Fluid–structure interaction on concentric composite cylinders containing fluids in the annulus

Dynamic response of two concentric horizontal composite cylinders containing water in the annulus was investigated under impact loading so as to examine the load transfer from the outer cylinder to the inner through a fluid medium. Different water filling levels in the annulus were considered along with different magnitudes of impact loading. Both of the composite cylinders were 254 mm long, had a diameter of 76.2 mm and 88.9 mm, respectively, and were assembled concentrically. Both experimental and numerical studies were conducted to supplement each other. The experimental set-up was designed and constructed. Both cylinders were constrained at both ends, and the water level was varied in the annulus of the two cylinders. The experimental set-up used strain gages at certain locations. For each experiment, the strain data were collected and examined. Then, the fast Fourier transform was applied to the strain data to identify major vibrational frequencies and to examine the effect of the added mass. The numerical study provided additional results which were not measured by the experiment, such as the fluid pressure in the annulus and the dynamic motion of the cylinders. The fluid–structure interaction resulted in significant coupling of the outer and inner composite cylinders.