共查询到17条相似文献,搜索用时 281 毫秒
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在血管壁施加第三类边界条件是计算血液与组织间对流换热的一种近似计算方法.为分析其可行性,用有限元数值模拟方法计算血管分支结构中血液与组织的对流换热,得到不同流速和半径下分支血管内血液的截面平均Nu数沿管长的变化曲线.结果表明,血管树中分支血管的Nu数变化幅度不大,且趋于稳定值的速度很快.以相同边界条件下包含简单血管系统的舌体为例,分别用近似方法和完全耦合计算方法,进行血液流场和舌体温度场模拟.通过比较计算结果,得出两种方法得到的温度场分布趋势基本相同;用完全耦合计算方法得到的舌体温度略高于用近似方法得到的舌体温度,两者差值小于0.2℃. 相似文献
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激光诱导间质热疗疗效评估的前提是必须获得准确的激光在不同功率、不同照射时间的生物组织温度场分布.利用多物理场直接耦合分析软件COMSOL Multiphysics构建了在组织光学参量不变情况下的三维有限元传热模型.该模型基于Pennes生物传热方程和轴对称高斯形状的激光光束热源方程,参量针对离体猪肝组织,考虑到了生物组织热物性密度、比热和热导率随温度变化的情况.仿真获得激光功率为0.77 W、0.95 W、1.23 W,照射时间为10~90 s,径向距离0~2 mm范围和轴向距离0~4 mm范围的温度场数据集.利用拟合算法,获得了自变量为激光功率、照射时间、径向距离和轴向距离的生物组织温度场分布模型.将功率为0.88 W和1.05 W时的结果与Pennes方程结果相比较,两者误差在5%以内. 相似文献
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为考察基于时间反转方法的高强度聚焦超声治疗在预设目标点处的组织损伤情况,使用三维有限差分算法求解Westervelt方程,建立非线性声波传播数值模型,采用97阵元相控阵结合虚拟源的时间反转方法进行超声聚焦,分析其形成的声场和热场,并考察目标点偏离轴线时的组织损伤形成规律。结果表明随着目标点偏轴距离的增大,声压旁瓣开始增多。旁瓣的温升较低,不足以形成组织损伤。时间反转方法可用于多点聚焦,在一定的范围内,形成多点目标损伤而不产生额外的周围组织损伤。同时多点聚焦可以形成一个较大的损伤区域,减少超声治疗时间。 相似文献
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In this paper, we reported a numerical solution of laser induced thermal effect in the bio-tissue. The model of photothermal effect and classical Pennes bio-heat transfer equation were introduced. Finite element method (FEM), which was realized by Matlab software, was used to calculate the temperature distribution. He-Ne laser (633 nm) was used to simulate the physical therapy in in vivo skin tissue. Under the cylinder coordinates, the three-dimension(3-D) geometry of tissue was reduced to two-dimension(2-D)computation. The results contained the radial, axial and temperature 3-D color plot. Combining the time animation display was possible. By changing the laser and tissue parameters we can get different results.This will be the initial and indispensable work of the non-destructive evaluation of the laser induced injury. 相似文献
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Estimation of temperature elevation generated by ultrasonic irradiation in biological tissues using the thermal wave method 下载免费PDF全文
In most previous models,simulation of the temperature generation in tissue is based on the Pennes bio-heat transfer equation,which implies an instantaneous thermal energy deposition in the medium.Due to the long thermal relaxation time τ(20 s-30 s) in biological tissues,the actual temperature elevation during clinical treatments could be different from the value predicted by the Pennes bioheat equation.The thermal wave model of bio-heat transfer(TWMBT) defines a thermal relaxation time to describe the tissue heating from ultrasound exposure.In this paper,COMSOL Multiphysics 3.5a,a finite element method software package,is used to simulate the temperature response in tissues based on Pennes and TWMBT equations.We further discuss different factors in the bio-heat transfer model on the influence of the temperature rising and it is found that the temperature response in tissue under ultrasound exposure is a rising process with a declining rate.The thermal relaxation time inhibits the temperature elevation at the beginning of ultrasonic heating.Besides,thermal relaxation in TWMBT leads to lower temperature estimation than that based on Pennes equation during the same period of time.The blood flow carrying heat dominates most to the decline of temperature rising rate and the influence increases with temperature rising.On the contrary,heat diffusion,which can be described by thermal conductivity,has little effect on the temperature rising. 相似文献
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层/湍流等离子体射流的稳定性与三维特性的实验观测研究 总被引:1,自引:0,他引:1
采用普通照相和短时间曝光成像的ICCD照相技术,观测了低于大气压条件下产生的纯氩和氩-氢直流电弧等离子体射流的高温区的瞬时形貌及其变化,结合电弧弧根在阳极表面贴附行为的观测结果,对射流的稳定性与三维特性和弧根行为之间的关联进行了分析.结果表明,层流等离子体射流的高温区长度明显长于湍流射流情形,并且具有很好的轴对称性和时间稳定性;湍流射流的高温区瞬时形貌则表现出明显的三维特征;等离子体射流的三维特性与弧根在阳极表面的贴附行为没有直接的联系. 相似文献