Abstract Many circular cylindrical engineering structures submerged in fluid are not always orthogonal to flow direction. Oblique circular cylinder is a more general model to study the flow around circular cylindrical engineering structures. Comparing with a normal circular cylinder, there are more three-dimensional effects reflected in the wake flow and aerodynamic forces of an oblique circular cylinder. Moreover, axial flow is a unique and important flow phenomenon in the oblique circular cylinder wake flow. This study introduces a numerical study based on an oblique circular cylinder model and unsteady Reynolds-Averaged Navier-Stokes equations (URANS) to reveal the three-dimensional external flow and axial flow. Effects of the yaw angles take the most attentions. The analyzed flow features include aerodynamic force coefficients, wake flow velocities, correlations between aerodynamic forces and wake flow structures, three-dimensional vortex structures and three-dimensional axial flow. Spectrum signatures of wake flow fluctuation and time-average axial flow pattern are verified by a visualized wind tunnel experiment. Numerical results prove that there are obvious three-dimensional effects in wake flow velocities and aerodynamic forces. Yaw angle, as a crucial parameter, determines the configuration of vortices. Furthermore, yaw angle affects the spectrum signatures of wake flow fluctuation and aerodynamic force fluctuation, and change the spanwise correlation of wake flow. A novel time-average axial flow velocity-distribution pattern is observed in the numerical results and experiment results. Its mechanism is analyzed based on the wake vortex structures.

中文翻译：

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斜圆柱尾流的三维特征及轴向流型

摘要 许多浸没在流体中的圆柱形工程结构并不总是与流向正交。斜圆柱体是研究圆柱体工程结构周围流动的更通用的模型。与普通圆柱体相比，斜圆柱体的尾流和气动力体现出更多的三维效果。此外，轴流是斜圆柱尾流中独特而重要的流动现象。本研究引入了基于斜圆柱模型和非定常雷诺-平均纳维-斯托克斯方程 (URANS) 的数值研究，以揭示三维外部流和轴流。偏航角的影响最受关注。分析的流动特征包括气动力系数、尾流速度、空气动力与尾流结构之间的相关性、三维涡结构和三维轴流。通过可视化风洞实验验证了尾流波动和时均轴流模式的频谱特征。数值结果证明尾流速度和气动力存在明显的三维效应。偏航角作为一个关键参数，决定了涡流的配置。此外，偏航角影响尾流波动和气动力波动的频谱特征，改变尾流的展向相关性。在数值结果和实验结果中观察到一种新的时均轴流速度分布模式。基于尾涡结构分析其机理。气动力与尾流结构、三维涡结构和三维轴流之间的相关性。通过可视化风洞实验验证了尾流波动和时均轴流模式的频谱特征。数值结果证明尾流速度和气动力存在明显的三维效应。偏航角作为一个关键参数，决定了涡流的配置。此外，偏航角影响尾流波动和气动力波动的频谱特征，改变尾流的展向相关性。在数值结果和实验结果中观察到一种新的时均轴流速度分布模式。基于尾涡结构分析其机理。气动力与尾流结构、三维涡结构和三维轴流之间的相关性。通过可视化风洞实验验证了尾流波动和时均轴流模式的频谱特征。数值结果证明尾流速度和气动力存在明显的三维效应。偏航角作为一个关键参数，决定了涡流的配置。此外，偏航角影响尾流波动和气动力波动的频谱特征，改变尾流的展向相关性。在数值结果和实验结果中观察到一种新的时均轴流速度分布模式。基于尾涡结构分析其机理。