Transient turbulence in Taylor-Couette flow

MSc graduation project of Arjang Alidai
Location: Lab. for Aero & Hydrodynamics
Supervisors: R. Delfos & J. Westerweel
Start of project: September 2010

Project description:

Most flows existing in engineering practice are turbulent, for example the water and natural gas people consume, or the oil pipe lines all around the world. A huge amount of energy would be saved if these flows run under laminar condition. Therefore, the dynamic behavior of the flow during transition from laminar to turbulence has been a significant topic for Fluid Dynamics scientists in recent years.

Flows in linearly stable systems like pipe or Taylor-Couette with stationary inner cylinder are laminar until the Reynolds number reaches a critical value and flow become highly sensitive to small distributions and consequently cause an abrupt change to turbulence. To realize dynamical behavior of the flow one can impose a controlled artifact perturbation on the main flow and observes its growth and development inside the flow. This has been done in pipe flows where momentous results have been obtained. However as an open system pipes have the length limitation and turbulence spot cannot sufficiently evolve to give complete information about their final states. Thus a closed system like Taylor-Couette with no length restriction is an appropriate choice to explore the structure and life time of these turbulent spots named patches in this flow. The Visualization technique PIV (particle image velocimetry) is utilized to achieve a more complete insight into this flow state. Furthermore, flow is numerically simulated to examine the role of secondary flow produced by top and bottom lids (Ekman effect) on laminar velocity profile and its effect on the shape and lifetime of the patch.