共查询到19条相似文献，搜索用时 703 毫秒
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考虑海冰热力因素对其厚度、密集度的影响,在光滑质点流体动力学(SPH)基础上发展了一个海冰热力-动力数值模式。该模式既解决了传统欧拉有限差分法和质点网格法存在的数值扩散问题,同时弥补了光滑质点动力学海冰动力模式未考虑热力因素的不足,具有精确模拟冰缘线运动、计算精度高等优点。首先介绍了光滑质点流体动力学的基本原理,并对海冰生消的热力因素进行了分析,将影响冰厚和密集度的热力因素引入到光滑质点流体动力学的海冰动力模式中,得到该热力-动力模式的控制方程。应用该数值模式对渤海海冰进行了48 h数值模拟,得到了海冰厚度和速度矢量的分布规律;对JZ20-2海域的海冰厚度、冰内温度场分布以及热力因素的变化特性进行了讨论。数值模拟结果表明,该数值模式能够很好地适用于渤海海冰数值模拟,是一种有效的海冰数值模拟方法。 相似文献
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以页岩油气为代表的低品位油气资源勘探与开发不断取得重大突破,已经成为中国重要的接替性资源。开展页岩气渗流机理和数值模拟模型研究有助于实现页岩气藏开发的动态变化过程,为认识页岩气渗流规律、优化数学模型、产能评价和预测奠定技术基础。围绕页岩气多尺度多流态多重介质下的运移机理,系统地阐述了页岩气数值模拟模型的研究进展,页岩气数值模拟模型可分为等效连续介质模型、离散裂缝网络模型和混合模型,总结了这3类数值模拟模型的优缺点。等效连续介质模型原理简单,追求宏观尺度的等效,忽略了储层内部真实流态,适用于裂缝发育程度低的均质页岩气藏;离散裂缝网络模型准确反映复杂裂缝网络的渗流特征,可以描述高度离散裂缝的形态规律,适用于勘探程度高且裂缝高度发育的页岩气藏;混合模拟模型结合两者的优点,能够准确反映复杂裂缝网络和流体运移规律,在满足计算精度的同时又节约了大量的计算资源,随着计算处理能力的增强,混合模拟模型是今后的发展趋势。最后分析了页岩气藏数值模拟模型中存在的问题,并指出了发展方向。 相似文献
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随着计算能力的不断提高,数值天气预报模式的水平网格分辨率已经达到公里—次公里量级,这一网格尺度与对流边界层中的湍流特征尺度相当,数值模式可以对有组织对流结构进行解析计算。传统的一维边界层参数化方案（适用于几公里或更粗水平分辨率）和大涡模拟三维湍流闭合方案（适用于几十米以下水平分辨率）的假设条件在这一尺度上均不成立,称为对流边界层的灰区尺度。在讨论传统参数化方法的适用性和局限性的基础上,从理论、方案方法和影响3个方面介绍了对流边界层灰区尺度的研究进展,总结了近20年来国内外发展的各对流边界层灰区尺度模拟方法的特点,探讨了该尺度上边界层过程对数值模式中其他物理过程（如浅/深对流等）的影响,最后展望了未来可能的研究方向和思路。 相似文献
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土体的大变形流滑导致了许多地质灾害的发生,对人们的生命财产安全构成了极大的威胁,因此越来越多的研究开始关注土体的大变形流滑特性。其中,光滑粒子流体动力学（SPH）方法是常用的模拟方法之一,但SPH方法的粒子特性导致其计算时间过长,影响了在工程地质领域的进一步应用。对此,本研究基于SPH方法的基本原理、非牛顿流体理论和等效黏度概念,提出了适用于土体大变形流滑分析的三维SPH仿真模型。结合OpenMP并行计算原理,实现了SPH算法的并行优化。在此基础上,对土体流滑模型试验进行了二维和三维分析,得到了滑动距离、滑动冲击力和冲击力峰值等动力学参数,分析了计算维数和边界条件对流滑特性的影响机制。通过不同线程数下计算时间的对比,获得了计算效率随线程数的变化规律。结果证明了本文的OpenMP并行优化具有较高的计算效率,显著降低了三维SPH模拟的计算耗时,对工程地质数值方法的效率提升具有重要的借鉴意义。 相似文献
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海冰拖曳系数的确定方法研究 总被引：3，自引：0，他引：3
风和流对海冰的拖曳系数是海冰数值模式中的基本参数, 它是精确模拟海冰漂移轨迹, 分析海冰的动力破坏、海冰爬升与堆积问题的重要依据.首先讨论了计算海冰拖曳系数的3种方法, 即涡动法、剖面法和动量法, 并分析了它们各自的特点和适用条件.针对辽东湾JZ20-2油气平台上同步连续观测的风速、流速和冰速等资料, 选用动量法对海冰拖曳系数进行了计算, 得到低密集度条件下光滑平整冰的风拖曳系数Ca(42) =1.402×10-3, 流拖曳系数Cw(7) =2.563×10-3.该数值能反映风和流对海冰表面拖曳和形状拖曳的共同作用.不同冰类型和密集度条件下的海冰拖曳系数有很大差异, 对其进一步的研究结果将提高海冰数值模拟的精度. 相似文献
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开展地下水数值模拟研究是高放废物处置场地安全评价的重要组成部分,然而深地质处置介质类型的复杂性、基岩深部资料的相对匮乏性导致模拟结果存在不确定性,如何刻画深部地下水动力场并评估可能引起的风险已成为高放废物处置安全评价中重点关注的问题。在大量文献调研的基础上,综述了世界典型国家高放废物深地质处置场地的地下水数值模拟与不确定性分析应用,并归纳总结该领域研究经验,得到以下认识:（1）深地质处置场深部构造、裂隙的发育与展布决定了地下水循环条件,探究适用于基岩裂隙地区新的水文地质试验方法是提高地下水数值模型仿真性的基础;（2）不同尺度模型融合是解决深地质处置地下水模拟的有效技术方法,区域尺度多采用等效连续介质法,场地尺度使用等效连续多孔介质和离散裂隙网络耦合模型,处置库尺度使用离散裂隙网络方法,其次需重点关注未来大时间尺度下放射性核素在地质体中的迁移转化规律,模拟预测场址区域地下水环境长期循环演变对核素迁移的潜在影响;（3）考虑到不同的处置层主岩岩性以及在多介质中发生的THMC（温度场—渗流场—应力场—化学场）过程,目前国内外常用的地下水模拟软件有:Porflow、Modflow、GMS及MT3DMS等用于模拟孔隙或等效连续介质,Connectflow、Feflow及FracMan等用于模拟地下水和核素在结晶岩、花岗岩等裂隙中的迁移,TOUGH系列软件主要应用于双重介质的水流、溶质及热运移模拟;（4）指导开展有针对性的模型和参数的不确定性分析工作,减少投入工作量,提高模型精度,并可针对处置库长期演变、废物罐失效、极端降雨等多情景预测模拟,为处置库安全评价及设计提供基础数据支撑;（5）针对我国深地质处置地下水数值模拟研究现状,下一步应加强区域地质、水文地质、裂隙测量以及现场试验等相关的调查及监测工作,多介质耦合、多场耦合模拟及不确定性分析研究将会是未来的研究重点。 相似文献
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弹丸侵彻无钢筋混凝土的数值模拟 总被引：1，自引：0，他引：1
采用二维梁-颗粒模型BPM2D（beam-particle model in two dimensions）模拟了刚性弹丸侵彻无钢筋混凝土的过程。离散元法（DEM）和有限元法（FEM）等数值计算方法各有其优势,同时也都存在不足之处：离散元法适于处理由连续介质向非连续介质转化的破坏问题,但对于连续体计算结果精度不高;有限元法适于预测材料破坏的区域,但难以直接用于计算脆性材料破坏过程,因此将两种方法结合可以形成一种较好的混合模型。梁-颗粒模型BPM2D是基于离散元法,结合有限元法开发的二维数值计算模型,采用3种类型梁单元形成混凝土数值试样,每种类型梁单元的力学性质均按韦伯（Weibull）分布随机赋值,以模拟混凝土细观结构的非均匀性,同时梁单元的强度随应变率不同而变化。利用此模型分析了弹丸侵彻下混凝土的破坏过程,并给出侵彻过程弹丸减速度-时间历程曲线。比较计算结果与试验数据表明梁-颗粒模型可有效应用于计算和模拟脆性材料动态破坏问题。 相似文献
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针对光滑粒子流体动力学方法（SPH）在滑坡模拟中建立粒子模型的难题,提出了基于地理信息系统（GIS）栅格数据的粒子排列与插入方法。根据该方法,建立了滑坡SPH粒子模型及相关粒子生成程序,进一步以结合摩尔-库仑破坏准则的SPH宾汉流体模型为核心,实现了运用SPH方法模拟滑坡破坏后三维运动的过程。该SPH模型在对唐家山滑坡的模拟中得到了验证,并预测了金坪子滑坡破坏后的影响范围。结果表明：基于GIS空间数据的滑坡SPH粒子模型具有可行性与良好的适用性。以GIS数据库为基础,开展滑坡灾害的模拟研究,将大大提高对滑坡等地质灾害的仿真分析,为滑坡灾害的预测与防治提供参考。 相似文献
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基于A.Nermoen的物理实验,文章进行了浅层气溢出过程数值模拟,区别于以往常用的欧拉-欧拉方法,文章采用了基于欧拉-拉格朗日方法的新型的离散粒子模拟方法MP-PIC（multiphase particle-in-cell）模型。揭示超压气体释放的机制,以及浅层气溢出过程中速度、压力的变化情况和变化规律。模拟得到的颗粒流化现象以及气泡的产生、运动和溢出现象与试验现象相一致,数模计算结果与实验资料两者相关度为0.94,相关性较好。临界流化速度和压力与土层的高度呈正相关,临界流化压力与实验结果较为接近,但由于马格努斯力（magnus）等作用力未考虑,导致临界流化速度相比于实验偏低。该模型方法能处理任意尺寸分布的颗粒,适用庞大的颗粒量,紧密耦合气固间相互作用,适用性好,准确性高,为数值模拟提供了便利。 相似文献
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光滑粒子流体动力学(SPH)由于无需网格生成和拉格朗日特性,对求解带有自由表面和大变形的力学问题有优势。但是该方法存在计算精度不高,计算效率较低等缺点。为此重点对SPH方法的精度提高进行研究。介绍了传统算法的基本公式,根据误差分析指出该算法精度不高的原因,提出了SPH二阶精度算法。通过精度验证分析,证明了该方法的精度的确能够达到二阶。通过二维计算实例,给出传统方法和二阶方法在粒子均匀分布和非均匀分布时函数值以及函数的一、二阶导数的误差分布,证明二阶算法能够克服传统算法的一些缺点,且计算精度有较大提高。 相似文献
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Smoothed particle hydrodynamics (SPH) is a meshfree, Lagrangian particle method which has advantages in handling solids with extremely large deformation. Like any other numerical methods, cares must be taken to ensure its desirable accuracy and stability through considering several correction techniques in calculation. The selection of values for parameters in those correction approaches is a key step in SPH simulation, which is always difficult for new beginners to deal well with effectively. This paper examines the common inconsistency and instability problems in SPH method and studies its computational efficiency when applied to hydrodynamics problems with material strength like soil column collapse. We analyzed in detail how the correction techniques mitigate these inconsistency and instability problems. Also, the numerical testing results associate with different values for the parameters used in the correction techniques are provided for better understanding the influence of these parameters and for finding out the desirable values. It is found that (1) the SPH method is easily subjected to an inconsistency problem in the boundary area due to the boundary deficiency, and it can be treated well by adopting “virtual particles” contributing to the particle summations. (2) The numerical oscillation in SPH simulation can be mitigated effectively by artificial viscosity with the suggested parameter values. (3) The tension cracking treatment, artificial viscosity and artificial stress work well in removing the tensile instability problem in SPH method. In addition, the nearest neighboring particle searching (NNPS) algorithm, spacing ratio, smoothing length and time step influence the efficiency and accuracy of SPH method significantly. It is shown that SPH method with suggested parameters values can produce a very good result compared with the experimental result. 相似文献
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A procedure for solving quasi‐static large‐strain problems by the material point method is presented. Owing to the Lagrangian–Eulerian features of the method, problems associated with excessive mesh distortions that develop in the Lagrangian formulations of the finite element method are avoided. Three‐dimensional problems are solved utilizing 15‐noded prismatic and 10‐noded tetrahedral elements with quadratic interpolation functions as well as an implicit integration scheme. An algorithm for exploiting the numerical integration procedure on the computational mesh is proposed. Several numerical examples are shown. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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The Finite Element Method (FEM) is widely used in the simulation of geotechnical applications. Owing to the limitations of FEM to model problems involving large deformations, many efforts have been made to develop methods free of mesh entanglement. One of these methods is the Material Point Method (MPM) which models the material as Lagrangian particles capable of moving through a background computational mesh in Eulerian manner. Although MPM represents the continuum by material points, solution is performed on the computational mesh. Thus, imposing boundary conditions is not aligned with the material representation. In this paper, a non-zero kinematic condition is introduced where an additional set of particles is incorporated to track the moving boundary. This approach is then applied to simulate the seismic motion resulting in failure of slopes. To validate this simulation procedure, two geotechnical applications are modelled using MPM. The first is to reproduce a shaking table experiment where the results of another numerical method are available. After validating the present numerical scheme for relatively large deformation problem, it is applied to simulate progression of a large-scale landslide during the Chi-Chi earthquake of Taiwan in which excessive material deformation and transportation is taking place. 相似文献
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首先讨论了Lagrangian和Eulerian无网格近似的联系和区别,然后基于稳定节点积分和增量本构理论,建立了分析边坡静动力破坏的高效大变形无网格法,并给出了详细的计算流程。该方法采用弹塑性损伤耦合本构关系来模拟岩土类材料的破坏演化过程,其中屈服函数采用Drucker-Prager准则,损伤准则为基于应变的各项同性损伤函数。由于无网格近似和稳定节点积分具有非局部近似的特性,在保证空间离散稳定性和提高计算效率的同时,也可准确有效地模拟应变集中所形成的剪切带的发生与扩展,通过数值算例验证了方法的有效性。 相似文献
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We have developed a new approach for the numerical modeling of deformation processes combining brittle fracture and viscous flow. The new approach is based on the combination of two meshless particle-based methods: the discrete element method (DEM) for the brittle part of the model and smooth particle hydrodynamics (SPH) for the viscous part. Both methods are well established in their respective application domains. The two methods are coupled at the particle scale, with two different coupling mechanisms explored: one is where DEM particles act as virtual SPH particles and one where SPH particles are treated like DEM particles when interacting with other DEM particles. The suitability of the combined approach is demonstrated by applying it to two geological processes, boudinage, and hydrofracturing, which involve the coupled deformation of a brittle solid and a viscous fluid. Initial results for those applications show that the new approach has strong potential for the numerical modeling of coupled brittle–viscous deformation processes. 相似文献
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The method of smoothed particle hydrodynamics (SPH) has recently been applied to computational geomechanics and has been shown to be a powerful alternative to the standard numerical method, that is, the finite element method, for handling large deformation and post‐failure of geomaterials. However, very few studies apply the SPH method to model saturated or submerged soil problems. Our recent studies of this matter revealed that significant errors may be made if the gradient of the pore‐water pressure is handled using the standard SPH formulation. To overcome this problem and to enhance the SPH applications to computational geomechanics, this article proposes a general SPH formulation, which can be applied straightforwardly to dry and saturated soils. For simplicity, the current work assumes hydrostatic pore‐water pressure. It is shown that the proposed formulation can remove the numerical error mentioned earlier. Moreover, this formulation automatically satisfies the dynamic boundary conditions at a submerged ground surface, thereby saving computational cost. Discussions on the applications of the standard and new SPH formulations are also given through some numerical tests. Furthermore, techniques to obtain the correct SPH solution are also proposed and discussed throughout. As an application of the proposed method, the effect of the dilatancy angle on the failure mechanism of a two‐sided embankment subjected to a high groundwater table is presented and compared with that of other solutions. Finally, the proposed formulation can be considered a basic formulation for further developments of SPH for saturated soils. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
18.
山东烟台夹河中、下游地区海水入侵三维水质数值模拟研究 总被引：17，自引：0，他引：17
建立了三维变密度对流弥散水质数学模型来研究山东省烟台夹河中、下游地区咸淡水界面的运移规律。以四面体为基本离散单元 ,推导出三维海水入侵变密度水质模型求解的数值方法 ,其中水流方程求解时运用了迦辽金有限单元法。溶质运移方程求解时运用了欧拉拉格朗日混合方法 ,将对流项与弥散项分离 ,用传统迦辽金有限元方法求解弥散项 ;采用自适应MOC MMOC法求解对流项 ,以消除人工过量和数值弥散。根据地下水的潮汐效应观测信息 ,确定了含水系统的海底延伸边界 ;利用该地区地下水水头及水质长观资料识别了模型的水文地质参数 ,探讨了夹河地区海水入侵的原因 :认为夹河下游地区滨海地带地下水过量开采是造成烟台地区海水入侵的主要原因。此外 ,海水随潮定期地倒灌进入夹河 ,通过局部岩性天窗侵入淡水含水层加剧了沿夹河河床两侧地下水的咸化。同时还预测了几种情况下地下水的水质演化趋势 ,为防止和减轻夹河地区海水入侵提供合理、科学的依据。 相似文献
19.
M. B. Liu G. R. Liu K. Y. Lam Z. Zong 《Fragblast: International Journal for Blasting and Fragmentation》2003,7(3):181-202
Shaped charges are widely applied in the defense industry and civil engineering for penetrating hardened targets. Simulations of shaped charges are generally based on traditional grid-based numerical methods. Different from the existing literature, the SPH method is applied in this paper to simulate the detonation process of shaped charge explosive. The combination of the meshless, Lagrangian and particle nature inherent in the SPH method is very attractive in dealing with large deformations and large inhomogeneities in extremely transient situations such as detonation process. The SPH method and some related numerical aspects are briefly discussed first, followed by applications in simulating shaped charge detonations. The effects of different detonation cavity angles and different charge head lengths are investigated. The results demonstrate that major shaped charge detonation phenomena are captured with revealing observations. 相似文献