Tailoring turbulence with an active grid
Tailoring turbulence with an active grid
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使用主动网格定制湍流
DOI：
10.1007/s00348-009-0812-5
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发表时间：
2010
影响因子：
2.4
通讯作者：
W. Water
中科院分区：
文献类型：
--
作者：
H. E. Cekli;W. Water
在风洞中使用主动网格，我们产生均匀的剪切湍流，并启动可调属性的湍流边界层。均匀剪切湍流的特征在于平均速度的恒定梯度和恒定的湍流强度。它是最简单的各向异性湍流湍流，传统上是通过在风洞中安装具有不同透明度的屏幕和流动矫直器来产生的。这并不容易做到，而且可达到的湍流水平是适度的。我们描述了一种新的技术，用于生成均匀剪切湍流只使用一个活动的网格。我们的活动网格由一个网格杆与附加叶片，可以旋转的伺服电机。我们通过规定每个轴的时间相关角度来控制网格。我们通过设置每个杆的适当角度来调整网格的垂直透明度剖面，例如以产生均匀的速度梯度，并设置杆在这些角度周围的拍打运动以定制湍流强度。达到的泰勒雷诺数为Rλ = 870，剪切速率S = 10 U/10 y = 9.2 s−1，无量纲剪切参数S* 10 Sq 2/ε = 12，u = 1.4 ms−1。作为这一思想的进一步应用，我们演示了在风洞中模拟大气边界层的生成，它具有可调的属性。这种方法比传统的方法有很大的优势，传统的方法需要在风洞中放置涡产生结构来产生厚边界层。
Using an active grid in a wind tunnel, we generate homogeneous shear turbulence and initiate turbulent boundary layers with adjustable properties. Homogeneous shear turbulence is characterized by a constant gradient of the mean velocity and a constant turbulence intensity. It is the simplest anisotropic turbulent flow thinkable, and it is generated traditionally by equipping a wind tunnel with screens which have a varying transparency and flow straighteners. This is not done easily, and the reachable turbulence levels are modest. We describe a new technique for generating homogeneous shear turbulence using an active grid only. Our active grid consists of a grid of rods with attached vanes which can be rotated by servo motors. We control the grid by prescribing the time-dependent angle of each axis. We tune the vertical transparency profile of the grid by setting appropriate angles of each rod such as to generate a uniform velocity gradient, and set the rods in flapping motion around these angles to tailor the turbulence intensity. The Taylor Reynolds number reached was Rλ = 870, the shear rate S = ∂U/∂y = 9.2 s−1, the nondimensional shear parameter S*≡ Sq2/ε = 12 and u = 1.4 ms−1. As a further application of this idea we demonstrate the generation of a simulated atmospheric boundary layer in a wind tunnel which has tunable properties. This method offers a great advantage over the traditional one, in which vortex-generating structures need to be placed in the wind tunnel to initiate a fat boundary layer.
影响因子：
3.7
作者：
I. Castro
通讯作者：
I. Castro