DOI: 10.1615/TSFP3
EFFECTS OF VISCOELASTICITY AND COMPRESSIBILITY ON TURBULENCE STRUCTURE FORMATION
ABSTRACT
A process for formation of a vortex tube along a vortex sheet and its impact on turbulence generation is investigated in the homogeneous isotropic turbulence. It is shown that a vortex tube is generated along a flat sheet under compression of the vorticity in the stretching direction. In place of the compression and reduction of the vorticity in the stretching direction, the growth of the azimuthal vorticity takes place, and the azimuthal vorticity gradually accumulates to form the vortex tube. Then, the flat sheet folds around this concentrated vortex tube, forming the spiral vortex sheet emanating from the tube core. An intense generation of turbulence takes place along the flat sheet during this sheet-tube transformation process. The effect of viscoelasticity on this sheet-tube transformation process is studied using the approximate solution for the Oldroyd constitutive equation. It is shown that the transformation process is disrupted by pulling the flat sheet back to the original fiat shape, and subsequently turbulence generation is attenuated. Similar attenuation of occurrence of transformation process was found when the compressibility was introduced into the flow, but this attenuation was primarily attributed to the influence of the pressure-dilatation term.