Abstract
Properties of both a turbulent jet injected downward in a rotating fluid and the induced secondary circulation are investigated by means of laboratory experiments and a linear theory. The main results obtained by the laboratory experiments are summarized as follows:
1) The advancing velocity of the lower end of the jet is smaller than that in a static fluid.
2) A remarkable upward motion appears when the injection of the source fluid is stopped.
3) The secondary circulation induced by the jet does not penetrate far below the lower end.
The structure of the induced secondary circulation can be qualitatively explained by the linear theory in which a two-dimensional laminar jet is assumed.
The suppression of the vertical velocities is caused by the upward pressure gradient force which is generated by the entrainment of the rotating ambient fluid and is horizontally balanced with the centrifugal force acting on the swirling fluid particles as was considered by Barcilon (1967b) and Wilkins et al. (1971a). The existence of this pressure gradient force is consistent with 1) and 2). 3) indicates that the depression in the pressure near the nozzle cancels the high pressure near the lower end of the jet due to the divergence field so as to make the pressure perturbation far below the jet vanish.
