Calculation Method about Vertical Distribution of Saturated Sediment Concentration Based on Exchange Equilibrium

2013 ◽  
Vol 405-408 ◽  
pp. 2287-2291
Author(s):  
Xiao Xiang Feng ◽  
Pei Jiu Yue
Keyword(s):  
Diffusion Coefficient ◽  
Vertical Distribution ◽  
Diffusion Theory ◽  
Sediment Concentration ◽  
Exchange Equilibrium ◽  
Sediment Diffusion Coefficient ◽  
The Difference ◽  
The Vertical Distribution ◽  
And Diffusion ◽  
Key Parameter

Diffusion theory is the leading one which is used to study the vertical distribution of sediment concentration. And diffusion coefficient is a key parameter to determine the vertical distribution of suspended sediment. First of all, the calculation methods are introduced based on the momentum transfer theory and fluctuating velocity. According to the sediment equation of exchange equilibrium in vertical, the new expression is obtained for sediment diffusion coefficient and the vertical distribution of sediment concentration. By the flume experimental data and field data in natural river, the difference is analyzed among the different expressions.

scholarly journals Fractal derivative model for the transport of the suspended sediment in unsteady flows

2018 ◽  
Vol 22 (Suppl. 1) ◽  
pp. 109-115 ◽  
Author(s):  
Shiqian Nie ◽  
Hong Sun ◽  
Xiaoting Liu ◽  
Wang Ze ◽  
Mingzhao Xie
Keyword(s):  
Vertical Distribution ◽  
Unsteady Flow ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Spatial Location ◽  
Sediment Concentration ◽  
Equation Model ◽  
Advection Dispersion ◽  
Fractal Derivative ◽  
The Vertical Distribution

This paper makes an attempt to develop a Hausdorff fractal derivative model for describing the vertical distribution of suspended sediment in unsteady flow. The index of Hausdorff fractal derivative depends on the spatial location and the temporal moment in sediment transport. We also derive the approximate solution of the Hausdorff fractal derivative advection-dispersion equation model for the suspended sediment concentration distribution, to simulate the dynamics procedure of suspended concentration. Numerical simulation results verify that the Hausdorff fractal derivative model provides a good agreement with the experimental data, which implies that the Hausdorff fractal derivative model can serve as a candidate to describe the vertical distribution of suspended sediment concentration in unsteady flow.

scholarly journals Theoretical Model of Suspended Sediment Concentration in a Flow with Submerged Vegetation

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1656 ◽  
Author(s):  
Da Li ◽  
Zhonghua Yang ◽  
Zhaohua Sun ◽  
Wenxin Huai ◽  
Jianhua Liu
Keyword(s):  
Vertical Distribution ◽  
Suspended Sediment ◽  
Schmidt Number ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Submerged Vegetation ◽  
Distribution Profile ◽  
Turbulent Schmidt Number ◽  
Rouse Number ◽  
The Vertical Distribution

Vegetation in natural river interacts with river flow and sediment transport. This paper proposes a two-layer theoretical model based on diffusion theory for predicting the vertical distribution of suspended sediment concentration in a flow with submerged vegetation. The suspended sediment concentration distribution formula is derived based on the sediment and momentum diffusion coefficients through the inverse of turbulent Schmidt number ( S c t ) or the parameter η which is defined by the ratio of sediment diffusion coefficient to momentum diffusion coefficient. The predicted profile of suspended sediment concentration moderately agrees with the experimental data. Sensitivity analyses are performed to elucidate how the vertical distribution profile responds to different canopy densities, hydraulic conditions and turbulent Schmidt number. Dense vegetation renders the vertical distribution profile uneven and captures sediment particles into the vegetation layer. For a given canopy density, the vertical distribution profile is affected by the Rouse number, which determines the uniformity of the sediment on the vertical line. A high Rouse number corresponds to an uneven vertical distribution profile.

A Model Study on the Diffusion and the Dilution of Low Molecular Weight Gaseous Components through Cigarette Paper during Smoking

1977 ◽  
Vol 9 (3) ◽  
Author(s):  
M. Muramatsu ◽  
T. Mikami ◽  
N. Naito ◽  
H. Tomita
Keyword(s):  
Diffusion Coefficient ◽  
Gas Mixture ◽  
Low Molecular Weight ◽  
Diffusion Loss ◽  
Front End ◽  
Model Study ◽  
The Difference ◽  
Cigarette Paper ◽  
And Diffusion ◽  
Standard Gas

AbstractThe effects of diffusion and dilution on the concentration of gaseous components have been studied by a model consisting of unlit cigarettes differing in paper porosity and length, and a standard gas mixture. Results are as follows: The difference in the concentration of gaseous components between the front and butt end of the cigarette during the puff increases with cigarette length and paper porosity, and also depends on the diffusion coefficient of respective components through the cigarette paper. These changes could be explained mainly by the diffusion loss through the paper in the case of the cigarette with ordinary paper, but by both dilution with air through the paper and diffusion loss in the case of the cigarette with perforated paper. Subsequently, the levels of gaseous components such as carbon monoxide in the exit stream become lower in the Iatter cigarette. In addition, the following equation, which can fully account for these changes, has been derived:where C1i and C0i are the concentrations of the component i at the front and butt end, respectively, L the cigarette length, r the cigarette radius, s the thickness of paper, U0 and U1 the apparent linear gas velocities at the butt and front end, respectively, and Di the diffusion coefficient of component i through the paper.

CONGENERIC OCCURRENCES OF SPECIES OF DIAPTOMUS IN SOUTHERN ONTARIO LAKES

1967 ◽  
Vol 45 (1) ◽  
pp. 81-90 ◽  
Author(s):  
F. H. Rigler ◽  
R. R. Langford
Keyword(s):  
Vertical Distribution ◽  
Calanoid Copepods ◽  
Southern Ontario ◽  
Ecological Separation ◽  
The Difference ◽  
Limnocalanus Macrurus ◽  
The Vertical Distribution

The vertical distribution of adult calanoid copepods was studied in 100 lakes in southern Ontario. In addition to Epischura lacustris, Limnocalanus macrurus, and Senecella calanoides, seven species of Diaptomus were recorded. Diaptomus minutus and D. oregonensis, the commonest species, coexisted in 45% of the lakes. In 9% a third species was also present. Coexisting populations of D. minutus and D. oregonensis were not well separated by their vertical distribution, but a third species, if present, occurred in deeper water than these two. Size displacement does not contribute to the ecological separation of D. minutus and D. oregonensis. The difference in size between populations coexisting in the same lake is less than between populations living in separate lakes.

scholarly journals IDV model for suspended sand transport under waves in ripple regime

2000 ◽  
Vol 22 (2) ◽  
pp. 71-86
Author(s):  
Dang Huu Chung
Keyword(s):  
Diffusion Coefficient ◽  
Sediment Transport ◽  
Vertical Distribution ◽  
Sediment Concentration ◽  
Measured Data ◽  
Irregular Waves ◽  
Sand Transport ◽  
Suspended Sediment Transport ◽  
Theoretical Studies ◽  
Effective Wave

In this paper the results of theoretical studies on suspended sand transport under irregular waves in the ripple regime are presented. The results from the lDV model, which simulates the instantaneous velocity and sand concentration from close to the bed up to higher in the water column are obtained. The model is based on the classical diffusion approach taking both the turbulence-related and the effective wave related diffusion into account. It shows that the time-averaged sand concentrations can be simulated reasonably well in the ripple regime using calibrated equations. Especially, the proposed formula for the diffusion coefficient by wave, considerably improved the behavior of vertical distribution of upended sediment concentration. Finally, the wave related suspended sediment transport in depth-integration is computed and compared with the measured data. The accuracy of the suspended transport was found to be strongly dependent on using measured data or predictive formula for concentration at the bed boundary.

Solvent diffusion in porous low-k dielectric films

2003 ◽  
Vol 766 ◽  
Author(s):  
Denis Shamiryan ◽  
Karen Maex
Keyword(s):  
Dielectric Constant ◽  
Diffusion Coefficient ◽  
Porous Matrix ◽  
Silicon Oxycarbide ◽  
Dielectric Films ◽  
Polar Solvents ◽  
Low Dielectric ◽  
The Difference ◽  
Low K ◽  
And Diffusion

AbstractPorous materials are being investigated as low dielectric constant (low-k) materials. While porosity decreases the k-value of a material by decreasing its density, it simultaneously allows unwanted adsorption and diffusion of chemicals inside the porous matrix. To investigate this, different porous low-k materials, specifically silicon oxycarbide (SiOCH), methylsilsesquioxane (MSQ), and a polymer, were exposed to polar (ethanol) and non-polar (toluene) solvents. A difference in diffusion of polar and non-polar solvents would be an indication of the density of polar centers which attract polar molecules (such as water) and increase the dielectric constant of a film. The diffusion coefficient for toluene at room temperature was found to be approximately 2×10-5 cm2/sec for MSQ (40% porosity), 10-7 cm2/sec for SiOCH (7% porosity), 2×10-8 cm2/sec for the polymer. The observed diffusion can be described by a model of a viscous flow in a porous medium. The toluene/ethanol diffusion coefficient ratios were 4.4, 1.3, 1 for MSQ, SiOCH, and the polymer, respectively. The difference in toluene/ethanol diffusion can potentially be used to screen a material's affinity for water adsorption.

scholarly journals Electron Drift and Diffusion in Parahydrogen at 77°K

1968 ◽  
Vol 21 (5) ◽  
pp. 637 ◽  
Author(s):  
RW Crompton ◽  
AI McIntosh
Keyword(s):  
Diffusion Coefficient ◽  
Energy Distribution ◽  
Vibrational Excitation ◽  
Electron Drift ◽  
Thermal Region ◽  
Dominant Process ◽  
Series Of Experiments ◽  
Normal Hydrogen ◽  
The Difference ◽  
And Diffusion

This paper reports a series of experiments to measure electron diffusion and drift in pure parahydrogen at 77° K. Tables of data are given for the electron drift velocity W in the range 1.2 X l0−19 ≤ E/N ≤ 9.5 x l0−17 V cm2 and for the ratio of diffusion coefficient to mobility D/μ for 2 X 10−20 ≤ E/N ≤ 6 X 10−17 V cm2. As expected, these data are indistinguishable from the data for normal hydrogen in the thermal region and at the higher values of E/N where vibrational excitation is the dominant process controlling the electron energy distribution. However, at intermediate values of E/N, the values of W and D/μ differ by more than 10 and 20% respectively from the corresponding values in normal hydrogen, demonstrating the influence of the difference in the statistical weights of the rotational levels in the two gases.

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