|
The mechanism leading to suppression and control on the self-
sustaining oscillation over the cavity are investigated
experimentally in this study. Quantitative velocity measurement
and qualitative flow visualization were performed by ways of LDA
system and the laser sheet technique. The main objects in this
study are : (1)Influence of the leading-edge profile of the
horizontal top plate on self-sustaining oscillation over a
rectangular cavity (2)Influence of the bottom slope on self-
sustaining oscillation (3)Influence of feedback interruption on
self-sustaining oscillation. Some important results are found
and concluded as follows:(1) Different leading-edge profiles of
the cover plate will produce different near-surface flow
structures leading to different extent of mean flow acceleration
and different level of velocity fluctuation that are the key
mechanism to promote the oscillatory characteristics of the
cavity shear-layer. In case of remarkable flow acceleration, the
mode of self-sustaining oscillation will jump to the mode of
higher frequency.(2) Cavity with positive bottom slope will
limit the feedback location within the downstream corner of the
cavity. However, negative bottom slope will provide adverse
effect for the feedback to move further upstream. Both will
diminish the self-sustaining oscillation within the cavity.(3)
For steady state condition, feedback interruption at different
positions and angles can modify the strength and the upstream
extent location for the feedbck to reach,thus,the self-
sustaining oscillation ca n be either suppressed or enhence. On
the other hand, applying different frequency perturbation to the
large recirculaton in the cavity only can enhence the low
frequency modullation, but can''t promote the self-sustaning
oscillation to jump to another mode.Keyword: cavity flow,
feedback interruption, self-sustaining oscillation
|