Applicability analysis of reduced order modeling methods for fluid dynamics in molten salt reactor

Abstract: Background : For high-fidelity simulations of fluid dynamics in molten salt reactor, even though a supercomputer is able to suppress the period of each simulation, the consequent expense is still prohibitively costly. A possible way to overcome this limitation is the use of Reduced Order Modelling (ROM) techniques. Purpose : Evaluating the accuracy of the ROM methods for reconstructing the velocity and pressure fields. Methods :  Two ROM methods based on the Proper Orthogonal Decomposition (POD) with both Galerkin projection, namely FV-ROM (ROM based on Finite Volume approximation ) and SUP-ROM (ROM with supremizer stabilization ), are established for fluid dynamics of molten salt reactor. Then, both methods are tested on the unsteady cases of liquid-fueled molten salt reactor (LFMSR). Results : The FV-ROM demonstrates notable advantages in both velocity prediction and computational efficiency. For laminar and turbulent transient simulations, the average velocity L2 relative errors are less than 0.5% and 0.6%, respectively, with acceleration ratios of approximately 1500 and 1000 times for single time steps. Conversely, the SUP-ROM scheme demonstrates significant prowess in pressure prediction, achieving remarkably low pressure average L2 relative errors of 0.20% and 0.38% for laminar and turbulent transient scenario, respectively. Conclusions : The integration of the SUP-ROM and FV-ROM for fluid dynamics computations of molten salt reactor could significantly enhances computational efficiency and ensure reliability and accuracy of transient simulation.