Full text
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| Author(s): |
Walter Arias Ramirez
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Mecânica |
| Defense date: | 2016-01-25 |
| Examining board members: |
William Roberto Wolf;
Carlos Eduardo Keutenedjian Mady;
Sami Yamouni
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| Advisor: | William Roberto Wolf |
| Abstract | |
A numerical investigation is performed to assess the effects of trailing edge bluntness and trailing edge suction & blowing on airfoil self-noise generation and propagation. A suite of direct numerical simulations (DNS) are carried out for a NACA 0012 airfoil at different free-stream Mach numbers (Ma=0.1 to 0.3), angles of incidence (AoA = 0 and 3 deg.), and Reynolds numbers based on the airfoil chord (Rec=5000, 10000, 50000 and 100000). Two-dimensional simulations are performed for a NACA 0012 airfoil profile with two modified blunt trailing edges. The effects of suction and blowing on airfoil self-noise generation are also examined for the flow configurations above. A hybrid methodology that employs DNS for near-field source computations and the Ffowcs Williams--Hawkings equation as an acoustic analogy formulation is applied to quantify the individual contributions of the dipole and quadrupole sources to the total noise. Results for the low Reynolds number flows studied show that the airfoil emits a single "narrow-band'' tone, and that a thicker trailing edge produces higher noise levels than a thinner one due to an increase in the intensity and proximity of quadrupole sources to the airfoil surface. On the other hand, results for the moderate Reynolds number flows analyzed reveal that the airfoil emits multiple "narrow-band'' tones superimposed on a broadband hump depending on the flow configuration. These results indicate the existence of an acoustic feedback loop as discussed in literature. It is shown that the presence of the secondary tones is very dependent on compressibility effects, angle of incidence and trailing edge bluntness. For those cases where a broadband hump with multiple tones are observed, trailing edge blowing and suction considerably modifies the near-field hydrodynamic region responsible for noise generation and, for some of the flow configurations investigated, blowing can completely eliminate the tonal peaks. This work also shows in appendix A further details of novel numerical techniques which can be applied for the study of airfoil noise. This chapter is an outcome of a 6-month internship performed at Lawrence Livermore National Laboratory by the present author (AU) | |
| FAPESP's process: | 14/10166-6 - Tonal noise generation in blunt trailing edges |
| Grantee: | Walter Arias Ramirez |
| Support Opportunities: | Scholarships in Brazil - Master |