Control of incident shock-induced boundary-layer separation using steady micro-jet actuators at M∞ = 3.5

Abstract

Experiments were carried out to control an incident shock-induced separation associated with 22° shock generator in a Mach 3.5 flow using an array of steady micro-jet actuators. Four micro-jet actuator configurations based on the variation in their pitch angle [Formula: see text], skew angle [Formula: see text] and span-wise spacing were used. Each of these configurations were placed 14 δ upstream of the interaction and operated with injection pressures ( Poj) varying from 140 to 643 kPa. While no major variations in separation characteristics were observed for Poj < 140 kPa, significant modifications were observed beyond [Formula: see text] of 140 kPa and until 208.5 kPa. Amongst all the four control configurations, micro-jet vortex generator 2 ([Formula: see text] showed the best control with a 2 δ downstream shift in separation point location relative to no-control. The shift is also accompanied with a change in maximum zero-crossing frequency towards higher frequency (almost twice), a reduction in the intermittency length and an increase in the correlation value between the boundary layer just upstream of the interaction and the intermittent region. These results indicate that the effectiveness of micro-jet vortex generator 2 is probably due to the improved entrainment levels in the shear layer induced by the micro-vortices which are generated downstream of these devices. The increase of the skew angle [Formula: see text] from 180° to 270° for the same pitch angle of β = 45° (micro-jet vortex generator 3) seems to have no major impact on the separation characteristics. The reduction in the span-wise spacing (micro-jet vortex generator 4) resulted in deterioration of the flow field due to the jet-to-jet interaction with increasing injection pressures.

Effect of air jet with injection pressure on the performance of mixed compression air intake

“…For supersonic cases, an experimental investigation on high speed micro-jets is demonstrated by Kumar and Alvi 12 to control boundary layer separation for application of internal and external flows. An experimental study on incident shock boundary layer interaction, conducted by Chidambaranathan et al 13 at Mach number of 3.5 and injection pressure varying from 140 to 643 kPa, reported improvements in shear layer. Further, the effect of injection through micro ramp on SWBLI control is reported by Vaisakh and Muruganandam 14 and the results suggest an increase in pressure recovery.…”

Effect of microramps on flare-induced shock – boundary-layer interaction

“…Although it is impossible to eliminate shock-boundary layer interactions from these highspeed flowfields, it is essential to alleviate or reduce its undesirable effects for better performance and reliability of these vehicles. Many techniques (18) have been put forth by researchers in the past to mitigate and possibly eliminate the shock-induced flow separation such as steady (19,20) and pulsating (21) microjet actuators, plasma actuators (22,23) , shock control bumps (24) , aerodynamic bleed (25) , magnetohydrodynamic systems, (26) etc. A large number of these flow control techniques are employed to energize the low momentum fluid of the boundary layer that is close to the wall, thereby enabling it to better resist the adverse pressure gradient.…”

Influence of multi-wall separation control on normal-shock-induced separation in supersonic duct flows

“…Since these MVGs control shock-induced separation using flow energy itself, they are considered as passive devices. Air jet vortex generators [18][19][20] are another type of control device to control shock-induced separation. Even though air jet vortex generators use external energy, the injected mass flow rate is very low compared to the boundary layer flow rate and this method qualifies as ''partially active''.…”