Fuente: Nature Physics - Issue - nature.com science feeds
Expuesto el: domingo, 23 de mayo de 2010 2:00
Autor: Tuan Tran
Asunto: Macroscopic effects of the spectral structure in turbulent flows
| Macroscopic effects of the spectral structure in turbulent flows Nature Physics 6, 438 (2010). doi:10.1038/nphys1674 Authors: Tuan Tran, Pinaki Chakraborty, Nicholas Guttenberg, Alisia Prescott, Hamid Kellay, Walter Goldburg, Nigel Goldenfeld & Gustavo Gioia There is a missing link between the macroscopic properties of turbulent flows, such as the frictional drag of a wall-bounded flow, and the turbulent spectrum. The turbulent spectrum is a power law of exponent α (the 'spectral exponent') that gives the characteristic velocity of a turbulent fluctuation (or 'eddy') of size s as a function of s (ref. 1). Here we seek the missing link by comparing the frictional drag in soap-film flows, where α=3 (refs 9, 10), and in pipe flows, where α=5/3 (refs 11, 12). For moderate values of the Reynolds number Re, we find experimentally that in soap-film flows the frictional drag scales as Re-1/2, whereas in pipe flows the frictional drag scales as Re-1/4. Each of these scalings may be predicted from the attendant value of α by using a new theory, in which the frictional drag is explicitly linked to the turbulent spectrum. |
