Effects of wavelength and amplitude of a wavy cylinder in cross-flow at low Reynolds numbers
Effects of wavelength and amplitude of a wavy cylinder in cross-flow at low Reynolds numbers
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DOI：
10.1017/s0022112008004217
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发表时间：
2009-02-10
影响因子：
3.7
通讯作者：
Lin, Y. F.
中科院分区：
文献类型：
--
作者：
Lam, K.;Lin, Y. F.
对横截面沿翼展方向呈正弦变化的圆柱体（称为“波状圆柱体”）周围的层流进行了三维数值模拟。在 Re = U(x) D(m)/v = 100 的雷诺数下详细研究了一系列具有不同无量纲波长和波幅 (a/D(m)) 组合的波状圆柱体，其中 U(x) 是自由流速度，D(m) 是波状圆柱体的平均直径。平均阻力系数和均方根（rms）升力系数随无量纲波长变化的结果表明，对于所研究的不同振幅，平均力系数和脉动力系数在最佳无量纲波长 lambda/D(m) 分别约为 2.5 和 6 时显着减小。根据流动结构和力特性的变化，将无量纲波长从lambda/D(m) = 1到lambda/D(m) = 10分为对应于三种类型尾流结构的三个波长范围。捕获了不同波状圆柱体近尾流处的尾流结构。对于所有波状圆柱体，分流线沿翼展方向变化。这导致沿翼展方向发展出周期性重复的三维自由剪切层，波状圆柱体的三维自由剪切层比圆柱体更大、更稳定，在某些情况下自由剪切层甚至不会卷入圆柱体后面成熟的涡街。因此，一些典型的波形圆柱体的平均阻力系数小于相应的圆柱体，阻力系数最大降低达18%。均方根值在最佳波长下，升力系数大大降低至几乎为零。在层流状态（60
Three-dimensional numerical simulations of laminar flow around a circular cylinder with sinusoidal variation of cross-section along the spanwise direction, named 'wavy cylinder', are performed. A series of wavy cylinders with different combinations of dimensionless wavelength and wave amplitude (a/D(m)) are studied in detail at a Reynolds number of Re = U(x) D(m)/v = 100, where U(x) is the free-stream velocity and D(m) is the mean diameter of a wavy cylinder. The results of variation of mean drag coefficient and root mean square (r.m.s.) lift coefficient with dimensionless wavelength show that significant reduction of mean and fluctuating force coefficients Occurs at optimal dimensionless wavelengths lambda/D(m) of around 2.5 and 6 respectively for the different amplitudes studied. Based on the variation of flow structures and force characteristics, the dimensionless wavelength from lambda/D(m) = 1 to lambda/D(m) = 10 is classified into three wavelength regimes corresponding to three types of wake structures. The wake structures at the near wake of different wavy cylinders are captured. For all wavy cylinders, the flow separation line varies along the spanwise direction. This leads to the development of a three-dimensional free shear layer with periodic repetition along the spanwise direction, The three-dimensional free shear layer of the wavy cylinder is larger and more stable than that of the circular cylinder, and in some cases the free shear layer even does not roll Lip into a mature vortex street behind the cylinder. As a result, the mean drag coefficients of some of the typical wavy cylinders are less than that of a corresponding circular cylinder with a maximum drag coefficient reduction up to 18%. The r.m.s. lift coefficients are greatly reduced to practically zero at optimal wavelengths. In the laminar flow regime (60