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Open AccessArticle

An Experimental Method for Generating Shear-Free Turbulence Using Horizontal Oscillating Grids

1
National Inland Waterway Regulation Engineering Research Center, Chongqing Jiaotong University, Chongqing 400074, China
2
Key Laboratory of Ministry of Education for Hydraulic and Water Transport Engineering, Chongqing Jiaotong University, Chongqing 400074, China
*
Author to whom correspondence should be addressed.
Water 2020, 12(2), 591; https://doi.org/10.3390/w12020591
Received: 7 January 2020 / Revised: 4 February 2020 / Accepted: 18 February 2020 / Published: 21 February 2020
(This article belongs to the Section Hydraulics and Hydrodynamics)
An experimental apparatus driven by horizontal oscillating grids in a water tank is proposed for generating shear-free turbulence, which is measured using Particle Image Velocimetry (PIV). The performances of the proposed apparatus are investigated through the instantaneous and root-mean-square (RMS) velocity, Reynolds stress, length and time scale, frequency spectra and dissipation rate. Results indicate that the turbulence at the core region of the water tank, probably 8 cm in length, is identified to be shear-free. The main advantage of the turbulence driven by horizontal oscillating mode is that the ratios of the longitudinal turbulent intensities to the vertical values are between 1.5 and 2.0, consistent with those ratios in open-channel flows. Additionally, the range of the length scale can span the typical sizes of suspended particles in natural environments, and the dissipation rate also agrees with those found in natural environments. For convenience of experimental use, a formula is suggested to calculate the RMS flow velocity, which is linearly proportional to the product of oscillating stroke and frequency. The proposed experimental method in this study appears to be more appropriate than the traditional vertical oscillating mode for studying the fundamental mechanisms of vertical migratory behavior of suspended particles and contaminants in turbulent flows. View Full-Text
Keywords: experimental method; shear-free turbulence; RMS velocity; horizontal oscillating grid; PIV experimental method; shear-free turbulence; RMS velocity; horizontal oscillating grid; PIV
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MDPI and ACS Style

Li, W.; Zhang, P.; Yang, S.; Fu, X.; Xiao, Y. An Experimental Method for Generating Shear-Free Turbulence Using Horizontal Oscillating Grids. Water 2020, 12, 591.

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