Sharif Digital Repository

A new microfluidic device is introduced for sorting the particles based on the hydrodynamic resistance induced in a microchannel which is not needed for additional detection or sorting modules. Hydrodynamic resistance affects physical properties, such as size and deformability of the particle. This device could apply application in cell sorting for remedies, diagnostics, and industrial applications. The device design is performed using an equivalent resistance model, and also numerical simulations are performed. For validation of the results, they are compared with experimental results. Moreover, we will discuss threshold particle size and will introduce a way to approximate it to ... 

Numerous experimental and modeling efforts have been paid done to investigate the behavior of gas-solid fluidized beds. Existence of a velocity gradient in the axial direction in tapered fluidized beds causes unique dynamic characteristics of this type of beds relative to cylindrical fluidized beds. Because of these characteristics, fluidized beds with inclined walls have found wide applications in industrial processes. Gas bubbles play an important role in the hydrodynamics of bubbling gas-solid fluidized beds; so, fundamental understanding of the bubbling behavior of fluidized beds is required to describe bubble-related phenomena such as solids mixing, segregation, reaction conversion,... 

One of the key issues in the design of vessels is their proper stability and performance in waves. Therefore, the use of twin-hull vessel designs such as conventional catamaran and SWATH is suitable for improving stability and seakeeping quality. Although SWATH has a better seakeeping quality than a conventional catamaran, it has been observed that at high forward speeds, especially in head waves, the vertical motions of the vessel is greatly enhanced. Various methods such as correction of the hull form and the use of fin stabilizers can be used to modify SWATH vessel motion behavior. These control surfaces can respond appropriately to the dynamic forces from the waves, reducing the motions... 

In this study, heat transfer and fluid flow inside a rectangular microchannel with partial porous media is simulated numerically. Darcy-Brinkman-Forchheimer equations are used to model the porous media. The effect of height of porous media, permeability (Darcy number), porosity and inlet velocity (Reynolds number) on Hydrodynamic and heat transfer performance are examined. At different values of height of porous media 0.2, 0.4, 0.6, 0.8, and 1 mm the Nusselt number of microchannel are 1.72, 1.78, 1.86, 1.94, and 2.02 compared to the microchannel without porous media. And the porous drop are 1.09, 1.2, 1.49, 1.76, and 2.15 compared to the microchannel without porous media. And FOM are 1.78,... 

One main problem in many numerical simulations is the lack of sufficient infrastructure data to precisely model and analyze the flow through complex geometries. Since experimental procedures are generally very expensive; and sometimes impossible, it becomes necessary to find alternative ways such as numerical approaches to predict the flow behavior through complex geometries. The heat exchangers can be categorized as geometries with complex configuration and apparently expensive to solve numerically. They are widely used in different industries including the aerospace. The restrictions in design and implementation of aviation’s heat exchangers have promoted the related companies to converge... 

In this research, the numerical simulation of the natural convection is performed by using the smoothed particle hydrodynamics based on the artificial compressibility method. For this aim, the formulation of the artificial compressibility method in the Eulerian reference frame for the mass and momentum equations is written in the Lagragian reference frame and the Lagrangin form of the energy equation is also considered to compute the thermal effects. The benefit of the artificial compressibility-based incompressible SPH (ACISPH) method over the weakly compressible SPH (WCSPH) method for computing the natural convection is that there is no need in the formulation considered here to use any... 

The main goal of this study is simulation of the flow-like landslide phenomenon and investigation of the effect of bed material entrainment on its behavior. Debris flows are considered as one of the types of flow-like landslides, and flow of dry granular materials on horizontal and inclined beds as a simple model of these types of flows in nature is numerically simulated. Also, in order to investigate the effect of entrainment on dynamics of flow, a bed containing granular materials is installed on horizontal and inclined beds. The governing equations of the flow are solved in the continuum context using the Smoothed Particle Hydrodynamics (SPH) method and the depth-averaged assumptions are... 

Improving the performance of modular, low-cost autonomous underwater vehicles (AUVs) in such applications as long-range oceanographic survey, autonomous docking, and shallow-water mine countermeasures requires improving the vehicles’ maneuvering precision and battery life. These goals can be achieved through the improvement of the vehicle control system. A vehicle dynamics model based on a combination of theory and empirical data would provide an efficient platform for vehicle control system development, and an alternative to the typical trial-and-error method of vehicle control system field tuning. As there exists no standard procedure for vehicle modeling in industry, the simulation of... 

In heavy ion collisions, extremely large electromagnetic fields are produced by fast-moving charged nucleons. They are sufficiently large to affect the low energy QCD processes and thus produce observable effects, whose occurrence is, however, directly related to the lifetime of these fields. In the present dissertation, the evolution of electromagnetic fields is studied in a plasma of quarks and gluons, by analytically solving the equations of relativistic magnetohydrodynamics (RMHD). The onideal Bjorken RMHD is solved by introducing the method of nonconserved charges. Assuming an electromagnetic force-free condition, the electric and magnetic fields are found to be either parallel or... 

Many species in nature exist which human can reach the aims of flying and swimming by inspiring from them. Observations show that fish can use their especial undulating motions of body/fins to crusing, increase performance, suddenly acceleration, and maneuvering. To design a robot fish and benefit the characteristics and abilities of a live fish, using its real geometry and kinematics in the robot is vital. Therefore, simulations are essential to better exploiting the fish behavior, which can obtain useful consequences by using computational fluid dynamics. In this thesis, first the kinematics of sharks is investigated. Then, investigations are accomplished by utilizing an unsteady finite... 

The purpose of this study is to investigate the resilience of the urban water supply network against earthquakes, A hydraulic analysis of the water supply network was implemented in Rtx software to study the effective parameters in the resilience of the network. Rtx software is a tool for assessing the reliability and resilience of communities and infrastructure to natural hazards by taking into account related uncertainties. The water supply network, like other networks, is affected by earthquakes. The seismic damage varies depending on the vulnerability of the network, the intensity of the earthquake, the focal depth, and the distance from the epicenter. Thus, it reduces the ability of the... 

In this thesis the perovskite catalyst of La0.7Sr0.3FeO3 with different percentages of kaolin and alumina boehmite as binders was synthesized to be used in the chemical looping partial oxidation process. To determine the best catalyst in terms of resistance against attrition, an attrition test was performed in a jet cup testing rig. The best catalyst in terms of resistance against attrition was perovskite catalyst 60% weight,25% weight kaolin and 15% weight alumina beohmite. Cold test of fluidized bed of the optimum catalyst in terms of resistance against attrition performed and minimum fluidization velocity, terminal velocity, flow regime type and Geldart type was obtained. The synthesized... 

Fault detection and diagnostics of rotating machinery are considered one of the most important issues. Propulsion system, power generator motor, shaft couplings and transmissions system prepare trust necessary to move the high speed craft. Vibration measurement, control and obtain the critical velocity and dynamic forces on bearings and joints is one of the most important issues in this case. In this project dynamic modeling of surface piercing system was analyzed which this system has ability to change trim and steering angles by hydraulic cylinder. Dynamic modeling regard to the driving forces of surface piercing propeller modes of in different operation state is performed. At the end,... 

The motion of gas bubbles in the bulk of a fluid can be one of the most widely used industrial phenomena. Various factors such as the size and shape of the bubbles, the physical properties of the liquid phase such as density and viscosity, method of gas injection, the presence of impurities, etc. affect this phenomenon. Some of the most important industrial processes that include the motion of bubbles in the liquid phase bulk are gas adsorption, distillation and froth flotation. According to the results of previous studies, the hydrodynamics of bubble motion in the bulk of a liquid fluid depends on the presence of impurities such as surfactants, proteins and colloidal particles. In many... 

In this research, first, the performance map and surge line of 46M6 and 46MB8 multi-stage radial compressors, which have 6 and 8 stages, respectively, have been estimated and invarianted. Invarianting the performance map makes the performance curve and surge line of the compressor, unchanged from input conditions, including molecular weight, which is very important for control systems. Then, the hydrodynamic circuit of Compressor System C-3002 of Nouri Petrochemical Company was modeled according to the characteristics of its components by solving equations in MATLAB software. main working condition of the hydrodynamic circuit is close to Start of Life operating condition which has a... 

This study presents an integrated two-dimensional numerical framework for simulating rainfall-induced landslides from instability initiation to post-failure flow. The discrete element method (DEM) is used to establish a rheological model that relates the apparent viscosity of a granular sand to shear rate, normal stress, and water saturation. A theoretical model is developed to determine water distribution and water-induced forces between particles for different saturations. The resulting forces are embedded in a 3D shear cell as a numerical rheometer and a wet sand is sheared between two walls. A power law rheological model is obtained as a function of inertia number and saturation. It was... 

Today, to reduce the effects of greenhouse gases on the earth, as well as reduce dependence on fossil fuels and other non-renewable sources, the international community is moving towards greater use of renewable energy. The oscillating water column device as a wave energy converter system has the ability to use and absorb energy within the waves through a chamber consisting an air and a water column. This system has the ability to move the turbine installed on the valve by expanding and compressing the air passing through the valve. Oscillating water column systems have different categories, and this high diversity makes the choice of this wave energy converter closely related to the... 

One of the biggest problems in improving the performance of submersible propellers is the acoustic standard in conventional propellers. Recently, new solutions in propellers geometry have been used to reduce non-cavitation noise. Designing CRP licenses is one of these methods. This research includes numerical analysis. Numerical analysis in this research solves RANS equations of flow and extraction of hydrodynamic parameters and impeller noise in Ansys software. The results of numerical hydrodynamic solution are validated by laboratory results.DTMB 4119 three-blade propeller is used for hydrodynamic and hydroacoustic validation. The solution of Lighthill equations by FW-H method is... 

A 2D simulation has been carried out to study the effect of magnetic field on heat transfer and pressure drop of nanofluid flowing through a pipe filled with porous medium. The nanofluid flow is modeled as a single-phase flow, and Darcy–Brinkman–Forchheimer equation is employed to model fluid flow in porous media. A constant uniform heat flux was imposed on the walls of the cylinder, and the values of Darcy number, Hartmann number, and volume fraction of the nanoparticles were selected as 0.1, 200, and 0.2, respectively. Effects of parameters such as Reynolds number, the material of the porous medium (conductivity and porosity), and material of nanofluids have been investigated in the... 

Liquid-liquid extraction is one of the common chemical processes in the industry which its application is increasing day by day. Taking trend of increase of energy resources, chemical materials and industrial system into account, the necessity use of least energy consumption and material for achieving highest output and purity of products in different industries is attracted researches and industerialists.In this research we have studied the effect of presence of nano particles on both disperses and continuous liquids phases on hydrodynamic of deoplets specially their investigated system in this project was watter, toluene and acetone, and chosen nanoparticles wer carbon nanotubes and TiO2....