Instability of surfactant solution flow in a Taylor cell
The hydrodynamic instability of surfactant solutions between two coaxial cylinders was investigated by using a laser-induced-fluorescence flow visualization technique to clarify the effect of drag-reducing additives on vortex formation in Taylor-Couette flow. The test fluids were Ethoquad O/12 surfactant solutions, which have a gel-like structure called "shear-induced structure" (SIS). Photographs of the formation of Gortler vortices were taken and compared with these of tap water. In the Taylor number range of 1.2 X 10(5) less than or equal to T-a less than or equal to 7.1 X 10(5), tap water and 10 ppm surfactant solution flows consisted of Taylor vortices and much smaller Gortler vortices at the rotating inner wall. However, for 50 and 100 ppm surfactant solutions, Taylor vortices were not apparent and Gortler vortices were collapsed. Measurements of the wavelength of Gortler vortices lead to the conclusion that surfactant solutions have a stabilizing effect on Gortler instabilities. This effect depends on surfactant concentration and becomes considerable with increasing acceleration of the inner cylinder.
surfactant solutions taylor cell visualization gortler vortices non-newtonian flow