Vibration and Work-Rate Measurements of Steam-Generator U-Tubes in Air-Water Cross-Flow
Bibliographic record
Abstract
In nuclear power plant steam generators, the vibration response of tubes in two-phase cross-flow is a general concern that in some cases has become a very real long-term wear problem. This paper summarizes the results of the most recent U-bend vibration-response tests in a program designed to address this issue. The tests involved a simplified U-tube bundle with a set of flat-bar supports at the apex, subjected to two-phase air-water cross-flow over the mid-span region of the U-bend. Tube vibration properties and tube-to-support interaction in the form of work-rates were measured over a wide range of flow velocities for homogeneous void fractions from zero to 90%, with three different tube-to-support clearances. The measured vibration properties and work-rates could be characterized by the relative influence of the two most important flow-induced excitation mechanisms at work, fluidelastic instability and random-turbulence excitation. As in previous similar tests, strong effects of fluidelastic instability were observed at zero and 25% void fraction for pitch velocities greater than approximately 0.5 m/s, whereas random turbulence dominated the tube vibration and work-rate response at higher void fractions. In both cases, a link between vibration properties and the effect of the flat-bar supports could be established by comparing the vibration crossing frequency, extracted from time-domain vibration signals, to the participation of the lowest few vibration modes and to the measured work-rate. This approach may be useful when fluidelastic instability, random turbulence and loose supports all combine to result in high work-rates. Such a combination of factors is thought to be responsible for excessive U-tube fretting-wear in certain types of operating steam generators.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".