Preliminary numerical study of single bubble dynamics in swirl fl ow using volume of fluid method

Spacer grid with mixing vane had been widely used in nuclear reactor core. One of the main feather ofspacer grid with mixing vane was that strong swirl flow was formed after the spacer grid. The swirl flownot only changed the bubble generation in the near wall field, but also affected the bubble behaviors inthe center region of the subchannel. The interaction between bubble and the swirl flow was one of thebasic phenomena for the two phase flow modeling in fuel assembly. To obatin better understanding onthe bubble behaviors in swirl flow, full three dimension numerical simulations were conducted in thepresent paper. The swirl flow was assumed in the cylindral calculation domain. The bubble interface wascaptured by Volume Of Fluid (VOF) method. The properties of saturated water and steam at differentpressure were applied in the simulation. The bubble trajectory, motion, shape and force were obtainedbased on the bubble parameters captured by VOF. The simulation cases in the present study includedsingle bubble with different size, at different angular velocity conditions and at different pressure conditions. The results indicated that bubble migrated to the center in swirl flow with spiral motion type. The lateral migration was mainly related to shear stress magnitude and bubble size. The bubble movedtoward the center with high velocity when the swirl magnitude was high. The largest bubble had thehighest lateral migration velocity in the present study range. The effect of pressure was small whenbubble size was the same. The prelimenery simulation result would be beneficial for better understandingcomplex two phase flow phenomena in fuel assembly with spacer grid KCI Citation Count: 0