Visualization of Continuous Stream of Grid Turbulence Past the Langston Turbine Cascade
Bibliographic record
Abstract
This paper describes a direct numerical simulation visualization study on the migration and distortion of a continuous stream of grid turbulence passing through a representative turbine cascade with and without being segregated by the blade leading edge. For the nonimpinging case, as the turbulent stream starts to enter the turbine cascade, there is a coarsening and reorientation of the small-scale and random grid-turbulence structures into short vortex tubes; inside the cascade, these short vortex tubes are further stretched into relatively long quasi-streamwise vortices. For the impinging case, very long streamwise vortices on the pressure surface are observed that correspond nicely to the “colored-fingers” phenomenon reported in previous turbine heat transfer experiments. The spanwise locations of the observed vortices vary with time. The origin of such turbine pressure-side streamwise vortices is revealedusing a relatively complete sequence of images documenting their life cycle. For the impinging case, the short vortex tubes formed at the stagnation are gradually distorted into the shape of a hockey stick. The long stick is nearly parallel to the blade pressure surface, whereas the short end is bent toward the freestream. This process can be well explained by invoking results from previous fundamental studies on simple stagnation flows and on the stretching and rotation of material lines by the mean strain-rate field under the assumption of rapid distortion. Taken together with earlier investigations on turbine distortion ofmigrating planarwake andmigrating isolated turbulent block, it is quite likely that Taylor–Goertler centrifugal instabilitymay not be an important player in the formation of pressureside elongated streamwise vortices in turbomachinery applications.
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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".