Transition to turbulence in Taylor Couette flow

The most recent studies of intermittent state in linearly stable shear flows, like pipe, Plane Couette and Taylor Couette flow, have shown that turbulent structures, created by finite-amplitude perturbation, have an exponential distribution of the lifetimes. Here we experimentally examine the lifetime of turbulent spot in Taylor Couette flow (with stationary inner cylinder) for different perturbation mechanisms and different boundary conditions. We show that for all of these cases, the decay of the turbulent spot can be described by Poisson process, which supports the chaotic transient model for this flow. Furthermore, we show that characteristic lifetime of the turbulent spot increases with Reynolds number faster than exponentially, but does not diverge to infinity. This is in agreement with the most recent studies in pipe and Taylor Couette flows and implies that turbulence is a transient state for all Reynolds numbers (before the global bifurcation). Finally, we show that there is a universal behavior for the characteristic lifetime of the intermittent state in Taylor Couette flow with stationary inner cylinder. This universal series is obtained using critical Reynolds number and aspect ratio as scaling parameters.Solid and Fluid MechanicsMechanical EngineeringMechanical, Maritime and Materials Engineerin

Lifetime of turbulent patch in Taylor Couette setup

In linearly stable shear ?ows like pipe and plane Couette ?ows, the transition from the laminar to the turbulent regime occurs abruptly. To better understand this transition, the time evolution of turbulent patches, created by controlled ?nite amplitude perturbations, have been studied in the literature. These studies mostly focused on pipe ?ows for which a ?nite lifetime of the patch was proven. The same conclusion was drawn in the only available study performed in a Taylor Couette setup. Here, we measured the lifetime in a different size TC setup. We show that the lifetime is indeed ?nite and also very sensitive to the boundary condition, but not much to the perturbation mechanism. We suggest that in addition to the Reynolds number, the lifetime depends on the aspect ratio to the radius ratio of the setup.Water ManagementCivil Engineering and Geoscience

Turbulent Spot in Linearly Stable Taylor Couette Flow

The transition from the laminar to the turbulent regime in linearly stable shear flows, for example, pipe and plane Couette flows, occurs abruptly with no precursor. The evolution of turbulent spots has been studied to better understand the dynamics of this transition and the onset of turbulence. These studies have mostly focused on pipe flows for which a finite lifetime of spots was proven. The same conclusion was drawn in the only available study performed in a Taylor Couette setup. Here, the spot lifetime is measured in a different size TC setup. It is shown that the lifetime is indeed finite and also very sensitive to boundary conditions, but not much to perturbation mechanisms. A scaling approach is provided which suggests in addition to the Reynolds number, the aspect and radius ratios are influential parameters on the lifetime. It is found that the spot size varies during its lifetime and increases with the Reynolds number that confirms the rise in turbulence proliferation by approaching the transitional point.Process and EnergyMechanical, Maritime and Materials Engineerin