Abstract Non-intrusive field measurements in the wake region of a circular adiabatic cylinder fitted in a channel are reported. The top wall of the channel is subjected to constant heat flux while maintaining the bottom wall and the cylinder under adiabatic condition. The cylinder diameter has been varied to achieve three different blockage ratios (D/H) of 0.25, 0.38 and 0.5. Experiments are performed in the range of 63≤Re ≤ 165 with water as the coolant fluid under hydrodynamically fully developed and thermally developing conditions. Effect of blockage ratio on heat transfer enhancement capability, its capacity to alter the flow physics by modifying the size of vortices, the downstream distance they travel and the Reynolds number at which the vortices get initiated, is reported. Path-integrated temperature distribution in the channel has been mapped through the classical form of Mach Zehnder interferometer. The temperature distribution thus obtained has been used to determine the variations in local heat transfer coefficient along the length of the top horizontal surface of the channel. Schlieren deflectometry is used to quantify the vortex shedding frequency under three different blockage ratio regimes. The experimentally obtained results are benchmarked and validated by performing numerical simulations using FLUENT. It has been observed that a decrease in blockage ratio at a constant Re leads to alterations in the size of the generated vortices, which manifest as an increase in the vortex shedding frequency. Vortex shedding is seen to get initiated at relatively lower value of Re (= 65) when the blockage ratio is low (D/H = 0.25). However, when the wake transition to three-dimensionalities is considered, an increase in blockage ratio from D/H = 0.25 to 0.5 leads to an increase in the value of transition Re (165 for D/H = 0.5). It is observed that the vortices travel maximum downstream distance for blockage ratio of 0.38. For all blockage ratios, due to vortex shedding, the thermal boundary layer assumes a corrugated shape and aids in enhancing the heat transfer rates from the channel surface.

中文翻译：

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使用全场动态测量研究堵塞比对嵌入通道的圆柱尾流区域的流动和传热的影响

摘要 报道了安装在通道中的圆形绝热圆柱体尾流区域的非侵入式场测量。通道的顶壁承受恒定的热通量，同时将底壁和圆柱体保持在绝热条件下。气缸直径已经改变，以实现三种不同的堵塞比 (D/H)，分别为 0.25、0.38 和 0.5。实验是在 63≤Re≤165 的范围内进行的，水作为冷却液，在流体力学充分发展和热发展的条件下进行。报告了堵塞比对传热增强能力的影响，它通过修改涡流的大小、它们行进的下游距离和开始涡流的雷诺数来改变流动物理的能力。通道中的路径集成温度分布已通过经典形式的马赫曾德尔干涉仪绘制。由此获得的温度分布已用于确定沿通道顶部水平表面长度的局部传热系数的变化。纹影偏转法用于量化三种不同阻塞率制度下的涡旋脱落频率。通过使用 FLUENT 进行数值模拟，对实验获得的结果进行了基准测试和验证。已经观察到，在恒定 Re 下阻塞率的降低导致产生的涡流大小的改变，这表现为涡流脱落频率的增加。当阻塞率低 (D/H = 0.25) 时，可以看到涡旋脱落在相对较低的 Re 值 (= 65) 处开始。然而，当考虑到三维的尾流过渡时，阻塞比从 D/H = 0.25 增加到 0.5 会导致过渡 Re 的值增加（D/H = 0.5 时为 165）。据观察，当堵塞比为 0.38 时，涡流在下游行进最大距离。对于所有阻塞率，由于涡流脱落，热边界层呈波纹状，有助于提高通道表面的传热率。据观察，当堵塞比为 0.38 时，涡流在下游行进最大距离。对于所有阻塞率，由于涡流脱落，热边界层呈波纹状，有助于提高通道表面的传热率。据观察，当堵塞比为 0.38 时，涡流在下游行进最大距离。对于所有阻塞率，由于涡流脱落，热边界层呈波纹状，有助于提高通道表面的传热率。