Mixing of Carbon Dioxide Gas and Air by a Pulsating Jet With a Reversed Flow

We consider pulsating jets as one method for the rapid mixing of two different gases. Pulsed carbon dioxide gas was issued from a round nozzle into still air. The intensity of the pulsation was set at the value which produced an oscillatory reversed flow in the nozzle exit. Spatial and temporal changes of concentration and velocity were investigated in the mixing region. The mixing of the gases is dramatically enhanced near the nozzle exit. Neither the concentration nor the velocity monotonically decays in the streamwise direction, because the ambient air is drawn periodically by the reversed flow. The direction of the velocity changes periodically at the boundary, which is the position where the mean concentration becomes the minimal value. The lump of any concentration is torn off because of the direction change in the velocity. There is also a phase difference between concentration and velocity.