1
مکانیک::
نیمه تجربی
Such an approximation is valid only for weakly nonlinear systems such as the weak wave turbulence described in Section 6.4 below; for hydrodynamic turbulence it is a semi-empirical approximation which was extensively used for the next forty years.
That semi-empirical model is a significant step forward compared with the earlier models of Prandtl, von Ka�rma�n and Taylor, where the Reynolds equations for mean velocity were closed by hypothetical algebraic equations for Reynolds stresses.
Obukhov developed a semi-empirical approach based on a sys- tematic use of universal dimensionless functions.
As we now believe, direct turbulence cascades (from large to small scales) have, at a fundamental level, nothing to do with either Gaussianity or self-similarity, even though these concepts can help to design useful semi-empirical models for ap- plications.
The argument of Batchelor & Townsend (1947) rests on the semi-empirical observation of apparent approach to constancy of the skewness factor with increasing Reynolds number, but anything approaching a proof of this sort of result is still lacking.
واژگان شبکه مترجمین ایران