An experiment was performed to measure near-wall velocity and Reynolds stress profiles ina pressure-driven three-dimensional turbulent boundary layer. An initially two-dimensionalboundary layer (Reθ≈4000) was exposed to a strong spanwisepressure gradient. At the furthest downstream measurement locations there was also a fairlystrong favourable streamwise pressure gradient.

Measurements were made using a specially designed near-wall laser-Doppler anemometer(LDA), in addition to conventional methods. The LDA used short focal length optics, a mirrorprobe suspended in the flow, and side-scatter collection to achieve a measuring volume 35 μmin diameter and approximately 65 μm long.

The data presented include mean velocity measurements and Reynolds stresses, all extendingwell below y+=10, at several profile locations. Terms of theturbulent kinetic energy transport equation are presented at two profile locations. The meanflow is nearly collateral (i.e. W is proportional to U) atthe wall. Turbulent kinetic energy is mildly suppressed in the near-wall region and theshear stress components are strongly affected by three-dimensionality. As a result, theratio of shear stress to turbulent kinetic energy is suppressed throughout most of theboundary layer. The angles of stress and strain are misaligned, except very near the wall(around y+=10) where the angles nearly coincide with the meanflow angle. Three-dimensionality appears to mildly reduce the production of turbulentkinetic energy.