An alternative floating element design for skin-friction measurement of turbulent wall flows
An alternative floating element design for skin-friction measurement of turbulent wall flows
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用于湍流壁流的表面摩擦测量的替代浮动元件设计
DOI：
10.1007/s00348-018-2612-2
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发表时间：
2018
影响因子：
2.4
通讯作者：
Ferreira M
中科院分区：
文献类型：
--
作者：
Ferreira M
估算表面剪应力的间接方法通常用于模拟粗糙壁边界层流动。不确定性通常很大，通常不足以进行定量分析，特别是对于表面粗糙度，其中已建立的缩放和相似性定律可能不成立。因此，最好是依靠独立的测量技术来准确地测量表面摩擦。浮动元素是最早引入的元素之一，并且仍然是最受欢迎的功能。虽然其基本原则保持不变，但已提出不同的安排，以克服其固有的局限性。在本文中，我们回顾了这些设计中的一些，并进一步提出了一种替代方案，能够校正到阻力测量的外来负载。其结构基于平行移动连杆，并具有定制的力传感器和数据采集系统，旨在实现高信噪比。光滑壁边界层流被用作基准来评估这种平衡的准确性。表面摩擦系数的值显示出与热线风速仪的协议，在。本文还研究了具有较大相对高度的交错分布立方体的粗糙表面。结果表明，在整个雷诺数范围内，在测量位置处，流动达到完全粗糙状态。此外，表面摩擦的值同意现有的估计，从替代的方法。图形abstractDrawings的浮动元件（FE）的平衡和表面摩擦测量光滑壁边界层。顶部：沿X-Y平面和顶部视图（左）对其相应图片（右）进行沿着切片。颜色突出了不同的子系统，即用于阻力测量的浮动框架（黄色），俯仰力矩机构（红色）和采集系统（蓝色）。左下角：光滑壁设置和校准系统。FE与风洞地板齐平安装，滑轮连接到一个线性横梁上，允许将其位置设置在不同的壁法线位置。在校准过程中，盖子被移除，以便滑轮移动到测试部分。然后用一根金属丝把重物吊起来。右下角：光滑墙壁上的皮肤摩擦。插图表示FE值（蓝色）和从边界层剖面的热线风速仪推断的FE值（红色）之间的相对差异。
AbstractIndirect methods to estimate surface shear stress are commonly used to characterise rough-wall boundary-layer flows. The uncertainty is typically large and often insufficient to carry out quantitative analysis, especially for surface roughness where established scaling and similarity laws may not hold. It is, thus, preferable to rely instead on independent measurement techniques to accurately measure skin friction. The floating element was one of the first to be introduced, and still is the most popular for its features. Although its fundamental principle has remained unchanged, different arrangements have been suggested to overcome its inherent limitations. In this paper, we review some of these designs and further present an alternative that is able to correct for extraneous loads into the drag measurement. Its architecture is based on the parallel-shift linkage, and it features custom-built force transducers and a data acquisition system designed to achieve high signal-to-noise ratios. The smooth-wall boundary-layer flow is used as a benchmark to assess the accuracy of this balance. Values of skin-friction coefficient show an agreement with hot-wire anemometry to withinforup to. A rough surface of staggered distributed cubes with large relative height,, is also investigated. Results indicate the flow reaches the fully rough regime, at the measurement location, for the entire range of Reynolds number. Furthermore, the values of skin friction agree with existing estimations from alternative methods.Graphical abstractDrawings of the floating-element (FE) balance and skin-friction measurements for a smooth-wall boundary layer. On top: slice along the X-Y plane and top view (left) next to their corresponding pictures (right). Colors highlight distinct subsystems, namely, the floating frame for drag measurement (yellow), the pitching moment mechanism (red) and the acquisition system (blue). Bottom left: smooth-wall setup and calibration system. The FE is flush mounted with the wind tunnel floor and the pulley is attached to a linear traverse which allows setting its position at different wall-normal locations. During calibration, a lid is removed to make way for the pulley to move into the test section. A wire is then strung over to suspend the weights. Bottom right: Skin friction over a smooth wall. The inset indicates the relative discrepancy between the FE values (blue) and those inferred from hot-wire anemometry of the boundary-layer profile (red).
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DOI：
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发表时间：
1964
期刊：
影响因子：
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作者：
Francis B O'Donnell
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DOI：
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发表时间：
2010
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影响因子：
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影响因子：
2.4
作者：
Esteban L
通讯作者：
Esteban L
影响因子：
4.6
作者：
J. M. Österlund;A. Johansson;H. Nagib;M. Hites
通讯作者：
J. M. Österlund;A. Johansson;H. Nagib;M. Hites
影响因子：
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作者：
E. Doğan;R. Hanson;B. Ganapathisubramani
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