**The transient run plateaus around 1.1 MN which matches the steady-state solution.
Transient simulation was stopped at 0.025 seconds run time.
Thrust definition
Inspiration: Based on the “Design and analysis of morphing rocket nozzle for thrust vector control” concept on GrabCAD, but morphing/TVC was intentionally removed for this exercise. The model here is a fixed, 2D axisymmetric bell nozzle sized for clarity and repeatability. exit diamter: 1.24 meters
Reference: https://grabcad.com/library/design-and-analysis-of-morphing-rocket-nozzle-for-thrust-vector-control-1
Coordinate system: Axisymmetric (x along centerline, r radial).
- 2D axisymmetric: captures startup physics (shock/expansion pattern and plume development).
- Initial Condition Air mass fraction ≈ 1 in entire domain.
| Species | Formula | Fraction | Percentage |
|---|---|---|---|
| Water | H₂O | 0.291 | 29.1% |
| Carbon Dioxide | CO₂ | 0.227 | 22.7% |
| Carbon Monoxide | CO | 0.056 | 5.6% |
| Hydrogen | H₂ | 0.048 | 4.8% |
| Oxygen | O₂ | 0.007 | 0.7% |
| Nitrogen | N₂ | 0.371 | 37.1% |
| Total | — | 1.0 | 100% |
Pressure ramp used in the transient:
2D axisymmetric mesh:
Wall Y+ hits exactly 1 at the nozzle exit last cell K-omega SST turbulence model was used for this exersize Key settings: Δt = 1e−6 s, total simulated time = 0.025 s, implicit transient, ~25 inner iterations/step.
Thrust was computed at the exit plane: area-weighted Mdot, Velocity, and Pressure; subtract P_infinity. Domain & outlet: Ensure far-field is large and non-reflecting.
Expectation: Once the ramp completes and the exit plane stabilizes, the transient time-average will rise toward the steady ≈1.1 MN.