Vortex Spoilers Do Not Work to Suppress Pulsations Generated by Turning Flows Into a Side Branch Against a Deadleg
Bibliographic record
Abstract
Abstract Turning flow into side branches against a deadleg along the main run can generate high levels of pulsations if the piping system acoustic resonance frequency matches closely the flow generated instabilities within the T-junction characterized by specific Strouhal number (St) that is function of the branch to main run diameters ratio (d/D). In order to suppress these pulsations, vortex spoilers (aka vortex breakers), akin to those employed and inserted inside the side branch to suppress pulsations generated due to flow past side branches, have been considered. The difference lies in the fact that these spoilers would have to be placed in the main-run close to the downstream trailing edge of the T-junction. Three spoilers of different geometries and characteristics were designed and tested experimentally on a high-pressure natural gas test setup at a pressure range of 4–5 MPa, mean gas velocities of 6–36 m/s in a DN100 piping arrangement and for d/D = 1.0. These spoilers are flat plate, perforated plate, and cross-plates all of length = 2.1D. Tests were carried out at different positions of the respective spoilers in relation of the T-junction intended to interfere and suppress the coherent vorticity generation and its interaction with the mean flow velocity and acoustic fields according to Howe acoustic source power theory. The paper presents details of the test setup, data collected, analysis of the normalized pulsation amplitude (P*) vs. St number and effectiveness of each of the three spoilers at three different positions inside the main run. It was found that the maximum amplitude of P* without spoilers was reached at St number approximately equals to 0.12 which is close to published data. However, none of the tested three spoilers was effective in suppressing the level of pulsations irrespective of their placement position inside the main run. It appears that due to the fact that the flow has to turn into the side branch, a high degree of shearing resulting in regions of high vorticity generation, combined with the predominant direction of the mean flow into to the side branch, all of which contribute to the acoustic power source, regardless of any interference or potential interference brought about by any spoiler. Complementary unsteady CFD simulations were also conducted on a similar experimental setup on air under well-defined flow and acoustic boundary conditions published in IMECE 2021. The combined experimental and CFD simulations concluded with that vortex spoilers appear to be of no use in suppressing pulsations generated by turning flows into a side branch against a deadleg at least in the range of spoiler placement positions studied.
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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 | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".