Determining the Effect of the Rotation Number on Turbulence Lifetimes in Subcritical Taylor-Couette Flow

Taylor-Couette flow is often characterized by two Reynolds numbers that describe the motion of the inner and outer cylinders independently. While these parameters are experimentally expedient since they are directly related to the rotation rates of the two cylinders, their use obfuscates some of the important underlying physics. In order to better understand the physical conditions under which turbulence is triggered in subcritical Taylor-Couette flow, it is more natural to parameterize the system using a shear Reynolds number (Re_s) and a rotation number (R_Ω), which isolate the relative importance of these two physical effects. Previous research has shown that long-lived transient turbulence can be triggered by introducing perturbations to subcritical laminar flow. Generically, the lifetimes of these transients increase as Reynolds number increases. In order to understand the effect of rotation on the transition to turbulence, we measured turbulence lifetimes at fixed Re_s while varying R_Ω. To accomplish this, we visualized the flow using rheoscopic fluid and implemented a machine vision algorithm to monitor the duration of turbulent transients. By measuring the lifetime of turbulence over many experimental trials, we hope to isolate the roles of shear and rotation in the transition to turbulence. This poster presents preliminary data from these investigations.