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Numerical Analysis of Underwater and Within Air Sound Generation by using Carbon Nanotube
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
Carbon nanotubes have special thermodynamic properties which makes suitable as a thermo-acoustic sound source. Recently it is shown that by using these nanotubes it is possible to generate strog sound waves in air or water. Experimental analysis of phenomenon can be complicated and expensive. Hence this fact, in this study using molecular dynamic simulation, numerical analysis of sound generation with CNTs in air and water is discussed. For this purpose, the required structue of the system is generated and it has reaced equilibrium. This process has been done for 6 different CNT and for each CNT there are 5 different distances between them. Althogether, 30 different cases has is used for...
Investigation of Optical Bistability in Quantum Dot and Erbium Doped Fiber Ring Resonator
, M.Sc. Thesis Sharif University of Technology ; Bahrampour, Alireza (Supervisor)
Abstract
Optical bistability is one of the most important results of nonlinear optics. The term optical bistability refers to the situation in which two different output intensities are possible for a given input intensity. Interest in optical bistability stems from its potential usefulness as a switch for use in optical communication and in optical computing. Optical bistability is resulted by nonlinear phenomena such as kerr effect, two photon absorption and saturable absorber. In this thesis, we study the optical bistability in a double-coupler ring resonator, in which the right half of ring is made of an erbium doped fiber amplifier for compensating the loss by the gain of EDFA, and the left half...
Molecular dynamics study of friction reduction of two-phase flows on surfaces using 3d hierarchical nanostructures
, Article Journal of Physical Chemistry C ; 2019 ; 19327447 (ISSN) ; Moosavi, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
American Chemical Society
2019
Abstract
The use of superhydrophobic surfaces is one the most promising methods for reducing the friction and increasing the flow rate in fluid transfer systems. Because in such systems the surface structure plays a key role, in this study, we explore the performance of the hierarchical nanostructures. These nanostructures are inspired by the superhydrophobic surface of the lotus leaf. We consider a flow between two walls with hierarchical nanostructures and simulate the system via the molecular dynamics method. The size of the nanostructures and the distance between them have been studied to find whether a design with a maximum flow rate exists. The nanostructures have two parts, a bigger part on...
Molecular dynamics study of friction reduction of two-phase flows on surfaces using 3d hierarchical nanostructures
, Article Journal of Physical Chemistry C ; 2019 ; 19327447 (ISSN) ; Moosavi, A ; Hannani, S. K ; Sharif University of Technology
American Chemical Society
2019
Abstract
The use of superhydrophobic surfaces is one the most promising methods for reducing the friction and increasing the flow rate in fluid transfer systems. Because in such systems the surface structure plays a key role, in this study, we explore the performance of the hierarchical nanostructures. These nanostructures are inspired by the superhydrophobic surface of the lotus leaf. We consider a flow between two walls with hierarchical nanostructures and simulate the system via the molecular dynamics method. The size of the nanostructures and the distance between them have been studied to find whether a design with a maximum flow rate exists. The nanostructures have two parts, a bigger part on...
Friction reduction in a nanochannel with grafted poly(N-isopropylacrylamide) oligomers: A molecular dynamics study
, Article Physics of Fluids ; Volume 33, Issue 5 , 2021 ; 10706631 (ISSN) ; Moosavi, A ; Hannani, S. K ; Sharif University of Technology
American Institute of Physics Inc
2021
Abstract
Superhydrophobic surfaces have been used for reducing friction in micro- and nanochannels. In the present work, water flow between two carbon walls with nanostructures made of poly(N-isopropylacrylamide) via the molecular dynamics method has been studied. The structure of this polymer can change based on the temperature of the environment, so that by increasing the temperature the structure becomes hydrophobic. This property has been studied and the effect of multiple factors on the slip length is presented. The effects of the number of monomers in the polymer, the distance between the polymers, and the temperature on the flow field are investigated. The results reveal that the slip length...
Friction reduction in grafted carbon nanochannels by applying an electric field
, Article Computational Materials Science ; Volume 213 , 2022 ; 09270256 (ISSN) ; Moosavi, A ; Hannani, S. K ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Water can be pumped in nanochannels by limiting it between the surfaces with different hydrophobicities and exerting a spinning electric field. The asymmetrical hydrophobicity combined with the spinning electric field and the fact that the water molecules have a dipole moment create a situation in which the angular momentum of water molecules is transformed into a linear momentum and the water is pumped into the nanochannel. The hydrophobicity of the surfaces can be manipulated by using nanostructures to reduce friction. In this study, two types of nanostructures have been used which are hierarchical nanostructures and polymer nanostructures made of Poly(N-isopropylacrylamide). The walls of...
Thermo acoustic study of carbon nanotubes in near and far field: Theory, simulation, and experiment
, Article Journal of Applied Physics ; Volume 117, Issue 9 , 2015 ; 00218979 (ISSN) ; Moosavi, A ; Huynh, C ; Saleki, O ; Sharif University of Technology
American Institute of Physics Inc
2015
Abstract
Carbon nanotube webs exhibit interesting properties when used as thermo-acoustic projectors. This work studies thermo-acoustic effect of these sound sources both in near and far field regions. Based on two alternative forms of the energy equation, we have developed a straightforward formula for calculation of pressure field, which is consistent with experimental data in far field. Also we have solved full 3-D governing equations using numerical methods. Our three-dimensional simulation and experimental data show pressure waves are highly affected by dimensions of sound sources in near field due to interference effects. However, generation of sound waves in far field is independent of...
Numerical study on the oscillation of a transient bubble near a confined free surface for droplet generation
, Article Theoretical and Computational Fluid Dynamics ; Vol. 28, issue. 4 , 2014 , p. 449-472 ; Shervani-Tabar, M.T ; Taeibi-Rahni, M ; Dadvand, A ; Sharif University of Technology
2014
Abstract
In the present work, the oscillation of a spark-created bubble near a confined water-air interface and the ensuing droplet generation and ejection are studied numerically using the boundary element method. The interface is accorded by the top opening of either one of the following symmetrical configurations, which are distinguished by the value of angle between their vertical symmetry axis and lateral wall (i.e., θ): (i) a centrally perforated horizontal flat plate (θ = 90°) and (ii) vertically placed cylinder (θ = 0°), nozzle (θ > 0°) and diffuser (θ < 0°). Furthermore, the influences of the effective parameters such as the strength parameter (i.e., the intensity of local energy input), the...
Molecular Dynamic Simulation of Friction Reduction in Two-Phase Flows with Nanostructures and Study of the effect of Electric Field
, M.Sc. Thesis Sharif University of Technology ; Kazemzadeh Hannani, Siamak (Supervisor) ; Moosavi, Ali (Supervisor)
Abstract
The use of superhydrophobic surfaces is one the most promising methods for reducing the friction and increasing the flow rate in fluid transfer systems. Since in such systems the surface structure plays a key role, in the first part of this study, the performance of the hierarchical nanostructures is explored. These nanostructures are inspired by the superhydrophobic surface of the lotus leaf. The flow is considered between two walls with hierarchical nanostructures and simulate the system via the molecular dynamics (MD) method. The size of the nanostructures and the distance between them have been studied to find whether a design with maximum flow rate exists. The nanostructures have two...
Interaction of two spark-generated bubbles near a confined free surface
, Article Theoretical and Computational Fluid Dynamics ; Volume 30, Issue 3 , 2016 , Pages 185-209 ; 09354964 (ISSN) ; Shervani Tabar, M. T ; Taeibi Rahni, M ; Dadvand, A ; Sharif University of Technology
Springer New York LLC
2016
Abstract
In this paper, the oscillation of two spark-generated bubbles placed on a vertical column in close proximity to a confined free surface is considered. The confined free surface is accorded by the top opening of different configurations. These configurations include (i) a centrally perforated horizontal flat plate (θ = 90∘), (ii) vertically placed cylinder (θ = 0∘) and (iii) nozzle (θ > 0∘). The main objective of the present work is to study the effects of key parameters such as the nozzle geometry, the locations of the energy input (i.e., initial position of the bubbles with respect to each other and relative to the free surface) on the dynamics of the two bubbles and the free surface. It...