Abstract
An experimental study has been conducted to investigate the flow characteristics over two rounded contour bumps. Vane-type vortex generators or longitudinal aligned passive by-pass jets were implemented in attempt to achieve wake flow control in rounded contour bumps. According to the results collected from the surface oil flow visualisation experiments, it was observed that the use of both the vane-type vortex generators and the longitudinally aligned passive by-pass jet could reduce the size of the spanwise vortices in the bump valley. In addition, a pair of streamwise horseshoe vortices was observed downstream of the bump crest of the contour bump that equipped with the vane-type vortex generators. From the data collected in the particle image velocimetry measurements, it was found that the use of both the vane-type vortex generators and the longitudinally aligned passive by-pass jet could not reduce the size of the wake region but they could reduce its strength. It is deduced that the two streamwise horseshoe vortices generated by the vane-type vortex generators enhance flow mixing which results in reducing the strength of the wake region. In contrast, blowing passive by-pass jet in the bump valley increases the local flow velocity in order to reduce the strength of the wake region.
Highlights
Flow characteristics over rounded contour bumps have been extensively investigated in both subsonic and supersonic freestream in the last two decades [1,2,3,4,5,6,7,8] because of their potential applications in achieving wave drag reduction in both transonic aircraft wings [9,10,11,12,13] and Diverterness Supersonic Inlets (DSI) [14,15]
This leads to the occurrence of flow separation at the leeward side of the bump which is evidenced by the presence of a separation line (S.L.) at the bump crest
High-speed Schlieren photography and time-averaged two-component particle image velocimetry were used for flow diagnostics
Summary
Flow characteristics over rounded contour bumps have been extensively investigated in both subsonic and supersonic freestream in the last two decades [1,2,3,4,5,6,7,8] because of their potential applications in achieving wave drag reduction in both transonic aircraft wings [9,10,11,12,13] and Diverterness Supersonic Inlets (DSI) [14,15]. The author observed that for a given length-to-width ratio of a rounded contour bump, in subsonic flow, increasing the freestream Mach number increases the sizes of both the wake region and the spanwise vortices that present at the leeward side of the bump. This further indicates that the size and shape of the flow features that formed are flow Reynolds number dependent
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