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Oscillatory double-diffusive convection in a rectangular enclosure with combined horizontal temperature and concentration gradients

Influence of imposed oscillatory frequency on mass transfer enhancement of grooved channels for pulsatile flow

A review of hydrodynamics and heat transfer through corrugated channels

Heat transfer enhancement in self-sustained oscillatory flow in a grooved channel with oblique plates

Flow and mass transfer characteristics in an axisymmetric sinusoidal wavy-walled tube are investigated experimentally in the Reynolds number range from 50 to 1000 The flow patterns are visualized by the aluminum dust method The measurements of the wall shear stress and the mass transfer rate for high Schmidt number are performed by the electrochemical method The attention is focused on their characteristics, including the transitional flow It was observed that steady flow changes into unsteady flow when the Reynolds number exceeds about 160 The wall shear stress in the minimum circular cross section of the tube and the mass transfer rate for one wavelength are shown to depend upon the Reynolds number In the laminar flow regime they increase with the slope of 1 and 1/3, respectively, whereas in the turbulent flow regime they increase with the slope of 3/2 and 3/5, respectively In the transitional flow regime both of them increase significantly with further larger slope It is found that the laminar-like motion and turbulent-like motion occur alternatively, with different time intervals, indicating intermittent flow behavior This is quite different from the flow instability of the wavy-walled channel in which Tollmien-Schlichting waves keeping a time-periodic flow appear

Fluid flow and mass transfer characteristics in a sinusoidal wavy-walled tube at moderate Reynolds numbers for steady flow

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

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

Flow patterns and mass transfer rates in a periodically grooved channel were studied in the transitional flow regime. Self-sustained flow oscillation occurs 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 fluid exchange between channel and groove parts through the shear layer. It is found that 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.

Fluid Mixing and Local Mass Transfer Characteristics in a Grooved Channel for Self-Sustained Oscillatory Flow.

Flow patterns and wall shear stresses in periodically grooved channels were studied in the transitional flow regime. In order to examine the effect of groove length, we employed three different channels. It is found that self-sustained flow oscillation occurs at a lower Reynolds number as the groove length is increased. The flow instability arises from Tollmien-Schlichting waves triggered by a shear layer between the bulk flow and groove flow, which is confirmed by numerical simulation. A significant increment in the wall shear stresses is identified after the onset of flow instability, and mass transfer is enhanced.

Hiroaki Nakagiri

Papers

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

Fluid Mixing and Local Mass Transfer Characteristics in a Grooved Channel for Self-Sustained Oscillatory Flow.

Flow Patterns and Wall Shear Stresses in Grooved Channels at Intermediate Reynolds Numbers. Effect of Groove Length.