A Critical Review of the Correlations Used for Predicting the Onset of the Transition Flow Regime in Pipe Flow of Yield Stress Fluids
Bibliographic record
Abstract
Abstract In this paper, we present a critical review of the models used for predicting onset of the transition flow regime in pipe flow of yield stress fluids. Using the experimental data obtained by the Particle Image Velocimetry (PIV) technique, we developed a new methodology to identify the beginning of the transition flow regime in pipe flow of yield stress fluids. The new method was then used to evaluate the accuracy of the existing transition flow regime model predictions. The proposed approach relies on the boundary layer theory to classify flow into laminar and turbulent. The boundary layer theory enables microscopic characterization of the flow transition that translates into a more in-depth fundamental understanding of the transition phenomena. The corresponding literature, experimental validation, and proof of the concept are presented. We investigated 36 possible permutations of Reynolds number (Re) and critical Reynolds number (Recrit.) definitions (i.e., six Re definitions combined with six critical Re definitions), and in none of these cases, the onset of the transition regime was accurately and consistently predicted. It was noted that the percentage difference between the maximum and minimum values of Re, for the same flow rate and fluid properties, ranged between 27% to 58%, based on fluid properties and flow rate combination, mainly because of the subjectivity of the Re definitions. In order to ensure an accurate prediction of the transition zone, test fluids were designed to have a wide range of generalized Reynolds numbers (i.e., 20 to 9000, as defined by the API-RP:13D) within the physical capacity of the experimental facility (i.e. for a given pipe diameter, maximum pressure capacity of the flow loop and maximum available pump flow rate). The yield stress of the test fluids varied from 0.10 to 0.95 Pa (determined by using the nonlinear curve fitting technique recommended by the API RP:13-D). Results indicated that most of the current transition criteria for the pipe flow of yield power law (YPL) fluids have low accuracy and lack of consistency to predict the onset of the actual transition regime as compared to the data measured by using the PIV technique. This was regardless of the Reynolds number definition used. The proposed PIV measurement-based criterion provides an objective measure that can be used to develop more accurate future transition models or improve the accuracy of existing transition criteria.
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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 | 0.008 | 0.016 |
| Meta-epidemiology (narrow) | 0.002 | 0.002 |
| Meta-epidemiology (broad) | 0.003 | 0.002 |
| Bibliometrics | 0.008 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.004 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".