Response Mitigation of Floating Platform by Porous-Media-Tuned Liquid Dampers

Abstract

A porous-media-tuned liquid damper (PMTLD) can serve as an effective and economical dynamic vibration absorber. Placing porous media within a water tank can improve the capacity for energy dissipation and optimize the performance by varying its material properties. Two numerical models are adopted for the simulations of the sloshing problem in PMTLD and the dynamics of a floating platform in waves. The first potential-based approach employs a mixed-type boundary value problem (BVP) solver and a free-surface particle tracker. This approach not only simulates the inviscid water wave but also includes the nonlinear damping effects via a quadratic Forchheimer term for the PMTLD. Another equivalent mechanical model is used to reduce the degree of freedom of the PMTLD system. The Newmark method is embedded to solve the rigid-body dynamics. The second viscous approach uses the finite element method (FEM) to spatially discretize the Navier-Stokes (NS) equations and handles the free surface via the volume of fluid (VOF) and the level set (LS) equations. The multiphase simulation is implemented by a computational modeling toolkit Proteus for the fluid phase and Chrono for the solid phase. The correlations between potential flow and two-phase Navier-Stokes models are presented. The PMTLD is designed by analogy with the tuned mass damper (TMD). Numerical results show that the PMTLD can effectively reduce the structure's dynamic response in terms of vibration amplitude around resonance. Such damping devices have great potential for offshore platforms and wind turbine design.

Catenary Mooring Length Control for Motion Mitigation of Semi-Submersible Floating Wind Turbines

“…Besides these indirect load mitigation control designs, more straightforward motion reduction control mechanisms by introducing additional actuations have been proposed, such as a structural control [22][23][24], ballast redistribution control [25], mooring control [26,27], or integration with wave energy converters [28,29]. These methods will allow for control operations even when the turbine is parked, e.g., the extreme wind condition, at the expense of extra equipment cost and energy utilisation if necessary.…”

Experimental and numerical analysis of the influence of fluid-structure interactions on the dynamic characteristics of a flexible tank

“…Liquid sloshing in tanks relies on a multiphase Navier-Stokes model and a potential model. Tsao et al used the open-source toolkits Proteus and Chrono to resolve the fluid domain and implement solid motion [26,27]. Moreover, various wall thicknesses can affect the dynamic characteristics of the liquid tank, possibly leading to an inactive TLD [25].…”