1
2251-600X
Isfahan University of Technology
115
General
Forced Convection Heat Transfer of Non-Newtonian Fluids Through Circular Ducts
S. Gh. Etemad
1
7
1998
17
1
1
12
25
10
2014
The Galerkin finite element method is used to solve the three dimensional continuity, momentum and energy equations for laminar Newtonian and power-law model non-Newtonian flow through horizontal circular tube. The governing equations are non-dimensionalized with respect to specific variables and converted into algebraic equations using appropriate elements. To accelerate convergence a combination strategy of fixed iteration and Newton-Raphson methods are employed. Uniform wall temperature as well as constant wall heat flux are used as thermal boundary conditions. Apparent friction factor and incremental pressure drop and also Nusselt number are obtained for a wide range of power-law indices. The effects of thermal boundary conditions and Prandtl number on heat transfer characteristics are presented and discussed.
116
General
Simulation of a Two Cards JIT Production System
M. Aghdasi
F. Mokhatab Rafiei and G. Moslehi
1
7
1998
17
1
13
31
25
10
2014
This paper presents a summary of the results from the simulation of a given two-stages production system which uses JIT. The system consists of an assembly line with two automated assembly cells and two assembly stock points and one manufacturing cell with three manufacturing stock points for storing reserved parts and one receiving stock. Carts with fixed capacity are used for handling the parts. A kanban is attached to each cart. The minimum number of kandbans required to operate the system without shortage in stock are estimated. The effects of changing the demand's mean and its variation on the number of carts are also investigated. Finally, a different simulation model is developed for the same production system using conventional job shop decipline and some main characteristics have been compared to the results, from the first model.
117
General
A Fuzzy Algorithm for the m-Machine, n-Job Flow Shop Sequencing Problem
A. Memariani
G. Moslehi
1
7
1998
17
1
33
41
25
10
2014
Flow shop sequencing problem is included in NP-hard problems and a number of heuristic methods have been developed to solve it. Most of these methods are offered for the crisp processing time. However fuzzy algorithm is appropriate for the problems with fuzzy processing time. This paper presents a method in which an algorithm is used to minimize make span of flow shop with fuzzy processing time by taking advantage of fuzzy mathematics. This method is based on the behavior of the decision maker who can make either pessimistic or the most likely decisions. The algorithm includes proper relations and corresponding results.
118
General
Analysis of Tall Buildings with Bundled Tube System Subjected to Wind and Earthquake loads
K. Mirtalaei and S.S. Mahini
1
7
1998
17
1
43
52
25
10
2014
At present, the tubular structural systems are mainly used in tall buildings to withstand earthquake loads. Although it is possible to analyse the structure by finite element methods using standard three dimensional programs, the system is generally time-consuming and expensive in the primary design work. In this paper, for the analysis of Framed-Tube systems, a simple method was studied and developed for Bundled-Tube systems and corresponding formulas for horizontal and vertical deflections were obtained. By replacing the discrete structure with and equivalent tube or replacing the multicell tube with orthotropic plates and making simple assumptions regarding the stress distributions in the structure, simple Closed-Form solutions using the were obtained. Standard load cases including uniformly distributed load, triangularly distributed load, and point load at the top were applied. By this method, a new computer program was developed, called TSAP (Tubular Structural Analysis Program). The <> results were compared with more accurate results obtained by famous finite element computer programs. The runtime for this program was about 2% of the runtime for other existing programs.
119
General
Evaluation of Seismic Behaviour of Ferrocement Elevated Water Tanks by Using Ambient Vibrations Tests
H. Shakib
1
7
1998
17
1
53
69
25
10
2014
In this study a series of ambient vibration tests on the triple ferrocement elevated water tanks with 150 cubic meters volume, is carried out. In order to verify the dynamic characteristics of full, half-full and one full tanks (mass eccentric system), the different arrangements of sensors are used. The effects of base rotation are also considered in the tests. Natural frequencies and mode shapes obtained from tests are compared to the mathematical model of the tanks using finite element method. In order to verify the effect of different assumptions on the design forces, the revised mathematical model is analyzed by spectral method. The results indicate that base rotation causes the change of design forces especially in the vicinity of the base of system.
120
General
Analysis of Thin-Walled Structures Using Torsional-Bending Elements
H. Haji-Kazemi and M. Arab
1
7
1998
17
1
71
83
25
10
2014
In this paper a new element for analysis of thin-walled structures is presented, and the effects of secondary shear stresses on longitudinal displacements are examined. Since the Interpolation Functions are based on non-uniform torsional differential equations, the analysis of stiffness matrix is facilitated. Therefore, its ability to produce accurate results with the least number of elements is considerably improved. Furthermore, this element can be used in the analysis of all kinds of thin-walled, straight or curved beams with open or closed sections.
121
General
Numerical Investigation of Fluid Flow Characteristics Around Slide Gates Using Multi-Zonal Method
B. Farhanieh
M. Golafshani and S. Ekrami
1
7
1998
17
1
85
107
25
10
2014
One method of solving the governing equations of fluid flow about complex geometries is to use multi-zonal method. In this method the overall domain is divided into small number of simpler domains. In each zone, the flow field is solved independently of other zones. The boundary conditions for connecting zones are enforced to convey the necessary linkage. This multi – zonal procedure has been applied into a finite- volume body – fitted code. This code employs collocated variable arrangement and Cartesian velocity components. The accuracy of the method was also established by comparing the calculated results with the numerical and experimental results available in the open literature of cavity flow and flow over a backward – facing step. The flow field around Alavian sliding gate is investigated using the present method. The velocity vectors, streamlines and pressure contours are plotted for various opening ratios of the gate. The drag forces induced due to the pressure field around the gate were calculated and compared with the experimental data.
122
General
Turbulent Flow in 2-D Domains with Complex Geometry-Finite Elelment Method
M. S. Sadeghipour and R. Razmi
1
7
1998
17
1
109
120
25
10
2014
Using the highly recommended numerical techniques, a finite element computer code is developed to analyse the steady incompressible, laminar and turbulent flows in 2-D domains with complex geometry. The Petrov-Galerkin finite element formulation is adopted to avoid numerical oscillations. Turbulence is modeled using the two equation k-ω model. The discretized equations are written in the form of a set of nonlinear equations by block implicit method and are then linearized by the Newton-Raphson method. The set of linearized equations are, finally, solved Through Frontal method. This generates a full implicit solution. A few laminar and turbulent flow sample problems are solved using the code. Results obtained are in perfect agreement with those obtained from numerical and experimental works reported in the literature.
123
General
A General New Algorithm for Regulaization of Singular Integrals in Three-Dimensional Boundary Elemnts
D. Derakhshan and G. Karami
1
7
1998
17
1
121
132
25
10
2014
In this paper an algorithm is presented for the regularization of singular integrals with any degrees of singularity, which may be employed in all three-dimensional problems analyzed by Boundary Elements. The integrals in Boundary Integrals Equations are inherently singular. For example, one can mention the integrals confronted in potential problems to evaluate the flow or the gradient of the flow or the integrals employed to determine the stress or the deformation in elastic problems. Having only the numerator functions and their derivatives derived either explicitly or implicitly, this algorithm may be employed to evaluate the strongly, hyper or supersingular integrals with a satisfactory of accuracy. To regularize the integrals, some functions are either added or subtracted successively so as to differentiate the singular and nonsingular terms. Three examples with their numerical solutions are included which show the efficiency and the accuracy of the proposed algorithm.
124
General
Longitudinal and Transversal Vibration Response of Beams by Statistical Energy Analysis (SEA)
E. Esmailzadeh and A. R. Ohadi
1
7
1998
17
1
133
142
25
10
2014
The useful and efficient method of Finite Element (FEM) has a drawback for dynamic analysis of complex structures, especially in the medium and high frequency range. To overcome this fundamental difficulty, application of Statistical Energy Analysis (SEA) and power flow technique has been suggested. As the SEA is based on the average response of structure and statistical properties of its resonant modes, SEA is found to be effective in cases like high modal density, high modal overlap and in short wave length. In these cases, the average response is found to be both real and an acceptable value, contrary to the FEM which is not accurate enough.;#10In this study, the fundamental difficulties of FEM in the high frequency range are explained and then the advantages and applications of SEA and power flow technique are presented. Moreover, a description of SEA basis, fundamental concepts of General Energy Method (GEM) are explained and formulated to be used in the longitudinal and transversal vibrations of beams. Finally, by satisfying the energy boundary conditions, the energy flow analysis of rods and beams with elastic support and under harmonic excitation are investigated.;#10
125
General
Increasing Cooling Towers Heat Capacity by Flue Gas Introduction
A. Nouri
1
7
1998
17
1
143
152
25
10
2014
In this paper the changes in the heat capacity of cooling towers has been investigated as a result of injecting combustion products of boilers. In the tower, the air is re-heated through mixing with hot flue gas after passing through the heat exchangers. As a result of this process, the draft of the cooling tower is increased. The additional produced draft depends on the ambient temperature and the amount of heating.;#10The results of the study show that the heating process is more effective in the hot weather than in the cold weather.;#10
126
General
Experimental Investigations into the Collapse of Simple and Reinforced Thin-Walled Channel Beams under Bending Loads
M. Salimi and H. Khademizadeh
1
7
1998
17
1
153
164
25
10
2014
In this paper, collapse behavior of simple and reinforced thin-walled channel- section beams, subjected to three- point bending, is investigated. Many simple channel- section beams of different geometry and some reinforced ones were tested, and their strengths after collapse were obtained thoroughly. Since the available theories in this area are complicated and little attention has been paid to the case of reinforced thin-walled beams, simple models were used and further developed to give an account of the collapse load and the deformation energy of such beams. The method proposed in this paper is valuable both to the further studies of the symmetric thin-walled beams with arbitrary cross-section and to its practical application of such beams as energy absorbers.
127
General
Extraction of Vanadium Oxide from Boiler Fuel Ash
M. H. Abbasi and M. Safarnoorallah
1
7
1998
17
1
165
175
25
10
2014
Fuel oil used in power plants contain metal impurities like Vanadium. After combustion, this metal remains in boiler fuel ash in the form of oxide. In this research, extraction of Vanadium oxide from fuel ash has been investigated. Two processes were used for this purpose. A pyro- hydrometallurgy and a hydrometallurgy process. In the pyro-hydrometallurgy process, using sodium carbonate, salt roasting of the ash followed by water leaching was carried out. Vanadium was then precipitated as ammonium vanadates which on heating decomposed and vanadium pentoxide (V2O5) was obtained. In the hydrometallurgy process, the ash was dissolved in sodium hydroxide. Vanadium oxide was then recovered from solution. Effects of various parameters in each case were investigated and the optimum condition for maximum recovery was determined.
128
General
Comparison of Carburizing and Boronizing Processes on Mechanical and Wear Properties of PM Parts
F. Ashrafizadeh
M. R. Toroghinezhad
1
7
1998
17
1
177
186
25
10
2014
In this study carburizing and boronizing processes were applied to powder metallurgy steel specimens and the mechanical and tribological properties of the substrate and coatings were evaluated under various process conditions.;#10The specimens, made from industrial test pieces, were carburized in a powder pack for a duration of 2-5 hrs at 850-950 ˚C. Similar specimens were pack boronized for 4 hrs at 950 ˚C. The effect of austenitization-quench treatment was also investigated on some specimens. The wear tests were carried out by means of a pin-on-disc tribotester against ball bearing steel.;#10The results indicate that by appropriate selection of process parameters it is possible to obtain high wear resistance together with moderate toughness. Boride layers with hardness values of 1700HV are properly formed on PM samples. The wear resistance, therefore, is significantly increased with practically no reduction in impact resistance. It is concluded that boronizing treatment can be more suitable for some PM parts under tribological conditions.;#10
129
General
An Algorithm for Color Matching of Textiles With Elimination of Limitation on Primaries
H. Khalili S. H. Amirshahi
1
7
1998
17
1
187
196
25
10
2014
The proposed algorithm suggests a new method for determination of K/S value of primaries based on linear least Squares Technique. By applying the matrix pseudoinverse, a modification is introduced to eliminate the limitation on the numbers of applied dyes in one – constant Kubelka-Munk theory. The selection of dyes for tristimulus matching are also done on the basis of the initial spectrophotometric results. The applicability of suggested methods are tested through a computer colour matching attempt with more/less than three primaries.
130
General
Off-Design Performance Prediction of Jet Engines
A. R. Azimian
1
7
1998
17
1
197
202
25
10
2014
In this paper it is attempted to predict the off-design performance of a jet engine. After a review of the governing equations, the off-design performance is investigated by two methods. In the first method, the component characteristic curves of the Gas Turbines are used. In the second method some design point parameters and the reference state conditions are employed. The results obtained by this two methods fairly agree, and therefore, the second simple method which is independent of the component characteristics are recommended.