抄録
This report describes experimental results obtained for a potential core of free jets with variable densities. The potential core oscillates periodically by forming and shedding a vortex ring in the shear layer. A sinusoidal velocity fluctuation in the potential core synchronizes with the radial pulsation of the potential core. The frequency of the pulsation depends on both the Reynolds number and the density of the discharging gas. The time-averaged configuration of the potential core differs from a single, circular cone, and is similar in form to a cone placed on a truncated cone. The length of the potential core depends on the density of the discharging gas and becomes shorter as the density of the jet becomes lower. In addition, the length of the potential core is in proportion to the 1/2 power of the density ratio defined by the densities of the issuing and surrounding gases.
