@article { author = {Mishra, D.R.}, title = {Experimental evaluation of shape factor of axis-symmetric sunken structures}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2831-2837}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.50181.1559}, abstract = {This paper presents the dependence of a shape factor for the fully sunken axis symmetrical structures (viz. cubical, square prismatic, pyramidal, and cylindrical) corresponding to the depth and their orientation. Experimental evaluations of the shape factor on reduce scale models are carried out in laboratory using thermal simulation method for different sets of conditions. The method has been used to determine shape factor, which can be used to determine heat loss from ground to structure or structure to groud fully sunken with the different orientation. Maximum and minimum value of shape factor for set-I and II condition are recoded as 90.18 and 9.93 respectively. In set –III it will varies from 16.49 to 35.28. At D/L=2 shape factor of set-VI leads by 17.26% as compared to set VII. Where as set- IX leads by 33.47% as compaired to set VIII. It would help for designing building structure of fully buried nature for creating thermal comfort.}, keywords = {Thermal simulation,Heat Transfer,buried structure}, url = {https://scientiairanica.sharif.edu/article_21471.html}, eprint = {https://scientiairanica.sharif.edu/article_21471_87910d5fa1d4023d6185b7a94350e874.pdf} } @article { author = {DAS, A. and Patel, S.K. and Biswal, B.B. and Das, S.R.}, title = {Performance evaluation of aluminium oxide nano particles in cutting fluid with minimum quantity lubrication technique in turning of hardened AISI 4340 alloy steel}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2838-2852}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.51223.2069}, abstract = {The current research comprises various machinability aspects of 4340 hardened alloy steel which are scrutinized with in context of improvements in main cutting force, tool flank wear, crater wear, surface roughness, microhardness, machined surface morphology, chip morphology, chip reduction coefficient and apparent coefficient of friction under three different cutting fluid applications i.e. compressed air, water soluble coolant based MQL, and nanofluid (using eco-friendly radiator coolant as the base fluid and Al2O3 as the nanoparticle) based MQL technique using cermet cutting inserts and a comparative assessment was performed to select which fluid performed better in terms of various machining attributes among three cutting fluids. The minimum quantity lubrication technique was used in which a smaller volume of coolant sprinkled at high pressure. This method is found as the most effective alternative to minimize health risks and machining costs, which is quite high in other setups. The test specimen was machined at three different cutting speeds i.e. 100,120 and 140m/min along with two machining parameters i.e. feed and depth of cut were kept constant respectively at 0.2mm/rev and 0.4mm. Outcomes made a conclusion that Al2O3 enriched ecofriendly nano-coolant outperformed both compressed air and water soluble coolant in terms of every machinability aspects.}, keywords = {AISI 4340,Cermet inserts,MQL,Nano Fluid,Machinability}, url = {https://scientiairanica.sharif.edu/article_21514.html}, eprint = {https://scientiairanica.sharif.edu/article_21514_bfe2f7d424130d3a3a55eb86024054e8.pdf} } @article { author = {Tunc, H. and Sari, M.}, title = {Simulations of nonlinear advection-diffusion models through various finite element techniques}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2853-2870}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.51513.2228}, abstract = {In this study, the Burgers equation is analyzed in both numerically and mathematically by considering various finite element based techniques including Galerkin, Taylor-Galerkin and collocation methods for spatial variation of the equation. The obtained time dependent ordinary differential equation system is approximately solved by α-family of time approximation. All these methods are theoretically explained using cubic B-spline basis and weight functions for a strong form of the model equation. Von Neumann matrix stability analysis is performed for each of these methods and stability criteria are determined in terms of the problem parameters. Some challenging examples of the Burgers equation are numerically solved and compared with the literature and exact solutions. Also, the proposed techniques have been compared with each other in terms of their advantageous and disadvantageous depending on the problem types. The more advantageous method of the three, comparison to other two, has been found out for the special cases of the present problem in detail.}, keywords = {Finite Element Method,α-family of approximation,advection-diffusion model,Burgers equation,Taylor-Galerkin method,Collocation method}, url = {https://scientiairanica.sharif.edu/article_21603.html}, eprint = {https://scientiairanica.sharif.edu/article_21603_4e1610338deeedc6b7fd0e92fbc1d54c.pdf} } @article { author = {Rahmaninia, R. and Amani, E. and Abbassi, A.}, title = {Computational optimization of a UFAD system using large eddy simulation}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2871-2888}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.51896.2413}, abstract = {In the present study, the Large Eddy Simulation (LES) turbulence closure is implemented, for the first time, to the best of our knowledge, to investigate the air conditioning system in a large space. The results of LES simulations are validated against experimental measurements and the model is used to study the effect of different design variables, including the Air Changes per Hour (ACH), supply temperature, and return air vent height, on design objectives, such as local and global thermal comfort indexes and the energy saving parameter, via a systematic multi-objective optimization approach. The sensitivity analysis shows that the global and local thermal comfort indexes are most sensitive to the air supply temperature while the energy saving is sensitive to ACH and the supply temperature to the same extent. In addition, the return air vent height affects the energy saving more than the other objectives. Finally, with the best design proposed by the multi-objective optimization, an energy saving of 22.9% is achievable while keeping the thermal comfort indexes within the allowable range.}, keywords = {Under-Floor Air Distribution (UFAD),Thermal comfort,energy saving,multi-objective optimization,Large Eddy Simulation (LES)}, url = {https://scientiairanica.sharif.edu/article_21490.html}, eprint = {https://scientiairanica.sharif.edu/article_21490_34d2d90dfe3930f6188e9834af05d0a5.pdf} } @article { author = {Haddad, Sh. and Baghani, M. and Zakerzadeh, M.R.}, title = {Size dependent analysis of tapered FG micro-bridge based on a 3D beam theory}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2889-2901}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.52031.2492}, abstract = {In the current study, an analytical solution based on the modified couple stress theory for a nonlinear model describing the couple 3D motion of a functionally graded tapered micro-bridge is presented. The small scale effects and the nonlinearity arising from the mid-plane stretching are taken into consideration. Governing equations of motions are derived utilizing the modified couple stress theory and applying Hamilton principle. Dynamic and static analyses to determine the effects of lateral distributed forces and mid-plane stretching are investigated. To this aim, analytical Homotopy-pade technique is employed to capture the nonlinear natural frequencies in high amplitude vibrations of tapered micro-bridges with different types of geometries and material compositions. The obtained results of frequencies propose that there is a good agreement between the present analytical results and the numerical ones in opposed to well-known multiple-scale method. Furthermore, comparing the results in 2D and 3D analyses shows that in 2D analysis, the stiffness and natural frequency of the micro-beam is underestimated and it is found that increasing the tapered ratio has different impacts on natural frequencies for micro-beams with different slender ratios.}, keywords = {Micro-bridge,3D beam theory,Couple stress,Tapered beam,Analytical HAM solution}, url = {https://scientiairanica.sharif.edu/article_21564.html}, eprint = {https://scientiairanica.sharif.edu/article_21564_8a51b900eb5af70dc77c0f84f87f6525.pdf} } @article { author = {Ghasemi, H. and Masoudi Nejad, R. and Jalayerian Darbandi, A. and Tadi Beni, Y. and Shariati, M.}, title = {Fatigue and fracture behavior of A516 steel used in thick-walled pressure vessels}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2902-2914}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.52119.2546}, abstract = {In this paper, the growth of semi elliptical crack in the walls of thick walled cylindrical pressure vessels has been investigated. Considering the importance of the crack growth problem in cylindrical pressure vessels provides a numerical and experimental 3D model for the growth of fatigue crack and estimating the fatigue life of pressure vessels. Because of available geometric geometric and physical parameters, it can be predicted the problem of the fatigue life of these pressure vessels more precisely in comparison with existing standard tests which are experimental and numerical. A most common specimen of thick walled tanks, steel, is analyzed for conducting experimental tests. The mechanical properties and fatigue behavior of A516 steel have been determined experimentally. For estimating the crack growth and calculation of fatigue life, boundary element method and linear fracture mechanics equations have been used. Finally, the experimental results for fatigue crack growth were compared with numerical method, which yielded acceptable results. The overall results show a good agreement between the experimental data and the numerical results.}, keywords = {Fatigue crack growth,Pressure vessel,Fatigue life,Fracture mechanics,Boundary element}, url = {https://scientiairanica.sharif.edu/article_21516.html}, eprint = {https://scientiairanica.sharif.edu/article_21516_971aba01f67f6a82cb54b2b8b055ce52.pdf} } @article { author = {Singh, T. S. and Verma, T. N.}, title = {Analysis of the effect of temperature on the morphology of egg shell calcium oxide catalyst: Catalyst production for biodiesel preparation}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2915-2923}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.52573.2780}, abstract = {The increase study on the usage of egg shell derived CaO being used as catalyst during biodiesel production have paved way for the need to study the effects of temperature on the calcination of egg shells. Therefore, the authors in the present study have undertaken calcination of chicken egg shells and duck egg shells at various temperatures of 800 °C, 900 °C and 1000 °C exposed at one hour. The synthesized CaO were characterised using X-ray diffraction (XRD), Fourier transform infra-red spectrometry (FT-IR), Scanning electron microscope (SEM) and Energy Dispersive X-ray analysis (EDX). The study have shown that there is changes in the distribution and formation of calcium, oxides and naturally occurring substance carbon, during calcination of the samples. It was observed in both the cases of chicken as well as duck egg shells that 800 °C is a decent temperature for calcinating the egg shells in producing calcium oxide catalyst.}, keywords = {Calcium oxide,chicken egg,duck egg,Catalyst}, url = {https://scientiairanica.sharif.edu/article_21496.html}, eprint = {https://scientiairanica.sharif.edu/article_21496_58c477c13b077605507b3003d91073d9.pdf} } @article { author = {Torabi, A. and Abedian, A. and Farsi, M.A.}, title = {An approximate methodology to simulate combined conduction-radiation heat transfer for multi-layer insulator}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2924-2932}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.53008.3003}, abstract = {A quasi-analytical methodology was developed to model combined conduction-radiation heat transfer through the thickness of a reflective multi-layer insulator. This methodology was validated by the experimental result. It could be used for earlier steps of the design process of the high-temperature multi-layer insulators. Traditionally, radiation thermal conductivity approximation is used in the earlier stages of design. Despite the accuracy of this approach in steady-state cases, it yields to some unacceptable errors when the thermal load is transient. It was shown that old methodology can not predict maximum temperature and time of occurrences in acceptable margins. The developed model originated from the radiation thermal conductivity approximation. But unlike the primitive one, the developed model seems acceptable in transient cases. This model is based on consideration of thermal emittance through the thickness of the insulator. It can predict the maximum temperature of the structure and occurrences time with an error of less than 4%.}, keywords = {combined conduction-radiation,reflective multi-layer insulator,approximate methodology,effective thermal conductivity,absorption area}, url = {https://scientiairanica.sharif.edu/article_21605.html}, eprint = {https://scientiairanica.sharif.edu/article_21605_fe6be9013490d291e28b705ba98c9c2b.pdf} } @article { author = {Ahmadi Dastgerdi, K. and Pazooki, F. and Roshanian, J.}, title = {Model reference adaptive control of a small satellite in the presence of parameter uncertainties}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2933-2944}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.50455.1704}, abstract = {An accurate control algorithm for small satellites is critical to the mission's success. In this paper, a novel discrete-time Model Reference Adaptive Control algorithm (MRAC) is developed based on unified approach for attitude control of a three-axis stabilized nonlinear satellite model. The linearized model of satellite with unknown dynamic parameters is derived and Recursive Least Squares (RLS) algorithm is used to identify the linear model’s unknown parameters. In order to take into account the nonlinear model of satellite dynamics, the proposed MRAC strategy is used considering the linear model, the estimation error; and the difference between the actual nonlinear system and the linear model outputs. The actual nonlinear model of satellite includes moments of inertia uncertainties, external disturbances, and sensor noise on the outputs. The introduced controller performance is compared with a conventional discrete -time MRAC which demonstrates excellent simultaneous regulation and tracking capabilities.}, keywords = {Discrete-Time,Model Reference Adaptive Control (MRAC),Parameter Uncertainty,Satellite}, url = {https://scientiairanica.sharif.edu/article_21522.html}, eprint = {https://scientiairanica.sharif.edu/article_21522_d0632d61fddf5a288217e478ab5d1528.pdf} } @article { author = {Wu, H. and Moradi, R. and Barzegar Gerdroodbary, M. and Shahbazi, M.}, title = {Development of micro gas actuator for analyzing gas mixture}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2945-2953}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.50575.1769}, abstract = {In this study, a computational technique is used to investigate the ability of a new MEMS gas actuator (MIKRA) for detection and sensation of the gas mixture. In this actuator, the temperature difference of two arms inside a rectangular domain at rarefied condition induces a Knudsen force which is relative to physical properties of the gas. Both 2d and 3D approaches are applied for the simulation of the flow inside the model. In order to define the flow feature of a low-pressure gas inside the micro gas actuator, a high order equation of Boltzmann should be solved to attain reliable results. Since the domain of this micro gas is non-equilibrium, Direct Simulation Monte Carlo (DSMC) method is applied for the simulation of the model. According to obtained results, a three-dimensional model presents more reliable results and the effect of a gap for three-dimensional model clearly demonstrates the impact of this parameter on the effective Knudsen force}, keywords = {Gas detection, Knudsen force,DSMC,low-pressure gas actuators,MEMS actuator}, url = {https://scientiairanica.sharif.edu/article_21672.html}, eprint = {https://scientiairanica.sharif.edu/article_21672_7074a9d01afb312009489b7c8a7bc4f2.pdf} } @article { author = {Mohammadi, M. and Khayyat, M.}, title = {Experimental investigation of the effect of one-dimensional roughened surface on the pool boiling of nanofluids}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2954-2966}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2020.51189.2048}, abstract = {The objectives of this research are to develop a special surface for increasing the nucleation heat transfer characteristics, decreasing the superheat temperature and postponing the occurrence of critical heat flux for long term work. A laboratory apparatus was built. In order to more feeding the microlayer of the bubble by capillary force of the micro-grooves, the boiling surface was roughened in one direction. Despite the fact that the boiling characteristics of roughened surface are improved relative to the polished surface, the results are not very impressive Although the boiling of two Nano-fluids, copper oxide and alumina on the micro-groove surface resulted in a significant increase in the nucleation heat transfer but this method cannot be used for a long time process because of the continues deposition of nanoparticles over the time and creation of insulation layer on the micro-groove surface. Therefore, simultaneous utilization of micro- groove surface, as well as the depositing of a thin and porous layer of nanoparticles on the surface increased the feeding of sites and the production of bubbles respectively. The critical heat flux and boiling heat transfer coefficient for the surface deposited with copper oxide nanoparticles enhanced by 46.5 % and up to 74.2% respectively.}, keywords = {Pool boiling,One-dimensional roughened surface,Deposition of nanoparticles,Critical heat flux,Heat transfer coefficient}, url = {https://scientiairanica.sharif.edu/article_22040.html}, eprint = {https://scientiairanica.sharif.edu/article_22040_3431429597ff7cb79bbe8e96b97ba79e.pdf} } @article { author = {Mallick, M. and Mohanta, A. and Kumar, A.}, title = {Multivariate adaptive regression spline approach to the assessment of surface mean pressure coefficient on surfaces of C-shaped building}, journal = {Scientia Iranica}, volume = {27}, number = {6}, pages = {2967-2984}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2020.51377.2142}, abstract = {Proper assessment of wind load enables durable design of structures under varying wind load conditions. The accurate prediction of pressure coefficient on any irregular plan shaped buildings is essential for the assessment of wind loads and the structural design. The main objective of this study is to present an equation in the line of Multivariate Adaptive Regression Spline (MARS) approach using experimental data of surface mean pressure coefficient. This developed equation can be used satisfactorily for the prediction of pressure coefficient values accurately on the surfaces of C-shaped buildings. An extensive experimentation was carried out to obtain coefficient of pressure over the surfaces of C-shaped models under varying sizes, corner curvature and angle of incidence in a sub-sonic wind tunnel. The predicted values of pressure coefficient of different C-shaped buildings using developed model are compared with equations developed by Swami and Chandra’s (S&C) and Muehleisen and Patrizi’s (M&P). The comparison indicates that the proposed MARS model predicts pressure coefficient values more accurately than those by S&C and M&P models on frontal as well as side surfaces. Further, the model is used to validate with the actual building, Tokyo Polytechnic University (TPU) data to show the applicability of the proposed equation.}, keywords = {Angle of incidence,C-shaped building models,mean pressure coefficient,Surface mean pressure coefficient,multivariate adaptive regression spline,wind tunnel test}, url = {https://scientiairanica.sharif.edu/article_21930.html}, eprint = {https://scientiairanica.sharif.edu/article_21930_a058de44d3c63ae30634162f5f939e73.pdf} }