On characteristics of a non-reacting and a reacting turbulent flow over a backward facing step (BFS)

Abstract

The turbulent reacting flow over a backward facing step shares some essential characteristics of premixed combustion occurring in a typical gas turbine combustor, while it is a simpler configuration to observe and model. For this reason and to explore the characteristics of the turbulent flow, in this study the combustion and flow dynamics in a backward facing step as a most elementary part of a combustor is studied numerically in atmospheric conditions. Two different configurations representing two laboratory devices are considered. As a first necessary step, the accuracy of predicted results is validated through the detailed comparison of numerical predictions and experimental measurements for a non-reacting flow. First, based on these non-reacting calculations, the turbulent model is selected and then the reacting simulations are done using a standard combustion model (available in CFX). Calculations are well supported with experimental data available from literature. Among the investigated turbulence models (k−ω, SST and SAS–SST), SAS–SST model showed the best agreement with the experimental data. The chosen turbulence model was used for the calculation of well documented case of turbulent flow over a backward facing step with the heated wall, showing satisfactory results compared to experimental data. For modeling of the reacting flow, the BVM combustion model was used. The predicted results using this model showed accurate results with an error about 2% on prediction of reattachment length.