Noise mechanisms in a radial fan without volute
Bibliographic record
Abstract
Abstract The noise emission of a large radial fan with 7 backward curved blades is investigated. When decreasing the flow rate, the broadband levels below 1 kHz increase and the tones decrease, and a broad hump appears at about 80% of the BPF. The present numerical investigation aims at identifying the mechanism responsible for the broadband hump in the spectra. The configuration is simulated using the Lattice Boltzmann PowerFLOW solver for four flow-rate conditions. The low flow-rate condition is run longer to achieve statistical convergence at low frequencies. The simulations capture reasonably well the acoustic spectra and in particular the broadband hump at lower flow rate. The flow in the fan shows an unsteady flow detachment in some blade passages shed from the leading edge of the blade, while other blade passages experienced a fully detached flow along the whole blade chord. A spectral proper orthogonal decomposition is applied to identify the modal structures of the flow responsible for this mechanism. Several azimuthal modes are obtained from the decomposition for the different frequencies in the acoustic spectra. In addition an axial acoustic mode in the fan bowl is found at a frequency in the broadband hump.
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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 | 0.001 |
| 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".