Dynamics of a Cantilevered Pipe Aspirating Fluid and Subjected to Reverse External Flow: the Effect of External Flow Confinement
Bibliographic record
Abstract
Abstract The dynamics of a hanging cantilevered pipe aspirating fluid and simultaneously subjected to a partially confined external axial flow in the reverse direction has been investigated experimentally. A bench-top-size apparatus is used in this experiment consisting of a pressure vessel filled with water, a hanging cantilevered pipe and a shorter concentric outer rigid tube which is also vertically cantilevered. The flow configuration investigated in this paper is a simplified representation of the hydrocarbon storage mode of salt-mined caverns, which are large underground cavities used for storing hydrocarbons. An experimental investigation has been conducted to determine the effect of the size of the annular gap on the onset of instability for various external to internal flow velocity ratios, Uo/Ui, ranging from 0.015 to 0.80. It was found that, for the range of flow velocity ratios investigated, the pipe loses stability via first-mode flutter. For the lower ratios of flow velocity, namely Uo/Ui = 0.015–0.06, the bifurcation diagrams show an increase in the root-mean-square (rms) amplitudes at three different ascending rates as the internal flow velocity Ui increased. In contrast, for high flow velocity ratio bifurcation diagrams, i.e., for Uo/Ui = 0.40–0.80, there is an increase in rms amplitude at a certain rate, followed by a diminished rate of growth as the internal flow velocity is increased further. The results demonstrate that the onset of instability occurs at relatively lower flow velocities as the Uo/Ui ratio is increased. Moreover, enlarging the annular gap has a stabilizing effect on the aspirating pipe. In comparison with the narrower rigid tube, with a wider rigid tube the signal power of the second-mode frequency was significantly amplified.
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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 | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".