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车-人碰撞事故中行人胫骨撞击响应的二维数值分析   总被引:1,自引:0,他引:1  
目的基于两相多孔弹性胫骨模型,建立一种车-人碰撞事故中行人胫骨撞击响应的二维数值分析方法。方法选用健康成年男性胫骨行CT分层扫描,结合数值插值方法获得胫骨的结构参数;在两相饱和多孔弹性理论的框架内,建立胫骨动力学控制方程组;采用自行开发的流-固耦合两相多孔介质有限元数值分析程序,数值模拟小汽车车头从侧向撞击行人下肢的动力学过程,并计算撞击载荷作用下0-200ms内行人胫骨的动力学响应。结果胫骨的弯曲变形主要集中在撞击载荷作用的区域;胫骨骨干上节点107处的侧向位移响应,约在75ms时刻出现峰值位移(-6mm),对撞击载荷有明显的时间滞后;胫骨骨干上单元E77中心处的轴向应力响应,约在30ms时刻出现峰值应力(140MPa),对撞击载荷也有明显的时间滞后。结论本研究所建立的对车-人碰撞事故中行人胫骨撞击响应的二维数值分析方法,能够近似地模拟胫骨撞击区的弯曲变形、侧向位移响应和轴向应力响应以及胫骨中骨髓流体组分对骨架固体组分动力学特性的影响。下一步研究将在现有初步结果的基础上提高胫骨动力学模型的生物仿真性。  相似文献
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In this paper the theory of mixtures is used to develop a two-phase model of an avascular tumour, which comprises a solid, cellular, phase and a liquid phase. Mass and momentum balances which are used to derive the governing equations are supplemented by constitutive laws that distinguish the two phases and enable the stresses within the tumour to be calculated. Novel features of the model include the dependence of the cell proliferation rate on the cellular stress and the incorporation of mass exchange between the two phases. A combination of numerical and analytical techniques is used to investigate the sensitivity of equilibrium tumour configurations to changes in the model parameters. Variation of parameters such as the maximum cell proliferation rate and the rate of natural cell death yield results which are consistent with analyses performed on simpler tumour growth models and indicate that the two-phase formulation is a natural extension of the earlier models. New predictions relate to the impact of mechanical effects on the tumour's equilibrium size which decreases under increasing stress and/or external loading. In particular, as a parameter which measures the reduction in cell proliferation due to cell stress is increased a critical value is reached, above which the tumour is eliminated.  相似文献
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研究麻醉蒸发器的多孔介质蒸发芯物理特性对蒸发的影响,为优化改进蒸发器结构提供理论依据,提高药物控制精度。通过实际测量麻醉蒸发器,用Pro/E软件建立了三维结构模型,采用CFD方法,利用FLUENT软件分析多孔介质物性对蒸发器工作性能以及麻醉药物蒸发与空气混合情况的影响。在计算分析中采用湍流随机跟踪方法,对麻醉药物蒸发雾滴在多孔介质区域的运动进行轨迹追踪,得到了蒸发器多孔介质区域内气体速度场变化,麻醉药物挥发以及与稀释气体混合过程中浓度场变化等。结果表明,多孔介质孔隙率、流动阻力对药物蒸发以及药物蒸气与稀释气体混合过程有较大影响,最终影响蒸发药物浓度的稳定性与精确性。多孔介质的存在减缓了蒸发器内部稀释气体的流动速度,使流动阻力增加。多孔介质的孔隙率越大药物的蒸发量与稀释气体的混合均匀性越高。并且在多孔介质区域内存在挥发吸热过程,需要根据药物最大蒸发量来确定温度补偿范围,以确保麻醉蒸发器药物浓度输出的稳定性和精确性。  相似文献
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中空纤维管透析器是人工血液透析等设备的质交换部件,其内部流体的浓度会发生变化,一般认为密集分布的纤维管能抑制管间流体的浮力作用.通过三维数值模拟,研究中空纤维透析器内流体在重力场中的流动,探讨浮力对流的存在条件及其对透析的影响.计算基于双多孔介质模型,纤维膜传质采用K-K方程描述,用计算流体软件FLUENT进行数值求解.结果表明,抑制浮力引起的对流并不是无条件的,需要综合考虑纤维管填充密度、血液入口浓度和透析液入口流量等因素.当纤维管分布密度低于临界值时,浮力作用是显著的;当高于临界值时,浮力作用是可以忽略的.该临界值与透析液流量和溶质浓度有关.本研究对于分析中空纤维透析器的透析传质过程具有理论意义.  相似文献
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The human finger is said to be the extension of the brain and can convey the information on mechanical, thermal, and tissue damaging. The quantitative prediction of blood flow rate and heat generation are of great importance for diagnosing blood circulation illness and for the noninvasive measurement of blood glucose. In this study, we developed a coupled thermofluid model to simulate blood flow in large vessels and living tissue. The finite element (FE) model to analyze the blood perfusion and heat transport in the human finger was developed based on the transport theory in porous media. With regard to the blood flow in the large arteries and veins, the systemic blood circulation in the upper limb was modeled based on the one-dimensional flow in an elastic tube. The blood pressure and velocity in each vessel were first computed and the corresponding values for the large vessels in the finger were subsequently transferred to the FE model as the boundary conditions. The realistic geometric model for the human finger was constructed based on the MRI image data. After computing the capillary pressure and blood velocity in the tissue, the temperatures in the large vessels and the tissue of the finger were computed simultaneously by numerically solving the energy equation in porous media. The computed blood flow in tissues is in agreement with the anatomical structure and the measurement. It is believed that this analysis model will have extensive applications in the prediction of peripheral blood flow, temperature variation, and mass transport.  相似文献
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In three-dimensional numerical studies of the aorta, it is difficult to apply proper boundary conditions at the end of each major aortic branch because of interactions between blood and organs. Organs and body parts were assumed to be likened to cylindrically shaped porous media, so-called pseudo-organs, and treated in the computational domain as forms of hemodynamic resistance. Permeability functions were determined from two-dimensional axisymmetric computations of each aortic branch and these functions were then used in an unsteady three-dimensional simulation of the complete aorta. Substantially accurate cardiac output (5.91 L/min) and blood distributions to the major branches were predicted.  相似文献
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目的在软骨数值模拟中,对由于设置均匀和随深度变化的力学参数而导致的结果差异进行评估。方法利用COMSOL多孔介质模块建立软骨非线性两相多孔介质模型。在静载荷下,分别用均匀和随深度变化的两种软骨力学参数对模型进行了计算,并对两者的计算结果差异进行了分析。结果对于软骨总应力,两种参数设置的结果之间差异很小。但在分析软骨的固相应力、液体压力和流动等较深入细致的问题时,两种参数设置结果之间的差异不能忽略。结论不同的软骨力学参数设置对软骨总应力的结果几乎没有影响,但对软骨内流速场则影响很大。所以均匀的力学参数设置可用来简化计算软骨总应力的问题,而其他一些更细致的分析需要立足于随深度变化的软骨力学参数。这些结论可以为今后的软骨建模和数值计算提供参考,为人工关节的设计和计算奠定基础。  相似文献
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