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Simulation of Fluid forces in Fuel Bundles
Alexander Moksyakov, Osama Elbanhawy, Marwan Hassan

Last modified: 2018-04-21


Vibrations of fuel bundles are major concerns as they can result in fretting wear damage at the interior surface of the pressure tube.  The fretting damage takes place at the locations where the outer fuel elements come in contact with the pressure tube surface.  The fretting wear results from the impact and sliding motion of the fuel elements against the pressure tube surface.  In addition, structural problem in the form endplate cracking can take place due to these vibrations.  One of the fluid forces that can greatly affect the dynamics of the fuel bundles are generated by the motion of the fuel elements in axial flow.  The fluid force acting on any fuel element is assumed to be a linear combination of the fluid forces created by the motion of all surrounding fuel elements.   These forces are expressed in terms of force coefficients representing the influence of these motions and can be decomposed into inertia, stiffness, and damping components.   The numerical model is introduced the represent these forces in a flexible fuel kernel.  The central element was given a period motion and the forces acting on the surrounding elements were obtained.  The obtained force coefficients were used in an analytical framework to predict the fuel bundle vibrations.


Fuel Bundles, CFD, Dynamics

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