scholarly journals DIRECT NUMERICAL SIMULATIONS OF SECONDARY FLOWAND AIR-WATER GAS TRANSFER IN OPEN-CHANNEL TURBULENCE

2015 ◽  
Vol 71 (2) ◽  
pp. I_765-I_772
Author(s):  
Ryosuke TERAOKA ◽  
Yuji SUGIHARA ◽  
Takuya NAKAGAWA ◽  
Nobuhiro MATSUNAGA
Keyword(s):  
Numerical Simulations ◽  
Open Channel ◽  
Direct Numerical Simulations ◽  
Gas Transfer ◽  
Water Gas

Interaction of surface waves with turbulence: direct numerical simulations of turbulent open-channel flow

1995 ◽  
Vol 286 ◽  
pp. 1-23 ◽  
Author(s):  
Vadim Borue ◽  
Steven A. Orszag ◽  
Ilya Staroselsky
Keyword(s):  
Free Surface ◽  
Numerical Simulations ◽  
Channel Flow ◽  
Gravity Waves ◽  
Open Channel ◽  
Open Channel Flow ◽  
Surface Region ◽  
Direct Numerical Simulations ◽  
Turbulence Production ◽  
Wind Sea

We report direct numerical simulations of incompressible unsteady open-channel flow. Two mechanisms of turbulence production are considered: shear at the bottom and externally imposed stress at the free surface. We concentrate upon the effects of mutual interaction of small-amplitude gravity waves with in-depth turbulence and statistical properties of the near-free-surface region. Extensions of our approach can be used to study turbulent mixing in the upper ocean and wind–sea interaction, and to provide diagnostics of bulk turbulence.

scholarly journals SIMULATING AIR-WATER GAS TRANSFER AT HIGH SCHMIDT NUMBER USING DYNAMICS OF OPEN-CHANNEL TURBULENCE

2016 ◽  
Vol 4 (1) ◽  
pp. 52-58 ◽  
Author(s):  
Yuji SUGIHARA ◽  
Daisuke NAKAGAWA ◽  
Ryosuke TERAOKA ◽  
Koji SHIONO
Keyword(s):  
Schmidt Number ◽  
Open Channel ◽  
Gas Transfer ◽  
High Schmidt Number ◽  
Water Gas

scholarly journals Bedform dynamics from coupled bed-flow direct numerical simulations

2019 ◽  
Vol 261 ◽  
pp. 03001
Author(s):  
N. Zgheib ◽  
J.J. Fedele ◽  
D.C.J.D. Hoyal ◽  
M.M. Perillo ◽  
S. Balachandar
Keyword(s):  
Flow Field ◽  
Numerical Simulations ◽  
Immersed Boundary Method ◽  
Open Channel ◽  
Numerical Approach ◽  
Direct Numerical Simulations ◽  
Immersed Boundary ◽  
Sediment Bed ◽  
Turbulent Flow Field ◽  
Pseudo Spectral

We present results of time-evolving coupled direct numerical simulations between an erodible bed and an overlying pressure-driven, turbulent flow field. A total of 6 simulations are considered, the details of which are shown in Table 1. The numerical setup consists of a horizontally periodic open channel, and the simulations are run at a shear Reynolds number of Reτ = 180. The coupling between the spatially and temporally evolving sediment bed and the flow field is enforced through the explicit immersed boundary method (IBM) of Uhlmann [1]. The flow field is fully resolved and is obtained by integrating the conservation of mass and momentum equations using a pseudo spectral code [2]. On the other hand, the sediment bed is modelled via the Exner equation [3]. Details about the numerical approach are available in [4-5].

scholarly journals Direct numerical simulations of stratified open channel flows

2011 ◽  
Vol 318 (2) ◽  
pp. 022009 ◽  
Author(s):  
E Deusebio ◽  
P Schlatter ◽  
G Brethouwer ◽  
E Lindborg
Keyword(s):  
Numerical Simulations ◽  
Open Channel ◽  
Direct Numerical Simulations ◽  
Channel Flows ◽  
Open Channel Flows

Air–water gas transfer and near-surface motions

2013 ◽  
Vol 733 ◽  
pp. 588-624 ◽  
Author(s):  
Damon E. Turney ◽  
Sanjoy Banerjee
Keyword(s):  
Open Channel ◽  
Breaking Waves ◽  
Capillary Waves ◽  
Gas Transfer ◽  
Water Interface ◽  
Surface Renewal ◽  
Near Surface ◽  
Transfer Rates ◽  
Air Water Interface ◽  
Water Gas

AbstractRates of gas transfer between air and water remain difficult to predict or simulate due to the wide range of length and time scales and lack of experimental observations of near-surface fluid velocity and gas concentrations. The surface renewal model (SR) and surface divergence model (SD) provide the two leading models of the process, yet they remain poorly tested by observation because near-surface velocity is difficult to measure. To contribute to evaluation of these models, we apply new techniques called interfacial particle imaging velocimetry (IPIV) and three-dimensional IPIV (3D-IPIV) for measuring water velocities within a millimetre of a moving deformable air–water interface. The latter technique (3D-IPIV) simultaneously measures the air–water interface topography. We apply these techniques to turbulent open-channel water flows and wind-sheared water flows with microscale breaking waves. Additional measurements made for each flow condition are bulk turbulent length scales, bulk turbulent velocity scales, air–water gas transfer rates, friction velocities, and wave characteristics. We analyse these data to test the surface divergence models for interfacial gas transfer. The first test is of predictions from the Banerjee (Ninth International Heat Transfer Conference, Keynote Lectures, vol. 1, 1990, pp. 395–418, Hemisphere Press) surface divergence model for gas transfer for homogeneous isotropic turbulence interacting with a planar free surface. The second test is of predictions from the McCready, Vassiliadou and Hanratty (AIChE J., vol. 32(7), 1986, pp. 1108–1115) surface divergence model, as applied in both open-channel flow and wind-sheared wavy flows. We find the predictions of the Banerjee and McCreadyet al. models to agree with the experimental data taken for open-channel flow conditions. On the other hand, for wind-driven flows with wind waves we find disagreement between the McCreadyet al. predictions and our direct measurements of the gas transfer coefficient. The cause of the disagreement is investigated by Lagrangian tracking of surface divergence of surface water patches, and by analysis of the corresponding Lagrangian time series with advection–diffusion concepts. A quantitative criterion based on surface divergence strength and lifetime is proposed to distinguish the effectiveness of each near-surface motion toward causing interfacial gas transfer. Capillary waves are found to contribute to surface divergence but to have too short a time scale to cause interfacial gas transfer. As wind speed increases, the presence and intensity on the air–water interface of capillary waves and other ineffective near-surface motions is diminished by the rise of turbulent wakes from microscale breaking waves thus causing the disagreement of the surface divergence model’s predicted transfer rates with measurements. A model of air–water gas transfer that combines the surface renewal and surface divergence models is formulated and found to agree with the data from both open-channel flows and wind-driven flows without requiring an empirical coefficient.

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