Water jet flow simulation and lithium free surface flow experiments for the IFMIF target

A water jet experiment was performed to investigate the influences of nozzle inner wall roughness on the free surface stability of water flow, which simulates the lithium (Li) target jet flow of the International Fusion Materials Irradiation Facility (IFMIF). The effect of a cover gas was investigated further as a possible candidate for the interfacial wave growth because of the Kelvin-Helmholtz instability. The results showed that the jet interfacial roughness was insensitive to the cover gas pressure, but it increased with the wall roughness because of the development of a boundary layer along the wall. This effect was found to be significant when the velocity was higher than 10 m/s. Utilizing these results, a Li open flow experiment is being planned by modifying the Li Loop at Osaka University