Fluid particle accelerations in fully developed turbulence

The motion of fluid particles as they are pushed along erratic trajectories by fluctuating pressure gradients is fundamental to transport and mixing i n turbulence. It is essential in cloud formation and atmospheric transport( 1,2), processes in stirred chemical reactors and combustion systems(3), and in the industrial production of nanoparticles(4). The concept of particle trajectories has been used successfully to describe mixing and transport in turbulence(3,5), but issues of fundamental importance remain unresolved. O ne such issue is the Heisenberg-Yaglom prediction of fluid particle acceler ations(6,7), based on the 1941 scaling theory of Kolmogorov(8,9). Here we r eport acceleration measurements using a detector adapted from high-energy p hysics to track particles in a laboratory water flow at Reynolds numbers up to 63,000. We find that, within experimental errors, Kolmogorov scaling of the acceleration variance is attained at high Reynolds numbers. Our data i ndicate that the acceleration is an extremely intermittent variable-particl es are observed with accelerations of up to 1,500 times the acceleration of gravity (equivalent to 40 times the root mean square acceleration). We fin d that the acceleration data reflect the anisotropy of the large-scale flow at all Reynolds numbers studied.