Spatiotemporal dynamics of shear induced bands en route to rheochaos*
Department of Physics, Indian Institute of Science, Bangalore 560012, India
Corresponding author: a firstname.lastname@example.org
Revised: 12 March 2008
Published online: 4 June 2008
We show experimentally that the route to rheochaos in shear rate relaxation measurements is via Type-III intermittency and mixed mode oscillations in the shear-thinning wormlike micellar system of cetyltrimethylammonium tosylate in the presence of salt sodium chloride. Depolarised small angle light scattering measurements performed during flow show that scattered intensity temporally follows the shear rate/stress dynamics and portrays the crucial role played by nematic ordering. Direct visualization of the gap of the Couette cell, illuminated by an unpolarised laser sheet, in the (vorticity, velocity gradient) plane shows that the spatiotemporal dynamics of the shear induced structures is closely related to the temporal behaviour of shear rate/stress fluctuations.
PACS: 82.70.Uv – Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems / 47.50.-d – Non-Newtonian fluid flows / 83.85.Ei – Optical methods; rheo-optics / 83.60.Wc – Flow instabilities
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2008