Multi-scale fluid-structure interaction simulations based on mesoscopic approaches

Many challenging fluid-structure interaction problems in nuclear engineering remain unresolved because current CFD methodologies are unable to manage the number of computational cells needed and/or the difficulties associated with meshing changing geometries. One of the most promising recent methodologies for fluid dynamics modeling is the lattice-Boltzmann method-an approach that offers significant advantages over classical CFD methodologies by 1) greatly reducing meshing requirements, 2) offering great scalability, and 3) through relative ease of code parallelization. While LBM often requires increased numerical effort compared to other methods, this can be dramatically reduced by combining LBM with Adaptive Mesh Refinement (LB-AMR). This study describes an ongoing collaboration investigating nuclear fuel-assembly spacer grid performance. The LB-AMR method, used to simulate the flow field around a specific spacer grid design, is capable of describing turbulent flows for high Reynolds numbers, revealing rich flow dynamics in good qualitative agreement with experimental results. Prepared by LLNL under Contract DE-AC52-07NA27344.