Abstract

The history of turbulence is replete with “truths” determined for a range of parameters which, upon extending the range, are found to need modifications—- perhaps not entirely but in some essential ways. As an illustration, a number of scaling relations in turbulence display slow changes with the Reynolds number, and it has been common knowledge that such variations depend loosely on the logarithm of the Reynolds number. Measurements and simulations, whose importance cannot be overstated, often offer less than sterling guidance because they are hard to make and suffer from numerous difficulties that are absent at low Reynolds numbers. This brings into focus the importance of asymptotic “theories”, often in the form of potential scenarios. This talk considers this perspective for a few specific cases from separate domains of turbulence research. It will consider fluctuations in turbulent wall flows (after a brief comment on mean quantities), the veracity of dissipative anomaly in homogeneous and isotropic turbulence, and the scaling of heat transport in thermal convection.