Study on gas entrainment evaluation method at free liquid surface; Application study of adaptive mesh refinement method on unsteady wake vortex analysis

Alzahrani, H.*; Matsushita, Kentaro ; Sakai, Takaaki*; Ezure, Toshiki ; Tanaka, Masaaki  

Development of evaluation method for cover gas entrainment (GE) by vortices generated at free surface in upper plenum of sodium-cooled fast reactor (SFR) is required. An evaluation method by predicting vortices from flow velocity distribution obtained by 3D CFD analysis is developed, and Adaptive Mesh Refinement (AMR) method is examined to improve efficiency of CFD analysis is examined. In this study, mesh refinement with two conditions were examined. The first one is to use negative second invariant of velocity gradient tensor, Q, and the second one is to use pressure gradient condition with Q0. As a result of applying AMR method to unsteady vortices system with a flat plate, the mesh near stagnation area around flat plate was refined in the latter condition compared with the former. Transient analyses were performed with refined mesh by AMR method, the result of mesh using the latter condition was closer to the result of all refined mesh with pressure distribution near flat plate.