Influences of microjet pressure and number of microjets on the control of shock wave/boundary layer interaction

Boundary layer separation is a common phenomenon in supersonic/hypersonic vehicles, and can adversely affect the lift coefficient. Currently, active flow control based on microjets is used to inhibit the separation of the turbulent boundary layer. The obtained results predicted by the three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations and two-equation shear stress transport (SST) k-omega both with Realizable k-epsilon turbulence models show that the control mechanism of the microjets method is the counter-rotating vortex pair (CVP) generated by the microjet mixes the low-energy flow within the boundary layer with the high-energy flow near the boundary layer. The size of the vortex core in this CVP is the key to controlling SWBLI. The vortex nucleus that is larger and closer to the wall enables better SWBLI control. A lower or higher ratio of microjet pressure to inflow static pressure increases the total volume of the separation bubble and produces a negative gain. When the ratio of the triangular microjet hole bottom edge length to the spacing between the holes is too small, leading to a deterioration in the control effect. The addition of microjets reduces the total pressure recovery coefficient.(c) 2023 Elsevier Masson SAS. All rights reserved.

Automated summary

Boundary layer separation is a common issue in supersonic/hypersonic vehicles, which can negatively impact the lift coefficient. Current active flow control techniques using microjets have shown to effectively prevent such separation by generating counter-rotating vortex pairs that mix low-energy and high-energy flows. The size of the vortex core plays a crucial role in the control of supersonic wall boundary layer interaction (SWBLI). The pressure ratio and geometry of the microjet holes also affect the control effectiveness and total pressure recovery coefficient.