CFD Analysis for Simulated Altitude Testing of Rocket Motors
Bibliographic record
Abstract
This paper deals with the high-altitude simulation and testing of upper stage rocket motors with large-nozzle area ratios, using second-throat exhaust diffusers (STED). To evaluate the performance of such motors, the low-pressure environment of the flight situation has to be simulated in the ground-testing installation. The shock pattern developed outside the rocket nozzle in the diffuser system can effectively seal the vacuum test chamber and maintain the required low-vacuum condition in the test chamber. An attempt has been made, in the present study, to numerically compute the flow field in a STED coupled with a large vacuum chamber, for simulating the entire high-altitude-test configuration of a rocket motor. Simulations have been carried out for both cold- and hot-flow situations and for cases with and without a large vacuum chamber. The computational results compare favorably with available experimental results for both hot (γ = 1.2)-flow and cold (γ = 1.4)-flow situations. The operational characteristics of the STED system and the associated flow structure are discussed in detail.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".