The deformation and dynamics of a flexible plate with attached mass blocks mounted behind a circular cylinder

This paper presents a wind tunnel experiment on the deformation and dynamics of a flexible plate with attached mass blocks mounted behind a circular cylinder. The mass blocks are fixed at a distance of 3/4 of the plate length from the rear stagnation point of the cylinder. Different flexible plates with lengths ranging from 1D to 7D and thicknesses equaling 0.5%D and 1%D (where D is the cylinder diameter) are tested and compared. It is found that as the plate length increases, the deformation behavior of the flexible plate can be classified into three sequential regimes — “linear-shaped”, “fish-shaped”, and “trumpet-shaped” — with the Strouhal number decreasing gradually. The deformation regime changes at a longer plate length for the thicker flexible plate (1%D) than for the thinner one (0.5%D). Proper orthogonal decomposition (POD) analysis reveals that the deformation of the flexible plate is mainly dominated by the first two POD modes, and that the “fish-shaped” and “trumpet-shaped” regimes are characterized by the bending mode and deflection mode, respectively. Additionally, in the “trumpet-shaped” regime, the flexible plates have higher maximum and mean elastic strain energies. A kinematic analysis of the characteristic points on the flexible plate shows that the movement of the plate's free end lags behind that of the mass blocks, and its phase lag decreases as the plate length increases. In particular, the fluctuating drag of the experimental model shows a step change when the deformation regime changes.