Prandtl Lecture 2013

Ludwig Prandtl Memorial Lecture

Monday, March 18, 13:30 - 14:30

(Serbian National Theatre)

Turbulence at Extreme Raynolds Numbers
Alexander Smits, Princeton

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, especially at very high Reynolds numbers. We describe a new nano-scale anemometry probe that dramatically extends the range of possible turbulence measurements, and we present turbulence measurements in a pipe flow over an unprecedented range of conditions. The results reveal a previously suspected but inverified universal distribution for the streamwise turbulence intensity, revealing a new symmetry in the scaling of mean and fluctuating velocities in wall-bounded turbulence.