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R. Naren Shankar et al.
1 Introduction
Supersonic jet finds application in rockets, missiles, fuel injectors, commercial, and
fighter jet exhausts [1]. Supersonic co-flowing jet (CFJ) is beneficial in mixing
enhancement and in jet noise reduction. It overtakes the usage of tab and chevron
because there is no blockage and reduces manufacturing complexity respectively.
Subsonic secondary jet eliminates Mach wave of supersonic primary jet [2].
Surrounding jet elongates central jet potential core length by 68% when compared
to single free jet [3]. Sukumar et al. [4] studied under-expanded and Sharma et al. [5]
studied over-expanded central jet with surrounding subsonic and sonic flow. Both
reported co-flow inhibits mixing because the lip thickness (LT) value ranges from
0.7 to 3 mm. Satyajit et al. [6] studied mixing characteristics supersonic CFJ with
constant finite LT 7.75 mm at nozzle pressure ratios (NPR) ranging from 3 to 8
in steps of one. The effect of lip thickness has not been addressed. Subsonic and
correctly expanded sonic CFJ were studied with varying lip thickness by Naren et al.
[7–11]. But they have not analyzed supersonic flow. The present study is the first
effort to study supersonic CFJ with varying lip thickness numerically.
2 Numerical Details
The supersonic co-flowing nozzle (Fig. 1) used in the current study is acquired from
Satyajit et al. [6]. The primary nozzle has inlet diameter 10 mm, throat 5 mm, and exit
6.5 mm. The secondary nozzle has inlet width (outer diameter minus inner diameter)
of 6 mm, throat width of 1 mm, and exit width of 1.65 mm. The geometry was
created in CATIA, ICEM CFD is used for meshing and ANSYS CFX solver is used
for numerical analysis. The fluid is set to ideal gas. Compared to other models, the
SST turbulence model is better in capturing the shear layers. The total temperature
of 298 K is taken to match with the experimental conditions. At inlet, corresponding
pressure value of NPR 3 and NPR 5 is set. No-slip adiabatic wall function is chosen
for the nozzle wall. The average static pressure is 1 atm at outlet, and the equations
are converged to a minimum error of 10
−4 [12, 13].
A coarse grid with 0.55 million nodes, medium grid with 1.1 million nodes, and a
fine grid with 2.2 million nodes were created for grid independence study. Figure 2
shows the validation plot for the nozzle pressure ratio (NPR) 5. The results show that
numerical simulation has good agreement with experimental curve.
R. Naren Shankar et al.
1 Introduction
Supersonic jet finds application in rockets, missiles, fuel injectors, commercial, and
fighter jet exhausts [1]. Supersonic co-flowing jet (CFJ) is beneficial in mixing
enhancement and in jet noise reduction. It overtakes the usage of tab and chevron
because there is no blockage and reduces manufacturing complexity respectively.
Subsonic secondary jet eliminates Mach wave of supersonic primary jet [2].
Surrounding jet elongates central jet potential core length by 68% when compared
to single free jet [3]. Sukumar et al. [4] studied under-expanded and Sharma et al. [5]
studied over-expanded central jet with surrounding subsonic and sonic flow. Both
reported co-flow inhibits mixing because the lip thickness (LT) value ranges from
0.7 to 3 mm. Satyajit et al. [6] studied mixing characteristics supersonic CFJ with
constant finite LT 7.75 mm at nozzle pressure ratios (NPR) ranging from 3 to 8
in steps of one. The effect of lip thickness has not been addressed. Subsonic and
correctly expanded sonic CFJ were studied with varying lip thickness by Naren et al.
[7–11]. But they have not analyzed supersonic flow. The present study is the first
effort to study supersonic CFJ with varying lip thickness numerically.
2 Numerical Details
The supersonic co-flowing nozzle (Fig. 1) used in the current study is acquired from
Satyajit et al. [6]. The primary nozzle has inlet diameter 10 mm, throat 5 mm, and exit
6.5 mm. The secondary nozzle has inlet width (outer diameter minus inner diameter)
of 6 mm, throat width of 1 mm, and exit width of 1.65 mm. The geometry was
created in CATIA, ICEM CFD is used for meshing and ANSYS CFX solver is used
for numerical analysis. The fluid is set to ideal gas. Compared to other models, the
SST turbulence model is better in capturing the shear layers. The total temperature
of 298 K is taken to match with the experimental conditions. At inlet, corresponding
pressure value of NPR 3 and NPR 5 is set. No-slip adiabatic wall function is chosen
for the nozzle wall. The average static pressure is 1 atm at outlet, and the equations
are converged to a minimum error of 10
−4 [12, 13].
A coarse grid with 0.55 million nodes, medium grid with 1.1 million nodes, and a
fine grid with 2.2 million nodes were created for grid independence study. Figure 2
shows the validation plot for the nozzle pressure ratio (NPR) 5. The results show that
numerical simulation has good agreement with experimental curve.