Evaluation of the influence of the viscous sublayer on the mechanical stability of fuel plates under axial flow conditions

Abstract

The current work aims to investigate the influence of the viscous sublayer on the mechanical stability of fuel element plates under axial flow conditions by means of two-way Fluid Structure Interaction (FSI) numerical simulations. The methodology adopted is that proposed by (Mantec´on, 2019; Mantec´on and Mattar Neto, 2018), who observed a transition from linear to non-linear behavior between the maximum deflection of the plates in their leading edge with the square of the velocity of the cooling fluid in the channel. The speed at which the transition is identified is the critical speed (Vc). In order to verify the influence of the viscous effects, the CFD domain was discretized from its viscous sublayer. As this approach greatly increases the computational cost, where the characteristics of the flow allowed, symmetry boundary conditions were used. In addition to this approach, it was decided to investigate the ability to solve the FSI problem in steady state. The obtained results confirmed that the boundary layer modeling is sufficient to determine the critical velocity. Furthermore, they also suggest that the steady-state approach and the application of symmetry boundary conditions, where possible, can be used in the design of new fuel elements, supporting traditional methods.