A parametric study has been conducted into the effects of device height (h=6−10 mm), Mach number (M∞=1.5−2.5), and Reynolds number (Re∞=28×106 to 63×106 m−1) on the effectiveness of microramp vortex generators as flow control devices. The control authority of the microramp comes from the two counter-rotating vortices it introduces into the boundary layer. The vortices transport high-momentum fluid toward the wall, thus creating a fuller velocity profile that is less prone to separation. This momentum transport, however, comes at the price of a low-momentum wake that is formed downstream of the device. The induced flowfield has been studied by means of two-dimensional particle image velocimetry, oil-flow, and schlieren visualizations. Most of the geometric flow features were found to scale linearly with microramp height h: the wake height, wake strength, vortex core height, and the momentum flux added to the near-wall region of the flow all increase linearly with h. The control effectiveness of the microramp in the symmetry plane is reduced for higher Mach numbers (M∞=2.5) as the strength of the vortices is reduced, which adds less momentum to the near-wall region of the flow. Also, a stronger wake is recorded for the higher Mach number cases. Only a weak Reynolds number effect is observed, with the microramp becoming slightly more effective at higher Reynolds numbers.
Mach and Reynolds Number Effects on the Wake Properties of Microramps
AIAA journal ; 54 , 11 ; 3481-3494
2016
Article (Journal)
English
Mach and Reynolds Number Effects on the Wake Properties of Microramps
Online Contents | 2016
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