Capillary pressure characteristics necessary for simulating DNAPL infiltration, redistribution, and immobilization in saturated porous media
Bibliographic record
Abstract
This study presents a capillary‐pressure saturation (PC‐S) constitutive model that incorporates the capillary phenomena necessary for simulating the spatial distribution of nonwetting fluid migrating in a saturated porous medium. To develop a model validation data set, a sequence of dense, nonaqueous phase liquid (DNAPL) pools were emplaced, under alternating drainage and imbibition conditions, in a one‐dimensional, 1 m tall, saturated sand pack. A light transmission/image analysis system successfully distinguished between connected‐phase and residual nonwetting fluid in the apparatus, thereby permitting the accurate measurement of DNAPL pool heights. These heights are found to depend on the nonzero capillary pressure across the fluid‐fluid interface at the top of the pool. The terminal pressure is demonstrated to be the minimum sustainable capillary pressure in connected‐phase nonwetting fluid experiencing imbibition, below which residual is formed. Additional bench‐scale experiments demonstrate that a nonwetting phase pool will penetrate an underlying capillary barrier when the entry pressure is exceeded and that the resulting infiltration will terminate when the capillary pressure at the barrier reduces to the terminal pressure. At the macroscopic scale the terminal pressure corresponds to the extinction saturation (i.e., zero nonwetting phase flow) at the inflection point on the imbibition PC‐S curve. A ratio of terminal to entry pressure of approximately 0.6 is found to apply at both bench and macroscopic scales and to be independent of porous media and fluid properties. The developed PC‐S constitutive model, which extends the Brooks‐Corey function to incorporate the terminal pressure, successfully predicted the behavior observed in the laboratory experiments. Constitutive models that do not incorporate both an entry and a terminal pressure, such as those based upon the standard van Genuchten function, are demonstrated to be unable to predict the observed equilibrium DNAPL pool heights in homogeneous media or above capillary barriers.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".