Discretization and perturbations in the simulation of localized turbulence in a pipe with a sudden expansion

At low Reynolds numbers, the flow through a pipe with sudden expansion is characterized by localized occurrence of instabilities, formation so-called turbulence puff. In literature, physical experiments typically predict earlier than computational fluid dynamics simulations. However, behaviour ‘natural’ transition to without perturbations, and dependence on are not yet fully understood, particularly for The purpose present study therefore investigate this flow, including possible sources perturbation in numerical simulations, evaluate their effect turbulence. Through exploration different rates, settings inlet amplitudes, evaluating coarse refined insights into low-Reynolds-number transitional turbulent flows obtained. kinetic energy budget puff or slug characteristic also evaluated. conclusion, even when perturbations intentionally added, there can still be significant error that trigger but will need added simulations order produce Finally, results agree notion may scenario where transitions naturally any perturbation.