Abstract

High Reynolds number flows are common in industrial applications as well as in daily life. These flows are characterized by stochastic perturbations, and need a constant source of energy to sustain themselves. I use low order models to understand the formation of coherent structures in wall-bounded flows. I will mainly discuss two canonical flow cases: turbulent channel flow and rotating pipe flow. Firstly, I will show why near-wall streaks, though turbulent, always have spanwise spacing of 100 wall units. Secondly, I will discuss the formation of large and very large scale motions in wall turbulence. Thirdly, I will discuss how rotation in pipe causes drag reduction. Fourthly, I will discuss improving the low order models by using turbulence models.