Effect of Small Angles of Attack on Laminar-Turbulent Transition in the Supersonic Boundary Layer on a Swept Wing with χ=72°

An experimental investigation of the effect of small angles of attack on laminar-turbulent transition in the supersonic boundary layer on a swept wing with the sweep angle of the leading edge 72 degrees is performed for the Mach numbers 2 and 2.5 (subsonic leading edge) and 4 (supersonic leading edge). The measurements were carried out in the T-325 wind tunnel of the Institute of Theoretical and Applied Mechanics of the Siberian Branch of Russian Academy of Sciences using a constant temperature hot-wire anemometer. The growth curves and the amplitude-frequency fluctuation spectra are obtained and the locations of laminar-turbulent transition in the supersonic boundary layer on a swept model wing are determined for several values of the angle of attack. It is shown that variations in the angle of attack have a strong effect on the transition Reynolds number at the freestream Mach numbers M = 2 and 2.5. At Mach 4 a small variation in the angle of attack does not lead to a considerable increase in the transition Reynolds number. A decrease in the transition Reynolds number with an increase in the Mach number fixed for the model wing with the sweep angle chi = 72 degrees is in good agreement with the data for the model wing with chi = 45 degrees.