共查询到20条相似文献,搜索用时 15 毫秒
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Sang Hoon Lee Hyoung Gwon Choi Jung Yul Yool 《Journal of Mechanical Science and Technology》2012,26(5):1355-1361
Numerical simulations for the blood flow are carried out to investigate the effect of the flexible artery wall on the flow field and to determine the wall shear stresses in the carotid artery wall. To solve the equation of motion for the structure in typical fluid-structure interaction (FSI) problems, it is necessary to calculate the fluid force on the surface of the structure explicitly. To avoid complexity due to the necessity of additional mechanical constraints, we use the combined formulation including both the fluid and structure equations of motion into a single coupled variational equation. The Navier-Stokes equations for fluid flow are solved using a P2P1 Galerkin finite element method (FEM) and mesh movement is achieved using arbitrary Lagrangian-Eulerian (ALE) formulation. The Newmark method is employed to solve the dynamic equilibrium equations for linear elastic solid mechanics. The time-dependent, three-dimensional, incompressible flows of Newtonian fluids constrained in the flexible wall are analyzed. The study shows strongly skewed axial velocity and flow separation in the internal carotid artery (ICA). Flow separation results in locally low wall shear stress. Further, strong secondary motion in the ICA is observed. 相似文献
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Kameda Y 《Microscopy research and technique》2002,59(3):196-206
In the bird the carotid body is located between the distal (nodose) ganglion of the vagus nerve and the recurrent laryngeal nerve at the beginning of the common carotid artery, that is, the organ is located at the cervicothoracic border. The chicken carotid body receives numerous branches from the vagus and the recurrent laryngeal nerves. In addition, dense networks of the peptidergic nerve fibers immunoreactive for substance P, calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide (VIP), galanin, and neuropeptide Y (NPY) are distributed in and around the carotid body parenchyma. The substance P- and CGRP-immunoreactive fibers are derived from both the superior and inferior ganglia of the vagus nerve. The VIP-, galanin-, and NPY-immunoreactive fibers originate from the 14th cervical ganglion of the sympathetic trunk. The endocrine organs including the thyroid gland, parathyroid glands, carotid body, and ultimobranchial gland are situated as a continuous series along the common carotid artery. The organs are supplied with arteries arising as one trunk from the common carotid artery. Glomus cells are widely distributed not only in the carotid body but also in the wall of the common carotid artery and around the common trunk and its branches. The glomus cells of the chicken carotid body exhibit intense immunoreactivity for serotonin, tyrosine hydroxylase, and chromogranin A. The cells located in the wall of the common carotid artery further express NPY mRNA and peptide. In the chickens exposed to isocapnic hypoxia for 35 days, 3-4-fold increase of the carotid body volume is induced and the carotid body glomus cells show enhanced synthetic and secretory activities. On the other hand, the cells in the wall of the common carotid artery display little changes after the long-term hypoxia, having different functions from the carotid body. The carotid body rudiment is formed in the lateral wall of the third branchial artery. The neural cells immunoreactive for TuJ1, PGP 9.5, and HNK-1, which are continuous with the inferior vagal (nodose) ganglion, first surround and then invade both the carotid body rudiment and the other portions of the third branchial artery, becoming glomus cells. 相似文献
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针对沿海地区配电线路抵御强台风能力不足的问题,对10k V配电线路抗台风的能力进行了数值研究,讨论了地基土与防风拉线对电杆防风能力的影响。采用ABAQUS/CAE建立了10k V单回路配电线路一个标准段的有限元模型,模型中包括导线、混凝土电杆、横担、拉线和地基土等;利用等效惯性加速度模拟线路所受风荷载,然后对模型在不同等级风速下进行了变形分析,通过数值解与理论解的对比,验证了数值模型的正确性。研究了3类线路的弯矩、扰度和应力等问题的变化规律,包括:考虑地基土作用、考虑拉线加固处理以及两者都没考虑的3类模型。研究结果表明,土体变形对电杆的扰度变化有叠加效应,安装拉线加固后电杆最大弯矩明显降低。 相似文献
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剪切力对动脉血管平滑肌细胞增殖分化的影响 总被引:2,自引:0,他引:2
目的:探讨剪切力作用下人脐动脉血管平滑肌细胞的增殖分化的变化。方法:利用改进的灌流及流动培养装置,通过蠕动泵提供稳定的剪切力,同时提供静态培养所需的其它条件,建立体外人脐动脉血管平滑肌流动培养模型。分别对体外培养的人脐动脉血管平滑肌细胞加载3,4,5,8,10dyn/cm^2的定长流剪切力24h,同时以静态培养的细胞为对照组。相差倒置显微镜观察玻片上细胞的数量并作细胞计数,α—actin免疫组化染色.结果:细胞记数显示,同对照组相比,七刀应力各组的增殖能力都有所下降,5dyn/cm^2切应力作用下,细胞增殖缓慢最为明显.α—actin免疫组化染色提示切应力各组的分化程度较对照组高。结论:初步研究表明,剪切力对人脐动脉血管平滑肌细胞的增殖有一定抑制作用,并且可能促进了细胞的分化。 相似文献
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This paper presents a pre-verifiable calibration model, which can accurately characterize the measurement behavior of the flexible wall shear stress thermal sensor in constant current drive mode. In this calibration model, the fitting parameter can be pre-verified with , which provides a method to verify the accuracy of calibration instruments and data. In repetitive experiments, the average related normalized standard deviation is 1.26%, which indicates that our calibrations are reliable. And the relative deviations between and are below 1.15% in all experiments, which indicates that the calibration model can pre-verify the reliability of calibration instruments and data among different sensors and different drive currents. 相似文献
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Yuanqiang Tan Hao ZhangDongmin Yang Shengqiang JiangJunhua Song Yong Sheng 《Tribology International》2012,46(1):137-144
A numerical simulation has been conducted to study the solid-fluid multi-phase flow problem in concrete pumping process. The kinematics and trajectory of the discrete particles as well as the particle-particle interaction were predicted by DEM while the motion of the continuous fluid phase was evaluated by a Navier-Stokes solver, and a pressure gradient force model was adopted to calculate the solid-fluid interaction force. A case of pneumatic conveying was utilized to demonstrate the capability of the coupling model. The concrete pumping process was then simulated, where several flow features were observed such as roping, particle segregation and particle concentration. The frequency of the particles impacting on the bended pipe was monitored, a new time average collision intensity model based on impact force has been proposed to investigate the wear mechanism of the elbow. The location of maximum erosive wear damage in the elbow was predicted. Statistical results were in good agreement with that observed in actual pumping process. It is found that the present multi-phase coupling model can predict the wear behavior of the bended pipe accurately, and consequently provide an effective guidance for the design of concrete pumping pipe. 相似文献
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Shaohui Wang Zhongyi Cai Mingzhe Li Yingwu Lan 《The International Journal of Advanced Manufacturing Technology》2012,60(9-12):901-911
Multi-point stretch forming (MPSF) is a new flexible forming technique to form aircraft outer skin parts. The multi-point stretching die (MPSD) replaces the traditional fixed shape stretching die, and the sheet metal is formed over a MPSD composed by the punch element. The MPSD is a discontinuous surface of discrete stretching die, and the stress concentration and local strain occur on formed parts. These lead to generate dimples on the surface of formed part. In this paper, a series of numerical simulations on MPSF processes for stretching parabolic cylindrical, spherical, and saddle-shaped parts were carried out. The local stress and local strain in thickness distribution of MPSF part were analyzed by dispersed the blank into solid elements. The forming results of MPSF were compared with those that use traditional stretch forming, and the influences of thickness of elastic cushion and the size of punch element on the stress concentration and local strain were surveyed. The simulation results show the distribution of local stress and local deformation in different layers, and the elastic cushion and the small size of punch element can reduce the stress concentration and local deformation. The results may understand the stress distribution on the sheet and prevent the defect of dimple. 相似文献
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钛及其合金应用越来越广泛,目前单点渐进成形技术已经开始运用于钛及其合金的成形加工,但仍存在成形件壁厚过度减薄的问题,严重影响了成形件的成形质量。文章以TA1钛合金板材成形方锥形件为研究对象,运用Abaqus有限元仿真软件,依据单一变量原则,分别探究工具头直径、底面边长、板材原始厚度和螺距等工艺参数对成形件平均壁厚减薄率与最大壁厚减薄率的影响规律。结果显示:增大工具头直径,平均壁厚减薄率随之增大,最大壁厚减薄率随之减小;平均壁厚减薄率和最大壁厚减薄率都随着底面边长的增加而增加;板材原始厚度增加,平均壁厚减薄率与最大壁厚减薄率都随之减小;随着螺距的增加,平均壁厚减薄率逐渐减小,最大壁厚减薄率逐渐增大。 相似文献
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固液两相流离心泵内颗粒运动规律的数值研究 总被引:1,自引:0,他引:1
《机电工程》2015,(12)
针对分析固相参数对颗粒在流道内运动规律影响的问题,对不同固相参数工况下流道内颗粒运动轨迹、固相速度分布和颗粒雷诺数分布规律进行了研究,对颗粒直径以及颗粒浓度对颗粒运动规律影响进行了归纳。应用RNG k-ε湍流模型以及离散相模型进行了离心泵内部固液两相流场数值模拟。研究结果表明,颗粒与蜗壳碰撞的次数随着直径和颗粒浓度的增大而减少;叶轮流道内,颗粒与叶片发生碰撞的位置在叶片工作面;流道内的固相速度随着直径的增大整体会有减小的趋势;蜗壳和叶轮流道内两相分离严重,两相滑移速度较大。 相似文献
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Thermo-fluid mechanical characteristics as well as flame structure of a pool fire were numerically simulated in this study.
The small scale pool fire was treated as a gaseous jet flame with low initial velocity as an approximation. The combustion
model postulated infinitely fast chemical reaction and the soot formation model included soot nucleation, surface growth,
coagulation, thermophoresis, and oxidation. Valuable data were obtained in the temperature distribution, velocity profiles,
soot volume fraction and major species concentrations. Especially, the periodic formation of the large scale structures were
successfully simulated. Its frequency agreed well with experimental results.
Research Institute of Industrial Science and Technology Heat and Fluid Flow Research Team 相似文献
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I P Chua S C Yu Q Xue 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2001,215(5):503-514
Most patients with atherosclerosis exhibit isolated stenoses of one or more epicardial coronary arteries. The wall shear stresses produced in high-grade stenosis are important in the understanding of atheromatous plaque rupture and thrombosis. This study is designed to establish a method which can be used to scale the different wall shear stresses obtained under different flow conditions to be normalized and subsequently collapsed on to a single general curve. The simulations include both steady and pulsatile flow. The reduced area percentages of the stenoses studied are 50, 75 and 90 per cent. Scaling laws for steady and pulsatile flow conditions are proposed and presented. It can be found from the results that the scaling analysis for pulsatile flow conditions is more complicated than for steady flow conditions and is restricted to, and only valid at, certain time intervals. 相似文献
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Ocular pneumoplethysmography in carotid artery disease 总被引:2,自引:0,他引:2
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A silicon-based micro-machined, floating element sensor for wall shear-stress measurement has been developed. Sensor with the dimension of 4×3×0.5 mm3 has been fabricated by inductively coupled plasma (ICP) etching techniques with single mask. An optical system was designed to identify whether there is defect in the structure of the fabricated sensor. Detection of the floating element motion induced by shear stress of fluid is accomplished using differential capacitance measurement. A special package was used to reduce the parasitic capacitance and realize flush mounted between the sensor and the wall. Calibration tests were carried out in a laminar flow channel; the result indicates that the sensitivity of the sensor is measured to be 27 mv/Pa. The measured non-linearity is less than 3.4% while the repeatability is within 4.9% in the regime of 0–35 Pa. 相似文献
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Maodan Yuan To Kang Jianhai Zhang Sung-Jin Song Hak-Joon Kim 《Journal of Mechanical Science and Technology》2013,27(11):3207-3214
A number of interesting phenomena at fluid-solid interfaces can be observed when the incident angle approaches the Rayleigh angle, including Schoch displacement and leaky Rayleigh waves. Besides the experimental and theoretical research on these problems, numerical tools have been more and more widely used for these complex problems. Based on previous experimental and numerical researches, a 2D finite element model has been built to reproduce the Schoch effects. With the same model, the minimum reflection profile is investigated for the feasibility of material characterization, especially for residual stress evaluation. Residual stress is one of the important properties for structures, and its measurement is a popular research topic in nondestructive evaluation. However, it is not possible to put the residual stress into the numerical model directly. According to the relation of residual stress with mechanical properties, the material damping and wave speed have been alternatively adopted in this work. The influence of minimum reflection profile by residual stress has been shown by the change of wave speed and damping factor. Simulation results show that the minimum reflection profile is a potential method for residual stress evaluation. 相似文献