Numerical analysis of self-induced free surface flow oscillation by fluid dynamics computer code splash-ale

SPLASH-ALE is a three-dimensional finite-element fluid-dynamics computer code employing Arbitrary Lagrangian Eulerian (ALE) method. Because the ALE method enables computational nodes lo move in arbitrary velocity, this code can deal with moving boundaries such as free surface. In a reactor vessel of liquid metal cooled Fast Breeder Reactor (FBR), there is such situation that upward coolant flow impinges on its free surface and makes swell of the surface. In a experiment of simplified flow geometry of such situation, an upward plane jet impinging on free surface oscillates without any external force. In this study, the oscillation was numerically analyzed by the SPLASH-ALE code. The numerical results corresponded well with experimental those, e.g. streakline of the oscillating jet. It was confirmed that the SPLASH-ALE code is capable to analyze unstable phenomena caused by interaction between flow and free surface, and the numerical result is available to solve the mechanism of the oscillation.