ABSTRACT

A subsonic zero-pressure gradient uniformly-heated turbulent boundary layer at a Reynolds number in the range of 3560 ≤ Re_θ ≤ 5360 was investigated. Particle-image velocimetry measurements were carried out at selected positions in the streamwise direction for several wind-tunnel speeds and for different wall temperatures to show the convection effects to expand the boundary-layer thickness and to enlarge the turbulence intensities in the log-law and wake region. The inclination of large-scale ramp-like vortex packets increases to higher characteristic angles, i.e., the mean angles are enlarged by approx. 10°. Hairpin-like vortex structures originating from the near-wall region seem to undergo higher climbing rates in the wall-normal direction causing the above mentioned significant changes in the mean velocity profiles, the boundary-layer thickness, and the strongly increased distributions of turbulence intensities in the wake region of the boundary layer. The two-point correlation distribution of the streamwise velocity fluctuations R_uu is increased for wall distances y/δ = 0.1 to y/δ = 0.75 indicating the existence of coherent structures in higher regions of the boundary layer.