The present experimental study investigates the interaction and downstream development of two localized swirling flow structures created using a tangential injection method. A swirl generator is placed at the inlet of a 52.1 mm diameter pipe. The swirl generator consists of two swirl chambers with inner diameters of 23.8 mm. Each swirl chamber has a design swirl number of 7.14. Water is injected into each swirl chamber by two tangential injection ports. The injection ports are tangent to the swirl chamber and perpendicular to the axis of the pipe. The two co-rotating vortices created in the swirl generator interact freely within the pipe downstream of the swirl generator. The objective of the present study is to document the interaction between the two vortices and the downstream development of the flow. Lateral velocity fields are obtained using particle image velocimetry (PIV). Time-averaged lateral velocity fields and tangential velocity profiles are presented for several axial locations downstream of the swirl generator. Reynolds numbers of 11,000 and 17,000 are investigated. Results document the streamwise development and interaction between the two co-rotating vortices created by tangential injection. As the two swirling structures develop in the streamwise direction, three different types of flow patterns are identified. The first consists of two distinct swirling flow structures. Further downstream of the swirl chamber, the two swirling structures merge and form a single swirling flow structure with an elliptic core. In the third flow pattern, the center core of the swirling flow has a circular shape.

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