4.7 Article

Control of laminar breakdown in a supersonic boundary layer employing streaks

Journal

JOURNAL OF FLUID MECHANICS
Volume 932, Issue -, Pages -

Publisher

CAMBRIDGE UNIV PRESS
DOI: 10.1017/jfm.2021.1047

Keywords

compressible boundary layers; drag reduction; transition to turbulence

Funding

  1. Gauss Centre for Supercomputing [44026]
  2. China Scholarship Council [201708080155]

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This study utilized direct numerical simulations to investigate the effects of various parameters on the laminar-flow-control capabilities of narrowly spaced streaks in a supersonic boundary layer at Mach 2.0. The research found that spectrum-enriching subharmonic modes do not destroy the controlling mechanism, and a complex breakdown scenario triggered by a multi-frequency point source can be effectively controlled.
In this study direct numerical simulations are employed to investigate the effects of various parameters on the laminar-flow-control capabilities of narrowly spaced streaks in a supersonic boundary layer at Mach 2.0. Previous work by Sharma et al. (J. Fluid Mech., vol. 873, 2019, pp. 1072-1089) has found these streak modes, excited by a spanwise blowing-and-suction strip, to be highly effective at delaying pure oblique-type breakdown. In the present work it is shown that spectrum-enriching subharmonic modes, relevant with increasing running-length Reynolds number, do not destroy the controlling mechanism, and also a complex breakdown scenario, triggered by a multi-frequency point source, is found to be effectively controlled. Moreover, the control-streak excitation by roughness elements is compared in detail with the blowing-and-suction method, revealing relevant features.

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