Fluid Resonance Between Twin Floating Barges with Roll Motion Under Wave Action

The wave-induced fluid resonance between twin side-by-side rectangular barges coupled with the roll motion of the twin barges is investigated by both numerical simulation and physical model test.A 2D numerical wave flume,based on an open source computational fluid dynamics(CFD)package OpenFOAM,is applied for the numerical simulation.After numerical validations and convergent verifications,the characteristics of the fluid resonance in the gap between the twin rolling side-by-side barges are examined.The resonant frequency of the oscillating fluid in the gap between the twin rolling barges decreases compared with that between the twin fixed barges.Generally,the twin barges roll in the opposite directions,and their equilibrium positions lean oppositely with respect to the initial vertical direction.A physical model test is carried out for a further investigation,in which the twin barges are set oppositely leaning and fixed.From the present experimental results,a linear decrease of the resonant frequency with the increasing leaning angle is found.Combined with the numerical results,the deflection of the equilibrium positions of the twin barges is a relevant factor for the resonant frequency.Besides,the effects of the gap width and incident wave height on the fluid resonance coupled with roll motion are examined.

Theoretical and numerical investigations of wave resonance between two floating bodies in close proximity

A simple theoretical dynamic model with a linearized damping coefficient is proposed for the gap resonance problem, as often referred to as the piston mode wave motion in a narrow gap formed by floating bodies. The relationship among the resonant response amplitude and frequency, the reflection and transmission coefficients, the gap width, and the damping coefficient is obtained. A quantitative link between the damping coefficient of the theoretical dynamic model（ε） and that devised for the modified potential flow model（μ_p） is established, namely, μ_p=3πεω_n/8 （where ω_n is the natural frequency）. This link clarifies the physical meaning of the damping term introduced into the modified potential flow model. A new explicit approach to determine the damping coefficient for the modified potential model is proposed, without resorting to numerically tuning the damping coefficient by trial and error tests. The effects of the body breadth ratio on the characteristics of the gap resonance are numerically investigated by using both the modified potential flow model and the viscous RNG turbulent model. It is found that the body breadth ratio has a significant nonlinear influence on the resonant wave amplitude and the resonant frequency. With the modified potential flow model with the explicit damping coefficient, reasonable predictions are made in good agreement with the numerical solutions of the viscous fluid model.