DOI: 10.1615/TSFP5
COMPARATIVE STUDY OF LAGRANGIAN EVOLUTION OF DISTURBANCES: VORTICITY VERSUS MATERIAL LINES
ABSTRAKT
The evolution of disturbances in turbulent flows is studied here using direct numerical simulations (DNS) and experimentally using three dimensional particle tracking velocimetry (3D-PTV) through a Lagrangian tracking of pairs of particles. The disturbances are presented as an evolving differences between the vorticity vectors of the initially closed particles and also infinitesimal material lines, attached to the particles. There is a striking dissimilarity of the evolution of active turbulent quantities, such as vorticity as compared to the passive objects such as material lines. The gained insight in the differences is important for progress in understanding of the mechanisms involved in genuine turbulence and evolution of passive objects.