Relative scaling exponents and intermittency in compressible turbulent channel flows

The relative scaling exponents and intermittency of three-dimensional compressible turbulent channel now are investigated by using direct numerical simulation. One case is subsonic flow (Ma = 0.8), the other is supersonic (Ma = 1.3), and the Reynolds numbers based on the mean bulk velocity and channel half-width are 2826 and 3010, respectively. The analysis of the local slopes of sixth order velocity structure function to third order reveals that there is a well-defined scaling range for 10 < y(+) < 100. It is also noted that the intermittency of longitudinal velocity increments in this region is stronger than that of the transverse ones. Comparison with the incompressible case shows that the location of the most intensive intermittency moves toward the log-law region, which is related to the displacement of streamwise vortical structures in the near-wall region.