Abstract

Significant success has been achieved in recent years by a dynamical systems approach to low Reynolds number turbulence, particularly regarding transition and their relation to coherent structures. Establishing links with experiments and simulations of turbulent flows, however, has been stifled by the vastness of the number of degrees of freedom in real flows. This both serves to mask the underlying dynamics and renders the simulations expensive. In plane Couette flows the Minimal Flow Unit was introduced as a testing ground for probing transitional dynamics. For pipe flow we introduce a 2.5-dimensional model which preserves the key spatio-temporal features—localised puffs, expanding slugs, and long-term transients. Simulations within this model are already proving fruitful in directing parallel simulations in 3-dimensions, which would otherwise prove costly to run without a clear target.