Vortex heat transfer enhancement in the separated flow near structured dimpled surfaces

Abstract

Abstract The numerically discovered phenomena of abnormal enhancement of the separated flow in the inclined oval-trench dimple (OTD) and the flow acceleration in the dimpled narrow channel are substantiated experimentally. The analysis of turbulent flow around a deep OTD on the plate and on the channel wall show that within the inclination angle range from 25° to 85°, the pressure drop is seen between the zones of stagnation on the windward slope and of rarefaction in the place where a tornado-like vortex is generated. The velocity field measurements in the narrow channel with two rows of inclined OTDs at the inclination angles of ±45° and ±135° reveal that the shear flow with a maximum velocity in front of the dimple entrance is formed in the flow core. This maximum shear flow velocity exceeds the maximum velocity in the plane-parallel channel.