Three-Dimensional Vortical Structure of a Large-Scale Coherent Vortex in a Turbulent Boundary Layer

Abstract

The streamwise evolution of three-dimensional structure of an artificially induced vortex was pursued by measuring velocity and vorticity fields through a simplified conditional sampling method. The artificial vortex developed downstream through the growth, the self-preserving and the decay stages. In the growth stage, the vortex grew up to have a horseshoe sculpture and the vorticity confined in it was increased downstream. The grown-up large-scale horseshoe vortex reached about 1.2δ in height, 1.0δ in width and 5.0δ in streamwise length. The vortex became more inclined forward and lost the ability of maintaining its self-similar construction in the decay stage. The convection velocity of the vortex’s head was 0.56 U _∞ in the foregoing two stages and was raised to 0.85 U _∞ in the decay stage.