刚性圆柱绕流以及稳定性的研究

发布时间：2017-12-28 10:47

本文关键词：刚性圆柱绕流以及稳定性的研究　出处：《江苏大学》2015年硕士论文　论文类型：学位论文

【摘要】：长久以来圆柱绕流问题一直是流体力学中最经典的问题。当流体绕过圆柱时,由于过流断面收缩,其流速增加,压强减少,由于粘性力的作用,就会在圆柱附近发生边界层分离现象,形成卡门涡街。而在计算流体力学(CFD)中,圆柱绕流的数值模拟也一直是验证流体计算软件可靠性的经典案例。在这篇研究论文中,首先主要基于OpenFOAM开源计算软件,通过对网格参数化的控制,快速的生成了较好的网格,探讨了层流条件下不同雷诺数圆柱绕流的阻力系数Cd、升力系数Cl、斯特罗哈数St,并于前人的实验和计算结果进行对比。之后,模拟了亚临界区圆柱绕流,使用SST k-ω湍流模型将Cd、Cl与相关数据进行了验证。建立了阻力系数平均值Cd,rms、升力系数最大值的平均值Clmax,rms随着Re变化的关系。其次我们利用大涡模拟的方法研究了槽道流与临界区的圆柱绕流,根据拟序结构对正弦扰动的不稳定性快速生成了湍流,并对于壁面附近的流向速度与壁面距离的关系进行了探讨;得到了对于低湍动能下光滑圆柱绕流的临界雷诺数。最后采用6DOF动网格模型,对于亚临界区单自由度圆柱绕流进行数值模拟。并采用C++编程语言,利用Romberg数值积分、数值拟合等多种方法对数据进行了提取、处理、分析,发现静止圆柱绕流Cl在一定周期内符合正弦变化,具有周期性。因此在一定周期内,单自由度圆柱相对稳定,但是由于初始流场的状态、圆柱的质量不同,会很快影响圆柱的稳定性特别是其偏离的幅度,而流固的耦合作用也会影响升力变化的频率,最终使得圆柱发生偏离;在一定周期以后由于对于静止圆柱Cl并不呈周期变化,圆柱最终一定会发生偏移。根据圆球与圆柱绕流的相似性,进行了类比,对比了球类运动中的参数,最终研究卡门涡街对球类运动的影响。
[Abstract]:The problem of flow around a cylinder has long been the most classical problem in fluid mechanics. When the fluid passes through the cylinder, the flow velocity increases and the pressure decreases due to the contraction of the cross section. Due to the effect of viscous force, the boundary layer separation near the column will happen, and the Carmen vortex street will form. In computational fluid dynamics (CFD), the numerical simulation of the flow around a cylinder has always been a classic case to verify the reliability of the fluid computing software. In this paper, firstly, mainly based on the OpenFOAM open source software, through the control of mesh parameterization, quickly generate better grid, discusses the flow laminar flow under different Reynolds number cylinder drag coefficient Cd, lift coefficient Cl, Castro ha St, and the results of experiment and calculation on the previous comparison. After that, the flow around the sub critical region is simulated, and the SST k- Omega turbulence model is used to verify the Cd, Cl and related data. The mean value of the drag coefficient Cd, RMS, the mean value of the maximum lift coefficient Clmax, and the relationship between the RMS and the Re change are established. Secondly, we use the method of flow around a large eddy simulation of channel flow and the critical region according to the coherent structure of cylindrical, sinusoidal disturbance instability quickly generate turbulence, and the relationship between flow velocity and wall distance near the wall surface are discussed; obtained for Reynolds flow under low turbulence kinetic energy cylinder number. Finally, the 6DOF dynamic mesh model is used to simulate the flow around a single degree of freedom cylinder in the subcritical region. By using C++ programming language, Romberg data integration, numerical fitting and other methods were used to extract, process and analyze the data. It was found that the Cl of stationary cylinder flows in a certain period, which is sinusoidal and cyclical. Therefore, in a certain period, a single degree of freedom cylindrical is relatively stable, but because of the quality of the state, cylindrical initial flow field is different, will soon affect the stability of cylindrical especially the deviation of the amplitude, and the flow structure interaction will also affect the change of the lift frequency, eventually making cylindrical deviation; in a certain period after the for the stationary cylinder Cl does not change periodically, the cylinder will eventually shift. According to the similarity between the circle and the circular cylinder, the analogy is carried out, the parameters in the ball movement are compared, and the influence of Carmen vortex street on the ball movement is finally studied.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O357.5

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