Hydraulic Resonance During Startup of a High Head Francis Turbine
Bibliographic record
Abstract
Abstract During the startup of a horizontal high-head Francis turbine, significant axial vibrations occurred at sub-synchronous speeds. The issue was exasperated by the low axial stiffness of the bearings. The vibration amplitude increased with speed, suggesting resonance tuning rather than self-excitation. Further evidence of resonance came from the site measurements that showed a beat-like signal in the draft tube pressure pulsations and synchronised draft tube and casing pulsations. Additionally, the measured draft tube pressure pulsations exhibited spike-like shapes, which are indicative of large cavitation volume implosions. The source of the excitation was identified, through CFD simulations, as a rope-like vortex beneath the runner, which generated both small asynchronous and large synchronous pulsations. The corresponding frequency matched well with the excitation frequency measured at site thus supporting the hypothesis of hydraulic resonance. The same normalized frequency was also observed in the model test on the dynamic pressures providing further support of the hypothesis.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".