Analytical and experimental study of turbulence-induced vibrations in a cantilever-mounted coaxial cylinder

This paper investigates turbulence-induced vibrations in a confined annular flow configuration representative of pressurized water reactor internals. The experimental setup consists of a rigid inner cylinder mounted on two flexible rectangular plates inside a cylindrical vessel. Building on our previous work, analytical expressions for the fluid-elastic forces in quiescent fluid are derived, accounting for added mass, damping, partial immersion, viscous, and confinement effects. Theoretical predictions of the natural frequencies for various filling heights are obtained and systematically validated against experimental measurements. A new nondimensional formulation of the governing equations further yields an analytical expression for the root mean square displacement under turbulent forcing. The root mean square prediction is based on an effective homogeneous turbulence model characterized by a prescribed pressure power spectral density and correlation lengths drawn from the literature. Although dedicated measurements indicate that the turbulence in the present configuration is not strictly homogeneous, introducing a calibrated cut-off reduced frequency in the pressure spectrum yields a consistent and quantitatively accurate description of the root mean square response as a function of reduced velocity.