An isothermal experimental investigation of turbulence transport through an abrupt axisymmetric expansion

Abstract

A non-intrusive, two-component laser Doppler velocimeter was employed to measure the flow properties of a confined, isothermal, swirling flowfield in an axisymmetric sudden expansion research combustor. A constant angle swirler was used to stir the flow at the inlet of the combustor. Measurements of mean velocities, Reynolds stresses and triple products were carried out at axial distances ranging from 0.38 H (step height) to 18 H downstream of the swirler. Detailed experimental data are provided to help in the understanding of the behaviour of swirling, recirculating, axisymmetric and turbulent flows. Also, these detailed experimental data will be available for upgrading advanced numerical codes. The turbulent kinetic energy terms, convection, diffusion and production, were computed directly from the experimental data using central differencing, while the dissipation term was obtained from an energy balance equation. The swirling flow data are compared with the simple dump flow in the same experimental arrangement and it is shown that swirl enhances the production and distribution of turbulence energy in the combustor which, in turn, indicates thorough flow mixing and earlier flow recovery.