Jet force

Abstract: : A detailed numerical investigation of the interaction between a lateral jet and the external flow has been performed for a variety of missile body geometries. These include non-finned axisymmetrical bodies and finned bodies with either strakes or aft-mounted tail fins. The computations were performed at Mach numbers 2, 4.5, and 8. To obtain the numerical results, both Reynolds- averaged Navier-Stokes and Euler techniques were applied. The computational results were compared with results from a previously published wind tunnel study that consisted primarily of global force and moment measurements. The results show significant interactions of the jet-induced flow field with the fin surfaces, which produce additional effects compared with the body alone. In agreement with the wind tunnel study, in some cases the presence of lifting surfaces resulted in force and/or moment amplification of the jet interaction with the missile surfaces. The results indicate deamplification of the jet force at Mach 2 for all three bodies. Amplification of the jet force was also observed for high Mach numbers, particularly for the body with strakes. For the results examined here, there were only minor differences in the global force and moment predictions when viscous or inviscid techniques were used. The dependence of the interaction parameters on angle of attack and jet pressure was well predicted by both methods. The numerical techniques showed good agreement with the experiments at supersonic Mach numbers but only fair agreement for the hypersonic, Mach 8 case.

Abstract: The flow interaction effects from a jet issuing into a supersonic crossflow are investigated using computational fluid dynamic simulations of a basic fin-stabilized projectile at moderate positive and negative angles attack. Data was generated for a high-pressure ratio jet located at seven locations along the projectile axis. Crossflow Mach numbers of 1.5, 2.5, and 3.5 were investigated for an angle of attack range of -10° ≤ α ≤ 10°. Flowfield visualizations indicated the size of the jet plume and the size of the resulting low-pressure region behind the jet were reduced as Mach number increased. The jet force amplification factor showed more variation as α became more negative. The effective jet location was found to vary little for α > -5° at Mach 2.5 and 3.5. For α > -5°, there was less variation of force amplification factor a Mach number increased. Flight simulations using reaction jet “squibs” were performed to evaluate the sensitivity of the control maneuver to the differences in jet thrust and jet actuation location. These results showed that significant differences in the projectile maneuver control were obtained if the effective jet thrust acting at the effective jet location were used instead of the ideal jet thrust acting at the jet exit location.

Abstract: Jet penetration, bubble dispersion, and liquid splash were studied in the nitrogen-water system. Among the effects evaluated were those due to lance design, nozzle dimensions, gas driving pressure, and liquid density. In side-nozzle injection, penetration is found to increase with jet force number,N, given by the product of the gas driving pressure and the nozzle diameter. In top-submerged injection, horizontal and vertical penetrations increase with the horizontal and vertical components, respectively, of the jet force number. Liquid splash is greater in the side-nozzle injection than in top-submerged multiple-orifice injection, and appears to decrease as the number of orifices increases.