Low-Re flow past an isolated cylinder with rounded corners
Low-Re flow past an isolated cylinder with rounded corners
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DOI：
10.1016/j.compfluid.2016.06.025
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发表时间：
2016-09
影响因子：
2.8
通讯作者：
Wei Zhang;R. Samtaney
中科院分区：
文献类型：
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作者：
Wei Zhang;R. Samtaney
对雷诺数= 1000时通过孤立圆柱的流动进行了直接数值模拟。圆柱体的四角以不同的半径为圆角，无量纲曲率半径从R+= R/D= 0.000（棱角分明的方圆柱体）到0.500（圆柱）不等，其中R为圆角半径，D为圆柱体直径。我们的目标是从时间平均统计、时间依赖行为、湍流统计和三维流动模式的角度来研究圆角对分离和过渡流通过圆柱体的发展的影响。数值结果表明，圆角处理能显著降低时间平均阻力和力波动。方形圆柱体下游尾流恢复最慢，尾流宽度最大。然而，统计量并不是随着角半径的单调变化而变化，而是在方形圆柱体和部分圆形圆柱体之间，以及后者与圆形圆柱体之间表现出剧烈的变化。与R+= 0.125圆柱体分离的自由剪切层最稳定，尾迹涡的第一次卷起发生在离圆柱体最远的地方，产生的再循环泡最大，随着R+的进一步增大，再循环泡的大小也减小。相干和非相干雷诺应力在靠近再附着点的近尾迹中最为明显，而在方形和R+= 0.125圆柱体的剪切层中也很明显。尾迹涡在流方向上的对流速度几乎是恒定的，大约是来流速度的80%。这些漩涡在圆形圆柱体中表现出几乎相同的轨迹，而在方形圆柱体中离尾流中心线最远。通过方形圆柱体的流动具有强烈的三维性，主要表现为主要的初级和次级熵，而通过圆形圆柱体的流动则以初级熵（ω z 2）为主。
Direct numerical simulation is performed for flow past an isolated cylinder at R e= 1, 000. The corners of the cylinder are rounded at different radii, with the non-dimensional radius of curvature varying from R+= R/D= 0.000 (square cylinder with sharp corners) to 0.500 (circular cylinder), in which R is the corner radius and D is the cylinder diameter. Our objective is to investigate the effect of the rounded corners on the development of the separated and transitional flow past the cylinder in terms of time-averaged statistics, time-dependent behavior, turbulent statistics and three-dimensional flow patterns. Numerical results reveal that the rounding of the corners significantly reduces the time-averaged drag and the force fluctuations. The wake flow downstream of the square cylinder recovers the slowest and has the largest wake width. However, the statistical quantities do not monotonically vary with the corner radius, but exhibit drastic variations between the cases of square cylinder and partially rounded cylinders, and between the latter and the circular cylinder. The free shear layer separated from the R+= 0.125 cylinder is the most stable in which the first roll up of the wake vortex occurs furthest from the cylinder and results in the largest recirculation bubble, whose size reduces as R+ further increases. The coherent and incoherent Reynolds stresses are most pronounced in the near-wake close to the reattachment point, while also being noticeable in the shear layer for the square and R+= 0.125 cylinders. The wake vortices translate in the streamwise direction with a convection velocity that is almost constant at approximately 80% of the incoming flow velocity. These vortices exhibit nearly the same trajectory for the rounded cylinders and are furthest away from the wake centerline for the square one. The flow past the square cylinder is strongly three-dimensional as indicated by the significant primary and secondary enstrophy, while it is dominated by the primary enstrophy (ω z 2) for the rounded cylinders.