Numerical analysis of the flow field in a sloshing tank with a horizontal perforated plate

Liquid sloshing is a type of free surface flow inside a partially filled water tank. Sloshing exerts a significant effect on the safety of liquid transport systems; in particular, it may cause large hydrodynamic loads when the frequency of the tank motion is close to the natural frequency of the tank. Perforated plates have recently been used to suppress the violent movement of liquids in a sloshing tank at resonant conditions. In this study, a numerical model based on OpenFOAM (Open Source Field Operation and Manipulation), an open source computed fluid dynamic code, is used to investigate resonant sloshing in a swaying tank with a submerged horizontal perforated plate. The numerical results of the free surface elevations are first verified using experimental data, and then the flow characteristics around the perforated plate and the fluid velocity distribution in the entire tank are examined using numerical examples. The results clearly show differences in sloshing motions under first-order and third-order resonant frequencies. This study provides a better understanding of the energy dissipation mechanism of a horizontal perforated plate in a swaying tank.     

GPS跟踪站观测的初步结果所揭示的板内及板缘地壳水平运动

利用ＧＰＳ跟踪站的观测结果,首次获得了东亚地区板内及板缘地壳水平运动较准确的运动速率,据此分析了我国大陆及周围地区地壳水平运动的特征。结果显示：我国大陆存在着明显的向东运动趋势,从西向东位移速率逐步减小;南北向的运动差异很大,西部青藏高原存在明显的向北运动,东部存在明显的向南运动趋势。探讨了地壳水平运动的动力学问题,认为板内及板缘地壳水平运动的最直接、最主要的推动力是板块之间的相互作用力,重力势能差也是板内地壳水平运动的一个重要驱动力。     

Wave attenuation mechanism of cross-plates applied in landslide-induced tsunami in river course

Since the impounding of the Three Gorges Reservoir, the channel of the Yangtze River has become a busy watercourse and the probability of landslide-induced tsunamis has increased. In the case of landslide-induced tsunamis in the Three Gorges Reservoir, even after shipping closures in advance, there are still facilities and objects in urgent need of protection within the risk zone of the watercourse, such as wharfs, marine fueling stations, berthed ships. The emergency protection against and decay of landslide-induced tsunamis in inland watercourses is a new challenge. In this study, 37 sets of wave decay experiments were conducted with the hydromechanics numerical method. The wave decay efficiencies of common simple structures including submerged horizontal plate, horizontal plate on the water surface, inclined thin plate and cross-plates in coastal areas were compared and analyzed. Cross-plates structure showed better wave decay capacity than other simple plates. The wave decay performance of cross-plates was related to five modes of energy dissipation and transformation, namely run-up/run-down, overtopping, reflecting, return flow and disturbed wave orbital path. The type of wave had little relation with the decay performance of cross-plates, but a strong correlation with cross-plates structure, especially the height of the vertical emerged plate. The best decay performance was observed when the ratio of wave amplitude to emerged vertical plate height was between 1 and 1.5, which can reduce up to about 80% of the incoming wave amplitude. Finally, the emergency way of cross-plates applied to the decay of landslide-induced tsunami in river course is discussed. This study provides a conceptual reference for related studies to practice the attenuation of landslide-induced tsunami in reservoirs.     

相对非洲的板块运动

相对板块运动不能表明板块各自的运动速度，绝对板块运动才能表明板块在不动的地球空间中的运动速度。对于不随板块运动的观察者，ITRF的速度场是近似的。为了探求绝对运动速度，考虑到非洲板块几乎不动，利用ITRF2000速度数据，研究了相对非洲板块的板块运动，得出了全球主要板块的站速度。结果表明：相对于非洲的板块运动，在一定程度上接近绝对板块运动；南美板块和加勒比板块的ITRF2000运动方向及欧亚板块的ITRF2000运动速率，相对于绝对运动可能有显著偏差。     

利用 ITRF2008 分析全球板块运动

基于 ITRF2008 参考架下 225 个 GPS 测站的速度场对 NNR-MORVEL56 板块运动模型中13个板块的运动参数及不确定度进行估计。在测站的筛选过程中,利用全球应变率模型 GSRMv1.2 的结果对测站第二不变应变率进行双三次二维平面插值,若测站的第二不变应变率小于10－14/a,则测站位于板块的刚性区域。考虑到冰期回弹对测站速度场的影响,基于冰期回弹模型ICE-3G(VM2),用TABOO直接对测站的水平位移速率进行定量计算,若冰期回弹引起的测站水平位移速率大于0.5 mm/a,则测站位于GIA地区,应予以剔除。分别比较本文计算结果、Altamimi计算结果和基于地质资料的MORVEL板块运动模型,结果显示本文建立的板块运动模型具有较高的精度,所采用的测站筛选准则具有可行性。简要分析了本文和Altamimi计算结果的差异以及个别板块偏差较大的原因。     

陆地板块的研究及其找矿意义

本文以研究大陆板块为内容,提出了应用古基底构造来划分大陆板块的新看法。主张在研究板块水平运动时,注重于力偶转换间升降运动的研究;强调两板块间相互关系的研究。主张以活动论的观点,把有用元素的转化迁移作用,作为矿化预测的理论模式。并根据我国陆地板块及其铀矿化控矿特征,为深化研究大陆板块构造进行了初步探索。     

东亚大陆形变应力场格局演化的数值模拟

用数值模拟方法研究了印度板块和欧亚板块碰撞后40 Ma以来青藏高原的挤压隆升、东亚大陆形变及应力场的演化过程.模型将东亚大陆限定在一梯形边界框架之中,大陆岩石层被视为由幂指数律控制的薄层,它上伏在粘滞性较低的软流层之上蠕变流动.模型设定印度板块以5 cm/a的恒定速度向北推进,并视其为青藏高原挤压隆升的主要驱动力.除此可活动边界之外,其余均被设为固定边界.数值模拟结果表明,模型预测的现代水平形变速度和GPS观测的格局吻合很好;数值模拟所确定的中国及邻区之区域构造应力场格局与用地震、地质观测所推断的东亚大陆现代构造应力场也能够吻合.这一结果意味着印度板块和欧亚板块的碰撞、挤压是构成现代中国大陆内部岩石层水平形变及应力场格局的主要驱动力.模型计算还表明,大陆水平形变及应力场格局受多种因素如岩石层的力学参数,特别是边界条件的制约.     

新增大楼对地倾斜观测的影响

根据弹性力学的基本理论 ,建立了水平矩形薄板模型 ,推导了计算此类薄板影响地倾斜的基本公式。通过该模型的模拟计算 ,分别得出了由大楼质量造成的附加引力位对观测点水平摆的偏转角度和大楼负荷产生的地倾斜 ,并针对厦门地震台的实际情况 ,讨论了大楼对地倾斜观测的影响。     

板块运动地球动力学机制探究

对前人提出的多种地球动力学机制特别是地幔对流说进行剖析,提出板块运动地球动力来源于地转离极作用和旋转半径变化造成的地转不同步作用,并受到刚性岩石圈板块应力平衡作用、惯性作用和弹性作用等内在规律的制约,另外规律性的固体潮作用和偶然性的陨石撞击作用是影响板块运动的附加应力因素。     

Wave interaction with a partially reflecting vertical wall protected by a submerged porous bar

This study gives an analytical solution for wave interaction with a partially reflecting vertical wall protected by a submerged porous bar based on linear potential theory. The whole study domain is divided into multiple sub-regions in relation to the structures. The velocity potential in each sub-region is written as a series solution by the separation of variables. A partially reflecting boundary condition is used to describe the partial reflection of a vertical wall. Unknown expansion coefficients in the series solutions are determined by matching velocity potentials among different sub-regions. The analytical solution is verified by an independently developed multi-domain boundary element method(BEM) solution and experimental data. The wave run-up and wave force on the partially reflecting vertical wall are estimated and examined, which can be effectively reduced by the submerged porous bar. The horizontal space between the vertical wall and the submerged porous bar is a key factor, which affects the sheltering function of the porous bar. The wave resonance between the porous bar and the vertical wall may disappear when the vertical wall has a low reflection coefficient. The present analytical solution may be used to determine the optimum parameters of structures at a preliminary engineering design stage.     

Coherent and incoherent internal tides in the southern South China Sea

Coherent and incoherent internal tides(CITs and ICITs) in the southern South China Sea were investigated from two sets of _18-month mooring current records. The CITs were mainly composed of diurnal Q _1, O _1, P _1 and K _1 and semidiurnal M_2. The observed diurnal internal tides(ITs) were more coherent than the semidiurnal constituents. Coherent diurnal variance accounted for approximately 58% of the diurnal motion, whereas semidiurnal tides contained a much smaller fraction(35%) of coherent motion. The ICITs mainly consisted of motion at non-tidal harmonic frequencies around the tidal frequency, and showed clear intermittency. The modal decomposition of CITs and ICITs showed that CITs were dominated by mode-1, whereas mode-1 and higher modes in ICITs signals showed comparable amplitudes. CITs and ICITs accounted for approximately 64% and 36% of the total kinetic energy of internal tides, respectively.     

海南及邻区现今地壳三维运动特征及地球动力学环境分析

利用海南及邻区1999年以来GNSS资料及1970年以来水准数据获取三维运动速度场，分析地壳运动特征，结合东南亚水平运动背景场分析周缘板块对海南地块及华南地块陆缘速度场的影响。结果表明，海南岛三维运动以白沙断裂为界，岛北部以海口-屯昌为界。华南地块各观测点E向运动速率自西向东逐渐减小，至陆缘区域速率最小，各观测站间运动速率差异性小；S向运动速率自西向东逐渐增大；位于23°～26°N区域观测点的速度场与其南北两侧存在差异。华南地块运动受印度板块与欧亚板块碰撞和挤压影响，陆缘地带还受太平洋板块、菲律宾海板块活动及南海扩张运动影响，澳大利亚板块对区域运动影响较小。     

Study on the breakwater caisson as oscillating water column facility

The Oscillating Water Column(OWC)wave energy convertor with the advantage of its simple geometrical construction and excellent stability is widely employed. Recently, perforated breakwaters have been often used as they can effectively reduce the wave reflection from and wave forces acting on the structures. Considering the similarity between the compartment of perforated caisson and the air chamber of OWC wave energy convertor, a new perforated caisson of breakwater is designed in this paper. The ordinary caisson is modified by installing facilities similar to the air chamber of OWC convener, but here they are utilized to dissipate the wave energy inside the caisson. Such an arrangement improves the stability of the caisson and reduces the construction cost by using the compartment of perforated caisson like using an air chamber. This innovation has both academic significance and important engineering value. For a new type of caisson, reliability analysis of the structure is necessary. Linear potential flow theory is applied to calculate the horizontal wave force acting on the caisson. The calculated results are compared with experimental data, showing the feasibility of the method. The Importance Sampling Procedure(ISP)is used to analyse the reliability of this caisson breakwater.     

Shear-flow induced secondary circulation in parallel underwater topographic corrugation and its application to satellite image interpretation

This study aims to figure out satellite imaging mechanisms for submerged sand ridges in the shallow water region in the case of the flow parallel to the topography corrugation.Solving the disturbance governing equations of the shear-flow yields the analytical solutions of the secondary circulation.The solutions indicate that a flow with a parabolic horizontal velocity shear and a sinusoidal vertical velocity shear will induce a pair of vortexes with opposite signs distributed symmetrically on the two sides of central line of a rectangular canal.In the case of the presence of surface Ekman layer with the direction of Ekman current opposite to(coincident with) the mean flow,the two vortexes converge(diverge) at the central line of canal in the upper layer and form a surface current convergent(divergent) zone along the central line of the canal.In the case of the absence of surface Ekman layer,there is no convergent(divergent) zone formed over the sea surface.The theoretical results are applied to interpretations of three convergent cases,one divergent case and statistics of 27 cases of satellite observations in the submerged sand ridge region of the Liaodong Shoal in the Bohai Sea.We found that the long,finger-like,bright patterns on SAR images are corresponding to the locations of the canals(or tidal channels) formed by two adjacent sand ridges rather than the sand ridges themselves.     

联合GPS与重力资料反演福建地区地壳运动

联合福建省近几年的GPS基本网、基准站观测数据和重力复测数据,反演福建块体的分块运动参数和主要活动断裂运动状态。结果显示,受欧亚板块、菲律宾海板块和太平洋板块相互碰撞的影响,福建地区块体的运动样式大体呈现顺时针方向的运动,造成北东向断裂作左旋走滑运动,而北西向断裂以右旋走滑为主。其中,长乐-诏安断裂带、邵武-河源断裂带和永安-晋江断裂带是块体内最活跃的断裂带,其左旋走滑速率分别为0.7±1.3、0.7±1.7和0.6±1.8mm/a,九龙江下游断裂带具有0.5±1.7mm/a的右旋走滑速率。     

Rock physics and seismic modeling of shale reservoirs with horizontal fractures

The presence of horizontal fractures enhances seismic anisotropy of shales.Calculation based on the effective medium theory indicates that horizontal fractures have little effects on velocities along the direction pa-rallel to fractures,but can significantly reduce velocities along the direction normal to fractures.Seismic respon-ses of shales with horizontal fractures are calculated based on the reflector model and the anisotropic propagator matrix method,in which the reflections are a combination of the contrast in impedance due to the variations in fracture density,anisotropic propagation of waves within the shales,and the tuning and interferences associated with layer thickness.Calculated results indicate that seismic reflections are sensitive to reservoir layer thickness and fracture density.Anisotropic propagation alters amplitudes and phases of reflections.It corresponds to high-er reflection amplitudes for the case of surrounding sandstone with higher velocity because the increase in frac-ture density increases the contrast in impedance between the shale and sandstone.In contrast,the surrounding sandstone with lower velocity corresponds to lower reflection amplitudes for the increase in fracture density.     

Taxonomic Studies on a New Marine Ciliate, Apocoleps magnus gen. nov., spec. nov. （Ciliophora, Colepidae）, Isolated from Qingdao, China

The morphology and infraciliature of a new marine colepid ciliate, Apocoleps magnus gen. nov., spec. nov., are described based on living observations and silver impregnations. The new genus Apocoleps is characterized by having 8 (vs. 6 in most other related genera) armour tiers, spines at both ends of the cell, 3 adoral organelles and plates with 4 reniform uni-windows. Apocoleps magnus spec. nov. is defined by the following features: body elongated and slightly curved, about 100–120μm× 35–45 μm in vivo; an...     

现今绝对板块运动

根据热点假设,热点对于中间层是固定的.相对热点的板块运动叫做绝对板块运动.绝对板块运动模型可以通过反演火山链传播的速率和走向数据以确定相对板块运动在角速度空间的原点来得到.利用一组近来(0～7.8 Ma)全球分布的热点的迁移速率和走向数据,结合板块运动模型NNR-NUVEL1A,已研制出一个叫做APM2的现今绝对板块运动模型.按照该模型,太平洋板块围绕60.063°S、102.210°E处的极以(0.833 0°±0.013 3°)/Ma的速率运动,非洲板块围绕46.849°N、44.372°W的极以(0.101 5°±0.013 4°)/Ma的速率运动,南极板块的运动则以46.871°N、146.942°E为极,速率为(0.084 6°±0.017 7°)/Ma,欧亚板块的运动更慢,极为27.291°N、171.925°W,速率为(0.065 5°±0.020 6°)/Ma.这一模型表明,岩石圈相对深部地幔有一个以49.423°S、90.625°E为极,速率为(0.198 3°±0.013 5°)/Ma的净旋转.表明太平洋热点同印度-大西洋热点不一致,显示太平洋热点的运动也不一致.为了分析和比较,还给出了仅用全球分布的热点的走向数据和仅用印度-大西洋热点的走向数据得到的板块绝对运动的角速度.     

确定板块运动学模型的台站选取

国际地球参考架(ITRF)和板块运动模型的台站选取标准都具有随意性，直接影响地球参考架和板块运动模型的精度和可信度。提出了一种确定刚体板块内台站的新方法，即从ITRF2000速度场利用7参数转换得到的各台站运动速度残差，使其向刚性板块运动逼近，通过多次循环，从而确定各板块的刚性台站，可更好地定向地球参考架和建立高精度板块运动模型。     

Crustal deformation revealed by GPS in Kumaun Himalaya,India

The foremost Global Positioning System(GPS) derived measurements in the Kumaun Himalaya indicate that most of the crustal motion of the Indian plate is accommodating towards the base as well as on the hanging wall of Main Central Thrust(MCT).Deformation pattern within the Kumaun Himalaya varies from south to north and indicates maximum deformation rate near MCT.Our study,based on the campaign mode GPS survey during 2003- 2006,reveals that the area between north of North Almora Thrust(NAT) and at the base of Great Himalaya registers maximum strain rate,which is lowered towards the Trans Himadri Fault(THF).The GAMIT-GLOBK processed campaign data of the area show that currently,the Himalayan Frontal Fault(HFF) and Main Boundary Thrust(MBT) are locked with the Indian plate,and a 6.7 ± 2.5 mm/yr of horizontal shortening is taking place between the Lesser Himalaya and Peninsular India.