摘要

Coherent structures were investigated in a round jet of heated air with temperature difference, 0-200K. The present jet was vertically ejected in a cross flow field with large-scale turbulence, grid turbulence and low-turbulence. Six kinds of jet structure were observed by flow visualization: (I) two vortex tubes disconnected by bifurcation, (II) two vortex tubes mutually interacted each other, (III) hairpin-type vortices, (IV) meandering jet structure with both of coherent vortices and turbulent eddies and (V) downwash structure.Vortex behavior, the convection velocity of the coherent vortices, the Strohal number, etc., was investigated from the results of motion pictures taken by a high speed camera.