Examination of the onset and decay of turbulence in pipe flow

This figure displays the iso-surfaces of a turbulent puff's azimuthal velocity. We have demonstrated that azimuthal motion is the primary cause of triggering the onset of turbulence, a chaotic state. Puffs abruptly break out of a chaotic state at Reynolds numbers Re 1870, then decay exponentially. We found that the decay rate is entirely consistent with the cubic expression Sreenivasan used in 1979, but only after adding a constant.