Comment on the paper of Jaffe et al (astro-ph/0503213) on evidence of vorticity and shear of the Universe We show that recent results in the paper of Jaffe et al on evidence of vorticity and shear of the Universe are incorrect. They fit WMAP data with certain Bianchi model which is known to have a vanishing vorticity. The performed fit of the shear is not reliable because the respective formula...

The nature of vorticity transport in three-dimensional turbulent flow is investigated using data from a direct numerical simulation of channel flow. An extension of Taylor's (1932) vorticity transport theory is derived by a formal Lagrangian analysis in which care is taken to include nongradient transport effects associated with vortex stretching and shearing. A comparison is made between the p...

Λ-vortex plays a critical role in the boundary layer transition process. In this paper, the mechanism of Λ-shaped rotational core formation is studied by DNS. The Blasius velocity profile is found to be the vorticity resource. The aggregation of vorticity (vortex filaments) is caused by the 2-D T-S wave. The mechanism of clustering of spanwise vorticity by 2-D T-S wave to form vortex tubes is s...

Local and nonlocal contributions to the total strain rate tensor S(ij) at any point x in a flow are formulated from an expansion of the vorticity field in a local spherical neighborhood of radius R centered on x. The resulting exact expression allows the nonlocal (background) strain rate tensor S(ij)(B)(x) to be obtained from S(ij)(x). In turbulent flows, where the vorticity naturally concentra...

The question of vortex growth in Euler flows leads naturally to the emergence of paired vortex structure and the “geometric” stretching of vortex lines. In the present paper, the first of two papers devoted to this question, we examine bounds on the growth of vorticity in axisymmetric flow without swirl. We show that the known bound on vorticity in this case, exponential in time, can be improve...

INTRODUCTION Theoretical analysis, experimental observations, and numerical simulations have all indicated that flame-vortex interactions play an important role in the propagation and extinguishment of turbulent flames in microgravity [1]. Most studies of flame-vortex interactions ignore the effects of gravity and experiments are usually conducted in Earth gravity. Recently, Sinibaldi et al. [2...