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Article

PIV Study on Grid-Generated Turbulence in a Free Surface Flow

1
Institute of Astronautic Electronic Engineering, School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China
2
Institute of Process Equipment, College of Energy Engineering, Zhejiang University, Hangzhou 310027, China
3
State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China
4
Ocean College, Zhejiang University, Zhoushan 316021, China
*
Authors to whom correspondence should be addressed.
Academic Editor: Alexander Yakirevich
Water 2021, 13(7), 909; https://doi.org/10.3390/w13070909
Received: 23 February 2021 / Revised: 21 March 2021 / Accepted: 23 March 2021 / Published: 26 March 2021
(This article belongs to the Section Hydraulics and Hydrodynamics)
To investigate the feature of turbulence developing behind the filter device in a current flow, the flow fields at intermediate downstream distance of an immersed grid in an open water channel are recorded using a two-dimensional (2D) Particle Image Velocimetry (PIV) system. The measurements on a series of vertical and horizontal sections are conducted to reveal the stream-wise evolution and depth diversity of grid turbulence in the free surface flow. Unlike the previous experiments by Laser Doppler Velocimetry (LDV) and Hot-Wire Anemometry (HWA), the integral scales and space-time correlations are estimated without using the Taylor hypothesis in this paper. The distributions of mean velocity, turbulence intensity and integral scale show the transition behavior of grid-generated flow from perturbations to fully merged homogenous turbulence. The distributions of velocity and turbulence intensity become more uniform with increasing distance. While the spatial divergence of integral scale becomes more pronounced as the flow structures develop downstream. The vertical distributions of flow parameters reveal the diversity of flow characteristics in the water depth direction influenced by free surface and the outer part of turbulence boundary layer (TBL) from the channel bottom. The applicability of the newly proposed two-order elliptic approximation model for the space-time correlations of the decaying grid turbulence in channel flow is verified at different positions. The calculated convection velocity for large-scale motion and sweep velocity for small-scale motion based on this model bring a new insight into the dynamic pattern of this type of flow. View Full-Text
Keywords: open-channel flow; grid turbulence; turbulence decaying; Particle Image Velocimetry; elliptic model open-channel flow; grid turbulence; turbulence decaying; Particle Image Velocimetry; elliptic model
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MDPI and ACS Style

Yao, H.; Cao, L.; Wu, D.; Gao, Y.; Qin, S.; Yu, F. PIV Study on Grid-Generated Turbulence in a Free Surface Flow. Water 2021, 13, 909. https://doi.org/10.3390/w13070909

AMA Style

Yao H, Cao L, Wu D, Gao Y, Qin S, Yu F. PIV Study on Grid-Generated Turbulence in a Free Surface Flow. Water. 2021; 13(7):909. https://doi.org/10.3390/w13070909

Chicago/Turabian Style

Yao, Haoyu; Cao, Linlin; Wu, Dazhuan; Gao, Yangyang; Qin, Shijie; Yu, Faxin. 2021. "PIV Study on Grid-Generated Turbulence in a Free Surface Flow" Water 13, no. 7: 909. https://doi.org/10.3390/w13070909

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