58 CHAPTER 6. STREAMING STUDIES
Single‐vortex
acoustic streaming
Particle tracks versus actuation frequency
for fixed phase
5.0 μm
particles
0.5 μm
particles
Figure 6.4: Numerical particle trajectories of 5-m-diameter particles (top row) and 0.5-m-diameter
particles (middle row) in a nearly-square channel for three dierent actuation frequencies ! = 2f. The
bottom graph shows the acoustic energy in the channel as function of the actuation frequency of the
velocity boundary conditions sketched to the bottom right. The trajectories correspond to actuation at
the horizontal half-wavelength resonance frequency f1 (left column), the frequency fm in between the two
resonance peaks (center column), and the vertical half-wavelength resonance frequency f2 (right column).
The phase shift of the velocity boundary conditions sketched to the bottom right has been chosen such
as to achieve a single roll streaming ow. The results presented in the gure is based on the simulations
described in Ref. 31 Appendix C.