Investigation of Power-Law Fluid Flow through a Two-Dimensional Microchannel Based on a Couple Stress Theory-Calculation of Characteristic Length
Fatemeh
Karami
PHD student, Shahrekord University
author
Afshin
Ahmadi Nodoushan
Mechanical Engineering Department, Shahrekord University, Shahrekord
author
Yaghoob
Tadi Bani
Shahrekord University
author
text
article
2019
per
The present paper aims to investigate the developed flow of Newtonian and non Newtonian fluids in a two-dimensional microchannel based on the completely consistent couple stress theory and the characteristic length of the fluids. First, the velocity and volumetric flow rate profiles of Newtonian and power-law non-Newtonian fluids in the microchannel were obtained via analytical methods. After that, the characteristic material lengths of water as a Newtonian fluid and blood as a non-Newtonian fluid were obtained and then the results were compared with the experimental data of other papers. Comparing the characteristic lengths of water and blood indicated the dependence of characteristic material length scale on the fluid material. Calculating the characteristic length produced the blood velocity profile of the couple stress theory in microchannel which was in turn compared to the results of classical Navier-Stokes theory. According to the results, increasing the volumetric flow rate of the fluid also increases the difference between the results of couple stress theory and classical theory, indicating the increased influence of length on microchannel flow properties. Further, the velocity profile of water in the microchannel was compared with the experimental results, revealing a good consistency between them and the couple stress theory.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1707
1714
https://mej.aut.ac.ir/article_3354_3e225d87c6a40897abb1e05f513f3ed1.pdf
dx.doi.org/10.22060/mej.2019.15246.6072
Numerical Study of Mixing in Double and Multiple T-Shaped Micromixers with Aligned and Non-Aligned Inputs
erfan
nematollahi
mechanic-energy conversion,mechanic engineer faculty,yazd university,yazd,iran
author
Mohammad
Sefid
دانشگاه یزد
author
text
article
2019
per
In this numerical investigation mixing behavior of two fluids water and ethanol with various density and viscosity mixing in 5 types of T-micromixers has been studied. The Geometries under research include 1 and 2 geometries are Multiple T-micromixer with non-aligned inputs in one and two plane respectively, and the 3, 4 and 5 geometries are included Multiple T-micromixer, double T-micromixer and T-micromixer. computational fluid dynamics commerical code of ANSYS fluent has been used to simulate mixing process at Schmidt number of 752.26 for Reynolds number in range of 1 to 200. For double T-micromixer and multiple T-micromixers two and three different types of placement for two fluids in the inputs respectively investigated and results has been compared. Cortes-Quiroz et al study used for validation present investigation. Mixing results compared for specific flow types in double and multiple micromixers with single flow type in T-micromixer. The results show mixing index and pressure drop are function of inputs’ number and position also for geometries with more than two inputs, types of input fluids have effect on these parameters.The value of 0.4878 is the maximum mixing index has been observed using flow type 1 in Multiple T-micromixer at the Reynolds number of 1.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1715
1728
https://mej.aut.ac.ir/article_3334_b7c15e3a8f02fb1899022d7895de54ae.pdf
dx.doi.org/10.22060/mej.2019.15037.6006
Experimental Study of Foam Generation in a Microfluidic Device
HR
Zanganeh
SUT
author
A
Bazzazi
SUT
author
Mohsen
Nazari
Shahrood University of Tech, Shahrood, Iran
author
MH
Kayhani
SUT
author
text
article
2019
per
Small scale tests can be conducted using Lab-on-a-chip devices with very tiny amount of fluids. In this paper, bubbles is generated with certain size in a flow focusing microfluidic device. Microfluidic device can be manufactured by SOFT LITHOGRAPHY. When the bubble density is high enough, they come in to contact, and they flow in the form of crystal foam. The flow of the foams in the channel depends on the liquid flow rate and inlet gas pressure. This shall determine dynamic behaviors of the flow such as super-stability. Two types of foam including wet and dry foams are generated in flow focusing device. At certain pressure of 600 to 700 (mbar), the foam behavior is switched to non-linear behavior in which the shape of bubble is changed in period of time. At specific flow rate of 0.1 and 0.2 (ml/hr), it is observed that bubbles are generated in one raw and some others are in two within channel which are called hex-one and hex-two. The effects of increasing the flow rate at constant pressure (which reduces the size of the bubble) and the effects of increasing the pressure in the constant flow rate (which increases the size of the bubble) are investigated.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1729
1740
https://mej.aut.ac.ir/article_3442_be8ca89d1fc9b17cca42d35f0a78db26.pdf
dx.doi.org/10.22060/mej.2019.14770.5948
Investigation of Flow in Microchannels with Superhydrophobic Surfaces Using Hybrid Direct Simulation Monte Carlo-Navier-Stokes Method with Information Preservation Approach
Ali
Babakhani
Mechanical Department, Engineering Faculty, Razi University, Kermanshah, Iran
author
Ali
Amiri-Jaghargh
Mechanical Department, Engineering Faculty, Razi University, Kermanshah, Iran
author
text
article
2019
per
In recent years, superhydrophobic surfaces have received significant attention due to properties such as drag reduction and self-cleaning. A superhydrophobic surface can be made by grooving the wall. In this case, the flow of gas caught in grooves may represent the rarefied flow. Therefore, particle-based approaches such as direct simulation Monte Carlo should be employed to simulate the flow. In this paper, laminar flow in superhydrophobic microchannels with ribs and cavities aligned perpendicular to the channel axis is investigated using a hybrid direct simulation Monte Carlo-Navier[1]Stokes method. Also, information preservation technique is employed to reduce statistical fluctuations of the direct simulation Monte Carlo method. The effects of the length of the cavity on the flow parameters such as effective slip length, and velocity slip are investigated and the results are compared with the simplified method of using Navier-Stokes equations with shear-free boundary condition as the gas-liquid interface. It is shown that the differences between the hybrid method and shear-free solution increase as the shear-free fraction increases. However, the difference is less than 6% for cases studied in this work. Therefore, it is acceptable to use the shear-free approach to reduce computational costs. Especially for Fc < 0.2 where the difference is less than 3%.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1741
1756
https://mej.aut.ac.ir/article_3443_e1e1c2f5a7dcec69a3eafba446eef46d.pdf
dx.doi.org/10.22060/mej.2019.15310.6093
New Development in Direct Simulation Monte Carlo Algorithm for Asymmetric Complex Geometry
ramin
zakeri
faculty of shahrrod university of tech. mech. dep.
author
ramin
kamalimoghadam
faculty of ARI
author
Mahmoud
Mani
MACHANICAL DEP, AUT
author
text
article
2019
per
In this paper, the development of the direct simulation Monte Carlo algorithm has been carried out for flow analysis around axial symmetric complex geometries in rarefied conditions with consideration of reduction in computational cost compared to a full three-dimensional state, appropriate accuracy of the results compared to related available references, as well as the proper selection of particles. In this paper, the algorithm is presented that involves studying different modes of motion and collision of particles with each other or the wall for axial symmetric complex geometries in such a way that the least computations are applied for achieving a high-efficiency solution. In the results section, various geometries such as simple geometry for first case and complex geometry for second case study is investigated and the results are compared with the validated results. The results show the proper accuracy of the proposed algorithm compared to the three-dimensional solvers. Also, the selection of the smallest number of suitable particles is one of the issues that has been studied for selecting the appropriate number of particles. It has been shown that in the first and second test cases, the 30000 and 500000 particles are at least number of particles with consideration of accuracy of results.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1757
1772
https://mej.aut.ac.ir/article_3509_a465b635d8f88367ff9053c61c1bec40.pdf
dx.doi.org/10.22060/mej.2019.15369.6104
Experimental Comparison of Injection Characteristics of Elliptical and Circular Liquid Jets into an Air Crossflow
Yosef
Rezaei
Department of Aerospace Engineering, Amirkabir University of Technology, Tehran, Iran
author
Mehran
Tadjfar
Department of Aerospace Engineering, Amirkabir University of Technology, Tehran, Iran
author
text
article
2018
per
The flow characteristics of liquid jets issuing from elliptical and circular injectors into an air crossflow were experimentally investigated. Two elliptical injectors with different aspect ratios and a circular injector as the reference case with the same cross-sectional area were employed. The major axis of the elliptical nozzles was aligned parallel and perpendicular to the air crossflow direction. The liquid jet was visualized using shadowgraph technique and a high speed camera was used to record the instantaneous status of the jets. The results revealed that some characteristics of injected liquid jets into the air crossflow such as penetration depth and the trajectory of liquid jet were affected by changing the nozzle exit shape. Based on the obtained results elliptical liquid jets because of the lower stability than circular jet, break up sooner and penetrate lower into the air crossflow. As the normalized breakup height of circular jet is obtained 29.5 but the normalized breakup height of elliptic jet with the aspect ratio of 3 and when its major axis was perpendicular to the crossflow direction, is obtained 21.53. In this study two different breakup regimes were observed, column breakup and bag breakup regimes.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2018
1773
1792
https://mej.aut.ac.ir/article_3200_9fea8bb64794a95b62419a1ba878de7f.pdf
dx.doi.org/10.22060/mej.2018.14953.5982
Experimental Study of the Supersonic Exhaust Diffuser Spray Cooling System
Nematollah
Fouladi
Space Transportation Research Institute, Iranian Space Research Center, Tehran, Iran
author
seyed Ahmadreza
Mirbabaei
Department of Aerospace Engineering, Sharif University of Technology
author
Mehdi
Khosroanjom
Space Transportation Research Institute, Iranian Space Research Center, Tehran, Iran
author
text
article
2019
per
A supersonic exhaust diffuser provides the required test cell vacuum conditions by self pumping of nozzle exhaust gases to the atmosphere in the high-altitude simulator. However, the plume temperature is often much higher than the allowable temperature of the diffuser structure. In the present study, a spray cooling system design method is presented for a supersonic exhaust diffuser. The method is evaluated by performing several experimental tests. First, in order to identify the critical temperature region, the test of the motor with a chamber pressure of 60 bar and a chamber temperature of 3100 °C is performed with a non-cooled metal diffuser. The results indicate that the temperature of the diffuser body in the inlet and ramp regions reaches a temperature above 1500 °C, which leads to the melting and perforation of the diffuser in these regions. Two other tests are performed with average motor chamber pressures of 33 bar and 55 bar along with the spray cooling of the diffuser body. The results show that the designed cooling system keeps the maximum temperatures of the external surface of the diffuser at the values smaller than 200 and 400 °C in these tests. The achieved critical temperatures are well-matched with the respected ones in the design procedure.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1793
1808
https://mej.aut.ac.ir/article_3371_ee7ad97ab035cef790121e6cf0d66e47.pdf
dx.doi.org/10.22060/mej.2019.15138.6038
Experimental Study of Effects of Bleed Geometric Parameters on the Performance of a Supersonic Axisymmetric Intake
Mohammad Ali
Maljaee
Mechanical Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad
author
Javad
Sepahi-Younsi
دانشگاه فردوسی مشهد
author
text
article
2018
per
A supersonic axisymmetric mixed compression air intake has been experimentally studied in a wind tunnel at three free-stream Mach numbers of 1.8, 2.0 and 2.2 at zero degrees angle of attack. Shadowgraph flow visualization has been used as well as the pressure transducers. By applying a suction slot over the external compression surface upstream of the throat, the effects of changing the area of the bleed entrance and exit on the intake performance parameters such as mass flow ratio, total pressure recovery, flow distortion and bleed mass flow ratio have been investigated. The results showed that by increasing the area of the bleed entrance, total pressure recovery increases in critical and subcritical conditions and if simultaneously the area of the bleed exit increases, the pressure recovery will be further improved, especially in subcritical condition. The results also indicated that if the area of the bleed entrance becomes very large, it can have an adverse effect on the intake performance, especially in the critical condition even worse than the no bleed case. However, using a large bleed entrance can postpone the buzz onset at off-design conditions.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2018
1809
1828
https://mej.aut.ac.ir/article_3199_1ab9ab0cc7f7e27c52543f9957856045.pdf
dx.doi.org/10.22060/mej.2018.14823.5952
Frequency Analysis and Parametric Estimation of Bubble Formation in Vertical Column
Ehsan
Habibi Siyahpoosha
Faculty of Mechanical Engineering, Tehran, Tarbiat Modares University
author
Mohammad Reza
ansari
Faculty of Mechanical Engineering
author
text
article
2019
per
Frequency analysis is one of the most important methods to estimate parameters of bubble formation in a vertical liquid column. In the present article, the frequency of bubble formation was analysed. Three-dimensional transient two-phase flow was simulated based on the volume of fluid method. Hybrid Reynolds averaged Navier-Stokes/large eddy simulation turbulence methods were used to improve the ability of computational fluid dynamics to capture formation of bubble in the vertical column. The model used for frequency response prediction was modified by applying the compressibility effect that improved the results for the acoustic behaviour. Due to the importance of interface tracking for sound sources recognition in addition to the problems which occur during combining with the large eddy simulation model in the simulation, different interface reconstruction methods have been applied and high-resolution interface capturing scheme was selected. The results were verified by theoretical and empirical data. Furthermore, it was presented that the natural frequency of bubble reduced as the size of the bubbles increased. The compressibility effect improved the results more accurately and the model behaviour was acted more physically.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1829
1846
https://mej.aut.ac.ir/article_3364_314bffca7cd3ca134d96fb0f1ff53a8f.pdf
dx.doi.org/10.22060/mej.2019.15110.6027
An Image-Based Computational Simulation of Pulmonary Embolism Using Radiological Images
Fateme
Mirakhorly
MSc student/University of Tehran
author
Bahman
Vahidi
Associate professor/University of Tehran
author
Marzieh
Pazoki
Department of Pulmonary Medicine, Tehran University of Medical Sciences, Tehran, Iran
author
text
article
2019
per
Pulmonary embolism is one of the most prevalent diseases amid hospitalized patients. However, this phenomenon has not been investigated in the field of biomechanics so far and insufficient information is available about hemodynamic factors affecting this phenomenon. In this research, a patient-specific anatomical model of pulmonary arteries has been constructed from computed tomography images. Navier-Stokes equations, as the governing equations, have been solved in an arbitrary Lagrangian-Eulerian formulation, and the fluid-structure interactions method was used. Viscoelastic parameters were adopted in accordance with the red blood clot (stemmed from deep veins) properties for the structure model (emboli). Results revealed that the maximum shear stress magnitude applied on the embolus was about 957 Pa that was occurred when the clot plow into the wall of the artery. In addition, the average shear stress of the arterial wall was reduced about 42 percent due to the presence of the embolus. This reduction may lead to such phenomena as high pulmonary arterial resistance, low pulmonary arterial compliance, endothelial dysfunction, and consequently cause right heart dysfunction and pulmonary arterial hypertension if different clots repeatedly pass through the arteries.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1847
1864
https://mej.aut.ac.ir/article_3378_d3d14b65dc84614ebd6954dc6a23b137.pdf
dx.doi.org/10.22060/mej.2019.14941.6000
Aerodynamic Performance Improvement of Hybrid Darrieus-Savonius Vertical Axis Wind Turbine
Abolfazl
Abdolahifar
Department of Aerospace Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran.
author
S.M.H
Karimian
Department of Aerospace Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran.
author
text
article
2019
per
Returning blades of Savonius vertical axis wind turbines make negative effects on the total moment produced by the turbines especially at high tip speed ratios. For hybrid Darrieus[1]Savonius vertical-axis wind turbines at the dynamic mode, with tip speed ratio increment from self[1]starting to that of high values, returning blades of its Savonius part make the whole part to produce negative moment. In the present work, in order to reduce negative effects of returning blades of Savonius vertical-axis wind turbines and consequently improve its aerodynamic performance, a wall is placed in front of them. Several configurations including two types of blade shapes with three types of wall placements are simulated three-dimensionally and their output-moment and moment fluctuations are computed for one complete cycle. Desired Savonius vertical-axis wind turbine with suitable wall which produces the most average-moment and the least moment fluctuations are mounted on a straight-blade Darrieus vertical-axis wind turbine and they formed a hybrid vertical-axis wind turbine. In comparison to straight-blade vertical-axis wind turbine, at the tip speed ratio of 0.9 proposed hybrid vertical-axis wind turbines produces 2.3% more average-moment along with 40% fewer moment fluctuations. This means in term of tip speed ratio values, proposed hybrid vertical-axis wind turbine has wider operating range in comparison to its general types.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1865
1884
https://mej.aut.ac.ir/article_3258_c53270ad021850152b4048769694bdbd.pdf
dx.doi.org/10.22060/mej.2019.15129.6034
Far-field Aeroacoustic Noise Prediction of a Tall Standard Building Model by Measuring Unsteady Surface Pressures
Alireza
Movahedi
University of Yazd
author
Ali Akbar
Dehghan
Mech. Eng. Dept, Faculty of Engineering, Yazd University, IRAN
author
Mojtaba
Dehghan Manshadi
Malek Ashtar University of Technology
author
text
article
2018
per
In the present study, far-field aeroacoustic noise emitted due to the air flow over a standard tall building model at different angles of attack is investigated. The purpose of this study is to estimate the far-field aeroacoustic noise emitted by measuring the unsteady surface pressures. The surface pressure data are used as input of a numerical algorithm which is written to solve the Ffowcs Williams and Hawkings equation. The aerodynamic and aeroacoustic characteristics of flow over a twodimensional square cyliner (for algorithm validation) and the main model are presented. The results revealed that the peak of vortex shedding frequency could be observed in the spectrum of surface pressure signals of sensors located on the side surfaces of the model. Its frequency is in an excellent agreement with the signals captured by hot wire measurement. The Strouhal number changes in the range of 0.08-0.1 depending on the angle of attack. Dipole pattern for sound radiation was also observed for three-dimensional model which is related to the vortex shedding phenomenon. The sound pressure level increases with increasing upstream velocity and decreases with distance from the model. The effect of angle of attack is also dependent on the reciever’s location.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2018
1885
1904
https://mej.aut.ac.ir/article_3066_388886a09a83b76aea9523212e70891b.pdf
dx.doi.org/10.22060/mej.2018.14260.5826
A Review of Studies on the Motion of Particles Under the Influence of Acoustic Waves in Microfluidic Systems
Sayed Mostafa
Zareei
Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran
author
Mostafa
Jamshidian
Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran
author
Shahrokh
Sepehrirahnama
Department of Mechanical Engineering, National University of Singapore, Singapore
author
Saeed
Ziaei-Rad
Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran
author
text
article
2019
per
The use of acoustic waves to control and manipulate suspended particles in the fluid has attracted particular attention in the last two decades. The propagation of acoustic waves in the fluid medium may affect the suspended particles mainly by two factors. The initial effect of wave propagation directly acts on the particles and causes the application of force on them via the fluid medium. In viscous fluid, due to the wave attenuation and the formation of velocity gradients due to viscosity, the secondary fluid streaming forms that can indirectly affect the particles. Due to the wide applications of this technology in medical and biological fields and the complexity of the experimental work in micrometer dimensions, there is a growing demand for analytic studies and theoretical insights on this subject. The subject of the present paper is a review on the analytical studies of the mechanisms affecting the movement of particles under the influence of acoustic waves propagating in the microfluidic systems. This review article presents a historical review of the early theories for the calculations of acoustic radiation forces and follows the progress of these theories up to the now. Also, a review of the existing research results, problems and limitations, and the effect of different parameters on estimating these results are presented.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1905
1924
https://mej.aut.ac.ir/article_3454_acc260a1eb298cf57cd936751b8be320.pdf
dx.doi.org/10.22060/mej.2019.15275.6081
Hydrodynamic Behavior of Different No-Slip Condition on the Curved Boundaries in
the Lattice Boltzmann Method
Taghilou
Taghilou
زنجان-مهندسی- گروه مهندسی مکانیک
author
Jalal
Ghasemi
دانشگاه زنجان/ هیات علمی گروه مهندسی مکانیک
author
Aref
Salimi
Department of Mechanical Engineering, University of Zanjan
author
text
article
2019
per
This paper examines the various methods of applying no-slip boundary condition on a fixed and rotary cylinder in the lattice Boltzmann framework. For this purpose, five methods of bounce[1]back, linear and quadratic method of Yu and the linear and quadratic method of Bouzidi are chosen. The main challenge in all of these methods is how to calculate and interpolate the unknown distribution functions at the points around the boundary points. Results show that in the stable conditions (Re=20 and Re=40), the maximum error of calculation of the separation angle is 6.7 % and it is related to the bounce-back method, while in the stable conditions, a significant difference cannot be seen between the bounce-back and other methods. Also, the linear method of Bouzidi has the most error in calculating the separation length (6% for Re=20 and 8.82 % for Re=40). By increasing the Reynolds number and increasing the rotational velocity, a difference in the lift coefficient in the early times, t*> 7.78 grows for the conditions of k=0.2 and Re=200, between the bounce-back and other methods, however with increasing time, this difference reduces, whereas the three methods of linear Yu, linear Bouzidi and quadratic Bouzidi, continue to produce similar results.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1925
1942
https://mej.aut.ac.ir/article_3336_d6a57d65ad1cde948e88276861a3e8cb.pdf
dx.doi.org/10.22060/mej.2019.15328.6095
Experimental and Numerical Simulation of Fluid Flow and Inclusion Removal in the
Steel Continuous Casting Tundish
mohamad reza
mosalman yazdi
yazd university
author
Ahmad Reza
Faghih Khorasani
دانشگاه یزد*فنی و مهندسی
author
Shahram
Talebi
Mechanical Engineering/Yazd University
author
text
article
2019
per
During the steel continuous casting process, the tundish is the last metallurgical actuator in which there will be an opportunity for removal of impurities present in the melt. Therefore, improving of the fluid flow phenomena inside the tundish, including the type of fluid flow pattern, increasing of inclusion residence time in the tundish, decreasing of volume of stagnant fluid and increasing of fluid flow in the rotation, can improve the process of separation of the inclusion and absorbing them into slag and the preparation of clean steel. In the mathematical method, the FLUENT software is used and in the experimental method, by manufacturing of the glass tundish in 1:4 scale and molten flow physical simulation, the effect of applying the dam in the tundish, as well as the change in the height of the melt on the behavior of the flow has been investigated, and it has been determined that decreasing of the molten height in the tundish increases the separated inclusion from the molten and inclusion residence time in the tundish. Also, using the dam at the inlet nozzle with a tall dam on the sides of the tundish leads to the removal of the inclusion and improving the molten flow.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1943
1954
https://mej.aut.ac.ir/article_3440_dfd8f70fb70bf34b11d23c26e13f88d8.pdf
dx.doi.org/10.22060/mej.2019.15523.6148
Numerical Simulation of Three-Dimensional and Bi-Disperse Particle-Laden Turbidity Current in an Experimental Channel in the Presence of an Obstacle
Saba
Teymouri
Department of Mechanical Engineering, University Of Zanjan, Zanjan, Iran.
author
Ehsan
Khavasi
Mechanical engineering department, University of Zanjan
author
text
article
2018
per
In the present study, the propagation of a continuous three-dimensional, in collision with obstacle and bi-disperse particle-laden turbidity current with a large eddy simulation method was modeled using the OpenFOAM numerically. Due to the presence of a large number of suspended particles, the Eulerian-Eulerian method has been used and for each particle a concentration equation, which the particles settling velocity has been added to, is solved. The results show that before the obstacle, there is no significant change in the current velocity profiles in with and without obstacle state, but the presence of an obstacle decreases the maximum velocity by 10%, also the number of suspended particles on the obstacle decreases in channel width. In the final semi-stable state, the maximum concentration of 15.3% is reduced compared to the without obstacle state. By increasing the particle diameter to 20 and 30 microns, maximum concentration is increased by 12.5% and 22.3%, the number of suspended particles also decreases by 68% and 21%, respectively. As a result, particles with larger diameter precipitate more and rapidly. Changing the inlet concentration in the case of smaller diameter particle increases the number of suspended particles by 11.2% and current will have more capability for carrying suspended particles.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2018
1955
1974
https://mej.aut.ac.ir/article_3212_de661cf2af0464d6faff13a71fcb2603.pdf
dx.doi.org/10.22060/mej.2018.14882.5967
Modeling of the Magnetorheological Damper with Optimization Approach for Magnetic Fluid Molecular Properties
mohsen
Ghafarian eidgahi
PhD student of mechanical engineering, Shahrood university of technology
author
Mohammad Mohsen
Shahmardan
Department of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran
author
Mahmood
Norouzi
Associated professor of mechanical engineering, Shahrood university of technology
author
text
article
2018
per
Magnetorheological damper, as one of the most widely used equipment in various industries, was firstly studied and optimized using a molecular properties analysis of operating magnetic fluid in it utilizing dissipative particle dynamics as molecular modeling method. By using modified Bouc-Wen model, hysteresis and damping force level have calculated in order to provide the required 10 N power requirement in micro-machines and after validation with experimental results presented in papers, the effect of molecular properties of magnetic fluid operating on it has investigated. Results of molecular modeling by dissipative particle dynamics method show that by increasing mass and diameter of magnetic particles, damping force increases, while by increasing number density of these particles and increasing mass of carrier fluid particles, damping force firstly increases and then decreases. Therefore, it is necessary to set optimal values. It is also observed that by decreasing the thickness of the surfactant layer at the surface of the magnetic particles, damping force increases. Finally, according to the obtained results, the optimal values of each studied parameters were determined to provide 10 N damping force with the least amount of energy consumed by damper and selected from commercial magnetic fluids 132-DG fluid as suitable magnetorheological fluid.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2018
1975
1992
https://mej.aut.ac.ir/article_3159_5b4feeae9d9e09d983b055f1a71b2f0f.pdf
dx.doi.org/10.22060/mej.2018.14751.5930
Modelling and Experimental Investigation of the Evaporation Suppression Using Floating Covers in the Presence of Surface Flows
amir
rezzazadeh
Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood
author
Pooria
Akbarzadeh
Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood
author
Milad
Aminzadeh
Department of Civil Engineering, Isfahan University of Technology, Isfahan, Iran
author
text
article
2019
per
The increase in fresh-water demand due to the rapid population growth and climate changes with severe droughts highlights the protection of limited fresh-water resources. In arid regions, evaporation accounts for a significant fraction of losses from water reservoirs. Among different methods for suppressing evaporative loss, the use of modular floating elements offers a simple and reliable technique. Despite numerous studies on application of floating elements, performance of this method in the presence of surface flows is not yet addressed comprehensively. Hence, the present study aims to investigate the effect of surface flows on evaporation from covered reservoirs. For this purpose, a 500-liter water reservoir was covered with white and black balls and a water-pump provided surface flows at different rates. The results show that evaporation decreases monotonically with increasing surface flow rate until a specific flow rate, called optimal flow rate. The increase in surface flow more than this optimal rate results in increase in evaporative loss. Regardless of surface flow condition, the results indicate that the lowest water evaporation occurs for the coverage with white balls while coverage using a mixture of black and white balls and only with black balls showed higher evaporation rates, respectively (the highest evaporation is of course for the uncovered surface). The experimental findings demonstrate that surface flows with appropriate rates can effectively enhance evaporation suppression efficiency of floating elements. Comparison of the modeling results with experimental outputs highlights application of the physically-based energy balance model in estimating surface evaporation for covered and uncovered water surfaces with and without surface flow conditions.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
1193
2010
https://mej.aut.ac.ir/article_3382_0835be3ae7ee6abc34ad81739fe5aa27.pdf
dx.doi.org/10.22060/mej.2019.15515.6145
Roll Dynamic Stability of an Autonomous Underwater Vehicle with a Fish-like Hull
Shape
Amir
Honaryar
PhD Student / Department of Maritime Engineering , Amirkabir University of Technology
author
Mahmoud
Ghiasi
صنعتی امیرکبیر*مهندسی دریایی
author
text
article
2019
per
An autonomous underwater vehicle designed and manufactured with fish-like hull shape in order to survey subsea pipeline and cable is analyzed hydrodynamically. Not only does having high hydrodynamic stability increase course keeping ability, but it facilitates dynamic behavior control of robot regarding the disturbances like marine currents in the water. Roll dynamic instability would be an adverse phenomenon for underwater vehicles results in the deviation from the main path. After mentioning governing motion equations of vehicle, hydrodynamic moment acting on the body has been computed numerically using computational fluid dynamics. The robot is assumed to be a rigid body and the flow passing over it is considered steady and incompressible. Having extracted relationship between moment and flow angular velocity, the linear hydrodynamic coefficient needed for stability analysis is estimated. Using this damping coefficient, roll dynamic stability of the robot has been evaluated. To ensure the accuracy of numerical results, computations are compared with axisymmetric body designed and manufactured in Ship Hydrodynamic Department of David Taylor Research Center; Comparisons show firmly good agreement with experiments. Results reveal that roll dynamic stability of proposed hull shape with triangular cross-section is 10 times as great as that of conventional axisymmetric body with circular cross-section.
Amirkabir Journal of Mechanical Engineering
Amirkabir University of Technology
2008-6032
52
v.
7
no.
2019
2011
2026
https://mej.aut.ac.ir/article_3355_12bd2969b7ac05dc47ce25eced8ce550.pdf
dx.doi.org/10.22060/mej.2019.15237.6066