SCALING PROPERTIES OF 2-DIMENSIONAL TURBULENCE IN WAKES BEHIND BLUFF-BODIES

This paper contains an analysis of the scaling properties of two-dimen sional (2D) turbulence obtained by means of numerical simulation using the vortex blob method. The flow under consideration is the turbulent wake behind a bluff body with a developed enstrophy cascade and reduc ed inverse energy cascade. The concept of extended self-similarity (ES S) and the associated relative scaling exponents <(zeta)over bar>(m,n) =zeta(n)/zeta(m) are invoked within the framework of 2D turbulence. Th e scaling exponents in the enstrophy range are found to systematically vary with the downstream distance from the obstacle, thus revealing t heir nonuniqueness. In terms of the relative exponents, the present re sults quantitatively agree with recent laboratory experiments of Gaudi n et al. [PMMH-ESPCI Report No. A 96/57, 1996 (unpublished)]. Error ba rs and the accuracy of the ESS scaling are carefully checked.