The Decay of Isotropic Turbulence
| Autor: | F. N. Frenkiel |
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| Rok vydání: | 1948 |
| Předmět: | |
| Zdroj: | Journal of Applied Mechanics. 15:311-321 |
| ISSN: | 1528-9036 0021-8936 |
| DOI: | 10.1115/1.4009853 |
| Popis: | The equation of decay of isotropic turbulence is determined in the two cases of large and small Reynolds number of turbulence by using the von Kármán-Howarth equations and applying Loitsianskii’s theorem of the conservation of the disturbance moment. The theoretical curves are compared with the results of measurements behind grids, made by various experimenters in the United States and in England. The decay of the longitudinal turbulent energy seems to agree quite well with the theoretical equations for large Reynolds number of turbulence. The theory does not give the variation of the transverse scale of turbulence measured in the experiments, but only the “disturbance length,” which is a function of the longitudinal correlation. Thus the comparison for the scale is only qualitative. It is not possible to show agreement with the theoretical variation of the scale deduced from the equations. The difference is explained by the imperfect isotropy, which has a much greater influence on the variation of the scale than it has on the energy decay. The present comparison of the theory with the experiments differs from similar prior comparisons by the fact that the decay is given as a function of the initial conditions of the turbulence at a chosen moment, without using arbitrary constants. |
| Databáze: | OpenAIRE |
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