Plastic Mechanism Analysis of Structural Performance of Web Girders During Ship Collision and Grounding

2014 ◽  
Author(s):  
Zhenguo Gao ◽  
Zhiqiang Hu
Keyword(s):  
Numerical Simulation ◽  
Deformation Process ◽  
Large Scale ◽  
Theoretical Models ◽  
Small Scale ◽  
Deformation Model ◽  
Mechanism Analysis ◽  
Plastic Mechanism ◽  
Ship Collision ◽  
The Web

The behavior of web girders is of crucial importance during ship collision and grounding accidents. A new theoretical deformation model for ship web girders subjected to in-plane localized force is proposed in this paper. It is based on a summary of the existing theoretical models and progressive deformation process of the web girder in the numerical simulation, which is a reproduction of a previous experiment. From the analysis of the deformation process of the web girder in the numerical simulation it is found that there are some important features which have not been considered by any of the existing models. Based on these new features, plastic analytical method is employed, and special emphasis is placed on the folding mechanism establishing and major energy dissipation pattern identifying. Thus, a new theoretical deformation model is proposed. The proposed model is verified by two previous experiments, one is small-scale and the other is large-scale. From the force-indentation curves in comparisons, it can be found that the results of the proposed method compare well with those of the experiments. Therefore, the proposed method can be a useful part in the quick and reliable assessment of the performance of the ship structures in the accidental collision and grounding events.

Mapping global water projects: improving access to donor investment information on the web

Water Policy ◽  
2003 ◽  
Vol 5 (3) ◽  
pp. 203-212
Author(s):  
J. Lisa Jorgensona
Keyword(s):  
Water Resources ◽  
Web Sites ◽  
Large Scale ◽  
Technical Assistance ◽  
Water Withdrawal ◽  
Small Scale ◽  
Water Projects ◽  
Essential Information ◽  
Water Project ◽  
The Web

This paper discusses a series of discusses how web sites now report international water project information, and maps the combined donor investment in more than 6000 water projects, active since 1995. The maps show donor investment:  • has addressed water scarcity,  • has improved access to improvised water resources,  • correlates with growth in GDP,  • appears to show a correlation with growth in net private capital flow,  • does NOT appear to correlate with growth in GNI. Evaluation indicates problems in the combined water project portfolios for major donor organizations: •difficulties in grouping projects over differing Sector classifications, food security, or agriculture/irrigation is the most difficult.  • inability to map donor projects at the country or river basin level because 60% of the donor projects include no location data (town, province, watershed) in the title or abstracts available on the web sites.  • no means to identify donor projects with utilization of water resources from training or technical assistance.  • no information of the source of water (river, aquifer, rainwater catchment).  • an identifiable quantity of water (withdrawal amounts, or increased water efficiency) is not provided.  • differentiation between large scale verses small scale projects. Recommendation: Major donors need to look at how the web harvests and combines their information, and look at ways to agree on a standard template for project titles to include more essential information. The Japanese (JICA) and the Asian Development Bank provide good models.

scholarly journals Anisotropic Characteristics of Turbulence Dissipation in Swirling Flow: A Direct Numerical Simulation Study

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Xingtuan Yang ◽  
Nan Gui ◽  
Gongnan Xie ◽  
Jie Yan ◽  
Jiyuan Tu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Energy Dissipation ◽  
Direct Numerical Simulation ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Turbulent Energy ◽  
Swirling Flows ◽  
Small Scale

This study investigates the anisotropic characteristics of turbulent energy dissipation rate in a rotating jet flow via direct numerical simulation. The turbulent energy dissipation tensor, including its eigenvalues in the swirling flows with different rotating velocities, is analyzed to investigate the anisotropic characteristics of turbulence and dissipation. In addition, the probability density function of the eigenvalues of turbulence dissipation tensor is presented. The isotropic subrange of PDF always exists in swirling flows relevant to small-scale vortex structure. Thus, with remarkable large-scale vortex breakdown, the isotropic subrange of PDF is reduced in strongly swirling flows, and anisotropic energy dissipation is proven to exist in the core region of the vortex breakdown. More specifically, strong anisotropic turbulence dissipation occurs concentratively in the vortex breakdown region, whereas nearly isotropic turbulence dissipation occurs dispersively in the peripheral region of the strong swirling flows.

Scaling Effect on Dynamic Impact Response of Structures in Fluid Fields

2013 ◽  
Author(s):  
Zhongheng Guo ◽  
Lingyu Sun ◽  
Taikun Wang ◽  
Junmin Du ◽  
Han Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Dimensional Analysis ◽  
Large Scale ◽  
Scaling Laws ◽  
Scaling Law ◽  
Fluid Pressure ◽  
Structural Safety ◽  
Scale Model ◽  
Small Scale ◽  
Water Tank

At the conceptual design phase of a large-scale underwater structure, a small-scale model in a water tank is often used for the experimental verification of kinematic principles and structural safety. However, a general scaling law for structure-fluid interaction (FSI) problems has not been established. In the present paper, the scaling laws for three typical FSI problems under the water, rigid body moves at a given kinematic equation or is driven by time-dependent fluids with given initial condition, as well as elastic-plastic body moves and then deforms subject to underwater impact loads, are investigated, respectively. First, the power laws for these three types of FSI problems were derived by dimensional analysis method. Then, the laws for the first two types were verified by numerical simulation. In addition, a multipurpose small-scale water sink test device was developed for numerical model updating. For the third type of problem, the dimensional analysis is no longer suitable due to its limitation on identifying the fluid pressure and structural stress, a simulation-based procedure for dynamics evaluation of large-scale structure was provided. The results show that, for some complex FSI problems, if small-scale prototype is tested safely, it doesn’t mean the full-scale product is also safe if both their pressure and stress are the main concerns, it needs further demonstration, at least by numerical simulation.

scholarly journals A study of the flow-field evolution and mixing in a planar turbulent jet using direct numerical simulation

2002 ◽  
Vol 450 ◽  
pp. 377-407 ◽  
Author(s):  
S. A. STANLEY ◽  
S. SARKAR ◽  
J. P. MELLADO
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Direct Numerical Simulation ◽  
Large Scale ◽  
Computational Study ◽  
Practical Interest ◽  
Small Scale ◽  
Mixing Process ◽  
Mean Velocity ◽  
Small Scales

Turbulent plane jets are prototypical free shear flows of practical interest in propulsion, combustion and environmental flows. While considerable experimental research has been performed on planar jets, very few computational studies exist. To the authors' knowledge, this is the first computational study of spatially evolving three-dimensional planar turbulent jets utilizing direct numerical simulation. Jet growth rates as well as the mean velocity, mean scalar and Reynolds stress profiles compare well with experimental data. Coherency spectra, vorticity visualization and autospectra are obtained to identify inferred structures. The development of the initial shear layer instability, as well as the evolution into the jet column mode downstream is captured well.The large- and small-scale anisotropies in the jet are discussed in detail. It is shown that, while the large scales in the flow field adjust slowly to variations in the local mean velocity gradients, the small scales adjust rapidly. Near the centreline of the jet, the small scales of turbulence are more isotropic. The mixing process is studied through analysis of the probability density functions of a passive scalar. Immediately after the rollup of vortical structures in the shear layers, the mixing process is dominated by large-scale engulfing of fluid. However, small-scale mixing dominates further downstream in the turbulent core of the self-similar region of the jet and a change from non-marching to marching PDFs is observed. Near the jet edges, the effects of large-scale engulfing of coflow fluid continue to influence the PDFs and non-marching type behaviour is observed.

scholarly journals A Study on Comparison of Network Location Efficiency of Web Application Firewall

2018 ◽  
Vol 7 (3.33) ◽  
pp. 183
Author(s):  
Sung-Ho Cho ◽  
Sung-Uk Choi ◽  
. .
Keyword(s):  
Web Services ◽  
Web Application ◽  
Large Scale ◽  
Service Providers ◽  
Web Security ◽  
Small Scale ◽  
Internet Service ◽  
Large Scale Networks ◽  
The Web ◽  
Line Type

This paper proposes a method to optimize the performance of web application firewalls according to their positions in large scale networks. Since ports for web services are always open and vulnerable in security, the introduction of web application firewalls is essential. Methods to configure web application firewalls in existing networks are largely divided into two types. There is an in-line type where a web application firewall is located between the network and the web server to be protected. This is mostly used in small scale single networks and is vulnerable to the physical obstruction of web application firewalls. The port redirection type configured with the help of peripheral network equipment such as routers or L4 switches can maintain web services even when physical obstruction of the web application firewall occurs and is suitable for large scale networks where several web services are mixed. In this study, port redirection type web application firewalls were configured in large-scale networks and there was a problem in that the performance of routers was degraded due to the IP-based VLAN when a policy was set for the ports on the routers for web security. In order to solve this problem, only those agencies and enterprises that provide web services of networks were separated and in-line type web application firewalls were configured for them. Internet service providers (ISPs) or central line-concentration agencies can apply the foregoing to configure systems for web security for unit small enterprises or small scale agencies at low costs.  

scholarly journals Evolution of Large and Small Scale Magnetic Fields in the Sun

1991 ◽  
Vol 130 ◽  
pp. 218-222
Author(s):  
Peter A. Fox ◽  
Michael L. Theobald ◽  
Sabatino Sofia
Keyword(s):  
Numerical Simulation ◽  
Magnetic Fields ◽  
Time Dependence ◽  
Large Scale ◽  
Sunspot Cycle ◽  
Small Scale ◽  
The Sun ◽  
Solar Magnetic Fields ◽  
Magnetic Resistivity ◽  
Statistical Evolution

AbstractThis paper will discuss issues relating to the detailed numerical simulation of solar magnetic fields, those on the small scale which are directly observable on the surface, and those on larger scales whose properties must be deduced indirectly from phenomena such as the sunspot cycle. Results of simulations using the ADISM technique will be presented to demonstrate the importance of the treatment of Alfvén waves, the boundary conditions, and the statistical evolution of small scale convection with magnetic fields. To study the large scale fields and their time dependence, the magnetic resistivity plays an important role; its use will be discussed in the paper.

The influence of atmospheric waves on the general circulation of the middle atmosphere

1987 ◽  
Vol 323 (1575) ◽  
pp. 693-705 ◽  
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Middle Atmosphere ◽  
Chemical Species ◽  
Theoretical Models ◽  
Irreversible Processes ◽  
Small Scale ◽  
Wind Fields ◽  
Meridional Transport ◽  
Radiative Balance

To a first approximation, the basic features of the globally averaged structure of the middle atmosphere (such as the warm stratopause and cold mesopause) can be understood on radiative grounds alone. However, dynamical processes must be invoked if the observed latitudinally varying structures of the zonal-mean temperature and wind fields are to be explained. Particularly large departures from a hypothetical radiatively determined state occur in the winter stratosphere (especially in the Northern Hemisphere) and in the upper mesosphere at the solstices. Simple theoretical models indicate that the primary dynamical mechanisms that drive the middle atmosphere away from radiative balance are wave motions, notably large-scale planetary waves and small-scale gravity waves. Much current research is being devoted to understanding the complex transient and irreversible processes by which such waves can influence the zonal-mean state and also lead to the meridional transport of chemical species.

scholarly journals Influence of Restraint Conditions on Welding Residual Stresses in H-Type Cracking Test Specimens

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2700 ◽  
Author(s):  
Jiamin Sun ◽  
Jonas Hensel ◽  
Thomas Nitschke-Pagel ◽  
Klaus Dilger
Keyword(s):  
Numerical Simulation ◽  
Tensile Stress ◽  
Residual Stresses ◽  
Experimental Method ◽  
Large Scale ◽  
Small Scale ◽  
Welded Structures ◽  
The Real ◽  
Restrained Cracking ◽  
Welding Processes

From the viewpoint of mechanics, weld cracking tends to occur if the induced tensile stress surpasses a certain value for the particular materials and the welding processes. Welding residual stresses (WRS) can be profoundly affected by the restraint conditions of the welded structures. For estimating the tendency of weld cracking, the small-scale H-type slit joints have been widely used for cracking tests. However, it is still hard to decide whether the real large-scale component can also be welded without cracking even though the tested weld cracking specimens on the laboratory scale can be welded without cracking. In this study, the intensity of restraint which quantitatively indicates how much a joint is restrained is used. The influence of restraint condition (intensity of restraint) on WRS is systematically investigated using both the numerical simulation and the experimental method. The achievement obtained in the current work is very beneficial to design effective H-type self-restrained cracking test specimens for evaluating the sensitivity of the material and the welding procedures for weld cracking in the real large-scale components.

Experimental Demonstrations and Optimal Design Conditions of Snow-Melting System Using Geothermal and Solar Energy

2009 ◽  
Author(s):  
Niro Nagai ◽  
Shigenobu Miyamoto ◽  
Toru Tsuda ◽  
Shinya Yamahata
Keyword(s):  
Numerical Simulation ◽  
Temperature Field ◽  
Optimal Design ◽  
Solar Energy ◽  
Surface Area ◽  
System Performance ◽  
Large Scale ◽  
Road Surface ◽  
Small Scale ◽  
Snow Melting

The authors have been proposed and developed snow-melting system using geothermal and solar energy. In summer, solar heat is stored into underground from road surface to underground piles. In winter, the underground heat is utilized to melt snow on the road surface. This system was applied to parking lots and bridges of relatively small scale (less than 1000 m2). Numerical simulation program was also developed to predict temperature field of the system and to evaluate system performance. This program was verified by experimental data only for relatively small scale test area. In addition, appropriate design conditions, such as pile diameter, length and number, can not be easily estimated when road surface area and ability (average heat flux) of snow-melting are given. This paper aims to demonstrate the system for relatively large scale (larger than 1000 m2), and to obtain optimal design conditions of the system at given road surface area and ability. The snow-melting system using geothermal and solar energy was applied to a parking lot and a bridge of large scale. Both sites were under practical use which means cars were sometimes parked and run over the bridge. Obtained experimental data of temperature field of the system and snow melting situation show that numerical simulation program predicted system performance and temperature field adequately even though the program contains several simplifications. To discuss the optimal design conditions, numerical simulation was conducted by changing the following parameters: diameter, length, number and pitch of piles, pitch and diameter of heat dissipation pipe, flow rate of circulating water, road surface area. All these parameters are considered to affect system performance. The simulation results revealed that pile surface area determined by diameter, length and number of piles is the dominant parameter for deciding snow-melting ability. Namely, when road surface and snow-melting ability are given, necessary pile surface area can be obtained from the simulation results, and system design of piles becomes possible with considering cost for embedding piles.

scholarly journals <i>Letter to the Editor</i>: First direct observations of the reduced striations at pump frequencies close to the electron gyroharmonics

1999 ◽  
Vol 17 (9) ◽  
pp. 1235-1238 ◽  
Author(s):  
F. Honary ◽  
T. R. Robinson ◽  
D. M. Wright ◽  
A. J. Stocker ◽  
M. T. Rietveld ◽  
...  
Keyword(s):  
Large Scale ◽  
Electromagnetic Emission ◽  
Theoretical Models ◽  
Small Scale ◽  
Radio Waves ◽  
Radio Science ◽  
Ionospheric Physics ◽  
F Region ◽  
Direct Observations ◽  
Electron Gyrofrequency

Abstract. It is well known that the ionospheric plasma response to high-power HF radio waves changes drastically as the heater frequency approaches harmonics of the electron gyrofrequency. These include changes in the spectrum of the stimulated electromagnetic emission, reduction in the anomalous absorption of low-power diagnostic waves propagating through the heated volume, and reduction in the large scale F-region heating. Theoretical models as well as previous experimental evidence point towards the absence of small-scale field-aligned plasma density irregularities at pump frequencies close to electron gyroharmonics as the main cause of these changes. Results presented in this paper are the first direct observations of the reduced striations at the 3rd gyroharmonic made by the CUTLASS radar. In addition, simultaneous EISCAT observations have revealed that the "enhanced ion-line" usually present in the EISCAT ion-line spectrum during the first few seconds after heater switch on, persisted at varying strengths while the heater was transmitting at frequencies close to the 3rd electron gyroharmonics.Key words. Ionosphere (active experiments; ionospheric irregularities) · Radio science (ionospheric physics)

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