DOI: 10.1615/TSFP6
FAR AXISYMMETRIC WAKES IN TURBULENT STREAMS
SINOPSIS
A time developing far axisymmetric wake at moderate Reynolds numbers (Re = O(104)) has been simulated without a generating body. When the wake achieved its self-similar state it was artificially combined with three different isotropic turbulent backgrounds with different intensities (u'bg = √u2). It was found that the presence of the background enhances the wake's decay rate to one which depends on the initial ratio of the free-stream turbulence intensity to the wake centre-line deficit velocity, u'bg/Ud. Moreover, the time required for enhancing the decay rate of the wake was also found to decrease with an increase in u'bg/Ud. In no case (with ubg > 0) did the wake achieve a self-similar state. Finally, rms turbulence levels inside the wake were clearly influenced and eventually dominated by the free stream levels. A tendency to isotropy in the rms normal stresses (i.e. u' ~ ν' ~ w') was noticed within the wakes, whilst the turbulence shear stress seemed to be largely maintained.