Abstract
In order to develop a new mixing procedure, we conduct DNS (direct numerical simulation) of dynamic controlled free jets. As the dynamic control, it is assumed that the inflow of jet rotates around the streamwise axis. To realize the high accurate computation, the discretization in space is performed with hybrid scheme in which sine or cosine series and 6th order compact scheme are used. From view of instantaneous vortex structures, it is found that the flow pattern considerably changes according to the rotating frequency, i.e., according to the increasing the frequency, helical and entangled mode appear in turn. From the ensemble averaged flow properties, it is confirmed that the jet widely spreads perpendicular to the rotating axis. Further in order to quantify the mixing efficiency of the dynamic control, as the mixing measure, a statistical entropy is examined. Compared to the uncontrolled jet, the mixing efficiency is markedly improved, thus it turns out that the dynamic control can be expected to be useful for the improvement of mixing performance.
