Volume: 9
Number: 1
June 2011

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

• Lattice-Boltzmann Analysis of Fluid Flow Behaviors around different Bluff Bodies in a 2D Micro-channel
  M. A. Taher and Y. W. Lee
  Abstract PDF
  Lattice-Boltzmann Analysis of Fluid Flow Behaviors around different Bluff Bodies in a 2D Micro-channel
  M. A. Taher and Y. W. Lee

  Abstract

  In this study, the numerical analysis has been carried out to investigate the fluid flow behaviors around various bluff bodies in a two dimensional micro-channel using Lattice-Boltzmann Method (LBM).The LBM has been built up on the D2Q9 (two dimensional lattice with nine velocities) model with single relaxation method called Lattice-B;GK (Bhatnagar-Gross-Krook) model. Streamlines, vorticity,, velocity and pressure contours are provided to analyze the important characteristics of the flow field for a wide range of the non-dimensional parameter Reynolds number (Re).The simulation results are compared with the experimental results and the results obtained from the other numerical models and the agreement is found to be very reasonable and satisfactory.
• Study of a Hybrid Photovoltaic Thermal (PVT) Solar System using different Ribbed Surfaces opposite to Absorber Plate
  Md. Rezwanul Karim and M.A.R.Akhanda
  Abstract PDF
  Study of a Hybrid Photovoltaic Thermal (PVT) Solar System using different Ribbed Surfaces opposite to Absorber Plate
  Md. Rezwanul Karim and M.A.R.Akhanda

  Abstract

  A hybrid Photovoltaic/Thermal (PVT) solar system can simultaneously provide electricity and heat, achieving a higher conversion rate of the absorbed solar radiation than that of a standard PV module. This system consists of a PV module coupled with water or air heat extraction devices. In this paper, an experimental study of a PVT dual system, both simultaneous air and water circulations with modifications in the air channel are presented. First modification is to place a Thin Flat Metallic sheet (TMS) inside the air channel and the second one is to mount Painted Black Ribbed surfaces at the bottom of the air channel. Natural convection is allowed to take place instead of forced convection to increase the system net electrical output and thereby the overall system efficiency. To observe variations of heat transmittance with change of the shape of ribs (Semicircular, Triangular, Rectangular and FIat surfaces), four experimental systems have been fabricated. Results obtained here have been compared with previous works in this area of research.
• Finite Element Simulation of Mixed Convection in a Lid-driven Cavity having War.y Bottom Surface with Internal Heat Generation
  Salma Parvin, M. A. Alim and N. F. Hossain
  Abstract PDF
  Finite Element Simulation of Mixed Convection in a Lid-driven Cavity having War.y Bottom Surface with Internal Heat Generation
  Salma Parvin, M. A. Alim and N. F. Hossain

  Abstract

  A numerical study has been performed to analyze the mixed convective flow and heat transfer characteristics of heat generating fluids contained in u lid- driven cavity with sinusoidal wavy bottom surface. The vertical walls of the cavity are perfectly insulated while the wavy bottom surface is maintained at a uniform temperature higher than the top lid. The flow is assumed to be two- dimensional. Calculations are carried oat through solving governing equations for different parameters by using Galarkin's weighted residual finite element method. The flow pattern and the heat transfer characteristics inside the cavity are presented in the form of streamlines and isotherms for various numbers of undulations ) and heat generating parameter Q. The heat transfer rate is found maximum for the lowest Q at = 1.
• Numerical Simulation of Axisymmetric Shock Wave Propagation over a Cone
  Mohammad Ali Jinnah
  Abstract PDF
  Numerical Simulation of Axisymmetric Shock Wave Propagation over a Cone
  Mohammad Ali Jinnah

  Abstract

  In the present work, u numerical simulation has been conducted for the axisymmetrical shock wave propagation over a cone by solving the Navier- Stokes equations. A two-dimensional domain is taken to solve the axisymmetric problem and s plane shock wave with the Mach number, Ms=2.38 that propagates from left to right and interacts with u cone surface. The cone apex angle is 86°. Different flow parameters are determined numerically at different positions of the shock wave on the cone to clarify the effects of viscosity and heat conductivity during shock reflection in the conical flow. It is observed that the surface heat flux rate and wall skin friction across the shock are more as compared to other places on cone surface behind the shock wave. The transition point from regular to Mach reflection can hardly be identified if the delayed transition occurs relatively close to the cone apex. The triple point trajectory is drawn for the shock wave propagation over the cone and the transition point is found for the shock wave position of 2.s-3.5 mm from the tip point. The advantages of the numerical simulation are accurate identification of the transition point as well as numerical visualization of the Mach reflection phenomena over the cone surface.
• Large Eddy Simulation on the Unsteady Aerodynamics of a Heavy Duty Truck in Wind Turbulence
  Prasanjit Das and Makoto Tsubokura
  Abstract PDF
  Large Eddy Simulation on the Unsteady Aerodynamics of a Heavy Duty Truck in Wind Turbulence
  Prasanjit Das and Makoto Tsubokura

  Abstract

  Unsteady aerodynamic forces acting on a full-scale heavy duty truck are investigated using a large-eddy simulation technique. The numerical method adopted is first validated on a static condition measured at the DNW German- Dutch wind tunnels. After the correction of the blockage ratio in the wind tunnel, the drag coefficient obtained by our numerical method shows good agreement with the experimental data within the errors of less than 5 %. Effect of an air deflector mounted on the top of a cabin is also discussed" Then the method is applied to non-stationary conditions in which the track is subjected to ambient perturbation of approaching flow. The perturbation of the flow is a model of atmospheric turbulence and sinusoidal crosswind velocity profiles are imposed on the uniform incoming flow with its wavelength comparable to the vehicle length. As a result, it is confirmed that when the wavelength of the crosswind is close to the vehicle length, average drag increases by more than 10% and down-force decreases by about 60%o, compared with the case without perturbation.