Articles in This Issue
Abstract
Numerical solutions are presented for mixed convection from an array of circular cylinders embed in a saturated porous medium. The cylinders are at constant temperature(isothermal) and arranged in a staggered tube bank. Both aiding and opposing flow conditions are considered. Numerical calculations using finite difference method with body-fitted coordinates have covered a wide range of governing parameters(i.e.,10 ،ـ Re ،ـ 100, 0 ،ـ Gr ،ـ 400 and Pr = 0.7). Results are presented for streamline, isotherms and the local and the average Nusselt number at different values of the governing parameters. The present results are compared with previous theoretical results and show good agreement
Abstract
This paper deals with a numerical investigation of natural convection of heat transfer in a horizontal eccentric annulus between a square outer enclosure and a heated circular inner cylinder. The governing equations are expressed by the term of the stream function-vorticity with dimensionless temperature. The body fitted coordinate system (BFC) was used to stretch over the physical domain of the presented problem. The Poission's equation of stream function is solved by successive over relaxation (SOR) method, while time marching technique was the best choice to solve both vorticity and energy equation.The results are presented for the streamlines and isotherms as well as the average Nusselt number at different eccentricities and angular positions. Comparison with previous theoretical results shows good agreement.
Abstract
Free vibration analysis of a cracked cantilever beam with two types of additional substructure attachment is investigated using ANSYS program. The cantilever beam is used as a master structure with single substructure attachment in various locations (as 1-DOF mass attachment and 1-DOF mass-spring attachment) with influence of crack in different location and depths. The results for the changes of the natural frequencies of a cracked beam are compared with the results produced by Vahit et al [1]. So the same geometrical properties have been studied. In additional work a cracked beam carrying two types of substructure attachment are compared with the results of the beam without a crack and with multi crack depth. In all calculations the beam has a uniform cross-section and the crack was modeled by reduction in the modulus of the beam. The reducing effects of the cracked beam on the natural frequencies had been more apparent with the substructure attached to the beam in different situations. The effect of mass-spring substructure is larger than the effect of the attachment when modeled as mass substructure for the same mass, with 17% for the first natural frequency and 2% for the second and third natural frequencies. The results can be used to identify cracks in simple beam structure; cracks have a clearer decreasing impact on the natural frequencies.
Abstract
In this study an attempt is made to develop a method of analysis dealing with a multi-layer composite continuous beam , for linear material and shear connector behavior in which the slip (horizontal displacement) and uplift force (vertical displacement) are taken into consideration. The cross-sectional area for the beam consists of three layers varying in thickness and shear stiffness. The analysis is based on a approach presented by Roberts[1], basically for two layer simply supported beam, under uniform and point loads , which takes into consideration horizontal and vertical displacement in interfaces. The analysis led to a set of eight differential equations containing derivatives of the fourth and third order. A program based on the present analysis is built using finite difference method using boundary conditions. A comparison between the present analytical solution and previous studies shows close agreement. Continuous composite beams are very important element in construction of high rise buildings , multi-story frames and bridges, due to great advantages that can be obtained by using this sort of structural elements, such as reducing the beam moments, suitable reduction in deflections. The model deals with continuous beam consisting from three layers as a cross-sectional area with inter-layer slip. The cross-sectional area consist of composite material including intermediate layer from concrete and an upper and lower material with high strength in tension and compression ( i.e. steel plates or steel beams )
Abstract
The aim of current work is to investigate the tensioned composite plates with two types of cutouts. Many industrial applications use composite matrix with reinforcement fiber to obtain better properties. The objective of this work is divided into two parts, first the experimental work covers the measuring of the normal strain (εx) at the edges of (circular & square) holes that are perpendicular to the direction of the applied loads with different number of layers and types of cutouts of composite materials by using strain gages technique under constant tensile loads to compare with the numerical results. The second part is numerical work, which involves studying the static analysis of symmetric square plates with different types of cutout (circular – square). In static analysis, the effect of the following design parameters on the maximum stress (σx), strain (εx) and deflection (Ux) is studied. This part of investigation was achieved by using the software finite element package (ANSYS 5.4).
Abstract
The main objective of this study is to determine the effect of vortex generators on a friction factor for fully developed flow of a fluid such as air. Longitudinal vortices can be generated in a channel flow by punching or mounting protrusions in the channel wall. Such vortex generators (VGs) can be classified into delta wing, rectangular wing, pair of delta-winglet and pair of rectangular winglet. These longitudinal vortices disrupt the growth of the boundary layer and lead to enhance the heat transfer rate between the working fluid and the conductor channel wall, but this enhancement is associated with increasing in a pressure gradient along the axial length of the channel. So, the friction factor for fully developed air flow in an equilateral triangular duct is investigated experimentally with Reynolds number ranging from (31,000) to (53,000) and the size of the generators was kept constant for three cases which are single, double, and triple pairs of delta–winglet type of vortex generators embedded in the turbulent boundary layer for attack angle of generator of (30, 40, and 50 ) degree. The results show that the friction factor increases by about (43.5 %) when the angle of attack is varied from (30 deg) to (50 deg) for the triple pairs case compared with the base case (without VG).
Abstract
An experimental investigation as well as nonlinear analysis is carried out in this paper to study the behavior of polymer members (Epoxy & Polyester) under direct tension. The ANSYS model accounts for nonlinear phenomenon, such as, Tension Softening Material (TSM) and Enhanced Multilinear Isotropic Softening (EMIS) models. The polymer specimens are modeled using PLANE82 element – eight node plane element – eight node plane element, which is capable of simulating the failure behavior of polymer material members. The intention of this paper is thereby to discuss the proposed softening models to validate the complete Stress-Strain and Load-Deflection response of prismatic specimens subjected to uniaxial tension. The outcomes from the verifications of both modeling techniques have shown good agreement with the experimental results obtained from literature.
Abstract
In this study an attempt is made to derive governing equations satisfying equilibrium and compatibility, for multi-layer composite simply supported beam under blast loading , for linear material and shear connector behavior in which the slip (horizontal displacement) and uplift force (vertical displacement) are taken into consideration. The analysis is based on an approach presented by Roberts, which takes into consideration horizontal and vertical displacements in interfaces. The model consists of a simply supported beam with three layers having a cross-sectional area ,different dimensions and material properties. The analysis led to a set of six differential equations containing derivatives of the fourth and third order. The blast loading was considered as a function of time. Explosions have different effects including blast, penetrations and fragmentation. The blast is the main effect which hits the structure in short duration. Multi –layer composite construction is the best type of constructions to resist the blast loading ; according to this , multi-layer composite construction is used for air-craft and marine industries. Analysis of composite beam under blast load , taking in consideration vertical and horizontal displacements, leads to six differential equations , the load is taken as a function of time.
Abstract
A new technique is presented by which lateral outflows of material , from an oblique impact collision between wax projectile and a rigid surface , are collected to form a high speed single jet. This jet has been shown to be capable of producing cavities in semi-infinite target of wax in a manner similar to that produced in a hypervelocity impact situation. The produced jet capability of penetration is found to be maximum at higher velocities of impact , lower values of standoff and with projectiles having angle of obliquity in the range (â=20-25o). A preliminary theoretical model is also presented in an attempt to describe the process of jet creation and jet characteristics. The present technique is proved to be promising in simulating penetration of semi-infinite targets by the impact of high speed jet .
Abstract
The research is interested in the noise sources that occur inside the cities. That the human being are subjected inside there homes, the way it maybe transfer and the way to treat this problem and control it by achieving a good planning to the city before the construction starts. The architecture role appears when planning the cities by defining the best way to use the land for and find the practical balance between the noise pollution the land suffer from. And also to indicate the locations of the housing area. in addition to locate the external and internal noise sources and put successful solutions to treat and control it by planning and design. A housing area at AL-SAQLAWIA a city near AL-ANBAR TECHNICAL INSTITUT was studied by distributing a (100) questionnaires for the people living at this area to recognize their opinion about the noise sources inside and outside their homes and how far it affect their life to find a table with conclusion about this object which contain a comparison between the house location near the street and far a way the street and transfer the results into graphs to explain the relation between the noise sources and the percentage ratio for the opinions of the living people.
Abstract
The progress in technological earth observation field , using of satellite data and the development of computer software, lead to reduce effort and time to control the change in land uses especially after the increases in both accuracy and resolution of image data. This paper studies the urban development of falluja city since its construction (depending on the fact of land uses) and future directions for the development of the city. The above two trends are very important in supporting decisions of governorates, municipalities and government departments in the land uses management and control of building by using a new technique which treated with data and uses maps. The present study concluded that the use of remote sensing, geographic information system and mathematical models are very important to prepare master plan of cities with high efficiency.
Abstract
The complete of the architectural space consider the most interested side in meanings and what it contain . it is the space where the basic stamp for the architecture formation achieved as the acoustic performance was one of the functional articles that belong to some architectural spaces style , the research choose two rooms belong to the institute used as auditorium to study its efficiency about the availability of some important acoustic indicators that should be available in such kind of auditoriums to achieve the connection between the engineering design and the acoustical design for the auditorium elements to reach the required performance for the room to give comfortable impression . the research see to study some of the following indicators :- 1. Reverberation Time. 2. Loudness. 3. intelligibility of Speech and Articulation.
Abstract
The Cooper-Harper rating of aircraft handling qualities has been adopted as a standard for measuring the performance of aircraft. In the present work, the tail plane design for satisfying longitudinal handling qualities has been investigated with different tail design for two flight conditions based on the Shomber and Gertsen method. Tail plane design is considered as the tail/wing area ratio. Parameters most affecting on the aircraft stability derivative is the tail/wing area ratio. The longitudinal handling qualities criteria were introduced in the mathematical contributions of stability derivative. This design technique has been applied to the Paris Jet; MS 760 Morane-Sualnier aircraft. The results show that when the tail/wing area ratio increases the aircraft stability derivative increases, the damping ratio and the natural frequency increases and the aircraft stability is improved. Three regions of flight conditions had been presented which are satisfactory, acceptable and unacceptable. The optimum tail/wing area ratio satisfying the longitudinal handling qualities and stability is (0.025KeywordsLongitudinal Handling---Stability---Tail Design