Wave Forces on Submerged Semi-Circular Breakwater and Similar Structures

The results of design and experiment of a submerged semi-circular breakwater at the Yangtze estuary show that the submerged structure will be unsafe when the general empirical wave force formula for semi-circular breakwater is used in design. Therefore, a new calculation method for the wave forces acting on a submerged semi-circular structure is given in this paper, in which the wave force acting on the inside circumference of semi-circular arch is included, and the phase modification coefficient in the general empirical formula is adjusted as well. The new wave force calculation method has been Verified by the results of seven related physical model tests and adopted in the design of the south esturary jetty of the first stage project of Deep Channel Improvement Project of the Yangtze River Estuary, the total jetty length being 17.5 km.

Effects of fundamental structure parameters on dynamic responses of submerged floating tunnel under hydrodynamic loads

This paper investigates the effects of structure parameters on dynamic responses of submerged floating tunnel （SFT） under hydrodynamic loads. The structure parameters includes buoyancy-weight ratio （BWR）, stiffness coefficients of the cable systems, tunnel net buoyancy and tunnel length. First, the importance of structural damp in relation to the dynamic responses of SPT is demonstrated and the mechanism of structural damp effect is discussed. Thereafter, the fundamental structure parameters are investigated through the analysis of SFT dynamic responses under hydrodynamic loads. The results indicate that the BWR of SFT is a key structure parameter. When BWR is 1.2, there is a remarkable trend change in the vertical dynamic response of SFT under hydrodynamic loads. The results also indicate that the ratio of the tunnel net buoyancy to the cable stiffness coefficient is not a characteristic factor affecting the dynamic responses of SFT under hydrodynamic loads.

Interface microstructure and properties of submerged arc brazing tin-based babbit

The submerged arc brazing method was used to connect the tin-based babbit alloy with the steel matrix.The microstructure of the submerged arc brazed Babbitt interface layer on the surface of Q235 B steel was analyzed by OM,SEM and EDS and the hardness properties of the joint interface layer were tested by MH-5 microhardness tester.the result of research shows that a layer of canine-shaped intermetallic compound with uneven thickness is formed at the interface,and the thickness is 10-20 μm.The interface layer includes two kinds of compound layers,namely the Fe Sn layer near the side of the steel substrate and FeSn layer near the side of the babbit.During the interfacial reaction process,Fe atoms in the steel matrix dissolve into the liquid babbit alloy and form a certain concentration gradient at the interface.The farther from the interface,the lower the Fe atom concentration.The growth of Gibbs free energy of Fe Sn is lower when the temperature is above 780.15 K,and the temperature during the welding process is much higher than 780.15 K,moreover the precipitation temperature of Fe Sn is higher.Therefore,in the subsequent cooling process,Fe Sn is first precipitated from the interface near the side of steel matrix and then FeSn is precipitated from the interface near the side of babbit alloy.Microhardness test showed that the intermetallic compound at the interface layer significantly improved the hardness properties.

Wave reflection, transmission and harmonics due to different submerged structures

Comparisons of wave reflection, transmission and harmonics due to different types of sub merged structures are investigated by a numerical method, the boundary-fitted coordinate (BFC) method. The types of submerged structures include a submerged horizontal plate, submerged breakwa ters (rectangular and trapezoidal) and a step-type structure (topography). First, the BFC method is ver ified by comparing the computed results with the experimental data, including wave surface elevations, reflected and transmitted wave heights, and amplitudes of higher harmonics, showing that the method is a reasonable one to predict wave deformations due to the submerged structures. Secondly, the wave sur face elevations and the higher harmonics over different submerged structures are compared. Thirdly, re flected and transmitted waves due to different submerged structures are investigated.

Wavemotionsarounddifferentsubmergedstructures

Wave motions around different types of submerged structures are investigated by a numerical method, theboundary fitted coordinate method. The types of submerged structures include a submerged horizontal plate, submerged breakwaters (rectangular and trapezoidal) and a step-type structure (topography) . Water level fluctuations, wave height distributions, velocity fields and wave energies around submerged structures are studied comprehensively.

ANALYSIS OF DYNAMIC STABILITY OF SUBMERGED STRUCTURE

The submerged structure is basically a large three-dimensional structure of few statically redundant members. The structure is subjected to vertical dead and live loads in addition to the wave forces. An analysis of dynamic stability of the submerged structure without damping has been made by J. Thomas and Abbas (1980). In this paper the analyses of dynamic stability of the sumberged structure with damping are conducted. The case structure with damping is more complicated 'than the case without it. According to the principle of perturbation, a new model for dynamic stability calculation in consideration of damping effect is developed. In this paper, the formulas are deduced, the computational program is compiled, the practical examples are analysed, and this problem is solved very satisfactorily. The computational results show that the shape and value of the regions of dynamic instability can be changed significantly by damping. So only by considering damping can the property of dynamic stability of the submerged structure be reflected correctly.

Simulation on the Conductivity of Charging Stock with Percolation Structure in the Submerged Arc Furnace

Based on the fractal geometry, a new way for selecting material burden ratio and size distribution, named physical design of burden, which is different from stoichiometric weight of carbon burden, would play a more important role in the operation of submerged arc furnace process. Cold simulation investigation was carried out to find how the fraction and size of metal balls affects the specific conductivity of charge mixture, by applying the percolation structure theory. A parameter equation, s/s=A(F-Fc)v, was suggested to calculate the specific conductivity of the charge mixture.

DYNAMIC CHARACTERISTIC ANALYSIS OF A 3-D SEMI-SUBMERGED BODY AS A FLUID-STRUCTURE INTERACTION SYSTEM

An Arnoldi's method with new iteration pattern,which was designed for solving a large unsymmetric eigenvalue problem introduced by displacement-pressure FE (Finite Element) pattern of a fluid-structure interaction system,was adopted here to get the dynamic characteristics of the semi-submerged body. The new iteration pattern could be used efficiently to obtain the Arnoldi's vectors in the shift-frequency technique,which was used for the zero-frequency problem. Numerical example showed that the fluid-structure interaction is one of the important factors to the dynamic characteristics of large semi-submerged thin-walled structures.

Fluid-structure interaction simulation for multi-body flexible morphing structures

The multi-body flexible morphing airfoil can improve the aerodynamic characteristics based on different flight missions continuously.Recently researches have focused on the unsteady aerodynamic characteristics of flexible wings under passive actuation.However,the unsteady aerodynamic characteristics with the fluid-structure interaction effects in the multi-body active actuation process of morphing airfoil deserve further investigation.In this paper,a fluid-structure coupled simulation method for multi-body flexible morphing airfoil with active actuation subsystem was investigated,and the aerodynamic characteristics during deformation were compared with different skin flexibility,flow field environment,actuation mode and actuation time.The numerical results show that for the steady aerodynamic,the skin flexibility can improve the stability efficiency.In the unsteady process,the change trend of the transient lift coefficient and pitching moment are consistent with those of the active drive characteristics,while the instantaneous lift-drag ratio coefficient is greatly affected by the driving mode and can be improved by increasing the driving duration.

The wave motion over a submerged Jarlan-type perforated breakwater

The wave motion over a submerged larlan-type breakwater consisting of a perforated front wall and a solid rear wall was investigated analytically and experimentally. An analytical solution was developed using matched eigenfunction expansions. The analytical solution was confirmed by previously known solutions for single and double submerged solid vertical plates, a multidomain boundary element method solution, and experimental data. The calculated results by the analytical solution showed that compared with double submerged vertical plates, the submerged Jarlan-type perforated breakwater had better wave-absorbing performance and lower wave forces. For engineering designs, the optimum values of the front wall porosity, relative submerged depth of the breakwater, and relative chamber width between front and rear walls were 0.1-0.2, 0.1-0.2, and 0.3-0.4, respectively. Interchanging the perforated front wall and solid rear wail may have no effect on the transmission coefficient. However, the present breakwater with a seaside perforated wall had a lower reflection coefficient.

Structure Design of SEN for High Efficiency Thin Slab Continuous Casting

Four-hole submerged entry nozzles （SEN） with dif- ferent structures were researched using the water simula- tion test by particle image velocimetry （PIV） and DJSO0 hydraulic measurement system to get suitable SEN for high efficiency continuous casting. The influences of the exit area ratio （2： 1：2, 3：2： 3, 1： 1：1 and 1：2： 1）, upper guide island angle θ （20°, 40°, 60° and 80°） , and lower guide island angle α （60°, 80°, 100° and 120°） on the vortex position in the mold and fluctuations were researched. The results show that the exit area ratio and the upper and low guide island angles have ob- vious influence on the flow field; the flow field in the mold is suitable at 1：2：1 of the exit area ratio, 80° of upper guide island angle, and 100° of lower guide island angle.

Metallographic structure analysis of DC pulsed SAW joint

Submerged arc welding （SAW） has shortcoming of over heat input, which increases grain size in heat-affected zone （ HAZ） and decreases welding quality and mechanical properties of the joints serioasly. With improvements of welding equipment, direct current （ DC） pulsed SAW （ PSAW） was utilized successfully in the research. Comparing DC PSAW with DC common SAW （ CSAW） , the metallographic structure was analyzed with optical and electron microscope, the width of HAZ was measured as well as the width and hardness of the coarse grained HAZ （CGHAZ）. The research shows that DC PSAW joint had higher welding penetration, narrower HAZ and CGHAZ, which benefited HAZ performance and welding quality.

Wave Scattering by a Submerged Sphere in Three-Layer Fluid

Using linear water wave theory,three-dimensional problems concerning the interaction of waves with spherical structures in a fluid which contains a three-layer fluid consisting of a layer of finite depth bounded above by freshwater of finite depth with free surface and below by an infinite layer of water of greater density are considered.In such a situation timeharmonic waves with a given frequency can propagate with three wavenumbers.The sphere is submerged in either of the three layers.Each problem is reduced to an infinite system of linear equations by employing the method of multipoles and the system of equations is solved numerically by standard technique.The hydrodynamic forces(vertical and horizontal forces)are obtained and depicted graphically against the wavenumber.When the density ratio of the upper and middle layer is made to approximately one,curves for vertical and horizontal forces almost coincide with the corresponding curves for the case of a two-layer fluid with a free surface.This means that in the limit,the density ratio of the upper and middle layer goes to approximately one,the solution agrees with the solution for the case of a two-layer fluid with a free surface.

Experimental Study of the Effects of Submerged Dikes on the Energy and Momentum Coefficients in Compound Channel

This paper aims to understand the flow structure around submerged dike in the main channel and flood plain of a compound cross section. The study undertaken to develop this understanding was carried out in a laboratory flume using a submerged vane installed at a 90 degree angle to the bank. In order to study the flow structures, the flow velocity was measured using a three-dimensional Acoustic Doppler Velocity meter (micro-ADV) with data collection rate of 50 Hz. These flow velocity measurements were taken at 500 points on a regular grid. As the tests were undertaken with turbulent flow, these conditions were subcritical. Furthermore, all the tests were undertaken using a fixed bed. The results obtained showed that the momentum transfer and the kinetic energy reduced in two directions. Also the energy and momentum coefficients decreased significantly with the installation of the submerged vane inside the main channel. Finally, streamlines were found to deviate from the side walls of channel into the main channel.

Mechanical Behaviors of Submerged Floating Tunnel under Current Effect

In order to provide a technical reference and guidance for the safety and stability analysis of the submerged floating tunnel （SFT） in the future, the mechanical behaviors of SFT under the action of water current with different velocities were studied by experiments on an SFT tube model made of rubber. Then, a numerical simulation on the coupling interaction between SFT and water current was conducted by finite element method （FEM）. The comparison .between the results obtained from experiment and those derived from the numerical simulation shows that the experimental results approximately tally with the simulational ones. As a result, the relationships between water current velocities and the mechanical behaviors of tube, such as the annular and axial strains, internal forces （ axial force and bending moment）, and deformations of the tube structure and the forces borne by the tension cables, were concluded.

苏北高邮湖菹草(Potamogeton crispus)生长衰亡过程对水质与浮游植物群落的影响

为探究菹草(Potamogeton crispus)生长、衰亡期对生态环境的效应,本文以南水北调东线源头调蓄湖泊——高邮湖为研究区域,通过分析湖泊水质及浮游植物群落随菹草生长衰亡过程的变化情况,揭示高邮湖菹草暴发下水环境状况变化。结果表明:在菹草生长期水体透明度明显提高,且总氮浓度有较大程度的下降;而在菹草衰亡期,菹草生物量越高的区域水质越差。菹草在生长期对水环境起到一定的净化效果,而菹草衰亡降解会造成水质恶化。菹草生长期浮游植物密度和生物量显著低于衰亡期,生长期菹草高、中生物量区的浮游植物密度和生物量低于低生物量区,而在菹草衰亡期高、中生物量区的浮游植物密度和生物量高于低生物量区。冗余分析结果表明,pH、溶解氧、氨氮、硝态氮、总磷、高锰酸盐指数是菹草生长衰亡过程影响浮游植物群落结构的主要环境因子。分段结构方程模型模拟结果表明,菹草生物量可对浮游植物生物量产生直接效应,也可以通过改变环境因子对浮游植物生物量产生间接效应。

固体发动机喷管热结构耦合数值仿真研究

针对在热载荷与内压联合作用下,固体火箭发动机潜入式喷管的热结构耦合数值仿真问题,采用流体仿真软件与结构计算软件,展开了数值模拟。在流体仿真软件中,计算了潜入式喷管工作过程的内部稳态流场,提取了高温燃气流动参数与固体壁面对流换热系数。在有限元结构计算平台内,编写了非均布壁面压力载荷与非均布对流换热系数子程序,耦合求解了喷管热结构耦合问题,获取了热防护材料内部温度场与应力场分布。研究表明,热载荷是引起喉衬应力的主要原因。喉衬环向压应力与拉应力随时间呈现先增大后减小的过程。经地面喷管结构完整性热试车试验验证,该热结构耦合数值仿真方法可用于喷管结构完整性与安全性分析,为喷管结构设计提供合理指导。

基于潜层关系增强的实体和关系联合抽取

为充分发掘文本序列中潜层语义关系信息,提出一种实体和关系联合抽取的潜层关系增强模型SREM(text subtext relationship enhancement model)。在潜层关系表示层利用结构化对齐的方式,获取并保持文本序列中的语义信息结构。在融合注意力机制的关系网络层中对数据进行建模,提高模型对文本词汇间关系信息的捕获能力。结合注意力机制获取细粒度语义信息,对上下文信息进行选择过滤。实验结果表明,在数据集NYT和WebNLG上取得的F1值分别为92.40%和92.52%,验证了模型的有效性。

淹没水射流式贝肉清洗装置设计与试验

随着贝类预制菜产业的发展,基于贝肉的精加工预制食品逐渐在市场上推广,虽然市场上清洗装置品类较多,但是尚未有适合各类贝肉产品清洗的装备,存在清洗效率低、洗净率差和易破损等问题。本研究基于淹没水射流机理,设计了以淹没水射流为清洗动力的贝肉清洗装置,并对清洗装置进行Fluent-EDEM耦合数值模拟,确定清洗装置的关键结构参数范围。通过2个阶段试验论证了该清洗装置的合理性,第1阶段通过清洗正交试验得出,当射流口直径为10 mm,清洗量为14 kg,清洗时间为6 min,淹没水射流式清洗效果最佳;第2阶段进行了生产性对比试验,并以洗净率和破损率作为评价指标,对比3种清洗装置洗净率。结果显示:以扇贝裙边为清洗对象时,淹没水射流式清洗装置的平均洗净率为97.77%,且无破损现象,较螺旋桨式清洗装置洗净率提高了14.4%,较超声波式清洗装置洗净率提高了7.3%;以鸟蛤肉为清洗对象时,淹没水射流式清洗装置的平均洗净率为98.23%,较螺旋桨式清洗装置的洗净率提高了12.49%,较超声波式清洗装置洗净率提高了6.7%,且无破损情况。研究表明,淹没水射流式装置具有较好的清洗效果,具备产业化推广价值。

耐候钢Q370qENH埋弧焊焊接接头锈蚀行为与机理研究

为了研究耐候钢Q370qENH埋弧焊材的锈蚀机理,对Q370qENH埋弧焊焊缝试样和基材试样进行浸泡腐蚀实验和电化学腐蚀实验,并对Q370qENH浸泡腐蚀后形成的锈层形貌和成分进行表征。结果表明,Q370qENH埋弧焊焊材焊缝处的耐蚀能力低于基材,其电化学阻抗为基材的38%。分析了Q370qENH埋弧焊材焊缝耐蚀能力低于基材的原因和表面锈层的形成机理,研究结果可为耐候钢在高速铁路钢桥等工程项目中的服役安全评估和维修养护提供科学依据和理论基础。