Chapter

IUTAM Symposium on Laminar-Turbulent Transition

Volume 78 of the series Fluid Mechanics and Its Applications pp 57-70

LOCALISED INSTABILITY IN UNSTEADY SEPARATION BUBBLES

  • Jaywant H. ArakeriAffiliated withDepartment of Mechanical Engineering, Indian Institute of Science
  • , S.P. DasAffiliated withDepartment of Mechanical Engineering, Indian Institute of Science
  • , Usha SrinivasanAffiliated withDepartment of Mechanical Engineering, Indian Institute of Science

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Abstract

We propose an experimental method to study the instability of thin unsteady separation bubbles, i.e. of unsteady boundary layers with reverse flow. The unsteady boundary layer is created by controlled temporal and spatial variations of the velocity external to the boundary layer. We present results of the evolution of instability in different temporally varying flows in a shallow angle diffuser. Depending on the extent of reverse flow in the boundary we observe that instability can be spatially localised.