Investigation on reverse flow phenomenon in U-tubes under the conditions of ship maneuver

• The reverse flow in U-tubes under the ship maneuver conditions are investigated.
• The effects of swerving, raising and sinking on the reverse flow are analyzed.
• The ship maneuver will significantly change the reverse flow characteristics.
• The effect of lateral motion on the reverse flow is greater than that of upright motion.

For the natural circulation, it is shown that the reverse flow phenomenon may occur in the vertically inverted U-tube steam generators (UTSG), which has some negative influences on the passive safety of nuclear power plant (NPP). However, related researches on the reverse flow in UTSG in marine NPP are relatively few. In present work, the characteristics of single phase reverse flow in the U-tubes under the conditions of ship maneuver are investigated using the computational fluid dynamics (CFD) method. The effects of swerving, raising and sinking of ship on the reverse flow phenomenon in the U-tubes are analyzed. The results show that these movements will significantly change the hydrodynamic characteristics of fluid flow in U-tubes. The acceleration in the portside direction of ship will reduce the possibility of reverse flow, whereas the acceleration in the starboard direction will increase that. On the other hand, the possibility of reverse flow will be decreased or increased when ships accelerate to float up or sink down. The influence of the lateral movement on the reverse flow is greater than that of the upright movement.