Experimental Investigation of the Effect of Azimuthal Spacing on the Performance of a Stacked Rotor in Hover and Forward Flight
Bibliographic record
Abstract
The unconventional configuration of a 2 × two-bladed stacked rotor with a diameter of 0.82 m is studied experimentally throughout this paper. With the rotational speed kept constant at 2453 RPM and the dimensionless axial spacing fixed at 0.06, the main objective is to assess the effect of azimuthal spacing across multiple configurations in forward flight, varying the shaft angle and freestream velocity. First, an analysis of the baseline rotor in forward flight is presented, featuring four blades evenly spaced in a single plane. This is followed by results for the stacked rotor in hover flight, revealing a consistent trend with the literature: a low-performance region offering lower blade loading values for smaller azimuthal spacings, when both rotors closely overlap, and a region of increased performance for larger azimuthal spacings in both positive and negative directions. Most azimuthal spacings exhibit higher performance relative to the baseline rotor, with a maximum positive change of 7.82%. Finally, a performance comparison between the baseline rotor and the stacked rotor in forward flight reveals a similar trend to hover flight regarding the low-performance region for small azimuthal spacings, but with a less significant region where the stacked rotor outperforms the baseline rotor. Moreover, the vibratory loads of the stacked rotor depend on the azimuthal spacing, varying from a two-per-revolution harmonic at an azimuthal spacing of 0° to a four-per-revolution harmonic at 90°, resulting in higher vibratory loads transmitted to the rotor hub when the blades of both rotors are unevenly spaced.
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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 | 0.000 |
| 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 | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".