Formation Process of Taylor Cells of a Surfactant Solution

Abstract

The flow of surfactant solutions between two coaxial cylinders was investigated using the laser-induced-fluorescence flow visualization technique to clarify the effect of drag-reducing additives on the formation process of Taylor cells in Taylor-Couette flow. Test fluids were Ethoquad O/12 10, 50 and 100 ppm surfactant solutions. In the Taylor number range of, 1.2×105 ≤ Ta ≤ 7.1×105, tap water and 10 ppm surfactant solution flows consisted of Taylor vortices and much smaller Go¨rtler vortices at the rotating inner cylinder wall. However, in 50 and 100 ppm surfactant solutions, Taylor vortices are not apparent and Go¨rtler vortices are collapsed. Measurement of the wavelength of Go¨rtler vortices led to the conclusion that surfactant solutions have a stabilizing effect on Go¨rtler instabilities. This effect depends on the concentration of surfactant solutions, and becomes considerable with increasing acceleration of the rotating inner cylinder. By considering the experimental results for the surfactant solutions without counterions, in which Taylor cells were not formed, it was shown that the increase in the local field viscosity based on the shear-induced structure of the surfactant solutions has a stabilizing effect on Go¨rtler instability.