Volume: 9
Number: 2
December 2011

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

• Experimental and Numerical investigation of Shock/Turbulence interaction by Hot-wire Technique
  Mohammad Ali Jinnah
  Abstract PDF
  Experimental and Numerical investigation of Shock/Turbulence interaction by Hot-wire Technique
  Mohammad Ali Jinnah

  Abstract

  In the present paper, an experimental investigation has been carried out to observe the amplification of turbulence intensity after shock/turbulence interaction by hot-wire technique. The hot wires are installed in the wake of the turbulent grids to measure the turbulence fluctuations before and after the reflected shock wave interaction with the turbulent field. Due to different grid plates, different strengths of turbulent fields are found behind the transmitted shock wave. It is observed that the turbulence fluctuations far less open area of the grid plate are higher than the turbulence fluctuations for more open area of the grid plate. Numerical simulations are also conducted on the experimental results where grid plate of 49.5 % open area is used. It is observed that the average longitudinal velocity line for the experimental velocity data simulate with numerical results properly and in some places, 5-7 % deviations are observed with numerical results. Alt the simulation results indicate that the present code with turbulence model is working properly for its initial conditions. The wall pressure fluctuations are also measured experimentally and substantial amplification of pressure fluctuations is observed after the shock/turbulence interaction. The rate of dissipation of turbulent kinetic energy (TKE) and the levels of length scales are determined numerically by using k-t: turbulence model and it is observed that the rate of dissipation of TKE and the levels of length scales decrease after shock/turbulence interaction,
• Development of a User-friendly Integrated CNC System Part Program Generation Software Focusing on Various Turning Operation
  Ahmed Sayem and Md. Anisul Islam
  Abstract PDF
  Development of a User-friendly Integrated CNC System Part Program Generation Software Focusing on Various Turning Operation
  Ahmed Sayem and Md. Anisul Islam

  Abstract

  The paper discusses the development of a user-friendly AutoCAD based Part Program generation software, named Design CAM Turning, suitable for various turning operations. Under Visual Busic® 6.0 environment, this feature based CNC system software allows automatic CNC codes generation by a unified CAD and process planning and CAM integration. Graphic feature identification and geometric parameter extraction from CAD-part-drawing saved as DXF format are executed for process planning and to generate part Program automatically. ActiveX Automation of AutoCAD@14.01 was used to sort out the nodal information and Visual Basic as the programming language as it helps to build a user-friendly and suitable graphical interface. However, software has been facilitated with a 2D simulation of VR Turning software to verify the Part Programs generated prior to using these programs as input to Denford CNC lathe. It has also been provided with the manual data input facility so that it can serve the purpose even to an unskilled user.
• Performance of a Small Window Type Air Conditioner using a Thermostatic Expansion Valve and a Capillary Tube
  Rakib lmtiazZaman and A.K.M. Iqbal Hussain
  Abstract PDF
  Performance of a Small Window Type Air Conditioner using a Thermostatic Expansion Valve and a Capillary Tube
  Rakib lmtiazZaman and A.K.M. Iqbal Hussain

  Abstract

  Electrical energy conservation is an important element of energy policy. Energy conservation reduces the energy consumption and energy demand per capita, thus offsets some of the growth in energy supply needed to keep up with population growth. Reduction of energy consumption is q major concern in the vapor compression refrigeration system especially in the area with hot weather conditions where window-air-conditioners are usually used to cool homes. This kind of weather condition has a major influence in the performance characteristics of air - conditioning units. In most of the cases, electrical power consumption increases considerably in such weather condition. Though some research has been focused on optimizing medium to large capacity refrigeration systems, considering both materials cost and operating costs, not much study has yet been done for a small system like the window air conditioner to find the optimum operating condition i.e, the minimum power requirement and hence the minimum cost of operation during typical summer days. Hence the present study includes an economic comparison between thermostatic expansion device and capillary tube expansion device as well as the optimum operating condition for a small window type air conditioner in hot climates.
• Experimental Studies on Multi-bladed S-shaped Vane type Rotor
  Z. Afroz, M.Q.Islam and M. Ali
  Abstract PDF
  Experimental Studies on Multi-bladed S-shaped Vane type Rotor
  Z. Afroz, M.Q.Islam and M. Ali

  Abstract

  The present research work studies the dynamic conditions of Multi bleded rotor at different Reynolds number. The investigation on wind loading and aerodynamic effects on the four, five and six bladed S-shaped vertical axis vane type rotor has been conducted with the help of an open circuit subsonic wind tunnel. For dffirent bladed rotor the flow velocities were varied from Sm/s to 9m/s covering the Reynolds nannbers up to 1.35 x lO'. tt wus observed that by increasing the number of blades of rotor to the optimum limit considering all significant factors and at the same time by increasing its Reynolds number, the power output cun be increased to its maximum level. It was also found that at higher Reynolds number the value of maximum torque co-efftcient is slightly lower. However, at the same Reynolds number for rotor having higher number of blades the maximum value of torque cofficient is also higher which is very important for irrigation parpose. Finally, the nature of predicted dynamic characteristics has been analyzed by comparing with the existing research works. For comparison power coefficient versus tip speed ratio of the present measurement and previous researcher's works has been
• The Time Mean Velocity and Temperature Fields in Developed Region in an Asymmetrically Heated Smooth Square Duct
  A.K.M. Abdul Hamid, A. R. Akanda and M.A. Taher Ali
  Abstract PDF
  The Time Mean Velocity and Temperature Fields in Developed Region in an Asymmetrically Heated Smooth Square Duct
  A.K.M. Abdul Hamid, A. R. Akanda and M.A. Taher Ali

  Abstract

  The present research deals with the experimental results concerning mean velocity and temperature fields for fully developed turbulent flow through an asymmetrically heated smooth square duct with constant heat flux boundary from the bottom wall. The experiment was carried out in the Reynolds number range 5x10⁴ 5 . It is seen that the mean velocity profiles near the wull bulge towards the corner along the corner bisectors and depress near the side wall along the wall bisectors producing saddle shape form instead of normal parabolic form. This indicates the presence of secondary flow and its effects gradually increases from centre towards the side wall of duct as the saddle shape behavior of the profiles becomes more and more prominent with the decrease in wall distance. This nature of velocity profiles greatly influences the temperature distribution in the flow field producing lower values of near the wall. However the influence of Reynolds number on temperature is 25 percent of that on velocity, In spite of this differential influence the correlation between the velocity ratio, u/u and the temperature ratio, curves fall on a straight line indicating their similurities. But due to presence of secondary velocity the conelqtion remains valid up to u/u,<0.85 in the regiort y/B<0.52. Near the wall i.e., y/B>0.52 secondary velocity changes the correlation constants. All the temperature profiles for dffirent Reynolds number nterge together near the heated waII confirming the steady state heat flow from the wall to the flowing fluid. The semi logarithmic plots of universal velocity, u"* vs. Z* and temperature T,* vs. Z* for each locations of y/B show that they lie on a straight line indicating the presence universal velocity distribution in the log- Iaw -region, region 30