Direct visualization of shear waves in viscoelastic fluid using microspheres

Wormlike micellar fluids, being viscoelastic, support shear waves. Shear waves in 500 mM CTAB-NaSal micellar fluid were visualized by seeding the fluid with 212–250 μm diameter polyethylene microspheres. This method was compared to visualization through birefringence induced by shear stress in the fluid. Measured shear wave speeds were 733 and 722 mm/s, respectively, for each technique. Particle displacement was a sinusoidal function of time and displacement amplitude decreased quadratically with distance from the source. This supports the possibility of using particle amplitude measurements as a measure of attenuation even at low fluid concentration where birefringence visualization techniques fail.