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11.
The hydrographic surveys in an area immediately northeast of Taiwan showed that the Kuroshio surface water intruded onto the shelf in the spring and there was a thick mixed layer and weak vertical stratification in the Kuroshio at the time. During the summer season, a strong thermocline was developed in the Kuroshio and the flow shifted offshore from Taiwan in front of the continental shelf break of the East China Sea. A numerical model is used to examine the effect of this seasonal thermocline on the flow pattern of the survey area. We find that the surface strength of the disturbance above the Su-Ao ridge is closely related to the occurrence of the on-shelf intrusion of Kuroshio. The presence of a seasonal thermocline in the Kuroshio can greatly diminish this disturbance in the surface level. 相似文献
12.
Allowing a structure to uplift and rock during an earthquake is one way in which activated forces can be capped and damage to the structure avoided or minimised. Slip‐friction connectors (also known as slotted‐bolt connectors) were originally developed for use in steel construction, but for this research have been adapted for use as hold‐downs in an experimental 2.4 m × 2.4 m rigid timber shear wall. A novel approach is used to achieve the desired sliding threshold in the connectors, and the wall uplifts when this threshold is reached. From a series of quasi‐static cyclic tests, it is shown that slip‐friction connectors can impart ductile and elasto‐plastic characteristics to what would otherwise be essentially brittle structures. Because forces on the wall were capped by the slip‐friction connectors to levels well below the design level, no damage to the wall was observed. Self‐centring potential was also found to be excellent. The slip‐friction connectors themselves are of a unique design and have proven to be robust and durable, adequately performing their duty even after almost 14 m of cumulative travel under high contact pressures. To resist base shear without unduly affecting rocking behaviour, a new type of shear‐key is proposed and implemented, and a procedure developed to quantify its influence on overall wall behaviour. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
13.
Previous investigations have suggested that wind stress curl, the balance of influx- and outflux-induced upwelling, as well
as a positive vorticity source fed from the left flank of the Kuroshio are all possible mechanisms that contribute to a persistent
cyclonic gyre in the South China Sea (SCS). Studies have also suggested that the loop current that forms from the Kuroshio
intrusion in the Luzon Strait, similar to the Loop Current in the Gulf of Mexico (GOM), has rarely been observed in the northern
SCS. In this research, an idealized numerical model driven by annual mean wind stress was adopted to investigate the relative
importance of dynamic processes that control the mean flow pattern of Kuroshio in the Luzon Strait and regulate circulation
in the SCS. An analysis of results drawn from numerical experiments suggests that the three mechanisms are of approximately
equal importance in the formation of the persistent cyclonic gyre in the northern SCS. Unlike the Gulf Stream which enters
the Gulf of Mexico through the Yucatan Channel, the two topographic ridges that align nearly meridionally in the Luzon Strait
keep the Kuroshio flowing roughly northward without distinct intrusion into the SCS. Unsurprisingly, an anticyclonic loop
current similar to the Gulf Stream pathway in the GOM was barely observed in the northern SCS. 相似文献
14.
Typhoons can cause substantial sea surface cooling (typically 2–4 °C), which is usually biased to the right side of the storm track. Under influence of the complex bathymetry of the southern Taiwan Strait (TS), two types of sea surface temperature (SST) response, cooling and warming, each associated with a different type of typhoon track were identified using satellite and mooring observations. When a typhoon moved westward (or northwestward) and passed through the TS (track A), the SST cooling in the TS was biased toward the left of the storm track. Numerical model results indicated that in track A, strong wind stress accelerates the flow east of the Taiwan Banks and drove the bottom flow to uplift due to the topography. Moreover, both wind stress and wind stress curl enhanced the Luzon loop. After the typhoon passed, the mean circulation was modified around strong cooling in the southern TS, causing more South China Sea surface water to be distributed to the Kuroshio region. However, when a typhoon moved westward (or northwestward) and passed south of the TS, SST warming was induced in the southern TS (track B). The model results indicated that when the typhoon passed to the south of the TS, the typhoon-induced horizontal divergent flow travelled to the north, where it encountered the shallower shelf of the TS that was confined to the water, causing warm water transported into this area to accumulate and downwelling to occur. This can be regarded as redistributing the heat content in the shelf area. After the typhoon, the thickened mixed layer resulting from downwelling prevented the formation of near-inertial waves and reduced the vertical mixing. 相似文献
15.
Numerical study on the interactions between a mesoscale eddy and a western boundary current 总被引：4，自引：3，他引：1
A reduced-gravity primitive equation eddy resolving model has been used to study the decay of a mesoscale eddy as it migrates
toward a western boundary current (WBC) region. The model results indicated that the gradient of the relative vorticity to
the east of the WBC is an important factor in the interaction between an eddy and a WBC. A circular eddy is deformed into
an elliptical form during the eddy–WBC interaction with the major axis of a cyclonic/anticyclonic eddy aligning in the NW/NNE
direction, respectively. Because of the difference in the major axes orientations for the cyclonic and anticyclonic eddies,
the kinetic energy transfer between a WBC and a particular eddy has very different behavior. A cyclonic eddy loses its energy
to the mean field, whereas an anticyclonic eddy can obtain energy from the mean flow during the WBC–eddy interaction. An anticyclonic
eddy, however, still decayed from losing its water and friction dissipation during the interaction period. 相似文献
16.
Shi-Chie Fuh Chir-Cherng Chern Shov-Chian Liang Yu-Liang Yang Suh-Huey Wu Tzy-Yi Chang Jen-Yang Lin 《Marine and Petroleum Geology》2009
Biogenic gas was accidentally discovered and produced from the Plio/Pleistocene formation of the Hsinying gas field in southwestern Taiwan in 1989. A stratigraphic trapping mechanism related to the evolution of submarine canyon systems in the Plio-Peistocene foreland basin has been proposed in a previous study which explained underestimated recoverable gas reserve before drilling. To verify this shallow gas exploration hypothesis and to systematically evaluate the biogenic gas generation and entrapment potential of the submarine canyon systems, seismic interpretation, high-resolution sequence stratigraphic interpretation, seismic attribute analysis and geochemical analysis were performed and integrated in this study. Twenty-nine submarine canyons mapped mainly trend in a NE direction, except the NW trending Eurchungchi submarine canyons located near the Chiali paleo-high. Bright seismic amplitudes were often observed at the incised valley heads of the canyon systems. The shales located near the incised valley heads and deposited during flooding stage possess the highest biogenic gas generation potential, as canyon fill reveals the second highest. Due to the high sediment accumulation rate in the foreland basin, organic matter in such a depositional environment tends to become diluted. A Class III AVO anomaly, inverted impedance lower than 4.7 e + 6 kg/M3*M/S and A/B (the ratio between the target horizon amplitude and the RMS amplitude from the background strata) greater than 1.78 were identified as valid direct gas indicators as sand is buried shallower than 1000 m. Class IV AVO anomaly and A/B greater than 1.4 were concluded to be the indicators of gas sand in the case that sand is buried deeper than 1600 m. Based on the results of sequence stratigraphic interpretation and the consistency between spatial geometries of seismic attributes and those of the submarine canyons, a stratigraphic trap associated with the incised valley heads was concluded to be the original gas entrapment style of the Hsinying and the Kuantian gas fields. Biogenic gas migrated after being trapped startigraphically, hence contributing to the present-day gas field structure. Due to the prevalent erosional features of the submarine canyons on the time structural maps, different types of stratigraphic traps formed in combination with faults and submarine canyons can be recognized easily. 相似文献
17.
A numerical study of the summertime flow around the Luzon Strait 总被引：3，自引：0，他引：3
Luzon Strait, a wide channel between Taiwan and Luzon islands, connects the northern South China Sea and the Philippine Sea.
The Kuroshio, South China Sea gyre, monsoon and local topography influence circulation in the Luzon Strait area. In addition,
the fact that the South China Sea is a fairly isolated basin accounts for why its water property differs markedly from the
Kuroshio water east of Luzon. This work applies a numerical model to examine the influence of the difference in the vertical
stratification between the South China Sea and Kuroshio waters on the loop current of Kuroshio in the Luzon Strait during
summer. According to model results, the loop current’s strength in the strait reduces as the strongly stratified South China
Sea water is driven northward by the southwest winds. Numerical results also indicate that Kuroshio is separated by a nearly
meridional ridge east of Luzon Strait. The two velocity core structures of Kuroshio can also be observed in eastern Taiwan.
Moreover, the water flowing from the South China Sea contributes primarily to the near shore core of Kuroshio. 相似文献
18.
The upper ocean response to a moving typhoon 总被引：1，自引：0，他引：1
The upper ocean response to the translation speed of typhoons is studied using a three-dimensional primitive equation model.
Similar models studied previously have applied stability criteria rather than the diffusion term to simulate the vertical
mixing process. This study retains the diffusion term and uses the level-2 turbulence closure scheme to estimate the vertical
eddy viscosity. The model results indicate that in the forced period, the mixed-layer temperature decrease is greater for
a slow-moving storm due to stronger upwelling caused by the longer residence time. A fast-moving storm can attain a similar
cooling intensity in the wake period if its residence time allows the wind to resonate with the current. The significant downward
momentum diffusion and advection in the first few inertial periods of these events leads to strong, persistent inertial pumping
throughout the upper ocean in the wake period. The mixed layer is further cooled by turbulent mixing supported by vertical
current shears. Meanwhile, the upper thermocline exhibits a compensating temperature increase. The vertical transfer magnitude
and penetration scale are smaller in the slow-moving case, when the inertial motion decays rapidly. The model results also
indicate that the dominant cooling process can be inferred from the non-dimensional storm speed. However, this value may be
misleading for rapidly moving storms in which the current response is so distant from the storm that little wind work is performed
on the ocean. 相似文献
19.
Interactions of Mesoscale Eddy and Western Boundary Current: A Reduced-Gravity Numerical Model Study
A reduced-gravity primitive equation eddy resolving model is used to study the interaction of a typhoon-induced eddy and a wind-driven general circulation. A typhoon-induced eddy is characterized by a core with a relative vorticity of the same order as the local Coriolis parameter. This eddy is neutrally stable relative to a disturbance induced by the westward advection of the eddy, due to the planetary β-effect. Hence, its evolution in the open ocean is similar to the classical frontal geostrophic eddy. Within the western boundary flow regime, the eddy is entrained northward by the mean circulation. This northward eddy advection and the mean-vorticity advection due to eddy flow induce another disturbance with a north-south asymmetry into the circular eddy. Together with the zonal asymmetric disturbance, associated with the planetary β-effect, the original circular eddy becomes unstable. The nonlinear eddy-flow interactions in the eastern flank of a western boundary current causes the eddy to deform quickly into an ellipse and lose its waters and energy into the mean circulation. 相似文献
20.
A general analytical solution for flow to a single horizontal well by Fourier and Laplace transforms
The objective of this paper is to present an analytical solution for describing the head distribution in an unconfined aquifer with a single pumping horizontal well parallel to a fully penetrating stream. The Laplace-domain solution is developed by applying Fourier sine, Fourier and Laplace transforms to the governing equation as well as the associated initial and boundary conditions. The time-domain solution is obtained after taking the inverse Laplace transform along with the Bromwich integral method and inverse Fourier and Fourier sine transforms. The upper boundary condition of the aquifer is represented by the free surface equation in which the second-order slope terms are neglected. Based on the solution and Darcy’s law, the equation representing the stream depletion rate is then derived. The solution can simulate head distributions in an aquifer infinitely extending in horizontal direction if the well is located far away from the stream. In addition, the solution can also simulate head distributions in confined aquifers if specific yield is set zero. It is shown that the solution can be applied practically to evaluate flow to a horizontal well. 相似文献