Mechanisms for spatial steady three-dimensional disturbance growth in a non-parallel and separating boundary layer
2009 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 634, 165-189 p.Article in journal (Refereed) Published
Steady linear three-dimensional disturbances are investigated in a two-dimensional laminar boundary layer. The boundary layer is Subject to a streamwise favourable-to-adverse pressure gradient and eventually undergoes separation. The separating flow corresponds to the first part of a pressure-induced laminar-separation bubble on a flat plate. Streamwise disturbance development in such a flow is studied by means of direct numerical simulation, a water-tunnel experiment and an adjoint-based parabolic theory suited to study spatial optimal growth. A complete overview of the disturbance evolution in various areas of the Favourable-to-adverse pressure gradient laminar boundary layer is given. Results from all investigation methods show overall good agreement with respect to disturbance growth and shape within the entire domain. In the favourable pressure-gradient region and, again, slightly downstream of separation, transient growth caused by the lift-Up effect dominates disturbance behaviour. In the adverse pressure-gradient region, a modal instability is observed. Evidence is presented that this instability is of Gortler type.
Place, publisher, year, edition, pages
2009. Vol. 634, 165-189 p.
gortler vortices, transition, bubble, instability, stability, vortex, flow, streaks
IdentifiersURN: urn:nbn:se:kth:diva-18778DOI: 10.1017/s0022112009007149ISI: 000270065600008ScopusID: 2-s2.0-76249105224OAI: oai:DiVA.org:kth-18778DiVA: diva2:336825
QC 201005252010-08-052010-08-052011-02-01Bibliographically approved