Numerical Simulation On Fluidstructure-fluid Interaction Of Nuclear Steam Generator Heat Transfer Tube Using OpenFOAM

The nuclear power steam generator is one of the key equipments of the nuclear power plant,connecting the primary and secondary circuits of the generator set.Therefore,its safety is directly related to the operational safety of the nuclear power plant.Heat transfer tubes in steam generators often generate high-frequency vibrations,so-called flow-induced vibration(FIV),due to the action of high-temperature and high-pressure fluid flow.Long-lasting vibrations can cause fretting wear and even cracking of tubes.Flow induced vibration is one of the typical fluid-structure interaction(FSI)phenomena.Therefore,it is very necessary to carry out researches on the phenomenon of flow-induced vibration of tubes of nuclear power steam generator.At present,many domestic and foreign scholars have done a lot of experimental and theoretical research on fluid-structure interaction of nuclear power steam generator heat transfer tubes,and have really achieved a lot,but the research in this area still lack of numerical simulation.Most domestic and foreign studies mainly consider the influence of external fluid of tubes and the internal fluid is simplified as a added mass.It is quite rare that the analysis of fluid-structure interaction phenomena in heat transfer tubes combines internal and external fluids,and the vast majority computational fluid dynamics software cannot directly solve such problems using a existing solver.In fact,tubes for nuclear power are largely affected by the complex internal flow field,in addition to the complex effects of the external fluid.This study combined the basic theories of computational fluid dynamics and fluidstructure interaction algorithms,researching the fluid-induced vibration problem on nuclear steam generator heat transfer tube.The main details are as follows:This study summarized the process to implement the discrete the computational domain and fluid-structure interaction using open source fluid calculation software OpenFOAM which is based on the finite volume method.Modifying the existing fluid-structure interaction solver made it possible to solve the fluid-structure interaction problem of the two-fluid single solid once in a time,namely the fluid-structure-fluid interaction(FSFI).In addition,the fluid-solid coupling solver was verified by the standard case,and the case of heat transfer tube in cross flow is used to verify the reliability of the developed fluidstructure-fluid interaction solver.This study also comprehensively studied the vibration characteristics of the tube of nuclear power steam generator under different outflow velocity,wall thickness,support plate spacing and location of reference point based on the dual fluid single solid interaction solver,combined with the influence of internal and external fluids,which provides a theoretical basis for the design and safe operation of nuclear power steam generator.The results show that there is no significant change in the vibration characteristics of the heat transfer tube at the different outside flow rates;As the wall thickness increases,the natural frequency and vibration frequency also increases,but the amplitude decreases;The amplitude at the position away from the support plate is obviously greater than the amplitude at the support plates.