Abstract
Water hammer occasionally occurs in the piping systems of power plants and always leads to tube rupture or component failure,by which normal operation will be interrupted, or just makes loud noise. The thesis emphasizes on the investigations of “numerical simulation of water hammer in single-phase and two-phase flow”, expected to describe precisely the process that the pressure wave propagates and the interaction with system boundaries. According to flow condition, water hammer (one-dimensional analysis) is divide into two parts (single and two-phase flow). Depending on their physical characteristics, we establish arithmetic models and choose the suitable numerical method to write single-tow phase water hammer analysis programs. For single-phase water hammer, we use the conventional numerical method: method of characteristics (MOC) and construct the arithmetic models of piping components. Besides, we discuss the numerical discrepancy with RELAP5, usually used as heat-flow analysis business program in plants. From benchmark cases, we know the MOC method can precisely describe the pressure wave propagation process. But RELPA5 using first order upwind scheme might make the amplification of pressure wave grew weaker because of the numerical diffusion. About two-phase water hammer, we focus on homogeneous bubbly flow. The governing equations for describing such type flows are a set of nonlinear partial different equation and wave speed depends on pressure. Because the MOC method can’t deal with the shock pressure problem, so we choose two numerical difference methods (MacCormack and Gabutti scheme). In order to analyze results and explain, we will discuss the numerical characteristics of those schemes, example of stability、convergence condition. From benchmark cases, we know that the numerical methods can simulate two-phase water hammer effectively. Water hammer in a pipeline results in column separation when the pressure drops to the vapor pressure of liquid. The situation will lead to pipeline divided into many subvolume with different flow chart, not homogeneous bubbly flow. For analysis transient events, we must combine water hammer and column separation effects. Due to this, it is proposed that the article can be fundamental in future to precisely analyze water hammer effect for all flow charts.