AIM 2000-0335 Application of the National Combustion Code Towards Unsteady Mixing and Combustion Modeling

This paper demonstrates the application of the National Combustion Code (NCC) to unsteady mixing in combustion modeling. It addresses questions raised previously concerning modeling of the Roback-Johnson isothermal swirling flow experiment. The RobackJohnson case has ti-equently been selected for flow modeling but has presented simulation difficulties for nearly twenty years. Recently, the entire flowpath was modeled including swirler vanes. This resolved disagreement between measurement and computation in the tangential velocity, but revealed a disagreement between experimental measurement and computational simulation in the dye concentration at x = 5 1 mm. Two simulations of the Roback-Johnson experiment are described in this paper. For these simulations, the NCC was run in time accurate mode in an attempt to resolve the dye concentration disparity. Agreement between computation and measurement was obtained by using a 111 three-dimensional model and a grid that was dense enough to resolve accurately the shear layers and centerline stagnation points.