Resumo (PT):
The equations governing the dynamics of large-scale perturbations superimposed on incompressible small-scale flow driven by a force have, under suitable conditions, the same structure as Navier-Stokes equations. The breaking of Galilean invariance due to the presence of the small-scale flow will, in general, induce a ¿vertex renormalization¿: the constant a in front of the advective nonlinearity does not remain equal to unity. A class of basic flows where the calculation of a a can be performed analytically is discussed. For finite Reynolds numbers, the constant a can indeed be very different from unity and can also vanish. The Reynolds number and the dynamics of a large-scale flow can then be quite different than predicted by setting a=1.
Abstract (EN):
The equations governing the dynamics of large-scale perturbations superimposed on incompressible small-scale flow driven by a force have, under suitable conditions, the same structure as Navier-Stokes equations. The breaking of Galilean invariance due to the presence of the small-scale flow will, in general, induce a 'vertex renormalization': the constant a in front of the advective nonlinearity does not remain equal to unity. A class of basic flows where the calculation of a can be performed analytically is discussed. For finite Reynolds numbers, the constant a can indeed be very different from unity and can also vanish. The Reynolds number and the dynamics of a large-scale flow can then be quite different than predicted by setting a = 1.
Idioma:
Inglês
Tipo (Avaliação Docente):
Científica
Nº de páginas:
6