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531.
小水线面双体船粘性流数值模拟 总被引:2,自引:0,他引:2
利用商业软件FLUENT对一小水线面双体船(SWATH)的粘性绕流进行数值模拟,得到了不同航速下的三维粘性流场和粘性阻力,通过对计算结果的分析、比较,验证了FLUENT用于预报小水线面双体船粘性阻力和伴流分布的有效性和实用性。 相似文献
532.
土体渗透性是影响砂井地基固结的重要因素。为研究复杂条件下砂井地基的固结性状,通过编制用户子程序在ABAQUS中建立了渗透系数沿径向变化的砂井地基固结计算数值模型,对固结过程中的孔压分布及固结性状进行了研究。结果表明:渗透系数在径向上的变化情况会对砂井固结性状产生很大的影响。假定涂抹区渗透系数为常数时固结速率最慢;假定涂抹区渗透系数呈抛物线变化时固结速率最快;而假定涂抹区渗透系数呈线性变化时固结速率介于以上两种情况之间。此外,砂井地基的固结性状还受排水条件和土层特性等因素的影响。 相似文献
533.
根据兰渝铁路毛羽山隧道出口开挖过程中出现严重大变形的工程实例,利用FLAC3D建立三维数值模型,对不同台阶长度、仰拱闭合时机、锚杆长度以及二次衬砌浇筑时机的隧道施工进行了动态模拟。计算结果表明:台阶长度对大变形控制至关重要,应尽可能减小上台阶长度,采用超短台阶法施工;仰拱对于挤压性围岩隧道大变形控制具有显著的效果,应尽早封闭成环;随着锚杆长度的增加,隧道变形逐渐减小,但是当其长度大于8m时,再增加锚杆长度对控制大变形所起作用不明显;开挖后立即施作二次衬砌,可有效控制围岩蠕变变形。 相似文献
534.
公路隧道二次衬砌纵向裂缝非线性数值模拟研究 总被引:1,自引:1,他引:1
已建隧道普遍存在衬砌开裂现象,裂缝的存在会降低隧道衬砌的承载能力.文章为研究带裂缝隧道衬砌的力学性能,提出了塑性地压、松弛土压、偏压等三种受力裂缝数值模拟的荷载施加模式;分析了几种常见裂缝模型的原理及适用性,并且基于钢筋混凝土有限元非线性分析理论,利用分布裂缝模型进行不同荷载模式下隧道二次衬砌开裂至破坏的全过程分析;通过计算得出了不同加载方式下裂缝的发展及分布规律.研究结果可为隧道衬砌裂缝成因判断及二次衬砌加固改造提供理论支撑. 相似文献
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Recently, the fatigue failure of ship rudders owing to vortex-induced vibration has increased as commercial ships become faster and larger. However, previous methods are inappropriate for fatigue failure prevention owing to the lack of fluid–structure interaction considerations. This study aims to develop a fatigue damage prediction method that can be applied at the design stage to prevent fatigue failure of ship rudders under vortex-induced vibration. The developed prediction method employed the fluid–structure interaction (FSI) method to properly consider the fluid–structure interaction and implemented orthonormal mode shapes to reflect the complex geometry and boundary conditions of the ship rudders. For validation, vortex-induced vibration of the hydrofoil model was obtained using the developed method, and the prediction results matched well with the experimental results. Then, the fatigue damage of the ship rudder model under vortex-induced vibration was predicted using the developed method, and their characteristics are discussed. The stress distribution obtained using the developed method matched well with the geometrical characteristics of the ship rudders. The potential for fatigue failure due to the resonance of vortex-induced vibration was expected by comparing the stress distributions for various flow velocities to the S–N curves provided by the DNV classification. 相似文献
539.
Innovative monopile-wheel hybrid foundations are proposed to enhance the lateral load and moment capacities of monopile for offshore wind systems. This paper presents a comprehensive numerical study on the bearing capacities of this hybrid foundation in clay-overlaying-sand soil conditions under combined V–H-M (vertical-horizontal-moment) loadings. Numerical models are generated and validated by comparing with laboratory experiment results and available centrifuge testing data on similar foundation systems. Parametric analysis is then carried out to quantify the effects of potential influencing factors on the failure mechanisms and bearing capacities of hybrid foundations, including the hybrid foundation geometry, soil properties, upper clay thickness, height of the lateral loading and pre-vertical load. It is found that in clay-overlaying-sand deposits, the hybrid system manifests totally different failure mechanism compared with that in uniform soil deposits. The thickness of the upper clay layer (Tc/L), within the practical range of Tc/L = 0.1–0.7, has a significant influence on the failure patterns and the bearing capacities of the hybrid system, and the proportion of bearing capacity provided by the pile and wheel is determined by the ratios of Dw/L and L/Dp. In addition, the failure envelopes in the V–H-M space manifests that the failure envelopes are shrank with the increase of the normalized vertical resistance, V/Vult, which is highly related to the clay layer thickness (Tc/L). 相似文献
540.
This paper reviews the importance of uncertainties in hull girder loads influenced by flexible fluid structure interactions. The focus is on developments in the field of hydroelastic modelling, simulation and model tests of practical relevance to the prediction hull girder wave load predictions and their validation. It is concluded that whereas hydroelastic methods for use in design development and assessment become increasingly useful, challenges in realizing and modelling uncertainties can be attributed to: (1) the limitations of numerical methods to suitably model nonlinearities; (2) the ambiguity of model tests; and (3) the systematic use of data emerging from computational, model- or full-scale methods. An approach is recommended to assess the uncertainty in the hydroelastic responses to wave loading and an example is provided to demonstrate the application of the procedure. 相似文献