TY - CONF
T1 - FREESTREAM-TURBULENCE INDEPENDENCE OF SECONDARY INSTABILITY OF CROSS-FLOW VORTICES IN SWEPT-FLAT-PLATE BOUNDARY LAYER
AU - Nakagawa, Kosuke
AU - Ishida, Takahiro
AU - Tsukahara, Takahiro
N1 - Funding Information:
This work was supported by JST SPRING, Grant Number JPMJSP2151. We appreciate Professor D. Watanabe at Toyama University for his valuable advice to simulate freestream turbulence. Some of the present numerical simulations utilized supercomputer resources at the Cybermedia Center, Osaka University and the Cybermedia Center, Tohoku University.
Publisher Copyright:
© 2022 12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022. All rights reserved.
PY - 2022
Y1 - 2022
N2 - Laminar-to-turbulent transition on a swept-flat plate is caused by the breakdown of the cross-flow vortex via the high-frequency secondary instability. In order to determine common transition mechanisms, this parametric study has analyzed turbulent transitions under various environmental conditions including wall-roughness elements and freestream turbulence. We performed direct numerical simulations of the Falkner-Skan-Cooke boundary layer with various conditions of isolated roughness and/or different peak wavelengths of freestream turbulence. In the roughened case, where the flow was accompanied by the stationary cross-flow vortex, the short-wavelength freestream turbulence promoted the secondary instability with hairpin vortices, while the long-wavelength disturbance delayed the cross-flow-vortex break down compared to the short wavelength condition. The wavelength of freestream disturbance played a key role to promote high-frequency secondary instability on the cross-flow vortex. The main finding here is, with or without freestream turbulence, the high-frequency secondary instability is commonly the trigger for the breakdown to turbulence.
AB - Laminar-to-turbulent transition on a swept-flat plate is caused by the breakdown of the cross-flow vortex via the high-frequency secondary instability. In order to determine common transition mechanisms, this parametric study has analyzed turbulent transitions under various environmental conditions including wall-roughness elements and freestream turbulence. We performed direct numerical simulations of the Falkner-Skan-Cooke boundary layer with various conditions of isolated roughness and/or different peak wavelengths of freestream turbulence. In the roughened case, where the flow was accompanied by the stationary cross-flow vortex, the short-wavelength freestream turbulence promoted the secondary instability with hairpin vortices, while the long-wavelength disturbance delayed the cross-flow-vortex break down compared to the short wavelength condition. The wavelength of freestream disturbance played a key role to promote high-frequency secondary instability on the cross-flow vortex. The main finding here is, with or without freestream turbulence, the high-frequency secondary instability is commonly the trigger for the breakdown to turbulence.
UR - http://www.scopus.com/inward/record.url?scp=85143823337&partnerID=8YFLogxK
M3 - Paper
AN - SCOPUS:85143823337
T2 - 12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022
Y2 - 19 July 2022 through 22 July 2022
ER -