Abstract
An experimental investigation is presented for the flow of a viscoelastic wormlike micelle solution (cetyltrimethylammonium bromide and sodium salicylate in deionized water) around an impulsively rotating cylinder. Flow fields generated by a rotating cylinder within a duct of circular and square cross section are obtained by a particle image velocimetry (PIV) in the plane of the light sheet perpendicular to the axis of rotation. In the early stage after the start of rotation, PIV measurements show that the shear wave is generated on the surface of the cylinder and is propagated by being repeatedly reflected by the duct wall and the surface of the cylinder. At higher rotation speeds, an abrupt change in flow is observed, where the time until the onset of the event is influenced by the effects of shear waves reflected from a duct wall. A core of fluid rotating like a solid body is found around the vicinity of the rotating cylinder. After sufficiently long time, the flow in the plane eventually becomes silent, but annular flow cells are generated wrapping around the rotating cylinder.
