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建筑LES模拟脉动入口的适用性研究 被引量:2
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作者 朱伟亮 杨庆山 曹曙阳 《空气动力学学报》 EI CSCD 北大核心 2011年第1期124-128,共5页
采用周期入流边界,在展向等间距网格系统中对平板湍流边界层(驱动单元)进行LES模拟,并将顺压力梯度引入流体控制方程以维持湍流边界层厚度的稳定。记录驱动单元脉动时程并将其引入虚拟模拟网格系统(验证单元)以研究LES脉动入口方法的适... 采用周期入流边界,在展向等间距网格系统中对平板湍流边界层(驱动单元)进行LES模拟,并将顺压力梯度引入流体控制方程以维持湍流边界层厚度的稳定。记录驱动单元脉动时程并将其引入虚拟模拟网格系统(验证单元)以研究LES脉动入口方法的适用性。数值结果表明,采用周期入流边界可成功实现脉动输入,边界层在顺压力梯度下的自保持性良好;脉动入流特性在驱动单元内保持良好,可满足工程需求;顺流向平均流速剖面以及湍流强度剖面均满足低湍流度下的风场特性,数值结果可为我国B类地貌下抗风研究采用。 展开更多
关键词 结构工程 结构抗风 大涡模拟 脉动入口 压力梯度
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Portal venous arterialization resulting in increased portal inflow and portal vein wall thickness in rats 被引量:7
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作者 Wen-Gang Li Yong-Liang Chen +4 位作者 Jing-Xi Chen Lei Qu Bin-Dang Xue Zhi-Hai Peng Zhi-Qiang Huang 《World Journal of Gastroenterology》 SCIE CAS CSCD 2008年第43期6681-6688,共8页
AIM: To explore the influence of portal vein hemodynamic changes after portal venous arterialization (PVA) on peribiliary vascular plexus (PVP) morphological structure and hepatic pathology, and to establish a th... AIM: To explore the influence of portal vein hemodynamic changes after portal venous arterialization (PVA) on peribiliary vascular plexus (PVP) morphological structure and hepatic pathology, and to establish a theoretical basis for the clinical application of PVA. METHODS: Sprague-Dawley rats were randomly divided into control and PVA groups. After PVA, hemodynamic changes of the portal vein and morphological structure of hepatohilar PVP were observed using Doppler ultrasound, liver function tests, ink perfusion transparency management and three-dimensional reconstruction of computer microvisualization, and pathological examination was performed on tissue from the bile duct wall and the liver. RESULTS: After PVA, the cross-sectional area and blood flow of the portal vein were increased, and the increase became more significant over time, in a certain range. If the measure to limit the flow in PVA was not adopted, the high blood flow would lead to dilatation of intrahepatic portal vein and its branches, increase in collagen and fiber degeneration in tunica intima. Except glutamic pyruvic transaminase (GPT), other liver function tests were normal. CONCLUSION: Blood with a certain flow and oxygen content is important for filling the PVP and meeting the oxygen requirement of the bile duct wall. After PVA, It is the anatomic basis to maintain normal morphology of hepatohilar bile duct wall that the blood with high oxygen content and high flow in arterialized portal vein may fill PVP by collateral vessel reflux. A adequate measure to limit blood flow is necessary in PVA. 展开更多
关键词 Peribiliary vascular plexus Portal venous arterialization Liver transplantation Bile duct neoplasms Three-dimensional reconstruction HEMODYNAMICS
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Gallbladder polyp as a manifestation of hemobilia caused by arterial-portal fistula after percutaneous liver biopsy: A case report 被引量:1
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作者 Chih-Lang Lin Tsung-Shih Lee +1 位作者 Kar-Wai Lui Cho-Li Yen 《World Journal of Gastroenterology》 SCIE CAS CSCD 2005年第2期305-307,共3页
Outpatient percutaneous liver biopsy is a common practice in the differential diagnosis and treatment of chronic liver disease. The major complication and mortality rate were about 2-4% and 0.01-0.33% respectively. Ar... Outpatient percutaneous liver biopsy is a common practice in the differential diagnosis and treatment of chronic liver disease. The major complication and mortality rate were about 2-4% and 0.01-0.33% respectively. Arterio-portal fistula as a complication of percutaneous liver biopsy was infrequently seen and normally asymptomatic. Hemobilia, which accounted for about 3% of overall major percutaneous liver biopsy complications, resulted rarely from arterio-portal fistula We report a hemobilia case of 68 years old woman who was admitted for abdominal pain after liver biopsy. The initial ultrasonography revealed a gallbladder polypoid tumor and common bile duct (CBD) dilatation. Blood clot was extracted as endoscopic retrograde cholangiopancreatography (ERCP) showed hemobilia. The patient was shortly readmitted because of recurrence of symptoms. A celiac angiography showed an intrahepatic arterio-portal fistula. After superselective embolization of the feeding artery, the patient was discharged uneventfully. Most cases of hemobilia caused by percutaneous liver biopsy resolved spontaneously. Selective angiography embolization or surgical intervention is reserved for patients who failed to respond to conservative treatment. 展开更多
关键词 Gallbladder polyp HEMOBILIA Arterial-portal fistula Percutaneous liver biopsy
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Hemodynamics in the portal vein evaluated by pulse wave Doppler ultrasonography in patients with chronic hepatitis C treated with interferon 被引量:1
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作者 Shigeo Nakanishi Katsuya Shiraki +3 位作者 Kouji Yamamoto Mutsumi Koyama Noboru Kimura Takeshi Nakano 《World Journal of Gastroenterology》 SCIE CAS CSCD 2005年第3期396-399,共4页
AIM: To employ pulse wave Doppler ultrasonography to evaluate the changes in portal blood flow velocity in patients with chronic hepatitis C (CHC) receiving interferon (IFN) treatment. METHODS: The subjects in this st... AIM: To employ pulse wave Doppler ultrasonography to evaluate the changes in portal blood flow velocity in patients with chronic hepatitis C (CHC) receiving interferon (IFN) treatment. METHODS: The subjects in this study were 14 patients (13 men and l woman) with CHC who received IFN treatment. Portal blood flow velocity was measured in the vessels at the porta hepatis at four time points: before IFN administration (pre-IFN), 2 wk after the start of administration (wk 2), 24 wk after the start of administration (wk 24, i.e., the end of IFN administration), and 24 wk after the end of administration (wk 48). RESULTS: The patients with CHC in whom IFN treatment resulted in complete elimination or effective elimination of viruses showed a significant increase in portal blood flow velocity at the end of IFN treatment compared with that before IFN treatment. In contrast, when IFN was ineffective, no significant increase in portal blood flow velocity was observed at wk 24 or 48 compared with the pre-IFN value. In addition, the patients with CHC in whom IFN was ineffective showed significantly lower portal blood flow velocity values than control subjects at all measurement time points. CONCLUSION: Pulse wave Doppler ultrasonography is a noninvasive and easily performed method for evaluating the effects of IFN treatment in patients with CHC. This technique is useful for measuring portal blood flow velocity before and 24 wk after IFN administration in order to evaluate the changes over time, thus assessing the effectiveness of IFN treatment. 展开更多
关键词 Chronic Hepatitis C INTERFERON Pulsed-wave Doppler ultrasonography Portal Vein HEMODYNAMICS
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用于可压缩壁面湍流LES及DNS入口边界条件的“回收-调节”方法综述
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作者 刘卫东 陈逖 +2 位作者 孙明波 范晓樯 梁剑寒 《航空动力学报》 EI CAS CSCD 北大核心 2011年第3期505-511,共7页
为了减小湍流流动问题的大涡模拟和直接数值模拟的入口湍流脉动边界条件对计算结果的影响,叙述了用于可压缩壁面湍流入口脉动生成的一种方法———"回收-调节"方法(recycling-rescaling method),叙述了这种方法的理论基础及... 为了减小湍流流动问题的大涡模拟和直接数值模拟的入口湍流脉动边界条件对计算结果的影响,叙述了用于可压缩壁面湍流入口脉动生成的一种方法———"回收-调节"方法(recycling-rescaling method),叙述了这种方法的理论基础及简要推导过程,介绍了几种常用的"回收-调节"方法并指出了实现中的几个关键问题,分析了这种方法中存在的不足并对其应用进行了总结评述.该方法可为湍流、燃烧问题的大涡模拟和直接数值模拟方法的发展提供参考. 展开更多
关键词 大涡模拟 直接数值模拟 可压缩壁面湍流 入口脉动生成 “回收-调节”方法
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湍流边界层中低矮建筑绕流大涡模拟 被引量:6
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作者 朱伟亮 杨庆山 《建筑结构学报》 EI CAS CSCD 北大核心 2010年第10期41-47,共7页
通过对平板湍流边界层进行大涡模拟,采用拟周期边界条件维持湍流边界层厚度稳定,提取速度和压力时程作为低矮建筑绕流模拟之脉动入流边界条件,研究脉动入流下的低矮建筑绕流特性。研究结果表明:入流边界特性对网格变化适应性良好,其平... 通过对平板湍流边界层进行大涡模拟,采用拟周期边界条件维持湍流边界层厚度稳定,提取速度和压力时程作为低矮建筑绕流模拟之脉动入流边界条件,研究脉动入流下的低矮建筑绕流特性。研究结果表明:入流边界特性对网格变化适应性良好,其平均速度剖面、湍流强度、流速频谱特性基本符合空旷地貌风场特性;脉动入流下,建筑表面的平均风压系数、脉动风压系数的计算结果与风洞试验结果基本吻合。受雷诺数及湍流强度的影响,流动分离区负压与试验值存在一定差别;屋盖上分离区风压时程具有非高斯概率特性,尤以气流分离较剧烈的屋盖迎风边缘及屋盖两侧风压的非高斯特性明显,该特征与风洞试验基本一致;受非高斯特性的影响,建议峰值因子g取4.5~5.5。 展开更多
关键词 低矮建筑 结构抗风 大涡模拟 脉动入口 风压系数
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“回收/调节”方法在混合LES/RANS模拟方法中的应用 被引量:5
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作者 陈逖 刘卫东 +1 位作者 范晓樯 孙明波 《航空动力学报》 EI CAS CSCD 北大核心 2011年第6期1215-1222,共8页
采用一种混合大涡模拟/雷诺平均Navier-Stokes(LES/RANS)模拟方法结合三阶加权基本无振荡(WENO)格式对马赫数为2.88的压缩斜坡流动进行了数值模拟,并采用"回收/调节"方法生成入口湍流脉动边界条件.当采用固定入口边界条件时,... 采用一种混合大涡模拟/雷诺平均Navier-Stokes(LES/RANS)模拟方法结合三阶加权基本无振荡(WENO)格式对马赫数为2.88的压缩斜坡流动进行了数值模拟,并采用"回收/调节"方法生成入口湍流脉动边界条件.当采用固定入口边界条件时,湍流边界层会缺乏合理的湍流能量,使之抵抗逆压梯度的能力减弱,会严重高估分离区的大小;而当采用"回收/调节"方法时,可以在10倍来流边界层厚度的距离内激励起湍流大尺度结构,计算得到的流场能够再现激波/湍流边界层干扰流场的非定常特性,时间及展向平均壁面压力和试验值吻合较好. 展开更多
关键词 混合大涡模拟/雷诺平均Navie-Stokes(LES/RANS) 加权基本无振荡(WENO)格式 “回收/调节”方法 入口湍流脉动边界条件 激波/湍流边界层干扰
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