Review of numerical simulation on the dynamics of Qinghai-Xizang plateau

In recent twenty years, much numerical simulation work has been done on the evolution of Qinghai-Xizang (Tibetan) plateau. In this paper some principal numerical models and results are reviewed and analyzed. The earlier plane stress or plane strain model has much discrepancy with the actual deformation of Qinghai-Xizang plateau, such as the thickening of Tibetan crust and the lateral extrusion of Tibet along strike-slip faults. The thin viscous sheet model and the thin-plate model may simulate the change of the crustal thickness and the deformation pro-duced by gravitational force. It is suitable for studying the large-scale and long-time deformation. The influence of faults on the deformation of Tibetan plateau should be further studied.

Review of numerical simulation on the dy-namics of Qinghai-Xizang plateau

In recent twenty years, much numerical simulation work has been done on the evolution of Qinghai-Xizang (Tibetan) plateau. In this paper some principal numerical models and results are reviewed and analyzed. The earlier plane stress or plane strain model has much discrepancy with the actual deformation of Qinghai-Xizang plateau, such as the thickening of Tibetan crust and the lateral extrusion of Tibet along strike-slip faults. The thin viscous sheet model and the thin-plate model may simulate the change of the crustal thickness and the deformation pro-duced by gravitational force. It is suitable for studying the large-scale and long-time deformation. The influence of faults on the deformation of Tibetan plateau should be further studied.

Microfluidic field strategy for enhancement and scale up of liquid-liquid homogeneous chemical processes by optimization of 3D spiral baffle structure

Due to the scale effect, the uniform distribution of reagents in continuous flow reactor becomes bad when the channel is enlarged to tens of millimeters. Microfluidic field strategy was proposed to produce high mixing efficiency in large-scale channel. A 3D spiral baffle structure(3SBS) was designed and optimized to form microfluidic field disturbed by continuous secondary flow in millimeter scale Y-shaped tube mixer(YSTM). Enhancement effect of the 3SBS in liquid-liquid homogeneous chemical processes was verified and evaluated through the combination of simulation and experiment. Compared with 1 mm YSTM, 10 mm YSTM with 3SBS increased the treatment capacity by 100 times, shortened the basic complete mixing time by 0.85 times, which proves the potential of microfluidic field strategy in enhancement and scale-up of liquid-liquid homogeneous chemical process.

Three-dimensional transient numerical simulation for gas exchange process in a four-stroke motorcycle engine

Three-dimensional transient numerical simulation of gas exchange process in a four-stroke motorcycle engine with a semi-spherical combustion chamber with two tilt valves was studied. Combination of the grid re-meshing method and the snapper technique made the valves move smoothly. The flow structure and pattern in a complete engine cycle were described in detail. Tumble ratios around the x-axis and y-axis were analyzed. Comparison of computed pressure with experimental pressure under motored condition revealed that the simulation had high calculation precision; CFD simulation can be regarded as an im-portant tool for resolving the complex aerodynamic behavior in motorcycle engines.

PHOTOINDUCED BIREFRINGENCE AND NUMERICAL SOLUTION OF A NEW DYNAMIC MODEL IN AN AMORPHOUS COPOLYMER CONTAINING AZOBENZENE GROUPS

Photoinduced birefringence is investigated in a new amorphous copolymer containing azobenzene groups. The levels of birefringence signal are found to depend an the polarization angle between the pump beam and the probe beam, and on the ellipticity of the pump beam. Both the growth and decay processes of the birefringence signal can be described by known biexponential equations. The rate constants and the amplitudes associated with the growth process of the photoinduced birefringence are observed to display a linear dependence with the pump beam intensity. A new dynamic model of the photoinduced birefringence is presented taking into account the contributions of both the bans and cis isomers of azobenzene groups and the local polymer segments. The numerical treatment of this model shows good agreement with the experimental data in the whole writing-erasing processes of the photoinduced birefringence conducted in our polymer samples.

Numerical investigations on dynamic process of muzzle flow

The integrative process of a quiescent projectile accelerated by high-pressure gas to shoot out at a supersonic speed and beyond the range of a precursor flow field was simulated numerically. The calculation was based on ALE equations and a second-order precision Roe method that adopted chimera grids and a dynamic mesh. From the predicted results, the coupling and interaction among the precursor flow field, propellant gas flow field and high-speed projectile were discussed in detail. The shock-vortex interaction, shockwave reflection, shock-projectile interaction with shock diffraction, and shock focus were clearly demonstrated to explain the effect on the acceleration of the projectile.

Numerical simulation for dynamical processes of seaice

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DYNAMIC MODEL AND SIMULATION OF THE PLATELETS'ROLE IN BLOOD COAGULATION

In order to confirm which process is the most important in the blood coagulation cascade,a dynamic model on the function of platelets in blood coagulation is presented based on biochemical experiments.Based on qualitative analysis and mathematical simulation,a series of conclusions about the influence of the activation rate of factor VIII and factor IX on the generation of thrombin(IIa)are drawn.It is evident that the pro-coagulation stimulus must exceed a threshold value to initiate the coagulation cascade.The value is related to the binding constant d_2 of the platelet. The stability of the equilibrium value is also related to the pro-coagulation stimulus. This article also evaluates the influence of the stimulus strength and the activated rate parameter of platelets on thrombin.The proportion of platelets activated at any given time is designated c.To each c,we obtain a maximum concentration of thrombin.It is evident that when the level of factor IX is below 1% of the normal level,the rate of thrombin generation reduces dramatically,resulting in severe bleeding tendency.

节流式燃/氧分离组合固体火箭发动机动态工作过程数值研究

利用商业软件ANSYS Fluent对节流式燃/氧分离组合固体火箭发动机动态工作过程进行数值研究,揭示该发动机基本动态工作过程以及节流阀作动速度的影响。结果表明,节流阀作动会导致发动机富氧燃烧室压强、节流阀出口质量流量以及发动机推力出现负调现象;节流阀作动速度差异不影响发动机调节后的稳定工作状态;随着节流阀作动速度增大,发动机达到稳定工作状态所需时间逐渐缩短,实现性能调控的响应速度增快,但发动机各参数负调量也随之增大,从而增加了发动机发生振动的风险。

两种直动式高速电磁阀数值模拟与动态响应对比分析

针对直动式高速电磁阀动铁芯与阀芯加工、装配工艺要求高,一致性较差的问题,提出了一种动铁芯与阀芯可分离的结构,基于AMESim平台建立此款电磁阀电–磁–机–气多物理场耦合模型,考虑了动铁芯与阀芯撞击与分离的情况,并在试验台上进行了验证。然后与另一种动铁芯与阀芯“绑定”的结构形式进行比较分析。结果表明:两种电磁阀在动态响应与影响动态响应的关键参数存在差别。在同等条件下,第一种结构形式的电磁阀动态响应整体略差,但是其对动铁芯–阀芯加工、装配工艺的要求较低。

抽水蓄能机组水轮机工况启动过程转轮动应力特性

本文以某原型水泵水轮机组为研究对象,研究了水轮机工况启动过程中外特性的动态变化曲线,重点分析水泵水轮机转轮内流场和动应力特性。研究结果表明,在水轮机工况启动过程中,转轮扭矩呈先上升后下降的趋势,在转速达到额定值时,扭矩接近于0;流量受到导叶开度的影响非常明显,处于先上升后下降趋势;水头在430~480m左右波动。随着转速的增加,转轮流固耦合面上的整体压力值显著增加。高压区起始集中在转轮进水边的压力面一侧,随着时间的推移,高压区域逐渐扩大并移动到进水边的吸力面一侧。转轮进水边与下环交接处的应力呈现先下降后上升的趋势,应力均值下降的同时,峰峰值也有所下降,应力值一直处于较低的水平。转轮进水边与上冠交接处的应力呈现上升趋势,并与转轮转速的变化趋势一致。本文对于深入理解水泵水轮机组启动过程复杂条件下的内部流动和转轮动应力特性具有重要参考价值。

Study on transient aerodynamic characteristics of parachute opening process

In the research of parachute, canopy inflation process modeling is one of the most complicated tasks. As canopy often experiences the largest deformations and loa-dings during a very short time, it is of great difficulty for theoretical analysis and experimental measurements. In this paper, aerodynamic equations and structural dynamics equations were developed for describing parachute opening process, and an iterative coupling solving strategy incorpo- rating the above equations was proposed for a small-scale, flexible and flat-circular parachute. Then, analyses were carried out for canopy geometry, time-dependent pressure difference between the inside and outside of the canopy, transient vortex around the canopy and the flow field in the radial plane as a sequence in opening process. The mechanism of the canopy shape development was explained from perspective of transient flow fields during the inflation process. Experiments of the parachute opening process were conducted in a wind tunnel, in which instantaneous shape of the canopy was measured by high velocity camera and the opening loading was measured by dynamometer balance. The theoretical predictions were found in good agreement with the experimental results, validating the proposed approach. This numerical method can improve the situation of strong dependence of parachute research on wind tunnel tests, and is of significance to the understanding of the mechanics of parachute inflation process.

鄱阳湖水利枢纽对江湖洪期水动力过程的影响

鄱阳湖作为通江湖泊,其洪水大小由多因素共同决定,湖区洪灾频繁。鄱阳湖水利枢纽工程建设后将对洪期复杂水动力过程造成影响。为评估其影响,建立了包括鄱阳湖湖区和尾闾以及长江九江到八里江段在内的平面二维水动力模型,对1954年大洪水和1991年倒灌2种灾害型洪期过程进行情景模拟,分析了枢纽对长江和湖区可能造成的影响。结果表明:枢纽工程使湖口出流过程更加平缓,具有一定的削峰作用,对长江洪水位基本无影响;1954年大洪水过程,枢纽使湖区水位升高,代表水文站水位壅高最大值为0.021 m;1991年倒灌过程,枢纽使湖区水位降低,湖区水位变化的趋势与湖口流量变化趋势一致,相位稍滞后于流量过程。研究成果可为江湖水安全管理提供技术支撑。

纤维类型和掺量对双丝拉拔试件动态性能的影响

基于各相材料的非均匀假设,采用动力有限元程序RFPA^(2D)-Dynamics建立了钢纤维、玻璃纤维和聚丙烯纤维三组双丝拉拔动态数值模型,研究动荷载下纤维类型和掺量对双丝拉拔试件力学性能的影响。从细观单元的弹性损伤本构关系出发,实现了双丝拉拔试件从微裂纹萌生、扩展直至贯通的动态破坏过程,得到不同双丝拉拔试件的破坏图、荷载-位移曲线和声发射累积能量曲线。结果表明,随着纤维体积掺量的增加,试件的整体耗能水平、抗裂性和延性逐渐提高,声发射总能量呈现先增大后减小的趋势,不同类型的纤维体积掺量存在一个最优掺量值。

舟曲江顶崖滑坡变形模式及发展趋势

以舟曲县江顶崖滑坡为依托,采用现场野外调查、工程地质钻孔勘探,全球导航卫星系统位移监测、无人机多期影像对比、变形历史对比、 Massflow数值模拟等方法获取滑坡变形的基本特征,分析滑坡复活机制、变形模式,再现其发展趋势及破坏范围.结果表明,江顶崖滑坡主要由降雨、江水冲刷诱发,降雨入渗在滑带处形成饱水带,软化、浸润滑面,导致滑带炭质板岩抗剪强度持续降低;江水冲蚀导致滑坡前缘失去支撑,最终诱发滑坡失稳;江顶崖滑坡拉裂滑动后后壁及侧壁出现“环状”灰黑色炭质板岩,中部形成洼地及平台,中前部出现多条鼓胀拉裂缝及剪切裂缝,前部形成多条放射状裂缝,滑体挤压白龙江河道,导致河道局部宽度不足5 m;江顶崖滑坡前部滑体滑动导致后部滑体失去支撑,加上后部滑体重力作用,导致局部复活,变形模式为前部牵引-后部推移的复合式破坏;数值模拟发现在不利工况下,滑坡堆积体将堵塞白龙江,形成18 m厚的堰塞体,并在滑坡上游形成6.6 km的回水淹没区,对上游南峪村、虎家崖村、安子坪村等村庄构成严重威胁,潜在危害大.

THE NUMERICAL SIMULATE OF THE UPLIFT PROCESS OF THE QINGHAI—TIBET PLATEAU

The quantitative analysis of uplift process of the Qinghai—Tibet plateau is a key to deepen the study of uplift mechanism and dynamic model, for this, numerical simulate was done to the whole process of uplift of the Qinghai—Tibet plateau.1 Geological model According to the tectonic evolution and lithospheric structure, continental crust in the Qinghai—Tibet plateau in profile is divided into sedimentary cover, crystalline rock formation and lower crust and composed of Kunlun, Bayan Har, Qiangtang, Gangdise and Himalaya blocks on the plane. Layer or block is bounded the detachment layer or large fault. On the basis of the uplift characteristics, the calculated time limit is in the Cenozoic since 65Ma, roughly four stages, i.e., 65 to 40Ma, 40 to 20Ma, 20 to 3Ma and 3Ma to now. Mesh profile used Yadong—Golmud Geoscience transect.

不同损伤模型下超高性能混凝土SHPB试验数值模拟对比

目的探讨不同损伤模型下超高性能混凝土SHPB试验数值模拟效果的差异性。方法应用大型有限元程序LS-DYNA,结合UHPC材料特性,明确了KCC、HJC和CSC模型中关键参数的取值,建立了超高性能混凝土SHPB试验数值仿真模型。在此基础上,开展不同损伤模型下UHPC试件波形、动态应力-应变曲线、弹性模量和动力增大系数(DIF)值模拟结果与实测结果的对比,探讨不同损伤模型下超高性能混凝土SHPB试验动态破坏进程。结果CSC模型在低速冲击下能更好地模拟UHPC材料的实测波形和动态应力-应变曲线,而在中高应变率下KCC模型和HJC模型得到的计算波形以及动态应力-应变曲线与实测值吻合度更好;低应变率下三种损伤模型得到的DIF值相差不大,但随着应变率提高,CSC模型在一定程度上将低估UHPC材料的动力特性;UHPC试件破碎程度随应变率的增加而增大,相对于CSC模型在冲击破坏时表现出的核心存留现象,KCC模型和HJC模型分别表现出明显的整体塌陷和边缘塌陷现象。结论对于UHPC材料,CSC模型适用于低速冲击下SHPC试验数值模拟,而KCC模型和HJC模型适用于中高应变率下数值模拟。

基于多场耦合仿真的四轨电磁发射器性能分析

电磁轨道发射器的工作过程涉及复杂的多物理场耦合现象,仅通过解析计算难以实现对电磁轨道发射器性能的全面分析。为了对电磁轨道发射器的动态发射过程进行研究,以四极凸轨道电磁发射器作为研究对象,建立了瞬态电磁-热-结构多物理场耦合仿真模型,采用CLM模型模拟发射过程中过盈电枢与轨道的电接触现象,得到了发射器工作过程中电枢、轨道受力随时间变化情况和电磁场、应力、温度分布。研究结果表明,发射器电枢、轨道受力的变化趋势与激励电流的变化趋势接近,趋肤效应和速度趋肤效应会引起受力的削弱。电磁力会改变接触面上的压力分布,改善枢轨接触状态,进而改变接触区域的电流分布。发射过程中,由于摩擦力作用,温升最大处位于电枢臂尾端而电流密度最大值出现在电枢喉部。所做的研究对了解发射器的动态发射过程及发射过程中的多物理场耦合机理具有一定参考意义。

乏燃料连续溶解过程的动态仿真模型研究

本文通过分析乏燃料芯块与硝酸之间溶解反应的质量传递过程,以及溶解液中溶质的质量传递过程,基于质量衡算得到了乏燃料芯块溶解过程的动态溶解模型,并利用Comsol和Matlab软件建立了求解溶解模型的仿真程序。仿真结果表明,在温度90℃、硝酸进料浓度6 mol/L、进料流率11 L/min、回流量35 L/min的工艺条件下,溶解液需要270 min达到出料要求,而达到平衡所需时间为2000 min。达到平衡后的溶解液出料中,铀浓度为253.23 g/L、硝酸浓度为2.78 mol/L,能满足出料要求。模拟结果的全过程质量平衡计算表明,模拟结果与理论计算值的相对误差为2.57%。模拟结果中溶质浓度变化趋势与实际过程基本一致,溶解器内铀浓度总体上呈先迅速升高、后较快减小、最后又缓慢减小,而硝酸浓度总体变化趋势则与铀浓度的变化趋势相反。以上结果表明,本研究所建立的回转式连续溶解器动态溶解仿真模型能较好地描述该溶解器中乏燃料的实际溶解行为,能为实际生产过程中乏燃料溶解工艺段提供仿真数据支撑。

近海三维泥沙输运数值模拟研究及其应用进展

本文总结了近海泥沙在波浪、潮流、波流耦合、风暴和陆架环流等动力作用下的输运特点,概述了较为著名的近海海域三维泥沙输运模型的特点及其在港口航道工程、海底地貌演变、海水水质监测等方面的应用进展。泥沙输运数值模型构建需要物理海洋学、沉积学、生态学、计算机科学等多学科理论支撑,现已从泥沙输运路径模拟向多模型耦合方向发展。因此,开展泥沙动力学、环境生态学、地貌动力学等相关理论的研究能够拓宽泥沙数值模拟研究的应用场景,使其服务于更多涉海领域。