基于不可压缩粘性流对板状结构的稳定性分析

基于粘性流理论考虑结构-流体的耦合效应,研究四跨简支板状梁在轴向流作用下的振动及其稳定性.采用假设模态法建立刚性水槽内多跨板状梁结构在轴向流体中的运动微分方程,分析系统的颤振临界流速随间隙和板厚的变化规律.结果表明:四跨简支板状梁在轴向二维粘性流中发生颤振失稳;在本文参数下,系统的颤振临界流速随水槽内间隙的增大而降低,随板状梁厚度的增大而提高.     

压水堆燃料组件附加质量仿真研究

为了准确探究反应堆冷却剂与燃料组件间存在流固耦合行为对燃料组件振动特性的影响,本文采用计算流体动力学（CFD）软件Fluent平台,运用其中的动态网格技术,以压水堆燃料组件为研究对象,通过建立燃料组件模拟棒束、堆芯围板以及冷却剂模型,实现燃料组件与堆芯围板分别单独运动工况的燃料组件附加质量计算。结果显示：燃料组件运动工况下,燃料组件附加质量系数均值为2.4712;围板运动工况下,燃料组件附加质量系数均值为–3.4713,均与文献值偏差小于5%。叠加附加质量后,燃料组件振动频率计算值与水中振动试验测试结果偏差小于5%,验证了分析方法的合理性。本研究建立的仿真计算方法能够用于压水堆燃料组件附加质量计算。     

蒸汽发生器传热管固有振动试验和分析研究

通过蒸汽发生器管束模拟体试验,测定了不同弯头半径的传热管固有频率和振型。研究了间隙、支撑板梅花孔、弯头半径等因素对传热管固有频率的影响。分别测量了无耦合效应的面内对称、反对称和面外对称、反对称四种振型的固有频率,并通过单跨和两跨连续直梁固有振动试验确定了面内振动时弯头处的弹簧系数。前12阶固有频率的试验值和计算值符合得较好。试验表明:以结构固有频率激振时,间隙效应使传热管响应谱的频带变宽,但其中激振频率成分仍占优势。     

窄间隙流固耦合结构抗震分析流程规范化研究

对于窄间隙流固耦合效应,采用简化方法得到附加质量和地震激励修正系数。在乏燃料贮存格架的抗震分析中,对其分析流程进行规范化,即在考虑流体附加质量的同时,也对地震激励进行修正,从而得到乏燃料贮存格架在地震载荷下的力学响应。在此研究基础上可以进一步建立窄间隙流固耦合结构抗震分析标准。     

悬臂管在同心套管包围的水中振动特性的研究

对悬臂管在同心套管包围的水中的振动特性作了分析。通过求解二维线性Navier—Stokes方程,得出了计算附加质量系数和粘滞阻尼比的公式。为了验证理论分析结果,对悬臂管在同心套管包围的水中的附加质量系数和粘滞阻尼进行了实验研究。得出了附加质量系数和粘滞阻尼比与套管内径和悬臂管外径之比、悬臂管在同心套管包围的水中振动的固有频率以及Stokes数之间的关系。     

核电厂地坑过滤器附加质量试验研究

采用测量转动惯量的方法对核电厂安全壳地坑过滤器水下附加质量进行测量,分别测量了圆柱、圆筒、双层圆筒、圆筒形地坑过滤器4种结构。将圆柱的附加质量测量值与在理想流体中的理论值进行对比,验证了该方法可以比较准确地测量附加质量。结果分析表明,附加质量不随激振频率变化,圆筒结构附加质量为圆柱结构的1.9倍,双层圆筒附加质量与单层圆筒差异不大;地坑过滤器由于表面开孔附加质量较圆筒结构降低70%;地坑过滤器附加质量与本身质量的值为同一数量级,地坑过滤器设计时不能忽略附加质量。     

采用变化附加阻尼的快堆堆芯组件抗震分析方法的研究

对快堆堆芯组件进行的抗震分析需要考虑冷却剂与堆芯组件之间的流固耦合作用。在之前的分析中,大多数人将流体附加阻尼处理为定值。实际上冷却剂对组件的作用还随着组件间的间隙变化而变化,其带来的附加阻尼应为变量。为更准确地模拟堆芯组件的振动,本文采用变化附加阻尼对快堆堆芯组件的抗震分析方法进行了研究。建立了快堆堆芯单排（5根）堆芯组件的抗震分析计算模型,对该模型进行了附加阻尼为定值和随间隙变化两种情况下的抗震分析,结果显示了考虑变化附加阻尼的堆芯组件抗震分析方法的可行性与有效性。本文所使用的模拟方法更为贴近堆芯组件的振动情况,为更为真实地模拟快堆堆芯组件的地震响应打下基础,这也有助于减少结构设计的保守性,具有一定的工程价值。     

一种质谱数据处理方法的扩充及程序化

在质谱分析稳定同位素标记化合物时,由于在某些标记物(特别是某一特定同位素的多标记物)上存在附加质子碎片,因而可导致测试误差增大。针对标记物中有多位标记的情况(如存在三、四、五、六位标记的分子),我们推导了多组实系数高次方程,求出实际标记的丰度;消除了附加质子碎片带来的误差。同时,将推导出的算法在PDP11/79计算机上用FORTRAN-77语言实现了程序化,使计算工作方便地进行。     

吊篮流致振动响应的数值计算

将流体和结构作用力分成与结构运动有关的流体作用力和与结构运动无关的作用力.与结构运动有关的流体力可以看成与结构惯性力、阻尼力和刚度力呈线性关系,并分别用附加质量、附加阻尼和附加刚度与结构的加速度、速度和位移的乘积表示;通常,附加阻尼、附加刚度比较小,可以忽略不计,主要考虑附加质量.与结构运动无关的流体作用力用CFD技术计算流场压力获得.最后用时程积分计算结构的响应.用该方法对秦山核电站二期1:5模型的吊篮进行计算,结果表明,对于流体产生的宽带激励,结构以其固有频率进行响应,主要以吊篮的一阶梁式频率作为响应的频率;实验和计算的响应统汁值保持在3.1倍范围内.因此,该方法可用于实验前的预估.     

振动条件下平行孔板间流体的作用力实验

乏燃料贮存格架自由放置在乏燃料水池内,格架 格架、格架 池壁之间有一定间隙。在地震载荷下,这些间隙中流体的流固耦合作用耗散了结构的能量,保证了格架的结构完整性。根据AP1000和CAP1400系列反应堆型的格架储存腔设计,格架的侧壁有平板或孔板两种方案。对格架进行结构动力学分析时,为了简化流体间隙附加质量的计算,工程上一般将孔板直接简化为平板。这样的方法并不能精确反映出实际的流固耦合效应。为获得格架与格架、格架与池壁间流体的流固耦合特性,搭建实验台架,通过振动实验,测量孔板的间隙流体在不同激振频率、不同间隙条件下的流体作用力。实验最终给出孔板的间隙流体的流体力,并给出了不同间隙条件下附加质量,本文可为AP1000和CAP1400系列乏燃料储存格架的流固耦合参数选取提供依据。     

基于铁摩辛柯梁理论的管道最大跨距分析

传统的管道跨距计算方法是基于欧拉梁理论的简支梁模型，该计算方法仅仅考虑横截面的弯曲变形，忽略剪切变形影响。本文以铁摩辛柯梁理论的简支梁为计算模型，给出考虑剪切变形的管道最大跨距理论计算公式。通过该公式可知，对于DN200及以下的管道，基于欧拉梁理论与铁摩辛柯梁理论求解的管道最大跨距相差小于1%；但对于DN200以上的管道，则基于铁摩辛柯梁理论得到的管道最大跨距小于基于欧拉梁理论得到的管道最大跨距，而且管道外径越大，管道最大跨距相差越大。因此对于DN200以上的管道，建议采用基于铁摩辛柯梁理论求解的公式计算管道最大跨距。      

镱同位素电磁分离束流接收与监测系统研制

镱同位素在放射性药物、原子钟、核物理等领域具有重要应用。电磁法是目前可用于分离镱同位素的最佳选择,为了收集和监测电磁法分离后的镱同位素,本文研制了镱同位素束流接收与监测系统。针对镱同位素分离色散小、数目多、不易分离的特点,通过理论计算和经验参数,设计多缝面板、内置水冷结构的模块化收集器和束流监测系统,减少同位素的蒸发和溅射,提高镱同位素的丰度。最终完成镱同位素束流接收与监测系统测试,目前该系统已经应用于镱同位素的分离,镱-176同位素丰度达到96.9%。     

乏燃料贮存格架流固耦合参数的数值模拟

乏燃料贮存格架是储存乏燃料组件的重要设备。在地震载荷下,其响应是非线性的,可能产生滑移、颠覆等。发生地震时,存在于格架间隙内的流体耗散了结构的能量,保证了格架的完整性。本文使用3/10缩比模型,利用CFD软件Fluent进行了乏燃料贮存格架2D瞬态分析。计算过程中利用动网格方法模拟格架强迫振动,并进行了参数不确定性分析。利用CFD瞬态流体力分别获得了双Ⅱ区、双Ⅰ区格架附加质量矩阵。利用同轴圆柱体附加质量的计算解与解析解进行对比验证,证明了本文计算方法的准确性。本文计算所得的附加质量矩阵可为乏燃料贮存格架结构动态软件提供流固耦合参数。     

Free vibration analysis of multi-span pipe conveying fluid with dynamic stiffness method

By taking a pipe as Timoshenko beam, in this paper the original 4-equation model of pipe conveying fluid was modified by taking the dynamic effects of fluid into account. The shape function that always used in the finite element method was replaced by the exact wave solution of the modified four equations. And then the dynamic stiffness was deduced for the free vibration of pipe conveying fluid. The proposed method was validated by comparing the results of critical velocity with analytical solution for a simply supported pipe at both ends. In the example, the proposed method was applied to calculate the first three natural frequencies of a three span pipe with twelve meters long in three different cases. The results of natural frequency for the pipe conveying stationary fluid fitted well with that calculated by finite element software Abaqus. It was shown that the dynamic stiffness method can still hold high precision even though the element's size was quite large. And this is the predominant advantage of the proposed method comparing with conventional finite element method.     

Fluid-structure interaction in non-rigid pipeline systems

Fluid-structure interaction in non-rigid pipeline systems is modelled by water hammer theory for the fluid coupled with beam theory for the pipe. Two different beam theories and two different solution methods in the time domain are studied and compared. In the first method, the fluid equations are solved by the method of characteristics and the pipe equations are solved by the finite element method in combination with a direct time integration scheme. In the second method, all basic equations (fluid and pipe) are solved by the method of characteristics. The solution methods are applied to a straight pipeline system subjected to axial and lateral impact loads and to a one-elbow pipeline system subjected to a rapid valve closure. In comparing the beam theories, the effects of rotatory inertia and shear deformation for practical pipe geometries and loading conditions are investigated. The significance of fluid-structure interaction is demonstrated. The fluid-structure interaction computer code , developed by and which solves the acoustic equations using the method of characteristics (fluid) and the finite element method (structure), enables the user to determine dynamic fluid pressures, structural stresses and displacements in a liquid filled pipeline system under transient conditions. To validate , experiments are performed in a large scale 3D test facility consisting of a steel pipeline system suspended by wires. Pressure surges are generated by a fast acting shut-off valve. Dynamic pressures, structural displacements and strains (in total 70 signals) are measured under well determined initial and boundary conditions. The experiments are simulated with . The agreement between experiments and simulations is shown to be good: frequencies, amplitudes and wave phenomena are well predicted by the numerical simulations. It is demonstrated that the results obtained from a classical uncoupled water hammer computation, would render completely unreliable and useless results.     

某高温气冷堆示范工程大跨单侧钢板混凝土组合梁受力机理研究

对某高温气冷堆示范工程大跨单侧钢板混凝土（HSC）组合屋盖中的一榀主梁进行缩尺静载试验研究,分析加载过程中试件的挠度、应变和裂缝的发展,研究了此类构件的受力特点和破坏形态。建立了HSC组合梁试件的有限元模型并进行分析,结果表明极限荷载作用下试验和模拟得到的跨中最大挠度基本一致,梁侧腹板下部混凝土表面最先出现微小裂缝,该类型构件中的钢板和钢筋混凝土可有效地形成组合截面共同工作,整个构件具有较高的承载力和延性性能。本文结论可作为核电厂单侧钢板混凝土组合梁初步设计和动力分析的参考。     

Diagnosis and dynamics in a simple low energy medium current electron beam channel

We present a simple experimental setup and an associated method enabling both the non-destructive diagnosis and the calculation of the beam evolution in a low energy medium current electron beam channel, where the space-charge and emittance effects are comparable. The diagnosis makes use of an axially symmetric magnetic lens while a second lens is added to increase the flexibility in the beam processing. The paper emphasizes the three steps involved in the method: the evaluation of the lenses' magnetic field by numerical simulation, the beam diagnosis, and the computation of the beam envelope. The calculation of the magnetic field is based on the finite element method. Subsequently, the beam parameters at the electron source exit – emittance and cross-over radius and position – are found with the modified three gradient method. Finally, the beam dynamics are modeled with the K–V equation adapted for the particular case of axial symmetry. The results obtained in this paper can be used to optimize technological processes, such as welding, hardening, cladding, and surface alloying.     

Experiment and analysis of shell model in-water frequencies of a 1/24th-scale core barrel model

Natural frequencies of a 1/24th-scale core barrel/vessel model in air and in water are measured by determining frequency responses to applied forces. The measured data are analyzed by the use of the one-dimensional fluid-structure computer code, MULTIFLEX, developed to calculate the hydraulic force. The fluid-structure interaction in the downcomer annulus is computed with a one-dimensional network model formed to be equivalent to two-dimensional fluid-structure interaction. The structural model incorporated in MULTIFLEX is substantially simpler than that necessary for structural analyses. Proposed for computation of structural dynamics is the projector method that can deal with the beam mode by modal analysis and the other shell modes by a direct integration method. Computed in-air and in-water frequencies agree fairly well with the experimental data, verifying the above MULTIFLEX technique.