ON THE NUMERICAL MODELING OF BUOYANCY-DOMINATED TURBULENT DIFFUSION FLAMES BY USING LARGE-EDDY SIMULATION AND k–ϵ TURBULENCE MODEL

Abstract

This work concerns the modeling of buoyancy-dominated turbulent diffusion flames. In these flames, ambient air is entrained just above the burning surface into the reactive zone at large mass flow rates. To describe the buoyancy-induced flow, both large-eddy simulation (LES) and the k–ϵ turbulence model are used. The two models, including direct effects of buoyancy, have been validated using experimental data from three (pool-like, vertical, and interaction between pool-like and vertical wall fires) turbulent diffusion flames. It is found that LES successfully predicted the variation of both the mean and fluctuating velocity/temperature. Important features of highly oscillating buoyancy-induced flows (recirculation zone, narrowing and broadening of the flame) have been correctly reproduced by LES, whereas the standard Smagorinsky model should be improved to model turbulent mixing near the vertical burning wall. It is found that interaction between pool-like and vertical wall fires induces an entraining ambient air at larger mass flow rates compared to a pool-like fire or a single vertical burning wall.

Keywords:

• diffusion flame
• oscillating flow
• buoyancy
• turbulence
• numerical modeling