An experimental study of a three-dimensional pressure-driven turbulent boundary layer
An experimental study of a three-dimensional pressure-driven turbulent boundary layer
复制标题
三维压力驱动湍流边界层的实验研究
DOI：
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发表时间：
1995
影响因子：
3.7
通讯作者：
R. Simpson
中科院分区：
文献类型：
--
作者：
Semih M. Ölçmen;R. Simpson
本文对由理想翼身结合部流动产生的三维压力驱动湍流边界层进行了实验研究。所提供的数据包括时间平均静压和直接测量的壁面摩擦力大小。三速度分量光纤激光多普勒风速计的平均速度和所有雷诺应力呈现在沿着由平均速度矢量分量确定的线的几个站平行于壁在层中的$\overline{u^2}$运动法向应力是最大的（法向应力坐标系）。这条线是通过直觉推理选择的，即近壁流动和外部区域流动的重叠发生在$\overline{u^2}$最大的位置。沿着这条线，水流受到强烈的横流压力梯度的影响，这改变了下游站的符号。流动中的剪应力矢量方向滞后于流动梯度矢量方向。这里研究的流动与许多其他实验研究的三维流动不同，因为平均流动变量取决于三个空间轴而不是两个轴，例如流动的三维性是由旋转圆柱体或整个流动中仅在一个方向上的压力梯度产生的。实验结果表明，流动的涡粘性不是各向同性的。这些和其他选定的数据集表明，在壁面剪应力坐标系中展向涡动粘度与流向涡动粘度之比比，比在局部自由流坐标系或法向应力坐标系中的分散性小，且更恒定（约0.6）。当y+ > 50且y/δ < 0.8时，|τ/ρ|对于剪切驱动和压力驱动的三维流动的三维流动站，运动法向应力$\overline{v^2}$近似为常数。在同一区域内，对于三维压力驱动流动，运动剪应力$-\overline{vw}/-\overline{uw}$的比值似乎是壁面应力坐标中y+的函数。
A three-dimensional, pressure-driven turbulent boundary layer created by an idealized wing–body junction flow was studied experimentally. The data presented include time-mean static pressure and directly measured skin-friction magnitude on the wall. The mean velocity and all Reynolds stresses from a three-velocity-component fibre-optic laser-Doppler anemometer are presented at several stations along a line determined by the mean velocity vector component parallel to the wall in the layer where the $\overline{u^2}$ kinematic normal stress is maximum (normal-stress coordinate system). This line was selected by intuitively reasoning that overlap of the near-wall flow and outer-region flow occurs at the location where $\overline{u^2}$ is maximum. Along this line the flow is subjected to a strong crossflow pressure gradient, which changes sign for the downstream stations. The shear-stress vector direction in the flow lags behind the flow gradient vector direction. The flow studied here differs from many other experimentally examined three-dimensional flows in that the mean flow variables depend on three spatial axes rather than two axes, such as flows in which the three-dimensionality of the flow has been generated either by a rotating cylinder or by a pressure gradient in one direction only throughout the flow. The data show that the eddy viscosity of the flow is not isotropic. These and other selected data sets show that the ratio of spanwise to streamwise eddy viscosities in the wall-shear-stress coordinate system is less scattered and more constant (about 0.6) than in the local free-stream coordinate system or the normal stress coordinate system. For y+ > 50 and y/δ < 0.8, the ratio of the magnitude of the kinematic shear stress |τ/ρ| to the kinematic normal stress $\overline{v^2}$ is approximately a constant for three-dimensional flow stations of both shear-driven and pressure-driven three-dimensional flows. In the same region, the ratio of the kinematic shear stresses $-\overline{vw}/-\overline{uw}$ appears to be a function of y+ in wall-stress coordinates for three-dimensional pressure-driven flows.