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首页> 外文期刊>International Journal of Heat and Mass Transfer >Effect of thermal buoyancy on vortex shedding behind a square cylinder in cross flow at low Reynolds numbers
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Effect of thermal buoyancy on vortex shedding behind a square cylinder in cross flow at low Reynolds numbers

机译：在低雷诺数下，热浮力对横流中方形圆柱体后部涡旋脱落的影响

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摘要

Two-dimensional numerical simulation is performed to understand the influence of cross buoyancy on the vortex shedding process behind a stationary heated square cylinder at low Reynolds numbers. The flow is considered in an unbounded medium, however, fictitious confining boundaries are chosen to make the problem computationally feasible. Numerical calculations are carried out by using a finite volume method based on the PISO algorithm in a collocated grid system. The range of Reynolds number is chosen to be 5-40. In this range the flow and thermal fields are found to be steady and separated without the superimposed thermal buoyancy (i.e. for pure forced convection). However, as the buoyancy parameter (Richardson number) increases flow becomes unstable and subsequently, at some critical value of Richardson number, periodic vortex shedding is observed to characterize the flow and thermal fields. The global flow and heat transfer quantities such as the recirculation length, overall drag coefficient and surface average Nusselt number are computed for the steady separated flow (without buoyancy effect) and are found in good agreement with the available results in the literature. The effect of superimposed thermal buoyancy for the range of Reynolds number is studied for various Richardson numbers. The frequency of vortex shedding (Strouhal number) is calculated for the unsteady periodic flow. The critical Richardson number for the onset of vortex shedding decreases and the corresponding critical Strouhal number increases with increasing Reynolds number in the chosen range.
机译：进行了二维数值模拟，以了解交叉浮力对低雷诺数的固定加热方筒后面的涡旋脱落过程的影响。在无限制的介质中考虑了流动，但是，选择了虚拟限制边界以使问题在计算上可行。在并置网格系统中，使用有限体积方法基于PISO算法进行数值计算。雷诺数的范围选择为5-40。在该范围内，发现流场和热场是稳定的并且分开而没有叠加的热浮力（即，对于纯强制对流）。但是，随着浮力参数（理查森数）增加，流量变得不稳定，随后，在理查森数的某个临界值处，观察到周期性涡旋脱落来表征流场和热场。为稳定的分离流（无浮力效应）计算了总的流量和传热量，例如再循环长度，总阻力系数和表面平均Nusselt数，发现它们与文献中的可用结果非常吻合。对于各种理查森数，研究了叠加热浮力对雷诺数范围的影响。对于不稳定的周期性流动，计算出涡旋脱落的频率（斯特劳哈尔数）。在选定范围内，随着雷诺数的增加，发生涡旋脱落的临界理查森数减小，而相应的临界斯特劳哈尔数增加。

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