scholarly journals Transient Behavior of Saltwater Wedge and Mixing Zone in Head-Controlled Coastal Aquifer: Experimental Measurements and Numerical Modeling

2019 ◽  
Vol 11 (Winter and Spring 2019) ◽  
pp. 41-51
Author(s):  
Abbasali Rezapour ◽  
Fazlolah Saghravani ◽  
Alireza Ahmadyfard ◽  
Mehdi Rezapour ◽  
◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Coastal Aquifer ◽  
Transient Behavior ◽  
Experimental Measurements ◽  
Mixing Zone ◽  
Saltwater Wedge

The Role of Coulombic Forces in Quasi-Two Dimensional Electrochemical Deposition

1996 ◽  
Vol 451 ◽  
Author(s):  
G. Marshall ◽  
P. Mocskos ◽  
F. Molina ◽  
S. Dengra
Keyword(s):  
Numerical Modeling ◽  
Pattern Formation ◽  
Electrochemical Deposition ◽  
Growth Pattern ◽  
Stokes Equations ◽  
Fluid Motion ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Dimensionless Numbers ◽  
Navier Stokes Equations

ABSTRACTRecent work demonstrates the relevant influence of convection during growth pattern formation in thin-layer electrochemical deposition. Convection is driven mainly by coulombic forces due to local charges at the tip of the aggregation and by buoyancy forces due to concentration gradients. Here we study through physical experiments and numerical modeling the regime under which coulombic forces are important. In the experimental measurements fluid motion near the growing tips of the deposit is visualized with neutrally buoyant latex spheres and its speed measured with videomicroscope tracking techniques and image processing software. The numerical modeling consists in the solution of the 2D dimensionless Nernst-Planck equations for ion concentrations, the Poisson equation for the electric field and the Navier-Stokes equations for the fluid flow, and a stochastic growth rule for ion deposition. A new set of dimensionless numbers governing electroconvection dominated flows is introduced. Preliminary experimental measurements and numerical results indicate that in the electroconvection dominated regime coulombic forces increase with the applied voltage, and their influence over growth pattern formation can be assessed with the magnitude of the dimensionless electric Froude number. It is suggested that when this number decreases the deposit morphology changes from fractal to dense branching.

scholarly journals Fluid flow in the impulse valve of a hydraulic ram

2020 ◽  
Vol 3 (22) ◽  
Author(s):  
Wojciech Sobieski ◽  
Dariusz Grygo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Modeling ◽  
Hydrodynamic Pressure ◽  
Water Velocity ◽  
Experimental Measurements ◽  
Ansys Fluent ◽  
Working Cycle ◽  
Numerical Studies ◽  
Minimum Force

The paper presents the results of a study investigating the equilibrium of forces acting on the closing element of the impulse valve in a water ram at the end of the acceleration stage. Acceleration is one of the three main stages in the working cycle of a water ram. In the first part of the paper, we estimated water velocity based on our earlier experimental measurements. We also calculated the minimum force required for closing the impulse valve. The second part of the paper discusses two variants of a numerical model, which was developed in ANSYS Fluent to determine the result-ant hydrodynamic pressure and, consequently, the forces acting on the head of the impulse valve at the end of the acceleration stage. The main aim of this research was to verify the applicability of numerical modeling in water ram studies. The present study was motivated by the fact that Computational Fluid Dynamics is very rarely applied to water rams. In particular, we have not found any numerical studies related to the equilibrium of forces acting on the closing element of the impulse valve in a water ram.

Controls on submarine groundwater discharge in an urbanized bay of the southern Baltic Sea: An isotope and trace metal perspective.

2021 ◽  
Author(s):  
Catia Milene Ehlert von Ahn ◽  
Jan Scholten ◽  
Christoph Malik ◽  
Peter Feldens ◽  
Bo Liu ◽  
...  
Keyword(s):  
Coastal Waters ◽  
Water Samples ◽  
Coastal Aquifer ◽  
Submarine Groundwater Discharge ◽  
Surface Sediments ◽  
Groundwater Discharge ◽  
Water Interface ◽  
Mixing Zone ◽  
Submarine Groundwater ◽  
The Impact

<p>Submarine groundwater discharge (SGD) acts as a source of fresh water and dissolved substances for coastal ecosystems. Evaluation of the actual controls on SGD and corresponding chemical fluxes require a closer understanding of the processes that take place in the mixing zone between SGD and the coastal waters. It is hypothesized that artificial infrastructures, like sediment channeling, may ease the hydrological connection between coastal aquifer and coastal bottom water. The resultant, increase of SGD, changes the residence time in the mixing zone, and thereby, reduces the impact of early diagenesis. The present study focuses on the distribution of SGD, including the characterization of different mixing zones in the urbanized Wismar Bay (WB), southern Baltic Sea. Short sediment cores were retrieved for geochemical porewaters and sediment analyses. Surface sea water samples were collected along across-shore transects in the WB.  Besides major ions, Ba, Fe, and Mn, the water samples were analyzed for nutrients, dissolved inorganic carbon (DIC), stable isotopes (H, O, C, S), and Ra isotopes. Sediments were analyzed for C, N, S, Hg contents as well as reactive components (e.g. Fe, Mn, P) by HCl extractions. Organic matter mineralization rates, DIC, and SO<sub>4</sub> fluxes for the sediment-water interface were modeled from porewater profiles. Shallow seismic techniques were applied to identify potential litho-morphological controls on SGD. Geochemical porewater data allow identification of active SGD sites in the WB. In the central part, the freshening of porewaters in the top surface sediments indicates the upward flow of SGD originating from a coastal aquifer. The acoustic profiles show that the bottom sediments in the central bay are under local impact of excavation, reducing the sediment thickness above the coastal aquifer. Overall, the impact of SGD on the coastal water body of the WB is diffuse and promoted by local anthropogenic activity. The water isotope composition of porewaters at this site are close to the local meteoric water line at Warnemünde (located 50 km east of the WB), suggesting a discharge of relatively modern fresh waters. The (isotope) hydrochemical composition of the fresh water discharging is controlled by water-rock interactions in the aquifer and modulated by intense diagenesis in the brackish surface sediments. Furthermore, the SGD facilitates the upward migration of elements and enhances their fluxes across the sediment-water interface, e.g. DIC concentrations in the fresh groundwater are further enhanced in the mixing zone, indicating that SGD is a potential source of excess CO<sub>2</sub> in the investigated coastal waters.</p><p>The investigations are supported by the DAAD, DFG RTS Baltic TRANSCOAST, KiSnet project, BONUS SEAMOUNT, FP7 EU Marie Curie career integration grant, DAM-MFG, and IOW.</p>

Numerical modeling and experimental measurements of water spray impact and transport over a cylinder

2006 ◽  
Vol 32 (1) ◽  
pp. 132-157 ◽  
Author(s):  
S.S. Yoon ◽  
P.E. DesJardin ◽  
C. Presser ◽  
J.C. Hewson ◽  
C.T. Avedisian
Keyword(s):  
Numerical Modeling ◽  
Experimental Measurements ◽  
Water Spray

Experimental Measurements and Numerical Modeling Validation of Temperature Distribution in Tissue Medium During Short Pulse Laser Irradiation

2007 ◽  
Author(s):  
Ashim Dutta ◽  
Kyunghan Kim ◽  
Kunal Mitra ◽  
Zhixiong Guo
Keyword(s):  
Numerical Modeling ◽  
Heat Conduction ◽  
Temperature Distribution ◽  
Laser Beam ◽  
Pulse Laser ◽  
Short Pulse ◽  
Hyperbolic Heat Conduction ◽  
Experimental Measurements ◽  
Conduction Model ◽  
Short Pulse Laser

The objective of this paper is to analyze the temperature distributions and heat affected zone in skin tissue medium when irradiated with either a collimated or a focused laser beam from a short pulse laser source. Single-layer and three-layer tissue phantoms containing embedded inhomogeneities are used as a model of human skin tissue having subsurface tumor. Q-switched Nd:YAG laser is used in this study. Experimental measurements of axial and radial temperature distribution in the tissue phantom are compared with the numerical modeling results. For numerical modeling, the transient radiative transport equation is first solved using discrete ordinates method for obtaining the intensity distribution and radiative heat flux inside the tissue medium. Then the temperature distribution is obtained by coupling the bio-heat transfer equation with either hyperbolic non-Fourier or parabolic Fourier heat conduction model. The hyperbolic heat conduction equation is solved using MacCormack’s scheme with error terms correction. It is observed that experimentally measured temperature distribution is in good agreement with that predicted by hyperbolic heat conduction model. The experimental measurements also demonstrate that converging laser beam focused directly at the subsurface location can produce desired high temperature at that location as compared to that produced by collimated laser beam for the same laser parameters.

Terahertz Tomography of Low Contrast Objects: Algorithms and Experimental Measurements

2010 ◽  
Vol 5 (4) ◽  
pp. 91-97
Author(s):  
Valeriy V. Pickalov ◽  
Aleksandr L. Balandin ◽  
Dmitriy G. Rodionov ◽  
Maxim G. Vlasenko ◽  
Boris A. Knyazev
Keyword(s):  
Numerical Modeling ◽  
Iterative Algorithm ◽  
Experimental Methods ◽  
Experimental Measurements ◽  
Diffraction Tomography ◽  
Low Contrast ◽  
Type Algorithm ◽  
Thz Range

In this paper numerical modeling of tomography projections measurements is done and the iterative algorithm of diffraction tomography is developed for reconstruction of images of objects. Generalization of one of the most perspective algorithms of iterative type, – algorithm Gerchberg-Papoulis (G-P), from ray tomography to diffraction tomography, is evolved. Experimental methods of tomographical projections acquisition in a THz range are constructed

Flow dynamics and salt transport in a coastal aquifer driven by a stratified saltwater body: Lab experiment and numerical modeling

2014 ◽  
Vol 511 ◽  
pp. 665-674 ◽  
Author(s):  
Imri Oz ◽  
Eyal Shalev ◽  
Yoseph Yechieli ◽  
Ittai Gavrieli ◽  
Haim Gvirtzman
Keyword(s):  
Numerical Modeling ◽  
Coastal Aquifer ◽  
Flow Dynamics ◽  
Salt Transport ◽  
Lab Experiment
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