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Noise radiated by low-Reynolds number flows past a hemisphere at Ma=0.3

Huadong Yao (Institutionen för tillämpad mekanik, Strömningslära) ; Lars Davidson (Institutionen för tillämpad mekanik, Strömningslära) ; Lars-Erik Eriksson (Institutionen för tillämpad mekanik, Strömningslära)
Physics of Fluids (1070-6631). Vol. 29 (2017), 7, p. Article no 076102 .
[Artikel, refereegranskad vetenskaplig]

Flows past a hemisphere and their noise generation are investigated at the Reynolds numbers (Re) of 1000 and 5000. The Mach number is 0.3. The computational method of the flows is large eddy simulation. The noise is computed using the Ffowcs Williams and Hawkings Formulation 1C (F1C). An integral surface with an open end is defined for the F1C. The end surface is removed to reduce the numerical contamination that is introduced by vortices passing this surface. However, the contamination cannot be completely reduced since a discontinuity of the flow quantities still exists at the open surface boundary. This problem is solved using a surface correction method, in which a buffer zone is set up at the end of the integral surface. The transformation of flow structures due to Re is explored. Large coherent structures are observable at low Re, whereas they diminish at high Re. A large amount of small-scale turbulent vortices occur in the latter case. It is found that these characteristics of the flows have an important influence on the noise generation in regard to the noise spectra. In the flows studied in this work, the fluctuating pressure on the walls is a negligible noise contributor as compared with the wake.

Nyckelord: sound generation, acoustic analogy, boundary-conditions, aerodynamic sound, computation, formulation, surfaces



Denna post skapades 2017-08-23. Senast ändrad 2017-10-03.
CPL Pubid: 251335

 

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Institutioner (Chalmers)

Institutionen för tillämpad mekanik, Strömningslära (2005-2017)

Ämnesområden

Strömningsmekanik

Chalmers infrastruktur