Abstract
The flow around a sphere falling through viscoelastic wormlike micelle solutions is investigated by using a particle image velocimetry (PIV) when the falling velocity of the sphere is high compared to the shear wave speed of the fluid. The speed of the shear waves generated by the impulsive excitation of a plate is measured with a PIV. Mach waves due to the passage of the sphere are observed at viscoelastic Mach numbers greater than 1. In relatively dilute cases, Mach waves are accompanied by small vortices generated by the sudden drop of falling velocity of the sphere.
