Parallel Computing Research For Core Thermal Hydraulic Based On Subchannel Model

At present,the sub channel model is mainly used for the fine thermal hydraulic analysis of the reactor,but the biggest problem of this model is the uncertainty interaction between channels.Coolant interaction between sub channels has some basic forms,namely,lateral flow,flow scattering,flow swept and turbulent mixing,which has been the major and most concerned issues of sub channel analysis.In view of the development of computer technology and computational fluid dynamics(CFD),CFD technology has been applied rapidly in the field of core thermal hydraulic analysis.In recent years,the research of numerical simulation for the flow field and temperature field of the sub channels is increasing.However,the limitation of the computational power makes it only be carried out in a limited area,according to it,in this paper,CFD technology is applied to analyze the mixing effects of coolant between the rods and the flow characteristics of coolant through the rod bundles,and then a theory foundation is provided for core thermal hydraulic analysis based on subchannel model.Taking two adjacent sub channels as the research object,periodic boundary conditions applied,the influence of geometrical structure on the interaction between sub channels in the fuel assembly with grid spaces is researched based on FLUENT.By analyzing mixed effects in sub channels caused by geometrical structure in the fuel assembly after results verified by experimental dates,then a formula of lateral mixing flow effect is carried out through quantitatively analyzing calculation results,which lays a theoretical foundation of sub channel model for core thermal hydraulic analysis.By considering the lateral mixing characteristics of the sub channels,the sub channel simulation code of the core thermal hydraulic is developed by coupling mass,axial momentum and energy conservation equations.Then taking the core of Qinshan II nuclear power plant as the research object,influences of different channel partitioning method on thermal hydraulic calculation of core are studied.And then based on primary system of Qinshan phase one,a system simulation code based on the sub channel model of reactor core is established,and the steady-state and transient analysis are carried out to verify the accuracy and applicability of the proposed model.The results of the code are in accord with simulation requirements,which shows that the code can be applied to high precision simulation of core thermal hydraulic.Last but not least,due to the complexity of the core structure,the precise modeling and fast simulation cannot both be achieved.Therefore,parallel computing is one of the most effective methods at present.So in this paper,it's discussed how to use message passing mode to develop parallel programming,based on MPI and high speed interconnection network,the cluster system was built,and then the parallel computing platform for reactor core thermal hydraulic was studied.The platform is mainly used to support the parallel computing of core thermal hydraulic,so as to achieve high accuracy and rapid solution for the reactor core simulation model.And then by running thermal hydraulic calculation on the parallel platform,it can be known that parallel computing can effectively improve the calculation speed of thermal hydraulic code.