Development of a coupling between a system thermal-hydraulic code and a reduced order CFD model

TL;DR

This paper introduces a reduced order model (ROM) to replace CFD solvers in nuclear system simulations, significantly reducing computational costs while maintaining accuracy in coupled thermal-hydraulic analyses.

Contribution

It develops a novel coupling method between a system code and a ROM of CFD, demonstrating improved efficiency and comparable accuracy in nuclear pipe flow simulations.

Findings

Coupled RELAP5/ROM models are 3-5 times faster than RELAP5/CFD.

ROM coupled models closely match CFD results in open and closed pipe flows.

The approach accurately predicts new parameter sets with reduced computational effort.

Abstract

The nuclear community has coupled several three-dimensional Computational Fluid Dynamics (CFD) solvers with one-dimensional system thermal-hydraulic (STH) codes. This work proposes to replace the CFD solver by a reduced order model (ROM) to reduce the computational cost. The system code RELAP5-MOD3.3 and a ROM of the finite volume CFD solver OpenFOAM are coupled by a partitioned domain decomposition coupling algorithm using an implicit coupling scheme. The velocity transported over a coupling boundary interface is imposed in the ROM using a penalty method. The coupled models are evaluated on open and closed pipe flow configurations. The results of the coupled simulations with the ROM are close to those with the CFD solver. Also for new parameter sets, the coupled RELAP5/ROM models are capable of predicting the coupled RELAP5/CFD results with good accuracy. Finally, coupling with the ROM is 3-5 times faster than coupling with the CFD solver.