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projection-method
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Simulation of 2-D dam break using improved incompressible smoothed particle hydrodynamics based on projection method
, Article Applied Mechanics and Materials ; Volume 390 , 2013 , Pages 81-85 ; 16609336 (ISSN) ; 9783037858332 (ISBN) ; Qate, M ; Javareshkian, A ; Farzbod, A ; Sharif University of Technology
2013
Abstract
This paper deals with numerical modeling of water flow which is generated by the break of a dam. The problem is solved by applying a new Incompressible Smoothed Particle Hydrodynamics (ISPH) algorithm based on projection method. The proposed ISPH model has two steps. In the first step, the incompressibility of fluid is maintained regarding to the changes of intermediate and initial particles densities at the first half-time step (stability step). In the second step, by computing the divergence of the intermediate secondary velocity at the second half-time step (accuracy step), the incompressibility is satisfied completely. In fact, by using this method both stability and accuracy are...
2D numerical simulation of density currents using the SPH projection method
, Article European Journal of Mechanics, B/Fluids ; Volume 38 , 2013 , Pages 38-46 ; 09977546 (ISSN) ; Firoozabadi, B ; Mahdinia, M ; Sharif University of Technology
2013
Abstract
Density currents (DCs) or gravity currents are driven by gravity in a fluid environment with density variation. Smoothed Particle Hydrodynamics (SPH) has been proved to have capabilities such as free surface modeling and accurate tracking of the immiscible-fluids interface that can be useful in the context of gravity currents. However, SPH applications to gravity currents have been limited to often-coarse simulations of high density-ratio currents. In this work, the SPH projection method is tried to solve currents with very low density-ratios (close to one), at a resolution, that captures the Kelvin-Helmholtz instabilities at the fluids interface. Existing implementations of the SPH...
Implementation of Time Splitting Projection Method in water hammer modeling in deformable pipes
, Article International Journal of Pressure Vessels and Piping ; Volume 98 , October , 2012 , Pages 30-42 ; 03080161 (ISSN) ; Borghei, S. M ; Bohluly, A ; Sharif University of Technology
Elsevier
2012
Abstract
In this paper Time Splitting Projection Method (TSPM) has been implemented to model transient flow in a deformable pipe. In addition a quasi-steady model and the Brunone unsteady model have been incorporated into the algorithm to consider the effect of static and dynamic friction on the shape and attenuation of pressure waves. The deformation of the cross section of the pipe due to the change of pressure has been considered using Hooke's Law of elasticity. Numerical results of the model have been compared with a simple analytical test and results of experimental measurements for water hammer problem with different Reynolds numbers in a simple pipeline system; besides, numerical stability...
Study of Rheology of Suspensions Using SPH Method and Immersed Boundary Method
, M.Sc. Thesis Sharif University of Technology ; Taghizadeh Manzari, Mehrdad (Supervisor)
Abstract
In this thesis, an Incompressible SPH (ISPH) method is used to simulate suspensions. A suspension is assumed to be a mixture of solid particles in a Newtonian fluid. First, renormalization tensors are applied to the discretized equations of SPH method. This leads to a higher accuracy in this method. It should be noted that the projection method is used for ISPH. After that, the Immersed Boundary Method (IBM) is used to model and simulate the presence of solid particles in fluid flow. Some modifications were necessary to use IBM with Lagrangian approach. Then, some benchmark problems are solved to validate the presented method. The main objective of the present thesis is simulation of...
Modified BFGS Method For Non-Convex Functions In Unconstrained Optimization
, M.Sc. Thesis Sharif University of Technology ; Mahdavi Amiri, Nezameddin (Supervisor)
Abstract
Nonlinear optimization is concerned with finding optimal solutions of optimization problems, where the objective function or some constraints are nonlinear. Since many issues in science and engineering can be expressed and formulated as a nonlinear problem, we investigate BFGS method, a successful iterative quasi-Newton method, for solving non-convex problems in unconstrained optimization. The method is based on the work of Yuan and his colleagues, making use of modified weak Wolfe-Powell line search, introducing a certain condition, introducing the next point if the condition is met, introducing a parabolic function if the condition is not established and obtaining the projection point and...
Iterative null space projection method with adaptive thresholding in sparse signal recovery
, Article IET Signal Processing ; Volume 12, Issue 5 , 2018 , Pages 605-612 ; 17519675 (ISSN) ; Asadi Kangarshahi, E ; Marvasti, F ; Sharif University of Technology
Institution of Engineering and Technology
2018
Abstract
Adaptive thresholding methods have proved to yield a high signal-to-noise ratio (SNR) and fast convergence in sparse signal recovery. The robustness of a class of iterative sparse recovery algorithms, such as the iterative method with adaptive thresholding, has been found to outperform the state-of-art methods in respect of reconstruction quality, convergence speed, and sensitivity to noise. In this study, the authors introduce a new method for compressed sensing, using the sensing matrix and measurements. In our method, they iteratively threshold the signal and project the thresholded signal onto the translated null space of the sensing matrix. The threshold level is assigned adaptively....
A new approach for vibration analysis of a cracked beam
, Article International Journal of Engineering, Transactions B: Applications ; Volume 18, Issue 4 , 2005 , Pages 319-330 ; 1728-144X (ISSN) ; Meghdari, A ; Ebrahimi, A ; Sharif University of Technology
Materials and Energy Research Center
2005
Abstract
In this paper the equations of motion and corresponding boundary conditions for bending vibration of a beam with an open edge crack has been developed by implementing the Hamilton principle. A uniform Euler-Bernoulli beam has been used in this research. The natural frequencies of this beam have been calculated using the new developed model in conjunction with the Galerkin projection method. The crack has been modeled as a continuous disturbance function in displacement field which could be obtained from fracture mechanics. The results show that the natural frequencies of a cracked beam reduce by increasing crack depth. There is an excellent agreement between the theoretically calculated...
Modeling and parallel computation of the non-linear interaction of rigid bodies with incompressible multi-phase flow
, Article Computers and Mathematics with Applications ; Volume 72, Issue 4 , 2016 , Pages 1055-1065 ; 08981221 (ISSN) ; Ghasemi, A. M ; Nikbakhti, R ; Ghasemi, A. R ; Hedayati, F ; Sharif University of Technology
Elsevier Ltd
Abstract
A computational tool is developed to capture the interaction of solid object with two-phase flow. The full two-dimensional Navier–Stokes equations are solved on a regular structured grid to resolve the flow field. The level set and the immersed boundary methods are used to capture the free surface of a fluid and a solid object, respectively. A two-step projection method along with Multi-Processing (OpenMP) is employed to solve the flow equations. The computational tool is verified based on numerical and experimental data with three scenarios: a cylinder falling into a rectangular domain due to gravity, transient vertical oscillation of a cylinder by releasing above its equilibrium position,...
Optimal placement of access points in cellular visible light communication networks: an adaptive gradient projection method
, Article IEEE Transactions on Wireless Communications ; Volume 19, Issue 10 , 2020 , Pages 6813-6825 ; Beyranvand, H ; Salehi, J. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
In this paper, a new approach toward the optimization of Access Point (AP) placement in cellular Visible light Communication (VLC) networks is proposed based on the projected gradient algorithm. The objective of the optimal placement problem is to maximize the average throughput of the network subject to constraints on the minimum illumination level and the minimum rate of the users. This optimization framework gives the enhanced AP deployment in case of users with static, nomadic, or completely mobile behavior. Taking the distribution of users, the receiver's field of view, reflection from walls and interference from neighboring APs into account makes the deployment problem complicated. To...
Parallelized numerical modeling of the interaction of a solid object with immiscible incompressible two-phase fluid flow
, Article Engineering Computations (Swansea, Wales) ; Volume 34, Issue 3 , 2017 , Pages 709-724 ; 02644401 (ISSN) ; Nikbakhti, R ; Ghasemi, A ; Hedayati, F ; Malvandi, A ; Sharif University of Technology
Abstract
Purpose - A numerical method is developed to capture the interaction of solid object with two-phase flow with high density ratios. The current computational tool would be the first step of accurate modeling of wave energy converters in which the immense energy of the ocean can be extracted at low cost. Design/methodology/approach - The full two-dimensional Navier-Stokes equations are discretized on a regular structured grid, and the two-step projection method along with multi-processing (OpenMP) is used to efficiently solve the flow equations. The level set and the immersed boundary methods are used to capture the free surface of a fluid and a solid object, respectively. The full...
Multivariate curve resolution-particle swarm optimization: A high-throughput approach to exploit pure information from multi-component hyphenated chromatographic signals
, Article Analytica Chimica Acta ; Volume 772 , 2013 , Pages 16-25 ; 00032670 (ISSN) ; Ebrahimi Najafabadi, H ; Jalali Heravi, M ; Sharif University of Technology
2013
Abstract
Multivariate curve resolution-particle swarm optimization (MCR-PSO) algorithm is proposed to exploit pure chromatographic and spectroscopic information from multi-component hyphenated chromatographic signals. This new MCR method is based on rotation of mathematically unique PCA solutions into the chemically meaningful MCR solutions. To obtain a proper rotation matrix, an objective function based on non-fulfillment of constraints is defined and is optimized using particle swarm optimization (PSO) algorithm. Initial values of rotation matrix are calculated using local rank analysis and heuristic evolving latent projection (HELP) method. The ability of MCR-PSO in resolving the chromatographic...
Modelling of power-law fluid flow through porous media using smoothed particle hydrodynamics
, Article Transport in Porous Media ; Volume 74, Issue 3 , 2008 , Pages 331-346 ; 01693913 (ISSN) ; Manzari, M. T ; Sharif University of Technology
2008
Abstract
The flow of non-Newtonian fluids through two-dimensional porous media is analyzed at the pore scale using the smoothed particle hydrodynamics (SPH) method. A fully explicit projection method is used to simulate incompressible flow. This study focuses on a shear-thinning power-law model (n < 1), though the method is sufficiently general to include other stress-shear rate relationships. The capabilities of the proposed method are demonstrated by analyzing a Poiseuille problem at low Reynolds numbers. Two test cases are also solved to evaluate validity of Darcy's law for power-law fluids and to investigate the effect of anisotropy at the pore scale. Results show that the proposed algorithm can...