A Study on the Water Packing Mitigation Scheme for the Thermohydraulic System Code
China General Nuclear Power Group(CGN)is developing a new thermal hydraulic system analysis code LOCUST 2.0,which uses a two-fluid two-pressure and seven-equation model.As LOCUST 2.0 uses the Euler system to describe the fluid equation,at the boundary of the numerically discrete control volume,the numerical processing method will introduce false violent pressure fluctuations similar to the water hammer phenomenon at the end of the pipe.This phenomenon is generally called water packing or numerical water hammer phenomenon.As the water packing mitigation scheme of the single pressure model is no longer applicable to the dual pressure,a method for suppressing the water packing phenomenon of the system code for the dual pressure model is designed.The method includes identifying the control volume where the water packing phenomenon occurs,and modifying specific terms in the pressure equation of the control volume where the water packing phenomenon occurs,and then resolving the pressure equation.In the process of modifying the pressure equation,an inhibitory factor with the ability to adapt to the pressure fluctuation amplitude is designed.The above method was used in the numerical solution of LOCUST 2.0,and the inlet conditions of saturated and subcooled liquid were tested under different pressures.The results showed that this method achieved the purpose of eliminating the violent fluctuation of pressure,and the effect of the designed suppression factor was better than that of using the suppression factor of two fluid single pressure system code.
Water packingTwo fluid two pressure modelPressure spikeThermal hydraulic system analysis code
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