Unsteady Chains of Wave Structures and Anomalous Transport of Passive Admixture in a Barotropic Jet Flow

Izvestiya, Atmospheric and Oceanic Physics - The anomalous transport of passive admixture is studied when unsteady chains of wave structures with closed streamlines are excited in a barotropic jet...     

Radiative Instability of a Barotropic Jet Flow in a Rotating Stratified Atmosphere

Izvestiya, Atmospheric and Oceanic Physics - This paper investigates the stability of a jet flow with a piecewise linear velocity profile in a rotating stratified atmosphere. The linearized set of...     

Chaotic Advection of the Shallow Kuroshio Coastal Waters

The shallow coastal water of the Enshu-Nada Sea (ENSW) recirculates regardless of whether the Kuroshio path is straight or has meanders. The recirculation is formed as a result of flow separation at the sharp coastline. The outputs of a recent numerical simulation of the Kuroshio current, including case of a short-term meander caused by an anticyclonic eddy, were analysed to track the motion of the ENSW. In contrast to the steady-flow cases, the unsteady cases showed that the ENSW discharges into the Kuroshio Extension region and intrudes further north into the Kuroshio-Oyashio confluence region due to chaotic advection. Two hyperbolic stagnation points of the velocity field characterise the transport paths; one south of the Izu peninsula and the other at the Kuroshio Extension. This mechanism exists even without the Ekman drift and may play an important role in the transportation of the fish eggs and larvae from the southern Japan spawning ground to the food abundant Kuroshio-Oyashio transition zone. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diffusion-Rotational Parameterization of Eddy Fluxes of Potential Vorticity: Barotropic Flow in the Zonal Channel

Izvestiya, Atmospheric and Oceanic Physics - The problem of parameterizing the eddy flux of a potential vorticity is discussed. The traditional diffusion parameterization is complemented by the...     

Barotropic instability of a viscous boundary jet

The barotropic instability of a boundary jet on a beta plane is considered with emphasis on the effect of internal viscosity. An eigenvalue problem for the disturbance equations and its inviscid version are solved by the aid of numerical methods, and instability characteristics are determined as functions of the Reynolds numberR for various values of the beta-parameter. Typical disturbance structures (eigenfunctions) are also computed. Numerical examples show that the minimum critical Reynolds numberR _cr for instability is smaller than 100. At a Reynolds number of the order of hundreds, there appears a second mode of instability in addition to the first unstable mode originating atR _cr ; a kind of ‘resonance’ between the first and second eigenvalues occurs at the particular value ofR. The neutral stability curves are accordingly multi-looped. Although each of the two unstable modes asymptotically approaches its inviscid counterpart asR→∞, the asymptotic approach to the inviscid limit is rather slow and the effect of varyingR is conspicuous even atR∼O (10⁴). It is thus demonstrated that the Reynolds number is an essential stability parameter for real boundary jets. The main part of the material contained in this paper was presented at 1981-Autumn Assembly of the Oceanographical Society of Japan.     

Barotropic disturbances caused by a point storm in aβ-plane ocean

Barotropic equation for vorticity balance in the-plane is solved for a volume transport stream function with a northward moving wind stress torque concentrated at a point (tweak). Asymptotic techniques are applied to the solution expressed by Fourier type integrals. In the front zone (northern half from the tweak) the stream function behaves asO(¦X¦^–5) whereX is a scaled eastward coordinate. In the wake, the stream function behaves asO(¦X¦^–1/2) within a wedge bounded by the westward axis and a line directed SSE approximately, but behaves asO(¦X¦^–5) in the rest of the half plane. On these boundaries it behaves asO(¦X¦^–5/2) andO(¦X¦^–1/3), respectively. East-west asymmetry is a result of asymmetry in zonal propagation of the planetary waves, which also cause the wavy pattern of the streamline in the western half of the wake. Friction is most effective in decreasing the stream function in the south to SSW sector and least effective to the west. Effect of divergence changes the wave pattern in the western half of the wake but does not change magnitude of the stream function. It is speculated that abnormal changes in daily mean sea levels observed in 1965 to 1971 along the south coast of Japan may be caused by the wake effect of moving typhoons east off Japan.     

流式细胞术检测对虾白斑症病毒(WSSV)对克氏原螯虾血细胞的感染

用WSSV粗提液人工感染克氏原螯虾,感染后分别在6,12,18,24 h采血分离血细胞,通过WSSV的混合单抗和FITC标记的羊抗鼠二抗的间接免疫荧光染色,应用流式细胞仪检测病毒对克氏原螯虾血细胞的感染并分析感染强度.结果表明:分离获得的血细胞形态完好,感染后血细胞内的病毒被标记上了绿色荧光;流式检测发现,随感染时间延长,被感染细胞的百分率及平均荧光强度均逐渐升高,反映血细胞的病毒感染程度逐渐加深;PCR检测同时证实人工感染后各采样点血细胞样品均为WSSV阳性.     

Three-Dimensional Instability of Flow Around Two Circular Cylinders in Tandem Arrangement

The spatial evolution of vortices and transition to three-dimensionality in the wake of two circular cylinders in tandem arrangement have been numerically studied. An improved virtual body method developed from the virtual boundary method is used here. A Reynolds number range between 220 and 270 has been considered, and the spacing between two cylinders is selected as L/D = 3 and L/D = 3.5. When L/D = 3, the secondary vortices of Mode-A are seen to appear at Re = 240 and persist over the range of the Reynolds number of 240 - 270. When L/D = 3.5, the similar critical Reynolds number has been found at Re = 250. No obvious discontinuity has been found in the Strouhal-Reynolds number relationship, and this is different from three-dimensional flow around a single cylinder at the critical Reynolds number. The spanwise wavelength is about four times the diameter of the cylinder, and it is the characteristic wavelength for ModeA instability. This paper can give some foremost insight into the three-dimensional instability of flow by complicated geometrical configuration.     

高雷诺数下近壁圆柱绕流数值模拟与分析

近壁圆柱绕流问题在海底悬跨管道的研究中具有重要的意义。在绕流阻力、升力以及海底土壤的耦合作用下,海底管道所发生的移位、悬跨等现象对于海底管道的安全运行构成了很大的威胁。正确预测各种绕流条件下管流之间的作用力是保证油气管道安全的首要任务。海底管道在极端海洋环境条件下的管、流相互作用为高雷诺数绕流问题,处于高雷诺数下的绕流模拟比处于低雷诺数下的绕流模拟要复杂很多,它需要更精细的网格以及合适的湍流模型。此文对处于悬跨状态下的海底管道进行数值研究,给出不同间隙比下海流绕流海底管道的流场结构形态,分析了间隙比对绕流阻力和绕流升力的影响,为进一步研究海底悬跨管道的受力和变形提供载荷边界数据。     

赤道东太平洋弯曲急流区质点轨迹及混沌运动机制

利用运动学模型 ,研究了弯曲急流控制参数为定常和发生周期扰动时的流体质点运动轨迹以及混沌现象的产生机制。发现弯曲急流控制参数为定常时 ,流体质点的运动为规则的周期运动 ;而控制参数发生扰动时 ,可以发生流体质点在不同特征区的穿行 ,流体质点的运动具有混沌特性。弯曲急流的相速、振幅发生周期扰动均可使流体质点的运动出现混沌特性。作者从运动学上对弯曲急流区的漂流浮标混沌特性给出了解释。     

北太平洋海洋带状流的正压特性

海洋中包含着多种时空尺度的运动过程,海洋带状流是近年来发现的一种新的流动形式。这种流动现象介于地转湍流和准定常流之间。上层海洋中大尺度运动的强度远大于海洋带状流而将其遮盖,因而带状流需要借助滤波方法提取出来。本研究基于纬向速度数据,通过切比雪夫高通滤波提取了北太平洋海洋带状流的三维结构,定义了“流向稳定度”指数,量化分析了北太平洋海域带状流的正压特性,从而进一步加深了对北太平洋海洋带状流结构特征的认识。     

Investigation of Barotropic and Baroclinic Seiches in Bounded Sea Basins

We present a survey of works carried out at the Wave-Theory Department of the Marine Hydrophysical Institute of the National Academy of Sciences of Ukraine for the last ten years and devoted to investigation of free and forced waves in bounded basins. Our attention is focused on the results of investigation of internal waves in basins of variable depth for the case of three-layer stratification of the liquid. The profiles of the bottom of the basin and interfaces are regarded as parabolic. Analytic solutions are obtained and the periods of oscillations of the free surface and interfaces for the first and second modes are determined. The dependences of the characteristics of baroclinic waves on the geometry of the basin and parameters of stratification are analyzed.     

Suppression of Flow Separation Around A Circular Cylinder by Utilizing Lorentz Force

Both experimental and numerical investigations on the flow past a cylinder under the influence of Lorentz force （electromagnetic force） were conducted in an electrically low-conducting fluid. The Lorentz force is applied beth locally, wholly and periodically on the surface of the cylinder, and their control effects for flow ,separation were investigated Both experimental and numerical results show that Lorentz force can suppress the flow separation with Lorentz force applied on beth local and whole surface of the cylinder. However, when the periodic and opposite Lorentz force adopted, the cylinder wake cannot be stabilized.     

Barotropic tidal mixing effects in a coupled climate model: Oceanic conditions in the Northern Atlantic

Impacts of mixing driven by barotropic tides in a coupled climate model are investigated by using an atmosphere–ocean–ice–land coupled climate model, the GFDL CM2.0. We focus on oceanic conditions of the Northern Atlantic. Barotropic tidal mixing effects increase the surface salinity and density in the Northern Atlantic and decrease the RMS error of the model surface salinity and temperature fields related to the observational data.     

不等直径串列双圆柱体绕流的数值模拟

利用Fluent软件模拟雷诺数为200时不同间距比G/D和直径比d/D情况下的圆柱绕流现象。根据模拟结果分析G/D和d/D对圆柱体的涡脱落形态,大、小柱体的升力,阻力系数和St数的影响,结果表明涡脱落形态随着G/D和d/D的变化呈现不同的形式,在G/D小于临界间距比时呈现单一涡脱落形态,在G/D大于临界间距比时,呈现双旋涡脱落形态;临界间距比随着d/D增大而增大。在临界间距比附近大、小柱体的升力和阻力系数值及St数变化较大,大、小柱体的St数具有相同的变化规律,St随着d/D的增大而减小。     

Interaction between Rossby Waves and a Jet Flow: Basic Equations and Verification for the Antarctic Circumpolar Current

Izvestiya, Atmospheric and Oceanic Physics - Abstract—The article focuses on the interaction of Rossby waves in the ocean with zonal jet flows. A new approach is proposed to show that...     

无结构网格二维海洋模式的正压梯度力算法改进

基于一套自主研制的无结构网格二维河口海洋数值模式A2D,在大圆湖理想模型下,通过与解析解进行比较分析,采用不同架构配置,改进设计正压梯度力计算方法。改进后的算法中引入了从算架构的配置,以配合主算架构,得到更佳的稳定性。通过水位场平面分布与单点过程线可以发现,三组试验的算法均获得了较好的精度和比原算法更好的稳定性,其中TSNS配置算法(中心点计算水位、边中点计算流速的主算架构,配合节点计算水位、边中点计算流速的从算架构)由于其主算架构更接近结构网格下的C网格,在守恒性、移动潮滩边界处理等方面具有一定优势和便利性,有利于在实际海洋中的计算。将TSNS配置算法在江浙沿海进行试算,水位验证结果与实测基本符合,与原A2D模式计算水位之间无显著差异。TSNS算法在稳定性方面的改进,有助于提升模式升级为三维后的稳定性,为今后模式成功升级为三维打下基础。     

Transformation of the Level of Barotropic Ocean under an Elliptic Region of Disturbances of a Baric Field

We study elevations of the level of a homogeneous ocean caused by a large-scale elliptic anomaly of the field of atmospheric pressure and determine the conditions under which Earth's rotation and the asymmetry of the region of disturbances of the baric field lead to significant deviations of the ocean level from its values given by the law of inverted barometer. Our investigation is based on the numerical analysis of the integral solution of the linear problem. It is shown that the deviations from the law of inverted barometer are especially pronounced in shallow-water regions, at high latitudes, and for strongly asymmetric regions of disturbances of atmospheric pressure.     

Data Assimilation Modeling of the Barotropic Tides in the Korea/Tsushima Strait

During 1999–2000, 13 bottom mounted acoustic Doppler current profilers (ADCPs) and 12 wave/tide gauges were deployed along two lines across the Korea/Tsushima Strait, providing long-term measurements of currents and bottom pressure. Tidally analyzed velocity and pressure data from the moorings are used in conjunction with other moored ADCPs, coastal tide gauge measurements, and altimeter measurements in a linear barotropic data assimilation model. The model fits the vertically averaged data to the linear shallow water equations in a least-squares sense by only adjusting the incoming gravity waves along the boundaries. Model predictions are made for the O₁, P₁, K₁, μ₂, N₂, M₂, S₂, and K₂ tides. An extensive analysis of the accuracy of the M₂ surface-height predictions suggests that for broad regions near the mooring lines and in the Jeju Strait the amplitude prediction errors are less than 0.5 cm. Elsewhere, the analysis suggests that errors range from 1 to 4 cm with the exception of small regions where the tides are not well determined by the dataset. The errors in the model predictions are primarily caused by bias error in the model’s physics, numerics, and/or parameterization as opposed to random errors in the observational data. In the model predictions, the highest ranges in sea level height occur for tidal constituents M₂, S₂, K₁, O₁, and N₂, with the highest magnitudes of tidal velocities occurring for M₂, K₁, S₂, and O₁. The tides exhibit a complex structure in which diurnal constituents have higher currents relative to their sea level height ranges than semi-diurnal constituents.