Particle image velocimetry measurements of flow over a wavy wall

The velocity field in a plane that is oriented in the flow direction and pe rpendicular to the wall was measured for flow over a sinusoidal wavy bounda ry. The conditions were such that the surface may be considered as fully ro ugh. Visual observations, as well as two-point correlations of the fluctuat ing velocity field, reveal that the turbulent structure is similar to what is found for flow over a smooth surface even though the mechanisms by which the wall maintains the turbulence are quite different. This provides suppo rt for the notion that, far enough away from the wall, the turbulence is un iversal. (C) 2001 American Institute of Physics.