Visualization experiment of complex flow fields in a triple elbow piping system under swirling inflow conditions

This study evaluated experimentally the effect of influence of the inflow condition upon the flow field in the cold leg piping of the primary cooling system of a sodium-cooled loop-type fast reactor by using a swirling flow generator. Flow visualization with the two-dimensional particle image velocimetry was conducted to reveal the velocity fields of the flow in the piping, especially fluctuating velocity fields, and the results were compared to those obtained from the fully-developed turbulent inflow case. The experiment showed that the there appeared long-period vortices shedding with weak periodicity from the intrados of the 1st elbow instead of steady vortices shedding from flow separation region. In the 2nd elbow, the periodicity of fluctuating velocities were not largely different from those obtained in the fully-developed turbulent inflow case. The downstream of the 2nd elbow was not largely affected by the inflow condition. (author)