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parseh--kaveh
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Assessment of characteristic boundary conditions based on the artificial compressibility method in generalized curvilinear coordinates for solution of the euler equations
, Article Computational Methods in Applied Mathematics ; 2017 ; 16094840 (ISSN) ; Hejranfar, K ; Sharif University of Technology
2017
Abstract
The characteristic boundary conditions are applied and assessed for the solution of incompressible inviscid flows. The two-dimensional incompressible Euler equations based on the artificial compressibility method are considered and then the characteristic boundary conditions are formulated in the generalized curvilinear coordinates and implemented on both the far-field and wall boundaries. A fourth-order compact finite-difference scheme is used to discretize the resulting system of equations. The solution methodology adopted is more suitable for this assessment because the Euler equations and the high-accurate numerical scheme applied are quite sensitive to the treatment of boundary...
Development of a high-order compact finite-difference total Lagrangian method for nonlinear structural dynamic analysis
, Article Applied Mathematical Modelling ; Volume 63 , 2018 , Pages 179-202 ; 0307904X (ISSN) ; Hejranfar, K ; Sharif University of Technology
Elsevier Inc
2018
Abstract
A high-order compact finite-difference total Lagrangian method (CFDTLM) is developed and applied to nonlinear structural dynamic analysis. The two-dimensional simulation of thermo-elastodynamics is numerically performed in generalized curvilinear coordinates by taking into account the geometric and material nonlinearities. The spatial discretization is carried out by a fourth-order compact finite-difference scheme and an implicit second-order accurate dual time-stepping method is applied for the time integration. The accuracy and capability of the proposed solution methodology for the nonlinear structural analysis is investigated through simulating different static and dynamic benchmark...
Assessment of characteristic boundary conditions based on the artificial compressibility method in generalized curvilinear coordinates for solution of the Euler equations
, Article Computational Methods in Applied Mathematics ; Volume 18, Issue 4 , 2018 , Pages 717-740 ; 16094840 (ISSN) ; Hejranfar, K ; Sharif University of Technology
De Gruyter
2018
Abstract
The characteristic boundary conditions are applied and assessed for the solution of incompressible inviscid flows. The two-dimensional incompressible Euler equations based on the artificial compressibility method are considered and then the characteristic boundary conditions are formulated in the generalized curvilinear coordinates and implemented on both the far-field and wall boundaries. A fourth-order compact finite-difference scheme is used to discretize the resulting system of equations. The solution methodology adopted is more suitable for this assessment because the Euler equations and the high-accurate numerical scheme applied are quite sensitive to the treatment of boundary...
Unsteady preconditioned characteristic boundary conditions for direct numerical simulation of incompressible flows
, Article AIAA Journal ; Volume 58, Issue 4 , 2020 , Pages 1476-1489 ; Hejranfar, K ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2020
Abstract
The unsteady preconditioned characteristic boundary conditions (UPCBCs) based on the artificial compressibility (AC) method are formulated and applied at artificial boundaries for the direct numerical simulation (DNS) of incompressible flows. The compatibility equations including the unsteady terms are mathematically derived in the generalized curvilinear coordinates and then incorporated as boundary conditions (BCs) in a high-order accurate incompressible flowsolver. The spatial derivative terms of the systemof equations are discretized using the fourth-order compact finite difference (FD) scheme, consistent with the high-order accuracy required for the DNS. The time integration is carried...
Development of Characteristic Boundary Conditions with Artificial Compressibility Method by Compact Finite-Difference Discretization
, Ph.D. Dissertation Sharif University of Technology ; Hejranfar, Kazem (Supervisor)
Abstract
In the present study, the preconditioned incompressible Navier‐Stokes equations with the artificial compressibility (AC) method formulated in the generalized curvilinear coordinates are numerically solved by using a high‐order compact finite‐difference scheme for accurately and efficiently computing the incompressible flows. A fourth‐order compact finite‐difference scheme is utilized to discretize the spatial derivative terms of the resulting system of equations and the time integration is carried out based on the dual time‐stepping method. The capability of the proposed solution methodology for computing the steady and unsteady incompressible viscous flows in a wide range of Reynolds...
Developing a Compact Finite Difference Method for Solving Fluid - Solid Interaction in Incompressible Flow
, M.Sc. Thesis Sharif University of Technology ; Hejranfar, Kazem (Supervisor)
Abstract
In this study, fluid-solid interaction (FSI) is simulated computationally by using a high-order accurate numerical method. The two-dimensional incompressible viscous flows are considered in the fluid domain. The primary problem with solutions of the incompressible Navier–Stokes equations is the difficulty of coupling changes in the velocity field with changes in the pressure field while satisfying the continuity equation. Herein, the artificial compressibility method is used to overcome this difficulty. Preconditioning is implemented to reduce the stiffness of the system of equations to increase the convergence rate of the solution. Using preconditioning, physical solutions even at low...
Control of continuous time chaotic systems with unknown dynamics and limitation on state measurement
, Article Journal of Computational and Nonlinear Dynamics ; Volume 14, Issue 1 , 2019 ; 15551415 (ISSN) ; Salarieh, H ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2019
Abstract
This paper has dedicated to study the control of chaos when the system dynamics is unknown and there are some limitations on measuring states. There are many chaotic systems with these features occurring in many biological, economical and mechanical systems. The usual chaos control methods do not have the ability to present a systematic control method for these kinds of systems. To fulfill these strict conditions, we have employed Takens embedding theorem which guarantees the preservation of topological characteristics of the chaotic attractor under an embedding named "Takens transformation." Takens transformation just needs time series of one of the measurable states. This transformation...
A new approach to extreme event prediction and mitigation via Markov-model-based chaos control
, Article Chaos, Solitons and Fractals ; Volume 136 , 2020 ; Salarieh, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Despite that the border between chaotic and stochastic systems is exactly defined, scientists, use high dimensional chaotic dynamics to model numerous stochastic models and sometimes use stochastic models to study chaotic systems. In this paper, we have investigated chaotic systems with a stochastic approach and proposed an estimator for the chaotic system which is used to present different algorithms for chaos control, extreme event prediction and extreme event mitigation. The stochastic estimator is constructed by meshing the phase space and applying the cell mapping method (with some considerations) which provides us with a model-free approximation of the systems. The algorithms are ideal...
Control of continuous time chaotic systems with unknown dynamics and limitation on state measurement
, Article Journal of Computational and Nonlinear Dynamics ; Volume 14, Issue 1 , 2019 ; 15551415 (ISSN) ; Salarieh, H ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2019
Abstract
This paper has dedicated to study the control of chaos when the system dynamics is unknown and there are some limitations on measuring states. There are many chaotic systems with these features occurring in many biological, economical and mechanical systems. The usual chaos control methods do not have the ability to present a systematic control method for these kinds of systems. To fulfill these strict conditions, we have employed Takens embedding theorem which guarantees the preservation of topological characteristics of the chaotic attractor under an embedding named "Takens transformation." Takens transformation just needs time series of one of the measurable states. This transformation...
An overview: recent development of semiconductor/graphene nanocomposites for photodegradation of phenol and phenolic compounds in aqueous solution
, Article Journal of Asian Ceramic Societies ; Volume 9, Issue 1 , 2021 , Pages 343-365 ; 21870764 (ISSN) ; Alijani, H ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
The development of graphene-based nanocomposites is currently the issue of enormous research interest. Recent advancements have exhibited that semiconductor/graphene nanocomposites can be purposed as a promising new category of catalysts for the heterogeneous photocatalytic treatment of wastewaters. Since semiconductor/graphene nanocomposites have been found efficient in degradation of organic pollutants, photodegradation of phenol and phenolic compounds as hazardous contaminants in aqueous solution has been most widely investigated by these aforementioned nanocomposites. In the present review, after introduction on the properties and the different synthesis methods of semiconductor/graphene...
Simultaneous removal of mercury ions and cationic and anionic dyes from aqueous solution using epichlorohydrin cross-linked chitosan @ magnetic Fe3O4/activated carbon nanocomposite as an adsorbent
, Article Diamond and Related Materials ; Volume 124 , 2022 ; 09259635 (ISSN) ; Bagherzadeh, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
An economical epichlorohydrin cross-linked chitosan @ magnetic Fe3O4/activated carbon nanocomposite, CH-EP@Fe3O4/AC, was successfully synthesized and used as a suitable adsorbent material for removal of a triphenylmethane cationic dye, Malachite green (MG), an anionic dye, Reactive red 120 (RR120), and Mercury ions (Hg2+) from aqueous solution. The prepared adsorbent has been characterized with Fourier transform infrared spectroscopy, X-ray diffraction, Scanning electron microscopy, Thermogravimetric analysis, Brunauer–Emmett–Teller analysis as well as Vibrating sample magnetometer. According to the result of Brunauer–Emmett–Teller isotherm, the prepared adsorbent has a specific surface area...
Aerodynamic Instability Modeling of a High Speed Centrifugal Compressor
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
The present thesis investigates the surge phenomenon of high speed centrifugal compressors. Surge is a highly undesired condition and may cause severe damage to the machine and thus the plant. Traditionally, surge is avoided via a surge avoidance scheme wih recycle valve in discharge at the most common approach. A one dimensional technique is developed where the Greitzer lumped parameter model along with the Gravdahl one dimensional model is considered as the basis. Shaft dynamics, volume dynamics, losses, energy transfer and time lag are imbedded in the present model to improve the prediction of the compressor characteristics beyond the stability region. On the other hand, in order to...
Aerodynamic Design Methodology for Changing Axial Compressor Capacity
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
Axial compressor design is a very complex and expensive process. In general, for design and development of a new axial compressor, manufacturing companies usually intend to employ an existing and successful axial compressor as an starting point and modify and upgrade it. In this regard, dimensional scaling is a common method for derivative axial compressors. The goal of dimensional scaling is to get a different capacitywhile minimizing the development time and cost. In this thesis, theNASA eight stage transonic axial flow compressor is chosen as the base model for dimensional scaling to lower and upper size of its original dimension. The scaled compressor is analyzed with a quasi 2-D code....
Development of a Design Tool for Restaging of Centrifugal Compressors
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, kaveh (Supervisor)
Abstract
The purpose of this research is theoretical and numerical investigations on centrifugal compressor. A computer code has been developed to simulate single-zone and two-zone model, based on the revised formulation for real gas, using Peng-Robinson equations. Single-zone modeling, also known as meanline method, established based on 1-D equations of fluid dynamics considering ideal gas relations, empirical loss correlations, slip factors, impeller efficiency and no wake or separation regions. Considering usual significant separated regions in the gas path of impellers, two-zone (jet and wake zone) model has been developed to achieve a more reliable simulation by using fewer correlations based on...
Design of Heat Exchanger in Thermoacoustic Systems
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
In this research, the principles of design of Heat Exchangers in thermoacoustic systems are developed. The Heat Exchangers as a essential part of thermoacoustic systems, complete the thermodynamic cycle in these systems. In this thesis, principles and algorithms of design for Shell&Tube, Plate and Screen Heat Exchangers are described and these principles are validated for each kind of Heat Exchangers. Then the balance of exergy is studied in thermoacoustic systems and at the end, for every Heat Exchangers amount of exergy destruction is evaluated for oscillating and non-oscillating fluids. Based on fitness functions of exergy destruction, heat transfer area and acoustic pressure drop, Heat...
Modeling and Developing a Control System for Centrifigual Compressors
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
Compression systems are widely used in industry. Dynamic Modeling is a necessary step in design procedure of a safe compression system. A dynamic model should be adequate and simulate dominant elements of system. One important element of industrial compression systems is downstream pipelines. In this work, a dynamic model including pipeline acoustics is developed. It is accepted that changes of working gas molecular weight can cause inception of instabilities in compression systems. The dynamic model used to study mechanisms of these instabilities. A conventional control system is modeled and tuned for the compression system. The ability of this control system to prevent such instabilities...
Preliminary Analysis of a Thermo Acoustic Heat Pump (THP) In Lab Scale
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
thermoacuostic heat pump (THP) is One of the most important thermoacuostic applications which is used for heat lost recovery in industrial applications and civil applications.In this project, we have a quick review on thermoacuostic theory and researches in this field. Also a thermoacuostic heat pump in a lab scale will be designed and analyzed.For achieving this goal, first, mathematical equations of thermoacuostic systems are reviewed; a thermoacuostic heat pump is designed on the base of Tijani method and final model is validated by DeltaEC software. In the next step, after investigating about laboratory equipments which is used in testing process, we generate test matrix and study about...
Exergy Analysis of Thermoacoustic Heat Pump with Industrial Application
, Ph.D. Dissertation Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
Typical thermoacoustic systems deal with the conversion of heat energy to sound energy and vice versa. Recent advances in the field of thermoacoustics have altered the working mechanism of many conventional heating and cooling devices. These systems have three highlighted advantages: first, they have simple structure, no moving parts, low cost of manufacture, and high reliability; second, by using inert gases as working fluid, they are environmentally friendly; and finally, heat driven thermoacoustic devices can be driven by low quality energy sources such as waste heat and solar energy.
The main focus of the present thesis is on the application of the thermoacoustic technology in the...
The main focus of the present thesis is on the application of the thermoacoustic technology in the...
Numerical Study of Streaming in Thermal Buffer Tube
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
Streaming has some applications in medical and industrial science. This phenomena can increase or decrease efficiency of an acoustic system. Deliberate streaming used to eliminate heat exchanger is an example of desired applications. In the most cases, secondary flow is an undesired issue. Streaming in thermal buffer tube (TBT) of thermoacoustic stirling heat engine (TASHE) has some unwanted effects. The main goal of author is to simulate numerically periodic field in TBT with axisymmetric geometry and study the effects of variating geometry and turbulence on the intensity of streaming. According to inaccessible boundary conditions in TBT of TASHE, firstly, the field is numerically solved...
Conceptual Design of a 1 MW Axial Flow Pump with Variable IGV
,
M.Sc. Thesis
Sharif University of Technology
;
Ghorbanian, Kaveh
(Supervisor)
Abstract
Considering the multi-disciplinary aspects as well as the importance of a wide performance map of a propulsion system, this thesis is focused on the preliminary design aspects of an axial flow pump with an inlet guide vane. First, a one-dimensional design algorithm is developed. The code is used to perform a preliminary design of a prototype pump. The results are used to carry on a detailed 3D design by using commercial software. The obtained geometry and performance map are compared with available data. Finally, the finalized code is employed to design and analyze a one megawatt axial pump with and without inlet guide vanes