冻土条件下均质土堤漫顶溃决试验研究

为了研究冻土条件下的溃堤机理,开展了弯道水槽概化模型试验。基于结构光的三维成像原理,提出了一种无干扰全方位的实时溃口三维参数测量方法,并结合温度传感器监测堤内温度变化,研究了冻土条件下均质土堤漫顶溃决过程中溃口形态的演变规律和溃决区域的水位、流速、流量变化特性。依据试验中溃口冲蚀特点,将溃堤过程划分为渗透过流、堤后冲蚀、横向展宽、冲淤平衡4个阶段,黏性土堤和非黏性土堤第2阶段、第3阶段分别以陡坎冲蚀和失稳坍塌为主要特征,且黏性土堤会出现明显的陡坎合并现象。试验结果还表明:冻结后土体间隙的冰晶体与土颗粒相互胶结,土体的黏聚力增大,溃口扩展速率及溃决区域的水位、流速变化率均减小,且黏性土堤受冻土深度的影响更加明显;冻土条件下堤防背水侧与堤顶的连接处薄弱易溃,应加强维护,且一旦溃堤应优先对临水侧进行封堵。     

基于阿里云的四维弹簧模型并行运算性能

四维弹簧模型（Four-Dimensional Lattice Spring Model,4D-LSM）是一种考虑额外维相互作用的新型离散数值计算方法。该方法用于岩石破坏分析需要消耗大量计算资源,不适合在普通个人电脑上运行。基于多核并行技术,在阿里云和多核工作站等多种硬件环境下对4D-LSM的计算极限性能及瓶颈进行详细分析,主要研究了求解规模、求解类型、线程数、硬件配置等对4D-LSM求解效能的影响。研究发现,内存容量决定可计算的模型规模,弹性问题的计算时间与模型规模成正比,并行计算效率受CPU性能和内存带宽的共同影响。在不考虑经济因素的情况下,云计算在多核匹配和内存分配方面的灵活性特别适合于四维弹簧模型的并行计算分析。结果表明：基于阿里云的4D-LSM最大运算规模可以达到十亿单元,由于目前的瓶颈在于前后处理,4D-LSM目前的可分析规模仍然限制在两千万单元。最后,展示了采用极限规模的并行四维弹簧模型求解三维币形裂纹扩展的实际应用案例。     

平面SV波入射下弹性半空间中三维球形洞室的动力响应

采用一种间接边界积分方程法求解了平面SV波入射下弹性半空间中三维洞室的动力响应问题。通过与已有结果的比较,验证了方法的计算精度。在此基础上,以半空间中圆球形洞室为例,对地表位移响应和洞周动应力集中特征进行了详尽的参数分析,并与二维模型进行了比较。研究表明:二维和三维模型对平面波的动力响应在平面内存在一定的相似性,但在波型转换上存在显著差别,尤其体现在响应峰值及空间分布特征上,并且随着频率的升高,空间分布差异愈加明显;在出平面方向,三维洞室周围存在着显著的波散射效应,而二维模型难以描述这种出平面波型转换现象。     

FLNG甲板上部天然气管线破断低温损伤后果研究

为了研究浮式液化天然气(FLNG)生产储卸装置甲板上部区域天然气产品输送管线发生泄漏的低温损伤后果,建立了甲板上部区域的泄漏扩散模型,将泄漏分为了低温气态天然气泄漏和液态LNG泄漏两大类,运用计算流体力学(CFD)软件和API相关规范确定了其泄漏扩散范围和低温区域。结果表明:当发生低温气态天然气泄漏时不会造成设备的低温损伤,但是时甲板人员有低温损伤风险;当发生液态LNG泄漏时,造成设备损坏和人员受伤。     

Closed-form integration of singular terms for constant,linear and quadratic boundary elements. Part 1. SH wave propagation

One of the most important aspects in the application of boundary element techniques to wave propagation problems is the accurate representation of the singular terms at the points of application of the virtual loads. It is current practice to carry out this task by means of numerical quadrature. This paper presents an analytical evaluation of the singular integrals for constant, linear and quadratic boundary elements involving SH waves, the results of which are then used to model inclusions in a two-dimensional acoustic medium illuminated by dynamic anti-plane line sources. Finally, the BEM results are compared with the known analytical solutions for cylindrical inclusions.     

SIF evaluation and stress analysis of drillstring threaded joints

In a study by Tafreshi and Dover [1], [2], [3] stress analysis of drillstring threaded joints under axial, bending and torsion loadings was carried out using the finite element method. Stress concentrations were determined on a variety of threaded joints in order to predict the fatigue life of these components. Here some of those results are presented in more detail. In this study it is shown that in the case of bending, axisymmetric solid elements with non-linear, asymmetric deformation with fourier interpolation can be employed which reduces the computational time and modelling in comparison with the full three-dimensional analysis. Quasi semi-elliptic circumferential internal and external cracks in tubes with the same dimensions of the pins or boxes of a series of joints are modelled and analysed using the J-integral method. The result of this fully three-dimensional crack analysis shows the same trend as experimental [3] and published results [4].     

波浪荷载作用下海上新型潜式浮式风力机运动特性研究

以适用于中等水深(50~200 m)的新型潜式浮式风力机为研究对象,该风力机基础综合Spar式、半潜式及张力腿(TLP)3类浮式风力机基础的优点,运行时基础主体淹没在水下,具有较小的水线面(如同Spar平台),受波浪影响较小;平台通过张紧式系泊线与海床相连(如同TLP平台),具有良好的垂荡和摇摆运动特性;拖航状态下,浮式平台处于半潜状态,水线面面积大(如同半潜式平台),具有良好的浮稳性。通过分析不同波况下的潜式浮式风力机耦合动力响应得到潜式浮式基础的横荡、纵荡、垂荡及纵摇运动响应,以及发电功率、叶片根部弯矩、塔筒顶部和底部弯矩、锚链张力时程曲线。研究结果表明:波浪对于结构的纵摇运动的影响最为明显,对发电功率、叶片根部弯矩和塔筒顶部弯矩影响较小,对塔筒底部弯矩和系泊线张力影响较大。