Theoret. Comput. Fluid Dynamics (1994) 6:113-123 Theoretical andComputational FluidDynamics O Springer-Verlag1994 A Numerical/Experimental Study of the Dynamic Structure of a Buoyant Jet Diffusion Flame R.W. Davis and E.F. Moore Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, U.S.A. L.-D. Chen Department of Mechanical Engineering, The University of Iowa, Iowa City, IA 52242, U.S.A. W.M. Roquemore Wright Research and Development Center, Aero Propulsion and Power Laboratory, Wright-Patterson Air Force Base, OH 45433-6563, U.S.A. V. Vilimpoc and L.P. Goss Systems Research Laboratories, Inc., Division of Arvin/Calspan, Dayton, OH 45440-3696, U.S.A. Communicated by Ashwani Kapila Received 24 January 1993 and accepted 5 September 1993 Abstract. An overview of a joint numerical/experimental investigation of the dynamic structure of a low-speed buoyant jet diffusion flame is presented. The dynamic interactions between the flame surface and the surrounding fluid mechanical structures are studied by means of a direct numerical simulation closely coordinated with experiments. The numerical simulation employs the full compressible axisymmetric Navier-Stokes equations coupled with a flame sheet model. Counterrotating vortex structures both internal and external to the flame surface are seen to move upward along with flame sheet bulges. These buoyancy-driven dynamic features compare well with those observed experimentally by means of phase-locked flow visualizations over entire flame-flickering cycles. The flicker frequencies measured both computationally and experimentally also compare well. Other aspects of this investigation which are discussed include sudden jumps in flicker frequency with increasing coflow velocity and the utilization of background pressure changes to simulate gravitational force variations experimentally. 1. Introduction Jet diffusion flames have been frequently studied as an analog for more complex combusting flows ever since the original development of the basic theory by Burke and Schumann (1928). This is because, although geometrically simple, these flames exhibit many of the features found in more complex physical systems. In particular, the dynamic interactions of the flame surface with the 113