Perturbation Technique
M. Zamanian; M. Hadilu; B. Firouzi
Abstract
In this paper, a comparison is made between direct and indirect perturbation approaches to solve the non-linear vibration equations of a piezoelectrically actuated cantilever microbeam. In this comparison, the equation of motion is considered according to Euler-Bernoulli theory with considering the non-linear ...
Read More
In this paper, a comparison is made between direct and indirect perturbation approaches to solve the non-linear vibration equations of a piezoelectrically actuated cantilever microbeam. In this comparison, the equation of motion is considered according to Euler-Bernoulli theory with considering the non-linear geometric and inertia terms resulted from shortening effect. In the direct perturbation approach, the multiple scales method is directly applied to the partial differential equation of motion. In the indirect approach, the multiple scales perturbation technique is applied to the discretized equation of motion. It is shown that, if the equation of motion is discretized using one non-uniform microbeam mode shape as a comparison function, then the results of indirect perturbation approach will be identical to those of the direct perturbation approach. Moreover, it is observed that discretization using one uniform microbeam mode shape as a comparison function results in a different output. The concept of non-uniform microbeam mode shape is the linear mode shape of the microbeam by considering the geometric and inertia effects of the piezoelectric layer.
Manufacturing Processes
Mehdi Tajdari; Saeed Zare Chavoshi
Abstract
In the present study, five modeling approaches of RA, MLP, MNN, GFF, and CANFIS were applied so as to estimate the radial overcut values in electrochemical drilling process. For these models, four input variables, namely electrolyte concentration, voltage, initial machining gap, and tool feed rate, were ...
Read More
In the present study, five modeling approaches of RA, MLP, MNN, GFF, and CANFIS were applied so as to estimate the radial overcut values in electrochemical drilling process. For these models, four input variables, namely electrolyte concentration, voltage, initial machining gap, and tool feed rate, were selected. The developed models were evaluated in terms of their prediction capability with measured values. It was clearly seen that the proposed models were capable of predicting the radial overcut. However, the MLP model predicted the radial overcut with higher accuracy than the other models. The statistical analysis showed how much the radial overcut was mainly influenced by voltage and electrolyte concentration during the electrochemical drilling process.
Turbulance
Mohammad Reza Nikpour; payam khosravinia; Davod Farsadizadeh
Abstract
Formation of shock waves has an important role in supercritical flows studies. These waves are often occurring during passage of supercritical flow in the non-prismatic channels. In the present study, the effect of length of contraction wall of open-channel for two different geometries (1.5 m and 0.5 ...
Read More
Formation of shock waves has an important role in supercritical flows studies. These waves are often occurring during passage of supercritical flow in the non-prismatic channels. In the present study, the effect of length of contraction wall of open-channel for two different geometries (1.5 m and 0.5 m) and fixed contraction ratio was investigated on hydraulic parameters of shock waves using experimental model (models 1 and 2). For achieving to this goal, values of height and instantaneous velocity were measured in various points of shock waves observed in contractions for four Froude Numbers. In general, non-uniform distribution of velocity and turbulence intensity profiles were completely clear. Comparing results of models 1 and 2, show that the height and velocity values of formed waves in the model 2 is so much more than the model 1. Also, motion of the shock waves was accompanied with longitude gradient decrease of turbulence kinetic energy. The results of the present research can be very useful for designer engineers.
Fatigue
Mazuri Erasto Lutema; Awel Mohammedseid Momhur
Abstract
The most crucial parts that literally sustain the safety of railroad rolling stock from the subfloor are the wheels. However, during operation, several random parameters can impair their performance, resulting in the train's unsafety. These unpredictable characteristics can lead to fatigue failure, especially ...
Read More
The most crucial parts that literally sustain the safety of railroad rolling stock from the subfloor are the wheels. However, during operation, several random parameters can impair their performance, resulting in the train's unsafety. These unpredictable characteristics can lead to fatigue failure, especially in a CHR2 high-speed train. This study aims to analyse the fatigue life of railway wheels for the CHR2 high-speed train due to different random parameters. Three scenarios with random parameters were considered: suspension system, passenger weight, and train speed. A 3D wheel model created by CAD and analyzed with finite element software ANSYS and nCode to validate the model by applying static force. A railway vehicle-track dynamics model with a 30t axle load using the vehicle-track dynamics theory. Then Monte Carlo simulations performed to produce random samples of sensitive parameters and analyze their effect distributions on wheel–rail contact under random wheel parameters. The findings demonstrate that the random parameters of the suspension system have more negative effects on fatigue life compared to random passengers’ weight and train speed, however, random passengers’ weight has a less negative impact compared to random suspension and passenger weight. But also, the dynamic results stress analysis showed that the random suspension system parameters have a high maximum stress compared to the stress obtained from random passengers’ weight and train speed. Moreover, the random suspension system parameters have high maximum stress compared to stress obtained from random passengers’ weight and train speed.
Computational Fluid Dynamics (CFD)
Sandeep Naramgari; Siva Krishnam Raju C; G. Kumaran
Abstract
This study deals with the three-dimensional flow of a chemically reacting magnetohydrodynamic Sisko fluid over a bidirectional stretching surface filled with the ferrous nanoparticles in the presence of non-uniform heat source/sink, nonlinear thermal radiation, and suction/injection. After applying the ...
Read More
This study deals with the three-dimensional flow of a chemically reacting magnetohydrodynamic Sisko fluid over a bidirectional stretching surface filled with the ferrous nanoparticles in the presence of non-uniform heat source/sink, nonlinear thermal radiation, and suction/injection. After applying the self-suitable similarity transforms, the nonlinear ordinary differential equations are solved numerically using Runge-Kutta and Newton’s methods. Results present the effects of various non-dimensional governing parameters on velocity, temperature and concentration profiles. Also, computed and discussed the friction factor coefficients along with the local Nusselt and Sherwood numbers. Similarity solutions for suction and injection cases are presented. A good agreement in the present results with the existed literature under some special limited cases is found. It is found that heat and mass transfer performance of Sisko ferrofluid is significantly high in injection case when compared with the suction case. Increasing values of the stretching parameter enhance the heat and mass transfer rate.
Fluid Mechanics
Rasoul Talebian; Mansour Talebi
Abstract
In the present study, the pressure drop of the nanofluid flow of carbon-water nanotubes (CNT/water) in a helical three-tube heat exchanger with constant fluid physical properties has been experimentally evaluated. For this purpose, first, the experimental device was designed and manufactured and then ...
Read More
In the present study, the pressure drop of the nanofluid flow of carbon-water nanotubes (CNT/water) in a helical three-tube heat exchanger with constant fluid physical properties has been experimentally evaluated. For this purpose, first, the experimental device was designed and manufactured and then the carbon-water nanotube nanofluid with volume percentages of 0.01%, 0.1%, and 0.5% was prepared and stabilized. For the experiment, two triple-tube helical heat exchangers with different geometries are considered, in which the diameter of the middle pipe varies in two geometries. The pitch of the helical coil is 100mm and the helix radius is 9.235mm. The experiment was performed on Dean numbers between 1000 and 5000. The measured and calculated data were according to the available correlation in the literature with an error of less than 4%. It is found that at low volumetric percentages of CNT, the pressure drop is almost equal to that of the base fluid, and with increasing volumetric percentage of nanoparticles, the pressure drop also increases. By changing the geometry of the tube (decreasing the middle diameter of the tube), the pressure drop decreases.
Fluid Mechanics
Kezzar Mohamed; tabet ismail; nafir Nourreddine; sari Mohamed Rafik
Abstract
In this paper, the bioconvective nanofluid flow in a horizontal channel was considered. Using the appropriate similarity functions, the partial differential equations of the studied problem resulting from mathematical modeling are reduced to a set of non-linear differential equations. Thereafter, these ...
Read More
In this paper, the bioconvective nanofluid flow in a horizontal channel was considered. Using the appropriate similarity functions, the partial differential equations of the studied problem resulting from mathematical modeling are reduced to a set of non-linear differential equations. Thereafter, these equations are solved numerically using the fourth order Runge-Kutta method featuring shooting technique and analytically via the Adomian decomposition method (ADM). This study mainly focuses on the effects of several physical parameters such as Reynolds number (Re), thermal parameter (𝛿𝜃), microorganisms density parameter (𝛿s) and nanoparticles concentration (𝛿f) on the velocity, temperature, nanoparticle volume fraction and density of motile microorganisms. It is also demonstrated that the analytical ADM results are in excellent agreement with the numerical solution and those reported in literature, thus justifying the robustness of the adopted Adomian Decomposition Method.
Thermodynamics and Cumbustion
Satyananda Tripathy; Manmatha K Roul; Akshaya K Rout
Abstract
Theoretical investigation of turbulent flame impinging normally on plane surfaces isdone to determine the average Nusselt number and the plate heat flux distribution as functions of jet Reynolds number, equivalence ratio, and separation distance. The analysis is established on the mathematical formulation ...
Read More
Theoretical investigation of turbulent flame impinging normally on plane surfaces isdone to determine the average Nusselt number and the plate heat flux distribution as functions of jet Reynolds number, equivalence ratio, and separation distance. The analysis is established on the mathematical formulation of the governing equations for conservation of mass, momentum, and energy. The turbulence phenomenon is analyzed with the help of the RNG k-ε turbulence model. The radiative heat transfer model has been designed by using the Discrete Ordinates radiation model. Results show that the heat flux graduallyincreases with the radial distance towards the plate center and attains a maximum value at a location slightly away from the stagnation point. The peak value in the local heat flux comes closer to the stagnation point when the height between the plates and the nozzle increases. Effects of variation of dimensionless separation distance on heat transfer characteristics are investigated. It is observed that heat flux gradually improves when the value of separation distance changes from 12 to 8 and decreases near the stagnation region with the further decrease in separation distance from 8 to 4.
Stress Analysis
Sidda Reddy Bathini; Vijaya Vumar Reddy K
Abstract
This paper presents closed-form formulations of higher order shear deformation theory (HSDT) to analyse the functionally graded plates (FGPs) acted upon a thermo-mechanical load for simply supported (SS) conditions. This theory assumes nullity conditions for transverse stress on bottom and top face of ...
Read More
This paper presents closed-form formulations of higher order shear deformation theory (HSDT) to analyse the functionally graded plates (FGPs) acted upon a thermo-mechanical load for simply supported (SS) conditions. This theory assumes nullity conditions for transverse stress on bottom and top face of the FGPs. Moreover, it considers the influence of both stresses and strains in the axial and transversal direction. In these improvements, an accurate parabolic variation is assumed in the thickness direction for transverse shear strains. Therefore, this theory omits the use of correction factor for accurately estimating the shear stress. The physical properties of the FGPs are considered to change along the thickness using a power law. The equilibrium relations and constraints on all edges are attained by considering the virtual work. Numerical evaluations are attained based on Navier’s approach. The exactness and consistency of the developed theory are ascertained with numerical results for deflections and stresses of SS FGPs; and it is deemed that numerical solutions for thermo-mechanical load will utilize as a reference in the future.
Biomechanics
Adel Maghsoudpour; Ali Dorostghol; Ali Ghaffari; Mansour NikkhahBahrami
Abstract
To quickly detect sudden Cardiac Death (SCD), it's decisive to gather suitable information and enhance the accuracy of the diagnosis algorithms. Consequently, In the present study the heart rate variability (HRV) signal of subjects who experienced sudden cardiac death (SCD) was studied. We looked at ...
Read More
To quickly detect sudden Cardiac Death (SCD), it's decisive to gather suitable information and enhance the accuracy of the diagnosis algorithms. Consequently, In the present study the heart rate variability (HRV) signal of subjects who experienced sudden cardiac death (SCD) was studied. We looked at people's heart signals for one hour before something happened to see if there were any noticeable changes. The patients' HRV signals are segregated into 5-minute parts in the suggested approach. Each section is divided into four shorter signals. Thereupon, The energy and instant amplitude of each sub-signal are examined. The information flows between signal strengths and measuring the complexity of energy sub-signals would be checked. A significant change from its former section is identified. A support vector machine (SVM) classifier benefits from detecting individuals exposed to SCD by considering significant changes as indicators of the SCD process. It can anticipate SCD 15 minutes before it happens. Not restricted to any special subclass of cardiac diseases, this technique has priority. To evaluate the algorithm's specificity, it has been used not only with patients having SCD but also with individuals who are healthy, as well as those with coronary artery disease (CAD) and congestive heart failure (CHF), analyzing their HRV signals. The specificity values for normal, CHF, and CAD patients are 100%, 93.3%, and 95.6%, respectively, in the results.
Fluid Mechanics
F. Khalighi; A. Ahmadi; A. Keramat
Abstract
Four explicit finite difference schemes, including Lax-Friedrichs, Nessyahu-Tadmor, Lax-Wendroff and Lax-Wendroff with a nonlinear filter are applied to solve water hammer equations. The schemes solve the equations in a reservoir-pipe-valve with ...
Read More
Four explicit finite difference schemes, including Lax-Friedrichs, Nessyahu-Tadmor, Lax-Wendroff and Lax-Wendroff with a nonlinear filter are applied to solve water hammer equations. The schemes solve the equations in a reservoir-pipe-valve with an instantaneous and gradual closure of the valve boundary. The computational results are compared with those of the method of characteristics (MOC), and with the results of Godunov''s scheme to verify the proposed numerical solution. The computations reveal that the proposed Lax-Friedrichs and Nessyahu-Tadmor schemes can predict the discontinuities in fluid pressure with an acceptable order of accuracy in cases of instantaneous and gradual closure. However, Lax-Wendroff and Lax-Wendroff with nonlinear filter schemes fail to predict the pressure discontinuities in instantaneous closure. The independency of time and space steps in these schemes are allowed to set different spatial grid size with a unique time step, thus increasing the efficiency with respect to the conventional MOC. In these schemes, no Riemann problems are solved; hence field-by-field decompositions are avoided. As provided in the results, this leads to reduced run times compared to the Godunov scheme.
Heat and Mass Transfer
Isa Ahmadi
Abstract
The non-Fourier effect in heat conduction is important in strong thermal environments and thermal shock problems. Generally, commercial FE codes are not available for analysis of non-Fourier heat conduction. In this study, a meshless formulation is presented for the analysis of the ...
Read More
The non-Fourier effect in heat conduction is important in strong thermal environments and thermal shock problems. Generally, commercial FE codes are not available for analysis of non-Fourier heat conduction. In this study, a meshless formulation is presented for the analysis of the non-Fourier heat conduction in the materials. The formulation is based on the symmetric local weak form of the second-order non-Fourier heat conduction equation in terms of the temperature. Using the local weak form of heat transfer equations in the sub-domains, the governing equation of the non-Fourier heat conduction is discretized in the space domain to the second order ordinary differential equations for the time. The discretized equations are integrated into the time domain with an appropriate finite difference method. The fictitious numerical oscillations are completely suppressed from the front of temperature waves in the presented method. An analytical series solution is developed for the non-Fourier heat transfer in one-dimensional heat transfer for special boundary conditions and the accuracy of presented numerical meshless method is validated by comparison of the results of the numerical meshless solution and the series solution. The numerical results are presented for non-Fourier heat conduction for various Vernotte numbers and boundary conditions and the results are compared with the results of the classical Fourier heat conduction.
Vibration
Nima Nadirian; Hasan Biglari; Mohammad Ali Hamed
Abstract
The purpose of this paper is control of simply supported flexible core sandwich beam's linear vibration equipped with piezoelectric patches under different loads. The effects of external forces imposed on sandwich beam can be reached to a minimum value by designing an appropriate controller and control ...
Read More
The purpose of this paper is control of simply supported flexible core sandwich beam's linear vibration equipped with piezoelectric patches under different loads. The effects of external forces imposed on sandwich beam can be reached to a minimum value by designing an appropriate controller and control the beam's vibration. Three-layer sandwich beam theory is used for analytical modeling of sandwich beam vibration. Euler-Bernoulli beam theory and linear displacement field are used for the face-sheets and the soft core, respectively. The piezoelectric stress resultants are expressed in terms of Heaviside discontinuity functions. Governing equations of motion are obtained using Hamilton’s principle. The state space equations of system are derived from governing equations of motion, by defining suitable state variables and using Galerkin’s method. The controller is designed using linear quadratic Gaussian (LQG) technique and Kalman filter is used to estimate the state of the system. The numerical results are compared with those available in the literature. The obtained results show that the controller can play a big role toward damping out the vibration of the sandwich beam. It also shows the difference between the vibration of top face sheets and bottom face sheets because of the flexibility of the core and the situations of sensor and actuator on the top or bottom face sheets have an important role on the dynamic response of sandwich beam.
Solar Energy
hamideh Hoseini; ramin mehdipour
Abstract
Solar chimney power plants are plants based on solar thermal power including three parts of collector, chimney and turbine, which is able to produce electrical energy. One of the effective parameters in increasing the power production is the collector angles versus horizon. In the present study, a numerical ...
Read More
Solar chimney power plants are plants based on solar thermal power including three parts of collector, chimney and turbine, which is able to produce electrical energy. One of the effective parameters in increasing the power production is the collector angles versus horizon. In the present study, a numerical analysis of a solar chimney power plant for different angles of the collector (divergent, convergent and horizontal type collector) is proposed. The introduced numerical model uses mathematical models of heat transfer. In this regard, effect of various angles of the three considered collectors on temperature distribution and power production of the solar chimney is evaluated. Divergent type collectors produce more power than convergent and horizontal collectors, as they produce more velocity and mass flow rates. It will be shown that by increasing the angle of divergent-type collector (keeping the inlet height constant), the power production will be increased and the output temperature will be decreased, in a way that the angle variation of 0.8 to 1 will increase the divergent type collector output power by 11 % and will decrease the output temperature by 0.78%. In the other case, when the output height is kept constant and the collector angle changes, performance of the divergent type collector is better than the other two collectors. Power production in a constant mean height is shown to be 3 times and 1.5 times more than the convergent and horizontal collectors respectively.
Fluid Mechanics
Miralam Mahdi; Mostafa Shariatnia; Majid Rahimi
Abstract
Microbubbles are used in ultrasound imaging, targeted drug delivery, destruction of cancerous tissues, etc. On the other hand, the demographic behaviors of small bubbles under the influence of Ultrasound have not been fully detected or studied. This study investigates the effect of the radial distribution ...
Read More
Microbubbles are used in ultrasound imaging, targeted drug delivery, destruction of cancerous tissues, etc. On the other hand, the demographic behaviors of small bubbles under the influence of Ultrasound have not been fully detected or studied. This study investigates the effect of the radial distribution of Sonazoid microbubbles on frequency response. It is shown that the optimal subharmonic response is possible by controlling the size distribution. For this reason, the numerical simulation of the dynamic behavior of a coated microbubble is performed using MATLAB coding and the modified Rayleigh-Plesset equation. The Gaussian distribution is then applied, and the frequency response is investigated. It was shown that at a constant excitation pressure of 0.4 MPa and a standard deviation of 0.2, with increasing mean radius, the fundamental response increases. The subharmonic response increases reaches a peak value and decreases. This peak value occurs for frequencies of 4,6, and 8 MHz in the mean radius of 0.8, 1 and 1.6 μm. By increasing the frequency of excitation, it is transferred to a smaller mean radius. It is also observed that the fundamental and subharmonic responses are amplified by increasing the excitation pressure. Studies show that the optimal subharmonic response can be achieved for various applications by controlling the size distribution of microbubbles.
Optimization
Meraj Rajaee; Mina Jalali
Abstract
The solar tree is a combination of technology and art that is considered as the application of solar energy in the art of urban architecture. This study aims to combine solar technology with architectural style and art, to help urban beautification and investigate the increase in solar panels' efficiency ...
Read More
The solar tree is a combination of technology and art that is considered as the application of solar energy in the art of urban architecture. This study aims to combine solar technology with architectural style and art, to help urban beautification and investigate the increase in solar panels' efficiency by focusing on the optimal slope and no shading in the form of a new solar tree structure. In this paper, the best angle for placing panels on tree branches to increase Shiraz's maximum efficiency has been calculated. The best angle is done with the help of the NRI mathematical model. Also, the Fibonacci sequence, which originates from nature and real trees, has been used to minimize shadows on this tree. The panels' optimal slope calculations are performed using MATLAB software. Also, the monthly efficiency changes resulting from the optimal slope have been calculated and displayed. By analyzing the computational relationships and their implementation by PVsyst simulator, the optimal annual slope of solar panels obtained 30 degrees. By implementing it in the solar tree structure, the proposed annual efficiency of the model has increased by 12% compared to the fixed state. This article examines the technical methods of using solar systems in urban architecture with emphasis on integration methods. In the proposed and implemented solar tree model with the ability to adjust the optimal angle and beautify passages, parks and recreation centers, it is possible to charge electronic equipment such as mobile phones, tablets, and electric bicycles through clean solar energy.
Computational Fluid Dynamics (CFD)
Milad Darabi Boroujeni; Ehsan Kianpour
Abstract
In this study, cooling of a hot obstacle in a rectangular cavity filled with water-CuO nanolfuid has been examined numerically. This cavity has an inlet and outlet and the cold nanofuid comes from the left side of the cavity and after cooling the hot obstacle, it goes out from the opposite site. All ...
Read More
In this study, cooling of a hot obstacle in a rectangular cavity filled with water-CuO nanolfuid has been examined numerically. This cavity has an inlet and outlet and the cold nanofuid comes from the left side of the cavity and after cooling the hot obstacle, it goes out from the opposite site. All of the walls are insulated, and the SIMPLER algorithm has been employed for solving the governing equations. The effects of fluid inertia, magnetic field strength, volume fraction of nanoparticles, and the place of outlet on heat transfer rate has been scrutinized. According to the results, the average Nusselt number builds up as the outlet place goes down. In other words, when the outlet is located at the bottom of the cavity, the rate of the heat transfer is maximum. Moreover, by increasing the Reynolds number and volume fraction of nanoparticles, the average Nusselt number builds up as well.
Manufacturing Processes
Faiz Fawzi Mustafa; Sadoon Radi Daham
Abstract
Surface layer in many engineering applications is strengthened by ceramic grains where the main parts have higher structure toughness than the original material. This paper presents the effect of four process parameters that have been taken into consideration using Taguchi technique based on L9 orthogonal ...
Read More
Surface layer in many engineering applications is strengthened by ceramic grains where the main parts have higher structure toughness than the original material. This paper presents the effect of four process parameters that have been taken into consideration using Taguchi technique based on L9 orthogonal array. These parameters are;1) transverse speed, 2) type of nano- powders, 3) rotational speed, and 4) groove’s depth friction stir welding T-joints aluminum alloy 6061-T6. This work combines welding T-joint sections and creating MMNCs in welding region simultaneously. The predicted optimum parameters and their percentage of contribution are estimated, utilizing the analysis of variance and signal to noise ratio techniques, depending on tensile test in skin and stringers direction, and hardness test of the joint. Optical microscope and scanning electron microscope (SEM) analysis are used to verify the microstructure and dispersion of nano-powders in welding joint. The best ultimate tensile stress (UTSskin) equal to (177MPa) for the skin welded part was obtained at the optimal conditions of 1550rpm rotational speed, 15mm/min transverse speed, Al2O3 type of powder and 1mm groove’s depth. SEM micrographic for metal matrix nanocomposite of all nine experiments revealed that the nano-particles are irregularly dispersed in nugget zone due to one pass. The rotational speeds of 960rpm, the transverse speed of 15mm/min, type of powder TiO2, and groove’s depth of 1.5mm, give the greatest hardness value of 80HV in nugget zone. The analysis of variance shows that the groove’s depth is the most significant parameter in this investigation.
Computational Fluid Dynamics (CFD)
mohammad saeed sharifi; Miralam Mahdi; Karim Maghsoudi Mehraban
Abstract
The shape of the air flow in the interior is heavily influenced by the air distribution system and the way air enters and exits. By numerically simulating flow by computational fluid dynamics, one can determine the flow pattern and temperature distribution and, with the help of the results, provide an ...
Read More
The shape of the air flow in the interior is heavily influenced by the air distribution system and the way air enters and exits. By numerically simulating flow by computational fluid dynamics, one can determine the flow pattern and temperature distribution and, with the help of the results, provide an optimal design of the air conditioning system. In this study, a chamber was first constructed and the temperature distribution inside it was measured. There was a fan installed at the back of the chamber for drainage. At the chamber entrance, three inlet for entering the flow were considered. The air from the middle inlet was heated by a heater. To prevent heat loss, the body of the enclosure was insulated. Several temperature sensors were installed at certain positions of the chamber for temperature measurement. Using Fluent software, the model of a full-sized chamber was created. Meshing is a hybrid and was used as a boundary layer Mesh. The inlet and outlet temperature of the chamber and the air output rates as boundary conditions were used in the simulation. Numerical analysis for K-ε and K-ω turbulence models was performed and different wall conditions were investigated. The numerical simulation results were in good agreement with the measurement results. Using the K-ε turbulence model with a scalable wall function had a better accuracy than other models. Changes in velocity and temperature were presented in graphs and contours at different positions of the compartment.
Fluid Mechanics
Payam Rahim Masharei; Seyed Mostafa Hosseinalipour; Mohammad Javad moslemani
Abstract
Laminar mixing of glycerin in a chaotic mixer is carried by means of the blob deformation method. The mixer was a cylindrical vessel with two rotational blades which move along two different circular paths with a stepwise motion protocol. The flow visualization was performed by marking of the free surface ...
Read More
Laminar mixing of glycerin in a chaotic mixer is carried by means of the blob deformation method. The mixer was a cylindrical vessel with two rotational blades which move along two different circular paths with a stepwise motion protocol. The flow visualization was performed by marking of the free surface of the flow with a tracer. The effects of controlling parameters such as rotational speed of blades, blades length, and rotational speed amplitude on mixing efficiency and time were analyzed by measuring of the area covered by the tracer. The results revealed that increasing rotational speed intensifies stretching and folding phenomenon, and consequently better mixing can be obtained. Also, the better condition in flow kinematic was provided to blend as stepwise motion protocol with wider amplitude adopted. A reduction in mixing time could be observed as the blades with longer length were used. In addition, it was also found that the promotion of mixing by rotational speed is more effective than that of two other parameters. The quantitative data and qualitative observations proved the potential of proposed chaotic mixer in wide range of industrial processes including chemical reaction and food processing in which laminar mixing is required.
Meshless Numerical Methods
Rahim Shamsoddini; Bahador Abolpour
Abstract
One of the main problems in liquid transfer tanks is the sloshing phenomenon. This phenomenon, which is associated with regular or irregular liquid waves inside the tank, can cause many risks. One of the most widely applied methods to control the fluctuations caused by the sloshing phenomenon is the ...
Read More
One of the main problems in liquid transfer tanks is the sloshing phenomenon. This phenomenon, which is associated with regular or irregular liquid waves inside the tank, can cause many risks. One of the most widely applied methods to control the fluctuations caused by the sloshing phenomenon is the use of baffles. Baffles are usually installed vertically or horizontally on the inner wall of the tank. In uniform samples (simple baffle), the hydrodynamic force on the baffle is significant. Therefore, in this research, mesh baffle from the category of permeable baffles is introduced and tested, which can significantly reduce the hydrodynamic forces on the baffle. Therefore, in the present work, the sloshing phenomenon in a rectangular tank is first modeled by Smoothed Particle Hydrodynamics (SPH) and validated. Then, the tank with a simple baffle and mesh baffle are modeled and examined. During the numerical solution (in each time interval), the hydrodynamic forces acting on the baffles are monitored and extracted. The comparison of the obtained results shows that in addition to reducing the fluctuations of the sloshing phenomenon, the mesh baffle also creates a lower hydrodynamic resistance force.
Manufacturing Processes
Saman Khalilpourazary; jamal ahmadi
Abstract
Reaming is a common finishing process for improving the drilled holes surface quality. Choosing an appropriate finishing method in drilling process has a significant effect on the surface quality of holes and in decreasing the process total cost and time. In this study, four similar holes were drilled ...
Read More
Reaming is a common finishing process for improving the drilled holes surface quality. Choosing an appropriate finishing method in drilling process has a significant effect on the surface quality of holes and in decreasing the process total cost and time. In this study, four similar holes were drilled on the AISI 4340 workpiece with different two pair feed rates. The drilling process was performed with a conventional cutting fluid, an emulsion of water and ECOCOOL 3015 GS-W. The surface roughness values after drilling process were measured using a portable roughness tester. Then, two distinct sizes of alumina micro-particles were used in the cutting fluid discretely to perform finishing process of the holes with a specific cylindrical tool. A comparison of the surface roughness measurements after the finishing process showed a significant decrease in the arithmetic surface roughness and ten-point mean roughness values of the drilled holes. The values were very close to the surface roughness limits in reaming process of the holes.
Computational Fluid Dynamics (CFD)
Golchehreh Shajari; Morteza Abbasi; Mehran Khaki Jamei
Abstract
In this study, comprehensive numerical simulations were conducted to examine laminar pulsatile developing flows through flat channels. The developing velocity fields and the hydrodynamic entry length were explored for the Reynolds numbers from 20 to 200, and the low and intermediate non-dimensional pulsation ...
Read More
In this study, comprehensive numerical simulations were conducted to examine laminar pulsatile developing flows through flat channels. The developing velocity fields and the hydrodynamic entry length were explored for the Reynolds numbers from 20 to 200, and the low and intermediate non-dimensional pulsation frequency or the Womersley number (1.08 ≤Wo≤ 8.86). For all simulations, the pulsating amplification factor was considered from zero to one, (0 ≤A≤ 1), and to achieve more practical and relevant outcomes, time-dependent parabolic inlet velocity profiles were applied. The outcomes reveal that for the higher values of the pulsation frequency or the Womersley number (6 ≤ Wo ≤ 8.66), the maximum pulsatile entranced length during a cycle is close to the inlet length of the mean component of the flow. On the other hand, for the rest of the Womersley number range (1.08 ≤ Wo < 6), and high amplification factor (0.5 ≤ A), the value of the entrance length increases and is significantly different from the development length of the steady component. Moreover, the results demonstrate that the entry length correlates with the Womersley number through a power-law function, whilst it has linear correlations with the Reynolds number and the amplification factor. Further, using the result of the accomplished numerical study, a practical correlation of the entrance length is offered to be used in the design phase for any type of pulsatile flow through the flat channels.
Biomechanics
Faramarz Talati; AliAsghar Asghar Taheri
Abstract
Hyperthermia is one of the first applications of nanotechnology in medicine by using micro/nano magnetic particles that act based on the heat of ferric oxide nanoparticles or quantum dots in an external alternating magnetic field. In this study, a two-dimensional model of body and tumor tissues embedded ...
Read More
Hyperthermia is one of the first applications of nanotechnology in medicine by using micro/nano magnetic particles that act based on the heat of ferric oxide nanoparticles or quantum dots in an external alternating magnetic field. In this study, a two-dimensional model of body and tumor tissues embedded is considered. Initially, the temperature distribution is obtained with respect to tumor properties and without the presence of an electromagnetic field. Then, the effect of the electromagnetic field on the temperature distribution is studied. The results are compared with those of other papers. The results indicate that the use of the electromagnetic field causes a significant rise in the tumor temperature; however, the risk of damage to the healthy tissues surrounding the cancerous tissue seems to be high. Then, the micro/nanoparticles are injected into the tumor tissue to focus energy on cancerous tissue and maximally transfer the heat onto the tissue. The temperature distribution in the state is compared with the case with no nanoparticles and other numerical works. The results demonstrate that with the injection of nanoparticles into the tumor, the maximum temperature location is transferred to the center of the tumor and also increases to 6°C. After determining the temperature distribution in the presence of nanoparticles, the effects of different variables of the problem are studied. According to the obtained results, the increase in the concentration and radius of nanoparticles have a positive effect on the temperature distribution in the tissue; on the other hand, the increase in the frequency and size of the electrodes have a negative effect. The relevant equations are solved numerically using the finite difference method.
Power Generation
Rehena Nasrin Nasrin; M. Saddam Hossain
Abstract
Photovoltaic (PV) module is one of the most useful, sustainable and non-harmful products in the field of renewable energy. It offers longer service period for least maintenance cost. The elements of PV are abrasive, easy for designing, and their structure like the stand-alone technique gives production ...
Read More
Photovoltaic (PV) module is one of the most useful, sustainable and non-harmful products in the field of renewable energy. It offers longer service period for least maintenance cost. The elements of PV are abrasive, easy for designing, and their structure like the stand-alone technique gives production from micro to mega-power level. A 3D numerical system of PV module has been built up and solved applying FEM technique-based software COMSOL Multiphysics in this article. The average solar irradiation and optimum tilt angle for six divisions (Dhaka, Chittagong, Rajshahi, Khulna, Barishal and Sylhet) in Bangladesh have been calculated. The effects of solar radiation, angle of inclination, ambient temperature, and partial shading on temperature of solar cell, electrical power and PV module's electrical efficiency have been investigated. It has been observed from the results that the greatest value of electrical power 15.14 W is found in Rajshahi for solar radiation 209 W/m2. The highest electrical efficiency is found as 12.85% in Sylhet at irradiation level of 189 W/m2. For every 1° increase of inclination angle, electrical power and electrical efficiency level devalue by 0.06 W and 0.05%, respectively. Results also show that the efficiency level decreases from 14.66 to 11.32% due to partial shading area from 0 to 40%. PV module's electrical power; and electrical efficiency reduces approximately 0.01 W and 0.01%, respectively due to every 1°C addition of solar cell temperature.
