A NUMERICAL EXPERIMENTAL-STUDY OF THE DYNAMIC STRUCTURE OF A BUOYANT JET DIFFUSION FLAME

An overview of a joint numerical/experimental investigation of the dyn amic structure of a low-speed buoyant jet diffusion flame is presented . The dynamic interactions between the flame surface and the surroundi ng fluid mechanical structures are studied by means of a direct numeri cal simulation closely coordinated with experiments. The numerical sim ulation employs the full compressible axisymmetric Navier-Stokes equat ions coupled with a flame sheet model. Counterrotating vortex structur es both internal and external to the flame surface are seen to move up ward along with flame sheet bulges. These buoyancy-driven dynamic feat ures compare well with those observed experimentally by means of phase -locked flow visualizations over entire flame-flickering cycles. The f licker frequencies measured both computationally and experimentally al so compare well. Other aspects of this investigation which are discuss ed include sudden jumps in flicker frequency with increasing coflow ve locity and the utilization of background pressure changes to simulate gravitational force variations experimentally.