Introduction • Got attention after the failure of Ariane 5 flight 501in July 1996 • Apart from the main cause, which was the control software bug, heavy side loads around the EPC (Vulcain) nozzle were also observed at the time of failure • At launch, the Vulcain engine is responsible to produce an enormous amount of thrust. The transonic free-stream flow from the outside of the main engine interacts with the high velocity supersonic flow forming a shear layer • The complex flow physics is expensive experimentally and numerical computation is helpful

1. BASE FLOW ANALYSIS OF ARIANE 5 USING RANS METHOD
Introduction
• Got attention after the failure of Ariane 5 flight 501in July 1996
• Apart from the main cause, which was the control software bug, heavy side loads around
the EPC (Vulcain) nozzle were also observed at the time of failure
• At launch, the Vulcain engine is responsible to produce an enormous amount of thrust.
The transonic free-stream flow from the outside of the main engine interacts with the
high velocity supersonic flow forming a shear layer
• The complex flow physics is expensive experimentally and numerical computation is helpful
Objective of the work
• Analyse the flow field through numerical simulation using Reynolds Averaged Navier-
Stokes (RANS) method and
• Comparison with experimental data

2. Flow conditions
• Mach number is 0.8 with free stream pressure of 1 bar and temperature of 300 K
• Booster nozzles had 30 bar inlet pressure, with T=350K, =1.4 while the Central Vulcain
nozzle Pressure=35 bar, T=350K, =1.4
• Working fluid was air because the experiment was performed with compressed air in the
main engine and the booster cannisters.
Mesh domain
Figure 1 Domain extents and mesh details
The mesh contained 2.4 million structured and hexahedral cells. The modified grid
consisted of 108 blocks

3. Structured solver was applied to remove negative Jacobians in the block.
T-Grid was also used to see the right-handed faces.
Turbulence models
 In RANS the following models were investigated
▪ Spalart Allmaras (S-A) (One Equation Turbulence Model)
▪ k-ε (Realizable) (Two Equation Model, one for Turbulent Kinetic
Energy and Dissipation rate)
▪ k-ω (Standard) (Two Equation Model, one for Turbulent KE and
Specific Dissipation Rate)
Results
Results of Cp were compared among different turbulence models. It was found that k- SST gave
the least error. Fig.2 shows effect of different models on the z-velocity with streamlines. The
result shows high levels of recirculation zone captured with inviscid (Euler) model while k- SST
captured intermittent level of circulation.
Table 1Results of Cp and comparison with experimental data with different turbulence models
Cp
Results
Cp-
Exp
Inviscid %error S-A %error K- %error K- %Error
P1 -0.168 -0.166 1.78 -0.052 68.80 -0.078 53.8 -0.109 35.11
P2 -0.115 -0.025 78.20 -0.053 53.15 -0.085 25.9 -0.123 6.96
P3 -0.260 -0.129 50.38 -0.264 1.50 -0.261 0.38 -0.250 3.77
P4 -0.250 -0.285 14.00 -0.267 6.80 -0.260 2.80 -0.2512 0.48

4. Figure 2 Contours of z-velocity and stream lines
Conclusion
For steady simulations k- performed better than the other two models
Difference in results is due to the presence of the Helium tank near the Vulcain
engine which was not modeled in CFD