Observations on Free-Surface Deformation and Air Entrainment Process in Supercritical Open Channel Flows

2019 ◽  
Author(s):  
WANGRU WEI ◽  
JUN DENG
Keyword(s):  
Free Surface ◽  
Open Channel ◽  
Surface Deformation ◽  
Air Entrainment ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Entrainment Process ◽  
Free Surface Deformation

Free-surface air entrainment in open-channel flows

2016 ◽  
Vol 60 (6) ◽  
pp. 893-901 ◽  
Author(s):  
WangRu Wei ◽  
WeiLin Xu ◽  
Jun Deng ◽  
Zhong Tian ◽  
FaXing Zhang
Keyword(s):  
Free Surface ◽  
Open Channel ◽  
Air Entrainment ◽  
Channel Flows ◽  
Open Channel Flows

Coherent Structures In Open-Channel Flows Over a Fixed Dune

2005 ◽  
Vol 127 (5) ◽  
pp. 858-864 ◽  
Author(s):  
Wusi Yue ◽  
Ching-Long Lin ◽  
Virendra C. Patel
Keyword(s):  
Free Surface ◽  
Coherent Structures ◽  
Open Channel ◽  
Surface Deformation ◽  
Channel Flows ◽  
Mean Flow ◽  
Open Channel Flows ◽  
Near Surface ◽  
Numerical Predictions ◽  
The Mean

Turbulent open-channel flow over a two-dimensional laboratory-scale dune is studied using large eddy simulation. Free surface motion is simulated using level set method. Two subgrid scale models, namely, dynamic Smagorinsky model and dynamic two-parameter model, are employed for assessing model effects on the free surface flow. The present numerical predictions of mean flow field and turbulence statistics are in good agreement with experimental data. The mean flow can be divided into two zones, an inner zone where turbulence strongly depends on the dune bed geometry and an outer layer free from the direct influence of the bed geometry. Streaky structures are observed in the wall layer after flow reattachment. Quadrant two events are found to prevail in near-wall and near-surface motions, indicating the predominance of turbulence ejections in open-channel flows. Large-scale coherent structures are produced behind the dune crest by a strong shear layer riding over the recirculation zone. These quasistreamwise tubelike vortical structures are transported downstream with the mean flow and most are destructed before arriving at the next crest. Free surface deformation is visualized, demonstrating complex patterns of upwelling and downdraft.

Additional spanwise vortices near the free surface in open channel flows

2021 ◽  
Vol 924 ◽  
Author(s):  
Yanchong Duan ◽  
Qiang Zhong ◽  
Guiquan Wang ◽  
Qigang Chen ◽  
Fujun Wang ◽  
...  
Keyword(s):  
Free Surface ◽  
Open Channel ◽  
Channel Flows ◽  
Open Channel Flows

Abstract

scholarly journals Flow Structures of the Air-Water Layer in the Free Surface Region of High-Speed Open Channel Flows

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Feng Jiang ◽  
Weilin Xu ◽  
Jun Deng ◽  
Wangru Wei
Keyword(s):  
Free Surface ◽  
Layer Thickness ◽  
High Speed ◽  
Open Channel ◽  
Water Layer ◽  
Channel Flows ◽  
Flow Structures ◽  
Air Velocity ◽  
Open Channel Flows ◽  
The Relationship

In hydraulic engineering, intense free surface breakups have been observed to develop in high-speed open channel flows, resulting in a mixed air-water layer near the free surface that grows with the development of self-aeration. This region is characterized by a substantial number of droplets coexisting with an induced air layer above. Little information about this droplet layer is currently available and no practicable approach has been proposed for predicting the parameters of the induced air layer based on the related flow structures in the droplet layer. In this research, laboratory experiments were accordingly conducted to observe the detailed droplet layer development in terms of layer thickness, droplet size, and frequency distributions under comparative flow conditions. Based on the simplified droplet layer roughness determined using the experimentally measured mean droplet size, the classical power-law of boundary layer theory was applied to provide an analytical solution for the air velocity profile inside the air layer. The relationship of air layer growth to droplet layer thickness, which is a key factor when determining the air velocity distribution, was also established, and the analytical results were proven to be in reasonable agreement with air velocity profiles presented in the literature. By determining the relationship between droplet layer properties and air velocity profiles, the study establishes a basis for the improved modeling of high-speed open channel flows.

scholarly journals Fundamental Properties of Free Surface Oscillation in Dead Zone of Open Channel Flows

1995 ◽  
Vol 39 ◽  
pp. 779-784 ◽  
Author(s):  
Ichiro KIMURA ◽  
Takashi HOSODA ◽  
Yoshio MURAMOTO ◽  
Ryo YASUNAGA
Keyword(s):  
Free Surface ◽  
Open Channel ◽  
Dead Zone ◽  
Channel Flows ◽  
Surface Oscillation ◽  
Open Channel Flows ◽  
Fundamental Properties

NUMERICAL STUDY ON FREE-SURFACE TURBULENCE IN THERMALLY-STRATIFIED OPEN-CHANNEL FLOWS

2015 ◽  
Vol 71 (4) ◽  
pp. I_583-I_588
Author(s):  
Ryosuke TERAOKA ◽  
Yuji SUGIHARA ◽  
Takuya NAKAGAWA ◽  
Nobuhiro MATSUNAGA
Keyword(s):  
Free Surface ◽  
Open Channel ◽  
Numerical Study ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Surface Turbulence ◽  
Free Surface Turbulence
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