Search for: numerical-investigations
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    Numerical Investigation of Two-Phase Flow Contains Water and Oil in Hydrocyclones

    , M.Sc. Thesis Sharif University of Technology Asadi, Mohammad (Author) ; Farhanieh, Bijan (Supervisor)
    Having an efficient and reliable system for oil-water separation is of crucial importance in oil and gas industry. Hydrocyclones have been used for more than a century to separate oil from water as well as sand from liquid or gas. The main objectives of this research are as follows: Determination the hydrocyclone principle of operation, based on computational fluid dynamic simulations. Hydrocyclones, in a spite of simple structure, are widely used in industry such as Petrochemical, Mining, Chemical Industries, Pharmacy, Food and Pulp Industries. The CALC BFC is one phase flow numerical code based on finite volume method and SIMPLEC algorithm. It was extended for simulating the two phase flow... 

    Numerical Investigation of Interaction Noise Using Rod-Airfoil Model

    , M.Sc. Thesis Sharif University of Technology Hashemi Rabori, Zari (Author) ; Farshchi, Mohammad (Supervisor) ; Tayyebi Rahni, Mohammad (Supervisor)
    In this thesis the interaction noise created by fluid flow with low Mach number over a rod-airfoil model simulated. Some numerical and experimental benchmark data for comparison and validation of results exist in articles. The simulation done by using Fluent 6.3 which restricts the choice of turbulence models to only 2D URANS. A study was undertaken on the cylinder as case study where some experimental aerodynamic and acoustic data are available. In this case study, the best turbulence model, discretization scheme and grid sizing were investigated. The only turbulence model which has the ability to simulate the near field and far field with a relatively good degree of accuracy was K-ω SST... 

    Experimental and numerical studies on resistance of a catamaran vessel with non-parallel demihulls

    , Article Scientia Iranica ; Vol. 21, Issue. 3 , 2014 , pp. 600-608 ; ISSN: 2345-3605 Ebrahimi, A ; Rad, M ; Hajilouy, A ; Sharif University of Technology
    In common catamaran vessels, demihulls are parallel to each other. In this paper, the total resistance of a catamaran vessel with non-parallel demihulls is investigated experimentally and numerically. Experiments are carried out at different Separation Ratios (S.R.), that is the ratio of fore to aft separation of the catamaran demihullsand also in two ratios of length to separation in amidships (L/Sm). The FLUENT solver, based on the Finite Volume Method (FVM), was used for numerical solution. Applying the VOF model, the free surface around the catamaran vessel and total resistance are calculated and compared with experimental results. Finally, the frictional resistance of the catamaran from... 

    A Numerical Study of Train-induced Vibration and the Screening Effectiveness of Shredded-tire-Infilled Trenches

    , M.Sc. Thesis Sharif University of Technology Koocheki, Kianoosh (Author) ; Ahmadi, Mohammad Mahdi (Supervisor)
    Train-induced vibrations can disturb the residential areas close to the rail as well as making ground-borne noises that can create problems for sensitive apparatus and devices. To reduce these problems, there need to be an evaluation of the amplitude of the ground-borne vibrations. The goal in this study is creating a suitable finite difference model in order to predict the intensity of train induced vibrations propagating inside or on the surface of the soil using FLAC (Fast Lagrangian Analysis of Continua) software as well as assessing the effectiveness of recycled shredded tires in reducing the surface vibrations by using these material as the filler for vibration isolation trenches. The... 

    A numerical investigation to study effects of a savonius rotor's plate shape on its optimum overlap ratio

    , Article ASME 2012 Gas Turbine India Conference, GTINDIA 2012, 1 December 2012 through 1 December 2012 ; December , 2012 , Pages 253-258 ; 9780791845165 (ISBN) Abbaszadeh, M ; Bagherzadeh, F ; Iravani, M ; Sharif University of Technology
    Present study is aimed to investigate the relationship between blade shape of Savonius rotor and its optimum overlap, an important parameter that can improve the rotor's performance superbly. To set a relation between rotor's shape and its overlap, a new parameter called "trailing angle" was introduced in this study and by a novel design method, several models were designed to represent a wide range of trailing angles. The investigation has been carried out by using Reynolds Stress Method (RSM) through ANSYS Fluent commercial software package. The application of the method was validated by comparing the results of a conventional model with experimental data acquired from one of the... 

    A Numerical Study of Bearing Capacity Factors for Shallow Foundations

    , M.Sc. Thesis Sharif University of Technology Sharifian, Hadi (Author) ; Ahmadi, Mohammad Mehdi (Supervisor)
    Determination of ultimate bearing capacity of shallow foundations has been discussed since long time ago in many books and papers. Although this is not generally a new problem, there are still some problems which may be interesting to be investigated in detail using suitable computer programs and by application of appropriate soil models. Comprehensive surveys on bearing capacity coefficients of different foundations have been done by utilizing FLAC software. The failure of soil is governed by the Elasto-Plastic Mohr-coulomb criterion. New graphs and equations have been developed for determining the coefficients. The equations achieved in this study by numerical methods, have been compared... 

    A Retrospective Trust-Region Method for Unconstrained Optimiation

    , M.Sc. Thesis Sharif University of Technology Zehtabian, Shohre (Author) ; Mahdavi-Amiri, Nezamoddin (Supervisor)
    We explain a new trust-region method for solving unconstrained optimization problems recently introduced in the literature, where the radius update is computed using the information at the current iterate rather than at the preceeding one. The update is then performed according to how well the current model retrospectively predicts the value of the objective function at the last iterate. Global convergence to first- and second-order critical ponits is proved under classical assumptions. Preliminary numerical expriments on CUTEr problems with MATLAB7.7 indicate that the new method is very competitive  

    Numerical Investigation of Combustion of Cryogenic H2-O2 Propellant under Sub-Critical Condition

    , M.Sc. Thesis Sharif University of Technology Ghasempour, Arash (Author) ; Mardani, Amir (Supervisor) ; Farshchi, Mohammad (Supervisor)
    The present work is concerned with numerical simulation of spray flame for rocket combustor (MASCOTTE A-10 test case at 10 bar pressure) based on cryogen gaseous hydrogen and liquid oxygen at specific condition. This liquid oxygen and gaseous hydrogen single element combustor experiment has been the focus of many numerical studies which is representative of combustion in rocket combustion chamber condition. The purposed strategy relies on hybrid Eulerian-Lagrangian framework that continuous phase is evaluated by Reynolds average Navier-stokes (RANS) equation with quick discretization method and dispersed phase of combustion chamber atmosphere is evaluated by discrete phase method (DPM). To... 

    Numerical Study of Pile Behavior under Seismic Loading

    , M.Sc. Thesis Sharif University of Technology Mashinchian, Mohammad Javad (Author) ; Ahmadi, Mohammad Mahdi (Supervisor)
    Numerous structures which are involved in seismic soil-pile-structure interaction have been destroyed. Considering complexities which exist in soil-pile interaction problems and lack of precise methods without imperfect bases, it is necessary to use numerical methods for analyzing soil-pile interaction problems. In this research, three-dimensional modeling and studying the effect of changing soil and pile parameters on the behavior of pile under earthquake loading is performed using finite difference software, FLAC3D. The soil in this model has a softening behavior. Real earthquake spectrum has been applied into the model as the acceleration time history at the bedrock level. The results of... 

    An Investigation on the Effects of Porous Media on Propagation of Aero-acoustic Waves, Using LBM

    , M.Sc. Thesis Sharif University of Technology Oveisi, Saeed (Author) ; Tayyebi Rahni, Mohammad (Supervisor) ; Massah, Hamid Reza (Co-Advisor)
    With advances in technology, production and propagation of sound waves in the air has become very important. One of the main goals of study of these waves is controlling them. The environment plays the most important role in sound propagation. Therefore, the properties of the environment and their effects should be studied. One such concern studied widespread previously, is porosity and porous media effects on the properties of a fluid flow and sound waves through it. An important application of this study is sound proofing systems. In this project two-dimensional numerical simulation of aeroacoustic waves passing through a porous media is carried out, using Lattice Boltzmann Method. The aim... 

    Numerical Evaluation of Engine Performance and Emission Characteristics of Rapeseed Oil and its Blends in Diesel Engines

    , M.Sc. Thesis Sharif University of Technology Saeedan, Mohammad (Author) ; Saeedi, Mohammad Hassan (Supervisor)
    Today, the importance of transportation and motor vehicles is crystal clear for everyone. On the other hand, energy crisis and the emissions of these vehicles are two fundamental problems of internal combustion motors. On account of this, the diesel vehicles have absorbed researchers’ attentions due to their higher efficiency and low fuel consumption.Due to high diesel vehicle efficiency, it is tried to substitute gasoline vehicles with these vehicles. In addition, the unrecyclable nature of fossil fuels has led to more attention to renewable energies such as biofuels. A lot of kinds of herbal oils have identical characteristics with diesel fuel.In this research, the combustion of Rapeseed... 

    Numerical and Analytical Investigation of Unequal Size Droplets Generation Process in Micro and Nano Channels

    , Ph.D. Dissertation Sharif University of Technology Bedram, Ahmad (Author) ; Moosavi, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Co-Advisor)
    In this paper, we introduced two methods for producing unequal sized droplet from an initial one that don’t have the disadvantages of the available methods. We developed a comprehensive analytical theory for the T-junction with valve method. Also the geometry was simulated using a VOF algorithm and a comparison was performed between numerical and analytical results and very good agreement was observed. The accuracy of numerical results was confirmed by doing the grid independency and time step independency and comparing the results with two analytical benchmarks. We derived accurate analytical relations for calculating the droplet volume ratio, droplet length (L1, L2 and Lwhole) and pressure... 

    Numerical Investigation of Cavitation Phenomenon in the Turbopump Inducer of Cryogenic Engines

    , M.Sc. Thesis Sharif University of Technology Sedaghi, Reza (Author) ; Farshchi, Mohammad (Supervisor) ; Ebrahimi Chamgardani, Abbas (Supervisor)
    Simulation of the flow inside a turbopump inducer of a cryogenic engine, can help to reduce the number of experimental tests in the design phase. In cryogenic engines, high speed of the turbo pump, engine working at off-design conditions, startup and shutdown of the engine, can cause the pressure to drop below the vapor pressure at the inducer blades. In such circumstances, cavitation bubbles start to grow and collapse as they are washed by the flow to the regions with higher pressure. Cavitation is the rapid formation and collapse of vapour cavities in a liquid.The energy required for evaporation is received from the surrounding liquid which causes the temperature to drop in the... 

    Numerical and Semi-Empirical Investigation of Pulsating Heat Pipe

    , M.Sc. Thesis Sharif University of Technology Arabnejad, Sajad (Author) ; Shafii, Mohammad Behshad (Supervisor) ; Saboohi, Yadollah (Supervisor)
    Thermal management of electronics is a contemporary issue which is increasingly gaining importance in line with the advances in packaging technology. Immediate and consistent multi-disciplinary research is needed to cater to the prevailing trends of net power and flux levels of upcoming microelectronics products. Material science, packaging concepts, fabrication technology and novel cooling strategies are some of key areas requiring synchronal research for successful thermal management. Focusing on the latter area, this thesis attempts to describe the complex thermo-hydrodynamics of Closed Loop ... 

    Numerical investigation of nanofluid mixed-convection flow in the entrance region of a vertical channel partially filled with porous medium

    , Article Heat Transfer - Asian Research ; Vol. 43, issue. 7 , November , 2014 , p. 607-627 Hajipour, M ; Dehkordi, A. M ; Jamshidi, S ; Sharif University of Technology
    In this article, transient two-dimensional mixed convection of nanofluids in the entrance region of a vertical channel has been studied carefully. The geometry under consideration consisted of a parallel-plate channel partly filled with a porous medium with a constant wall temperature. In the free flow region, the two-dimensional flow field has been governed by the Navier-Stokes equations. The general formulation of the momentum equations accounting for the inertial and the viscous effects in the presence of a porous medium has been used. Viscous dissipation effects have also been incorporated in the thermal energy equation. Effects of Brownian diffusion and thermophoresis have also been... 

    Experimental & numerical investigation of losses in centrifugal compressor components

    , Article Proceedings of the ASME Turbo Expo, San Antonio, Tx ; Volume 6 C , 2013 ; ISBN: 9780791855249 Doustmohammadi, A. A ; Hajilouybenisi, A ; Mojaddam, M ; Sharif University of Technology
    In this research an analytical model for performance prediction of centrifugal compressors is developed. The loss mechanisms are investigated in impeller, diffuser and volute separately for wide operating rotational speeds of the compressor. The contributions of compressor components in total entropy generation are further studied using different experimental correlations and methods. The results are verified using experimental test results, carried out at Sharif University of technology Turbocharger laboratory which has been designed to derive performance curves of turbocharger compressors. The test rig is equipped to measure static and stagnation pressures at inlet and outlet of each... 

    Numerical investigation on the effect of the size and number of stages on the tesla microvalve efficiency

    , Article Journal of Mechanics ; Volume 29, Issue 3 , 2012 , Pages 527-534 ; 17277191 (ISSN) Mohammadzadeh, K ; Kolahdouz, E. M ; Shirani, E ; Shafii, M. B ; Sharif University of Technology
    In the present study, the effect of the number of stages of Tesla Micro-Valve (TMV), as well as the dependency of Reynolds number, Re, on the valve performance has been analyzed. For this purpose, different layouts include one to four-stage with different sizes are investigated numerically. The main criterion for evaluation of valves performance is diodicity, Di. Unsteady and steady flow in valve have been simulated and compared. It is shown that although there are some difference but the trend is similar for both responses. Finally, 2-D and steady state computations of the fluid flow have been utilized that reveal a strong dependence of Di on Re and pressure drop, ΔP. The results showed... 

    A numerical investigation on effects of the gap between plates of Savonius vertical axis wind turbines with different shapes on their performance

    , Article ASME 2012 Gas Turbine India Conference, GTINDIA 2012, 1 December 2012 through 1 December 2012 ; December , 2012 , Pages 259-264 ; 9780791845165 (ISBN) Abbaszadeh, M ; Doroodian, F ; Sharif University of Technology
    Present study introduces the vertical gap between the blades of a Savonius rotor's blades as a parameter that can enhance performance of the rotor. To provide comprehensive concept about application of gap between blades, two different models were tested in different working conditions and working regimes. The study completed by using R.S.M. turbulence model through ANSYS Fluent commercial software package. Utilization of the method was validated by comparing results of a conventional model with experimental data from one of the references. Results of the study proved that application of a proper gap between blades can improve rotor's moment coefficient by 20 percent; however, the amount of... 

    Effects of cylinder diameters, reynolds number and distance between two-tandem cylinders on the wake profile and turbulence intensity

    , Article ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011 ; Volume 1, Issue PARTS A, B, C, D , 2011 , Pages 3441-3447 ; 9780791844403 (ISBN) Rahimzadeh, A ; Jafarian, M. M ; Khoshnevis, A ; Sharif University of Technology
    A series of experimental and numerical investigations on two tandem cylinders wake have been studied. The velocity profile and turbulence intensity have been acquired by a single one dimensional Hot Wire anemometer. The two cylinders were mounted in a tandem manner in the horizontal mid plane of the working section. The effect of the upstream cylinder diameter, Reynolds number and the distance between the cylinders on the wake profile and turbulence intensity on the downstream cylinder was investigated, while the Reynolds number ranged between1.5× (10)∧4 ∼ 3×(10)∧4. The upstream cylinder diameter (d) was 10, 20 and 25 mm, while the downstream cylinder diameter (D) was 25 mm, corresponding to... 

    Optimization of the switching surface for the simplest passive dynamic biped

    , Article Proceedings of the 17th International Conference on Advanced Robotics, ICAR 2015, 27 July 2015 through 31 July 2015 ; July , 2015 , Pages 363-368 ; 9781467375092 (ISBN) Safa, A. T ; Naraghi, M ; Alasty, A ; Saranli U ; Kalkan S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Recently, it has been proved that a different switching surface can preserve the walking trajectory while varying the walking stability [1], [2]. In this paper, by employing the simplest passive dynamic biped, we optimize the switching surface to maximize the robot's stability. Here, the stability measure is preferably the size of the basin of attraction, i.e. the collection of all possible initial conditions leading to the system's equilibrium point. Numerical investigations indicate that the maximum stability is obtained for neither the highest nor the lowest walking speed