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    Column and batch study of haloacetic acids adsorption onto granular activated carbon

    , Article Research Journal of Chemistry and Environment ; Volume 15, Issue 2 , Jun , 2011 , Pages 866-872 ; 09720626 (ISSN) Tabatabaee, G. S. M ; Mousavi, S. M ; Soltanieh, M ; Seif, K. A. K ; Sharif University of Technology
    The granular activated carbon (GAC) was used as an adsorbent for its ability to remove haloacetic acids (HAAs) from drinking water by batch and column experiments. Various thermodynamic parameters, such as ΔG°, ΔH° and ΔS° have been calculated. The thermodynamics of HAAs onto GAC system indicates spontaneous and exothermic nature of the process. The ability of GAC to adsorb HAAs in a fixed bed column was investigated as well. The effect of operating parameters such as flow rate and inlet HAAs concentration on the sorption characteristics of GAC was investigated. The total adsorbed quantities, equilibrium uptakes and total removal percents of HAAs related to the effluent volumes were... 

    Analytical Solution for Isothermal Flow in a Shock Tube Containing Rigid Granular Material

    , Article Transport in Porous Media ; Volume 93, Issue 1 , 2012 , Pages 13-27 ; 01693913 (ISSN) Hayati, A. N ; Ahmadi, M. M ; Mohammadi, S ; Sharif University of Technology
    Analytical solution of shock wave propagation in pure gas in a shock tube is usually addressed in gas dynamics. However, such a solution for granular media is complex due to the inclusion of parameters relating to particles configuration within the medium, which affect the balance equations. In this article, an analytical solution for isothermal shock wave propagation in an isotropic homogenous rigid granular material is presented, and a closed-form solution is obtained for the case of weak shock waves. Fluid mass and momentum equations are first written in wave and (mathematical) non-conservation forms. Afterwards by redefining the sound speed of the gas flowing inside the pores, an... 

    A robust finite volume model to simulate granular flows

    , Article Computers and Geotechnics ; Volume 66 , May , 2015 , Pages 96-112 ; 0266352X (ISSN) Yavari Ramshe, S ; Ataie Ashtiani, B ; Sanders, B. F ; Sharif University of Technology
    Elsevier Ltd  2015
    This paper introduces a well-balanced second-order finite volume scheme, based on the Q-scheme of Roe, for simulating granular type flows. The proposed method is applied to solve the incompressible Euler equations under Savage-Hutter assumptions. The model is derived in a local coordinate system along a non-erodible bed to take its curvature into account. Moreover, simultaneous appearance of flowing/static regions is simulated by considering a basal friction resistance which keeps the granular flow from moving when the angle of granular flow is less than the angle of repose. The proposed scheme preserves stationary solutions up to second order and deals with different situations of wet/dry... 

    Sliding on wet sand

    , Article Granular Matter ; Volume 22, Issue 3 , May , 2020 Liefferink, R. W ; Aliasgari, M ; Maleki Jirsaraei, N ; Rouhani, S ; Bonn, D ; Sharif University of Technology
    Springer  2020
    We present sliding experiments of a sledge on wetted sand and describe that the frictional response is controlled by the penetration hardness of the granular medium. Adding a small amount of water to sand increases the hardness which results in a decrease of the sliding friction. Pouring even more water to sand results in a decrease of the hardness and a subsequent increase of the friction. This inverse correlation between hardness of a wetted granular material and its frictional response to sliding is found to be due to ploughing of the sledge. When the load of the sledge exceeds the penetration hardness of the water-sand mixture the granular material is irreversibly deformed, which is... 

    Development of a saturation-based μ(I)-rheology for wet granular materials using discrete element method

    , Article Scientia Iranica ; Volume 28, Issue 5 B , 2021 , Pages 2719-2732 ; 10263098 (ISSN) Ghorbani, R ; Taghizadeh Manzari, M ; Hajilouy Benisi, A ; Sharif University of Technology
    Sharif University of Technology  2021
    The present study employs Discrete Element Method (DEM) to establish a rheological model that relates the apparent viscosity of a granular material to shear rate, normal stress, and water saturation. In addition, a theoretical model was developed to determine water distribution and water-induced forces between particles for different saturations. The resulting forces were embedded in a 3D shear cell as a numerical rheometer, and a wet specimen was sheared between two walls. A power law rheological model was then obtained as a function of inertia number and saturation. It was found that up to a critical saturation, the apparent viscosity increased with saturation that was higher than that of... 

    Investigating the effect of mixing layer rheology on granular flow over entrainable beds using SPH method

    , Article Computers and Geosciences ; Volume 155 , 2021 ; 00983004 (ISSN) Nikooei, M ; Manzari, M. T ; Sharif University of Technology
    Elsevier Ltd  2021
    This paper numerically studies the interaction of a flowing granular material with an entrainable granular bed, while materials are mixed at the interface of two materials. The rheological behavior of this granular mixture is characterized by a generalized viscoplastic model that includes local volume fraction of materials as well as their physical properties, i.e. size, density, and friction angle. Additionally, the effect of the dynamics of entrained bed-type particles on the rheology of the granular mixture is considered. The governing equations of the flow are discretized using the Incompressible Smoothed Particle Hydrodynamics (SPH) method in which mixing of particles can be... 

    Pore scale study of permeability and tortuosity for flow through particulate media using Lattice Boltzmann method

    , Article International Journal for Numerical and Analytical Methods in Geomechanics ; Volume 35, Issue 8 , 2011 , Pages 886-901 ; 03639061 (ISSN) Ghassemi, A ; Pak, A ; Sharif University of Technology
    In this paper, Lattice Boltzmann method (LBM) has been used to study the effects of permeability and tortuosity on flow through saturated particulate media and identify the relationships between permeability and tortuosity with other parameters such as particles diameter, grain specific surface, and porosity. LBM is a simple kinematic model that can incorporate the essential physics of microscopic and mesoscopic processes involved in flow through granular soils. The obtained results indicate that the 2D LB model, due to its inherent theoretical advantages, is capable of demonstrating that the porosity and specific surface are the most influential parameters in determining the intrinsic... 

    Numerical study of the coupled hydro-mechanical effects in dynamic compaction of saturated granular soils

    , Article Computers and Geotechnics ; Volume 37, Issue 1-2 , 2010 , Pages 10-24 ; 0266352X (ISSN) Ghassemi, A ; Pak, A ; Shahir, H ; Sharif University of Technology
    Dynamic compaction is a widely used method for improvement of loose granular deposits. Its applicability in saturated layers generally considered to be less effective because of the fact that part of the applied energy is absorbed by pore water. Up to now the majority of numerical simulations have focused on the analysis of dynamic compaction in dry/moist soils. In this paper, a fully coupled hydro-mechanical finite element code has been developed and employed to evaluate the dynamic compaction effects on saturated granular soils. After verification of the results by comparing the numerical results with those measured in a real field case of DC treatment in a highway, some sensitivity... 

    Effect of stress direction on the cyclic resistance of sand

    , Article Proceedings of the Institution of Civil Engineers: Geotechnical Engineering ; Volume 171, Issue 2 , April , 2018 , Pages 109-120 ; 13532618 (ISSN) Jafarzadeh, F ; Zamanian, M ; Sharif University of Technology
    ICE Publishing  2018
    In total, 55 undrained cyclic torsional shear tests were conducted at a constant mean confining stress, σ0m, constant intermediate principal stress ratios, b = (σ2 − σ3)/(σ1 − σ3), and principal stress directions, α. The cyclic resistance of loose, isotropically consolidated specimens exhibited a dip in strength, with the lowest values for α being 45°, an angle at which α was oriented such that the potential shear band directions dovetailed with the plane having the weakest strength (i.e. horizontal plane). For a given α, the cyclic resistance decreased to the lowest values for b = 0·5, at which the value of the principal stresses was different in the three major directions. For dense... 

    A numerical tool for design of dynamic compaction treatment in dry and moist sands

    , Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 33, Issue 4 , 2009 , Pages 313-326 ; 10286284 (ISSN) Ghassemi, A ; Pak, A ; Shahir, H ; Sharif University of Technology
    Dynamic compaction (DC) is a popular soil improvement method that is extensively used worldwide. DC treatment design is usually carried out based on past experiences and empirical relations. To establish a rational design approach, all important factors affecting the DC process should be taken into account. In this paper, a finite element code is developed for modeling the impact behavior of dry and moist granular soils. The code is verified with the results of some centrifuge tests. Several analyses were conducted in order to study the effects of energy/momentum per drop, tamper base radius, and number of drops on compaction degree, compacted depth, and extension of the improved zone in the... 

    Discrete element model (DEM) simulations of cone penetration test (CPT) measurements and soil classification

    , Article Canadian Geotechnical Journal ; Volume 57, Issue 9 , November , 2020 , Pages 1369-1387 Khosravi, A ; Martinez, A ; Dejong, J. T ; Sharif University of Technology
    Canadian Science Publishing  2020
    This paper presents a study on the simulation of cone penetration tests (CPTs) using the discrete element model (DEM) method. This study’s main objective is to investigate the effect of different modeling parameters and simulation configurations on the ability of three-dimensional DEM simulations to replicate realistic CPT tip resistance (qc) and friction sleeve shear stress (fs) measurements. The CPT tests were simulated in virtual calibration chambers (VCCs) containing particles calibrated to model the behavior of sand. The parameters investigated included the granular assembly properties, interparticle contact parameters, particle–probe interface characteristics, and simulation... 

    Studying effect of entrainment on dynamics of debris flows using numerical simulation

    , Article Computers and Geosciences ; Volume 134 , 2020 Nikooei, M ; Manzari, M. T ; Sharif University of Technology
    Elsevier Ltd  2020
    This paper studies entrainment phenomenon in debris flows using full flow (non-depth-averaged) equations and an Incompressible Smoothed Particle Hydrodynamics (ISPH) method. A viscoplastic constitutive relationship is adopted for both the overlying fluid and bed material. Collapse of a two-dimensional dry granular column on a horizontal bed consisting of entrainable dry granular material is considered as a benchmark problem. The adopted ISPH method for simulation of collapse over rigid and entrainable beds is validated using available numerical and experimental data. To quantify the effects of entrainment on dynamics of flow, the initial aspect ratio of granular column (a) is varied and the... 

    An enhanced neural network model for predictive control of granule quality characteristics

    , Article Scientia Iranica ; Volume 18, Issue 3 E , 2011 , Pages 722-730 ; 10263098 (ISSN) Neshat, N ; Mahloojifl, H ; Kazemi, A ; Sharif University of Technology
    An integrated approach is presented for predicting granule particle size using Partial Correlation (PC) analysis and Artificial Neural Networks (ANNs). In this approach, the proposed model is an abstract form from the ANN model, which intends to reduce model complexity via reducing the dimension of the input set and consequently improving the generalization capability of the model. This study involves comparing the capability of the proposed model in predicting granule particle size with those obtained from ANN and Multi Linear Regression models, with respect to some indicators. The numerical results confirm the superiority of the proposed model over the others in the prediction of granule...