A numerical study of fan noise linked to imposed synthetic turbulence impinging the rotor
(English)Manuscript (preprint) (Other academic)
A study has been conducted to numerically examine the noise generation mechanisms associated witha low-speed fan operating in a turbulent-rich inﬂow. Although, the turbulent content in the upstreamﬂow is an important aspect of the noise characteristics associated with subsonic fans, it is often omittedin numerical investigation. In this paper the turbulent structures are generated by the synthetic eddymethod (SEM) which ensures that the vortical structures imposed on the inﬂow boundary are temporallyand spatially correlated. The ﬂow ﬁeld is resolved using the Improved Delayed Detached Eddy Simulation(IDDES), which enables in addition to the deterministic tonal components associated with the blade passingfrequency (BPF) and its harmonics, the continuous envelope of broadband noise associated with turbulenceto be scrutinized. In the present work, the noise produced from the tip leakage ﬂow is suppressed by aslightly less resolved tip region. Hence the eﬀect on the noise produced associated with both the inﬂowturbulence and the vortices in the tip region are examined. The sound pressure level (SPL) in the far-ﬁeldis obtained from the Ffowcs–Williams and Hawkings acoustic analogy. Validation with experimental resultsof a similar setup is provided. The results presented accentuates the need for properly constructed inletboundary conditions where turbulent structures, either part of the inﬂow or developed in the tip region,reinforce the noise produced.
Fan noise, aeroacoustics, IDDES, SEM, FW-H
Fluid Mechanics and Acoustics
Research subject Vehicle and Maritime Engineering
IdentifiersURN: urn:nbn:se:kth:diva-199279OAI: oai:DiVA.org:kth-199279DiVA: diva2:1061733
QC 201601042017-01-032017-01-032017-01-04Bibliographically approved