Investigation of the flow redistribution upstream of grid-like obstacles separated by a variable gap

In nuclear Pressurized Water Reactors, fuel assemblies are slender structures composed of many rods held together by regularly spaced grids. Intense in-core conditions may sometimes result in permanent deformations impairing the reactor normal operation or even challenging its safety. Fluid-structure interactions central plot this multiphysical storyline, and water gaps between adjacent act as main character. More specifically, flow redistribution upstream grids, from gap to rod bundle other way around, affects force which is exerted coolant on Analytical models accounting for effect can be found literature. The present article describes a simple experiment dedicated providing validation data such models. Mock-up grids were 3D printed disposed hydraulic loop with variable distance them. For each configuration, mean axial velocity was probed at hundreds locations inside using an LDA acquisition system. rate then computed several methods compensating lack measures unreachable areas. This experimental campaign helped gain insight into behavior across assembly. Notably, near proportionality demonstrated width through it. It also observed that cross-flows take place very limited region