This study numerically investigated the changes in the behaviour of fluid flowing through an ejector in response to modifications in the nozzle design. The investigation involved constant mass flow of the primary stream through four nozzles (PN1-PN4) formed with a combination of straight lines and sine functions. The area of the nozzle streamwise section varied with each contour. The PN4 nozzle refers to the reference nozzle, and its contours were straight lines only. The velocity decay, turbulence, entrainment, and mixing data were used to measure the flow behaviour. The decay rate was increased by ≈1.7%, entrainment by≈8%, and the maximum turbulence intensity by 16% in the PN3 nozzle. Only a 0.5% increase in decay rate was recorded in PN1 and PN2. The PN3 nozzle had the lowest streamwise area of the four nozzles and performed best per entrainment and mixing. This was because the increase in the velocity of the primary stream at the nozzle trailing edge due to the reduced streamwise area, improved the momentum transfer to the secondary stream and its entrainment into the primary stream.
