An experimental analysis of flow transitions in a periodically grooved channel*

Understanding the primary instabilities of a pressure-driven flow in a grooved channel has been critical due to the broad range of industrial applications. This study is investigating the instability behavior of a pure Newtonian fluid passing over and through the periodic two-dimensional groove geometries perpendicular to the flow direction. We performed a combination of flow visualization and particle-image velocimetry and particle tracking velocimetry (PIV/PTV) measurements for a wide range of Reynolds numbers, along stream and span-wise directions to observe the flow patterns.  The experimental data of the primary instability for the Newtonian fluid quantitatively validate the supercritical character predicted by direct numerical simulations (DNS) and also characterizes the convective nature of the instability as well as the determination of critical Reynolds numbers, using well-established methods of applying controlled disturbances. The geometry-induced shear layer destabilization which results in a low-Reynolds number supercritical primary instability has been analyzed in detail.