圆柱流致振动数值模拟及其机理研究

发布时间：2018-08-26 21:31

【摘要】：圆柱体的流致振动问题广泛存在于机械工程、海洋工程等诸多领域,然而圆柱(群)流致振动问题及其复杂,虽然经过数十年的研究,学术界对此问题仍未达到深刻。开展圆柱(群)流致振动的研究,深入理解圆柱间的相互作用,准确预报圆柱(群)响应特性,不仅具有重要的学术价值,对于提高VIVACE海流能利用装置的能量转化系数也具有重要的工程应用价值。本文对圆柱(群)流致振动开展了数值模拟研究,旨在深入理解圆柱(群)流致振动的机理。本文追踪了国内外有关圆柱流致振动的研究动向,对一系列热点问题开展了全面、深入的研究。内容包括单圆柱涡激振动、串列和并列双圆柱流致振动以及正方形排列四圆柱流致振动。论文系统总结了圆柱(群)流致振动的响应和尾流特性变化规律,研究与讨论了间距比对圆柱(群)流致振动的影响以及相邻圆柱间的耦合机制,深度剖析了圆柱(群)流致振动中出现的新现象,及其背后的物理本质和机理。通过研究本文得到了如下有价值的结论：1、单圆柱涡激振动中,流向振动对横向振动的影响主要存在于锁定区间。当折合流速Ur≥8.0时,圆柱涡激振动的阻力均值小于圆柱绕流的阻力均值,这是由于涡激振动时脱落旋涡离圆柱底部更远,以及升力和位移之间相位差发生180跳跃两方面原因造成的。2、间距比为s/D=2.5并列双圆柱流致振动中首次发现了两圆柱振动不对称和新迟滞现象。进一步的研究发现,当阻流比B≥0.08时,不对称区间和新迟滞现象均消失。3、并列双圆柱流致振动(s/D=2.5和s/D=5.0)中出现了8种不同的尾流模式,分别为不规律模式、同相同步、反相同步、偏斜反相同步、同相FF、长周期同相FF、异相FF和混合模式。4、间距比为s/D=1.5串列双圆柱间的耦合机制明显不同于间距比s/D=3.0和s/D=5.0时的情况。当间距比s/D≥3.0以后,上游圆柱的响应开始与单圆柱涡激振动相似,但在其下端分支和非同步区域之间的过渡区间并未出现迟滞现象,说明了下游圆柱对上游圆柱的影响要比传统观点认为的显著。与间距比s/D=1.5和s/D=5.0时两圆柱的响应出现迟滞现象不同,间距比s/D=3.0的流致振动中并未出现迟滞现象。5、正方形排列(s/D=5.0)四圆柱流致振动中,上游两圆柱的最大振幅相同,均为Ymax/D=0.56,与单圆柱涡激振动振幅接近。下游两圆柱的最大振幅不同,分别为Ymax/D=1.01和Ymax/D=0.997,分别比单圆柱涡激振动振幅增大了77.2%和74.8%。6、正方形排列(s/D=5.0)四圆柱流致振动中各圆柱响应均出现了三个不对称区间,分别为第一不对称区间(Ur=4.7～6.07)、第二不对称区间(Ur=6.9～7.2)和第三不对称区间(Ur=10.5～50.0)。进入不对称区间以后,尾流呈现出类似于并列双圆柱流致振动中出现的宽、窄尾流现象。随着折合流速的增加,两圆柱振幅差距减小,尾流宽度差距也缩小。总之,本文从单圆柱涡激振动入手,研究了单圆柱涡激振动的基本规律；并进一步模拟了串列和并列双圆柱流致振动,分析了关键参数对振动响应的影响以及振动现象背后的物理本质和机理；初步开展了正方形排列四圆柱流致振动的数值模拟,分析了基本的流致响应、振动特性、尾流模式,揭示了圆柱流致响应中的相互作用机制。本文的创新性成果为深刻认识圆柱(群)流致振动现象和机理提供了有学术价值的参考。
[Abstract]:The problem of flow-induced vibration of cylinders exists widely in mechanical engineering, marine engineering and many other fields. However, the problem of flow-induced vibration of cylinders (groups) and its complexity have not yet reached a deep level in academia after decades of research. The study of flow-induced vibration of cylinders (groups) has been carried out to deeply understand the interaction between cylinders and accurately predict the interaction between cylinders. (group) response characteristics, not only have important academic value, but also have important engineering application value for improving the energy conversion coefficient of VIVACE current energy utilization device. In this paper, numerical simulation of cylindrical (group) flow-induced vibration is carried out to understand the mechanism of cylindrical (group) flow-induced vibration. In this paper, the response and wake characteristics of flow-induced vibration of cylinders (groups) are systematically summarized, and the spacing between cylinders is studied and discussed. By comparing the effects of flow-induced vibration of cylinders (groups) and the coupling mechanism between adjacent cylinders, the new phenomena in flow-induced vibration of cylinders (groups) and the physical essence and mechanism behind them are analyzed in depth. When the velocity Ur is greater than 8.0, the mean drag of vortex-induced vibration is smaller than that of the flow around the cylinder. This is due to the fact that the vortex shedding is farther away from the bottom of the cylinder and the 180 jumps of the phase difference between the lift and displacement. 2. The spacing ratio is s/D=2.5. The asymmetry and new hysteresis phenomena of the two cylinders are found for the first time. Further studies show that the asymmetry region and new hysteresis phenomena disappear when the blocking ratio B is greater than 0.08. Eight different wake modes appear in the flow-induced vibration of two parallel cylinders (s/D=2.5 and s/D=5.0), which are irregular, synchronous, anti-synchronous and skewed. In phase, in phase FF, long period in phase FF, heterogeneous FF and mixing mode.4, the coupling mechanism between two cylinders in series with the spacing ratio s/D=1.5 is obviously different from that when the spacing ratio s/D=3.0 and s/D=5.0. When the spacing ratio s/D is greater than 3.0, the response of the upstream cylinder begins to be similar to that of the single cylinder, but in the branching and non-synchronous regions at its lower end There is no hysteresis in the transition interval between the two cylinders, which indicates that the downstream cylinder has more significant influence on the upstream cylinder than the traditional view. The maximum amplitudes of the upstream two cylinders are the same, both of which are Ymax/D=0.56, which is close to the vortex-induced vibration amplitudes of a single cylinder. The maximum amplitudes of the downstream two cylinders are different, respectively, Ymax/D=1.01 and Ymax/D=0.997, which are 77.2% and 74.8% higher than the vortex-induced vibration amplitudes of a single cylinder. There are three asymmetric intervals, namely, the first asymmetric interval (Ur = 4.7-6.07), the second asymmetric interval (Ur = 6.9-7.2) and the third asymmetric interval (Ur = 10.5-50.0). After entering the asymmetric interval, the wake appears to be similar to the wide and narrow wake phenomena in the flow-induced vibration of two parallel cylinders. In short, the basic law of vortex-induced vibration of a single cylinder is studied, and the flow-induced vibration of two parallel and series cylinders is further simulated. The numerical simulation of flow-induced vibration of square-arranged four-cylinder is carried out preliminarily, and the basic flow-induced response, vibration characteristics and wake model are analyzed. The interaction mechanism of flow-induced vibration of cylinder is revealed.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV131.2

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