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mirhashemi--soroosh
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Nonlinear dynamics of a nearly taut cable subjected to parametric aerodynamic excitation due to a typical pulsatile wind flow
, Article International Journal of Engineering Science ; Volume 188 , 2023 ; 00207225 (ISSN) ; Haddadpour, H ; Sharif University of Technology
Elsevier Ltd
2023
Abstract
In this study, the dynamic response of a nearly taut nonlinear cable that is actuated by a pulsatile wind flow is investigated for the sake of obtaining the regime of motion and bifurcations of the system. The aerodynamic model is a general modelling of wind excitation including nonlinear cubic terms. Since realistic wind blows frequently and is not invariant, the velocity of the time-variant flow is considered to be a typical combination of a constant and a small harmonic perturbation. The equation of motion of the system has a simple form and is discretized by single-mode Galerkin method and by employing the method of multiple scales (MMS) the parametric resonance of the system is...
Design of an Optimized Gas-liquid Auxiliary Heat Exchanger to Improve Performance of a Rankin Cycle Using CFD
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
The enviromental wind would cause serious drop in the performance of Heller cooling systems in thermal powerplants working on Rankin cycle. Therfore, it is necessary to consider the wind velocity in the design of such cooling tower systems. We use the computational fluid dynamics (CFD) and simulate the 3D buoyant flow passing through and over a heel cooling tower. We consider three different wind veocities of 0, 5 and 10 m/s in our simulations. In order to consider the low efficiency of the cooling system in efficiency drop of the main rankin cycle, we need to consider actual power generated by the powerplant generator, which is directly affected by the turbine back pressure. To connect the...
Dynamics, Stability, and Aero-servo-elasticity of Airships with Flexible Body and Fins
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor)
Abstract
In this research, the dynamics, aero-elasticity, and control of an airship with a flexible body hull and fins are investigated. The flexible airship is modeled as a combination of several beams with specific boundary conditions. So that the dynamics and vibration of its body hull and fins can be taken into account regarding the aerodynamic, gravity, aerostatic, and control input forces. The governing equations of motion of the system are derived by using the velocity of an arbitrary point on each component and integration over the component and substituting them into the Euler-Lagrange equations in a body frame. Afterward, the added mass acting on the hull is calculated. Then, a perturbation...
Nonlinear dynamics and stability analysis of a parametrically excited CNT-reinforced MRE viscoelastic cantilever beam
, Article Smart Materials and Structures ; Volume 27, Issue 10 , 2018 ; 09641726 (ISSN) ; Jalali, A ; Sharif University of Technology
2018
Abstract
This paper investigates the dynamic response of a clamped-free CNT-reinforced-MRE beam which is actuated by the combination of a constant and a harmonic time-dependent magnetic field. Using Hamilton's principle, the equation of motion has been obtained and discretized using the Galerkin method. This procedure transforms the governing PDE equation of motion into a nonlinear ODE equation in the form of the nonlinear Mathieu equation with cubic damping. Then, the method of multiple scales is employed to obtain the dynamic response of the system. Furthermore, a stability analysis is also performed and the effects of a magnetic field on the dynamic response and stability of the system is...
Dynamics of a harmonically excited nonlinear pipe conveying fluid equipped with a local nonlinear energy sink
, Article Communications in Nonlinear Science and Numerical Simulation ; Volume 118 , 2023 ; 10075704 (ISSN) ; Saeidiha, M ; Ahmadi, H ; Sharif University of Technology
Elsevier B.V
2023
Abstract
When the magnitude of the lateral elastic deformation of a pipe over its length is more prominent than in a linear situation, it is necessary to use nonlinear terms to reduce the gap between the mathematical model and the real system. Also, the importance of nonlinear terms is more considerable when a pipe conveying fluid is studied. Since the passive vibration control of pipes is of great significance, one may employ a nonlinear energy sink (NES) as the control configuration attached to the pipe. Hence, in this study, the dynamics of a harmonically excited nonlinear pipe conveying fluid attached to a local NES is investigated. The boundary conditions are assumed doubly clamped. The two...
Predicting crack initiation of solder joints with varying sizes under bending
, Article Journal of Electronic Materials ; 2019 ; 03615235 (ISSN) ; Farrahi, G. H ; Nourani, A ; Soroosh, F ; Sharif University of Technology
Springer New York LLC
2019
Abstract
The critical strain energy release rate for crack initiation, J ci , was measured under mode I loading for SAC305 solder joints between two copper substrates. Fracture tests were performed using double cantilever beam specimens at a strain rate of 0.03 s −1 . Different bond-line widths (i.e., joint size in the out-of-plane dimension) and thicknesses, were examined. The fracture force per unit width and J ci (the average value of four J-integral contours encircling the crack tip) were relatively insensitive to the width of the joint ranging from 8 mm to 21 mm. Variations in bond-line thickness (i.e., 150 μm, 250 μm and 450 μm) also had an insignificant influence on the fracture energy of...
Predicting crack initiation of solder joints with varying sizes under bending
, Article Journal of Electronic Materials ; 2019 ; 03615235 (ISSN) ; Farrahi, G. H ; Nourani, A ; Soroosh, F ; Sharif University of Technology
Springer New York LLC
2019
Abstract
The critical strain energy release rate for crack initiation, J ci , was measured under mode I loading for SAC305 solder joints between two copper substrates. Fracture tests were performed using double cantilever beam specimens at a strain rate of 0.03 s −1 . Different bond-line widths (i.e., joint size in the out-of-plane dimension) and thicknesses, were examined. The fracture force per unit width and J ci (the average value of four J-integral contours encircling the crack tip) were relatively insensitive to the width of the joint ranging from 8 mm to 21 mm. Variations in bond-line thickness (i.e., 150 μm, 250 μm and 450 μm) also had an insignificant influence on the fracture energy of...
Details study of ambient wind effect on heat dissipation capacity of thermal-powerplant dry cooling-towers
, Article American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM ; Volume 1A , August 3–7 , 2014 , pp. V01AT03A017 ; ISSN: 08888116 ; ISBN: 9780791846216 ; Behrouzifar, A ; Mirhashemi, A ; Salemkar, H ; Schneider, G. E ; Sharif University of Technology
2014
Abstract
Thermal powerplants report a reduction in their dry cooling tower performances due to surrounding wind drafts. Therefore, it is very important to consider the influence of wind velocity in cooling tower design; especially in geographical points with high wind conditions. In this regard, we use the computational fluid dynamics (CFD) tool and simulate a dry cooling tower in different wind velocities of 0, 5 and 10 m/s. To extend our calculations; we also consider the temperature variation of circulating water through the tower heat exchanger or deltas one-by-one. We show that some heat exchangers around the tower cannot reduce the circulating water temperature sufficiently. This causes an...
Same Partners, New Routes: Evidence on the Effect of Sanctions on Iran’s Trade Patterns
, M.Sc. Thesis Sharif University of Technology ; Ansari, Mahdi (Supervisor) ; Madanizadeh, Ali (Supervisor) ; Haidar, Jamal Ibrahim (Co-Supervisor)
Abstract
Trade wars and economic sanctions have become increasingly common tools of economic policy, prompting targeted countries to seek alternative trade routes. For instance, in response to tariffs, China has redirected exports to the United States through intermediary countries. This issue is also relevant in Russia’s confrontation with Western sanctions. In this study, we leverage Iran’s long-term experience with sanctions to examine whether trade re-routing occurs, how quickly it emerges, and whether it persists over time. Analyzing trade data from 2002 to 2023, we find that by the end of this period, 70% of Iran’s imports originated from the UAE, China, and Türkiye, whereas two decades...