Flow instability in a vertical boiling channel under ocean conditions

Two-phase flow instability is a very common phenomenon in two-phase systems. However, there are a few studies on flow instability characteristics under ocean motions especially the resonance phenomenon induced by combined actions of thermal hydraulic and ocean motions. The flow instability is harmful to the operation of two-phase flow systems. Therefore, more researches are needed for in depth understanding of this phenomenon. In this paper, an ocean condition version thermal-hydraulic system code is briefly introduced. The source term for additional acceleration is added into the momentum equation in a conventional system code. The system code possesses the capability to assess flow instability under ocean conditions. The quantitative analysis of system stability is performed based on stability boundary, phase change number (Npch) line and scale of flow oscillation (SFO). The effects of rolling and heaving motions on flow instability in a vertical boiling channel are analyzed. There is resonance phenomenon which induces oscillations with relatively large amplitude and makes the system more unstable.