Showing 6 results for Sabetghadam
Volume 15, Issue 7 (Supplementary Issue - 2013)
Abstract
Interaction of menthol with polyethylene terephthalate bottles during storage time was tested at three different temperatures. Menthol is a mint flavor agent added to yogurt drinks in Iran and is considered as a factor affecting consumer acceptance. Absorption of menthol to packaging material could cause a loss of quality in the final product due to diminished flavor intensity. Tests were done on the effects of environmental conditions (storage for three months at temperatures of 4, 25, and 45°C) on flavor stability of yogurt drink samples. Absorbed flavor was extracted from PET bottles after the specified time periods and quantified using gas chromatography coupled with FID detector. Then, the diffusion coefficient of menthol into PET bottles (Dp) was determined using concentrations of absorbed menthol. Results showed different absorption levels under various conditions. After 90 days, the absorption quantities at 4, 25, and 45°C were 38.21, 186.66 and 700.50 ng g-1 of PET bottle, respectively. It was concluded that amounts of menthol absorption into PET bottles increased with storage time and higher temperature. Elevation of storage temperature resulted in significant increase in diffusion coefficient of menthol in PET bottle.
Hamoon Pourmirzaagha, Vahid Esfahanian, Fereidoun Sabetghadam, Farshad Torabi,
Volume 15, Issue 9 (11-2015)
Abstract
In this paper, one-dimensional numerical optimization of lead-acid battery with finite-volume method is performed using the governing equations of battery dynamics. For validation, the present results are compared with previous studies which show good agreement. The demand for batteries with high energy and power has increased due to their use in hybrid vehicles.The major shortcoming of lead-acid batteries in industry is low energy and high weight; therefore, a cell with higher energy and lower thickness is designed by using particle swarm optimization based on developed simulation code which is less time consuming and much faster than experimental method. The results of optimization show that an optimal battery that has 85 percent higher energy can be made with the same cell length. The results also show that an optimum cell battery can be obtained with a decrease of 25 percent in weight and 23 percent in dimensions while keeping the energy content constant.
Fereidoun Sabetghadam, Abdullah Shajari-Ghasemkheily,
Volume 17, Issue 10 (1-2018)
Abstract
A new method is proposed for implementing the no-slip/no-penetration conditions on the irregular immersed boundaries in the vorticity-streamfunction formulation of the incompressible viscous fluid flow. Time integration is performed using a semi-implicit method such that in each time step the vorticity-streamfunction equations are changed to a Helmholtz and a Poisson’s equation. Some singular source terms are added to the right hand sides of these equations, in the solid region, such that the desired boundary conditions can be satisfied. The singular source terms are found, using the inverse problems method, such that the desired boundary conditions of the vorticity-streamfunction equations be satisfied. Since the fast Poisson’s solvers are used, the method is high performance, with the computational effort of O(NlogN); and it is also flexible because it can be applied easily to the complex geometries. The method is applied in simulation of the fluid flow around a square solid obstacle, placed in a channel, and the agreement of the results with the other benchmark results are shown.
M.a. Badri, F. Sabetghadam,
Volume 19, Issue 5 (May 2019)
Abstract
In the present paper, a new penalization method is proposed for implementation of the rigid surfaces on the Navier-Stokes equations in the vorticity-stream function formulation. In this method, a rigid body is considered as a region in the fluid flow, where the time is stopped. Therefore, by stopping the fluid particles, this region plays the role of a rigid body. In this regard, a new transformation is introduced and applied to the governing equations and a set of modified equations are obtained. Then, in the modified equations, the time dilation of the solid region is approached to infinity, while the time dilation of the fluid region remains In the article, the physical and mathematical properties of modified equations are investigated and satisfaction of the no-slip and no-penetration conditions are justified. Then, a suitable numerical algorithm is presented for solving the modified equations. In the proposed algorithm, the modified equation is time integrated via the Crank–Nicolson method, and the spatial discretization with the second-order finite differencing on a uniform Cartesian grid. The method is applied to the fluid flow around a square obstacle placed in a channel, the sudden flow perpendicular to a thin flat plate, and the flow around a circular cylinder. The results show that the no-slip and no-penetration conditions are satisfied accurately, while the flow fields are also high level of accuracy.
M. Fadaei, A. Davari, F. Sabetghadam, M.r. Soltani,
Volume 20, Issue 9 (September 2020)
Abstract
Wind turbines are one of the most important renewable energy production devices and improving their efficiency leads to more effective exploitation of clean energies. Flow separation on wind turbine blade is one of the major reasons of performance loss in wind turbines. The present paper investigates the effect of single dielectric barrier discharge plasma actuator (SDBD) placement on a critical section of wind-electric wind turbine blade (660kW)) designed inside country. An experimental investigation for assuring the validity of the numerical simulations has been performed. Then, two dimensional simulations were extended to evaluate the effect of plasma actuator performance on flow characteristics. Numerical simulations are based on the latest enhanced electrostatic plasma actuator models. The fluid flow is incompressible and the free stream velocity is about 20m/s. The results clearly indicate that frequency and voltage increase can significantly correct the flow pattern in post stall condition. A linear pattern has been achieved between the frequency and aerodynamic coefficients variations. The best improvement for the range under investigation is more than 800% for aerodynamic performance and approximately 50% for separation point delay.
Volume 21, Issue 148 (June 2024)
Abstract
Effect of osmosis dehydration, ultrasonic and edible coating as the pretreatment before drying has been studied in order to improve the flavor of the product, reduce thermal damages, decrease interstitial water and ease of transferring mass. The response surface method was used to optimize the drying conditions of Pommelo slices by osmosis-hot air. The concentration of edible coating (0-2% w/v) and the time of applying ultrasound (0-30 min) and the concentration of sucrose (40-80% w/w) were evaluated as independent variables on the amount of moisture content, absorption of solids, weight loss and productivity coefficient of Pommelo slices as dependent variables. All process variables were linearly significant for all responses (P<0.01). The comparison of the optimization results of coated and uncoated Pommelo osmotic dehydration showed that at the optimal point, the maximum amount of carboxymethyl cellulose coating and the osmotic dehydration time and the concentration of the osmotic solution in the coated sample were calculated as 2%, 21.86 minutes and 57.75%, respectively. The highest values of water reduction, weight loss and efficiency coefficient were 0.09172 (g/100g of solid matter), 0.091% and 19.478 respectively in the coated sample, and the highest absorption of solids with a value of 0.0089 (g/100g of solids) was reported in the uncoated sample. The results showed that the use of coating reduces the absorption of solid.
