Global linear stability of confined wakes with co-flow
(English)Manuscript (Other academic)
The global stability of confined wakes is studied numerically, using 2D global modes. The wake inlet velocity is varied, and the main focus lies in wakes with co-flow (base bleed). The density and viscosity are assumed to be constant in and outside the wake. We find that for wake Reynolds number 100, the confinement is stabilising in general. The frequency of the unstable mode increases, and wavelength decreases with confinement. By comparing with an artificial, more slowly developing wake, we conclude that the dampening effect is due to the mean flow development. For higher Reynolds numbers this effect decreases. The critical inlet velocities for which the wake becomes unstable are almost identical for unconfined and confined wakes at $Re=400$. Also, the present results are compared with results for an inviscid parallel wake found in literature, since the inlet profile is very similar to the inviscid profile. The confined wake is found to be more stable than its inviscid counterpart, while the unconfined wake is more unstable than the inviscid wake. The reason to both can be explained by the mean flow development.
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-10184OAI: oai:DiVA.org:kth-10184DiVA: diva2:210095
QC 201011022009-04-012009-03-302010-11-02Bibliographically approved