JOURNAL OF ENGINEERING AND TECHNOLOGY

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Volume: 10
Number: 1
June 2012

To see an article directly, click its Title. To see abstract, click its [Abstract] link.

  • An Experimental Investigation of Wind Load on a Group of Octagonal Cylinders with Variable Longitudinal Spacing
    Md. Jomir Hossain, Md. Quamrul Islam and Mohammad Ali
    Abstract PDF
    An Experimental Investigation of Wind Load on a Group of Octagonal Cylinders with Variable Longitudinal Spacing
    Md. Jomir Hossain, Md. Quamrul Islam and Mohammad Ali

    Abstract

    An experimental investigation of wind load on a group of octagonal cylinders with various longitudinal spacing was carried out. The study was performed on group consisting of two cylinders, arranged in staggered form varying longitudinal spacing, one in the upstream and the other in the downstream side. The test was conducted in an open circuit wind tunnel at a Reynolds number of 4.13 x 104 If based on the face width of the cylinder across the flow direction in a uniform flow of velocity 13.2 m/s. The surface static pressures at the different locations of the cylinder were measured with the help of inclined multi-manometers. Then the group of two cylinders were taken into consideration for the study and the surface static pressures were measured for various longitudinal spacing's of ID,2D,3D,4D,5D,6D,7D and 8D, where D being the width of the cylinder across the flow direction. The pressure coefficients were calculated from the measured values of the surface static pressure distribution on the cylinder. It was observed that the drag coefficients become remarkably smaller compared to those for a sharp-edged square cylinder. After all, it was concluded from the results that wind loading on a building is generally less severe when the building forms part of a group than when it is free- standing.
  • Prospect of Wind Electricity Generation in Kutubdia Island, Bangladesh
    A.K. Azad, M. M. AIam, M. Saha and Islam M. RAFIQUL
    Abstract PDF
    Prospect of Wind Electricity Generation in Kutubdia Island, Bangladesh
    A.K. Azad, M. M. AIam, M. Saha and Islam M. RAFIQUL

    Abstract

    Kutubdia is an isolated island and normally the power demand partially fulfilled by diesel generators in this remote island. It is very expensive, difficult, highly risky and time-consuming to transport diesel to this isolated isl.and. Another alternative source of power is 1 MW wind battery hydride power plant. This paper presents the current power situation and a statistical analysis of wind power potential in Kutubdia for extension of wind power plant to meet the power demand there. For the analysis, the wind data from 2000 to 2006 have been collected from the meteorological department, Bangladesh. The data has been sorted in the appropriate frequency like daily, monthly and annual mean wind speed and analysis of two important parameters like Weibull's shape factor (k) and scale factor (c) by three methods like Weibull's paper method, Standard deviation method and energy pattern factor method. It has been found that the value of k remains in between 1.4 to 3.38 and that of c remains between 2.83 to 6.90. The most of the Weibull functions follow very close to the Raleigh function (k=2) for the selected sites. The Weibull's probability density function f(v) and Weibull's function F(v) have been plotted and analyzed with 2006 wind data only and noted its remarkable variations.
  • Study of Magneto-Convection with a Central Spherical heat Source
    Salma Parvin, M.A. Alfun and N. F. Hossain
    Abstract PDF
    Study of Magneto-Convection with a Central Spherical heat Source
    Salma Parvin, M.A. Alfun and N. F. Hossain

    Abstract

    The aim of the present study is to investigate numerically the effect of direction of external uniform magnetic field on natural convection flow in a square cavity in the presence of a spherical heal source. The left wall is heated with a uniform temperature, while the rest walls are kept adiabatic and a circular heat source with higher temperature is placed at the centre. The effect of orientation of magnetic field on streamlines, isotherms, rate of heat transfer, average temperature and average velocity is studied. The governing equations along with boundary conditions are solved by using the finite element method based on Galarkin's weighted residual approach. The result indicates that the horizontal direction of imposed external magnetic field is most appropriate to reduce the fluid flow and heal transfer significantly.
  • A THEORITICAL INVESTIGATION OF TORQUE AND DRAG CHARACTERISTICS OF A SIX BLADED SAVONIUS ROTOR
    Shamsun Nahar, Md. Quamrul Islam and Mohammad Ali
    Abstract PDF
    A THEORITICAL INVESTIGATION OF TORQUE AND DRAG CHARACTERISTICS OF A SIX BLADED SAVONIUS ROTOR
    Shamsun Nahar, Md. Quamrul Islam and Mohammad Ali

    Abstract

    The research work has been carried out to study the aerodynamic characteristic i.e., drag coefficient torque coefficient etc. of a vertical axis type six bladed Savonius rotor. At first drag and torque characteristics of the six bladed Savonius rotor are determined by measuring the pressure distribution over the convex and concave surfaces of each blade at different angle of rotation. The experiment has been carried out at a Reynolds number of 2x105 in a uniform flow jet produced by an open circuit wind tunnel. The pressure measurements have been made at 13 tapping points on each two blades of the rotor. Pressure on the convex and concave surfaces have been measured for every 10° interval of rotor angle up to 360° angle of rotation. The data obtained experimentally has been presented in terms of non-dimensional coefficients. To calculate drag force and torque in non-dimensional form, computer based software has been used and the output has been subsequently plotted and analyzed. The effects of individual blade and also the combined effects of six blades on different aerodynamic characteristics are analyzed in this research work. A quasi-steady approach has been applied for the prediction of the dynamic performance of the rotor using the static drag and torque coefficients. Power coefficient versus tip speed ratio curve for six bladed Suvonius rotor has been drawn. This method results in a reasonable agreement with the measured power coefficient,