The jet axial velocity decay and velocity distributions of two 2D Lobed Nozzles (2DLN), and three baseline nozzles, one circular and two rectangular with different aspect ratios (AR), were measured and compared at low velocity (M0 <0.35) and ambient temperature conditions. The five nozzles have the same exit area. Test results show:
1) The jet axial velocity decay of the 2DLN may be characterized by three distinct regions; i.e., “potential core region”, where the jet axial velocity almost remains constant; “rapid decay region”, where streamwise and normal vortices play major roles for enhanced mixing; and, “smooth-down decay region”, where the mixing process is dominated by viscous shear layer spreading and small-scale turbulence.
2) The jet potential core length of the two 2DLN tested is only half to one-third that of the baseline rectangular nozzle (AR=4.37), and about one-fourth to one-sixth compared with the baseline circular nozzle. The length, in which the jet mixed with surrounding air is nearly uniform, is one to two times that of the 2DLN equivalent exit diameter, and depends on lobe design.
