Rodríguez, D and Gennaro, EM and Juniper, MP (2013) On the two classes of global primary modal instability in laminar separation bubbles. 43rd Fluid Dynamics Conference.Full text not available from this repository.
The self-excited global instability mechanisms existing in flat-plate laminar separation bubbles are studied here, in order to shed light on the causes of unsteadiness and three- dimensionality of unforced, nominally two-dimensional separated flows. The presence of two known linear global mechanisms, namely an oscillator behavior driven by local regions of absolute inflectional instability and a centrifugal instability giving rise to a steady three- dimensionalization of the bubble, is studied in a series of model separation bubbles. Present results indicate that absolute instability, and consequently a global oscillator behavior, does not exist for two-dimensional bubbles with a peak reversed-flow velocity below 12% of the free-stream velocity. However, the three-dimensional instability becomes active for recirculation levels as low as urev ≈ 7%. These findings suggest a route to the three-dimensionality and unsteadiness observed in experiments and simulations substantially different from that usually found in the literature, in which two-dimensional vortex shedding is followed by three-dimensionalization.
|Divisions:||Div A > Energy|
|Depositing User:||Cron Job|
|Date Deposited:||07 Mar 2014 12:10|
|Last Modified:||08 Dec 2014 02:17|