Multi-Group Two-Phase Flow Model of Drift Drop Plume
Bibliographic record
Abstract
A homogeneous two-phase multi-group model of drift drop plumes emerging from natural draft cooling towers has been developed and validated using the experimental data obtained in the 1977 Chalk Point Dye Tracer Experiment (CPDTE). The conservation equations for mass fractions of water droplets having different sizes are solved in addition to the standard conservation equations for mixture mass, momentum, energy, water vapor mass fraction and turbulent quantities (turbulent kinetic energy and its dissipation rate). Extra terms are provided to the conservation equations for mass fractions of liquid water to account for the drift of water drops due to their gravitational settling. Various formulations for drift velocity and terminal velocity have been tested and compared. The phase change effects (condensation, evaporation, solidification and melting) are assumed to be negligible due to specific conditions of the experiment. The droplet-size distribution available at the cooling tower exit and containing the 25 groups of drops is simplified to 11 groups. Also, the 3-group and 1-group options are considered for comparison. The individual drop deposition fluxes and the total deposition flux are calculated and compared with the experimental data available at the sensors located on the 35° arcs at 500 and 1000 m from the cooling tower centerline. The total deposition flux is calculated as a sum of products of individual group mass concentrations of water drops and corresponding terminal velocities. The model has been incorporated into the commercial general-purpose Computational Fluid Dynamics (CFD) code, PHOENICS. The study has demonstrated a good agreement between the CFD predictions and the experimental data on the water vapor plume rise and the total drift deposition fluxes. In particular, the plume rise predictions agree well with experimental values (the errors are from 4% to 34% at different distances from the tower centerline). The predicted deposition fluxes are in agreement with the experimental values within a factor of 1.5, which is well within the industry acceptable error limits (a factor of 3). The model developed is recommended for analyzing the drift drop plumes under the conditions similar to CPDTE conditions of small Stokes numbers. It is easier to use and not less accurate than the multiphase Eulerian-Lagrangian CFD models used recently by various researchers for modeling CPDTE plume. The model has a potential to supplant or complement the latter in the computational analyses of gravitational phenomena in complex two-phase flows in engineering equipment and its environment.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.003 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".