Fluorescent dye measurements of the mixing and transport of wastewater discharge in the bosphorus

1995 ◽  
Vol 32 (2) ◽  
pp. 61-68 ◽  
Author(s):  
Emin Özsoy ◽  
Mohammed Abdul Latif ◽  
Sükrü T. Besiktepe ◽  
Alexander Gaines
Keyword(s):  
Extreme Events ◽  
Interfacial Layer ◽  
Lower Layer ◽  
Fluorescent Dye ◽  
Longitudinal Dispersion ◽  
Wastewater Discharge ◽  
Exchange Flows ◽  
Background Levels ◽  
Good Agreement ◽  
Mixing And Transport

The performance of the wastewater discharge of Istanbul is evaluated based on fluorescent dye technique, supported by hydrographic and current measurements. Under the normal exchange flows, as well as during extreme events of blocking, the dye essentially remained confined in the lower layer. The maximum upper layer average dye concentration in the Bosphorus was close to the background levels, while the interfacial layer values were larger. Good agreement is found between the observations and simple models of longitudinal dispersion in the lower layer of the Bosphorus.

Longitudinal dispersion in open channel flow with suspended canopies

2016 ◽  
Vol 74 (3) ◽  
pp. 722-728 ◽  
Author(s):  
Wenxin Huai ◽  
Chengguang Li
Keyword(s):  
Dispersion Coefficient ◽  
Fate And Transport ◽  
Longitudinal Dispersion ◽  
Zone Model ◽  
Shear Stresses ◽  
Maximum Point ◽  
Longitudinal Dispersion Coefficient ◽  
Flow Disturbances ◽  
Tracer Experiments ◽  
Good Agreement

Suspended canopies can cause flow disturbances such as reducing velocities within the canopy, and increasing flow beneath the canopy. Flow modifications by canopies dramatically affect the fate and transport of sediment, nutrients, contaminants, dissolved oxygen, and fauna in aquatic systems. A three-zone model is presented here to predict the longitudinal dispersion coefficient by simplifying Chikwendu's N-zone model. To validate the model, both flow field and tracer experiments were conducted using a straight rectangular Plexiglas flume, with rigid circular rods as the modeled suspended canopies. The result shows that velocities increased above the flume bed and maximized at a point between the canopies and flume bed. Above that point, streamwise velocities decreased into and within the canopies. Reynolds shear stresses were largest at the canopy interface and smallest (zero) at the velocity maximum point. Good agreement between the modeled results and experimental data shows that the model can effectively predict the longitudinal dispersion coefficient in open channels with suspended canopies.

Role of Interfacial Surfactant Layers in the Thermal Conductivity of Nanofluids

2012 ◽  
Vol 531-532 ◽  
pp. 535-538
Author(s):  
Liu Yang ◽  
Kai Du ◽  
Yun Long Wu ◽  
Shuai Yang Bao
Keyword(s):  
Thermal Conductivity ◽  
Interfacial Layer ◽  
Langmuir Adsorption ◽  
Adsorption Theory ◽  
Proposed Model ◽  
Classical Models ◽  
Interfacial Surfactant ◽  
S Model ◽  
Good Agreement

Various mechanisms and correlations have been developed for prediction of thermal conductivity of nano-suspensions. However, seldom theoretical researches on thermal conductivity of nanofluids containing surfactant are found. In this work, a thermal conductivity prediction-model of nanofluid containing surfactants is proposed based on Leong et al.’s model and Langmuir adsorption theory by considering the interfacial surfactant layers. The thickness of the interfacial layer is defined by Langmuir adsorption theory. Compared with the experimental data available in the literature on thermal conductivity of nanofluid containing surfactants, the calculated values on the proposed model have been verified that the proposed models show reasonably good agreement with the experimental results and give better predictions for the effective thermal conductivity of nanofluids compared to existing classical models.

scholarly journals Stratification effects on shoaling Internal Solitary Waves

2021 ◽  
Author(s):  
Sam Hartharn-Evans ◽  
Magda Carr ◽  
Marek Stastna ◽  
Peter Davies
Keyword(s):  
Density Gradient ◽  
Solitary Waves ◽  
Numerical Experiments ◽  
Lower Layer ◽  
Internal Solitary Waves ◽  
Topographic Slope ◽  
Numerical Studies ◽  
The World ◽  
Upper Boundary ◽  
Mixing And Transport

<p>Shoaling is a key mechanism by which Internal Solitary Waves (ISWs) dissipate energy, induce mixing, and transport sediment. Past studies of shoaling ISWs in a three-layer stratification (with homogeneous upper and lower layers separated by a thin pycnocline layer) have identified a classification system where waves over the shallowest slopes undergo fission, whilst over steeper slopes, the breaking type changes from surging, through collapsing to plunging as a function of increasing internal Irribaren number (Ir) defined with the topographic slope, s, and the incident wave’s amplitude and wavelength, A<sub>w</sub> and L<sub>w </sub>respectively, as <img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.9fb46536f70067154311161/sdaolpUECMynit/12UGE&app=m&a=0&c=d84eaf790c6586a46ed8fca09040fcd7&ct=x&pn=gnp.elif&d=1" alt="" width="117" height="24">. Here, a combined numerical and laboratory study extends this prior work into new stratifications, representing the diversity of ocean structures across the world. Numerical results were able to successfully reproduce past studies in the three-layer stratification, and those in the two-layer stratification in the laboratory. Where a linear stratified layer overlays a homogeneous lower layer (two-layer stratification), it is found that plunging dynamics are inhibited by the density gradient throughout the upper layer, instead forming collapsing-type breakers. In numerical experiments, where the density gradient is continuous throughout the full water column (linear stratification), not only are the plunging dynamics inhibited, but the density gradient at the bottom boundary also prevents the formation of collapsing dynamics, instead all waves in this stratification either fission, or form surging breakers. Where the wave steepness is particularly high in the linear stratification, the upslope bolus formed by surging was unstable, and Kelvin-Helmholtz instabilities were observed on the upper boundary of the bolus, dynamics not previously observed in the literature. These results indicate the importance of using representative stratifications in laboratory and numerical studies of ISW behaviours.</p>

Numerical Calculation of Kerr Spectra for Magnetic Multilayered and Granular Films

2005 ◽  
Vol 475-479 ◽  
pp. 3745-3748
Author(s):  
Zhi Gao Huang ◽  
Yingbin Lin ◽  
Yan Min Yang ◽  
Feng Ming Zhang ◽  
You Wei Du
Keyword(s):  
Numerical Calculation ◽  
Kerr Effect ◽  
Interfacial Layer ◽  
Theoretical Calculations ◽  
Optical Kerr Effect ◽  
Multilayered Films ◽  
Granular Films ◽  
Damped Oscillation ◽  
Magneto Optical Kerr Effect ◽  
Good Agreement

In this paper, based on 4×4 matrix method, we present theoretical calculations of the polar magneto-optical Kerr effect for Co/Pt and MnBi multilayered films, and NixSiO2(1-x) granular films. The calculated results indicate that, (1) the simulated Kerr spectra as a function of photo-energy are in good agreement with experimental ones; (2) the maxima and the periodical and damped oscillation appear in the Kerr spectra curve with the magnetic thickness, which is important for design of the material in the future; (3) the structure of interfacial layer affect greatly the Kerr spectra, which is significant for the processing of magneto-optical material.

Buoyancy transfer across a diffusive interface

1989 ◽  
Vol 209 ◽  
pp. 1-34 ◽  
Author(s):  
Harindra J. S. Fernando
Keyword(s):  
Interfacial Layer ◽  
Cold Water ◽  
Lower Layer ◽  
Layer Structure ◽  
Constant Heat Flux ◽  
Time Interval ◽  
Interfacial Layers ◽  
Density Interface ◽  
Turbulent Eddies ◽  
Opposing Effects

An experimental investigation of various aspects of buoyancy transfer across a diffusive density interface that separates stably stratified, turbulently convecting layers of relatively fresh cold water overlying hot salty water is described. It is argued that the interfacial layer should possess a double boundary-layer structure, in which the thicknesses of the salt and heat interfacial layers are determined by a balance between the opposing effects of diffusion and entrainment. Based on this argument, a simple theory, that predicts the interfacial-layer thickness, the diffusive heat and salt fluxes across the density interface, and the time variation of the temperature and salt concentrations in the convecting layers, is proposed for the case in which the convection is driven by a constant heat flux supplied to the lower layer. During a certain time interval, the theory and experiment agree well, but thereafter distinct differences can be seen. Measurements suggest that these differences may be due to the distortion of the density interface at low interfacial stabilities by turbulent eddies, which leads to a change in the buoyancy transfer mechanism. When the Richardson number falls below a critical value Riv, the interface was found to migrate slowly upwards and the mechanism of entrainment was the detachment of thin sheets of fluid by eddies scouring the interface.

Drift velocity of spatially decaying waves in a two-layer viscous system

1995 ◽  
Vol 299 ◽  
pp. 217-239 ◽  
Author(s):  
Ismael Piedra-Cueva
Keyword(s):  
Mass Transport ◽  
Lower Layer ◽  
Mass Conservation ◽  
Layer System ◽  
Transport Velocity ◽  
Mass Transport Velocity ◽  
Lagrangian Coordinate ◽  
Progressive Waves ◽  
Lagrangian Coordinate System ◽  
Good Agreement

This paper analyses the mass transport velocity in a two-layer system induced by the action of progressive waves. First the movement inside the two layers is obtained. Next the mass transport of spatially decaying waves is calculated by solving the momentum and mass conservation equations in the Lagrangian coordinate system. Two different physical situations are analysed: the first is waves in a closed channel and the second is waves in an unbounded domain, where the steady-state mass flux may be non-zero. The influence of the viscous properties of the lower layer on the mass transport in both layers is studied. Comparison with the experiments of Sakakiyama & Bijker (1989) in a water-mud system shows good agreement. The results show that the mass transport velocity can be quite different from the velocity given by the rigid bed theory, depending on the physical properties of the lower layer.

scholarly journals Dimensionless formulation for human stability in open flows

RBRH ◽  
2016 ◽  
Vol 21 (4) ◽  
pp. 666-673 ◽  
Author(s):  
André Luiz Andrade Simões ◽  
Harry Edmar Schulz ◽  
Lafayette Dantas da Luz
Keyword(s):  
Human Body ◽  
Extreme Events ◽  
Calculated Data ◽  
Correlation Coefficients ◽  
Open Water ◽  
Dam Breaks ◽  
Dimensionless Groups ◽  
The Stability ◽  
Dimensionless Formulation ◽  
Good Agreement

ABSTRACT The stability of humans partially immersed in risky open water flows, resulting from urban flooding caused for example by dam breaks, or failures in drainage systems, or natural extreme events, is a topic of increasing interest because it involves the human safety in an environment that is more and more subjected to extreme events of hydraulic nature. The studies in this field of the applied fluid mechanics generally present equations that handle the results through dimensional quantities. These results were generally obtained in specific experiments for the evaluation of the stability of models of the human body. Intending to advance in the direction of a more general formulation, a dimensional analysis for the problem of human stability in open flows is presented here, showing dimensionless groups that represent the mentioned problem. Equations using these nondimensional groups were then developed using statistical analyses and approximations based on principles of physics and on data of the human body. The results obtained with the proposed methodology are of very good quality, presenting high correlation coefficients and good agreement between measured and calculated data.

Numerical Simulation of Study on Rupture Development Rules of Overburden Strata in Repeated Mining

2012 ◽  
Vol 433-440 ◽  
pp. 1933-1939 ◽  
Author(s):  
De Chao Wang ◽  
Yong Jie Yang ◽  
Kai Wang ◽  
Nan Nan Zhao
Keyword(s):  
Numerical Simulation ◽  
Development Time ◽  
Lower Layer ◽  
Thick Coal Seam ◽  
Upper Limit ◽  
Measurement Results ◽  
Mining Conditions ◽  
Final Crack ◽  
Good Agreement ◽  
Overburden Strata

Take 3 coal repeated mining of Luxi colliery as research background, overburden strata rupture development rules in repeated mining of thick coal seam were studied by using the methods of field measurement and numerical simulation. The results indicate that the height of overburden crack belt reduced along with the increase of goaf development time; the crack belt height of upper layer is 34.73m, the ratio of crack height and mining thickness is 15.1, the crack belt height of lower layer increased to 41.51m, but the increased trend declined, the ratio is only 13.84; the final crack height of numerical simulation is 39.4m, in good agreement with measurement results. The results have important guiding sense for predicting overburden rupture rules in the similar mining conditions and improving the upper limit.

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