Effect of aspect ratio on the near field dynamics of a surface attaching jet

Abstract

The interaction of a rectangular turbulent jet with a free surface for three jet-exit aspect ratios is experimentally investigated using Particle Image Velocimetry (PIV). The jet exits from a sharp edged rectangular orifice plate, parallel to the free surface and has a jet width of d = 10 mm. Aspect ratios of 1, 2 and 4 are studied with a fixed offset of 3d from the free surface. Reynolds and Froude numbers based on the bulk velocity are 6900 and 1.27 respectively. Detailed 2-D velocity fields are captured using the PIV in the central x-y plane for 0 < x/d < 23.5. The distribution of Reynolds shear stresses and turbulent kinetic energy show that they are suppressed in the vicinity of the free surface due to confinement. There was a significant effect of nozzle geometry on the reattachment point and recirculation region of the jets.