Fig.1.21 Instantaneous velocity vector volume (LPT with STB) within the turbulent boundary layer flow, flow velocity color coded, (see Sect.18.2 for details).
More information about Shake-The-Box and 3D Lagrangian Particle Tracking at high Particle Densities (with animation of results as presented in Fig. 1.21) can be found at
Schröder, A., Schanz, D., Geisler, R., Gesemann, S., Willert, C.E.:
Near-wall turbulence characterization using 4D-PTV “Shake-The-Box”.
In:11th International Symposium on Particle Image Velocimetry - PIV 2015. Santa Barbara (CA) ,USA (2015)