Generalized hydrodynamic coefficients of twin connected circular cylinders in finite water depth

In this work the generalized hydrodynamic coefficients of connected twin circular cylinders are studied. Firstly, a matched boundary element method with eigen-function expansion is applied to study the generalized hydro-dynamic coefficients of floating and submerged tunnels with twin horizontal cylinders in finite water depth. By numerical examination it is found that gap resonance problem can be neglected for the submerged floating tunnels with a certain submergence depth, and the axial wave number play an important role for the added mass. Then, analytic solutions are derived for the high frequency approximations of the generalized added masses of twin connected cylinders by the eigenfunction expansion in the polar coordinate system with aid of their images about the x-axis in the infinite fluid domain. The high frequency approximations of generalized added masses decrease with increasing vibration wave number. When T/a and B/a are larger than 3 (where T is the cylinder submergence, B is the spacing distance between the twin cylinders and a is the radius of the cross-section of the cylinder), the hydrodynamic interference between the two cylinders can be neglected and the generalized added mass coefficients of connected twin cylinders can be derived from these of single isolated cylinders.

Automated summary

This work investigates the generalized hydrodynamic coefficients of connected twin circular cylinders. The study applies a matched boundary element method with eigen-function expansion to analyze the hydrodynamic coefficients of floating and submerged tunnels with twin horizontal cylinders in finite water depth. The study finds that the gap resonance problem can be ignored for submerged floating tunnels with a certain submergence depth, and the axial wave number plays a crucial role in the added mass. Analytic solutions are then derived for the high frequency approximations of the generalized added masses of twin connected cylinders. The hydrodynamic interference between the two cylinders can be neglected when certain conditions are met, allowing for the derivation of generalized added mass coefficients from those of single isolated cylinders.