Blunt Trailing Edge Profiled Body Wake Control Using Synthetic Jets
Bibliographic record
Abstract
The three-dimensional structure of turbulent blunt trailing edge body wakes is experimentally investigated with and without forcing. The intrinsic effect of boundary layer transition on the frequency of vortex shedding and its three-dimensional structure is explored. Disturbances in the shear layers are amplified as the boundary layers transition and this is associated with more phase variations in the vortex shedding along the span and the more frequent occurrence of vortex dislocations. In contrast, it is found that the shedding phase drift does not change significantly with the boundary layer thickness in the turbulent boundary layer regime. These changes in the wake three-dimensionality are linked to the spanwise correlation of the streamwise velocity, as well as the relative strength of the vortex shedding compared to the turbulent fluctuations in the wake. Furthermore, a coherent secondary instability vortical structure is identified in the wake in all of the investigated cases. The spanwise wavelength of this structure is measured to be approximately 0.8 times the body thickness, d, irrespective of the state of the boundary layers and their thickness, and it is identified as the mode B instability originally reported in cylinder wakes. An array of synthetic jets on the body is used to force the vortex shedding into a different three-dimensional configuration. The jets are located near the trailing edges of the body and distributed symmetrically on both sides with a uniform spanwise spacing of 2.4d. The forcing partially tilts the von Karman vortices into the streamwise direction and induces the formation of coherent streamwise vortex loops. This reorientation of the wake vorticity is associated with the attenuation of the vortex street and drag reduction. The effect of forcing amplitude and low-frequency modulation on the drag reduction and the structure of the wake is examined. The greatest drag reduction of approximately 25% is achieved when the vortical structures emitted by the jets penetrate up to the edge of the boundary layers of the body. Evidence is presented that the greatest drag reduction occurs when the vortex street is most tilted into the streamwise direction by the forcing.
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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 | 0.000 |
| 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 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".