Abstract In this study, we perform a numerical investigation to better comprehend the domination and the effect of strong thermal buoyancy on hydrodynamic and thermal characteristics, vortex shedding in particular, of a horizontal circular heated cylinder subject to a vertically upward laminar flow stream. The Reynolds number is varied in the range 20 ≤ R e ≤ 150 while maintaining the Prandtl number constant at P r = 7.1. The effect of thermal buoyancy on the system is determined by varying the Richardson number up to R i = 5. The behaviour is determined by solving the unsteady laminar two-dimensional Navier–Stokes and standard energy equations numerically, utilising the spectral-element method with buoyancy considered using the Boussinesq approximation. Representative vorticity, streamline, and thermal patterns are presented, and the average Nusselt numbers are plotted as a function of the Richardson number for a set of Reynolds numbers to explain, in detail, the role of superimposed thermal buoyancy on the wake flow and rates of heat transfer. The predictions demonstrate that the wake flow exhibits unsteady periodic characteristics for the selected moderate Reynolds numbers, and as the buoyancy parameter increases, the fluid flow and temperature fields become less stable. Subsequently, it was observed that heat transfer augmented considerably, the vortex shedding stopped abruptly, the wake converted to steady twin vortices beyond certain critical Richardson numbers, and the Nusselt numbers suddenly reduced to minimum values. These critical values are determined to increase with the Reynolds number. The results also confirm that for increased heating, the recirculating flow in the cylinder near the wake disappears and flow separation occurs only at the backward stagnation point.

中文翻译：

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热浮力对平行流圆柱体后涡脱落的影响

摘要 在这项研究中，我们进行了数值研究，以更好地理解强热浮力对受垂直向上层流影响的水平圆形加热圆柱体的流体动力和热特性的支配和影响，尤其是涡旋脱落。雷诺数在 20 ≤ Re ≤ 150 的范围内变化，同时保持普朗特数恒定在 P r = 7.1。热浮力对系统的影响是通过改变理查森数直到 R i = 5 来确定的。 行为是通过数值求解非定常层流二维纳维-斯托克斯方程和标准能量方程来确定的，利用谱元方法使用 Boussinesq 近似考虑的浮力。呈现了具有代表性的涡度、流线和热模式，将平均努塞尔数绘制为一组雷诺数的理查森数的函数，以详细解释叠加热浮力对尾流和传热速率的作用。预测表明，对于选定的中等雷诺数，尾流表现出不稳定的周期性特征，并且随着浮力参数的增加，流体流动和温度场变得不太稳定。随后，观察到传热显着增加，涡旋脱落突然停止，尾流转变为超过某些临界理查森数的稳定孪生涡旋，并且努塞尔特数突然减小到最小值。这些临界值被确定为随着雷诺数的增加而增加。结果还证实，对于增加的加热，