Large-eddy simulation of bubbly turbulent shear flows

Abstract

This paper reports on recent advances in the application of the large-eddy simulation (LES) approach to turbulent, vertical mixing layers containing bubbles at low void fraction. The method is based on the filtered multi-fluid equations derived from the application of a single component-weighted volume-averaging process. The subgrid-scale (SGS) modelling is based on the Smagorinsky kernel in both its original form and the dynamic procedure of Germano. Parameter studies have been undertaken to determine the effects of the ratio of the cut-off filter to the typical length scale characterizing the dispersed phase, the influence of the lift coefficient, the performance of the SGS models and the importance of inlet turbulence levels. A new model is proposed for possible bubble-induced turbulence modulation, in which the mixing length of the dispersed phase at the SGS is inferred dynamically from the resolved flow field. By averaging over times longer than the dynamic time scales of the turbulent fluctuations, mean quantities, including phase velocities and void fractions, are derived, which are then compared against experimental data. A critical discussion of the usefulness of LES approaches in this context is given. Overall, the LES approach shows considerable promise in regard to predicting mean quantities including phase velocities and void fractions.

This article was chosen from selected Proceedings of the Second International Symposium on Turbulence and Shear Flow Phenomena (KTH-Stockholm, 27-29 June 2001) ed E Lindborg, A Johansson, J Eaton, J Humphrey, N Kasagi, M Leschziner and M Sommerfeld.