An experimental investigation on the coherent structure formation in the 2-dimensional mixing layer between combustion gas and air has been conducted.
In order to study the effect of initial conditions on the formation of coherent structure, a trip wire was placed at the nozzle exit.
Velocities of combustion gas and air are 7.0 mps and 6.6 mps respectively. Reynolds number based on the down stream distance and the air velocity is order of $10^4$.
Velocity measurements were accomplished by utilizing laser Doppler velocimeter and molar concentration was measured using gaschromatograph. Flow visualizations were performed by the shadowgraph method.
Certain conclusions as to the mixing layer can be made based upon the results of the current study.
These conclusions include:
1. The laminar instability predominates in the near region of the mixing layer of the present study.
2. When tripwire was placed at a certain region of nozzle exit, the coherent structure was collapsed. This may be due to the variation of mean velocity profile resulted from the wake effect of the wire.
3. In case the tripwire is placed, the diffusion of heat and mass may be more active.