Flow along a long thin cylinder
Flow along a long thin cylinder
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DOI：
10.1017/s0022112008000542
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发表时间：
2008-04
影响因子：
3.7
通讯作者：
O. Tutty
中科院分区：
文献类型：
--
作者：
O. Tutty
用两种不同的方法计算了细长圆柱体的湍流流动，其中流动与圆柱体对齐。边界层程序被用来预测超长圆柱体(长径比高达O(106))的平均流动，并通过湍流模型估计湍流的影响。与实验结果的详细比较表明，预测的平均流动性质在实验精度范围内。边界层模型预测，在下游足够远的地方，表面剪应力将(几乎)保持不变。这与声纳阵列形式的长圆柱体的实验结果一致。建立了一个周期的Navier-Stokes问题，得到了雷诺数从300到5×104的解。计算结果与边界层模型和实验结果相吻合。强湍流只发生在圆柱体表面附近，大部分边界层上的湍流相对较弱。对于边界层厚度远大于圆柱体半径的厚边界层，表面附近的平均流动在时间和空间上都是有效的恒定的，而外部流动在时间或空间上继续发展。对周向平均表面压力谱的计算表明，在物理意义上，随着圆柱体半径的减小，来自湍流的表面噪声增加，在雷诺数为O(103)时噪声最大。噪声随半径(雷诺数)的减小而增大，这与实验结果一致。
Two different approaches have been used to calculate turbulent flow along a long thin cylinder where the flow is aligned with the cylinder. A boundary-layer code is used to predict the mean flow for very long cylinders (length to radius ratio of up to O(106)), with the effects of the turbulence estimated through a turbulence model. Detailed comparison with experimental results shows that the mean properties of the flow are predicted within experimental accuracy. The boundary-layer model predicts that, sufficiently far downstream, the surface shear stress will be (almost) constant. This is consistent with experimental results from long cylinders in the form of sonar arrays. A periodic Navier–Stokes problem is formulated, and solutions generated for Reynolds number from 300 to 5×104. The results are in agreement with those from the boundary-layer model and experiments. Strongly turbulent flow occurs only near the surface of the cylinder, with relatively weak turbulence over most of the boundary layer. For a thick boundary layer with the boundary-layer thickness much larger than the cylinder radius, the mean flow is effectively constant near the surface, in both temporal and spatial frameworks, while the outer flow continues to develop in time or space. Calculations of the circumferentially averaged surface pressure spectrum show that, in physical terms, as the radius of the cylinder decreases, the surface noise from the turbulence increases, with the maximum noise at a Reynolds number of O(103). An increase in noise with a decrease in radius (Reynolds number) is consistent with experimental results.