2018-01-23T07:39:32Z
http://miscj.aut.ac.ir/?_action=export&rf=summon&issue=26
AUT Journal of Modeling and Simulation
2588-2953
2588-2953
2011
43
1
Numerical Simulation of Random Irregular Waves for Wave Generation in Laboratory Flumes
Mohammad Janvad
Ketabdari
Ali
Ranginkaman
Understanding of wave hydrodynamics and its effects are important for engineers and scientists. Important insights may be gained from laboratory studies. Often the waves are simulated in laboratory flumes do not have the full characteristics of real sea waves. It is then necessary to present reliable methods of wave generation in wave flumes. In this paper, the results of numerically simulated water waves using different methods are presented. A model was developed to simulate water wave profile using DSA, NAS and WNDF methods. The results showed that although DSA method provides better agreement between output and target spectra, it is associated with non realistic simulation of sea waves. In the other hand WNDF method involves better stochastic wave characteristics if a qualitative white noise is used. It is also possible to put some controls on wave characteristics as input to WNDF model.
Random Irregular Waves
DSA Method
NSA Method
WNDF Method
White Noise
2011
04
01
1
6
http://miscj.aut.ac.ir/article_140_fa0b4143256098fc69283eb747efd615.pdf
AUT Journal of Modeling and Simulation
2588-2953
2588-2953
2011
43
1
A multi Agent System Based on Modified Shifting Bottleneck and Search Techniques for Job Shop Scheduling Problems
M.H
Karimi Gavareshki
M.H
Fazel Zarandi
This paper presents a multi agent system for the job shop scheduling problems. The proposed system consists of initial scheduling agent, search agents, and schedule management agent. In initial scheduling agent, a modified Shifting Bottleneck is proposed. That is, an effective heuristic approach and can generate a good solution in a low computational effort. In search agents, a hybrid search approach is presented. The schedule management agent can manage the system. Finally, the proposed agent based system is tested and validated by some benchmark problems. The results show the superiority of the proposed system in terms of makespan minimization and CPU times.
Job shop scheduling
multi agent system
shifting Bottleneck
search technique
2011
04
01
7
15
http://miscj.aut.ac.ir/article_143_724d1b1a82659da8eb6622e82dce6879.pdf
AUT Journal of Modeling and Simulation
2588-2953
2588-2953
2011
43
1
Fuzzy Model of Human’s Performance for Guarding a Territory in an Air Combat
R.
Ghasemi
S.K.Y.
Nikraveshii
M.B.
Menhajiii
S.
Akbariiv
This paper proposes a new method for a three dimensional fuzzy model of pilot's performance for guarding a territory with a short-distance between two aircraft in an air combat task with a gun. A third-order nonlinear point mass vehicle model is considered for an aircraft's flight dynamics. The desired value of the velocity, the flight path and the heading angles are obtained from some derived equations and rule bases developed in this paper. The physical control parameters are computed through a mean square error scheme. To model pilot's performance and generate a complicated offensive maneuver in an air combat, we need to imitate pilot's decisions making performance. The proposed model shows promising performance in all scenarios in which two aircraft can hold in an air combat. This model employs a time optimal combination of classic pursuits when needed. This makes our model very powerful. We consider two cases for modeling, the first one is the model of the pilots with constant specific energy and the other is with time varying specific energy. Finally, this paper proposes a new 3-Dimentional flight simulator.
Fuzzy modeling
Guarding a territory
Pilot's performance
Maneuvering Offender
Pursuit Evasion Game
flight simulator
2011
04
01
17
24
http://miscj.aut.ac.ir/article_144_642b65db77b3f0141362b2f3450d1e38.pdf
AUT Journal of Modeling and Simulation
2588-2953
2588-2953
2011
43
1
Numerical Simulation and Parametric Study of Forced Convective Condensation in Vertical Channel
Forced convective condensation in vertical channel is investigated numerically. The condensation boundary layers that occur due to temperature difference between the walls and saturation temperature of steam is simulated by the volume of fluid (VOF) method. The effect of variations in the hydraulic diameter, steam velocity, Re number and temperature difference between the wall and saturation temperature of inlet steam on heat transfer coefficients are investigated. Simulation results showed that the condensation length and heat transfer coefficient increase by the increase in the amount of inlet velocity and Reynolds number of inlet steam. Also, it was seen a reduction in temperature difference between the wall and saturated steam.
Condensation
Numerical simulation
Vertical channel
heat transfer coefficient
2011
04
01
25
34
http://miscj.aut.ac.ir/article_146_34d014ffbcee7efc0e971af039f31fe8.pdf
AUT Journal of Modeling and Simulation
2588-2953
2588-2953
2011
43
1
Velocity Modeling in a Vertical Transversely Isotropic Medium Using Zelt Method
In the present paper, the Zelt algorithm has been extended for ray tracing through an anisotropic model. In anisotropic media, the direction of the propagated energy generally differs from that of the plane-wave propagation. This makes velocity values to be varied in different directions. Therefore, velocity modeling in such media is completely different from that in an isotropic media. The velocity model for ray tracing is parameterized in terms of blocky trapezoid cells where the velocity changes inside the cells linearly. Thomsen’s approximations in weakly anisotropic media were used to estimate anisotropic velocity vectors. Rays were traced in direction of group vector in the vertical transversely isotropic (VTI) media, whereas, the anisotropic Snell’s law must be satisfied by the phase angle and phase velocities across the interface. The synthetic examples are given to demonstrate and verify the ray tracing algorithm. Reflected and turning waves were traced through the isotropic and anisotropic velocity models. Lateral and vertical velocity variation caused deviation on trajectory of the traveltime curve. The results show that the difference between isotropic and anisotropic traveltimes increases with offset, especially when the ratio offset/depth exceeds 1.5.
Ray tracing
Vertical Transversely Isotropy (VTI)
Zelt method
seismic velocity modeling
2011
04
01
35
40
http://miscj.aut.ac.ir/article_148_01e619fc5e0d7d41d49814ee3261659b.pdf
AUT Journal of Modeling and Simulation
2588-2953
2588-2953
2011
43
1
Equation Chapter 1 Section 1 Analytical Solutions for Radially Functionally Graded Annular Plates
M. H.
Babaei
M.
Salehi
R.
Naj
A closed-form solution for deflections and stresses in an annular thin plate of radially functionally graded material under transverse uniform pressure loading is presented. The small displacement theory of elasticity is assumed in the present work. Young’s modulus of the material is taken in the form of a simple power law to vary in the radial direction with an arbitrary exponent showing heterogeneity of the plate, while Poisson's ratio is held constant throughout the plate. Deflection and stress distributions are graphically presented for various values of the heterogeneity exponent to illustrate its effects on the deflections and stresses. Through the current analysis, this exponent can be adjusted in actual designs to control the deflections and stress levels in a plate.
Annular plate
Functionally Graded Material (FGM)
Analytical Solution
2011
04
01
41
45
http://miscj.aut.ac.ir/article_151_43372749e8840af5d5cf964664970598.pdf
AUT Journal of Modeling and Simulation
2588-2953
2588-2953
2011
43
1
Water Management in the Cathode Side of a PEM Fuel Cell
N.
Khajeh-Hosseini D
H. R.
Shabgard
M. J.
Kermaniiii
A one dimensional isothermal mathematical modeling of cathode side of a Proton Exchange Membrane (PEM) fuel cell is developed for the water management problem. Water transport is investigated in both cathode Gas Diffusion Layer (GDL) and membrane through solving appropriate equations for fluid flow and mass transport in GDL and water transport within the membrane. The gaseous mixture flowing in cathode GDL consists of three species: oxygen, water vapor and nitrogen. The model considers one phase flow in the gas diffusion layer and then predicts the regions with possible condensation. Homogenous distribution of wet phase (liquid water) is assumed throughout each wet control volume as fog. The model couples all governing equations in both membrane and GDL using an innovative algorithm. A detailed discussion of numerical techniques for the PEMFC model is given with a flow diagram to provide an overview of the solution procedure. Validation for polarization curve is implemented to show agreement between the obtained results and existing results in the literature.
PEM fuel cell
Water management
Porous electrode
Stefan-Maxwell equation
2011
04
01
47
54
http://miscj.aut.ac.ir/article_154_a82f91f2fb309ca8a25b12c62f84b97b.pdf
AUT Journal of Modeling and Simulation
2588-2953
2588-2953
2011
43
1
Flexural Behavior of Cementitious Composites Reinforced by Synthetic Fibers
H. R.
Pakravani
M.
Jamshidiii
M.
Latifiii
The application of fibers to reinforce cementitious materials is a well-known subject. At first, asbestos fibers are used in industrial process to produce fiber reinforced cement sheets. Thereafter, various types of synthetic fibers are produced and used as asbestos substitutes. The aim of the present work is to evaluate the effect of synthetic fibers on the flexural behavior of cementitious composites. In this study, the flexural strength of cement-based materials reinforced by three different types of synthetic fibers (polypropylene (PP), polyamide 66 (PA66) and acrylic (PAN)) is studied at various volume contents. It was found that although PAN and PA66 improve maximum flexural load borne by the cementitous composite before failure, the PAN fibers improves toughness of cementitous composites about 30% more than PP and PA66 fibers.
Flexural behavior
Fiber
Cementitious composites
2011
04
01
55
61
http://miscj.aut.ac.ir/article_156_3d628cd3999ff64b2a55678c05104058.pdf