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Variational study of bifurcations in von Karman equations
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作者 Rongrong JIN Guangcun LU 《中国数学前沿:英文版》 SCIE CSCD 2019年第3期567-590,共24页
For a class of nonlinear elliptic boundary value problems including the von Karman equations considered by D. M. Due, N. L. Luc, L. Q. Nam, and T. T. Tuyen [Nonlinear Anal., 2003, 55: 951-968], we give a new proof of ... For a class of nonlinear elliptic boundary value problems including the von Karman equations considered by D. M. Due, N. L. Luc, L. Q. Nam, and T. T. Tuyen [Nonlinear Anal., 2003, 55: 951-968], we give a new proof of a corresponding theorem of three solutions via Morse theory instead of topological degree theory. Several bifurcation results for this class of boundary value problems are also obtained with Morse theory methods. In addition, for the von Karman equations studied by A. Borisovich and J. Janczewska [Abstr. Appl. Anal., 2005, 8: 889-899], we prove a few of bifurcation results under Dirichlet boundary conditions based on the second named author’s recent work about parameterized splitting theorems and bifurcations for potential operators. 展开更多
关键词 MORSE THEORY von Karman EQUATIONS BIFURCATION
Extrapolation reconstruction of wind pressure fields on the claddings of high-rise buildings
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作者 Yehua SUN Guquan SONG Hui LV 《结构与土木工程前沿:英文版》 EI CSCD 2019年第3期653-666,共14页
Recent research about reconstruction methods mainly used the interpolation reconstruction of the fluctuating wind pressure field on the surface.However,to investigate wind pressure at the edge of the building,the work... Recent research about reconstruction methods mainly used the interpolation reconstruction of the fluctuating wind pressure field on the surface.However,to investigate wind pressure at the edge of the building,the work presented in this paper focuses on the extrapolation reconstruction of wind pressure fields.Here,we propose an improved proper orthogonal decomposition(POD)and Kriging method with a von Karman correlation function to resolve this issue.The studies show that it works well for not only interpolation reconstruction but also extrapolation reconstruction.The proposed method does require determination of the Hurst exponent and other parameters analysed from the original data.Hence,the fluctuating wind fields have been characterized by the von Karman correlation function,as an a priori function.Compared with the cubic spline method and different variogram,preliminary results suggest less time consumption and high efficiency in extrapolation reconstruction at the edge. 展开更多
关键词 EXTRAPOLATION RECONSTRUCTION PROPER orthogonal decomposition KRIGING method von Karman function Hurst EXPONENT rescaled range analysis
8800DF(R)涡街流量计在铜冶炼中的应用
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作者 李庚民 段兴文 朱国斌 《金川科技》 2018年第2期39-40,共2页
本文简述8800DF(R)涡街流量计在铜冶炼生产中的使用特点.介绍了8800DF(R)涡街流量计工作原理、优缺点、分类.使用注意事项、选型等。
关键词 8800 df(R)vortex FLOWMETER Karman VORTEX STREET REYNOLDS number VORTEX occurred body.
Kaimal和Von Karman湍流谱模型在风电机组载荷计算中的差异 预览 被引量:4
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作者 蔡继峰 张宇 《风能》 2012年第3期共5页
本文在Bladed for Windows 4.2环境下,基于Kaimal湍流模型和Von Karman湍流模型对风电机组载荷进行了大量仿真计算,根据IEC61400-1 Ed.3的要求,从疲劳载荷和极限载荷外推两个角度对结果进行了统计对比,并对差异给出了评价,供风电机组... 本文在Bladed for Windows 4.2环境下,基于Kaimal湍流模型和Von Karman湍流模型对风电机组载荷进行了大量仿真计算,根据IEC61400-1 Ed.3的要求,从疲劳载荷和极限载荷外推两个角度对结果进行了统计对比,并对差异给出了评价,供风电机组设计和认证过程中参考. 展开更多
关键词 Kaimal Von Karman 湍流谱模型 等效疲劳载荷 极限载荷外推
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Effects of Turbulent Dispersion of Atmospheric Balance Motions of Planetary Boundary Layer 预览 被引量:1
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作者 刘式适 黄伟 荣平平 《大气科学进展:英文版》 SCIE CAS CSCD 1992年第2期147-156,共10页
New Reynolds’ mean momentum equations including both turbulent viscosity and dispersion are used to analyze atmospheric balance motions of the planetary boundary layer. It is pointed out that turbulent dispersion w... New Reynolds’ mean momentum equations including both turbulent viscosity and dispersion are used to analyze atmospheric balance motions of the planetary boundary layer. It is pointed out that turbulent dispersion with r 0 will increase depth of Ekman layer, reduce wind velocity in Ekman layer and produce a more satisfactory Ekman spiral lines fit the observed wind hodograph. The wind profile in the surface layer including tur-bulent dispersion is still logarithmic but the von Karman constant k is replaced by k1 = 1 -2/k, the wind increasesa little more rapidly with height. 展开更多
关键词 TURBULENT REYNOLDS EKMAN Dispersion MOMENTUM satisfactory Karman averaged PLANETARY logarithmic
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A numerical study of sound field radiated by the flow around a circular cylinder
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《声学学报:英文版》 1992年第1期17-30,共14页
The Von-Karman vortex street flow behind a circular cylinder issuccessfully solved at R_e=100 for incompressible N-S equations in theform of stream function and vorticity.The method adopted here involvesADI-BGE schem... The Von-Karman vortex street flow behind a circular cylinder issuccessfully solved at R_e=100 for incompressible N-S equations in theform of stream function and vorticity.The method adopted here involvesADI-BGE schemes,a recent treatment of body boundary conditions anda new acceptable perturbation model.The solutions of the flow fieldobtained here are better than previous numerical ones and agree with theexperimental data closer.Therefore,it can be used to study sound fieldnumerically.The Curle equation is directly and numerically solved to ana-lyze the distribution of sound sources and the characteristics of their radi-ated sound field at R_e=100 and to compare with the solution fromthe theory of vortex sound.It is shown that this method is successful. 展开更多
关键词 cylinder circular VORTEX INCOMPRESSIBLE PERTURBATION VORTICITY AGREE Karman UNSTEADY numerically
ON THE INSTABILITY OF WAKES BEHIND STATIONARY CIRCULAR CYLINDERS 预览
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《中国航空学报:英文版》 SCIE EI CAS CSCD 1991年第2期171-178,共8页
The study on the formation of vortex streets behind stationary circular cylinders is of substantial sense in engineering, since vortex streets play the leading role in introduction of vibration, generation of noise ... The study on the formation of vortex streets behind stationary circular cylinders is of substantial sense in engineering, since vortex streets play the leading role in introduction of vibration, generation of noise and wake instability, etc.. In the present paper, the Orr-Sommerfeld equation combined with measured velocity profiles is used to investigate the type of instability behind stationary cylinders, which determines the mechanism of vortex formation. The numerical calculations for Reynolds numbers of 56-140 000 imply that there is a range around the end of the dead water region in cylinder wakes where the instability belongs to the absolute type. Beyond the range, the flows show to be of the convective type. On the other hand, the flows tend to be of the convective instability when Reynolds number is below the subcritical value of forming vortex streets. All of the correspondent Strouhal numbers agree with experimental data very well. The formation of vortex streets behind stationary cylinders is 展开更多
关键词 vortex INSTABILITY CONVECTIVE absolute STATIONARY REYNOLDS behind cylinders AGREE Karman
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TWO DIMENSIONAL DISTRIBUTION OF SEDIMENT CONCENTRATION NEAR THE BOTTOM OF STANDING WAVES IN SHALLOW WATER 预览
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作者 Zhang, Furan Wang, Huaren 《中国海洋工程:英文版》 SCIE EI 1990年第3期307-314,共8页
In this paper, the formula of turbulent viscous coeffecient of standing waves in shallow water is obtained with Karman theory. Then, the two dimensional solution of sediment concentration near the bottom of standing... In this paper, the formula of turbulent viscous coeffecient of standing waves in shallow water is obtained with Karman theory. Then, the two dimensional solution of sediment concentration near the bottom of standing waves in shallow water is deduced, which is in good agreement with Hattori’s semi-empirical result (1969, 1971). 展开更多
关键词 TURBULENT VISCOUS SHALLOW Karman deduced empirical suspended COORDINATES NEGLECTED SEDIMENTARY
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DIMPLE IMPERFECTION SENSITIVITY OF SUBMARINE PIPELINES UNDER COMBINED EXTERNAL PRESSURE AND AXIAL LOAD 预览
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作者 Huang, Yuying Yue, Dongyi 《中国海洋工程:英文版》 SCIE EI 1989年第4期499-507,共9页
Based on the Karman-Donnell shell equations, a two-timing perturbation technique together with Fourier series expansion is used to solve an imperfection sensitivity problem of submarine pipelines with dimple shaped ... Based on the Karman-Donnell shell equations, a two-timing perturbation technique together with Fourier series expansion is used to solve an imperfection sensitivity problem of submarine pipelines with dimple shaped initial deflection under external pressure combined with axial load. The relationship between limit load and initial postbuckling coefficient as well as imperfection parameter is obtained. It shows that these submarine pipelines are imperfection-sensitive to a dimple shaped imperfection over a large range of a geometrical parameter and that the effect of the dimple shaped imperfection on limit load depends only upon its linear buckling mode component of the corresponding Fourier series expansion. 展开更多
关键词 pipelines SUBMARINE shaped PERTURBATION BUCKLING Karman Pipeline OFFSHORE expanded DEFLECTION
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POSTBUCKLING OF RECTANGULAR PLATES UNDER UNIAXIAL COMPRESSION COMBINED WITH LATERAL PRESSURE 预览
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作者 沈惠申 《应用数学和力学:英文版》 SCIE EI 1989年第1期55-63,共9页
Based on the nonlinear large deflection equations of von Karman plates,thee ateralpressure is first converted into an initial deflection by Galerkin method,the postbucklingbehavior of simply supported rectangular pl... Based on the nonlinear large deflection equations of von Karman plates,thee ateralpressure is first converted into an initial deflection by Galerkin method,the postbucklingbehavior of simply supported rectangular plates under uniaxial compression combined withlateral pressure is then studied applying perturbation method by taking deflection asperturbation parameter.Two types of in-plane boundary conditions and the effects of initial geometricimperfection are also considered.It is found that the theoretical results are in goodaccordance with experiments. 展开更多
关键词 DEFLECTION simply Karman APPLYING PERTURBATION converted imperfect UNIAXIAL rectangular BUCKLING
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A CORRECTION TO REMOTE SENSING BY SODAR
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作者 周秀骥 《科学通报:英文版》 SCIE EI 1988年第5期411-413,
<正> Acoustic sounders, or sodars, are important instruments for the study of the atmospheric boundary layer. They can be used to measure a variety of physical parameters in lower atmosphere, such as profiles of... <正> Acoustic sounders, or sodars, are important instruments for the study of the atmospheric boundary layer. They can be used to measure a variety of physical parameters in lower atmosphere, such as profiles of wind, temperature and turbulent microstructure. So far, for analysing acoustic echoes, the sodar equation relating to the received power P(R) to other parameters has been written as 展开更多
关键词 TURBULENT instruments TURBULENCE ATTENUATION tempera negligible FLUCTUATION Karman lidar Profiles
随从力作用下薄膜的非线性自由振动特性研究 预览
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作者 邵明月 武吉梅 +2 位作者 应戍狄 王砚 卢瑶 《西安理工大学学报》 CAS 北大核心 2019年第1期17-22,共6页
本文研究了切向均布随从力作用下运动印刷薄膜的非线性振动特性。基于Von Karman薄板理论推导出轴向运动薄膜非线性振动方程,应用Galerkin方法对振动偏微分方程组进行离散,利用数值法对微分方程进行求解,得到薄膜非线性振动的频率表达... 本文研究了切向均布随从力作用下运动印刷薄膜的非线性振动特性。基于Von Karman薄板理论推导出轴向运动薄膜非线性振动方程,应用Galerkin方法对振动偏微分方程组进行离散,利用数值法对微分方程进行求解,得到薄膜非线性振动的频率表达式。分析了不同初始条件下,随从力和无量纲运动速度对薄膜振动复频率的影响。该研究可为印刷机的设计、制造以及印刷机的稳定性提供理论指导。 展开更多
关键词 非线性振动 随从力 运动薄膜 Von Karman薄板理论
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基于高阶剪切变形理论的磁电弹性梁的非线性静力分析 预览
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作者 许亮亮 郑玉芳 陈昌萍 《贵州大学学报:自然科学版》 2019年第6期17-21,共5页
基于高阶剪切变形理论和Von Karman非线性理论建立磁电弹性梁的非线性模型,采用Hamilton原理推导磁电弹性梁的非线性平衡微分方程,利用伽辽金方法对该非线性偏微分方程组进行求解。数值计算中,具体讨论了外部荷载、跨高比、磁场及电场... 基于高阶剪切变形理论和Von Karman非线性理论建立磁电弹性梁的非线性模型,采用Hamilton原理推导磁电弹性梁的非线性平衡微分方程,利用伽辽金方法对该非线性偏微分方程组进行求解。数值计算中,具体讨论了外部荷载、跨高比、磁场及电场等因素对磁电弹性梁非线性静力响应的影响。 展开更多
关键词 Reddy三阶剪切理论 Von Karman非线性理论 磁电弹性梁 伽辽金法
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基于卡门涡街的水下振动能量采集器的设计与研究(英文) 预览
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作者 王海 金标 +3 位作者 姚刚 杨春来 郑衍畅 文莉 《传感技术学报》 CAS CSCD 北大核心 2019年第3期469-475,共7页
针对传统的单自由度压电能量采集器工作带宽窄的现状,提出了在水下流激振动环境下的一种基于卡门涡街的二自由度宽频压电能量采集器来提高压电能量采集器的带宽。3种二自由度压电能量采集器分别被设计、制造,并且测试了能量采集性能。... 针对传统的单自由度压电能量采集器工作带宽窄的现状,提出了在水下流激振动环境下的一种基于卡门涡街的二自由度宽频压电能量采集器来提高压电能量采集器的带宽。3种二自由度压电能量采集器分别被设计、制造,并且测试了能量采集性能。结果表明,采用二自由度能量采集器比采用传统的单自由度能量采集器具有更好的采集效率。根据仿真和实验结果,H型压电能量采集器具有更好的振动能量采集效率。 展开更多
关键词 无线传感网络 压电能量采集器 卡门涡街 二自由度
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测温元件保护套管对管道流体流态特征影响的模拟分析 预览
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作者 苏苗印 《管道技术与设备》 CAS 2019年第6期39-42,共4页
文中对测温元件保护套管进行三维建模,采用Fluent软件对管道内流体进行模拟仿真和分析计算,并研究不同插入深度下管内流体的流态特征,为工程设计或安装施工提供参考。
关键词 温度元件保护套管 插入深度 套管外径 数值模拟 圆柱绕流 卡曼涡街
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嫦娥四号着陆点区域高分辨率数字高程模型构建 预览
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作者 陈昊 刘世杰 +1 位作者 童小华 胡明 《上海航天》 CSCD 2019年第3期35-39,共5页
嫦娥四号登月探测器成功着陆于冯·卡门撞击坑内,实现了人类历史上首次月背软着陆。嫦娥四号登月探测器着陆区的高分辨率数字高程模型(DEM)对后续任务顺利开展至关重要,着陆点区域的三维地形可为月球探测提供关键空间信息支撑,但在... 嫦娥四号登月探测器成功着陆于冯·卡门撞击坑内,实现了人类历史上首次月背软着陆。嫦娥四号登月探测器着陆区的高分辨率数字高程模型(DEM)对后续任务顺利开展至关重要,着陆点区域的三维地形可为月球探测提供关键空间信息支撑,但在嫦娥四号着陆点区域,月球轨道激光高度计生成的DEM/LOLADEM分辨率仅有30m,未见公布高分辨率DEM。基于高分辨率的月球勘测轨道飞行器窄角相机(LROCNAC)影像,利用摄影测量法和阴影恢复形状方法(SFS)针对嫦娥四号着陆点区域,生成了着陆点区域的高分辨率DEM。结果表明,SFS法生成的DEM分辨率更高,重建的地形更加精细。 展开更多
关键词 嫦娥四号登月探测器 冯·卡门撞击坑 数字高程模型 月球勘测轨道飞行器窄角相机(LROCNAC) 阴影恢复形状
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基于卡门涡街效应的压电悬臂梁的发电仿真分析 预览
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作者 李海宁 王海峰 +2 位作者 郭修宇 孙凯利 崔宜梁 《青岛大学学报:工程技术版》 CAS 2019年第3期11-15,共5页
为研究压电体在海洋中受迫振动发生形变产生电场的复杂问题,本文以柔性压电片(聚偏氟乙烯作为压电体)为例,基于ANSYS有限元仿真软件,建立流体固体压电三场耦合的仿真模型,研究基于卡门涡街效应的柔性压电悬臂梁的发电能力与水速、圆柱... 为研究压电体在海洋中受迫振动发生形变产生电场的复杂问题,本文以柔性压电片(聚偏氟乙烯作为压电体)为例,基于ANSYS有限元仿真软件,建立流体固体压电三场耦合的仿真模型,研究基于卡门涡街效应的柔性压电悬臂梁的发电能力与水速、圆柱直径、压电片尺寸之间的关系。分析结果表明,在压电片尺寸和水流速度相同的情况下,圆柱直径为40 mm时,产生的电压最大为1.95 V;在压电片尺寸和圆柱直径相同的情况下,水流速度为0.2 m/s时,产生的电压最大为1.95 V;在水流速度和圆柱直径相同的情况下,当压电片长度为170 mm时,产生的电压最大为1.85 V。该研究为以后相关研究提供了理论基础。 展开更多
关键词 卡门涡街 压电悬臂梁 柔性压电发电装置 ANSYS 多物理场耦合 数值水槽
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涡街提频振荡水柱驱动压电发电理论分析 预览
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作者 杜小振 李周杰 +2 位作者 康辉 张咪 于红 《压电与声光》 CAS 北大核心 2019年第4期557-561,569共6页
海洋波浪能频率低(0.3~1Hz),海浪进入振荡水柱气室压缩空气形成高速气流。在高速气流通道内放置绕流圆柱钝体,采用卡门涡街效应提高波浪能振荡水柱采集气室气压激振频率,实现高频驱动压电发电,提高海洋能量转换效率。推导波浪进入气室... 海洋波浪能频率低(0.3~1Hz),海浪进入振荡水柱气室压缩空气形成高速气流。在高速气流通道内放置绕流圆柱钝体,采用卡门涡街效应提高波浪能振荡水柱采集气室气压激振频率,实现高频驱动压电发电,提高海洋能量转换效率。推导波浪进入气室形成振荡的水气动力转换理论,计算了气室初级压强和流速。分析了低频高压气流经钝体形成卡门涡街高频涡流激振提频过程,计算出气压作用于钹型压电发电结构输出的电量。研究气体流速、钝体等系统参数与输出能量的关系。计算结果表明,周期为0.65~1.1s的海浪进入气室经提频作用于钹型压电发电结构,稳定输出电能可达70~80mW,为新型波浪能采集技术提供了理论基础。 展开更多
关键词 波浪能 振荡水柱 卡门涡街 气室流量 压电发电
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电脱水器绝缘棒圆柱绕流数值模拟研究 预览
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作者 于进 杜炘洁 《油气田地面工程》 2019年第8期29-35,39共8页
使用FLUENT软件数值模拟研究原油电脱水器绝缘棒的三维圆柱绕流问题,旨在寻找合适的原油流速,使得漩涡区域最小。采用标准k-ε模型对来流速度为0.5、1.0和2.0m/s三种情况进行了模拟计算,并详细分析了计算结果,包括压力云图和速度云图等... 使用FLUENT软件数值模拟研究原油电脱水器绝缘棒的三维圆柱绕流问题,旨在寻找合适的原油流速,使得漩涡区域最小。采用标准k-ε模型对来流速度为0.5、1.0和2.0m/s三种情况进行了模拟计算,并详细分析了计算结果,包括压力云图和速度云图等。对不同流速下三维圆柱体绕流的各个截面漩涡脱落形式和速度、压力的变化情况进行分析,从而研究圆柱体绕流问题的三维效应,研究发现,通过改变区域的速度就可达到改变甚至消除卡门涡街的目的,同时也证明了FLUENT软件对不可压缩绕流计算的可行性和准确性。 展开更多
关键词 电脱水器 绝缘棒 三维圆柱绕流 FLUENT软件 数值模拟 漩涡 卡门涡街
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湍流模型系数不确定度对翼型绕流模拟的影响
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作者 赵辉 胡星志 +2 位作者 张健 陈江涛 马明生 《航空学报》 EI CAS CSCD 北大核心 2019年第6期68-78,共11页
使用非嵌入式多项式混沌方法研究了湍流模型系数的不确定度对RAE2822跨声速翼型绕流模拟的影响。计算中关注了数值模拟的积分量(升力系数、阻力系数)和局部量(壁面压力、摩擦系数和空间马赫数分布)的不确定度量化结果。首先,从单输入变... 使用非嵌入式多项式混沌方法研究了湍流模型系数的不确定度对RAE2822跨声速翼型绕流模拟的影响。计算中关注了数值模拟的积分量(升力系数、阻力系数)和局部量(壁面压力、摩擦系数和空间马赫数分布)的不确定度量化结果。首先,从单输入变量入手,研究卡门常数的不确定度对数值模拟的影响。然后,同时考虑Spalart-Allmaras模型中9个参数的不确定度带来的影响。通过多项式混沌展开,得到系统输出对不确定输入变量的响应,由此可以得到输出的统计特性,包括平均值、方差和极值等信息。最后,在多变量不确定度量化过程中,通过Sobol指标来量化每个输入变量的不确定度对输出不确定度的贡献程度。本文计算只考虑了RAE2822跨声速翼型模拟的单一计算状态,影响规律是否可以推及其他工况和算例需要进一步检验。 展开更多
关键词 不确定度量化 多项式混沌 湍流模型 卡门常数 翼型绕流
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