Study on Added Mass and Fluid Damping Characteristics Based on Concentric Cylindrical Structure

To deeply investigate the intrinsic characteristics of added mass and fluid damping, analyze the impact of viscosity and amplitude on them, and provide guidance for analyzing fluid-induced vibration, this study takes a concentric cylinder as an example to establish a prediction method of added mass and fluid damping based on computational fluid dynamics (CFD). The user-defined function (UDF) is used to set the motion equation of the inner circle, and the overset grid technology is used to complete the grid motion, so as to realize the numerical simulation of the flow field. The shape of the function is determined according to Bearman's hypothesis, and the calculated fluid force curve is fitted by the least square method to obtain the added mass and fluid damping. Finally, the influences of viscosity and dimensionless amplitude on results are compared. The calculation and analysis results show that the viscosity not only affects the fluid damping but also the added mass. The dimensionless amplitude has little effect on the added mass and an obvious effect on the fluid damping. Pressure damping and viscous damping increase in equal proportion with the increase of dimensionless amplitude, and the proportion of pressure damping increases with the decrease of diameter ratio. The solution of the modified formula with dimensionless amplitude effect is in good agreement with the numerical results. The research in this paper has an important guiding role in optimizing the existing analysis methods of flow-induced vibration.