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1.
Katsuya Tanifuji Tsukasa Sato Roger Goodall 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2003,39(4):309-327
Summary This paper deals with a basic study on the actively steered rail vehicle with two-axle bogie trucks, which employs a control law based on the self-steering ability of wheelset. However, this control law not only helps the steering performance, but also tends to lower the running stability. Two methods are proposed to improve the stability. The first method is to add a feedback of wheelset lateral velocity, the second one is to give some time lag to the control force, and both are proved to be affective. Here, the latter is more practical method and the delay of control due to the time lag does not deteriorate the steering performance. 相似文献
2.
Structural pipe-in-pipe cross sections have significant potential for application in offshore oil and gas production systems
because they combine thermal insulation performance with structural strength and self weight in an integrated way. Such cross
sections comprise inner and outer thin-walled pipes with the annulus between them fully filled by a selectable filler material
to impart an appropriate combination of properties. Structural pipe-in-pipe cross sections can exhibit several different collapse
mechanisms, and the basis of the preferential occurrence of one over the others is of interest. This article presents an exact
analysis for predicting the elastic buckling behaviours of a structural pipe-in-pipe cross section when subjected to external
hydrostatic pressure. Simplified approximations are also investigated for elastic buckling pressure and mode when the outer
pipe and its contact with the filler material is considered as a pipe on an elastic foundation. Results are presented to show
the variation of elastic buckling pressure with the relative elastic modulus of the filler and pipe materials, the filler
thickness, and the thicknesses of the inner and outer pipes. Case studies based on realistic application scenarios are used
to show that the simplified approximations are sufficiently accurate for practical structural design purposes. 相似文献
3.
A free-fall microstructure profiler (TurboMAP) reveals highly intermittent features in the fluorescence field. Conventional CTDs that mount a fluorometer are usually deployed with a tethered cable, and the data are averaged or smoothed over a given time or water depth. Because of the nature of the operation and the data processing involved, intermittent features of fluorescence fields are masked. We have developed a statistical technique to extrapolate the intermittency using a lognormal mixture probability density function (mixture pdf). The statistics obtained from the mixture pdf are consistent with microstructure data, thus the conventional CTD can provide statistics appropriate to a micro-scale fluorescence field. 相似文献
4.
A series of elastoplastic large deflection FEM analyses has been performed on hatch covers of bulk carriers subjected to lateral load. Two types of hatch covers are considered which are the folding type and the side-sliding type. For the folding-type cover, one size is considered which is for Handy size bulk carrier, whilst for the side-sliding-type cover, two sizes are considered which are for Panamax and Cape size bulk carriers. For each type, two hatch covers are selected which are designed in accordance with the old ICLL rule and new IACS rule, respectively. Calculated collapse strengths are compared with individual design loads, and a strength assessment is performed. On the basis of collapse behaviour observed in FEM analyses, a simple method is proposed to evaluate the collapse strength of a hatch cover subjected to lateral load. It is confirmed that the collapse strength is accurately predicted by the proposed method. 相似文献
5.
CFD simulation of 3-dimensional motion of a ship in waves: application to an advancing ship in regular heading waves 总被引:1,自引:0,他引:1
A new computational fluid dynamics simulation method has been developed for the unsteady motion of a ship advancing in waves.
The objective is to evaluate the added resistance and predict the performance of a ship in waves. In this study, a finite
volume method, in the framework of a boundary-fitted grid system, is employed. The motion of the ship is solved with six degrees
of freedom by using the hydrodynamic forces and moments obtained from the solution of the simulation method. The marker–density–function
method is employed to calculate the nonlinear free surface. This method is applied to the coupled motion problem of heaving
and pitching.
Received for publication on Nov. 15, 1999; accepted on Nov. 18, 1999 相似文献
6.
In order to investigate the biological impacts of the ocean sequestration of CO2 (carbon dioxide), the dilution processes of CO2 were investigated near injection points in the deep ocean. From a combined fluid-dynamics, chemical, and biological approach,
a two-phase computational fluid dynamics (CFD) method with mass transfer was developed to predict droplet plume flow, the
dissolution of CO2 from droplets into seawater, and the advection–diffusion of dissolved CO2 (DCO2) in the deep ocean. Changes in pH due to the concentration of DCO2 were also calculated. In addition, the isomortality concept of Auerbach et al. was incorporated to predict the lethal damage
to marine organisms caused by DCO2. The simulation results suggested that the biological impacts of CO2 sequestration were insignificant in terms of mortality in both small-scale field experiments and the real-life cases we propose.
Received: October 3, 2001 / Accepted: December 14, 2001 相似文献
7.
Pop-Paul Ewphun Chau Tan Vo Prathan Srichai Chinda Charoenphonphanich Susumu Sato Hidenori Kosaka 《International Journal of Automotive Technology》2017,18(4):643-652
This paper investigates the effects of Hydrotreated vegetable oil-diesel blend to combustion characteristics under various ambient oxygen concentrations and ambient pressure. Combustion characteristics were investigated using heat release rate analysis, two color method, soot concentration measurement and NOx concentration measurement. The experiments were carried out on a rapid compression expansion machine to simulate the ambient condition of a CI engine at TDC. Synthetic gas with oxygen concentrations of 21 %, 15 % and 10 % were used to simulate EGR conditions. A single hole injector was used with five different fuels: commercial diesel, HVO-commercial diesel blends and HVO. The results showed that increasing HVO blending percentages decreased ignition delay, flame temperature, soot concentration and NOx concentration. Heat release at oxygen concentration of 10 % dramatically dropped due to a shortened ignition delay, which resulted in less combustion. A decreased oxygen concentration from applied EGR conditions not only increased ignition delay, heat release, flame temperature and NOx concentration, but also increased soot concentration. A combination of EGR and supercharged conditions by increasing ambient pressure and decreasing oxygen concentrations resulted in increased heat release, decreased flame temperature, ignition delay and soot concentration, compared to EGR conditions. 相似文献
8.
Plumes of air and carbon-dioxide (CO2) bubbles in stratified water were studied experimentally and numerically. It is important to understand the plume behavior
of droplets or bubbles in the ocean in marine environmental engineering. In sequestration of CO2 in the ocean, liquid CO2 is injected in the form of droplets, and thermal stratification in enclosed seas is possibly destroyed by a bubble generator.
This study focuses on the relationship between intrusion depth and stratification intensity, gas flow rate, and bubble size.
A desktop-sized tank was used to achieve no-background-flow conditions for salt stratification. The results from the air-bubble
experiments indicated that the larger the bubble size, the smaller the intrusion depth. We also observed the behavior of CO2 bubbles. They are different from air in that they dissolve in water and are reduced in volume. Our numerical simulation method
for two-phase flow was validated by comparisons with the experiments.
Received: August 13, 2001 / Accepted: October 9, 2001 相似文献
9.
法国、德国、意大利等国的高速铁路迅猛发展,成为引领世界高速铁路的主力,并且,欧洲高速铁路已进入商业运行速度(320 km/h)的新时代。文章介绍了法国、德国、意大利、西班牙等国家高速铁路列车所采用的新技术、新装备、新工艺及发展前景。 相似文献
10.
Numerical tests of various subgrid-scale (SGS) models were conducted for turbulence in thermally stratified homogeneous-shear
flow at a relatively low Reynolds number. Compared with a direct numerical simulation (DNS), we found that nondynamic isotropic
SGS models are not able to represent the energy spectrum very well because the energy decays considerably during the transition
between an initial random stage and a stage of coherent turbulent structures. Dynamic models performed well for simulating
the energy spectrum and the change of GS properties with time; anisotropy is not a necessary feature under the present simulation
conditions, although one of the special features of stratified turbulence is anisotropy. This may be because the present grids
for large-eddy simulation were fine enough to resolve the patches of counter-gradient heat fluxes, which play an important
role in the evolution of turbulent energy in stratified turbulence. With respect to the domain-averaged values of SGS stresses,
only the dynamic two-parameter mixed (DTM) model produced results of the same order of magnitude as those of filtered DNS.
This is because of the terms arising from re-decomposing of the SGS stresses in the DTM model. It was also found that this
incompetence in simulating the SGS stress is not necessary to simulate GS energy evolution, as is known for wall turbulence.
Updated from the Japanese original (J Soc Nav Archit Jpn 2001; 190:27–39) 相似文献