Enstrophy Study of the Turbulent Swirling Flow in Pipe

Abstract

Turbulent swirling flow is characterized by significant vortex fluctuations, intensive diffusion processes and energy cascade transfer from larger to smaller vortices over a continuous spectrum of wave numbers. The dissipation of the kinetic energy of turbulence occurs in the smallest vortices, because in these areas, both the velocity gradients and the deformation velocities are the largest. In this paper is analyzed turbulent swirling flow in pipe, generated by the axial fan impellers for three various blade angles (22°, 26° and 30°). Vorticity, enstrophy and lambda 2 values are calculated in order to study the structure of the generated turbulent swirling flows. Axial fan impeller operates in the region of lower flow rates, and it is shown that blade angle doesn’t influence much on the integral flow parameters, as well as on the enstrophy distribution. It is, also, shown that the dissipation of the kinetic energy of turbulence is associated with the vorticity fluctuations, i.e. with turbulent fluctuating enstrophy. All these distributions are obtained by use of the high speed particle image velocimetry data and provided velocity fields. Enstrophy is directly related to the kinetic energy, i.e. it corresponds to dissipation effects in this flow. It has maximum in small vortices, i.e. in shear layer, that surrounds vortex core region, where the process of turbulence kinetic energy dissipation occurs.