High Spatial Resolution Measurement of Turbulent Channel Flow Using 2C-2D PIV and 3C-3D Digital Holographic PIV*

Experimental measurements of turbulent channel flow have historically lagged behind direct numerical simulations (DNS). However, they remain essential for verifying simulations that involve surface treatments, such as micro-texturing of the channel walls. This presentation reports on high-resolution measurements of turbulent channel flow using 2-component – 2-dimensional (2C-2D) particle image velocimetry (PIV) and 3-component – 3-dimensional (3C-3D) Digital Holographic PIV (DHPIV).

The measurements were conducted in a water channel with a test section 20 mm high and 700 mm wide, yielding an aspect ratio of 35, which ensures that the mean flow at the channel centerline is nominally two-dimensional. The frictional Reynolds number (Re_τ) is 1400. Using a pair of 100 MP sensors, the spatial resolution of the 2C-2D PIV is less than the viscous length scale. For the 3C-3D DHPIV, the presented methodology applied a three-dimensional volume deconvolution to mitigate the depth-of-focus and virtual image issues, and a predictive inverse reconstruction approach was used to improve the dynamic range of particle reconstruction.