A multiscale numerical algorithm for heat transfer simulation between multidimensional CFD and monodimensional system codes

Abstract

Abstract. Nowadays the rapidly-increasing computational power allows scientists and engineers to perform numerical simulations of complex systems that can involve many scales and several different physical phenomena. In order to perform such simulations, two main strategies can be adopted: one may develop a new numerical code where all the physical phenomena of interest are modelled or one may couple existing validated codes. With the latter option, the creation of a huge and complex numerical code is avoided but efficient methods for data exchange are required since the performance of the simulation is highly influenced by its coupling techniques. In this work we propose a new algorithm that can be used for volume and/or boundary coupling purposes for both multiscale and multiphysics numerical simulations. The proposed algorithm is used for a multiscale simulation involving several CFD domains and monodimensional loops. We adopt the overlapping domain strategy, so the entire flow domain is simulated with the system code. We correct the system code solution by matching averaged inlet and outlet fields located at the boundaries of the CFD domains that overlap parts of the monodimensional loop. In particular we correct pressure losses and enthalpy values with source-sink terms that are imposed in the system code equations. The 1D-CFD coupling is a defective one since the CFD code requires point-wise values on the coupling interfaces and the system code provides only averaged quantities. In particular we impose, as inlet boundary conditions for the CFD domains, the mass flux and the mean enthalpy that are calculated by the system code. With this method the mass balance is preserved at every time step of the simulation. The coupling between consecutive CFD domains is not a defective one since with the proposed algorithm we can interpolate the field solutions on the boundary interfaces. We use the MED data structure as the base structure where all the field operations are performed, allowing the algorithm to be used with all the numerical codes where a MED duplicate of the field solution can be created. The MEDmem libraries come with the Salome platform and include basic methods for handling meshes and fields. We provide results that show the consistency of the proposed algorithm.

FEMuS-Platform: a numerical platform for multiscale and multiphysics code coupling

“…The coupling between a system code and the FEMuS finite element library has been presented in past works, and the interested reader can consult [11,12]. In particular, the FEMuS library has been coupled with the system code CATHARE to have multiscale simulations of complex systems.…”

“…In most of them, the CFD code uses the system code variables as inlet values. To have a two-way coupling, the average value of the solution at the outlet of the CFD code's domain is used either as an imposed value in the system code (decomposed domain technique), or to calculate a fictitious source term to be imposed in the system domain to make the system code solution equal to the CFD one (overlapping domain technique, see [11]). Thus, we implemented a function able to build a MED interface on a desired portion of the domain, containing all the solution fields on it.…”

Simulation of TALL-3D experimental facility with a multiscale and multiphysics computational platform

“…This paper summarizes the results obtained from the joint collaboration between ENEA and UNIBO, showing the consistency of the developed algorithm for multi-scale simulations, with the intent to provide a suitable tool for studying issues of LFR technology. The coupling between FEMuS-OpenFOAM CFD codes and CATHARE system code is based on an overlapping domain method [5,6,7]. In the first part, the main attention is put on CFD analysis of the test section where further boundary conditions are tested to achieve more accurate simulation results.…”