Dresden 2009 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 16: Fluid dynamics I

DY 16.6: Talk

Wednesday, March 25, 2009, 16:00–16:15, ZEU 255

Control of Intermittent Turbulence in Pipe Experiments — •Bjoern Hof, Alberto de Lozar, and Devranjan samanta — Max Planck Institut fuer Dynamik und Selbstorganisation, Goettingen, Deutschland

Despite more than a century of research the onset of turbulence in pipe flow is still not well understood. Flows can in principle remain laminar for all Reynolds numbers (Re) but in practice, unless great care is taken, transition already occurs at moderate values of Re. Typically in the transitional regime flows change intermittently between laminar and turbulence. Here we study the dynamics at the interface between the two states of the flow. An instability mechanism is identified which continuously transfers energy from the laminar to the turbulent motion. From the observed dynamical behaviour we can rationalize the intermittent dynamics and why turbulent structures remain localized in this Re regime. Furthermore, having identified the energetically most active region of the flow, we are able to apply a simple control mechanism to intercept the energy transfer. In experiments carried out at relatively low Reynolds numbers this simple control concept is sufficient to destroy the localized turbulent structures. When this procedure is applied continuously turbulence can be fully omitted downstream of the control point.