Hydrodynamic instability of boundary layers and separated flows (present state)

Artikel i vetenskaplig tidskrift, 2006

Review is given of recent experimental results on the mechanisms of turbulization of complex flows, such as gradient, spatial, and separated flows, and perspectives of studies in this area at subsonic flow speeds, taking into account the modern manufacturing technologies of wing planes (making surfaces reasonably smooth) for big transport aircrafts at large Reynolds numbers, and the design of wing planes for small-sized flying vehicles (avoiding flow separation) at small Reynolds numbers, are shown. Nonlinear stages of the secondary high-frequency instability of various flows modulated by streaks, as well as methods of the laminar-turbulent transition control for these cases using streak interaction, riblets, localized and distributed suction are considered. Various methods to control the separated flows using localized disturbance sources inside of separated regions, exposing acoustics, and shaping the surfaces by the corrugations are demonstrated. A method of control of the flow separation using the MEMS technique is described.