Numerical investigation of the effect of tangential helium injection on the linear stability of a compressible boundary layer on a flat plate

The paper is devoted to the numerical investigation of the effect of the geometry of a single channel for tangential helium injection on disturbances in a compressible boundary layer. The boundary layer calculations are performed within the framework of the Navier–Stokes equations in a two-dimensional plane formulation for compressible flows. The boundary layer stability calculations are carried out within the framework of the linear stability theory in the locally parallel approximation taking into account a binary gas mixture. It is shown that, regardless of the configuration of a single channel, the introduction of helium into the boundary layer stabilizes disturbances of the second mode and destabilizes disturbances of the first mode in the region close to the injection site. However, at a sufficient distance from the gas injection site, the growth rates of two-dimensional disturbances of the first and second Mack modes are less than in the case without injection. It is also shown that, at a constant mass flow rate, the channel geometry mainly affects the boundary layer stability only in the helium injection region. An increase in the channel height leads to an increase in the growth rates of the two-dimensional disturbances of the second mode and a decrease in the growth rates of the two-dimensional disturbances of the first mode.