾部产生射流现象,电磁力产生净推力作用,出现负阻力现象,而且升力脉动幅值显著减小且接近于零。
Re=3 900圆柱绕流的三维大涡模拟
战庆亮,周志勇,葛耀君
哈尔滨工业大学学报 , 2015, DOI: 10.11918/j.issn.0367-6234.2015.12.013
Abstract: 为研究亚临界雷诺数范围内圆柱绕流流场特性及三维大涡模拟方法的适用性,基于C++语言及有限体积法开发了三维非结构化网格的大涡模拟计算程序.采用新的高稳定性高精度二阶离散格式,及Smagorinsky亚格子模型对Re=3900均匀来流条件下的圆柱绕流问题进行数值模拟,并统计获得了平均流场参数及湍流流场的详细结构特性.结果表明:采用本文的网格、计算步长和高稳定性二阶离散精度大涡模拟方法计算所得的湍流场一阶统计特性和二阶统计特性与实验值吻合很好.验证了大涡模拟程序在模拟亚临界雷诺数下圆柱绕流流场平均值及脉动值的合理性.
圆柱尾流的绝对不稳定性
邵传平,鄂学全,王薇
力学学报 , 1999, DOI: 10.6052/0459-1879-1999-1-1999-001
Abstract: 在水槽和低湍流度水洞中进行亚临界雷诺数圆柱尾流稳定性实验来流速度由零缓慢增长到一定值后保持不变,稳定足够长时间后,在流向某站位处给流场一个有限幅值的脉冲扰动,测量扰动前后相当长时间内下游尾流速度信号的变化情况当雷诺数处于高亚临界值时,未受扰动的尾流速度脉动很小,处于定常状态,但对近尾流进行脉冲扰动后,能够激发出不衰减的旋涡脱落发现扰动位置限制在圆柱后一定范围内才能有效,再往下游则扰动随时间衰减.说明圆柱近尾流中存在一个绝对不稳定区,在该区域内的扰动将在当地放大,经过复杂的演化,最后形成不衰减的旋涡脱落.
改进SST湍流模型在分离流中的应用
康庄,倪问池,孙丽萍
哈尔滨工程大学学报 , 2017, DOI: 10.11990/jheu.201606063
Abstract: 针对标准SST模型无法对分离流动进行准确的数值模拟的问题,本文根据分离流动的特性,在传统SST模型的基础上增加了能量传递耗散项,提升了该模型对分离流动的模拟精度。以开源软件OpenFOAM为平台,运用改进的SST湍流模型,对亚临界雷诺数情况下的圆柱绕流算例进行计算,并结合已有的实验结果,与原始SST模型的计算结果进行对比。结果证明:改进的SST模型能有效弥补原始SST模型在模拟分离流时,漩涡脱落强度偏小的缺陷,对于亚临界雷诺数下的分离流动的数值模拟具有良好效果。
ABSOLUTE INSTABILITY IN CRICULAR CYLINDER WAKES
圆柱尾流的绝对不稳定性

Shao Chuanping,E Xuequan,Wang Wei,
邵传平
,鄂学全,王薇

力学学报 , 1999,
Abstract: The stability of circular cylinder wake at low Reynolds numbers has been studied experimently. The experiments were separatly carried out in a propeller-driven water channel and in a gravity-driven low turbulence water tunnel. The test section of water channel was 15 cm in width, 10cm in depth and 100 cm in length, and the test section of water tunnel was 4 cm in width.10cm in height and 100 cm in length. The cylinder model used in channel and tunnel were 15 cm long, 0.2 cm in diameter and 4cm long, 1 cm in diameter respectively. The model cylinder was placed horizentally across the test section, both ends in close contact with the vertical walls of the test section. Turbulence intensity of the oncoming flow. was 0.8% in channel and 0.25% in tunnel.The apparatus used both in water channel and water tunnel that applied disturbances to wake flow field was made up of a thin tube, a cylindric container, a round thin aluminium plate and an elastic membrane. The thin tube made of stainless steel, outer diameter 0.12cm, inner diameter 0.08cm, was in inserted into the water tunnel from above, perpendiculely penetrating through the upper wall. The end of the steel tube was less than 0.5 cm deep in water so that no disturbances were imposed to the wake flow by the tube. The end out of the tunnel was connected to the container. The container was sealed by the elastic membrane at the upper end. The round plate, with diameter slightly smaller than the inner diameter of the container, was glued to the elastic membrane, forming a plate that could move up and down in the container. Water from the tunnel filled the container and it was kept at appropriate height to keep the membrane in equilibrium. When an impulsive force was applied upon the membrane, an impulse jet from the thin tube entered the flow field, imposing a disturbance to the wake, then water was sucked back into the container, the membrane backed to the equilibrium. It was tested that one impulse force could cause just one impulse jet, the second time disturbing never appeared. In the test, velocity of the oncoming flow was slowly increased from zero to a certain value and then kept constant there to allow the flow to stabilize. An impulse disturbance was applied to the cylinder wake at some point and the downstream velocity was recorded in long periods before and after the disturbance by a hot film probe located at a point 26 diameters downstream the cylinder.When the Reynolds number is smaller than the critical one, fluctuation of the undisturbed wake velocity is very small. But disturbances applied to the near wake excite vortex shedding that does not decay. It is observed that the disturbance applied must be within certain range behind the cylinder, otherwise, when the disturbance applied to a point some distance downstream that range, it decays. The experimental results indicate that there is an absolutely unstable zone in the near wake. Disturbances within the zone locally amplify and spread,
亚临界雷诺数圆柱绕流远场气动噪声实验研究
Far-field aeroacoustic experimental study of flow around a circular cylinder at subcritical Reynolds number

李玲,刘沛清,邢宇,郭昊,田云
- , 2016, DOI: 10.13700/j.bh.1001-5965.2015.0364
Abstract: 摘要 针对亚临界雷诺数下圆柱绕流的气动噪声问题,在北京航空航天大学D5气动声学风洞中进行了圆柱绕流远场气动噪声的实验研究。在D5气动声学风洞实验段不同来流条件下,测量消声室中距离圆柱不同位置的自由场传声器的远场声压信号,经过快速傅里叶变换(FFT)获得亚临界雷诺数下圆柱绕流气动噪声随来流速度、接收点距离的变化规律。实验结果表明:圆柱绕流的远场气动噪声在垂直气流方向最大,随着偏离垂直方向角度的增大噪声逐渐减小,属于典型的偶极子噪声源辐射特性;远场气动噪声近似与来流速度的6次方成正比,与接收点到圆柱中心距离的2次方成反比,这说明偶极子类型的噪声源是圆柱绕流的主要噪声源。
Abstract:To study the aeroacoustics of the flow around a circular cylinder at subcritical Reynolds number, the experimental investigation of far-field aerodynamic noise generated from flow past a circular cylinder was carried out in D5 aeroacoustic wind tunnel at Beihang University. Under variable flow conditions in the D5 test section, the signal of the sound pressure obtained from the free-field microphones at different positions in the anechoic chamber was measured. The dependence of far-field noise on free stream velocity and receiver position was acquired with the fast Fourier transform(FFT). With the qualitative and quantitative analysis of the aeroacoustic characteristics, the experimental results validate that the noise emitted from the circular cylinder is the largest in the direction vertical to the flow and decreases with the angle increasing, belonging to the characteristics of the sound radiated from a dipole sound source. The far-field aerodynamic noise generated from the cylinder is proportional to the sixth power of flow speed and inversely proportional to the twice power of the distance between the receiver and the center of the circular cylinder, confirming the domination of the dipolar noise source.
建立微尺度蒸发冷凝的通用准则
吴赞,李蔚
工程热物理学报 , 2011,
Abstract: 蒸发冷却模式以及微换热器,是最具有潜力的冷却高热流密度电子器件的方法之一。总结和研究微尺度蒸发冷凝相变机理,是本文研究目的。我们在参阅大量文献和提取大量精确数据的基础上,发现了新的区分常规通道与微通道的临界准则Bo×Re10.5=200;在此基础上,我们归纳出了新的预测微通道压降、传热系数和临界热流量的关联式,与以前的关联式相比,新的关联式能更好地预测微通道数据。
圆形断面在35k~330k雷诺数范围的气动力特性研究
马文勇,袁欣欣,张晓斌,尉耀元,刘庆宽
工程力学 , 2015, DOI: 10.6052/j.issn.1000-4750.2014.05.S022
Abstract: 圆形断面是土木工程中最常见的断面形状之一,圆形断面的细长结构常发生风致大幅振动,雷诺数是影响该类断面结构气动力的重要参数之一。采用刚性模型测压风洞试验,通过气动力系数、风压分布、流动特征点和漩涡脱落频率的分析,给出索结构在雷诺数35k~330k范围内的气动力特点及其产生机理。与亚临界区相比,在临界雷诺数区,平均风压系数零点、最小平均风压系数点和分离点向尾流区移动,圆柱断面两侧流动状态不对称,平均阻力系数下降,出现非零的平均升力系数,规则的漩涡脱落消失。
人工糙管中流动状态转变
戴干策,王归仁,范自晖
华东理工大学学报 , 1989,
Abstract: 以压降法、压力脉动法、速度脉动法测定了横肋管中的临界雷诺数Re_C。当峰高k/d为0.01~0.06,间距s/k为7~40时,其值为850~2100。在流动稳定性理论的基础上探讨了峰高、间距及初始扰动等因素对Re_C的影响。
准周期性磁结构的形成过程及其特征的数值分析
金曙平,周鸿松
地球物理学报 , 1995,
Abstract: 在入流马赫数MA为0.1-0.4范围内,选取不同的入流,逐一考察在可压缩导电介质中磁场重联的类型随磁雷诺数Rm的变化.大量的数值结果表明:在不同入流驱动下,磁雷诺数(Rm)均有临界值存在,如果等离子体系统逐渐趋于稳定的单X线重联;若间歇性的次级撕裂产生了重复出现的磁结构,而且Ma越大产生间歇性次级撕裂的临界值越高,与MA之间基本上符合线性关系.此外还发现,当多重X线重联间歇性地出现时,有关物理量发生准周期性地振荡.
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