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R. Naren Shankar et al.
Fig. 3 a CTPD of lip 2 mm and 7.75 mm for NPR 3. b CTPD of lip 2 mm and 7.75 mm for NPR 5
reflect to form shock waves. This process continues till the supersonic flow becomes
subsonic. This region is called potential core length. Entrainment is the process of
momentum transfer between surrounding still air and the jet. Because of entrainment,
characteristic decay occurs, i.e. jet loses its strength. Finally, fully developed region
is the one where there is minimum variation with jet and surrounding air.
For the comparative purpose, NPR 3 and 5 are chosen for the study. Figure 3a,
b shows the CTPD results for NPR 3 and NPR 5, respectively. From Fig. 3a, the
supersonic core length has extended up to X/D p = 3.4 for lip thickness LT 2 mm (LT
0.3 D p ) whereas it is X/D p = 2.78 for lip thickness 7.75 mm (LT 1.2 D p ) which is
18% reduction in potential core length. But in characteristic decay region (CDR), LT
1.2 D p has decayed faster than LT 0.3 D p . For example, at X/D p = 6, LT 7.75 mm
has decayed 47% whereas LT 2 mm has decayed only 25%. Hence, the effect of lip
thickness is well pronounced in the CDR.
From Fig. 3b, the LT 2 mm has extended core of X/D p = 7.73 compared to LT
7.75 mm of X/D = 2.47 which is 65% reduction in potential core. The primary core
has been greatly reduced because of the interaction because of the interaction between
primary and secondary jets. The primary and secondary jets interact vigorously with
in a shorter axial distance due to the wave dominance. Mach disk is dominant with
CFJ with LT 7.75 mm and there is no Mach disk formed for CFJ with LT 2 mm.
R. Naren Shankar et al.
Fig. 3 a CTPD of lip 2 mm and 7.75 mm for NPR 3. b CTPD of lip 2 mm and 7.75 mm for NPR 5
reflect to form shock waves. This process continues till the supersonic flow becomes
subsonic. This region is called potential core length. Entrainment is the process of
momentum transfer between surrounding still air and the jet. Because of entrainment,
characteristic decay occurs, i.e. jet loses its strength. Finally, fully developed region
is the one where there is minimum variation with jet and surrounding air.
For the comparative purpose, NPR 3 and 5 are chosen for the study. Figure 3a,
b shows the CTPD results for NPR 3 and NPR 5, respectively. From Fig. 3a, the
supersonic core length has extended up to X/D p = 3.4 for lip thickness LT 2 mm (LT
0.3 D p ) whereas it is X/D p = 2.78 for lip thickness 7.75 mm (LT 1.2 D p ) which is
18% reduction in potential core length. But in characteristic decay region (CDR), LT
1.2 D p has decayed faster than LT 0.3 D p . For example, at X/D p = 6, LT 7.75 mm
has decayed 47% whereas LT 2 mm has decayed only 25%. Hence, the effect of lip
thickness is well pronounced in the CDR.
From Fig. 3b, the LT 2 mm has extended core of X/D p = 7.73 compared to LT
7.75 mm of X/D = 2.47 which is 65% reduction in potential core. The primary core
has been greatly reduced because of the interaction because of the interaction between
primary and secondary jets. The primary and secondary jets interact vigorously with
in a shorter axial distance due to the wave dominance. Mach disk is dominant with
CFJ with LT 7.75 mm and there is no Mach disk formed for CFJ with LT 2 mm.