Space-time correlation measurements in a turbulent natural convection boundary layer

Spatial correlations normal to the wall and longitudinal space-time correlations of temperature fluctuations have been measured. The relative independence of the flow in the sublayer from that outside has been noted. In the transition region a strongly periodic phenomenon was observed with characteristics which agree with those suggested by linear stability analyses. The decay of the 'memory' of the turbulence in the fully turbulent region, was found to be similar to that observed in grid turbulence and in a forced flow boundary layer. The important scales of the turbulence were found to vary relatively slowly with distance normal to the wall, outside the sublayer, indicating a fairly uniform turbulence structure.