Spatial Relationships Between Large Scale Particle Clusters and Momentum Structures

The clustering behavior of inertial particles in a turbulent boundary layer was studied experimentally at the scale of the natural large-scale motions (LSMs) of the momentum field. A new, wavelet-based hierarchy detection tool was employed to identify large-scale coherent clusters of particles, instantaneously. Significant particle clustering at scales of two to three times the boundary layer thickness was observed, with a dominant orientation in the streamwise direction. Conditional averaging was then used to determine the typical coherent motions associated with the large-scale clusters. The influence of LSMs on the size, orientation, and hierarchical organization of particle clusters was explored.