共查询到20条相似文献,搜索用时 203 毫秒
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后验概率算法用于位移场的确定 总被引:1,自引:0,他引:1
提出了一种基于贝叶斯最大后验估计算法确定固体表面位移场的方法。在图像处理过程中,把位移看作随机变量,首先建立贝叶斯模型,对变形前数字图像中的一个像素点,选定变形前后两幅数字图像中对应的圆形子区,将两子区所对应的所有可能位移逐一代入贝叶斯后验概率公式进行计算,使后验概率最大的位移值就是所求该点的位移。在得到整像素位移之后,引入亚像素重建技术,确定图像的精确位移场。本文通过计算机数字模拟实验和实物标准位移实验,验证了该方法的可行性,并得到了0.02pixel的位移测量精度。 相似文献
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超声散斑数字相关法应用于体面内转动测量的研究 总被引:1,自引:0,他引:1
在激光数字散斑相关法测量理论的基础上,阐述了超声散斑相关法测量的基本原理,并建立了相应的超声散斑数字相关实验分析系统。在实验分析时,首先应用模拟测量的方法对刚体面内转动对散斑场相关性的影响进行了分析;然后应用实验测量的方法再对此进行了分析;最后对刚体未知面内转角进行了实测。实验结果表明,刚体面内转动可测量的最大转角为9°,当转动角度为10°时,误差大于9%。实验中分别应用了爬山搜索法和相关系数拟合法来分别搜索整像素的位移和亚像素的位移。 相似文献
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含可动机构的杆系结构非线性力法分析 总被引:6,自引:0,他引:6
推导了基于矩阵奇异值分解的小变形条件下杆系结构的力法分析(LFM)过程,并采用杆件内力修正的方法,提出了考虑大位移的几何非线性力法分析(NFM)方法思想和步骤。该方法有效地解决了结构中同时存在刚体位移、弹性位移的结构分析问题,适合计算机编程,结构的强度计算、机构分析和形态分析,讨论了力法与位移法的优缺点,给出的算例表明所提出的方法是正确的、有效的。 相似文献
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本文基于多刚体-弹簧系统模型,给出了求解平面刚架结构弹塑性、大位移极限承载力分析的多刚体离散元法。文中首先推导了多刚体离散元法在总体坐标下的切线刚度阵,建立多刚体元法的增量平衡方程。 相似文献
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Despite the increase in horizontal well applications, scaling fluid displacement in porous medium with horizontal wells is
yet to be fully investigated. Determining the conditions under which horizontal wells may lead to better oil recovery is of
great importance to the petroleum industry. In this paper, a numerical sensitivity study was performed for several well configurations.
The study is performed in order to reveal the functional relationships between the scaling groups governing the displacement
and the performance of immiscible displacements in homogeneous reservoirs produced by horizontal wells. These relationships
can be used as a quick prediction tool for the fractional oil recovery for any combinations of the scaling groups, thus eliminating
the need for the expensive fine-mesh simulations. In addition, they provide the condition under which a horizontal well configuration
may yield better recovery performance. These results have potential applications in modeling immiscible displacements and
in the scaling of laboratory displacements to field conditions. 相似文献
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We describe scale up of geological models of field-scale porous media using a new method based on the wavelet transformations. The porous media of interest contain broadly-distributed and correlated permeabilities. Wavelet transformation of the permeability field of such porous media coarsens the geological model from smallest to largest length scales, drastically reduces the number of equations to be solved, preserves the important information on the permeability field at all the relevant length scales, and yields numerical results for any fluid flow property that are as accurate as those that are obtained with the highly detailed geological model of the same porous media. To test this method, we carry out extensive computer simulations of unstable miscible displacement processes and the associated viscous fingering phenomenon in highly heterogeneous porous media, both with the fine-scale geological model and the coarsened model. Excellent agreement is found between the results of the two sets of simulations. 相似文献
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医学界为攻克脊柱压缩性骨质疏松难题,试图应用一种钢质网状可变球型(简称GWQ)机构,将其植入人体脊椎,通过有效变形达到支撑已经压缩的脊椎、恢复人体原高度之目的。针对该机构目前没有力与位移定量关系的现状,本文自行设计制作了GWQ测量传感器,将机构的空间受力问题转化为悬臂梁的弯曲变形问题,定量讨论了机构在三维空间不同位移约束条件下,各方向力与位移的关系,确定了机构三维空间中最优的工作方向,得出了驱动力与该方向上位移的关系曲线。结果表明在机构所置三维空间中,要使其工作效率最高,应选取y向为工作方向(沿脊柱方向),z向为施加外力方向。x、y向初始距离的比值n应大于0.8,驱动力一定时,工作力与n成正比。驱动力Fz与Z向位移Δlz成正比关系,但其变化率随Δlz的增大而减小。临床应用时可根据对该位移的监测实现对驱动力的控制。 相似文献
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有界不确定参数结构位移范围的区间摄动法 总被引:20,自引:0,他引:20
当结构参数具有误差或有界不确定性时,区间数学可以在不同知识不确定变量的概率分布的情况下定量地考察不确定参数对结构响应的影响。为计算出不确定结构参数对结构位移影响范围的上下界,文中提出了的两种区骚动国方法。 相似文献
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Displacement of a viscous fluid by a lower viscosity immiscible fluid (such as waterflood of a viscous oil) in a porous medium is unstable. The displacement front generates viscous fingers which lead to low oil recovery efficiency. These fingers are much smaller in width than typical reservoir simulation grid blocks, and capturing their effect in reservoir simulation is important. A dimensionless scaling group (viscous finger number) had been suggested in the past, which has a power-law relationship with the breakthrough recovery and cumulative recovery in unstable core floods. The relative permeability used in large grid block simulations had been modified to so-called pseudo-relative permeability on the basis of the dimensionless group, thus incorporating the effect of fingers in waterflood predictions. However, the previous proposed models were constructed from experiments in only water-wet rocks. This paper extends the recent viscous fingering models to oil-wet systems. Sandstone cores were treated to alter the wettability to oil-wet. Adverse viscosity water floods were performed in oil-wet cores. Viscosity ratio, velocity and diameter were varied. It is shown that the previously developed viscous finger number does not work for the oil-wet experiments. The correlating dimensionless number is modified for oil-wet systems; it is also different from the dimensionless group identified by Peters and Flock (Soc Petroleum Eng, 1981. doi: 10.2118/8371-PA) for oil-wet cores. A pseudo-relative permeability model has been developed for oil-wet cores. Corefloods have been matched by the new pseudo-relative permeability model to determine the model parameters. This pseudo-relative permeability model can be used in reservoir simulations of water and polymer floods in viscous oil-wet reservoirs. 相似文献
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Understanding and predicting the performance of solvent drives and remediation of contaminated aquifers in heterogeneous reservoirs is of great importance to the petroleum and environmental industries. In this paper, a general method to scale flow through heterogeneous reservoirs is presented for a miscible displacement of oil by a solvent. Results show that scaling miscible displacements in a two-dimensional, heterogeneous, anisotropic vertical cross section requires the matching of 13 dimensionless scaling groups. These groups were derived using a general procedure of inspectional analysis. A detailed numerical sensitivity study was performed to reveal the relationship between the scaling groups and the fractional oil recovery of miscible displacements in heterogeneous reservoirs. This relationship was then mapped using an artificial neural network, which can be used as a quick prediction tool for the fractional oil recovery for any combinations of the scaling groups, thus eliminating the need for the expensive fine-mesh simulations. These results have potential applications in modeling miscible displacements and in the scaling of laboratory displacements to field conditions. 相似文献
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In this work, we investigate the accuracy of some physical models that are frequently used to describe and interpret dispersive mixing and mass transfer in compositional reservoir simulation. We have designed a quaternary analog fluid system (alcohol?Cwater?Chydrocarbon) that mimics the phase behavior of CO2-hydrocarbon mixtures at high pressure and temperature. A porous medium was designed using PolyTetraFlouroEthylene (PTFE) materials to ensure that the analog oil acts as the wetting phase, and the properties of the porous medium were characterized in terms of porosity, permeability and dispersivity. Relative permeability and interfacial tension (IFT) measurements were also performed to delineate interactions between the fluid system and the porous medium. The effluent concentrations from two-component first-contact miscible (FCM) displacement experiments exhibit a tailing behavior that is attributed to imperfect sweep of the porous medium: A feature that is not captured by normal dispersion models. To represent this behavior in displacement calculations, we use dual-porosity (DP) models including mass transfer between flowing and stagnant porosities. Two 4-component two-phase displacement experiments were performed at near-miscible and multicontact miscible (MCM) conditions and the effluent concentrations were interpreted by numerical calculations. We demonstrate that the accuracy of our displacement calculations relative to the experimental observations is sensitive to the selected models for dispersive mixing, mass transfer between flowing and stagnant porosities, and IFT scaling of relative permeability functions. We also demonstrate that numerical calculations substantially agree with the experimental observations for some physical models with limited need for model parameter adjustment. The combined experimental and modeling effort presented in this work identifies and explores the impact of a set of physical mechanisms (dispersion and mass transfer) that must be upscaled adequately for field-scale displacement calculations in DP systems. 相似文献
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During two-phase flow in porous media, non-wetting phase is present simultaneously in states of mobile connected continuum and of trapped isolated ganglia. Mass exchange between these two parts of non-wetting phase is going on by dissolution and diffusion of component in the wetting phase, so, compositions of non-wetting phase in both parts are different. Nevertheless, the traditional mathematical model for two-phase multicomponent transport in porous media assumes the homogeneous distribution of each component in the overall non-wetting phase. New governing equations honouring ganglia of non-wetting phase are derived. They are successfully verified by a number of laboratory tests. Analytical model is developed for miscible water-alternate-gas (WAG) displacement of oil-condensates. The modelling shows that the significant amount of oil-condensate is left in porous media after miscible WAG, while the traditional model predicts that the miscible displacement results in the total sweep. 相似文献