Instability of surfactant solution flow in a Taylor cell

Abstract

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 Görtler vortices were taken and compared with these of tap water. In the Taylor number range of 1.2ᏽ10 5 d Ta d 7.1ᏽ10 5 , tap water and 10 ppm surfactant solution flows consisted of Taylor vortices and much smaller Görtler vortices at the rotating inner wall. However, for 50 and 100 ppm surfactant solutions, Taylor vortices were not apparent and Görtler vortices were collapsed. Measurements of the wavelength of Görtler vortices lead to the conclusion that surfactant solutions have a stabilizing effect on Görtler instabilities. This effect depends on surfactant concentration and becomes considerable with increasing acceleration of the inner cylinder. critical Taylor number, Ta crit = 4.6 u10 3 t time of inner cylinder rotating ts the time for the flow to become stable, ts = 10800 s G gap width, G = Ri Ro = 39 mm * aspect ratio, * = L / G J shear rate K viscosity of test solution OG Görtler wavelength Q kinematic viscosity of tap water Zi angular velocity

Study on the structures of fluid flows in the annular space formed by a submerged tilting pad journal bearing

“…These vortices have been also investigated for high-speed applications of hydrodynamic journal bearings (e.g., Short and Jackson, 1975). It will, in such applications, also be interesting to suppress the vortices with some agent in the lubricating fluid such as a surfactant (e. g., Watanabe, Takayama and Ogata, 2004). In many cases, however, both of inner and outer cylinders subjected to the study are fully circular and plain without any axial grooves or cavities.…”