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Comparison of different turbulence models in predicting cohesive fluid mud gravity current propagation

International Journal of Sediment Research 2020年第5期35卷 504-515页

作者： Seyed-Mohammad-Kazem Emami Sayed-Farhad Mousavi Khosrow Hosseini Hesam Fouladfar majid mohammadian Faculty of Civil Engineering University of Semnan Iran Water & Power Resources Development Company 3. Department of Civil Engineering University of Ottawa

A numerical study of propagation of cohesive fluid mud gravity currents in the form of lock-exchange was done using the OpenFOAM open source *** Eulerian approach solution for three separate phases was developed by incorporating a rheological model to predict the front position of cohesive fluid mud gravity *** model also simulates features in the complete movement phases including slumping,self-similar,and viscous in which the dynamics of propagation are affected by the balance of viscous and buoyancy forces,and the inertia force is *** influence of using different turbulence models containing sub-grid scale(SGS),modified SGS,detached eddy simulation(DES),delayeddetached eddy simulation(DDES),Launder-R eece-Rodi(LRR),and k-ε models on the accuracy of simulation results was evaluated by comparing with available experimental *** results show that the selection of the proper turbulence model is one of the most important issues for this type of the numerical *** more efficient turbulence model was suggested and tabulated for each stage of propagation and different selected concentrations of 1,045,1,140,and 1,214 g/*** different turbulence models(except k-ε) lead to front propagation dynamic simulation results that are in good agreement with the experimental measurements in the early stage of propagation for low concentrations,only DES,SGS,and modified SGS are able to capture the Kelvin-Helmholtz instability vortex shapes at the dense fluid interface,which is the main characteristic of the gravity current through the slumping *** calculated accuracies of SGS and modified SGS in predicting gravity current propagation for the both self-similar and viscous phases also are slightly better than DES,DDES,and LRR model *** results of this study confirmed the performance and efficiency of the modified SGS model in which the interaction coefficients between phases are calibrated for the numerical modeling of fluid mud

关键词： Gravity current Turbulence model Numerical simulation Cohesive particles Rheology

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Numerical Simulation of Van der Waals Fluids

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材料科学与工程（中英文A版） 2011年第3X期1卷 444-450页

作者： A. majid mohammadian A. Vahid mohammadian Department of Civil Engineering University of Ottawa 161 Louis Pasteur Ottawa Ontario KI N6N5 Canada Department of Mechanical Engineering Chabahar Maritime University Iran

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On Dissipation and Dispersion Errors Optimization,A-Stability and SSP Properties

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Communications in Computational Physics 2018年第6期24卷 268-285页

作者： Arman Rokhzadi Abdolmajid mohammadian Department of Civil Engineering University of Ottawa161 Louis PasteurOttawaONCanada

In a recent paper(Du and Ekaterinaris,2016)optimization of dissipation and dispersion errors was investigated.A Diagonally Implicit Runge-Kutta(DIRK)scheme was developed by using the relative stability concept,*** ratio of absolute numerical stability function to analytical *** indicated that their new scheme has many similarities to one of the optimized Strong Stability Preserving(SSP)*** concluded that,for steady state simulations,time integration schemes should have high dissipation and low *** this note,dissipation and dispersion errors for DIRK schemes are studied *** is shown that relative stability is not an appropriate criterion for numerical stability ***,within absolute stability analysis,it is shown that there are two important concerns,accuracy and stability *** is proved that both A-stability and SSP properties aim at minimizing the dissipation and dispersion *** A-stability property attempts to increase the stability limit for large time step sizes and by bounding the error propagations via minimizing the numerical dispersion relation,SSP optimized method aims at increasing the accuracy limits by minimizing the difference between analytical and numerical dispersion ***,it can be concluded that A-stability property is necessary for calculations under large time-step sizes and,more specifically,for calculation of high diffusion ***,it is shown that the oscillatory behavior,reported by Du and Ekaterinaris(2016),is due to Newton method and the tolerances they set and it is not related to the employed temporal schemes.

关键词： Diagonally Implicit Runge-Kutta methods dissipation and dispersion optimization numerical stability steady state

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Reservoir heterogeneity and fracture parameter determination using electrical image logs and petrophysical data(a case study, carbonate Asmari Formation, Zagros Basin, SW Iran)

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Petroleum Science 2020年第1期17卷 51-69页

作者： Ghasem Aghli Reza Moussavi-Harami Ruhangiz mohammadian National Iranian South Oil Company(NISOC) AhvazIran Department of Geology Ferdowsi University of MashhadMashhadIran

Assessment of reservoir and fracture parameters is necessary to optimize oil production,especially in heterogeneous *** and image logs are regarded as two of the best methods for this ***,due to core limitations,using image log is considered as the best *** study aims to use electrical image logs in the carbonate Asmari Formation reservoir in Zagros Basin,SW Iran,in order to evaluate natural fractures,porosity system,permeability profile and heterogeneity index and accordingly compare the results with core and well *** results indicated that the electrical image logs are reliable for evaluating fracture and reservoir parameters,when there is no core available for a *** on the results from formation micro-imager(FMI)and electrical micro-imager(EMI),Asmari was recognized as a completely fractured reservoir in studied field and the reservoir parameters are mainly controlled by ***,core and image logs indicated that the secondary porosity varies from 0%to 10%.The permeability indicator indicates that zones 3 and 5 have higher permeability *** log permeability index shows a very reasonable permeability profile after scaling against core and modular dynamics tester mobility,mud loss and production index which vary between 1 and 1000 *** addition,no relationship was observed between core porosity and permeability,while the permeability relied heavily on fracture ***,fracture aperture was considered as the most important parameter for the determination of *** changes were also observed at zones 1-1 and 5 in the permeability trend,due to the high fracture *** can be concluded that the electrical image logs(FMI and EMI)are usable for evaluating both reservoir and fracture parameters in wells with no core data in the Zagros Basin,SW Iran.

关键词： FMI and EMI image logs Porosity and permeability Fractures Core data Heterogeneity index

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Numerical modeling of local scour at a submerged weir with a downstream slope using a coupled moving-mesh and maskedelement approach

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International Journal of Sediment Research 2021年第2期36卷 279-290页

作者： Xiaohui Yan Colin David Rennie Abdolmajid mohammadian Department of Civil Engineering University of Ottawa

This paper presents a model for local scour at submerged weirs with downstream slopes that uses a coupled moving-mesh and masked-element approach. In the developed model, the fluid-sediment interface is tracked using a moving-mesh technique, and the effects of the structure on the hydrodynamics and bed morphology are resolved using a masked-element technique. Compared to traditional sediment scour models, based on the moving-mesh technique, the present model has the advantage of allowing for a simpler setup of the computational grids and a larger-amplitude deformation. Laboratory experiments on local scour at a submerged weir with a downstream slope were conducted, which provided bed profiles at different time instants. The results obtained by the present model are compared to the experimental data. The comparisons demonstrate the performance of the model in satisfactorily predicting local scour at a submerged weir with a downstream slope. The model was further modified and employed to carry out additional computations to investigate the influence of various parameters and sub-models.

关键词： Numerical modeling Bed morphology Submerged weir Downstream slope Moving-mesh and masked-element OpenFOAM

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Hydrodynamic Assessment of A New Nature-Based Armour Unit on Rubble Mound Breakwater for Coastal Protection

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China Ocean Engineering 2024年第3期38卷 439-452页

作者： Ehsan SAFA Alireza MOJTAHEDI Abdolmajid mohammadian Mohamad Ali Lotfollahi YAGHIN Department of Water Resources Engineering Faculty of Civil EngineeringUniversity of TabrizTabriz ***Iran Faculty of Civil Engineering University of OttawaOttawa K1H 8M5Canada

This research proposes a novel nature-based design of a new concrete armour unit for the cover layer of a rubblemoundbreakwater. Armour units are versatile with respect to shape, orientation, surface condition details, and ***, a detailed analysis is required to investigate the exact state of their hydraulic interactions and structuralresponses. In this regard, the performance results of several traditional armour units, including the Antifer cube,Tetrapod, X-block and natural stone, are considered for the first step of this study. Then, the related observed resultsare compared with those obtained for a newly designed (artificial coral) armour unit. The research methodology utilizesthe common wave flume test procedure. Furthermore, several verified numerical models in OpenFOAM code areused to gain the extra required data. The proposed armour is configured to provide an effective shore protection as anenvironmental-friendly coastal structure. Thus it is designed with a main trunk including deep grooves to imitate thetypical geometry of a coral type configuration, so as to attain desirable performance. The observed results and ananalytic hierarchy process (AHP) concept are used to compare the hydraulic performance of the studied traditionaland newly proposed (artificial coral) armour units. The results indicate that the artificial coral armour unit demonstratesacceptable performance. The widely used traditional armour units might be replaced by newer designs for betterwave energy dissipation, and more importantly, for fewer adverse effects on the marine environment.

关键词： rubble mound breakwater hydraulic interaction armour unit analytic hierarchy process numerical model

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Immobilization of organophosphorus hydrolase enzyme by covalent attachment on modified cellulose microfibers using different chemical activation strategies:Characterization and stability studies

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Chinese Journal of Chemical Engineering 2019年第1期27卷 191-199页

作者： Meisam Sharifi Seyed-Mortaza Robatjazi Minoo Sadri Jafar mohammadian Mosaabadi Department of Bioscience and Biotechnology Malek Ashtar University of Technology

The plant cellulose powder was activated by two different methods using 1,4-butanediol diglycidyl ether(BTDE)and 1,1′-Carbonyldiimidazole(CDI) as the chemical coupling *** hydrolase(OPH) from Flavobacterium ATCC 27551 was immobilized on any of activated support through covalent *** optimal conditions of affecting parameters on enzyme immobilization in both methods were found, and it was demonstrated that the highest activity yields of immobilized OPH onto epoxy and CDI treated cellulose were 68.32%and 73.51%, *** surface treatment of cellulose via covalent coupling with BTDE and CDI agents was proved by FTIR *** kinetic constants of the free and immobilized enzymes were determined, and it was showed that both immobilization techniques moderately increased the Kmvalue of the free *** improvements in storage and thermal stability were investigated and depicted that the half-life of immobilized OPH over the surface of epoxy modified cellulose had a better growth compared to the free and immobilized enzymes onto CDI treated ***, the pH stability of the immobilized preparations was enhanced relative to the free counterpart and revealed that all enzyme samples would have the same optimum pH value for stability at ***, the immobilized OPH onto epoxy and CDI activated cellulose retained about 59% and 68% of their initial activity after ten turns of batch operation, *** results demonstrated the high performance of OPH enzyme in immobilized state onto an inexpensive support with the potential of industrial applications.

关键词： Organophosphorus hydrolase Cellulose powder Activation Immobilization Stability

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Numerical modeling of local scour due to submerged wall jets using a strict vertex-based,terrain conformal,moving-mesh technique in OpenFOAM

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International Journal of Sediment Research 2020年第3期35卷 237-248页

作者： Xiaohui Yan Abdolmajid mohammadian Colin D.Rennie Department of Civil Engineering University of Ottawa

This study presents the implementation and validation of a new sediment-scour model with a strict vertex-based,terrain conformal,moving-mesh technique within the framework of *** lacks the ability to simulate large-amplitude motion needed for analysis of sediment-scour problems,and,thus,its application normally is restricted to small-amplitude cases to prevent computational divergence due to mesh *** proposed simple,moving-mesh technique in OpenFOAM is implemented to overcome the shortcomings of the conventional automatic mesh-motion techniques in handling large-amplitude moving *** model is used to simulate a simple case of prescribed boundary motion,a previous experiment in the literature,and a new laboratory experiment for local scour due to submerged wall *** results are compared with both the experimental and other numerical *** comparisons demonstrate that the proposed model has the novel advantage of allowing for more severe topographic variations,and can provide more reliable predictions for the key characteristics and evolution of the bed profiles in wall jet scour ***,to improve the practice of modeling wall jet scour,various turbulence modeling approaches and bedload equations also are evaluated and compared.

关键词： Numerical modeling Sediment scour Submerged wall jets Moving mesh OpenFOAM Bed evolution

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Benzene selective hydrogenation over supported Ni(nano-) particles catalysts: Catalytic and kinetics studies

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Chinese Journal of Chemical Engineering 2018年第3期26卷 521-528页

作者： M.H.Peyrovi N.Parsafard Z.mohammadian Faculty of Chemistry Science and Petroleum Department of Physical Chemistry University of Shahid Beheshti Kosar University of Bojnord Department of Applied Chemistry

This report aims to reduce the benzene in a mixture of benzene and toluene as a model reaction using catalytic hydrogenation. In this research, we developed a series of catalysts with different supports such as Ni/HMS, Ni/HZSM-5, Ni/HZSM5-HMS, Ni/Al2O3 and Ni/SiO2. Kinetic of this reaction was investigated under various hydrogen and benzene pressures. For more study, two kinetic models have also been selected and tested to describe the kinetics for this reaction. Both used models, the power law and Langmuir-Hinshelwood, provided a good fit toward the experimental data and allowed to determine the kinetic parameters. Among these catalysts, Ni/Al2O3 showed the maximum benzene conversion （99.19%） at 130℃ for benzene hydrogenation. The lowest toluene conversion was observed for Ni/SiO2. Furthermore, this catalyst presented high selectivity to benzene （75.26%） at 130℃. The catalytic performance （activity, selectivity and stability） and kinetics evaluations were shown that the Ni/SiO2 is an effective catalyst to hydrogenate benzene. It seems that the surface properties particularly pore size are effective parameter compared to other factors such as acidity and metal dispersion in this process.

关键词： Catalytic hydrogenation Power law model Langmuir-Hinshelwood mode Selectivity Kinetics

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TWO DIMENSIONAL NUMERICAL SIMULATION OF FLOW AND GEO-MORPHOLOGICAL PROCESSES NEAR HEADLANDS BY USING UNSTRUCTURED GRID

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International Journal of Sediment Research 2004年第4期19卷 258-277页

作者： A.mohammadian,M.TAJRISHI,F.LOTFIAZAD Dept.ofCivil Engineering Sharif University of Technology Tehran Iran Ph.D.Candidate Assistant Professor Dept. of Civil Engineering Sharif University of Technology Tehran Iran Research Associate Dept. of Comput. Hydr. Water Research Center Tehran Iran

A two-dimensional mathematical model for simulating flow and sediment transport is presented. The model simulates flow and geo-morphological processes using a high order accurate, oscillation free scheme. The depth averaged Reynolds (shallow water) equations are used for flow simulation. Both equilibrium and non-equilibrium methods (by solving convection-diffusion equation) are used for sediment transport modeling while sediment carrying capacity is computed using different methods. A finite volume, flux difference splitting scheme is employed to solve the governing equations, which is able to simulate sub, super and transcritical flows with shock waves. Moreover, the numerical method is able to simulate flow over the variable topographies and it has a low level of numerical diffusion in the case of circulating flows like headlands. The computational grid of this model is triangular unstructured with variable size, which is flexible for arbitrary geometries and grid refinement. Using the model for simulating flow and sediment transport in some test cases such as a partially closed channel and comparing the results showed that the results obtained by the developed model were in a reasonable agreement with measurements and the other models cited.

关键词： Flow Geo-morphological processes Shallow water Unstructured grid

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