A compound swirl jet which consists of an annular swirling jet and a coaxial free jet is effective as a push flow of the push-pull ventilator. In this paper, to enhance the mixing capability of the jet flow, the experiment was carried out under the condition of locating the inner tube of free jet to the upstream. The flow rate of the jet flow was examined for various nozzle depth by the measurement of velocity distribution. As a result, it was found that the optimum flow rate of the collection is obtained without the swirling flow, when the nozzle depth increases. The mechanism of the flow was clarified by the flow visualization using the smoke method.
