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Effect of Mach number on transonic flow past a circular cylinder

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Chinese Science Bulletin 2009年第11期54卷 1886-1893页

作者： xu changyue CHEN LiWei LU XiYun Department of Modern Mechanics University of Science and Technology of China Hefei 230026 China

The effect of Mach number on transonic flow past a circular cylinder is investigated numerically for the free-stream Mach number M∞ from 0.85 to 0.98 and the Reynolds number 2×105 based on the diameter of the cylinder. The work provides an insight into several salient features, including unsteady and quasi-steady flow state, formation of local supersonic zone, and evolution of turbulent shear layer. Results show that there exist two flow states dependent of a critical Mach number Mcr around 0.9. One is an unsteady flow state characterized by moving shock waves interacting with the turbulent flow in the near region of the cylinder for M∞Mcr, suppressing vortex shedding from the cylin-der. Some flow behaviors in the unsteady and quasi-steady flow states are revealed. From time evolu-tion of flow structures, local supersonic zones are identified in the wake and generated by two typical processes, i.e. reverse flow behind the cylinder and shed vortices in the near wake. The convective Mach number Mc of turbulent shear layers shed from the cylinder is identified nearly as Mc1 in the quasi-steady flow regime, resulting in different evolutions of the shear layers.

关键词：马赫数圆柱体绕流非定常流动湍流流动时间演化稳态流动剪切层

Shock-Wave/Rail-Fasteners Interaction for Two Rocket Sleds in the Supersonic Flow Regime

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Fluid Dynamics & Materials Processing 2020年第4期16卷 675-684页

作者： Bin Wang Jing Zheng Yuanyuan Yu Runmin Lv changyue xu Key Laboratory of Aircraft Environment Control and Life Support MIITNanjing University of Aeronautics and AstronauticsNanjing210016China AVIC Aerospace Life-Support Industries Ltd.Xiangyang441003China

Rocket sleds belong to a category of large-scale test platforms running on the *** applications can be found in many fields,such as aerospace engineering,conventional weapons,and civil high-tech *** the present work,shock-wave/rail-fasteners interaction is investigated numerically when the rocket sled is in supersonic flow *** typical rocket sled models are considered,i.e.,an anti-D shaped version of the rocket sled and an axisymmetric slender-body *** dynamics for Mach number 2 have been simulated in the framework of a dynamic mesh *** emerging shock waves can be categorized as head-shock,tailing-shock and *** unsteady large-scale vortex and related shock dynamics have been found for the anti-D shaped rocket ***,a quasi-steady flow state exists for the slender-body shaped rocket *** indicates that the axisymmetric geometry is more suitable for the effective production of rocket *** the help of power spectral density analysis,we have also determined the characteristic frequencies related to shock-wave/rail-fasteners ***,a harmonic phenomenon has been revealed,which is intimately related to a shock wave reflection mechanism.

关键词： Rocket sled shock wave dynamic mesh method ground effect

Three-dimensional numerical simulation of a vortex ring impacting a bump

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Theoretical & Applied Mechanics Letters 2014年第3期4卷 42-48页

作者： Heng Ren changyue xu China Electronics Technology Group Corporation No.38 Research Institute College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics

A vortex ring impinging on a three-dimensional bump is studied using large eddy simulation for a Reynolds number Re = 4 × 104 based on the initial translation speed and diameter of the vortex ring. The effects of bump height on the vortical flow phenomena and the underlying physical mechanisms are inves- tigated. Based on the analysis of the evolution of vortical structures, two typical kinds of vortical structures, i.e., the wrapping vortices and the hair-pin vortices, are identified and play an important role in the flow state evolution. The circu- lation of the primary vortex ring reasonably elucidates some typical phases of flow evolution. Furthermore, the mechanism of flow transition from laminar to turbulent state has been revealed based on analysis of turbulent kinetic energy.

关键词： large eddy simulation vortex ring bump vortical structure turbulent state

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地面对双轨超声速火箭橇的气动特性影响研究

航空科学技术 2024年第4期35卷 31-39页

作者：王方元林晓辉余元元董凌锋郑达仁许常悦南京航空航天大学飞行器环境控制与生命保障工业与信息化部重点实验室江苏南京210016 航空工业航宇救生装备有限公司湖北襄阳441003 航空防护救生技术航空科技重点实验室湖北襄阳441003

地面对动态滑行状态下双轨火箭橇的气动特性有较大影响。本文采用尺度自适应(SAS)方法和动网格方法结合的策略对Ma 2的双轨火箭橇进行数值模拟,研究了地面导致的流场变化、气动力及其时域和频域特性。结果表明,激波和压缩波在地面设施... 详细信息

地面对动态滑行状态下双轨火箭橇的气动特性有较大影响。本文采用尺度自适应(SAS)方法和动网格方法结合的策略对Ma 2的双轨火箭橇进行数值模拟,研究了地面导致的流场变化、气动力及其时域和频域特性。结果表明,激波和压缩波在地面设施的反射会导致双轨火箭橇下表面出现6处额外的高压区,其中4处的形状和强度会随反射位置发生变化;地面导致升力时均值提升了9.6倍;气动力呈现明显的同频周期性振荡,升力振荡幅值为时均值的28.6%,阻力振荡较小。为双轨火箭橇的减阻减振工作提供参考依据。

关键词：双轨火箭橇超声速流动 SAS 动网格气动特性

Evolutionary history shapes variation of wood density of tree species across the world

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Plant Diversity 2024年第3期46卷 283-293页

作者： Fangbing Li Hong Qian Jordi Sardans Dzhamal Y.Amishev Zixuan Wang changyue Zhang Tonggui Wu Xiaoniu xu Xiao Tao Xingzhao Huang Anhui Province Key Laboratory of Forest Resources and Silviculture Anhui Agricultural UniversityHefei 230036China State Key Laboratory of Subtropical Silviculture Zhejiang A&F UniversityHangzhou 311300China Research and Collections Center Illinois State Museum1011 East Ash StreetSpringfieldIL 62703USA CREAF Cerdanyola del VallesBarcelona 08193Spain Global Ecology Unit CREAF-CSIC-UAB CSICBellaterraBarcelona 08193Spain Key Laboratory of Ecosystem Carbon Source and Sink China Meteorological Administration(ECSS-CMA)School of Applied MeteorologyNanjing University of Information Science&Technology219 Ningliu RoadNanjing 210044China Department of Natural Resources Management Lakehead UniversityThunder BayOntario P7B 5E1Canada School of Forestry&Landscape of Architecture Anhui Agricultural UniversityHefei 230036China Research Institute of Subtropical Forestry Chinese Academy of ForestryHangzhou 311400China

The effect of evolutionary history on wood density variation may play an important role in shaping variation in wood density,but this has largely not been *** a comprehensive global dataset including 27,297 measurements of wood density from 2621 tree species worldwide,we test the hypothesis that the legacy of evolutionary history plays an important role in driving the variation of wood density among tree *** assessed phylogenetic signal in different taxonomic(e.g.,angiosperms and gymnosperms)and ecological(e.g.,tropical,temperate,and boreal)groups of tree species,explored the biogeographical and phylogenetic patterns of wood density,and quantified the relative importance of current environmental factors(e.g.,climatic and soil variables)and evolutionary history(i.e.,phylogenetic relatedness among species and lineages)in driving global wood density *** found that wood density displayed a significant phylogenetic *** density differed among different biomes and climatic zones,with higher mean values of wood density in relatively drier regions(highest in subtropical desert).Our study revealed that at a global scale,for angiosperms and gymnosperms combined,phylogeny and species(representing the variance explained by taxonomy and not direct explained by long-term evolution process)explained 84.3%and 7.7%of total wood density variation,respectively,whereas current environment explained 2.7%of total wood density variation when phylogeny and species were taken into *** angiosperms and gymnosperms were considered separately,the three proportions of explained variation are,respectively,84.2%,7.5%and 6.7%for angiosperms,and 45.7%,21.3%and 18.6%for *** study shows that evolutionary history outpaced current environmental factors in shaping global variation in wood density.

关键词： Wood density Phylogeny Angiosperms Gymnosperms Climate factors Biophysical parameters

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平面超声速引射器内部流动的大涡模拟

航空学报 2014年第8期35卷 2136-2143页

作者：许常悦周涛王从磊南京航空航天大学航空宇航学院江苏南京210016

采用大涡模拟(LES)方法对平面超声速引射器的内部流动进行了数值研究。为了验证LES方法的可靠性,对计算结果和实验数据进行了定量对比,对比的物理量有速度和温度剖面。结果表明当前计算结果和实验数据吻合得较好,这说明LES方法能够有效... 详细信息

采用大涡模拟(LES)方法对平面超声速引射器的内部流动进行了数值研究。为了验证LES方法的可靠性,对计算结果和实验数据进行了定量对比,对比的物理量有速度和温度剖面。结果表明当前计算结果和实验数据吻合得较好,这说明LES方法能够有效地研究此类问题。引射器主射流的失稳过程与自由射流的失稳过程相同,分为增长、失稳和混合3个阶段。Lamb矢量散度的分布表明,混合室内部的混合过程被限制在狭小的带状区域。混合室内压力信号的功率谱分析表明,主射流的失稳主导着混合室内部流体的混合过程,其特征St数约为0.27。

关键词：可压缩流动引射器射流大涡模拟湍流

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方柱跨声速流动中的剪切层和尾迹特性

上海交通大学学报 2021年第4期55卷 403-411页

作者：许常悦郑静王哲王彬南京航空航天大学飞行器环境控制与生命保障工业和信息化部重点实验室南京210016

采用尺度自适应模拟(SAS)方法研究了来流马赫数Ma为0.71、雷诺数Re为4×10^(5)的方柱跨声速绕流,并对分离剪切层和尾迹特性进行了深入分析.为了验证SAS方法的可靠性,将SAS结果与已有数值和实验结果进行了对比.在当前的跨声速流场中,剪... 详细信息

采用尺度自适应模拟(SAS)方法研究了来流马赫数Ma为0.71、雷诺数Re为4×10^(5)的方柱跨声速绕流,并对分离剪切层和尾迹特性进行了深入分析.为了验证SAS方法的可靠性,将SAS结果与已有数值和实验结果进行了对比.在当前的跨声速流场中,剪切层中的对流马赫数约为0.6,这意味着Kelvin-Helmholtz不稳定性主导剪切层的初始阶段演化.在剪切层的初始阶段,可以看出扰动涡沿展向呈现滚筒状结构.剪切层外侧附近和方柱的回流区均出现倍频现象,这与剪切层中存在明显的涡合并有关.压力场的本征正交分解表明,方柱跨声速流场中的主导流动模态为反对称模态,这与尾迹中的涡脱落现象和剪切层引起的压缩波传播有关.

关键词：方柱激波剪切层 Lamb矢量尺度自适应模拟

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来流马赫数对座舱气动加热影响的数值模拟

南京航空航天大学学报 2011年第4期43卷 464-469页

作者：吴丹许常悦孙建红南京航空航天大学航空宇航学院南京210016

采用数值手段研究了来流马赫数对飞机座舱附近区域气动加热的影响,计算的来流马赫数为0.8~2.0,基于翼展的雷诺数为107。通过分析飞机蒙皮表面的温度分布、表面摩擦因数、壁面法向速度梯度和热流量等物理量,给出了飞机头部座舱附近区域... 详细信息

采用数值手段研究了来流马赫数对飞机座舱附近区域气动加热的影响,计算的来流马赫数为0.8~2.0,基于翼展的雷诺数为107。通过分析飞机蒙皮表面的温度分布、表面摩擦因数、壁面法向速度梯度和热流量等物理量,给出了飞机头部座舱附近区域的气动热分布情况。计算结果表明,随着来流马赫数的增加,壁面法向速度梯度增大,飞机对称面上的平均温度、表面摩擦因数和热流量随之增大。此外,针对某型号飞机的计算结果表明,座舱附近区域上表面中心线上的平均温度与来流马赫数、自由来流温度之间呈一定的函数关系。

关键词：气动加热湍流超声速流动数值模拟

基于行程时间阈的城轨乘客乘车方案多维匹配推定模型

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同济大学学报（自然科学版） 2022年第1期50卷 87-95页

作者：朱炜范伟莉徐昶悦徐瑞华同济大学上海市轨道交通结构耐久与系统安全重点实验室上海201804 同济大学道路与交通工程教育部重点实验室上海201804 中铁上海设计院集团有限公司上海200070

基于城市轨道交通网络化运营过程中的自动售检票系统(AFC)票卡和列车自动监控系统(ATS)行车数据以及乘客走行时间参数数据,提取乘客乘车方案行程时间阈,分析乘客实际选择的影响因素,提出基于行程时间阈的乘客乘车方案多维匹配推定模型... 详细信息

基于城市轨道交通网络化运营过程中的自动售检票系统(AFC)票卡和列车自动监控系统(ATS)行车数据以及乘客走行时间参数数据,提取乘客乘车方案行程时间阈,分析乘客实际选择的影响因素,提出基于行程时间阈的乘客乘车方案多维匹配推定模型。该模型实现了逐位票卡乘客推定至最可能的乘客方案上,并具有较强的合理性和实用性。最后通过北京城市轨道交通网络实际案例验证了方法的可行性和有效性。

关键词：城市轨道交通乘车方案行程时间阈多维匹配推定模型