Modeling Fuel Assemblies on Large Shake Tables

摘要

Non-intrusive optical measurement techniques have been adapted to gamer high spatial and temporal data of fluid structure interaction (FSI) on an earthquake shake table, which is a particularly challenging environment. A single flexible cylinder in a concentric cylinder exposed to turbulent axial flow with external seismic forcing is a simplified geometry of a nuclear fuel rod contained in a fuel bundle. This geometry allows for development of experimental diagnostics such as particle image velocimetry (PIV) and shadowgraphy at high magnifications - on the order of unity; this requires mounting optical equipment on the shake table to obtain fluid and structural dynamics in the non-inertial reference frame. Additionally, the laser beam is delivered to the shake table with carefully designed high-power optical fibers and the cameras deployed here have long recording times at 2 kHz. This unusual diagnostics leads to capture of multi-temporal scale phenomena that is indicative of earthquakes. Three cases are studied herein, (1) static test on laboratory floor, (2) static test on shake table while table is activated, (3) shake table test with external forcing applied. The fluctuating velocity at the center of the flow in the axial direction at the center of the flow, and associated spectra, are analyzed for the three cases to guarantee that unwanted vibrations have been minimized, and to characterize the effect of external forcing on the fluid velocity.