This study examines thermal flow structures and heat transfer through a vertical heated channel with an adiabatic circular cylinder symmetrically positioned between lateral walls. A two-dimensional numerical simulation is conducted covering a range of parameters including Rayleigh numbers Ra = 8.9 × 106–8.9 × 108, cylinder positions relative to the channel height h = 0–0.50, and blockage ratios (the ratio of cylinder diameter to channel width) β = 0.25–0.75. Three distinct flow regimes are observed at different Rayleigh numbers and blockage ratios, including steady symmetric, unsteady periodic, and unsteady asymmetric flow regimes. The steady symmetric and unsteady periodic flows are observed at all blockage ratios, while the unsteady asymmetric flow is only observed at the highest blockage ratio of β = 0.75 for Rayleigh numbers above 8.9 × 107. It is found that the presence of the cylinder significantly enhances mixing and turbulence in the channel, which in turn enhances heat transfer through the channel. A 64.3% enhancement of heat transfer is achieved at β = 0.50 and h = 0.05 for Ra = 8.9 × 108.

中文翻译：

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有限圆柱垂直加热通道自然对流的数值研究

本研究研究了通过垂直加热通道的热流结构和传热，该通道具有对称位于侧壁之间的绝热圆柱体。进行二维数值模拟，涵盖一系列参数，包括瑞利数 Ra = 8.9 × 106–8.9 × 108、圆柱体相对于通道高度 h = 0–0.50 的位置以及堵塞率（圆柱体直径与通道的比率）宽度）β = 0.25–0.75。在不同的瑞利数和阻塞比下观察到三种不同的流态，包括稳态对称流态、非稳态周期性流态和非稳态非对称流态。在所有阻塞比下都观察到稳态对称和非稳态周期性流动，而非稳态非对称流动仅在瑞利数高于 8.9 × 107 的最高阻塞比 β = 0.75 时观察到。发现圆柱体的存在显着增强了通道中的混合和湍流，这反过来又增强了通过通道的传热。当 Ra = 8.9 × 108 时，当 β = 0.50 和 h = 0.05 时，传热增强了 64.3%。