Showing 4 results for Saghafian
Volume 11, Issue 3 (Number 3 - 2009)
Abstract
Runoff estimation is one of the main challenges encountered in water and watershed management. Spatial and temporal changes of factors which influence runoff due to het-erogeneity of the basins explain the complicacy of relations. Artificial Neural Network (ANN) is one of the intelligence techniques which is flexible and doesn’t call for any much physically complex processes. These networks can recognize the relation between input and output. In this study ANN model was employed for runoff estimation in Plaszjan Riv-er basin in the central part of Iran. The models used are Multiple Perceptron (MLP) and Recurrent Neural Network (RNN). Inputs include data obtained from 5 rain gauges as well as from 2 temperature recording gauges, the output of the model being the monthly flow in Eskandari Hydrometric Station. Preprocessing of the data as well as the sensitivity analysis of the model were carried out. Different topologies of Neural Networks were cre-ated with change in input layers, nodes as well as in the hidden layer. The best architec-ture was found as 7.4.1. Recurrent Neural Network led to better results than Multilayer Perceptron Network. Also results indicated that ANN is an appropriate technique for monthly runoff estimation in the selected basin with these networks being also of the ca-pability to show basin response to rainfall events.
Mohsen Behnia, Mahdi Nili Ahmadabadi, Mohsen Saghafian,
Volume 13, Issue 14 (Second Special Issue 2014)
Abstract
In this study, the radial flow turbine of a cooling turbine is investigated numerically and then compared with the experimental results at some operation conditions. Performance characteristics of the compressor are obtained experimentally by measurements of rotor speed and flow parameters. In this investigation, the turbine performance curve is obtained and three dimensional flow field in the turbine is analyzed. The rotor and casting geometry are modeled in BLADE GEN and CATIA softwares respectively. The TURBO GRID software is used for grid generation of rotor while the ANSYS MESH software is applied for grid generation of casting. Finally, 3D numerical solution of fluid flow in the turbine is solved by CFX flow solver. In this approach, compressible flow equations are solved according to the pressure based method with SST turbulence model. To ensure the numerical results, the grid independency is studied. Finally, the performance characteristics of the turbine are obtained numerically which are then compared to the experimental results. The comparison shows good agreement between numerical and experimental results.
Seyed Ali Kazemi, Mahdi Nili Ahmadabadi, Mohsen Saghafian, Ahmad Sedaghat,
Volume 15, Issue 1 (3-2015)
Abstract
The ratio of lift to drag coefficient in wind turbine blades is within the most important parameters affecting the power coefficient of wind turbines. Due to the performance of Magnus wind turbines in low speed air flow; such turbines are attractive for research centers. In the present work, a new geometry for the blades of Magnus wind turbines is defined. The defined geometry is based on the geometry of a Treadmill with a difference that the diameter of its leading circle is greater than that of its trailing one. In the present work, the body is supposed to a low speed air flow while a tangential velocity is applied to the airfoil surfaces and then, its effect on the lift and drag coefficient is studied by numerical method. The effect of generated tangential velocity on the surfaces is investigated for different air flow speed and attack angles and then, its results are compared with that for stationary surfaces. The results show that generating tangential velocity along the surfaces caucuses the lift and drag coefficients and, their ratio to be varied, greatly. By the tangential movement of the surfaces, the maximum ratio of lift to drag coefficient occurs in zero attack angle which is equal to 109. Moreover, maximum magnitude of lift to drag coefficient for attack angles 5, 10, and 15 degrees are 81, 64, and 57; respectively.
H. Aghaie, M. Saghafian, D. Saedi,
Volume 19, Issue 12 (December 2019)
Abstract
Today, the use of ultrasonic waves is expanding to the separation of particles or cells. One of the effective factors in the separating is cell deformation caused by ultrasonic waves. The most popular models used for deformation are the elastic and viscoelastic models. In this research, the cell has been modeled in a fluid environment under the influence of ultrasonic waves and deformations has been obtained. For this purpose, the Helmholtz equation that is a combine of the disturbance equations of sound waves and Navier-Stokes equation is solved and acoustic pressure is obtained. This pressure is then applied to the cell as deformation agent and the deformation is obtained using fluid-solid interactions modeling. Initially, deformation of the cell with elastic properties has been presented and validation has been conducted using comparison with the previous experimental researches. Finally, the deformation for the viscoelastic cell, which has so far not been used for deformation modeling in the acoustic field, has been obtained and presented. The results show that the viscoelastic model has the most compatibility with the experiment results. Also, the effect of frequency on the aspect ratio has been investigated. As the frequency ranges increased from 2 to 8 MHz, the aspect ratio is increased to 0.3.
