Velocity and Static-Pressure Distributions in Swirling Air Jets Issuing From Annular and Divergent Nozzles

Mean-velocity and static-pressure measurements have been made in a series of swirling air jets issuing from annular and divergent nozzles into stagnant-air surroundings. Swirl was generated by introducing varying proportions of air through tangential ports while the remainder of the air was introduced axially. A region of subatmospheric pressure is set up in the central region of the jets and as soon as the pressure gradients on the axis exceed a certain critical value, reverse flow is set up with an associated internal ring vortex. With increasing degrees of swirl, the angle of spread of the jets is increased and, correspondingly, the decay of the maximum values of axial, tangential, and radial components of velocity along the lengths of the jets is faster. The integrated axial fluxes of linear and angular momenta were shown to be conserved along the length of the jets.