A multi-field coupling simulation method for rod dropping behavior based on overset mesh

[Background] The time of dropping rod is one of the most important parameters in the design of reactor control rod structure. [Purpose] This study aims to offer a new method for the study of rod dropping behavior. [Methods] A dynamic multi-field coupling simulation method based on overset mesh was proposed by using computational fluid dynamics (CFD) approach. Two-dimensional axisymmetric models of control rod and driving rod are established respectively. The flow field component and background mesh of the control rod and driving rod were changed adaptively according to the rod dropping behavior. The calculated fluid resistance was exchanged between the two flow fields at each time step, and the motion of control rod and driving rod were updated according to the velocity obtained by solving the motion equation, thus establishing the multi-field coupling. [Results] The simulation results show that the method is reliable to cover the typical rod dropping behavior with good generality. [Conclusions] This method achieves a good compromise between calculation time and solution accuracy, hence can be easily extended to 3D model when the computational conditions allow. (author)