Integrated fluid-thermal-structural numerical analysis for the quenching of metallic components

The quenching of a metal component with a channel section in a water tank is numerically simulated. Computational fluid dynamics (CFD) is used to model the multiphase flow and the heat transfer in film boiling, nucleate boiling and convective cooling processes to calculate the difference in heat transfer rate around the component and then combining with the thermal simulation and structure analysis of the component to study the effect of heat transfer rate on the distortion of the U-channel component. A model is also established to calculate the residual stress produced by quenching. The coupling fluid-thermal-structural simulation provides an insight into the deformation of the component and can be used to perform parameter analysis to reduce the distortion of the component.     

危岩主控结构面损伤-断裂数值模拟研究

危岩是迄今研究程度极其薄弱的地质灾害类型,而主控结构面受荷损伤断裂扩展过程是危岩发育机理研究的核心技术.本文通过对主控结构面裂端损伤区范围确定及损伤区损伤材料参数的求解,运用有限元数值模拟方法对天然状态工况、持续暴雨工况及地震工况进行了数值模拟,获取了不同工况主控结构面的断裂韧度富余系数,与危岩体的稳定系数具有良好的一致性.     

连续两弯水流特性的数值模拟研究

连续两弯的过渡段及后弯水流特性明显受到前弯水流的影响.采用RNGκ-ε湍流模型和VOF方法处理自由水面的水、气两相流数学模型,对中心角为120°带过渡段的连续两弯水流进行计算,分析了连续两弯的断面环流和表面流态.分析结果表明,连续两弯的过渡段表面存在回流；回流与前弯剩余环流叠加,在后弯进口水面出现环流强度＜0.14的特...     

Optimization of pellet production process parameters in grate using simulation results

The objective of this paper is to optimize the parameters of pellet drying and preheating process in grate. A mathematical model of drying and preheating is developed, and is verified by the experiments. Further, the operating parameters of wind temperature, wind speed, grate speed and bed depth etc. are investigated through the orthogonal method using the simulation results. And a relationship of drying, preheating effects and operating parameters is achieved. The results show that the optimization effect can be achieved in the given range when air velocity is about 3.0 m/s and temperature is about 300, 500, 800, and 1 100 °C in the updraft drying zone, downdraft drying zone, preheating I zone, and preheating II zone respectively. The work is help for saving energy and reducing emissions in pellet induration.     

Optimization of pellet induration process parameters in rotary kiln using simulation results

In order to optimize the pellet induration process parameters of rotary kiln, a mathematical model is developed and solved by using commercial software FLUENT. Orthogonal regression has been performed by using the simulated results of the pellet induration in rotary kiln. The functional relations between pellet induration quality and process parameters are obtained. The main parameters that affect the thermal process are also discussed. The results show that the high temperature zone is longer and the local high-temperature could be avoided while the velocity difference decreases between the secondary air and the carbon particle, which leads to more uniformed temperature distribution and better induration quality. The work gives a right direction on improving of pellet production.     

岩溶隧道开挖围岩力学及渗流三维数值模拟

依托贵州省在建的新寨隧道,用 ABAQUS 有限元软件建立计算模型,模拟隧道施工过程中围岩及衬砌结构的变形和受力特征。考虑地下水的作用,计算了围岩的孔隙水压力和分布规律。分析结果表明：隧道开挖过程中,围岩存在一定程度的应力释放,隧道拱顶和仰拱底部局部会出现较小的拉应力,而在隧道边墙部分则出现应力集中的现象。隧道开挖应力影响范围约为2倍洞径,在1倍洞径范围内影响较大,不宜在不作处理的情况下修筑其他地下空间结构。隧道围岩塑性区沿隧道径向影响范围约为4 m。     

基于 Fluent 防雪栅栏数值仿真研究

运用CFD软件Fluent ,针对特定的防雪栅栏,简要叙述其作用机理,选取新疆塔城地区S201线典型断面,对不同的防雪栅栏的水平距离、路堤高度以及边坡坡率等参数设定,基于风雪流的气固两项性并采用一定的数学模型进行数值模拟,进行雪害沉积的规律研究和模拟参数的合理确定,从而为新疆公路风吹雪灾害提供一种快速、经济、可靠的治理方法。     

Three-dimensional numerical simulation of splat formation on substrates in plasma spraying

Plasma sprayed coatings are built up by the accumulation of splats formed by the impacting, spreading and solidifying of molten droplets on the substrate. A three-dimensional computational model including heat transfer and solidification is established to simulate the formation process of a single splat using the computational fluid dynamics (CFD) software, FLUENT. The fluid flow and energy equations are discretized and solved according to typical finite volume method on an unstructured grid. A volume of fluid (VOF) tracking algorithm is used to track the droplet flow with free surface. In order to understand the splat formation mechanism, the process of splat formation caused by impacting and spreading of a molten nickel droplet on a polished mild steel surface is simulated. On this basis, the simulations of impact of a molten droplet on substrate with different conditions including the surface morphology, thermal conductivity, initial temperature of the substrate and the thermal contact resistance are presented. The results clearly show the effect of those parameters on the shape of the final splat and splash behaviors.     

基于数值仿真的多开孔车轮定位器优化设计

针对车轮定位器的阻挡作用与其准确的定位特点,提出车轮定位器优化方法,使其性能得到了改善。为获得多开孔车轮定位器的最佳组合参数,采用正交试验法,以横截面的4个因素为设计变量,每个变量设计3个水平,建立了车辆与车轮定位器的有限元模型,并进行了9组试验。用 LS-DYNA 软件进行仿真分析,其结果与常用的车轮定位器性能进行比较。验证结果表明：多开孔车轮定位器能够有效地加强定位器的阻挡作用,且能做到准确定位的功能,达到优化的效果。     

轨道短波不平顺数值模拟新方法

针对轨道短波不平顺问题, 提出了一种基于离散二进制小波的轨道短波不平顺数值模拟方法, 将ISO 3095标准谱作为目标函数, 得到了ISO 3095标准谱和小波系数的关系, 给出了数值模拟算法流程与步骤, 并将数值模拟结果与上海某段地铁实测结果进行了对比分析。分析结果表明: 合适的小波分解层数为8层, 最低层包含的波长范围为512~1 024 mm; 短波不平顺数值模拟时域波形符合实际轨道短波不平顺的统计特征, 呈现非平稳性, 幅值分布范围为-0.15~0.15 mm; 数值模拟结果与ISO 3095标准谱之间存在的差异由倍频程采样间隔与三分之一倍频程采样间隔的差异造成。可见, 采用二进制小波变换可以有效实现轨道短波不平顺的数值模拟, 模拟结果与实测结果在幅值和细部波形方面略有差别, 建议对轨道短波不平顺进行大量的测量与统计分析。     

岩质边坡动力失稳机制及数值模拟研究

在分析岩质边坡动力破坏机制的基础上,采用FLAC3D方法,建立了四川震区理县至小金公路工程中豹子嘴岩质边坡三维数值模型.以永久位移作为评价指标,在对四川5.12汶川MS8.0大地震中理县地震台实测地震波校正的基础上,对该岩质边坡在地震荷载作用下的动力稳定性进行了数值模拟.计算结果表明,该岩质边坡在地震荷载作用下并未出现明显的拉应力区,主要以＂压-剪＂破坏模式为主,由于边坡内部分布的应力并不大,该边坡总体上仍为较稳定边坡;在地震荷载作用下,边坡位移呈现出明显的分层现象,位移分布总体上呈现由坡内向坡外、由坡底向坡顶逐步增大的趋势.考虑到地震动力作用下边坡的永久位移偏大,且边坡坡脚处出现了应力集中,应增设SNS主动防护网及矮脚墙进行防护.     

Sensitivity Analysis of Effect Related with Material Process and Assembly Variations to Loads Deformation and Stress on HSS Stamping Die

During stamping process, the material properties, process design parameters and production environments inevitably have variation and noisy factors, which possibly affect the sheet metal formability and the deformation of the die structure.After gaining a success in applying sheet metal forming numerical simulation analysis to get the forming loads during stamping process, a methodology of die structure analysis based on sheet metal forming simulation was proposed and validated by experiments.Based on these results, the effect related with initial blank thickness, blank holder force, blank positioning error and die alignment error variations to a DP600 hyperbolic bottomed cup drawing die's forming loads(especially unbalanced loads), and deformation and stress was studied numerically.The influence level of these variations to the die's forming loads, deformation and stress was disclosed.The findings can guide die design, die tryout and process control for high-strength steel(HSS) stamping with increased forming load and decreased sheet metal formability.     

The numerical simulation of a towing cylinder based on immersed body boundary method

An immersed body boundary method is adopted to track the motions of a towing cylinder, and a homogenous multiphase Eulerian-Eulerian fluid approach is used to capture the free surface. The Reynolds average Navier-Stockes (RANS) solver is applied to all gird nodes to deal with different velocities of the nodes that are in the body boundary, near the boundary and out of the boundary and their effect on the fluid. The towing cylinder resistance at different submerged depths in the tank is presented. The simulation results are compared with the experimental data, and the method is verified and validated. Finally, the hydrodynamic characters of the cylinder are discussed further. The numerical and experimental results show that at high speeds, the deeper the cylinder submerges, the lower resistance it suffers. The resistance coefficient trough is obtained at Froude number in the range of 0.3 < F r < 0.4. These phenomena can provide some suggestions on the small waterplane area twin hull (SWATH) design.     

电厂天然气锅炉富氧燃烧数值模拟

对传统燃烧方式下和应用富氧燃烧技术（O2/CO2燃烧技术）时电厂天然气锅炉内的燃烧特性进行数值模拟研究.结果表明随着氧气浓度的增大,整个炉膛的高温区分布趋于集中,烟气温度增加,火焰分布更为集中,充满度也越来越差.当氧气浓度为25%时,炉膛内的温度分布和烟气辐射特性与传统燃烧方式下最接近.当氧气浓度由21%上升到40%时,炉膛内烟气温度得到较大幅度的提高,燃烧器所在截面温度上升300 K以上,火焰充满度变差.     

车辆吸能部件的碰撞试验与数值仿真

为了设计某列车耐撞性车体, 实现列车被动安全保护, 进行了台车碰撞试验和数值仿真计算, 研究了耐撞性车体吸能部件的吸能特性。在台车撞击试验过程中, 吸能部件从预期部位开始发生稳定有序的塑性变形, 吸收的冲击动能与最大变形量基本成正比关系, 说明该部件具有良好的吸能效果。并在此基础上, 应用显式动力有限元理论建立了其有限元撞击模型, 进行了数值仿真计算。相关性分析结果表明: 仿真结果与试验结果基本一致, 在整个撞击过程中, 撞击力曲线基本吻合, 最大撞击力峰值分别为2486.3、2423.1kN, 最大变形量误差和初始撞击力峰值误差都小于3%, 反弹速度误差小于4%。显然, 利用撞击试验验证了数值计算的有效性和可靠性, 利用数值计算设计和优化车辆吸能部件是可行的。     

高填方块碎石夯实地基变形三维数值模型

根据场区的工程地质条件和高填方资料建立地质模型, 运用现场试验所获得的参数和3DFLAC程序对高填方块碎石夯实地基的变形进行数值模拟, 分析地基沉降和侧向变形及可能发生剪切破坏的位置, 模拟和分析结果与实际基本一致。     

破舱倾覆船体扳正过程数值模拟

考虑了破舱倾覆船体浮性和稳性, 研究了船体在扳正过程中空间位置和受力状态; 采用欧拉旋转变换方法建立了船体空间力学平衡方程, 根据船舶静力学原理, 得到了破舱倾覆船体稳性和扳正力数学模型; 根据伯努利定理计算了破舱进水量及其对船体重心和浮心位置的影响; 利用GHS软件模拟了破舱倾覆船体的扳正过程, 求解了其最大扳正力和进水量, 计算了船体纵向6个位置的剪力、弯矩和扭矩。计算结果表明: 在最初扳正时, 破舱进水导致倾覆船体扳正力矩降低了130.312 MN·m, 说明破舱进水降低了倾覆船体的稳性, 可以减小最初扳正力, 降低了扳正难度; 在扳正后期时, 破舱进水产生的倾斜力矩最大值为163.594 MN·m, 说明破舱进水降低了船体的稳性, 提高了扳正难度, 仍需要施加较大的扳正力平衡船体; 船体纵向强度分布会随着扳正力和破舱进水量的变化而改变, 多点扳正船体的最大扳正力小于单点最大扳正力的40%, 最大扭矩小于单点扭矩的50%;方案1~4的最大进水量分别为6 269.76、6 781.01、5 830.76、6 653.33t, 因此, 合理布置扳正点的位置, 单点扳正(方案1~3) 的进水量小于多点扳正(方案4)。     

阳宗隧道试验段动态开挖过程的数值模拟研究

根据昆明—石林高速公路阳宗隧道S5型支护衬砌设计优化调整方案和XK38+926断面现场监控量测数据,进行位移反分析,得到计算所需的围岩弹性模量E和侧压力系数K_0;然后运用有限元方法,对其试验洞段上下台阶开挖动态施工过程进行仿真数值模拟研究,从而反馈调整和指导施工。     

泥石流与主河交汇区三维数值模拟

依据流体力学和非牛顿流体力学原理,建立了交汇区混合流运动方程,分析并提出了双场交汇计算的耦合模型,主要包括数值计算方法、交汇区流变关系和泥沙沉降关系.通过计算表明,该三维耦合计算模型能与实测资料相吻合,并能详细刻画交汇区泥沙浓度分布规律及主河水位的变化.