rahim shamsoddini

One of the main problems in liquid transfer tanks is the sloshing phenomenon. This phenomenon, which is associated with regular or irregular liquid waves inside the tank, can cause many risks. One of the most widely applied methods to control the fluctuations caused by the sloshing phenomenon is the use of baffles. Baffles are usually installed vertically or horizontally on the inner wall of the tank. In uniform samples (simple baffle), the hydrodynamic force on the baffle is significant. Therefore, in this research, mesh baffle from the category of permeable baffles is introduced and tested, which can significantly reduce the hydrodynamic forces on the baffle. Therefore, in the present work, the sloshing phenomenon in a rectangular tank is first modeled by Smoothed Particle Hydrodynamics (SPH) and validated. Then, the tank with a simple baffle and mesh baffle are modeled and examined. During the numerical solution (in each time interval), the hydrodynamic forces acting on the baffles are monitored and extracted. The comparison of the obtained results shows that in addition to reducing the fluctuations of the sloshing phenomenon, the mesh baffle also creates a lower hydrodynamic resistance force.

Most of the pollution of dams, lakes and even coastal water is related to their upstream bed. When floods and drifts occur, the pollutants in the bed are carried into these bodies of water. There are several factors that influence the rate at which these pollutants are emitted. Among these factors, the material and slope of the bed play a crucial role, yet they have not been thoroughly investigated until now. Therefore, this study aims to model this phenomenon and examine the aforementioned parameters using a Lagrangian numerical method. The numerical method developed is the Smoothed Particle Hydrodynamics (SPH). The flow consists of two phases, one phase is considered a Newtonian fluid while the other phase is considered a non-Newtonian fluid. Due to the momentum of the fluid and the sharp changes in the flow, turbulent flow is assumed, and by approximating and calculating the turbulent viscosity, its effects are considered in the modeling. In addition to the fluid motion equations, the concentration equation is also solved to calculate the emission rate. After validating the computational code, nine different cases are modeled and evaluated based on the bed material and the slope of the bed. The results show that the change in each of these parameters has a significant effect on the emission of pollutants.

Mixing and homogenization of cement paste are some of the most used phenomena in the construction and building industries. In most cases, a homogeneous mixture of cement paste is required and this is supplied by rotary mixers. In the present study, the rotary cement paste mixers in two-dimensional (2D) conditions are investigated by an Incompressible Smoothed Particle Hydrodynamics (ISPH) method. The method is validated and then used to model the cement paste mixer. The cement paste is considered a Bingham fluid. Two types of mixers are examined; shear mixer and blender. An appropriate mixing index that was previously applied to the discrete element method was successfully implemented for the ISPH method, and the performance of these two types of mixers is analyzed with this mixing index. The results show that the Reynolds number has a key role in the mixing in the shear mixers. In the low Reynolds numbers, an unmixed region is formed, which decreases with increasing Reynolds numbers. In blender mixers, the mixing rate is expected to increase with the multiplicity of vortices formed. But the coordinated motion of the vortices with the blades causes a fluid mass to move. Also, the resistance of the fluid to the moving components of the mixer is calculated and the difference in the performance of the two mixers in terms of energy consumption and mixing speed is compared and discussed.

Due to importance of pigging operations for purposes such as monitoring-cleaning, which leads to an increase in the service life of pipeline networks, management, and optimization of energy consumption in oil and gas industries, providing accurate numerical models is a research need that has been very vital. Considering advantages of meshless methods, for the first time in this research a model is presented for evaluating the flow around the pig using the smooth particle hydrodynamics (SPH) method and the standard k-ε model to simulate the turbulence of the flow. Besides, the performance of the model based on the experimental study has been evaluated and validated. The results showed that the average error rate of the SPH model compared to the laboratory model was less than 5%, which indicated the research model's high accuracy and acceptable performance. After validating the performance of the research model, the simulation of the flow around the stationary and mobile pig was modeled, and the results were compared and evaluated with the existing numerical results. In addition, by using a meta-heuristic algorithm of gray wolves optimization (GWO), studies wereconducted on the relative diameter parameter of the bypass pig to achieve optimal values of this parameter. The results of the optimization model showed that the optimal relative diameter of the bypass pig was equal to d⁄D=0.418. The results of this research showed that the presented model had an acceptable accuracy in modeling the flow around the bypass pig in the pipe, and it could also be used as a reference model based on the SPH method for modeling the flow around the bypass pig.

Liquid sloshing is a common phenomenon in the transporting of liquid tanks. A safe liquid transporting needs to control the entered fluctuating forces to the tank walls, before leading these forces to large forces and momentums. Using predesigned baffles is a simple method for solving this problem. Smoothed Particle Hydrodynamics is a Lagrangian method that has been widely used to model such phenomena. In the present study, a three-dimensional incompressible SPH model has been developed for simulating the liquid sloshing phenomenon. This model has been improved using the kernel gradient correction tensors, particle shifting algorithms, turbulence model, and free surface particle detectors. The results of the three-dimensional numerical model are compared with an experimental model, showing a very good accuracy of the three-dimensional numerical method used. This study aims to investigate vertical baffle effects on the control and damping of liquid sloshing. The results of the present investigation show that in this particular case, by using baffles, it is possible to reduce more than 50% of the maximum value of pressure fluctuations in the slashing phenomenon.

The mesh generation process as a time-consuming and computational effort in the numerical methods always has been paid attention to by researchers to provide more accurate and fast methods. In this study, an accurate, fast, and user-friendly method of mesh generation has been developed by combining the image processing method with Computational Fluid Dynamics (CFD). For this purpose, a turbulent flow around a single square as a bluff body is simulated by homemade code using MATLAB software as a test case to illustrate the mentioned method. The conservative Equations have been discretized using the finite volume method based on the Power-la scheme. Utilizing useful filters on the imported gray-scale digital image provides edge detection of the obstacle in the computational domain. After the edge detection step, an orthogonal, structured, and staggered mesh is generated.

Solving many important industrial problems requires knowing the values of the heat transfer coefficient of passing of one or more fluid streams in different equipment, systems or pipes. In the present study, a numerical model has been developed to simulate compressible fluid flow at the inlet of a hot pipe with different angles to the horizon. In this zone, the hydrodynamic and thermal boundary layers of the fluid flow are developing. Due to the turbulence of the fluid flow due to the interaction of heat and fluid flow inside this tube, a three-dimensional turbulent model was used for this simulation. For this purpose, continuity and compressible Navier-Stokes equations, Reynolds stress model, and turbulent and compressible energy equation have been solved simultaneously. Then, using a set of numerical runs by the concepts of experimental design and optimization methods, a predictive formula for the Nusselt number for these flows has been obtained. Finally, the ability of this formula has been investigated using a set of laboratory data.

In the present study, a one-dimensional unsteady-state model is developed to investigate an industrial Acheson reactor for producing SiC. The mechanisms of the SiO2 melting and converting to SiC are investigated using the experimental data of previous works. Additionally, the obtained models are utilized in the developed mathematical model. The finite difference method is used for the simulation of the developed model. The accuracy of the presented model is validated by empirical data. The complete discussions of the reaction progress, melting process, variations of the bed, and also the temperature inside the bed are presented. Attending to the importance of the existing competition between the melting of SiO2 and converting to SiC, these mechanisms are investigated using the presented data in previous relevant studies and the obtained models are utilized in the developed mathematical model. The model predictions show that the final produced cylinder of SiC at the center line of the reactor occupies 8.05% of the reactor diameter and has 8.16% weight loss during the production process.

In the thermodynamic of non-ideal solutions, there are two valuable approaches for linking the saturated vapor and liquid phases in an equilibrium system, i.e. the γ-φ and φ-φ approaches. Nevertheless, these methods are complex and need huge calculation procedures. Therefore, developing novel equations, with a simple format, is necessary for decreasing the size of the calculation procedure or increasing the accuracy of the predicted values for the required thermodynamic parameters. This study aims to develop a simple and accurate (with less than 5% mean absolute error for several cases of validation) relation among the thermodynamic parameters of two phases of a pure or binary mixture vapor-liquid equilibrium system. The format of this equation is very simple, which improves its applicability for solving various thermodynamic problems in vapor-liquid equilibrium systems. For this purpose, the compressibility factors of each phase that are suitable combinations of the PVT parameters of the system, are chosen for relating the thermodynamic parameters of these phases. Therefore, obtaining a relation between the compressibility factors of the saturated liquid and vapor phases relates the PVT parameters of these phases to each other. Although the idea of this theory-based equation has been raised from the investigation of equilibrium PVT values of pure substances, this equation has also been validated using the experimental PVTxy data of several binary mixtures. Comparing the predictions of the obtained equilibrium equation with the experimental data of pure and binary mixtures approves the accuracy of the predictions of the obtained equation.

Electroosmotic is one of the four electrokinetic phenomena that is formed by applying an electric field to an ionized electrolyte near the charged dielectric surface. Due to the applying of this electric field change the arrangement of ions within the electrolyte, and eventually a region called the Electric double layer is formed near the surface. The thickness of this layer is approximated by the Debye length. In this study, the Because the Reynolds number in in microfluidic devices is usually very low. Therefore, achieving to sufficient mixing in electroosmotic microchannel flow has been a challenge. For this purpose, a non uniform distribution of surface potential for flow mixing is considered. This type of charge distribution is very efficient for mixing purposes by creating circulations in the microchannel. Lagrangian description is used to solve the governing equations. The method used in this research is the constant density weakly compressible particle hydrodynamics method. In order to improve the mixing, the effect of changing the Debye length has been analyzed. The results show that increasing the Debye length causes smaller vortexes to be produced and mixing efficiency is reduced.

Liquid sloshing is a common phenomenon in the transporting of liquid tanks. Liquid waves lead to fluctuating forces on the tank wall. If these fluctuations are not predicted or controlled, they can lead to large forces and momentum. Baffles can control liquid sloshing fluctuations. One numerical method, widely used to model the liquid sloshing phenomena is Smoothed Particle Hydrodynamics (SPH). Because of its Lagrangian nature, SPH is suitable for simulating free surface flow. In the present study, a relatively accurate Incompressible SPH (ISPH) method improved by kernel gradient correction tensors, particle shifting algorithms, turbulence viscosity calculations, and free surface particle detectors is applied for the free surface flow modeling. In comparison to the other SPH Simulations and experimental data, these results show that the present algorithm is effective for simulating free surface problems. The present algorithm has been applied to simulate liquid sloshing phenomena, while the aim of this study is the investigation of vertical and horizontal baffle effects on the control and damping of liquid sloshing. Results show that for vertical baffles, baffle size has a major role in sloshing fluctuation damping. For horizontal baffles, also including size, the baffle base position has a significant role in liquid sloshing fluctuation damping. When horizontal baffle is near the free surface, sloshing fluctuation-damping increases.

Fluid mixing is a crucial and challenging process for microfluidic systems, which are widely used in biochemical processes. Because of their fast performance, active micromixers that use stirrer blades are considered for biological applications. In the present study, by using a robust and convenient Incompressible Smoothed Particle Hydrodynamics (ISPH) method, miscible mixing within a two-blade micromixer is investigated. The problem discussed herein is represented by an active micromixer comprising two stir-bars that rotate to mix the fluids. Because of its Lagrangian nature, Smoothed Particle Hydrodynamics is an appropriate and convenient method for simulating moving boundary problems and tracking the particles in the mixing process. Previous investigations have been carried out for mixing flow for a low Schmidt number. However, a low Schmidt number is barely applicable for liquid mixing. Hence, in the present study, the Schmidt number is considered to be Sc=1000. The present results show that the two-blade micro-channel mixer considerably improves the mixing rate in comparison with the one-blade micro-channel mixer.

In this present study, the mixing of two incompressible miscible fluids with different density and viscosity has been investigated in a two-dimensional microchannel equipped with an oscillating stirrer in different excitation frequency. Although most studies in the field of fluid mixing, have been studied the mixer performance when the two fluids were absolutely identical, but the mixing make sense when two fluids has been non-uniformity such as different temperature, concentration or properties. The aim of this study is to evaluating the effect of various properties of the fluids in mixer performance and mixing value. Simulation has been performed in Re=100 and Sc=10, between 0.1 to 1 strouhal number by using element based finite volume method by means of commercial code CFX. Mixer performance has been evaluated in three different modes: mixing of two identical fluids, mixing of two fluids with different density and mixing of two fluids with different viscosity. The results show that, mixing of the fluids with different properties leads to change in mixer performance, and has unique performance in each case. In comparison with similar properties fluids, mixing of fluids with different viscosity and density show lesser inclined in mixing. It has been shown that variation of strouhal number has lesser effect on mixing index changes. The ratio of maximum mixing index changes to base mixing index in the case of different density and viscosity is 54.01 and 51.15 percent, respectively, while the value is 577.94 percent for the mixing of similar fluids.

In the present study, the mixing fluids flow in the twin and circular mixers is investigated by using an improved robust weakly compressible Smoothed Particle Hydrodynamics method. In order to remove the Smoothed Particle Hydrodynamics complications and according to a predictive corrective scheme, a robust modified algorithm which uses the advanced second order discretization, pressure velocity decoupling, kernel gradient corrections and shifting algorithm is offered. After the verification and validation of the present algorithm for the moving boundary problems, the present algorithm is applied for investigation of the mixing behaviors of the two-blade circular and twin chamber mixers. By investigation of the mixing paths, the proper geometry for the two-blade mixers is proposed and examined. The effects of the rotation direction of the blades, geometry and Reynolds number on the mixing rate are investigated. The results show that the twin chamber mixer can improve the mixing performance over 60% in comparison with the circular chamber mixer while the case with circular chamber and same direction rotation of the blades has the weakest performance among the cases which have been examined.