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1.
物体浅水冲击会造成结构响应和自由液面的剧烈喷溅,以往的研究多集中在物体受水的冲击响应方面,而对浅水层受物体冲击引起的剧烈喷溅问题及其喷溅抑制结构的相关研究很少。本文基于SPH/FEM耦合方法对浅水冲击的液体喷溅特性开展研究。首先,计算了刚性长方体结构的冲击喷溅,与文献中准二维溅水试验结果进行了比较,将浅水喷溅分为初始喷溅、二次喷溅和底部射流三部分。分别研究了各部分喷溅的形成机理,指出二次喷溅由结构对水层的挤压和底部射流的能量传递共同引起,并分析了水深对二次喷溅的影响规律。其次,对喷溅抑制结构的机理做了数值研究,发现拱形翻边构型可以抑制初始喷溅,但不能有效降低二次喷溅。最后,提出了一种带凹槽和阻水边条的新型翻边构型,对二次喷溅具有更好的抑制效果。  相似文献   
2.
This paper develops a framework to deal with the unconditional superclose analysis of nonlinear parabolic equation. Taking the finite element pair $Q_{11}/Q_{01} × Q_{10}$ as an example, a new mixed finite element method (FEM) is established and the $τ$ -independent superclose results of the original variable $u$ in $H^1$-norm and the flux variable $\mathop{q} \limits ^{\rightarrow}= −a(u)∇u$ in $L^2$-norm are deduced ($τ$ is the temporal partition parameter). A key to our analysis is an error splitting technique, with which the time-discrete and the spatial-discrete systems are constructed, respectively. For the first system, the boundedness of the temporal errors is obtained. For the second system, the spatial superclose results are presented unconditionally, while the previous literature always only obtain the convergent estimates or require certain time step conditions. Finally, some numerical results are provided to confirm the theoretical analysis, and show the efficiency of the proposed method.  相似文献   
3.
建立了一种细胞趋硬性迁移的理论模型和有限元分析框架,为连续变刚度人工基质的试验设计提供理论依据。考虑了细胞体的黏弹性属性,以及细胞与基质间的配受体动态反应过程,并以配受体合成时间为时间步长,将细胞运动方程化为静力学形式进行求解。对有限元过程提出一种动约束,便于消除其结构矩阵的奇异性。结果表明,模型能够模拟黏着斑内部力的快速波动现象,细胞的运动速度与观测数据一致,可有效模拟20,h以上的长时程问题。  相似文献   
4.
针对铁路道床有砟-无砟过渡段的结构特点,采用离散元-有限元耦合模型分析散体道砟和无砟道床间过渡段的动力特性。散体道砟道床和无砟道床分别采用离散元方法 DEM和有限元方法 FEM模拟,而在过渡段将道砟颗粒嵌入无砟道床以增加道砟颗粒与无砟道床间的咬合力,并在离散元和有限元耦合区域实现了力学参数的传递。采用以上DEM-FEM耦合方法对有砟-无砟道床及其过渡段在列车荷载作用下的沉降过程进行了数值分析。计算结果表明,离散元方法中道砟颗粒间的力链呈现非对称梯形分布,其与有限元方法中的应力分布趋势一致;采用嵌入式道砟颗粒的方法可以增加有砟-无砟过渡段道砟间的咬合力,有效约束道砟颗粒的位移,减少有砟-无砟道床间的沉降差异。本文计算模型可以合理地分析有砟道床的力链分布以及无砟道床的应力分布,确定列车荷载下道床有砟-无砟过渡段的动力学行为。  相似文献   
5.
王军  姚熊亮  郭君 《爆炸与冲击》2015,35(6):832-838
为研究安装甲板模拟器的浮动冲击平台系统考核舰载设备的机理,对整个系统建立有限元模型进行数值模拟并建立力学模型进行了理论分析。根据船体甲板结构产生的垂向低通滤波特性,提出甲板模拟器具有减缓高频冲击并满足设备安装频率要求的作用。将被试设备的浮动冲击平台考核系统简化为有阻尼的三自由度系统强迫振动模型,通过拉普拉斯变换方法求解了不同冲击环境下被试设备的响应。数值模拟与理论计算结果比较吻合,被试设备响应迅速达到峰值后逐渐衰减,振动频率由高频向低频过渡,在分析浮动冲击平台舰载设备考核系统长时间响应时需考虑阻尼的影响。  相似文献   
6.
The airship structures made of multi-layer composite fabrics or membranes can offer the platform for earth observations, wireless communications and space research due to light weight and good mechanical performance. The structural safety and serviceability strongly depend on material properties and working conditions. Available studies are limited within service stress limits or are lack of suitable biaxial tensile constitutive models for understanding structural behavior. This paper thus focuses on a refined numerical model for determining inflation-burst behavior of composite airship structures considering new biaxial constitutive equations, novel failure criteria and manufacture factors.The differences between ideal and real forms of airship structures, e.g. volume difference, demonstrate the necessity for incorporating cutting-pattern effects in the initial numerical model. For structural analysis, stress distributions on real structural forms are different from those on ideal forms because of welding parts that can enhance local stiffness. The ultimate pressures are 56.7 kPa and 59.5 kPa for ideal and real structural forms. Structural breaking initiated at the maximum diameter of ideal structural forms propagates fast while welding parts can prevent breaking propagation for real structural forms. Therefore, the refined numerical model can reveal basic structural behavior and safety performance of airship structures in the inflation-burst processes.  相似文献   
7.
The dielectric elastomer (DE) has attracted significant attention due to its desired features, including large deformation, fast response, and high energy density. However, for a DE actuator (DEA) utilizing a snap-through deformation mode, most existing theoretical models fail to predict its deformation path. This paper develops a new finite element method (FEM) based on the three-parameter Gent-Gent model suitable for capturing strain-stiffening behaviors. The simulation results are verified by experiments, indicating that the FEM can accurately characterize the snap-through path of a DE. The method proposed in this paper provides theoretical guidance and inspiration for designing and applying DEs and bistable electroactive actuators.  相似文献   
8.
In this article, we study the superconvergence analysis of conforming bilinear finite element method (FEM) for nonlinear Joule heating equations. Based on the rigorous estimates together with high accuracy analysis of this element, mean value technique and interpolation postprocessing approach, the superclose and superconvergent estimates about the related variables in H1‐norm are derived for semidiscrete and a linearized backward Euler fully discrete schemes, which extends the results of optimal estimates obtained for conforming FEMs in the previous literature. At last, a numerical experiment is performed to verify the theoretical analysis.  相似文献   
9.
Ultra-high pressure belt-type die was designed with a large sample volume prism cavity and a split cylinder which was divided into eight segments to eliminate circumferential stress. The cylinder of this type die has no cambered surface on inner wall, and the inner hole is a hexagonal prism-type cavity. The divided bodies squeeze with each other, providing the massive support and lateral support effect of the cylinder. Simulation results indicate that the split cylinder with the prism cavity possesses much smaller stress and more uniform stress distribution. The split cylinder with the prism cavity has been shown to bear larger compressive stresses in radial, circumferential and axial directions due to its structure, and tungsten carbide is most effective in pure compression so this type cylinder could bear higher pressure. Experimental results prove that the high pressure apparatus with a prism-type cavity could bear higher pressure. The apparatus with a prism cavity could bear 52.2% more pressure than the belt-type die.  相似文献   
10.
基于商用软件的等离子体数值模拟方案大多是基于标准Galerkin格式的有限元方法,在计算大气压流注放电时,存在数值振荡和伪扩散的问题,计算结果可靠性不高.针对针-板体流注放电结构,构建了修正的COMSOL Multiphysics等离子体模型.修正模型与COMSOL Multiphysics内置等离子体模块的区别主要在于增加了基于弱形式的人工稳定项.利用修正模型复现了经典的雪崩-流注转捩算例,并与经典纳秒秒冲过电压针板放电实验结果进行了对比验证.结果表明,引入修正后的商用软件模型能够克服数值振荡和伪扩散缺陷,确保等离子体数值计算的准确性和可复现性.   相似文献   
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