The Poisoning Effect of Sulfur-Containing Compounds on the Elelctro-Oxidation of Methanol and Ethanol on Ni and Cu Electrodes

, M.Sc. Thesis Sharif University of Technology Valadbeigi, Younes (Author) ; Gobal, Fereydon (Supervisor)

Abstract

In this study a systematic effort was made to investigate the poisoning effect of sulfur-containing materials on the electro- oxidation of methanol and ethanol on Ni and Cu electrodes in alkaline solutions by the methods of cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Activation energy of methanol electro-oxidation in the absence of Na2S was obtained 30.7 kJ/mol by cyclic voltammetric at different temperatures, and its values increased by increase in Na2S concentrations to 97kJ/mol. Na2S adsorption isotherms corresponded with Langmuire isotherm, equilibrium constants of adsorption – desorption and adsorption enthalpy (ΔHads= -62kJ/mol) were calculated for...

Effect of distance-dependent dispersivity on density-driven flow in porous media

, Article Journal of Hydrology ; Volume 589 , October , 2020 Younes, A ; Fahs, M ; Ataie Ashtiani, B ; Simmons, C. T ; Sharif University of Technology

Elsevier B.V 2020

Abstract

In this study, the effect of distance-dependent dispersion coefficients on density-driven flow is investigated. The linear asymptotic model, which assumes that dispersivities increase linearly with distance from the source of contamination and reach asymptotic values at a large asymptotic distance, is employed. An in-house numerical model is adapted to handle distance-dependent dispersion. The effect of asymptotic-dispersion on aquifer contamination is analyzed for two tests: (i) a seawater intrusion problem in a coastal aquifer and (ii) a leachate transport problem from a surface deposit site. Global Sensitivity Analysis (GSA) combined with the Polynomial Chaos Expansion (PCE) surrogate...

The henry problem: New semianalytical solution for velocity-dependent dispersion

, Article Water Resources Research ; Volume 52, Issue 9 , 2016 , Pages 7382-7407 ; 00431397 (ISSN) Fahs, M ; Ataie Ashtiani, B ; Younes, A ; Simmons, C. T ; Ackerer, P ; Sharif University of Technology

Blackwell Publishing Ltd 2016

Abstract

A new semianalytical solution is developed for the velocity-dependent dispersion Henry problem using the Fourier-Galerkin method (FG). The integral arising from the velocity-dependent dispersion term is evaluated numerically using an accurate technique based on an adaptive scheme. Numerical integration and nonlinear dependence of the dispersion on the velocity render the semianalytical solution impractical. To alleviate this issue and to obtain the solution at affordable computational cost, a robust implementation for solving the nonlinear system arising from the FG method is developed. It allows for reducing the number of attempts of the iterative procedure and the computational cost by...

Semianalytical solutions for contaminant transport under variable velocity field in a coastal aquifer

, Article Journal of Hydrology ; Volume 560 , 2018 , Pages 434-450 ; 00221694 (ISSN) Koohbor, B ; Fahs, M ; Ataie Ashtiani, B ; Simmons, C. T ; Younes, A ; Sharif University of Technology

Elsevier B.V 2018

Abstract

Existing closed-form solutions of contaminant transport problems are limited by the mathematically convenient assumption of uniform flow. These solutions cannot be used to investigate contaminant transport in coastal aquifers where seawater intrusion induces a variable velocity field. An adaptation of the Fourier-Galerkin method is introduced to obtain semi-analytical solutions for contaminant transport in a confined coastal aquifer in which the saltwater wedge is in equilibrium with a freshwater discharge flow. Two scenarios dealing with contaminant leakage from the aquifer top surface and contaminant migration from a source at the landward boundary are considered. Robust implementation of...

On the use of COMSOL Multiphysics for seawater intrusion in fractured coastal aquifers

, Article 25th Salt Water Intrusion Meeting, SWIM 2018, 17 June 2018 through 22 June 2018 ; Volume 54 , 2018 ; 22671242 (ISSN) Mozafari, B ; Fahs, M ; Ataie Ashtiani, B ; Simmons, C. T ; Younes, R ; Sharif University of Technology

EDP Sciences 2018

Abstract

COMSOL Multiphysics is a comprehensive simulation software environment for a wide range of applications. COMSOL has an interactive interface that facilitates the modeling procedure and allows an easy coupling of different physical processes. The Subsurface Flow module extends the COMSOL modeling environment to applications related to fluid flow in saturated and variably saturated porous media. COMSOL is increasingly used in the investigation of geophysical, hydrogeological and environmental phenomena. The main goal of this work is to explore the ability of COMSOL for simulating seawater intrusion (SWI) in fractured coastal aquifers. Numerical modeling of such a problem is of high interest as...

Convective-reactive transport of dissolved CO2 in fractured-geological formations

, Article International Journal of Greenhouse Gas Control ; Volume 109 , 2021 ; 17505836 (ISSN) Shafabakhsh, P ; Ataie Ashtiani, B ; Simmons, C. T ; Younes, A ; Fahs, M ; Sharif University of Technology

Elsevier Ltd 2021

Abstract

Carbon dioxide (CO2) storage in geologic formations is an attractive means of reducing greenhouse gas emissions. The main processes controlling the migration of CO2 in geological formations are related to convective mixing and geochemical reactions. The effects of heterogeneity on these coupled processes have been widely discussed in the literature. Recently, special attention has been devoted to fractured geological formations that can be found in several storage reservoirs. However, existing studies on the effect of fractures on the fate of CO2 neglect the key processes of geochemical reactions. This work aims at addressing this gap. Based on numerical simulations of a hypothetical...

Uncertainty analysis for seawater intrusion in fractured coastal aquifers: Effects of fracture location, aperture, density and hydrodynamic parameters

, Article Journal of Hydrology ; Volume 571 , 2019 , Pages 159-177 ; 00221694 (ISSN) Koohbor, B ; Fahs, M ; Ataie Ashtiani, B ; Belfort, B ; Simmons, C. T ; Younes, A ; Sharif University of Technology

Elsevier B.V 2019

Abstract

In this study we use polynomial chaos expansion (PCE) to perform uncertainty analysis for seawater intrusion (SWI) in fractured coastal aquifers (FCAs) which is simulated using the coupled discrete fracture network (DFN) and variable-density flow (VDF) models. The DFN-VDF model requires detailed discontinuous analysis of the fractures. In real field applications, these characteristics are usually uncertain which may have a major effect on the predictive capability of the model. Thus, we perform global sensitivity analysis (GSA) to provide a preliminary assessment on how these uncertainties can affect the model outputs. As our conceptual model, we consider fractured configurations of the...

Study of the effect of thermal dispersion on internal natural convection in porous media using fourier series

, Article Transport in Porous Media ; Volume 131, Issue 2 , 2020 , Pages 537-568 Fahs, M ; Graf, T ; Tran, T. V ; Ataie Ashtiani, B ; Simmons, C. T ; Younes, A ; Sharif University of Technology

Springer 2020

Abstract

Natural convection in a porous enclosure in the presence of thermal dispersion is investigated. The Fourier–Galerkin (FG) spectral element method is adapted to solve the coupled equations of Darcy’s flow and heat transfer with a full velocity-dependent dispersion tensor, employing the stream function formulation. A sound implementation of the FG method is developed to obtain accurate solutions within affordable computational costs. In the spectral space, the stream function is expressed analytically in terms of temperature, and the spectral system is solved using temperature as the primary unknown. The FG method is compared to finite element solutions obtained using an in-house code...

Editorial: Modeling-Based approaches for water resources problems

, Article Frontiers in Water ; Volume 4 , 2022 ; 26249375 (ISSN) Fahs, M ; Ataie Ashtiani, B ; Graf, T ; Saaltink, M. W ; Simmons, C. T ; Younes, A ; Sharif University of Technology

Frontiers Media S.A 2022

A generalized semi-analytical solution for the dispersive henry problem: effect of stratification and anisotropy on seawater intrusion

, Article Water (Switzerland) ; Volume 10, Issue 2 , 2018 ; 20734441 (ISSN) Fahs, M ; Koohbor, B ; Belfort, B ; Ataie Ashtiani, B ; Simmons, C. T ; Younes, A ; Ackerer, P ; Sharif University of Technology

MDPI AG 2018

Abstract

The Henry problem (HP) continues to play a useful role in theoretical and practical studies related to seawater intrusion (SWI) into coastal aquifers. The popularity of this problem is attributed to its simplicity and precision to the existence of semi-analytical (SA) solutions. The first SA solution has been developed for a high uniform diffusion coefficient. Several further studies have contributed more realistic solutions with lower diffusion coefficients or velocity-dependent dispersion. All the existing SA solutions are limited to homogenous and isotropic domains. This work attempts to improve the realism of the SA solution of the dispersive HP by extending it to heterogeneous and...

Welcome message from the P2MNET chairs

, Article Proceedings - Conference on Local Computer Networks, LCN ; Article number 6761228 , 21-24 October , 2013 , pp. lv-lvi ; ISBN: 9781479905379 Boukerche, A ; Loucif, S ; Mammeri, A ; Ababneh, N ; Araujo, R ; De Grande, R ; Delicato, F ; Fouchal, H ; Juiz, C ; Pagna Disso, J. F ; Pereira, R ; Pires, P ; Rezende, C ; Sarbazi-Azad, H ; Si, W ; Takai, M ; Younes, M. B ; Xie, H ; Sharif University of Technology

2013

Abstract

[No abstract available]

Welcome message from the P2MNET chairs

, Article Proceedings - Conference on Local Computer Networks, LCN ; October , 2013 , Pages lv-lvi ; 9781479905379 (ISBN) Boukerche, A ; Loucif, S ; Mammeri, A ; Ababneh, N ; Araujo, R ; De Grande, R ; Delicato, F ; Fouchal, H ; Juiz, C ; Pagna Disso, J. F ; Pereira, R ; Pires, P ; Rezende, C ; Sarbazi Azad, H ; Si, W ; Takai, M ; Younes, M. B ; Xie, H ; Sharif University of Technology

IEEE Computer Society 2013