Pipe flow turbulence at extreme reynolds numbers

Turbulent fluid motion is characterized by a large range of physical and temporal scales, so that the smallest eddies are typically many orders of magnitude smaller than the largest eddies, and the time scales also encompass many orders of magnitude. This complexity makes turbulent flows extremely difficult to predict and so experiments become crucial in any effort to model the flow behavior. It is the same complexity, however, that makes turbulence measurements very difficult, and current methods often suffer from inadequate spatial and temporal resolution to capture the full range of scales present in the flow. We describe a new nano-scale anemometry probe that dramatically extends the range of possible turbulence measurements, and we demonstrate its impact by presenting turbulence measurements in a pipe flow over an unprecedented range of conditions. The results reveal a remarkable similarity in the scaling for the mean flow and for the streamwise turbulence intensity, which marks the onset of what we call the extreme Reynolds number regime.