Flow field in a liquid impinging jets confined by slopping plane walls

Abstract

An experimental investigation was carried out to characterize the flow field in a liquid impinging jet confined by slopping plane walls and emanating from a rectangular duct. The fluids are Newtonian flowing in the laminar (Re= 135 and 276) and turbulent regimes (Re=13,750) and the two-dimensional rectangular cell has an aspect-ratio equal to 13. The fully-developed rectangular jet impinging the flat surface (plate) is confined by two slopping plane walls, each one making an angle of 12° relative to the plate. The presence of the impact plate is felt upstream at y/H= -0.2 in the laminar regime and at y/H= -0.4 in the turbulent regime. The results show that the flow is symmetric relative to the x-y and x-z center planes. Near the plane slopping wall there is separated flow for Reynolds numbers in excess of 208, as was observed in visualization studies. For Re= 275 this small separated flow zone has a normalized length, xR/H = 0.25, whereas for turbulent flow xR/H is equal to 0.9. In the turbulent flow regime turbulence is very high at the jet impact region due to strong fluid deceleration, but the maximum turbulence is observed in the shear layer formed between the jet along the impinging wall and the separated flow region on the sloping wall. We also report three-dimensional effects due to finite slenderness of the flow geometry.