The effect of horizontal Coriolis force on internal wave-mean flow interaction

-In this paper, an improvement and revision of the theory of Miiller (1974, 1976), has been made under two conditions: (1) the horizontal component of the Coriolis force has been taken into account in the equations of motion for the internal wave field; and (2) the role of internal waves with frequencies close to the inertial frequency has been considered. The values of the viscosity coefficients and the diffusivity coefficients obtained in this paper are: Theappearance of the cross-diffusion (vc) of momentum is a natural result from the effect of the horizontal Coriolis force. Therefore the role of the horizontal shear of the mean flow cannot be absolutely separated from that of the vertical shear. So far in testing Muller's theory, the approximation of effective wave stress obtained by Ruddick and Joyce (1979) was extensively used, but it has to be revised under the conditions of this paper. The revised approximation shows that the internal waves with low frequencies close to the inertial frequency pl     

Interpretation of GLORIA side-scan sonar imagery for the Coriolis Troughs of the New Hebrides backarc

The Coriolis backarc troughs in southern Vanuatu are elongate, rhomboidal depressions with steep walls and flat floors, formed by extension. The Futuna Trough is relatively immature and, like Erromango Basin, shows no recent volcanism. Vate Trough is most developed, and its floor is largely covered by lava fields. Between Vate and Banks Islands, the backarc has three distinct characters: in the south it is sediment-draped; centrally, either lava projects through sediment cover or the area is covered by slide debris; in the north, a steep escarpment may result from collision of the arc with the D'Entrecasteaux Ridge.     

On the Theory of Symmetric Instability of Time-Periodic Flows with a Complete Account for the Coriolis Force

Izvestiya, Atmospheric and Oceanic Physics - The symmetric (inertial) parametric instability of time-periodic flows with a linear velocity profile has been investigated, with a complete account for...     

The role of Coriolis in sandbank formation due to a headland/island system

Tidal flow past a headland was modelled and the resulting sandbank formation due to bedload transport by eddy systems was examined with particular emphasis on the role of Coriolis. The headland configuration was extended to the more complex case of a headland with a detached island and the role of Coriolis in sandbank formation was again examined. In the headland case, the contribution of Coriolis resulted in the expected change in bed level at the centre of the residual eddies (positive contribution for the cyclonic eddy and negative change for the anticyclonic eddy). In the headland/island case, the role of Coriolis in the resulting bed level change was a function of eddy shedding from the island, defined by the island wake parameter. When eddy shedding occurred, the inclusion of Coriolis had a large magnitude effect on creating flood/ebb sandbank asymmetry. When eddies remained attached to the island, Coriolis had a minor role in the magnitude of this asymmetry.     

A force source of tectonic movement-A secondary mass center restoring force

The earth system discussed in this paper is composed of two secondary particle systems: a water body and a base body. The base body shows different behaviours under the actions of long term and short term effects of its rheologic character and viscoelasticity. The short term effects result in a secondary particle system to deviate from its original position, and produce a secondary mass center restoring force directly proportional to the deviating distance. The long term effects result in the earth's material producing a secondary mass center restoring motion under the action of the secondary mass center restoring force.     

4D analogue modelling of transtensional pull-apart basins

Scaled sandbox models were used to investigate the 4D evolution of pull-apart basins formed above underlapping releasing stepovers in both pure strike-slip and transtensional basement fault systems. Serial sectioning and 3D volume reconstruction permitted analysis of the full 3D fault geometries. Results show that very different pull-apart basins are developed in transtension compared to pure strike-slip. Both types of models produced elongate, sigmoidal to rhomboidal pull-apart systems, but the transtensional pull-apart basins were significantly wider and uniquely developed a basin margin of en-echelon oblique-extensional faults. Dual, opposing depocentres formed in the transtensional model whereas a single, central depocentre formed in pure strike-slip. In transtension, a distinct narrow graben system formed above the principal displacement zones (PDZs). Cross-basin fault systems that linked the offset PDZs formed earlier in the transtensional models.Sequential model runs to higher PDZ displacements allowed the progressive evolution of the fault systems to be evaluated. In cross-section, transtensional pull-aparts initiated as asymmetric grabens bounded by planar oblique-extensional faults. With increasing displacement on the PDZs, basin subsidence caused these faults to become concave-upwards and lower in dip angle due to fault block collapse towards the interior of the basin. In addition, strain partitioning caused fault slip to become either predominantly extensional or strike-slip. The models compare closely with the geometries of natural pull-apart basins including the southern Dead Sea fault system and the Vienna Basin, Austria.     

A study of Coriolis effects on long waves propagating in an unbounded ocean, channel and basin

The effects of Coriolis force on long waves have been discussed based on gravity waves propagating in an unbounded ocean, channel and basin. In case of ocean, results show that the Coriolis effect will be significant and negligible, when the wave period is comparable to 2π/f and much shorter, respectively. Results also show in a channel, the wave amplitude and water particle velocity decrease exponentially in the positive y direction in the northern hemisphere (where f is positive). Moreover, in a basin, the Cotidal lines have been found as curves and rotate counterclockwise around the origin.     

Evaluation of methods to remove inertial force from measured model wave impact force signals

The subject of wave impact on offshore structures and their components is important to vessel designers and operators for many reasons. They are often required to quantify these impact loads. Standard methods for wave load prediction will underestimate the forces on these structures due to intermittent loading. This necessitates the use of physical model tests to establish wave impact loads. The model measurement systems are designed to have high stiffness. This ensures that the natural frequency of the structure is above the wave frequency. However, it is widely believed that impacting waves contain high-frequency energy components that cause the structure to vibrate at its modal frequencies. This impact-induced vibration is recorded by the measuring system as a force (inertial force), and corrupts the actual applied force measurement. Before scaling can occur, the inertial force must be removed from the measured signal.A number of techniques for removing inertial force from measured signals are described in the published literature. Three methods are discussed, implemented and compared in this paper. The algorithms and procedures are presented. Each technique contains inherent and unique problems, while some are common to all methods.Neither of the techniques produced results that are fully satisfactory. The main problem is unwanted high-frequency content after the application of the methods. While neither method offers the perfect solution, the use of digital filtering techniques is recommended based on their relative performance and ease of implementation.     

近岸多波束测量中的GPS-RTK差分技术及其受影响的因素

分析了近岸多波束测量中应用GPS-RTK差分技术对船只导航与定位,对在受波浪影响的多波束测量中,船只所受潮汐、换能器吃水的动态变化量等诸影响因素的改正以及船只的运动姿态纠正等问题进行了讨论。使用GPS-RTK系统可以有效地解决潮汐(水位)、波浪影响和换能器吃水的动态变化量对多波束测量精度综合影响的问题,如果使用"一加三"的GPS-RTK接收机,还可以实现船只姿态的高精度综合修正。同时,对4个影响GPS-RTK差分技术系统能力的主要因素应引起重视,采取措施加以解决,使近岸的多波束测量工作更加富有成效。     

A study of faulting patterns in the Pearl River Mouth Basin through analogue modeling

The Pearl River Mouth Basin is one of the most favorable areas for gas exploration on the northern slope of the South China Sea. Differences of fault patterns between shelf and slope are obvious. In order to investigate the tectonic evolution, five series of analogue modeling experiments were compared. The aim of this study is to investigate how crustal thickness influences fault structures, and compare this to the observed present-day fault structures in the Pearl River Mouth Basin. The initial lithospheric rheological structure can be derived from the best fit between the modeled and observed faults. The results indicate. (1) Different initial crustal rheological structures can produce different rift structures in the Pearl River Mouth Basin. (2) We also model that the Baiyun Sag in the southern Pearl River Mouth Basin may have had a thinned crust before rifting compared to the rest of the basin. (3) The thickness ratio of brittle to ductile crust in southern Pearl River Mouth Basin is less than normal crust, suggesting an initially hot and weak lithosphere. (4) Slightly south of the divergent boundary magma may have taken part in the rifting process during the active rift stage.     

海底边坡稳定性分析中波浪力的求解

针对浅水区波浪的非线性特性,提出了在海底边坡稳定性分析中应用椭圆余弦波理论来研究波浪力的问题,利用非线性弥散关系建立了新的适用于整个水深范围的椭圆余弦波的近似求解方法.结合工程实例,确立了海底边坡波浪力的计算步骤,并编制了计算程序.     

A finite difference solution of the shear flow over a circular cylinder

The incompressible viscous shear flow past a circular cylinder is analyzed by solving two-dimensional Navier-Stokes equations and pressure Poisson equation using a finite difference method. The shear flow is calculated for Reynolds numbers from 80 to 1000, and shear parameters up to 0.25. The numerical results indicate that the vortex shedding persists at the shear parameters up to 0.25 for the present Reynolds number range. The Strouhal number and the drag coefficient decrease as the shear parameter increases. There is a transverse force acting from the high velocity side toward the low velocity side in the shear flow.     

The role of freshwater fluxes in the thermohaline circulation: Insights from a laboratory analogue

Regime transitions in the meridional overturning circulation (MOC) and the rate of formation of deep and bottom waters are thought to be sensitive to changes in the freshwater flux at high latitudes. We model convective overturning in the presence of a surface freshwater input using laboratory experiments that are inverted relative to the ocean: we establish an equilibrium circulation forced by differential heating and cooling along the base of a box and perturb this flow by adding a stabilizing saltwater input at the ‘polar’ end of the box. An initially stable layer forms near the source of the salinity anomaly as a ‘polar halocline’. The subsequent circulation is governed largely by the ratio of salinity and thermal buoyancy supply. For small values of this ratio we observe periodic formation and breakdown of the halocline. Larger values of the flux ratio lead to subthermocline intrusions and stable layering laterally throughout the basin, isolating the bulk of the water column from the forcing boundary. The shutdown of deep overturning and formation of a shallow circulation occurs at a salinity buoyancy input of order 0.1 times the rate of loss of thermal buoyancy. This salinity buoyancy is then comparable to the buoyancy that forces the deep sinking plume below the thermocline in steady-state overturning. When the salinity buoyancy flux is removed, the circulation slowly returns to its original state.     

Finite Larmor radius magnetohydrodynamic analysis of the ballooning modes in tokamaks

In this paper, the effect of finite Larmor radius (FLR) on high n ballooning modes is studied on the basis of FLR magnetohydrodynamic (FLR-MHD) theory. A linear FLR ballooning mode equation is derived in an `U+015D - α ' type equilibrium of circular-flux-surfaces, which is reduced to the ideal ballooning mode equation when the FLR effect is neglected. The present model reproduces some basic features of FLR effects on ballooning mode obtained previously by kinetic ballooning mode theories. That is, the FLR introduces a real frequency into ballooning mode and has a stabilising effect on ballooning modes (e.g., in the case of high magnetic shear U+015D ≥ 0.8). In particular, some new properties of FLR effects on ballooning mode are discovered in the present research. Here it is found that in a high magnetic shear region (U+015D ≥ 0.8) the critical pressure gradient (α_c,FLR ) of ballooning mode is larger than the ideal one (α_c,IMHD ) and becomes larger and larger with the increase of FLR parameter b₀ . However, in a low magnetic shear region, the FLR ballooning mode is more unstable than the ideal one, and the α_c,FLR is much lower than the α_c,IMHD . Moreover, the present results indicate that there exist some new weaker instabilities near the second stability boundary (obtained from ideal MHD theory), which means that the second stable region becomes narrow.     

泥蚶同工酶谱在不同组织的差异研究

用聚丙烯酰胺电泳法对泥蚶5种组织中的19种同工酶进行检测分析,发现除其中4种酶未显示任何有活性的区带,两种酶只显示极微弱且不稳定的区带外,其他种酶类在各个组织中都显示出清晰稳定的图谱,且这些酶在分布和活性上均表现出高度的组织特异性,说明泥蚶组织中已存在相当丰富和完整的酶系统,基本具备了与高等动物相类似的机体代谢方式,而且这些酶基因的表达存在着组织分布上的自我调控机制.同时与其他贝类和高等动物相比,泥蚶的同工酶基因的表达既表现出了与其分类地位相一致的特征,又反应出在分类阶元上的特殊性.     

白令海2008年冬夏季节陆架水的差异

本文利用中国海洋大学极地变化重点实验室提供的2008年3月与7月白令海陆架水资料,对白令海200 m内水域温盐及水团进行了分析和对比,对白令海陆架区冬季水团形成机制做了初步的探讨。白令海冬季陆架水的温盐结构垂向均匀;夏季层化明显,存在垂直温盐跃层;白令海由夏季表层水和冬季水两种水团组成;白令海冬季残留水团在陆架区水深20 m处即出现,最低温度较大洋深处冬季水温偏低。     

Nonlinear Finite Element Analysis of Ocean Cables

This study has focused on developing numerical procedures for the dynamic nonlinear analysis of cable structures subjected to wave forces and ground motions in the ocean. A geometrically nonlinear finite element procedure using the isoparamnetrie curved cable element based on the Lagrangian folmulation is briefly summarized. A simple and accurate method to determine the initial equilibrium state of cable systems associated with self-weights, buoyancy and the motion of end points is presented using the load incremental method combined with penalty method. Also the Newmark method is used for dynamic nonlinear analysis of ocean cables. Numerical examples are presented to validate the present numerical method.