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Experimental Study of Hydraulic Characteristics of Perforated Pipes in Submerged Area
, M.Sc. Thesis Sharif University of Technology ; Jamali, Mir Mosaddegh (Supervisor)
Abstract
In small settling tanks, the sludges can be removed using perforated pipes. In this method the pipe is placed in the depth of a fluid and the lateral inflow through perforations lead to the outlet. Since there are few researches about hydraulic characteristic of perforated pipes, this research will investigate the hyadraulic characteristic of these pipes experimentally. One of the main objectives of these pipes is to use the entire lenghte of the pipe and also provide the uniform distribution of inflow. In the past studies, it was found out that inflow mostly comes through downstream perforations. The objective of this research is to find the distribution of discharge along the perporated...
Experimental study of liquid jets injected in crossflow
, Article Experimental Thermal and Fluid Science ; Volume 115 , 2020 ; Kebriaee, A ; Sharif University of Technology
Elsevier Inc
2020
Abstract
In this paper, we studied the behavior of liquid sheet and jet injection into a low-speed crossflow. Characteristics of primary breakup in a liquid sheet and jet are investigated for circular and rectangular orifices. Effect of dimensionless numbers on primary breakup regimes including jet trajectory, length, height, breakup, and spray characteristics are surveyed by the shadowgraphy technique at ambient pressure and temperature. Tests were performed in the range of 0.8–16.57 for the Weber number, 5–250 for the momentum flux ratio, and 380–1850 for the Reynolds number. This comprehensive study on rectangular jets in crossflow leads to introduce the transition regions of the primary...
Effects of Heart Dynamic Motion on Blood Hemodynamics and LDL Accumulation in Coronary Bifurcation
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor)
Abstract
In this thesis, the effect of heart dynamic motion and pulsatile inflow on blood hemodynamics and LDL permeation into the arterial wall in a 3-D coronary artery bifurcation was investigated. To determine the effect of each factor alone and simultaneous effect of both factors i.e. heart dynamic motion and pulsatile inflow, flow simulations were performed in four cases i.e. steady-static, steady-dynamic, pulsatile-static, and pulsatile-dynamic. The results of flow simulations showed that dynamic geometry and pulsatile inflow have considerable impact on temporal variations of wall shear stress (WSS), even though the effect of pulsatile inflow on WSS variation dominates over the effect of...
Experimental Study of Liquid Sheet Breakup in Cross Flow
, Ph.D. Dissertation Sharif University of Technology ; Kebriaee, Azadeh (Supervisor)
Abstract
Injecting liquid fuel into the cross flow of air provides high penetration of the liquid, rapid mixing with air, and increased efficiency. This method has widespread applications in the propulsion systems of gas turbines, scramjets, turbine blade cooling, and fuel injection for engine afterburners. One of the design strategies for future aircraft engines is to reduce pollutants using fuel spray into the cross flow instead of direct jet fuel injection and using renewable energy sources. The applications of cross flows include injecting fluid through rotating pressure injectors in exhaust flows, injecting fluid through pressure-rotating injectors in radial injectors, and using slinger...
Fishbone pattern formation due to asymmetries in colliding low-velocity jets
, Article Atomization and Sprays ; Volume 28, Issue 8 , 2018 , Pages 751-762 ; 10445110 (ISSN) ; Kashanj, S ; Olyaei, G ; Sharif University of Technology
Begell House Inc
2018
Abstract
Here, we experimentally investigated the effects of skewness and velocity difference of two Newtonian colliding jets on the formation of a special oscillating liquid sheet pattern with periodic fragmentation, called fishbone, for four liquid sheet regimes known as the triple chain, double chain, close rim, and open rim. We expressed the ranges of the skewness and the velocity difference, where the fishbone pattern was formed for every four regimes. The formation of this special pattern was attributed to the instability of the liquid rim in the past studies. We qualitatively studied the upward and downward directions of the rims branched from the liquid sheet. Besides, the size variations of...
Determination of the Minimum Fluidization Velocity of an Object Immersed in a Bubbling Fluidized Bed through the CFD-DEM Simulations
, M.Sc. Thesis Sharif University of Technology ; Fotovat, Farzam (Supervisor)
Abstract
Due to the unique advantages of fluidized beds for solid mixing and heat transfer, they are widely used for the thermal processing of solid fuel particles. In practice, such systems are composed of non-conventional fuel particles such as coal or biomass, which are completely different in shape, size, and density from the bed material such as sand. In such systems, correct understanding of the main fluidization parameters such as the minimum fluidization velocity (Umf) of the bed components plays a key role in the successful design and control of the system. However, the onset of fluidization of irregular particles is not clear as it may vary depending on the physical properties of the...
Modification of carbohydrate polymers via grafting in air. 1. Ceric-Induced synthesis of starch-g-polyacrylonitrile in presence and absence of oxygen [electronic resource]
, Article Starch - Starke ; Volume 54, Issue 3-4, pages 140–147, April 2002 ; Zohurian Mehr, Mohammad J
Abstract
Monomer grafting, a unique technique for polysaccharide modification, is always performed under inert (e.g., N2) atmosphere. This work is the first report related to evaluating the possibility and efficiency of the grafting of acrylonitrile (AN) onto starch in presence of oxygen. Thus, corn starch (in both granular and gelatinized states) as well as soluble starch were grafted by AN using a ceric-carbohydrate redox initiating system. Graft copolymerizations were performed under nitrogen, air, and oxygen atmospheres at similar conditions. Grafting occurrence was verified using chemical and spectral proofs. The polymerization mechanism and kinetics were investigated by recording the...
Modification of carbohydrate polymers via grafting in Air. 2. Ceric-Initiated graft copolymerization of acrylonitrile onto natural and modified polysaccharides [electronic resource]
, Article Starch - Stärke ; Volume 54, Issue 10, pages 482–488, October 2002 ; Zohuriaan-Mehr, Mohammad J
Abstract
Acrylonitrile (AN) was grafted onto various natural and modified polysaccharides (i.e., gum arabic, gum tragacanth, xanthan gum, sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose) by using ceric-carbohydrate redox initiating system. After overcoming practical problems, mainly from the high viscosity of the aqueous solutions of the different substrates, the graft copolymerization reactions were run either in air or in N2 atmosphere under similar conditions. Grafting was confirmed using chemical and spectral (FTIR) proofs. The reactions were kinetically investigated using semi-empirical expressions and time-temperature profiles. An anomalous...
Modeling of in Plane Behavior of Retrofitted Adobe Walls with Finite Element Method under Cyclic Loading
, M.Sc. Thesis Sharif University of Technology ; Bakhshi, Ali (Supervisor) ; Ghannad, Mohammad Ali (Co-Advisor)
Abstract
Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by...
Silica chloride/wet SiO2 as a novel heterogeneous system for the deprotection of acetals under mild conditions [electronic resource]
, Article Phosphorus, Sulfur, and Silicon and the Related Elements ; Volume 178:2667-2670, Issue 12, 2003 ; Pourjavadi, Ali ; Zolfigol, Mohammad Ali ; Bamoniri, Abdolhamid
Abstract
A combination of silica chloride and wet SiO2 was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under mild and heterogeneous condition
Distributed Fault-tolerant Computation for Massive Data
, M.Sc. Thesis Sharif University of Technology ; Maddah-Ali, Mohammad Ali (Supervisor)
Abstract
In this thesis we consider the problem of distributed computation by many processors.We mainly concentrate on matrix multiplication problem in this thesis because of its importance. A distributed system consists of N worker processors and one master processor. The master processor should distribute the computation between workers and after computation in each of them, collect the results. In this thesis, we are going to mitigate the effect of straggler processors by using coding methods. Straggler processors can cause delays in the computation time.In this thesis, we firstly introduce a method to multiply any number of matrices in each other. The proposed method occurred in one shot without...
Numerical Modeling of Fluid Flow in Cracked Porous Media using Phase-Field Approach
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
The objective of this research is to investigate fluid flow in cracked porous media. Fluid, mass, and heat transfer in porous and cracked porous media, particularly in subsurface environments characterized by complexity and uncertainty—such as hydraulic fracturing, lowـpressure groundwater flow, and more—are of great importance in the oil and geothermal energy industries. The problem domain consists of three main sections: the saturated porous medium, the crack or channel within this porous medium, and the boundary layer between the crack and the adjacent environment. The phase field method is utilized in this study to model these discontinuities. Phase field models are similar to...
Incomplete Reduction of Iron Ore in a Fluidized Bed Reactor
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
The main goal of current investigation was partial reduction of Fe2O3 available in Hematite-rich ore to Magnetite by Fludization Bed method. The reductive gas, CO, was produced by incomplete combustion of Acetylene and Airmixed in inappropriate ratio. X-Ray Diffraction and X-Ray Florescence analyses were implemented in order to conducting qualitative analysis of present phases before and after reduction of the ore. Quantitative analysis of the same phases was also conducted by Titration. The latter analysis revealed the precise magnitude of available iron in each of the oxide containing phases. The chemical composition of the reactor gas was also determined before and after reduction...
Sequential Competitive Facility Location In Continuous Geometric Space
, M.Sc. Thesis Sharif University of Technology ; Abam, Mohammad Ali (Supervisor)
Abstract
Abstract The problem of competetive facility location can be defined as follows: There are a number of customers in the form of points in space, and two players arrange a number of facilities in the form of points in space, given some limitations, respectively. Each customer’s connection to each facility has a cost for the customer and an advantage for the facility, and each customer wants to be connected to at most one of the facilities which has the lowest cost for him. The goal is to find the strategy of placing the facilities and determining the cost which the facility receives from the customer, in such a way that the player’s profit is maximised.In this thesis, we first sought to...
Distributed Verifiable Computing: Algorithms and Analysis
, M.Sc. Thesis Sharif University of Technology ; Maddah Ali, Mohammad Ali (Supervisor)
Abstract
Zero knowledge proofs allow a person (prover) to convince another person (verifier) that he has performed a specific computation on a secret data correctly, and has obtained a true answer, without having to disclose the secret data. QAP (Quadratic Arithmetic Program) based zkSNARKs (zero knowledge Succinct Non-interactive Argument of Knowledge) are a type of zero knowledge proof. They have several properties that make them attractive in practice, e.g. verifier's work is very easy. So they are used in many areas such as Blockchain and cloud computing. But yet prover's work in QAP based zkSNARKs is heavy, therefore, it may not be possible for a prover with limited processing resource to run...
Privacy Preserving Communication Schemes for Light Clients in Blockchain Networks: Algorithms and Analysis
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor) ; Maddah Ali, Mohammad Ali (Co-Supervisor)
Abstract
Lightweight clients are a type of blockchain users who do not store all the blocks in the blockchain due to limited resources. These users store only a small part of each block and when needed, request transactions from full nodes that store the entire blockchain. These users have no role in block validation and only want to receive transactions related to their addresses with proof of the inclusion in the block from full nodes.Since light clients rely on full nodes for receiving transactions, their privacy against full nodes is important. The current implementation of Bitcoin uses Bloom filters for privacy, but this offers very little privacy to the users.In this thesis, we study the...
A numerical modeling of thermal management of high CPV arrays using spray cooling
, Article Applied Thermal Engineering ; Volume 230 , 2023 ; 13594311 (ISSN) ; Shen, X ; Morad, M. R ; Olyaei, G ; Sharif University of Technology
Elsevier Ltd
2023
Abstract
Liquid cooling is an efficient way of thermal management for high CPV cells, increasing the system performance by reducing cell's temperature. Thermal management complexity rises upon using an array of cells while the system becomes sizeable. The present numerical simulations follow a single cell study to investigate spray cooling for high CPV arrays with minimum number of injecting nozzles. The idea is to cool the cells by the liquid film formed on the thermal paste surface. Cooling the whole surface by the help of the liquid film decreases the number of nozzles to less than the number of cells. Both mass flow rate and pumping power are reduced, improving the system efficiency and lowering...
Coded Computing for Distributed Machine Learning
, Ph.D. Dissertation Sharif University of Technology ; Maddah Ali, Mohammad Ali (Supervisor)
Abstract
Nowadays, we are forced to use distributed computing due to the growth of data, the challenge of storing and processing it, as well as the emergence of new problems in machine learning and the complexity of the models. In distributed computing, the computation is per- formed by a distributed system consisting of several worker nodes such that, the main task is divided into several smaller tasks and assigned to each worker node. Then, different worker nodes will cooperate to accomplish the main task. Although distributed systems are efficient in solving problems and dealing with the mentioned challenges, they are vulnerable to the presence of stragglers, adversarial worker nodes, high...
Designing Online Algorithm for Admission Control in Payment Channel Networks
, M.Sc. Thesis Sharif University of Technology ; Maddah Ali, Mohammad Ali (Supervisor)
Abstract
Payment channel networks (PCNs) are a promising technology to improve the scalability of cryptocurrencies. Users can send instant and almost free transactions via payment channel networks and, at the same time, enjoy the security guarantees of Blockchains. In order to open a mutual payment channel, two users should send a ``channel creation" transaction to the underlying Blockchain. Through this transaction, two parties deposit some money on the Blockchain. This money, which we call the channel's capacity, can be used to send off-chain transactions between the two users. After the channel creation, the channel-holders can send each other off-chain transactions by forwarding the money back...
Power System Load Frequency Control Considering Renewable Energy Sources
, M.Sc. Thesis Sharif University of Technology ; Ranjbar, Ali Mohammad (Supervisor)
Abstract
Power system frequency regulation entitled load frequency control (LFC) has been one of the important control problems in electric power system design and operation. Off-normal frequency can directly impact on power system operation and system reliability. A large frequency deviation can damage equipment, degrade load performance, cause the transmission lines to be overloaded and can interfere with system protection schemes, ultimately leading to an unstable condition for the power system . On the other hand, the increasing need for electrical energy in the 21st century, as well as limited fossil fuel reserves and the increasing concerns with environmental issues for the reduction of carbon...