Fluid mixing and local mass transfer characteristics in a grooved channel for self-sustained oscillatory flow

Abstract

Flow patterns and mass transfer rates in a periodically grooved channel were studied in the transitional flow regime. Self-sustained flow oscillations occur at a low Reynolds number. Primary flow instability arises from Tollmien-Schlichting waves triggered by a shear layer above the groove, and thus there is a fluid exchange between channel and groove parts through the shear layer. A further increase of the Reynolds number produces secondary instability causing a three-dimensional flow at the bottom of the groove. Mass transfer was performed by the electrochemical method. The transport rate at the rib increases significantly after the primary instability, but the increment of mass transfer at the bottom of the groove is small. The secondary instability leads to marked transport enhancement at the bottom of the groove