Showing 6 results for Cfd Simulation
Hamid Moradtabrizi, Amir Nejat,
Volume 15, Issue 10 (1-2016)
Abstract
In this paper, a useful method proposed for aerodynamic design of Megawatt wind turbine's blade based on Blade Element Momentum (BEM) theory. In this method first a preliminary design is done based on the ideal BEM and then a method have been offered for geometric modifications to approximate the geometry of the blade to a real and functionally one. The advantage of this method is that needed few design parameters that simplify the design procedure, however its results are in good agreement with 5MW NREL reference wind turbine assumed as validation case and show that with use of this method can achieve a good aerodynamic design. then the twist angle has been optimized using Genetic algorithm and Bezier curve with annual energy production (AEP) as the goal function. At the end, a 2.5 MW wind turbine has been design based on this method with considering the Lootak site specifications in province of Sistan and Baloochestan. Then 3D model of the blade has been made and CFD simulation applied on that for showing the designed turbine operation in real conditions and comparison with BEM method and there is acceptable compatibility between two analytical methods.
Seyyed Mohammad Reza Maleki, Behrooz Mohammad Kari, Mehdi Maerefat,
Volume 17, Issue 4 (6-2017)
Abstract
Courtyard has been recognized as one of main elements in the Iranian culture, architecture and building design. According to its micro-climate effect in improving thermal performance of building, courtyard has been considered as a considerable subject for many researches. This paper investigates the courtyard’s design parameters and geometric configurations in pre-design states for improving thermal performance and comfort. For achieving this point, in this research the influence of courtyard orientation, horizontal dimensions and other parameters related to geometry have been evaluated. Due to micro-climate effect of courtyard on parameters related to thermal comfort, three main geometric layouts such as closed, semi-closed and open geometry have been investigated and compared by CFD simulations in ENVI-met software. The thermal comfort parameters are also investigated through comparing mean PMV in all simulations cases, using Fanger’s extended model. The results showed that thermal performance of closed shaped courtyard is better than other layouts. Also the comparison of results related to different aspect ratios (length to width ratios), put into evidence that thermal performance improves as the aspect ratio gets close to 1. That means as the courtyard shape encloses to square, the thermal performance improves and the mean air temperature in the investigated microclimates declines. To determine best configuration for Tehran’s climate, the results showed north-south orientation of building and increase of the height of the courtyard, are the two most appropriate considerations that will directly improve the thermal performance and comfort, specifically in closed and semi-closed layout.
Amir Heidari,
Volume 18, Issue 8 (12-2018)
Abstract
In this contribution, behavior of gas phase distribution in a two phase gas-liquid stirred vessel with Rushton turbine was studied by computational fluid dynamic (CFD) technique at different operational conditions. Multiphase flow regime in the in the two phase gas-liquid vessel was modeled by Eulerian-Eulerian multiphase flow approach. Due to complex hydrodynamics and turbulent flow in the agitated vessel, RNG k-ε was used to simulate turbulence flow behavior. With study of operational conditions by means of Aeration and impeller Reynolds dimensionless numbers, distribution of gas phase volume fraction was studied in the vessel. The results showed minimum hold up of the gas phase exists between vessel bottom up to impeller and maximum gas phase hold up is formed in the impeller zone. Also, it was observed due to the formation of larger vortex areas with increase in impeller Reynolds number the mixing quality in the vessel improves. Furthermore, it was shown that increase in Aeration and impeller Reynolds numbers enhances gas phase holdup in the vessel. Study of impeller Power number showed that with increase in Aeration number the amount of mixing power is reduced at constant Reynolds number. Also, it was observed that increase in Reynolds number enhances power consumption at constant Aeration number.
B. Sharifi, S.h. Hashemabadi,
Volume 19, Issue 6 (6-2019)
Abstract
In the present study, CFD simulation of Transit-time ultrasonic flowmeter with the PZT-5J piezoelectric sensor was modeled for light, heavy, and medium crude oil by the wave equation in the acoustic wave propagation path and finite element solving method in the unsteady state and it was implemented, using COMSOL Multiphysics 5.3 software. Different samples of light, heavy, and medium crude oil at different temperatures were modeled and simulated under constant pressure, using CFD tools. voltage and speed of sound in were calculated by the proposed model. To evaluate the accuracy of the proposed model, the simulation results were compared with the empirical data obtained from the experimental work of the researchers. The average values of the maximum voltage of signals for an ultrasonic containing light, heavy, and medium light crude oil samples are 0.9491, 1.0115, and 0.943 v, respectively. The difference between the simulation results and the experimental data for the speed of sound in the light, heavy, and medium crude oil samples was at most about 0.2336%, 0.4339%, and 0.1378%, respectively. Therefore, the high costs of designing and optimizing the transit-time ultrasonic flowmeter for crude oil can be reduced, using the proposed model.
B. Rahmati, S.h. Hashemabadi, M. Salemi Mojarrad,
Volume 20, Issue 7 (6-2020)
Abstract
The present study is a numerical model for prediction of turbine flowmeter performance, using the equation of motion based on torque balance theory. In this model, numerical simulations were carried out for a 2-inch diameter G65 and PN/ANSI 150 gas turbine flowmeter which was made by Vemmtec Company, in steady state, using Multiple Reference Frame (MRF) model and Standard k-ε turbulence model using Fluent software. In order to model torque balance equation and calculate angular velocity of rotor, a UDF (User Defined Function) code was created and was added to the software. To evaluate the model's accuracy, simulation results were compared with experimental data which was obtained from manufacturer of the meter. The difference between the simulation results and experimental data was 0.16%, approximately, which indicates the validity of the proposed model in simulating of turbine gas flowmeter performance. The results obtained from the simulation depicted that the velocity distribution asymmetry was more than 0.4Qmax at the downstream of the meter, and because this phenomenon had no negative effect on flow measurement, the suitable length for the flow development for the downstream of meter was done using simulation at least 10 times the diameter of the pipe was proposed. Therefore, using the proposed model, the capital cost of design and optimization of turbine flowmeters can be reduced.
H. Farahzadi, S.h. Hashemabadi, M. Shirvani,
Volume 20, Issue 9 (9-2020)
Abstract
Using vortex flowmeter is affordable, in addition, simple installation, high reliability, and high accuracy are some advantages of the vortex flowmeter. Vortex flowmeter works based on the vortex shedding principle, hence, the presence of particles in gas-solid flows may results in modulation in the turbulence intensity of the carrier phase and manipulate vortex shedding generated by a bluff body. In this study, the performance of the vortex flowmeter in the presence of particles with different sizes, density, solid volume fraction, and solid mass loading was studied with CFD simulation. The results indicated that the volume fraction and particles diameter are two significant parameters that affect vortex frequency. The vortex frequency is proportional to the velocity of gas flow and volume flow rate is calculated by Q= VA where V is average velocity in a pipe section with the area of A. Notwithstanding the neutral effect of microparticles on vortex frequency, moderate particles lessen the vortex frequency approximately by 20%. To coincide with the increase of solid volume fraction, the vortex frequency will descend, and in the high level of solid volume fraction, the vortex pattern goes to reach the instability. Since the size and volume fraction of the particles affects the frequency and consequently velocity, the gas flow rate measured by the vortex flowmeter is influenced by the presence of the particles. The numerical results have been validated with experimental data. The maximum relative error between the numerical simulation and the corresponding experimental data is 0.46% and 6.72 % for single-phase and gas-solid two-phase flows, respectively.
