High Spatial Resolution PIV Study of Self-Similar Adverse Pressure Gradient Turbulent Boundary Layer on the Verge of Separation.

This presentation reports high-spatial-resolution 2C–2D PIV measurements of a self-similar adverse-pressure-gradient turbulent boundary layer near the verge of separation. The experiment was conducted in the LTRAC APG-TBL wind tunnel using a dual-camera system that combined a large field of view for outer-layer structures with a high-resolution near-wall view. Measurements at three streamwise locations show an approximately constant Clauser pressure-gradient parameter, β ≈ 17–18, and very low skin friction, indicating a near-separating APG-TBL. The mean velocity and Reynolds-stress profiles collapse under appropriate scaling, while the near-wall velocity PDF peaks close to zero, further supporting that the flow is close to the verge of separation. Overall, the results demonstrate that high-spatial-resolution PIV can accurately characterise both mean and turbulent statistics in a self-similar APG-TBL and provide evidence of self-similar development with reduced dependence on upstream history effects.