Implicit large-eddy simulation of subsonic compressible low Reynolds number flow over a flat plate at Re = 20,000

We performed an implicit LES around a 5% thick plate with a Reynolds number of 2.0 × 10⁴ and investigated the freestream Mach number effect on the flow structure and turbulent transition. As in the Reynolds number of 1.1 × 10⁴ reported in the previous studies, the turbulent transition is delayed, and the length of the laminar separation bubble increases due to an increase in the freestream Mach number. The tendency was remarkable at the Mach number of 0.5. In the case of Mach number of 0.8, the pressure plateau disappears, and flow does not transition to turbulence at the Reynolds number of 1.1 × 10⁴, but it was found that the reattachment occurs after the turbulent flow transition when the Reynolds number is 2.0 × 10⁴. In addition, the transition point and the reattachment point move downstream as the freestream Mach number increases, and the distance from the transition point to the reattachment point is also increased by increasing the freestream Mach number. This result indicates that the turbulent transition gently occurs under the high Mach number condition. In addition, the peak Reynolds stress is reduced under high Mach number conditions.