Characteristic features of jet
A jet is produced when a fluid is discharged through the nozzle. In the jet the velocity of the fluid is accelerated. Free jet is produced when the fluid is discharged in the surrounding with no confinement. A jet is said to be confined when the fluid is discharged in the container. The characteristic feature of the jet (whether free or confined) is that it spreads due to the difference in the density of the jet and the surrounding. A hot jet in the cold surrounding spreads faster than a cold jet in the same surrounding. Spreading of the jet is due to entrainment of the surrounding. Due to entrainment of the surrounding, the axial velocity of the jet decreases. For any downstream axial distance, the maximum velocity is at the centre and minimum at the periphery such that a parabolic profile is developed as shown in the figure 27.3
| Figure 27.3: |
Spreading of an axis-symmetric jet in the surrounding |
In addition, jet carries with it momentum flux. The momentum flux within the jet is
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