Scaling properties of two-dimensional turbulence in wakes behind bluff bodies

This paper contains an analysis of the scaling properties of two-dimensional (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 reduced inverse energy cascade. The concept of extended self-similarity (ESS) and the associated relative scaling exponents ζ-barm,n=ζn/ζm are invoked within the framework of 2D turbulence. The scaling exponents in the enstrophy range are found to systematically vary with the downstream distance from the obstacle, thus revealing their nonuniqueness. In terms of the relative exponents, the present results quantitatively agree with recent laboratory experiments of Gaudin et al. [PMMH-ESPCI Report No. A 96/57, 1996 (unpublished)]. Error bars and the accuracy of the ESS scaling are carefully checked.