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2 International Journal of Applied Mechanics and Engineering

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Mixing and flame holding characteristics in two-dimensional supersonic stream with perpendicular injection

Ali M., Ahmed S., Sadrul Islam A. K. M.

International Journal of Applied Mechanics and Engineering

2008

Vol. 13, no 1

5-20

This paper reports the mixing of hydrogen in a supersonic airstream and the fIame holding capability of the combustion chamber. In particular, two-dimensional Navier-Stokes equations have been solved to see the effects of injector positions on mixing and fIame holding in a supersonic combustor. An explicit Harten-Yee Non-MUSCL Modified-fIux-type TVD scheme has been used to solve the system of equations, and a zeroequation algebraic turbulence model to ca1culate the eddy viscosity coefficient. The performance of combustor has been investigated by varying the distance of injector position from the left boundary keeping constant the backward-facing step height and other ca1culation parameters. The results show that the configuration for small distances of injector position has high mixing efficiency but the upstream recirculation cannot evolve properly which is an important factor for fIame holding capability. On the other hand, the configuration for very long distance has lower mixing efficiency due to lower gradient of hydrogen mass concentration on the top of the injector caused by the expansion of side jet both upstream and downstream of the injector. For moderate distances of injector position, large and elongated upstream recirculation can evolve which might be activated as a good flame holder.

Separation characteristics of fluid flow in a pipe with wavy surface

Mahmud S., Mamun M. A. H., Sadrul Islam A. K. M.

International Journal of Applied Mechanics and Engineering

2002

Vol. 7, no 4

1263-1278

Separation characteristics of fluid flow in a pipe with sinusoidal wavy surface are investigated numerically. The pipe waviness is characterized by a wavelength ('lambda') and an amplitude (a) of the wave. Steady laminar flow of a Newtonian fluid is considered. Governing equations are discretized using the control volume based Finite-Volume method with collocated variable arrangement. SIMPLE algorithm is used and TDMA solver is applied to solve the system of equations. The length of the pipe is kept four times the wavelength (4*'lambda'). The effect of surface waviness, determined by the wavelength-amplitude ratio 'lambda'/a (=L*) , on separation characteristics of fluid flow is presented. The simulation work has been carried out for L*= 11.0 - 30.0 and for the Reynolds number ranging from 50 to 2000. The structure of separation bubble depends strongly on the waviness of the surface for a particular Reynolds number and changes a little with the wave number n. Finally the flow field is presented in the form of stream function and axial velocity profiles for understanding the separation phenomenon.