The understanding and quantitative prediction of velocity and pressure fluctuations in turbulent flows around such bluff bodies have been evolving over the years. The main aim of the present work is to investigate experimentally and numerically the flow field in the wake region of different bluff bodies such as circular, square and triangle cross section cylinders placed horizontally perpendicular to the uniform flow. The experimental studies were performed by Particle Image Velocimetry (PIV) method in an open water channel at Reynolds numbers 5000 and 10000 defined according to the characteristic lengths of the cylinders in the facilities of Selcuk University of Advanced Technology Research and Application Center in Turkey. The experimental results are compared to the numerical results obtained by means of transient simulation with LES turbulence model of ANSYS-Fluent Software. It is shown that the numerical and experimental results have a good agreement in respect of the instantaneous and time-averaged flow field patterns of vorticity, velocity component streamwise direction and streamline topology. In addition, drag coefficient of the geometries were also numerically calculated. For all geometries the wake length in x and y directions and size of the foci of the streamlines are decreasing by increasing Reynolds numbers in time-averaged results. The time-averaged flow patterns of both experimental and numerical results have considerable symmetry with respect to the centerline of each cylinder. Contours of the time-averaged stream wise velocity for Re=10000 demonstrate that the stagnation point around the symmetry plane moves further upstream for all cylinders in accordance with Re=5000. The maximum drag coefficient value was yielded for the square cross-section cylinder as 1.78 due to the sharp-edged geometry.
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机译：这些年来，对湍流周围湍流速度和压力波动的理解和定量预测一直在发展。本工作的主要目的是通过实验和数值研究不同钝体的尾流区域内的流场，例如水平，垂直于均匀流放置的圆形，方形和三角形横截面圆柱体。在土耳其塞尔柱克大学高级技术研究和应用中心的设施中，根据气瓶的特征长度，在雷诺数为5000和10000的明水通道中，通过粒子图像测速（PIV）方法进行了实验研究。将实验结果与通过ANSYS-Fluent软件的LES湍流模型进行瞬态仿真得到的数值结果进行比较。结果表明，数值模拟和实验结果在涡流，速度分量流向和流线形拓扑的瞬时和时间平均流场模式方面具有良好的一致性。另外，还通过数值计算了几何形状的阻力系数。对于所有几何形状，通过在时间平均结果中增加雷诺数，可以减小在x和y方向上的尾流长度和流线焦点的大小。实验结果和数值结果的时间平均流动模式相对于每个气缸的中心线具有相当大的对称性。 Re = 10000的时间平均流向速度的等高线表明，根据Re = 5000，对称平面周围的停滞点向所有汽缸进一步向上游移动。由于具有锋利的几何形状，方形截面圆柱的最大阻力系数值为1.78。
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