Affiliations: Applied Mechanics, Chalmers University of Technology,
SE-412 96, Gothenburg, Sweden | Institute of Theoretical and Applied Mechanics SB RAS,
630090, Novosibirsk, Russia. E-mail: kozlov@itam.nsc.ru | Naval Architecture & Ocean Engineering, Pusan
National University, 609-735, Pusan, Korea
Abstract: Nonlinear instabilities of boundary layer streaks are investigated
experimentally. Extensive measurements visualizing the sinusoidal and varicose
instabilities of streaky structures at nonlinear stage of the breakdown process
in boundary layer are presented. The flow behaviour in the course of spatial
evolution of the streaky structures with a secondary high-frequency disturbance
generated on them is discussed. Various scenarios of origination and
development of coherent vortex structures examined in physical experiments are
considered. Specific features of the development of sinusoidal and varicose
cases of destruction of the steady streamwise streaks are demonstrated, such as
transverse and streamwise modulations of the streak by the
secondary-disturbance frequency, appearance of new streaky structures in the
downstream direction, and emergence and evolution of unsteady
Λ-shaped structures localized in space in both cases.
Keywords: Visualization, Hot-wire anemometry, Sinusoidal and Varicose instabilities, Streaks
