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381.
Application of new parameterizations of gas transfer velocity and their impact on regional and global marine CO2 budgets 总被引:1,自引:0,他引:1
One of the dominant sources of uncertainty in the calculation of air–sea flux of carbon dioxide on a global scale originates from the various parameterizations of the gas transfer velocity, k, that are in use. Whilst it is undisputed that most of these parameterizations have shortcomings and neglect processes which influence air–sea gas exchange and do not scale with wind speed alone, there is no general agreement about their relative accuracy.The most widely used parameterizations are based on non-linear functions of wind speed and, to a lesser extent, on sea surface temperature and salinity. Processes such as surface film damping and whitecapping are known to have an effect on air–sea exchange. More recently published parameterizations use friction velocity, sea surface roughness, and significant wave height. These new parameters can account to some extent for processes such as film damping and whitecapping and could potentially explain the spread of wind-speed based transfer velocities published in the literature.We combine some of the principles of two recently published k parameterizations [Glover, D.M., Frew, N.M., McCue, S.J. and Bock, E.J., 2002. A multiyear time series of global gas transfer velocity from the TOPEX dual frequency, normalized radar backscatter algorithm. In: Donelan, M.A., Drennan, W.M., Saltzman, E.S., and Wanninkhof, R. (Eds.), Gas Transfer at Water Surfaces, Geophys. Monograph 127. AGU,Washington, DC, 325–331; Woolf, D.K., 2005. Parameterization of gas transfer velocities and sea-state dependent wave breaking. Tellus, 57B: 87–94] to calculate k as the sum of a linear function of total mean square slope of the sea surface and a wave breaking parameter. This separates contributions from direct and bubble-mediated gas transfer as suggested by Woolf [Woolf, D.K., 2005. Parameterization of gas transfer velocities and sea-state dependent wave breaking. Tellus, 57B: 87–94] and allows us to quantify contributions from these two processes independently.We then apply our parameterization to a monthly TOPEX altimeter gridded 1.5° × 1.5° data set and compare our results to transfer velocities calculated using the popular wind-based k parameterizations by Wanninkhof [Wanninkhof, R., 1992. Relationship between wind speed and gas exchange over the ocean. J. Geophys. Res., 97: 7373–7382.] and Wanninkhof and McGillis [Wanninkhof, R. and McGillis, W., 1999. A cubic relationship between air−sea CO2 exchange and wind speed. Geophys. Res. Lett., 26(13): 1889–1892]. We show that despite good agreement of the globally averaged transfer velocities, global and regional fluxes differ by up to 100%. These discrepancies are a result of different spatio-temporal distributions of the processes involved in the parameterizations of k, indicating the importance of wave field parameters and a need for further validation. 相似文献
382.
WAN De-Cheng 《船舶与海洋工程学报》2007,6(2):51-58
In this paper, an efficient multigrid fictitious boundary method (MFBM) coupled with the FEM solver package FEATFLOW was used for the detailed simulation of incompressible viscous flows around one or more moving NACA0012 airfoils. The calculations were carried on a fixed multigrid finite element mesh on which fluid equations were satisfied everywhere, and the airfoils were allowed to move freely through the mesh. The MFBM was employed to treat interactions between the fluid and the airfoils. The motion of the airfoils was modeled by Newton-Euler equations. Numerical results of experiments verify that this method provides an efficient way to simulate incompressible viscous flows around moving airfoils. 相似文献
383.
Junbo Jia 《Journal of Marine Science and Technology》2007,12(1):43-57
To reduce the area on deck occupied by each car and the labour and time required for lashing and unlashing cars, it has been
proposed by the author that in some conditions, cars on decks could be transported without lashing. To evaluate cargo securing
based on this “lashing-free” concept, computational code was developed to calculate the vehicle–deck interactions for various
ship motions. The code was structured by incorporating a vehicle model into a piece of ship motion calculation code. A series
of time-domain simulations were conducted to evaluate vehicle securing. It was found that for a target ship consisting of
a 6000-unit Ro-Ro vessel, vehicle securing is mainly influenced by the ship's rolling motions and is highly dependent on the
wave height and loading conditions. It was suggested from the analysis that vehicles could be secured without being lashed
in a large area of the ship in specific weather conditions and on some routes with less adverse sea states. However, it is
still suggested that conventional lashing holes should be constructed on the deck because in severe sea states the cars will
still need to be lashed. The limitations of the current investigations are also presented.
The relevant research work was carried out at the Division of Ship Design and Engineering, Department of Shipping and Marine
Technology, Chalmers University of Technology. 相似文献
384.
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
385.
An efficient method for calculation of the slamming pressures on ship hulls in irregular waves is presented and validated
for a 290-m cruise ship. Nonlinear strip theory was used to calculate the ship–wave relative motions. The relative vertical
and roll velocities for a slamming event were input to the slamming calculation program, which used a two-dimensional boundary
element method (BEM) based on the generalized 2D Wagner formulation presented by Zhao et al. To improve the calculation efficiency,
the method was divided into two separate steps. In the first step, the velocity potentials were calculated for unit relative
velocities between the section and the water. In the next step, these precalculated velocity potentials were used together
with the real relative velocities experienced in a seaway to calculate the slamming pressure and total slamming force on the
section. This saved considerable computer time for slamming calculations in irregular waves, without significant loss of accuracy.
The calculated slamming pressures on the bow flare of the cruise ship agreed quite well with the measured values, at least
for time windows in which the calculated and experimental ship motions agreed well. A simplified method for calculation of
the instantaneous peak pressure on each ship section in irregular waves is also presented. The method was used to identify
slamming events to be analyzed with the more refined 2D BEM method, but comparisons with measured values indicate that the
method may also be used for a quick quantitative assessment of the maximum slamming pressures. 相似文献
386.
Udo Helge Fox 《WMU Journal of Maritime Affairs》2007,6(1):75-87
Just twenty five years have passed since the International Maritime Organization (IMO) provided the legal and internationally
harmonized framework for maritime search and rescue operations. While a number of nations only had to adapt their well-established
national services it took great efforts for other nations to develop agencies able to fulfil or outstrip minimum requirements.
However, the majority of nations (well aware of the humanitarian nature of that task) have been afraid to cope with this challenge
and the related financial burdens since the benefits to local, regional, or even national economies are not always clear to
the relevant national administrating authorities. 相似文献
387.
FU Ming-Yu BIAN Xin-Qian SHI JiCollege of Power Nuclear Engineering Harbin Engineering University Harbin China 《船舶与海洋工程学报》2002,1(1):41-46
All kinds of reasons are analysed in theory and a fault repository combined with local expert experiences is establishedaccording to the structure and the operation characteristic of steam generator in this paper. At the same time, Kohonen algo-rithm is used for fault diagnoses system based on fuzzy neural networks. Fuzzy arithmetic is inducted into neural networks tosolve uncertain diagnosis induced by uncertain knowledge. According to its self-association in the course of default diagnosis. thesystem is provided with non-supervise, self-organizing, self-learning, and has strong cluster ability and fast cluster velocity. 相似文献
388.
'Port competition' is a rather puzzling expression. This paper approaches it literally, searching for precise meanings. In seaports that contain complex and changeable mixtures of public and private enterprise, who competes and why? The answers to these questions are not conclusive but suggestive indications are found in the US, UK and northwestern Europe. Finally, we discuss what seem to be the key influential factors which may impact on the competitiveness of a port. 相似文献
389.
Taek S. Jang Hang S. Choi Takeshi Kinoshita 《Journal of Marine Science and Technology》2000,5(4):181-188
This paper illustrates how to estimate a wave source generating a wave system, including local waves, with the assumption
of linear dispersive waves of two dimensions. The estimation of wave source is realized by using an inverse problem. Unfortunately,
the inverse problem is ill-posed in the sense of stability, since the wave source information included in local waves diminishes
as the distance from the wave source increases. In the area of applied mathematics, there are well-developed methods to tackle
ill-posed problems, which are called regularizations. In this paper, three different regularizations which are well known
in applied mathematics are introduced and investigated to learn whether they are applicable to the present problem of the
estimation of wave source. From the numerical experiments, it is shown that the estimation is realized by the regularizations
introduced in this study, so that they can be applied to the determination of a wave source generating a wave system including
local waves.
Received: June 6, 2000 / Accepted: February 7, 2001 相似文献
390.
HANBing ZHAOGuo-liang 《船舶与海洋工程学报》2004,3(1):24-27
The course-keeping control of underactuated hovercraft with two aft propellers was considered. The control of the heading error and cross-track error was accomplished by the yaw torque merely in this case. The hovercraft dynamic model is nonlinear and underactuated. At first the Controllability of course-keeping control for hovercraft was proved, then a course-keeping control law was derived that keeps hovercraft heading constant as well as minimizes the lateral movement of hovercraft. The proposed law guarantees heading error and sway error all converge to zero exponentially. Simulation tests were carried out to illustrate the effectiveness of the proposed control law. For further research, the disturbance influence would be considered in the dynamic equations. 相似文献