The aim of this study was to investigate the effects of installing the grooved and smooth control cylinder upstream of a circular bare cylinder with a focus on the heat transfer and the flow structure behind the bare cylinder. The Reynolds number based on the bare cylinder diameter (D = 50 mm) is Re = 5 000. Control cylinder has a constant diameter as d = 25 mm. Flow characteristics and heat transfer were determined the varying gap space L (center-to-center distance between the bare cylinder and the control cylinder) and surface geometries. The experimental study was conducted in a water channel to collect the temperature and velocity data. Heat transfer coefficient and Nusselt number were determined by measuring the surface temperature distributions. A digital particle image velocimetry (PIV) system was also used to quantify the flow characteristics in order to assess the effectiveness of the flow control with different grooved surface (smooth, rectangular, triangular and circular grooved), in comparison with a bare cylinder case. As to the temperature measurement results, the optimum gap space was defined as L/D = 2.0. It was found that when the control cylinder is introduced, the separation point shifted downstream of the bare cylinder. The cylinders with groove geometry, however, proved to improve heat transfer in comparison to a single main cylinder. The velocity profiles in the time-averaged streamwise direction caught the peak of the single cylinder at L/D = 2.0, where the time-averaged velocity profiles of the control cylinders were minimum. The vorticity components showed that grooved cylinders were more effective in flow control, especially at L/D = 2.0, compared to a single cylinder.

本研究的目的是研究在圆形裸圆柱体上游安装凹槽平滑控制圆柱体的影响，重点是裸圆柱体后面的传热和流动结构。基于裸圆柱体直径 (D = 50 毫米) 的雷诺数为 Re = 5 000。控制圆柱体的直径恒定为 d = 25 毫米。流动特性和传热由变化的间隙空间 L（裸圆柱体和控制圆柱体之间的中心到中心距离）和表面几何形状确定。实验研究是在水道中进行的，以收集温度和速度数据。通过测量表面温度分布来确定传热系数和努塞尔数。还使用数字粒子图像测速 (PIV) 系统来量化流动特性，以评估不同凹槽表面（光滑、矩形、三角形和圆形凹槽）与裸圆柱体情况下的流动控制的有效性。对于温度测量结果，最佳间隙空间定义为 L/D = 2.0。发现当引入控制圆柱体时，分离点移动到裸圆柱体的下游。然而，与单个主汽缸相比，具有凹槽几何形状的汽缸被证明可以改善传热。时间平均流向的速度分布在 L/D = 2.0 处捕捉到单缸的峰值，其中控制缸的时间平均速度分布最小。