Vertical mass transfer in open channel flow

1968 ◽  
Author(s):  
Harvey E. Jobson
Keyword(s):  
Mass Transfer ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow

The relationship between surface-renewal and bursting motions in an open-channel flow

1989 ◽  
Vol 203 ◽  
pp. 103-123 ◽  
Author(s):  
Satoru Komori ◽  
Yasuhiro Murakami ◽  
Hiromasa Ueda
Keyword(s):  
Mass Transfer ◽  
Methylene Blue ◽  
Free Surface ◽  
Transfer Coefficient ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Liquid Interface ◽  
Surface Renewal ◽  
Buffer Region

Surface-renewal motions in the interfacial region below a gas-liquid interface were experimentally investigated in relation to bursting motions in the wall region. To estimate the frequency of the appearance of surface-renewal eddies, mass-transport experiments with methylene-blue solution, together with velocity measurements, were done in an open-channel flow. The instantaneous concentration of methylene-blue tracer emitted from a point source positioned in the buffer layer was measured at the free surface downstream from the source by an optical probe. Instantaneous streamwise velocity was measured using a laser-Doppler velocimeter at a position in the buffer region. Frequencies of both surface-renewal and bursting events were computed from these concentration and velocity signals using a conditional-averaging method. In order to clarify whether the surface-renewal eddies actually dominate mass transfer across the gas-liquid interface, gas-absorption experiments were added. Carbon dioxide was absorbed into the water flow across the calm free surface and its mass-transfer coefficient on the liquid side was measured under the same flow conditions as used in the above mass-transport experiments. The results show that the surface-renewal motions originate in the bursting motions which vigorously occur in the buffer region. That is, the decelerated fluid which is strongly lifted towards the outer layer by bursting almost always arrives at the free surface and renews the free surface. The frequency of the surface renewal, as well as the bursting frequency, is uniquely determined by the wall variables or the outer-flow variables and the Reynolds number. Mass transfer across the gas-liquid interface is dominated by the large-scale surface-renewal eddies, and the mass-transfer coefficient on the liquid side is proportional to the square-root of the surface-renewal frequency.

The liquid‐gas mass transfer coefficient in open channel flow is correlated to the turbulent kinetic energy at the interface

2020 ◽  
Vol 98 (5) ◽  
pp. 1191-1201
Author(s):  
Fanny Springer ◽  
Lucie Carrera ◽  
Gislain Lipeme Kouyi ◽  
Alejandro Claro‐Barreto ◽  
Pierre Buffiere
Keyword(s):  
Mass Transfer ◽  
Kinetic Energy ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Turbulent Kinetic Energy ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow

Ionic mass transfer in open channel flow

1976 ◽  
Vol 21 (2) ◽  
pp. 143-147 ◽  
Author(s):  
S. Mohanta ◽  
T.Z. Fahidy
Keyword(s):  
Mass Transfer ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Ionic Mass Transfer ◽  
Ionic Mass

scholarly journals Direct numerical simulation of turbulent mass transfer at the surface of an open channel flow

2022 ◽  
Vol 933 ◽  
Author(s):  
Michele Pinelli ◽  
H. Herlina ◽  
J.G. Wissink ◽  
M. Uhlmann
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Channel Flow ◽  
Schmidt Number ◽  
Open Channel ◽  
Open Channel Flow ◽  
Reynolds Numbers ◽  
Transfer Velocity

We present direct numerical simulation results of turbulent open channel flow at bulk Reynolds numbers up to 12 000, coupled with (passive) scalar transport at Schmidt numbers up to 200. Care is taken to capture the very large-scale motions which appear already for relatively modest Reynolds numbers. The transfer velocity at the flat, free surface is found to scale with the Schmidt number to the power ‘ $-1/2$ ’, in accordance with previous studies and theoretical predictions for uncontaminated surfaces. The scaling of the transfer velocity with Reynolds number is found to vary, depending on the Reynolds number definition used. To compare the present results with those obtained in other systems, we define a turbulent Reynolds number at the edge of the surface-influenced layer. This allows us to probe the two-regime model of Theofanous et al. (Intl J. Heat Mass Transfer, vol. 19, 1976, pp. 613–624), which is found to correctly predict that small-scale vortices significantly affect the mass transfer for turbulent Reynolds numbers larger than 500. It is further established that the root mean square of the surface divergence is, on average, proportional to the mean transfer velocity. However, the spatial correlation between instantaneous surface divergence and transfer velocity tends to decrease with increasing Schmidt number and increase with increasing Reynolds number. The latter is shown to be caused by an enhancement of the correlation in high-speed regions, which in turn is linked to the spatial distribution of surface-parallel vortices.

MODELING THE ORGANIC REMOVAL AND OXYGEN CONSUMPTION BY BIOFILMS IN AN OPEN-CHANNEL FLOW

1994 ◽  
Vol 30 (2) ◽  
pp. 53-61 ◽  
Author(s):  
Shiyu Li ◽  
Guang Hao Chen
Keyword(s):  
Water Quality ◽  
Oxygen Consumption ◽  
River Water ◽  
Channel Flow ◽  
Diffusion Layer ◽  
Open Channel ◽  
Open Channel Flow ◽  
River Water Quality ◽  
Monod Kinetics ◽  
Organic Removal

A mathematical model is proposed to predict the removal of dissolved organic substances and the consumption of dissolved oxygen by attached biofilms in an open-channel flow. The model combines the biofilm equations with the conventional Streeter–Phelps type equations of river water quality by considering the mass transfer of organics and oxygen in the river water through the diffusion layer into the biofilm. It is assumed that the diffusion and reaction within the biofilm are of steady-state, and follow Monod kinetics. The model is solved numerically with a trial-and-error method. The simulation results of the model for an ideal case of river flow and biofilm show that the organic removal rate and oxygen consumption rate caused by the biofilm are greater than that by suspended biomass. The effects of diffusion layer thickness, flow velocity, and biofilm thickness on the change of river water quality are discussed.

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