WAVE RESPONSE ANALYSIS FOR HUGE FLOATING STRUCTURES : 1st Report : Dynamic interaction for fluid and elastic beam

As the output power of wind turbine increasingly gets larger, the structural flexibility of elastic bodies, such as rotor blades and tower, gets more significant owing to larger structural size. In that case, the dynamic interaction between these flexible bodies become more profound and may significantly impact the dynamic response of the whole wind turbine. In this study, the integrated model of a 5-MW wind turbine is developed based on the finite element simulations so as to carry out dynamic response analysis under random wind load, in terms of both time history and frequency spectrum, considering the interactions between the flexible bodies. And, the load evolution along its transmitting route and mechanical energy distribution during the dynamic response are examined. And, the influence of the stiffness and motion of the supporting tower on the integrated system is discussed. The basic dynamic characteristics and responses of 3 models, i.e. the integrated wind turbine model, a simplified turbine model (blades, hub and nacelle are simplified as lumped masses) and a rigid supported blade, are examined, and their results are compared in both time and frequency domains. Based on our numerical simulations, the dynamic coupling mechanism are explained in terms of the load transmission and energy consumption. It is found that the dynamic interaction between flexible bodies is profound for wind turbine with large structural size, e.g. the load and displacement of the tower top gets around 15% larger mainly due to the elastic deformation and dynamic behaviors (called inertial-elastic effect here) of the flexible blade; On the other hand, the elastic deformation may additionally consume around 10% energy (called energy-consuming effect) coming from external wind load and consequently decreases the displacement of the tower. In other words, there is a competition between the energy-consuming effect and inertial-elastic effect of the flexible blade on the overall dynamic response of the wind turbine. And similarly, the displacement of the blade gets up to 20% larger because the elastic-dynamic behaviors of the tower principally provides a elastic and moving support which can significantly change the natural mode shape of the integrated wind turbine and decrease the natural frequency of the rotor blade.

Download Full-text

A Study on Wave Response and Evaluation of Habitability of Floating Restaurant

Volume 6: Nick Newman Symposium on Marine Hydrodynamics; Yoshida and Maeda Special Symposium on Ocean Space Utilization; Special Symposium on Offshore Renewable Energy ◽

10.1115/omae2008-57364 ◽

2008 ◽

Cited By ~ 1

Author(s):

Hiroaki Eto ◽

Osamu Saijo ◽

Koichi Maruyoshi

Keyword(s):

Size Structure ◽

Boundary Integral ◽

Frame Structure ◽

Medium Size ◽

Response Analysis ◽

Structural System ◽

Floating Structure ◽

Structural Dynamic ◽

Floating Base ◽

Wave Response

Since Japan is limited in area, the effective ocean space development is very important and urgent subject. Concerning a research and development of effective ocean space utilization, the MEGA-FLOAT was one of the most famous projects in Japan that had the purpose of a floating airport construction, and the numerous R & D were conducted aiming at actual construction and those results were reported in respect of conceptual design, construction method, fluid analysis, structural dynamic analysis, environment issue etc. However, the end was faced without achieving it, it can be said that the effect is large. After the end of that project, the realistic, small or medium size structure began to be paid to attention. As the good example of such a kind floating structure, floating pier and disaster prevention base having an advantage against an earthquake, floating restaurant etc. were constructed shown in Figure 1. In this paper, assuming the small size floating restaurant, the wave response analysis was studied, and the habitability of that structure was evaluated from the response calculation results. Concretely, the floating base part; barge type of the restaurant building was designed by the Class NK (Rules and Guidance for the survey and construction of steel ships, Part Q Steel barges). The calculation model consists of a three-story building and the base, that floating artificial base supporting the building was assumed by the elastic plate structural system, and also that building was of the frame structure system. In order to structural analysis, the restaurant model of two different structural systems was united into one body system. In this paper, it is called the hybrid structural system. Fluid effect was analyzed as the fluid-structural interaction problem. Concretely, the Boundary Integral Equation Method (BIEM) was used here, and the wave response calculation was demonstrated by that forces. The evaluation of habitability of the restaurant in vertical and horizontal motion was examined by the diagram proposed from our research results.

Download Full-text

Dynamic analysis of a shape memory alloy beam with pseudoelastic behavior

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x17754268 ◽

2018 ◽

Vol 29 (9) ◽

pp. 1835-1849 ◽

Cited By ~ 5

Author(s):

Reza Razavilar ◽

Alireza Fathi ◽

Morteza Dardel ◽

Jamal Arghavani Hadi

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Frequency Response ◽

Kinetic Equations ◽

Elastic Beam ◽

Beam Theory ◽

Response Analysis ◽

Interesting Phenomenon ◽

Time Saving ◽

Solution Approach

This article aims at developing a semi-analytic approach for studying the free and forced vibrations of a pseudoelastically behaving shape memory alloy beam. Based on the Euler–Bernoulli beam theory, equations of motion were derived through Hamilton principle, and the obtained partial differential equations were decomposed by applying the Galerkin approach and were solved using Newmark integration method. A three-dimensional phenomenological model of shape memory alloy, which is capable of identifying the main properties of the shape memory alloy, was employed to model the behavior of the shape memory alloy beam. A closed-form numerical algorithm was introduced to simulate the governing kinetic equations of the shape memory alloy beam coupled with transformation strain. The presented novel solution approach is simple, flexible, and time-saving. Stability analysis was performed using phase state trajectories to show dynamic characteristics of the shape memory alloy beam. Due to hysteric behavior of the shape memory alloy, energy dissipation was clearly observed in early stages of the free vibration and within the transient regions of the forced vibration. The numerical results showed that, due to the hysteric induced damping effect, the vibration amplitude is smaller in comparison to an equivalent elastic beam, and consequently, the shape memory alloy beam exhibits more stable behavior at the resonant frequencies. This property can potentially find applications in energy damping applications and vibration control. Moreover, an interesting phenomenon called jumping was observed in the results of frequency response analysis. At jumping frequency, the amplitude of the frequency response has two distinct levels. This jumping frequency is as a result of the hysteresis behavior of the shape memory alloy, and it is a function of the exciting amplitude.

Download Full-text

Dynamic Response of SPAR in Internal Solitary Waves

Volume 1: Offshore Technology; Polar and Arctic Sciences and Technology ◽

10.1115/omae2011-49413 ◽

2011 ◽

Author(s):

Yan Qu ◽

Zhijun Song ◽

Bin Teng ◽

Yunxiang You

Keyword(s):

Dynamic Response ◽

Solitary Waves ◽

Mkdv Equation ◽

Internal Solitary Waves ◽

Response Analysis ◽

Potential Hazard ◽

Current Profile ◽

Floating Structures ◽

Dynamic Motion ◽

De Vries

Internal solitary wave is considered as a potential hazard environmental condition to the floating structures in South China Sea. This paper presents results of the dynamic response analysis of a SPAR in internal solitary waves (ISW). Mathematical model of the ISW is selected to simulate the current process induced by the ISW. The result shows that the Korteweg–de Vries (KdV) gives rational result compared with the Modified Korteweg–de Vries (MKdV) equation. Dynamic motion of SPAR were estimated by using the current profile derived from KDV theory, load determined by Morrison equation and the nonlinear model of the mooring system.

Download Full-text

Wave Response of a Semisubmersible Floating Structure Model With Mechanical Connectors

Volume 6: Nick Newman Symposium on Marine Hydrodynamics; Yoshida and Maeda Special Symposium on Ocean Space Utilization; Special Symposium on Offshore Renewable Energy ◽

10.1115/omae2008-57339 ◽

2008 ◽

Author(s):

Yoshiyasu Watanabe ◽

Koichiro Yoshida

Keyword(s):

Numerical Analysis ◽

Response Analysis ◽

Structure Model ◽

Analysis Program ◽

Floating Structure ◽

Response Characteristics ◽

Wave Response ◽

New Type ◽

Hydroelastic Response ◽

Two Bodies

It is desired instead of welding to develop a mechanical connector, which may work well to connect two units at the site in spite of circumstances of some extent of relative motions between two units caused by waves. One of the authors proposed a new type of mechanical connector, which is based on an idea of three bodies problem instead of usual mechanical connectors (two bodies problem). In this paper, wave exciting tests of a semisubmersible floating structure model with the proposed mechanical connectors of 1/100 scale and the numerical analysis using hydroelastic response analysis program VODAC are carried out and wave response characteristics of the semisubmersible floating structure model with the mechanical connectors and its feasibility are reported.

Download Full-text

Wave response analysis of a floating bridge for strait crossing

PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN ◽

10.2208/prooe.14.155 ◽

1998 ◽

Vol 14 ◽

pp. 155-160

Author(s):

Yuichirou Hara ◽

Tomoaki Utsunomiya ◽

Eiichi Watanabe ◽

Shougo Matsunaga ◽

Haruhiko Uetsuka ◽

...

Keyword(s):

Response Analysis ◽

Wave Response ◽

Floating Bridge

Download Full-text

Investigating the Linear and Nonlinear Stationary Wave Response to Anomalous North American Snow Cover

Journal of the Atmospheric Sciences ◽

10.1175/2010jas3581.1 ◽

2011 ◽

Vol 68 (4) ◽

pp. 904-917 ◽

Cited By ~ 3

Author(s):

Stefan Sobolowski ◽

Gavin Gong ◽

Mingfang Ting

Keyword(s):

Snow Cover ◽

North American ◽

Land Surface ◽

Large Scale ◽

Wave Model ◽

Stationary Wave ◽

Response Analysis ◽

Stationary Waves ◽

Continental Scale ◽

Wave Response

Abstract Continental-scale snow cover represents a broad thermal forcing on monthly-to-intraseasonal time scales, with the potential to modify local and remote atmospheric circulation. A previous GCM study reported robust transient-eddy responses to prescribed anomalous North American (NA) snow cover. The same set of experiments also indicated a robust upper-level stationary wave response during spring, but the nature of this response was not investigated until now. Here, the authors diagnose a deep, snow-induced, tropospheric cooling over NA and hypothesize that this may represent a pathway linking snow to the stationary wave response. A nonlinear stationary wave model is shown to reproduce the GCM stationary wave response to snow more accurately than a linear model, and results confirm that diabatic cooling is the primary driver of the stationary wave response. In particular, the total nonlinear effects due to cooling, and its interactions with transient eddies and orography, are shown to be essential for faithful reproduction of the GCM response. The nonlinear model results confirm that direct effects due to transients and orography are modest. However, with interactions between forcings included, the total effects due to these terms make important contributions to the total response. Analysis of observed NA snow cover and stationary waves is qualitatively similar to the patterns generated by the GCM and linear/nonlinear stationary wave models, indicating that the snow-induced signal is not simply a modeling artifact. The diagnosis and description of a snow–stationary wave relationship adds to the understanding of stationary waves and their forcing mechanisms, and this relationship suggests that large-scale changes in the land surface state may exert considerable influence on the atmosphere over hemispheric scales and thereby contribute to climate variability.

Download Full-text