Oil‐water core‐annular flow in vertical pipes: A CFD study
Bibliographic record
Abstract
Oil‐water core‐annular flow has the potential to significantly reduce the pumping power required for heavy oil transportation. We study axisymmetric, laminar‐laminar oil‐water core‐annular flow in a pipe (radius 14.2 mm) under three different channel conditions: vertically upward flow, vertically downward flow, and without considering the gravitational effect. For the ‘no‐gravity’ case, a smooth oil‐water interface is obtained and the results correspond to the analytical solution for a ‘fully‐developed’ annular flow. For the vertically upward flow, ‘saw‐tooth’ waves are observed at the interface. No perturbations are introduced to the flow initially; the interfacial waves take shape from the interplay between buoyancy, viscous force, and interfacial tension. CFD simulations are compared with published experimental observations, and found in qualitative agreement with each other. Both the CFD simulations and experiments show the wave amplitude reducing with increasing oil flow rate while keeping the water flow rate constant for a vertically upward flow. CFD simulation for a vertically downward flow shows the presence of very short waves of small amplitude, and the mean interfacial radius is larger than for the no‐gravity case. Moreover, the maximum velocity in the annular water film occurs between the interface and the wall, unlike the upward and no‐gravity cases where the maximum velocity in the water film occurs at the interface.
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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 | 0.000 |
| 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".