Stochastic motion of a laminar/turbulent interface in a shear flow

• Plane Couette flow is a classical prototype of a shear flow where transition toturbulence is subcritical, i.e. happens despite linear stability of the base flow. In this studywe are interested in the spatio-temporal competition between the (active) turbulent phase andthe (absorbing) laminar. Our three-dimensional numerical simulations show that the delimitinginterface, when parallel to the streamwise direction, moves in a stochastic manner which wemodel as a continuous-time random walk. Statistical analysis suggests a Gaussian diffusionprocess and allows us to determine the average speed of this interface as a function of theReynolds number Re, as well as the threshold in Re above which turbulence contaminatesthe whole domain. For the lowest value of Re, this stochastic motion competes with anotherdeterministic regime of growth of the localised perturbations. The latter, a rather unexpectedregime, is shown to be linked to the recently found localised snaking solutions of the Navier-Stokes equations. An extension of this thinking to more general orientations of the interfaceswill be proposed.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Strömningsmekanik och akustik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Fluid Mechanics and Acoustics (hsv//eng)

Publikations- och innehållstyp

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