A quality control method by ultrasonic vibration energy and diagnosis system at trimming process |
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Authors: | Shin-Jeong Kang Mamoru Tanahashi Toshio Miyauchi |
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Affiliation: | (1) Seocho Technology Appraisal Center, Kibo Technology Fund, Japan;(2) Department of Mechanical and Aerospace Engineering, Tokyo Institute of Technology, Tokyo, Japan |
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Abstract: | To investigate a relation between vortex clusters and large-scale structures in the outer layer of wall turbulence, direct
numerical simulations of turbulent channel flows have been conducted up toRe
τ
= 1270. The vortex clusters in the outer layer consist coherent fine scale eddies (CFSEs) of which diameter and maximum azimuthal
velocity are scaled by the Kolmogorov length and the Kolmogorov velocity. The CFSE clusters are inside the large-scale structure,
which contributes to the streamwise velocity deficit The scale of those clusters tends to be enlarged with the increase of
a distance from the wall. The CFSE clusters are composed of the relatively strong CFSEs, which play an important role in the
production of the Reynolds shear stress and the dissipation rate of the turbulent kinetic energy. The most expected maximum
azimuthal velocity of the CFSEs in these low-momentum regions of the outer layer is 30–70% fester compared with those of the
CFSEs in unconditioned regions (i.e. all regions of the outer layer), while the most expected diameter of the CFSEs is not changed greatly. |
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Keywords: | Turbulent channel flow Direct numerical simulation Large-scale structure Coherent fine scale eddy |
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