Measurement of Wall Shear Stress Fluctuation with the Micro-fabricated Hot-film Sensor in a Boundary Layer of a Wall Jet
Measurement of Wall Shear Stress Fluctuation with the Micro-fabricated Hot-film Sensor in a Boundary Layer of a Wall Jet
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用微加工热膜传感器测量壁射流边界层壁剪应力脉动
DOI：
10.11395/jjsem.14.s13
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
M. Shikida and Y. Ito
中科院分区：
文献类型：
--
作者：
T. Sawada;O. Terashima;Y. Sakai;K. Nagata;M. Shikida and Y. Ito
在这项研究中，我们开发了一种热膜传感器来测量湍流中的壁面剪应力波动。传感器的加热元件作为传感部分，宽度为10μm，并被折回两次以增加其电阻以产生热量。此外，考虑到基板的加热能力，传感器的基板由1μm厚的硅片制成，以提高传感器的时间分辨率。此外，还进行了静态/动态响应测试以及壁面射流边界层中壁面剪应力波动的测量。结果表明，新开发的热膜传感器能够正确响应壁面剪应力，其滚降频率为1 kHz。此外，还发现壁面剪应力脉动的功率谱存在多个峰值。然而，在壁面附近的流向速度脉动中没有发现明显的峰值。这意味着壁面剪切应力波动更多地受到特定流动结构的影响，例如在湍流边界层中以恒定频率出现的相干涡流结构。
In this study, we developed a hot-film sensor to measure the wall shear stress fluctuation in turbulent flows. The heated element of the sensor, which acts as a sensing part is 10 μm wide and is folded back twice for increasing its electrical resistance to produce heat. In addition, the substrate of the sensor is made up of silicon wafer of 1 μm thickness for increasing the sensor’s temporal resolution, in consideration of the substrate’s heating capacity. Further, the static/dynamic response test and the measurement of the wall shear stress fluctuation in the boundary layer of the wall jet are performed. The results show that the newly developed hot-film sensor responds to the wall shear stress properly and that its roll-off frequency is 1 kHz. In addition, it is found that the power spectrum of the wall shear stress fluctuation has several peaks. However, no distinct peaks are found in that of the streamwise velocity fluctuation near the wall. This implies that the wall shear stress fluctuation is influenced more by the specified flow structure, such as the coherent vortex structure which arises with a constant frequency in a turbulent boundary layer.