Transition control of Mach to regular reflection induced interaction using an array of micro ramp vane-type vortex generators

An experimental investigation has been conducted to favorably control/modify a Mach reflection induced interaction in a Mach 2.05 flowon a flat plate using an array of single row mechanical micro vane-type vortex generators (VGs). The objective was to study the variation in (i) control device configuration (trapezoidal and the split-trapezoidal or ramp vane-type), (ii) control device height (h/delta = 0.3, 0.5), and (iii) control location (X/delta = 9, 15 upstream of the interaction) in controlling the overall interaction. The primary aim was to investigate a control location and VG configuration which is able to effectively initiate a transition from Mach reflection to regular reflection with minimum changes to the separation characteristics for no control. While the trapezoidal configuration is seen to move the separation location upstream only slightly, the split-trapezoidal configurations result in a considerable upstream movement that is associated with significant reduction in separation shock strength. The latter flow modification causes the Mach stem to completely disappear resulting in a transition from Mach to regular reflection. The control location of X/delta = 15 seems to be most effective for all control device configurations tested. It is further observed that whilst the effectiveness of the split-trapezoidal configuration of h/delta = 0.3 in controlling the transition improves with increasing X/delta, increasing its height to h/delta = 0.5 not only controls the transition process but is also able to control the extent of separation. All the control devices, however, are seen to increase the flow unsteadiness in the intermittent region of separation for both control locations. From this perspective, increasing the height of the control device seems favorable for the closer control location as it not only completely modifies the Mach reflection but also keeps the peak rms value similar to the baseline case. (C) 2015 AIP Publishing LLC.