Statistical properties of streamwise velocity in a supersonic turbulent boundary layer

Statistical properties of streamwise velocity fluctuations in a supersonic boundary layer are examined using particle image velocimetry data. The mean velocity profile reveals a logarithmic region that extends farther from the wall (compared to incompressible boundary layers), up to y/delta approximate to 0.5. The rms velocity profiles are consistent with previous measurements reported in the literature and indicates a plateau region between y/delta=0.3 and 0.6 with a nominal second peak at y/delta approximate to 0.6. Contours of two-point correlations are forward leaning for reference locations near the wall and become more symmetric along both streamwise and wall-normal directions as the reference location moves away from the wall. The integral length scales (L-x) and the representative length scales (lambda(u)(x)) reveal an increasing-decreasing trend with distance from the wall, attaining a maximum within the logarithmic region at y/delta approximate to 0.4. (c) 2007 American Institute of Physics.