THE VISCOUS-FLOW ON SURFACES WITH LONGITUDINAL RIBS
THE VISCOUS-FLOW ON SURFACES WITH LONGITUDINAL RIBS
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DOI：
10.1017/s0022112089002247
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发表时间：
1989-09-01
影响因子：
3.7
通讯作者：
BARTENWERFER, M
中科院分区：
文献类型：
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作者：
BECHERT, DW;BARTENWERFER, M
对具有细长纵肋(肋)表面的湍流边界层的粘性亚层进行了理论研究。考虑了这种粘性流动的平均流动成分。利用保角变换，计算了不同表面构型上的速度分布。所研究的几何形状包括具有三角形和梯形凹槽的锯齿形轮廓，以及具有薄的刀片形状的肋条、圆边的肋条和具有尖脊和U形凹槽的肋条。(后一种Riblet构型也可以在微小的快鲨身上找到。)我们的计算使我们能够确定位于山脊尖端以下的速度剖面的原点的位置。这个原点与脊尖之间的距离，我们称之为“凸出高度”。发现凸起高度的上限是侧筋间距的22%；系数0.22是表达式π−1在2中的值。该限制适用于二维肋片几何形状。用电解槽进行了类似的实验，作为对理论计算的补充检验。这也是一种通过实验确定任意新Riblet几何形状的速度剖面原点位置的简单方法。讨论了湍流边界层流中凸起高度与减阻之间的可能联系。最后，本理论还在脊形表面上方产生了一种可用于未来整个湍流边界层的数值计算的正交格网模式。
The viscous sublayer of a turbulent boundary layer on a surface with fine longitudinal ribs (riblets) is investigated theoretically. The mean flow constituent of this viscous flow is considered. Using conformal mapping, the velocity distributions on various surface configurations are calculated. The geometries that were investigated include sawtooth profiles with triangular and trapezoidal grooves as well as profiles with thin blade-shaped ribs, ribs with rounded edges and ribs having sharp ridges and U-shaped grooves. (This latter riblet configuration is also found on the tiny scales of fast sharks.) Our calculations enable us to determine the location of the origin of the velocity profile that lies somewhat below the tips of the ridges. The distance between this origin and the tip of the ridge we call ‘protrusion height’. The upper limit for the protrusion height is found to be 22% of the lateral rib spacing; the coefficient 0.22 being the value of the expression π−1 In 2. This limit is valid for two-dimensional riblet geometries. Analogous experiments with an electrolytic tank are carried out as an additional check on the theoretical calculations. This is also an easy way to determine experimentally the location of the origin of the velocity profile for arbitrary new riblet geometries. A possible connection between protrusion height and drag reduction in a turbulent boundary layer flow is discussed. Finally, the present theory also produces an orthogonal grid pattern above riblet surfaces which may be utilized in future numerical calculations of the whole turbulent boundary layer.