Modal analysis of roughness-induced crossflow vortices in a Falkner-Skan-Cooke boundary layer
2013 (English)In: International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2013, TSFP-8 , 2013Conference paper, Published paper (Refereed)
Abstract [en]
A three-dimensional global stability analysis using high-order direct numerical simulations is performed to investigate the effect of surface roughness with Reynolds number (based on roughness height) Rek above and below the critical value for transition, on the eigenmodes of a Falkner-Skan-Cooke boundary layer. The surface roughness is introduced with the immersed boundary method and the eigenvalues and eigenfunctions are solved using an iterative time-stepper method. The study reveals a global instability for the case with higher Reynolds number that causes the flow in the non-linear simulations to break down to turbulence shortly downstream of the roughness. Examination of the unstable linear global modes show that these are the same modes that are observed in experiments immediately before breakdown due to secondary instability, which emphasizes the importance of these modes in transition.
Place, publisher, year, edition, pages
TSFP-8 , 2013.
Keywords [en]
Atmospheric thermodynamics, Boundary layers, Computational fluid dynamics, Eigenvalues and eigenfunctions, Iterative methods, Modal analysis, Reynolds equation, Reynolds number, Surface roughness, Turbulence, Turbulent flow, Vortex flow, Crossflow vortices, Falkner-Skan-Cooke boundary layers, Global instability, Global stability analysis, Immersed boundary methods, Nonlinear simulations, Roughness height, Secondary instability, Shear flow
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-222982Scopus ID: 2-s2.0-85034229223ISBN: 9780000000002 (print)OAI: oai:DiVA.org:kth-222982DiVA, id: diva2:1193246
Conference
8th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2013, 28 August 2013 through 30 August 2013
Note
QC 20180326
2018-03-262018-03-262022-06-26Bibliographically approved