8,054 research outputs found
Dialogical Skirmishes
No full textTan was guest editor for 'And Now China?', a special print edition of the Ctrl+P journal, which critically responded to the celebratory rhetoric’s of ‘China Now’ and other celebratory markers of China's global ascent in 2008. As well as the introductory article 'Dialogical Skirmishes', Tan also interviewed Hans Ulrich Obrist
The natural vibration characteristics of a water-shell tank interaction system
No full textThe simulation of liquid – tank interactions is important for LNG-tank designs and safe operations. This paper presents some research results developed by authors. Integrated systems studied are formulated using a generalised fluid-structure interaction theory. Various suitable boundary conditions applied to the system are considered, which describes free surface disturbances, dynamical couplings on wet interfaces as well as prescribed pressures caused by explosion waves. The mixed FE substructure – subdomain method and the corresponding computer code adopting the solid displacement and the fluid pressure as variables are described. A water-shell tank interaction system and a 2-dimensional section of a LNG-tank system are numerically simulated using the developed code. The natural frequencies and modes of these two systems are presented. To reveal the filled air influence on the natural vibration characteristics, a case of air-water-shell interaction is investigated. The numerical results are compared with the available numerical and experimental results to demonstrate and validate the method and the computer code. Some guidelines are provided for dynamic designs of liquid-container systems involving fluid-solid interactions
The dynamic analysis of a building structure - acoustic volume interaction system excited by human footfall impacts
No full textA numerical model is developed using a mixed finite element method to simulate building structure – acoustic volume interaction systems excited by human walking impacts. The pressure in the air volume and the displacement in the structure are chosen as fundamental variables to describe structure – air interaction dynamics. The governing equations and corresponding variational formulation are presented. Based on available experimental results on the footfall load history, an approximate load function is proposed to simulate the measured dynamic footfall load as a moving load with a walking speed and dynamically applied to each foot contact point. A simple example is presented to illustrate the method which reveals the mechanism of low-frequency vibration produced by human walking impacts using an air-structure interaction method. The benefits of the proposed method are summarized to provide a guideline using the method to practical house designs
Transient dynamic responses of an internal liquid-LNG tank-sea water interaction system excited by waves and earthquake loads
No full textSloshing problems in partially filled large LNG carriers are of increasing concern because sloshing loads may endanger LNG carriers in operations. Currently, most investigations on sloshing problems mainly focus on the analysis of liquids in rigid tanks which omitted fluid-structure interactions. Based on a mixed displacement–pressure finite element method developed, the authors recently investigated the natural vibration of an internal liquid–elastic structure–external water interaction system. The simulation demonstrated the significance of the interactions between internal liquid sloshing modes and floating modes of LNG tanks on the external sea water. This paper further studies the dynamic responses of this integrated system subject to sea waves and earthquake excitations. The sea wave loads are modelled by pressure waves with different frequencies applied to a boundary of the external water domain and the ground motion data recorded from El-Centro earthquake is used as an earthquake load to the system. The numerical analysis on the dynamic responses of this coupled system further confirms the necessity to consider fluid-structure interactions for safe LNG ship designs
Developments of a mixed finite element substructure–subdomain method for fluid–structure interaction dynamiProccs with applications in maritime engineering
No full textTheoretical developments of mixed finite element substructure-subdomain method for dynamic analysis of fluid-structure interaction systems (FSIS) with applications in maritime engineering are summarised in this paper. Governing equations for FSIS are presented. Boundary conditions for air-liquid interfaces are formulated to account for mass density discontinuity of different fluids. Frequency shift technique is demonstrated for FSIS, which establishes a basis for the design of an algorithm for the purpose of dynamic analysis of structure, fluids and their interactions. A flow chart of the computer program is provided to better illustrate the implementation of numerical method. Four problems in maritime engineering are simulated using the developed Fluid-Structure Interaction Analysis Program-FSIAP. Problem 1 investigates the sloshing frequencies of a liquid tank and its dynamic responses to a sinusoidal base motion and El Centro earthquake excitation, respectively. Problem 2 analyses the transient response of a liquefied natural gas (LNG) tank-water system to an explosion wave in the water. Problem 3 studies a structure-acoustic-volume system subject to human footfall impacts, which may explain the “character” of the footstep noise claimed by people, such as “thuds”, “thumps” and “booming”. Problem 4 investigates the dynamic response of an onshore LNG storage tank subject to an impact load. The numerical results are analysed to provide the guidelines for designs of maritime products involving FSIS
Evidence for erbium-erbium energy migration in erbium(III) bis(perfluoro-p-tolyl)phosphinate
No full textCopyright 2008 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Applied Physics Letters 92, 103303 (2008) and may be found at
Application developments of mixed finite element method for fluid-structure interaction analysis in maritime engineering
No full textThe application developments of a mixed finite element method for transient dynamic analysis of fluid-structure interaction systems (FSIS) in maritime engineering are summarised in this paper. Following the mathematical equations governing generalised FSIS, three problems involving maritime engineering, developed in Marstruct Project, are presented to illustrate the applications of the developed numerical method. Problem 1 investigates the sloshing frequencies of a liquid storage tank and its dynamic response excited by the El Centro earthquake data. Problem 2 analyses the dynamic response of a LNG tank-water interaction system subject to an explosion pressure wave on a water boundary. Problem 3 considers the dynamic response of a structure-acoustic volume interaction system subject to human footfall impacts, which may be used to simulate ship deck vibration caused by human footfall loads to obtain a comfortable living environment of passengers. The numerical results are discussed and analysed to provide the related guidelines for the designs of maritime products involving fluid-structure interactions
An experimental study on vibration characteristics of a thin spherical tank–water interaction system
No full textAn experimental study on the dynamic behavior of a thin spherical tank–water interaction system is reported. The water–tank interaction system is horizontally fixed on a vibration table with equally spaced tabs on the outer shell and excited by vertical harmonic table motions.
Several cases of chosen water levels were tested to investigate the variation of the system. The effect of free surface boundary is considered by opening the top hole of the tank, allowing the air inside the tank directly connecting into the air outside. While a plug closes the hole of the tank, the air inside the tank cannot go out which is considered as cases with no free surface effect. The experimental results obtained show the variations of the natural frequencies and modes of the water–tank interaction system affected by the water levels and free surface, which provides a guideline of the liquid spherical tank design
A numerical investigation of natural characteristics of a partially filled tank using a substructure method
No full textSloshing of liquid in a partially filled tank has been a concern in a number of engineering fields, including automobile, aerospace and marine industries. This paper reports the findings of a numerical investigation into the variations of natural frequencies and mode shapes of a tank-liquid system. The effects of a few parameters of the system, such as the liquid filling level, geometry shape and wall stiffness of the tank, etc. on the natural vibrations, especially natural frequencies, are examined. Both spherical and rectangular tanks are studied.
Fluid-structure interaction systems are described by a generalized linear fluid-structure interaction theory of which the structure is governed by the theory of linear elasticity and the fluid by a wave equation as well as various suitable boundary conditions, such free surface wave disturbance and kinematic and dynamic coupling conditions on the fluid-solid interfaces. Numerical simulations are based on a mixed finite element substructure – subdomain method and the corresponding computer code which adopts the displacement of solid and the pressure in the fluid as variables to model the coupling system.
A spherical liquid container and a 2D cross section of LNG tank are simulated using the developed method. The results are compared with the available theoretical, reported numerical and experimental results to demonstrate the applications of the method. Some guidelines obtained by this investigation are presented which may be a reference for dynamic designs of liquid-container system considering fluid-solid interactions
Vibration problem of a spherical tank containing jet propellant: numerical simulations
No full textThis document is the final report on the joint research project on vibration problem of a spherical tank containing jet propellant between IHI, Japan and SES, University of Southampton, UK. The background of the project is described. The fundamental principles and numerical method used in numerical simulations are presented. The detailed FEA models for each studied cases are given. The calculation results are presented using tables, curves, figures as well as the attached data files. The available experiment results are listed to compare with the numerical calculations. The calculation results show a fundamental agreement with the experiment results. The numerical analysis confirms that:1)Due to water – tank interaction, the natural frequencies of the water – tank system are decreased with the water level increase. For the 25% water level, the natural frequencies, especially heave mode frequency, shows a significant decrease compared with the empty case. However, with continuing increase the filed water more than 25% level, the decrease gradient of the natural frequencies gradually tends to zero. In the 100% water case, the natural frequency of heave mode is about 200 Hz which can not equal zero.2)Considering free surface wave effect produces a lot of sloshing modes of very low frequencies compared with the natural frequencies of the dry tank structure. Therefore, for dynamic response analysis with high frequency excitations, the free surface wave may be neglected. However, to assess loads caused by sloshing modes, the free surface waves have to be considered.3)There exist relative big deformations at the four tank support places in several vibration modes, which may produce a large local stress at support places to cause the product fail in vibration environment. A strengthen local design at the support places is needed.4)The dynamic response results are affected by damping coefficients of all modes used in the dynamic response analysis. The damping coefficients are approximately presented and therefore, the numerical results are good reference for practical designs.The report confirms that the original purpose of this joint research project has well completed by IHI and SES
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