Gas pressure gradients in unsaturated porous media and the assumption of infinite gas mobility
Bibliographic record
Abstract
Abstract The assumption that gas is infinitely mobile, moving without viscous pressure drops, is common in studies of unsaturated flow in porous media. The objectives of this work were to use experimental measurements to examine that assumption in systems experiencing rapid drainage and to explore the extent to which observed pressure drops could be described by conventional multiphase flow simulation tracking viscous flow in both phases. Because many published studies have used vented columns in an effort to equilibrate pore gas pressures with inlet gas, an additional objective of the work was to use experimental measurements to explore the ability of column vents to equilibrate pore gas with inlet gas during dynamic drainage. Results of the work suggest that gas pressure gradients can be significant, and that the assumption of infinite gas mobility is likely to be unsatisfactory in many systems where moderately rapid saturation change occurs. While vents have the potential to influence flow by providing additional gas inlets, experimental results of this work show almost no impact on pore gas pressures from a vent similar in size to those in other published studies. An equation developed as a part of the work suggests that the spatial slope of gas pressure with distance away from the front during dynamic drainage is proportional to the ratio of outflow Darcy velocity to saturated hydraulic conductivity for vertical columns. As such, systems with more rapid saturation change also have a greater potential to exhibit experimental artifacts related to gas pressure gradients.
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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 | 0.001 | 0.003 |
| 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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| 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 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".