In this study, the effects of the surge radiation force are investigated by a floating cylinder in two-layer fluid over a bottom-mounted cylinder. The proposed device consists of a floating cylinder in the upper layer and another a coaxial bottom cylinder in the lower layer of a two-layer fluid system of finite depth having the infinite horizontal extent. The radiation problem is taken into consideration under the framework of linear water wave and the entire fluid domain is divided into two regions, say, an exterior and interior regions. The analytical solutions for the surge radiation potential to the boundary-value problems in the respective regions are obtained by utilizing the method of separation of variables. By making use of the matched eigenfunction expansion method, the unknown coefficients that arise in the radiation potentials are evaluated. With the help of the expressions of the surge radiated potential, the corresponding radiation forces are obtained as a linear combination of added mass and damping coefficient. A bunch of numeric outcomes of added mass and damping coefficient are investigated for a distinct set of parameters of the device, i.e., the effect of the variation in frequencies with the radii of the cylinders, drafts of the floating cylinder, and the density ratio between the fluid layers on the surge radiated force are presented and their significant results are discussed. The 3D free surface and interface elevations due to the effect of surge radiated waves are presented in both surface- and internal-wave modes. The oscillations in added mass and damping coefficients are observed with variations of the parameters of the device.

在本研究中，通过底部安装圆柱体上的两层流体中的浮动圆柱体来研究浪涌辐射力的影响。该装置由上层的一个浮动圆柱体和下层的另一个同轴底部圆柱体组成，具有无限水平范围的有限深度的两层流体系统。在线性水波的框架下考虑辐射问题，将整个流体域分为两个区域，即外部区域和内部区域。利用变量分离的方法，得到了各区域浪涌辐射势边值问题的解析解。通过利用匹配特征函数展开方法，可以评估辐射势中出现的未知系数。借助浪涌辐射电势的表达式，可以得到相应的辐射力，作为附加质量和阻尼系数的线性组合。针对设备的一组不同参数，研究了一系列附加质量和阻尼系数的数值结果，即频率随圆柱半径、浮动圆柱的吃水深度以及之间的密度比的变化的影响。介绍了流体层对浪涌辐射力的影响，并讨论了它们的重要结果。由于浪涌辐射波的影响而产生的 3D 自由表面和界面高程以表面波和内波模式呈现。随着装置参数的变化，观察到附加质量和阻尼系数的振荡。