Modularfiloating structures(MFS)offer a sustainable pathway towards the expansion of coastal cities in adaptation tofilooding and sea level rise driven by climate change.It is therefore necessary to develop analytical...Modularfiloating structures(MFS)offer a sustainable pathway towards the expansion of coastal cities in adaptation tofilooding and sea level rise driven by climate change.It is therefore necessary to develop analytical methods easily accessible to architects or structural engineers for the rapid prototyping of MFS designs.This work develops novel closed‑form expressions describing the rigid body dynamics of symmetrically loaded rectangular pontoons across all six degrees of freedom(DOF)excited by surface waves approaching from any arbitrary direction.The derivations were based on Airy wave theory assuming frequency‑independent added mass and damping.When benchmarked against numerical solutions from ANSYS/AQWA for two MFS prototypes,the analytical approach proved capable of predicting the response amplitude operators(RAO)across all DOFs,wave directions,and structural confiigurations.However,while the response of mass‑dominated DOFs(surge,sway,and yaw)were well captured,the damping ratio for stiffness‑dominated DOFs(heave,roll,and pitch)must be judiciously selected to yield accurate RAO results.A parametric investigation further elucidated the contribution of structural geometry and wave directionality on the critical accelerations experienced by an idealizedfiloating structure founded upon a square pontoon under realistic sea states.It was discovered that the largest accelerations were triggered by waves approaching orthogonally to the pontoon.Ultimately,this work facilitates a more streamlined approach for the dynamic analysis of compliantfiloating bodies to supplement detailed modeling efforts via numerical methods.展开更多
One of the new methods for powering low-power electronic devices at sea is a wave energy harvesting system. In this method, piezoelectric material is employed to convert the mechanical energy of sea waves into electri...One of the new methods for powering low-power electronic devices at sea is a wave energy harvesting system. In this method, piezoelectric material is employed to convert the mechanical energy of sea waves into electrical energy. The advantage of this method is based on avoiding a battery charging system. Studies have been done on energy harvesting from sea waves, however, considering energy harvesting with random JONSWAP wave theory, then determining the optimum values of energy harvested is new. This paper does that by implementing the JONSWAP wave model, calculating produced power, and realistically showing that output power is decreased in comparison with the more simple Airy wave model. In addition, parameters of the energy harvester system are optimized using a simulated annealing algorithm, yielding increased produced power.展开更多
It has been shown that Boussinesq type equations, which include the lowest order effects of nonlinearity and frequency dispersion, can provide an accurate description of wave evolution in coastal regions. But differen...It has been shown that Boussinesq type equations, which include the lowest order effects of nonlinearity and frequency dispersion, can provide an accurate description of wave evolution in coastal regions. But different linear dispersion characteristics of the equation can be obtained by different integrating method. In this paper, a new form of the Boussinesq equation is derived by use of two different layer horizontal velocity variables instead of the commonly used depth-averaged velocity or an arbitrary layer velocity. This significantly improves the linear dispersion properties of the Boussinesq equation and enables it to be applied to a wider range of water depth.展开更多
This paper presents a potential approach to settle the problem of surviving major safety accidents in Submerged Floating Tunnel （SFT） that detachable emergency escape devices are set up outside SFT. The Computationa...This paper presents a potential approach to settle the problem of surviving major safety accidents in Submerged Floating Tunnel （SFT） that detachable emergency escape devices are set up outside SFT. The Computational Fluid Dynamics （CFD） technology is used to investigate the effect of emergency escape devices on the hydrodynamic load acting on SFT in uniform and oscillatory flows and water waves by numerical test. The governing equations, i.e., the Reynolds-Averaged Navier-Stokes （RANS） equations and k - ε standard turbulence equations, are solved by the Finite Volume Method （FVM）. Analytic solutions for the Airy wave are applied to set boundary conditions to generate water wave. The VOF method is used to trace the free surface. In uniform flow, hydrodynamic loads, applied to SFT with emergency escape device, reduce obviously. But, in oscillatory flow, it has little influence on hydrodynamic loads acting on SFT. Horizontal and vertical wave loads of SFT magnify to some extend due to emergency escape devices so that the influence of emergency escape devices on hydrodynamic loads of SFT should be taken into consideration when designed.展开更多
文摘Modularfiloating structures(MFS)offer a sustainable pathway towards the expansion of coastal cities in adaptation tofilooding and sea level rise driven by climate change.It is therefore necessary to develop analytical methods easily accessible to architects or structural engineers for the rapid prototyping of MFS designs.This work develops novel closed‑form expressions describing the rigid body dynamics of symmetrically loaded rectangular pontoons across all six degrees of freedom(DOF)excited by surface waves approaching from any arbitrary direction.The derivations were based on Airy wave theory assuming frequency‑independent added mass and damping.When benchmarked against numerical solutions from ANSYS/AQWA for two MFS prototypes,the analytical approach proved capable of predicting the response amplitude operators(RAO)across all DOFs,wave directions,and structural confiigurations.However,while the response of mass‑dominated DOFs(surge,sway,and yaw)were well captured,the damping ratio for stiffness‑dominated DOFs(heave,roll,and pitch)must be judiciously selected to yield accurate RAO results.A parametric investigation further elucidated the contribution of structural geometry and wave directionality on the critical accelerations experienced by an idealizedfiloating structure founded upon a square pontoon under realistic sea states.It was discovered that the largest accelerations were triggered by waves approaching orthogonally to the pontoon.Ultimately,this work facilitates a more streamlined approach for the dynamic analysis of compliantfiloating bodies to supplement detailed modeling efforts via numerical methods.
文摘One of the new methods for powering low-power electronic devices at sea is a wave energy harvesting system. In this method, piezoelectric material is employed to convert the mechanical energy of sea waves into electrical energy. The advantage of this method is based on avoiding a battery charging system. Studies have been done on energy harvesting from sea waves, however, considering energy harvesting with random JONSWAP wave theory, then determining the optimum values of energy harvested is new. This paper does that by implementing the JONSWAP wave model, calculating produced power, and realistically showing that output power is decreased in comparison with the more simple Airy wave model. In addition, parameters of the energy harvester system are optimized using a simulated annealing algorithm, yielding increased produced power.
文摘It has been shown that Boussinesq type equations, which include the lowest order effects of nonlinearity and frequency dispersion, can provide an accurate description of wave evolution in coastal regions. But different linear dispersion characteristics of the equation can be obtained by different integrating method. In this paper, a new form of the Boussinesq equation is derived by use of two different layer horizontal velocity variables instead of the commonly used depth-averaged velocity or an arbitrary layer velocity. This significantly improves the linear dispersion properties of the Boussinesq equation and enables it to be applied to a wider range of water depth.
基金the China Postdoctoral Science Foundation (Grant Nos. 201003274, 20090460636)the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20090111120016)
文摘This paper presents a potential approach to settle the problem of surviving major safety accidents in Submerged Floating Tunnel （SFT） that detachable emergency escape devices are set up outside SFT. The Computational Fluid Dynamics （CFD） technology is used to investigate the effect of emergency escape devices on the hydrodynamic load acting on SFT in uniform and oscillatory flows and water waves by numerical test. The governing equations, i.e., the Reynolds-Averaged Navier-Stokes （RANS） equations and k - ε standard turbulence equations, are solved by the Finite Volume Method （FVM）. Analytic solutions for the Airy wave are applied to set boundary conditions to generate water wave. The VOF method is used to trace the free surface. In uniform flow, hydrodynamic loads, applied to SFT with emergency escape device, reduce obviously. But, in oscillatory flow, it has little influence on hydrodynamic loads acting on SFT. Horizontal and vertical wave loads of SFT magnify to some extend due to emergency escape devices so that the influence of emergency escape devices on hydrodynamic loads of SFT should be taken into consideration when designed.
