Liquid Slug Motion in Vertical Risers with Limited Ventilation
Bibliographic record
Abstract
Dangerous intermittent slug flows occur when large air pockets entrapped in deep tunnels escape from vertical risers, a phenomenon known as stormwater-induced geysers. Although the dynamics of liquid slug flow in fully ventilated pipelines has been well studied, investigations on the mass shedding of liquid slugs moving in vertical risers with a top orifice are lacking. By means of a three-dimensional computational fluid dynamics model, the dynamic behavior of liquid slugs with different initial slug lengths under different driving pressures and orifice openings was analyzed. Experiments were conducted to provide physical insights and data for model validation. It was found that the length of the rising liquid slug decreased due to a constant mass shedding rate. The latter was independent of the driving pressure and initial slug length, but dependent on the size of the orifice at the top end. The velocities of the slug’s tail and front were linearly related via the mass shedding rate. In the fully open riser, the net force driving the slug decreased but remained positive in the geyser event, while in the riser with limited ventilation it depended on both the driving air pressure and the orifice size and could become negative. A new relationship between the air bubble nose velocity, the water slug front velocity, and the film flow velocity has been derived. The upward film flow velocity can be laminar or turbulent. Moreover, a relationship between the film thickness, mass shedding rate, and pipe diameter has been derived.
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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 | 0.001 |
| 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".