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进口雷诺数和湍流度对压气机叶栅流动特性影响
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作者 杜文海 陈珂 +2 位作者 彭旻扬 王硕琨 张燕峰 《哈尔滨工程大学学报》 EI CAS CSCD 北大核心 2024年第8期1607-1615,共9页
针对高空条件下,无人机发动机的压气机气动性能明显下降的问题,本文以某高亚声速压气机叶型V103为研究对象,采用数值模拟方法研究了3种雷诺数(Re=1.5×10^(5),4.5×10^(5),1.2×106)条件下,不同来流湍流度(Tu=1%,3%,5%,6%,7... 针对高空条件下,无人机发动机的压气机气动性能明显下降的问题,本文以某高亚声速压气机叶型V103为研究对象,采用数值模拟方法研究了3种雷诺数(Re=1.5×10^(5),4.5×10^(5),1.2×106)条件下,不同来流湍流度(Tu=1%,3%,5%,6%,7.5%,10%)对压气机叶栅内部流动特性的影响,分析了流动分离和转捩之间的变化关系,以及由此引起的叶型损失变化规律。研究结果表明:当湍流度不变时,随着雷诺数减小,分离泡长度增加,但分离点位置不变;当雷诺数不变,湍流度减小,层流分离点位置会提前,并且前移现象在低雷诺数下更明显;当湍流度增加,叶片表面分离泡消失,但损失仍然呈现出随着湍流度增加而增大的趋势;在不同雷诺数条件下,都存在一个对应于最小叶型损失的来流湍流度,且该湍流度随着雷诺数的减小而略有增大。本文为修正低雷诺数条件下压气机叶型损失模型和发展预测压气机高空低雷诺数效应的数值模型提供理论指导。 展开更多
关键词 低雷诺数 进口湍流度 流动分离 边界层分离 转捩 叶型损失 数值模拟 压气机叶栅 表面边界层
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NONLINEAR EFFECT OF LOCAL ROUGH WALL ON LARGE EDDY STRUCTURE IN BOUNDARY LAYER
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作者 陆昌根 曹卫东 张艳梅 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2008年第3期194-200,共7页
Based on the building of a theoretical model for the large eddy structure, the nonlinear effect of the local rough wall on the large eddy structure in the boundary layer is studied by direct numerical simulation. Nume... Based on the building of a theoretical model for the large eddy structure, the nonlinear effect of the local rough wall on the large eddy structure in the boundary layer is studied by direct numerical simulation. Numerical results show that factors of the local rough feature, the distributing structure and the intensity, etc. play an important role in the evolution of the large eddy structure in the boundary layer. 展开更多
关键词 surface roughness boundary layers large eddy structure
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NONLINEAR EVOLUTION OF TWO-DIMENSIONAL T-S WAVE IN LOCALIZED ROUGH BOUNDARY LAYER
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作者 陆昌根 吴卫国 戚琴娟 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2009年第3期192-198,共7页
Numerical simulations are carried out to investigate the mechanism of the nonlinear evolution of two- dimensional (2-D) Tollmien-Schlichting (T-S) wave on a localized rough boundary layer. The three-dimensional (... Numerical simulations are carried out to investigate the mechanism of the nonlinear evolution of two- dimensional (2-D) Tollmien-Schlichting (T-S) wave on a localized rough boundary layer. The three-dimensional (3-D) numerical solution of a base flow on a boundary layer is obtained for the localized rough wall with the local- ized ejection, the localized suction and the combination of ejection and suction. Based on numerical simulations, the processes of stable and the most instable nonlinear evolution of the 2-D disturbance T-S wave are studied. The effects of the form on the localized roughness, the intensity, and the distribution structure on the nonlinear evolution of 2-D T-S wave and the growth rate are discussed. Results show that the basic flow induced by the lo- calized rough wall is a key factor causing the fast growth of the disturbance wave. Due to the change of the aver- age flow profile and the existence of the spanwise velocity, the localized rough wall enhances the instability of the flow. Consequently, the instable region of the neutral curve is enlargened, and the maximnum growth rate of the 2-D T-S wave is increased. In the process of the nonlinear evolution of 2-D disturbance T-S wave, with the in- crease of the nonlinear interaction, the most instable 2-D disturbance wave triggers the appearance of the 3-D dis- turbance wave and the high-frequency harmonic wave. Its streamwise wave number and the frequency are the same as those of 2-D disturbance wave. The spanwise velocity can excite the growth of the 2-D disturbance wave, the instability of 2-D wave, the formation of the streamwise vortex, and the generation of 3-D disturbance wave. Simulation results agree well with experimental results. 展开更多
关键词 surface roughness boundary layers 2-D T-S wave
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黄海冬季雾与夏季雾个例的对比研究 被引量:1
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作者 王绪翔 刘锦超 李杨 《气象研究与应用》 2022年第1期96-100,共5页
使用具有较高分辨率的NCEP格点数据对2008年7月8-11日和2010年2月22-25日发生在黄海海区的两次海雾过程的环流形势和特征参量进行了对比研究,以探讨黄海海区冬季雾与夏季雾产生机制的异同。结果表明,这两次海雾过程都是发生在稳定层结... 使用具有较高分辨率的NCEP格点数据对2008年7月8-11日和2010年2月22-25日发生在黄海海区的两次海雾过程的环流形势和特征参量进行了对比研究,以探讨黄海海区冬季雾与夏季雾产生机制的异同。结果表明,这两次海雾过程都是发生在稳定层结下的低压前部、高压后部型的平流冷却雾。海雾发生时表面行星边界层有抬升,海雾消散时表面行星边界层降低。冬季雾逆温层先减弱消失,然后海雾消散,与冬季雾相反,夏季雾是海雾先消散,然后逆温层消失,逆温层演变特征为该海域海雾的监测和定量预报提供参考。 展开更多
关键词 海雾 表面行星边界层 逆温层
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Construction of Wave-free Potentials and Multipoles in a Two-layer Fluid Having Free-surface Boundary Condition with Higher-order Derivatives 被引量:1
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作者 Dilip Das 《Journal of Marine Science and Application》 CSCD 2015年第3期270-282,共13页
There is a large class of problems in the field of fluid structure interaction where higher-order boundary conditions arise for a second-order partial differential equation. Various methods are being used to tackle th... There is a large class of problems in the field of fluid structure interaction where higher-order boundary conditions arise for a second-order partial differential equation. Various methods are being used to tackle these kind of mixed boundary-value problems associated with the Laplace’s equation (or Helmholtz equation) arising in the study of waves propagating through solids or fluids. One of the widely used methods in wave structure interaction is the multipole expansion method. This expansion involves a general combination of a regular wave, a wave source, a wave dipole and a regular wave-free part. The wave-free part can be further expanded in terms of wave-free multipoles which are termed as wave-free potentials. These are singular solutions of Laplace’s equation or two-dimensional Helmholz equation. Construction of these wave-free potentials and multipoles are presented here in a systematic manner for a number of situations such as two-dimensional non-oblique and oblique waves, three dimensional waves in two-layer fluid with free surface condition with higher order partial derivative are considered. In particular, these are obtained taking into account of the effect of the presence of surface tension at the free surface and also in the presence of an ice-cover modelled as a thin elastic plate. Also for limiting case, it can be shown that the multipoles and wave-free potential functions go over to the single layer multipoles and wave-free potential. 展开更多
关键词 two-layer fluid wave-free potentials Laplace’s equation modified Helmholtz equations higher order boundary conditions MULTIPOLES
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Studies of stability of blade cascade suction surface boundary layer
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作者 董学智 颜培刚 韩万金 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2007年第2期189-192,共4页
Compressible boundary layers stability on blade cascade suction surface was discussed by wind tunnel experiment and numerical solution. Three dimensional disturbance wave Parabolized Stability Equations (PSE) of ortho... Compressible boundary layers stability on blade cascade suction surface was discussed by wind tunnel experiment and numerical solution. Three dimensional disturbance wave Parabolized Stability Equations (PSE) of orthogonal Curvilinear Coordinates in compressible flow was deducted. The surface pressure of blade in wind tunnel experiment was measured. The Falkner-Skan equation was solved under the boundary conditions of experiment result, and velocity, pressure and temperature of average flow were obtained. Substituted this result for discretization of the PSE Eigenvalue Problem, the stability problem can be solved. 展开更多
关键词 wind tunnel experiment turbine blade cascade boundary layer stability PSE equation
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Large excavations and their effect on displacement of land boundaries 被引量:1
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作者 Jan Nemcik Naj Aziz 《International Journal of Mining Science and Technology》 SCIE EI 2012年第5期633-637,共5页
A study to estimate land surface movement caused by large surface excavations in sedimentary strata is presented.In stratified or jointed strata the stress relief driven movement adjacent to large excavations can be s... A study to estimate land surface movement caused by large surface excavations in sedimentary strata is presented.In stratified or jointed strata the stress relief driven movement adjacent to large excavations can be significantly larger than expected.High lateral stresses measured in Australia and other places around the world indicate that the ratio of horizontal to vertical stress has been particularly high at shallow depths.The in situ strata is in compression and during excavation,stress is relieved towards the opening causing strata movement.Large excavations such as,open cut mines or highway cuttings,can initiate an extensive horizontal slide of surface layers towards the excavation.These ground movements can be damaging to surface structures such as water storage dams and large buildings.Based on stress measurements at shallow depths in Australian coal mines the study presented here calculates and models the extent of potential ground movement along the bedding surface adjacent to large excavations and provides a new prediction tool of land movement at the excavation boundary that can benefit the geotechnical practitioners in the mining industry. 展开更多
关键词 Stress measurements High lateral stress Lateral stress relief Lateral displacement of bedded strata Stability of large excavations
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NO_x Release from Snow and Ice Covered Surface in Polar Regions and the Tibetan Plateau
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作者 Feng Wang Weili Lin +1 位作者 Junxia Wang Tong Zhu 《Advances in Climate Change Research》 SCIE 2011年第3期141-148,共8页
The exchanges of NOx between snow and air have significant impact on the atmospheric components and photochemical processes in the overlying boundary layer. Such exchanges increase the oxidizing capacity of the atmosp... The exchanges of NOx between snow and air have significant impact on the atmospheric components and photochemical processes in the overlying boundary layer. Such exchanges increase the oxidizing capacity of the atmosphere and may have a crucial impact on the air signals that are retrieved from ice cores. In the recent years, sunlit snow and ice have been demonstrated to be important NOx sources in the polar atmospheric boundary layer. This paper makes a thorough review on the release of NOx from snow and ice, including field observations and experimental evidences, release mechanisms and influential parameters that affect such a release process, polar NOx concentrations and fluxes, and environmental impacts of the chemical processes of NOx in the polar atmospheric boundary layer. In the Tibetan Plateau, the released NOx observed recently in the sunlit snow/ice-cover is 1-order magnitude more than that in polar regions, but further scientific research is still needed to reveal its impact on the atmospheric oxidizing capacity. 展开更多
关键词 NOx exchange between snow and air polar area atmospheric oxidizing capacity Tibetan Plateau
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Computational Investigation of Blade slotting on a High-Load Low-Pressure Turbine Profile at various Reynolds Numbers:Part Ⅰ——Slotting Scheme's Verification 被引量:3
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作者 Qiang Du Junqiang Zhu +1 位作者 Min Zhou Wei Li 《Journal of Thermal Science》 SCIE EI CAS CSCD 2011年第1期13-20,共8页
Boundary layer separation and reattachment is often an unavoidable feature of low pressure (LP) turbine,one of the main causes of this phenomenon is the high altitude low Reynolds number experienced by the modern LP t... Boundary layer separation and reattachment is often an unavoidable feature of low pressure (LP) turbine,one of the main causes of this phenomenon is the high altitude low Reynolds number experienced by the modern LP turbine stage in aero-engine.Although an excellent turbine airfoil design can avoid flow separation on certain extent,but within flight envelope,LP turbine's characteristic Reynolds number may varied greatly,so it will be still under the risk of the presence of separation bubble.In this two parts paper a new concept of slotted-blade was raised to testify the gain of the blade slotting.A high aerodynamic loading LP turbine blade IET-LPTA was under investigated with different Reynolds number.Computational results reveal that the blade slotting could be a way of choice to suppress separation bubble and reduce profile loss under the condition of low Reynolds number,although its position and geometry need to be further investigated. 展开更多
关键词 Boundary layer separation and reattachment High aerodynamic loading LP turbine blade Slotted-blade
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Experimental Study of Turbulent Boundary Layers on Groove/Smooth Flat Surfaces 被引量:3
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作者 Hongwei MA Qiao TIAN Hui WU 《Journal of Thermal Science》 SCIE EI CAS CSCD 2005年第3期193-197,共5页
This paper presents an experimental investigation of the turbulent boundary layers on both groove and smooth flat surfaces. The flow structures were shown in a water tunnel using the hydrogen-bubble flow visualization... This paper presents an experimental investigation of the turbulent boundary layers on both groove and smooth flat surfaces. The flow structures were shown in a water tunnel using the hydrogen-bubble flow visualization technique. The measurement results indicate that: (1) the grooves can effectively reduce accumulation of low-speed fluids, decrease the number of the low-speed streaks and depress oscillation of the streaks in the sublayer; (2) the grooves can restrain forming of the horseshoe vortices in the buffer region; (3) the grooves bate oscillation and kinking of the quasi-streamwise vortices and restrain production of the hairpin vortices and the ring vortices, reducing both frequency and intensity of the turbulence bursting; (4) the grooves directly affect the flow structures in the sublayer of the boundary layer and then modulate the flow field up to the buffer region and the logarithmic region by restraining development and interaction of the vortices. 展开更多
关键词 streamwise groove turbulent boundary layer drag reduction mechanism coherent structure hydrogen-bubble flow visualization
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Estimation of key surface parameters in semi-arid region and their impacts on improvement of surface fluxes simulation 被引量:1
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作者 LIU Ye GUO WeiDong SONG YaoMing 《Science China Earth Sciences》 SCIE EI CAS CSCD 2016年第2期307-319,共13页
Uncertainties in some key parameters in land surface models severely restrict the improvement of model capacity for successful simulation of surface-atmosphere interaction. These key parameters are related to soil moi... Uncertainties in some key parameters in land surface models severely restrict the improvement of model capacity for successful simulation of surface-atmosphere interaction. These key parameters are related to soil moisture and heat transfer and phy- sical processes in the vegetation canopy as well as other important aerodynamic processes. In the present study, measurements of surface-atmosphere interaction at two observation stations that are located in the typical semi-arid region of China, Tongyu Station in Jilin Province and Yuzhong Station in Gansu Province, are combined with the planetary boundary layer theory to estimate the value of two key aerodynamic parameters, i.e., surface roughness length zorn and excess resistance κB-1. Multiple parameterization schemes have been used in the study to obtain values for surface roughness length and excess resistance κB-1 at the two stations. Results indicate that Zorn has distinct seasonal and inter-annual variability. For the type of surface with low-height vegetation, there is a large difference between the default value of Zorn in the land surface model and that obtained from this study, κB-1 demonstrates a significant diurnal variation and seasonal variability. Using the modified scheme for the estimation of Zom and κB-1 in the land surface model, it is found that simulations of sensible heat flux over the semi-arid region have been greatly improved. These results suggest that it is necessary to further evaluate the default values of various parameters used in land surface models based on field measurements. The approach to combine field measurements with atmospheric boundary layer theory to retrieve realistic values for key parameters in land surface models presents a great potential in the improvement of modeling studies of surface-atmosphere interaction. 展开更多
关键词 Semi-arid region Turbulent transfer Surface roughness length Excess resistance Field experiments
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Relationship of atmospheric boundary layer depth with thermodynamic processes at the land surface in arid regions of China 被引量:30
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作者 ZHANG Qiang ZHANG Jie +1 位作者 QIAO Juan WANG Sheng 《Science China Earth Sciences》 SCIE EI CAS 2011年第10期1586-1594,共9页
The atmospheric boundary layer (ABL) is an important physical characteristic of the Earth's atmosphere. Compared with the typical ABL, the ABL in arid regions has distinct features and is formed by particular mecha... The atmospheric boundary layer (ABL) is an important physical characteristic of the Earth's atmosphere. Compared with the typical ABL, the ABL in arid regions has distinct features and is formed by particular mechanisms. In this paper, the depth of the diurnal and nocturnal ABLs and their related thermodynamic features of land surface processes, including net radiation, the ground-air temperature difference and sensible heat flux, under typical summer and winter conditions are discussed on the basis of comprehensive observations of the ABL and thermodynamic processes at the land surface carried out in the extreme arid zone of Dunhuang. The relationships of the ABL depth in the development and maintenance stages with these thermodynamic features are also investigated. The results show that the depth of the ABL is closely correlated with the thermodynamic features in both development and maintenance stages and more energy is consumed in the development stage. Further analysis indicates that wind velocity also affects ABL development, especially the development of a stable boundary layer in winter. Taken together, the analysis results indicate that extremely strong thermodynamic processes at the land surface are the main driving factor for the formation of a deep ABL in an arid region. 展开更多
关键词 arid region deep atmospheric boundary layer development and maintenance thermodynamic process at the land surface main driving factor
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Group Theory Analysis of Free Convective BoundaryLayer Behavior at a Stretching Surface
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作者 Junmei Shi Xuezi Xu +1 位作者 Jianren Fan Kefa Cen (Department of Energy Engineering, +Department of Mechanics, Zhejiang University, Hangzhou, 310027,China) 《Journal of Thermal Science》 SCIE EI CAS CSCD 1995年第4期229-235,共7页
In the Present study, free convection and heat transfer behavior of electrically conducting fluid in the boundary layer over a vertical continuously stretching surface is investigated. The effects of free convection, ... In the Present study, free convection and heat transfer behavior of electrically conducting fluid in the boundary layer over a vertical continuously stretching surface is investigated. The effects of free convection, magnetic field, suction/blowing at the surface and the stretching speed of the surface on the flow and heat transfer characteristics are considered. By applying one-parametric group theory to analysis of the problem, a similarity solution is found. The governing equations of continuity, momentum and energy are solved numerically by a fourth-order Runge-Kutta scheme. The numerical results, which are obtained for the flow and heat transfer characteristics, reveal the influences of the parameters. 展开更多
关键词 group theory stretching surface free convection.
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Numerical simulation of gurney flaps lift-enhancement on a low reynolds number airfoil 被引量:4
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作者 HE Xi WANG JinJun +3 位作者 YANG MuQing MA DongLi YAN Chao LIU PeiQing 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2017年第10期1548-1559,共12页
Two-dimensional steady Reynolds-averaged Navier-Stokes (RANS) equations with transition shear stress transport (SST) model were solved to investigate the effects of Gumey flaps on the aerodynamic performance of a ... Two-dimensional steady Reynolds-averaged Navier-Stokes (RANS) equations with transition shear stress transport (SST) model were solved to investigate the effects of Gumey flaps on the aerodynamic performance of a low Reynolds number airfoil. This airfoil was designed for flight vehicles operating at 20 km altitude with freestream velocity of 25 rn/s. The chord length (C) of this airfoil is 5 m and the corresponding Reynolds number is 7.76× 10^5. Gurney flaps with the heights ranging from 0.25%C to 3%C were investigated. It has been shown that Gurney flaps can enhance not only the prestall lift but also lift-to-drag ratio in a certain range of angles of attack. Specially, at cruise angle of attack (3°), Gurney flap with the height of 0.5%C can increase lift-to-drag ratio and lift coefficient by 1.6% and 12.8%, respectively. Furthermore, the mechanisms of Gumey flaps to improve the aerodynamic performance were illustrated by analyzing the surface pressure distribution, streamlines and trailing-edge flow structure for this low Reynolds number airfoil. Specially, distinguished from some other numerical researches, the flow details such as the laminar separation bubble and transition phenomena for low Reynolds number airfoil with Gumey flaps were investigated and it was found that Gurney flaps can delay the transition onset position at small angles of attack (≤2°). However, with the increase of angles of attack, Gurney flaps will promote the boundary layer transition. 展开更多
关键词 gurney flaps lift-enhancement low reynolds number numerical simulation
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Massive heat transfer enhancement of Rayleigh-Benard turbulence over rough surfaces and under horizontal vibration
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作者 Jian-Zhao Wu Bo-Fu Wang Quan Zhou 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2022年第2期60-67,I0002,共9页
We carried out direct numerical simulations of turbulent Rayleigh-Benard convection(RBC)with accounting for both the roughness and the external vibration over the Rayleigh number range 10^(7)≤Ra≤10^(11) and the vibr... We carried out direct numerical simulations of turbulent Rayleigh-Benard convection(RBC)with accounting for both the roughness and the external vibration over the Rayleigh number range 10^(7)≤Ra≤10^(11) and the vibration frequency range 0<ω<1400.The triangular rough elements are uniformly distributed over the top and bottom surfaces,and the vibration is applied in the horizontal direction.It is shown that under the combined action of roughness and horizontal vibration,with increasing the vibration frequency ω,the heat transfer is initially decreased a little and then greatly enhanced after ω exceeds the critical value.The physical reason for massive heat-transfer-enhancement is that high frequency vibration destabilizes thermal boundary layers(BL)over rough surfaces,triggers abundant emissions of thermal plumes,and strengthens the motion of large-scale circulation(LSC),which consequently thins the thickness of thermal BL and heightens the convective transport.In addition,it is shown that vibration-induced heat-transfer-enhancement can obviously affect the scaling behavior between the heat flux and the Rayleigh number,and the scaling exponent increases with increasing ω,whereas the influence of vibration on the scaling behavior between the intensity of LSC and Ra is very weak. 展开更多
关键词 Rayleigh-Benard convection Rough surface VIBRATION Heat transfer enhancement
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Experimental Investigation of Dimensionless Velocity and Shearing Stress in Boundary Layer Flow on Continuous Moving Surface in Power Law Fluids 被引量:1
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作者 Hao Zhang Xinxin Zhang +2 位作者 Liancun Zheng Weiliang Wang Yuancheng Wang 《Journal of Thermal Science》 SCIE EI CAS CSCD 2011年第2期115-118,共4页
An analysis is carried out to study the steady flow characteristics from a continuous flat surface moving in a parallel free stream of non-Newtonian power law fluid. The constitutive equations of the fluid are transfo... An analysis is carried out to study the steady flow characteristics from a continuous flat surface moving in a parallel free stream of non-Newtonian power law fluid. The constitutive equations of the fluid are transformed into dimensionless ones. The velocity field is measured by Particle Image Velocimetry. Experimental results are obtained for the distribution of velocity. The influence of wall velocity ratio parameter on boundary layer flow field is observed in the experiment. Dimensionless velocity distribution and shearing stress distribution are obtained by post-processing experimental results. The effects of various physical parameters like velocity ratio parameter and similarity variable on various momentum transfer characteristics are discussed in detail and shown graphically. It is indicated that dimensionless velocity increases with velocity ratio parameter and similarity variable, and that dimensionless shearing stress decreases with velocity ratio parameter and similarity variable. 展开更多
关键词 Boundary layer Power law fluid PIV Experiment Dimensionless transformation
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Effects of the superhydrophobic surface on coherent structures in the turbulent boundary layer 被引量:1
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作者 Yu-Fei Wang Xin-Wei Wang +2 位作者 Xing-Yu Ma Zhan-Qi Tang Nan Jiang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2022年第10期66-79,共14页
The influence of drag-reducing superhydrophobic(SHPo)surface on turbulent boundary layer(TBL)is investigated.A large area of the SHPo surface(about 10δ99 in the streamwise and 5δ99 in the spanwise)is fabricated to f... The influence of drag-reducing superhydrophobic(SHPo)surface on turbulent boundary layer(TBL)is investigated.A large area of the SHPo surface(about 10δ99 in the streamwise and 5δ99 in the spanwise)is fabricated to fully evolve the coherent structures in the TBL.A comparative experiment is carried out by time-resolved particle image velocimetry on a smooth surface and the SHPo surface at Re_(τ)=528.Velocity profiles with high spatial resolution are obtained by the single-pixel resolution ensemble correlation method.The reduction of the streamwise velocity gradient is observed in the near-wall region of y<0.05δ99 on the SHPo surface.By comparing the turbulence statistics,it is discovered that the Reynolds shear stress is reduced by 15.7%,and the turbulent kinetic energy is reduced by 12.3%on the SHPo surface.The coherent structures are investigated by the snapshot proper orthogonal decomposition(POD)and conditional average method.The intensity of Q_(2)/Q_(4)events on the SHPo surface has declined by 16.1%and 12.7%,respectively.The number of clockwise spanwise vortices is substantially reduced by 47%.Through spatial two-point correlation analysis,the streamwise and wall-normal direction scales of the coherent structures on the SHPo surface are suppressed. 展开更多
关键词 SUPERHYDROPHOBIC TURBULENCE Coherent structure
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Implementation of a Roughness Element to Trip Transition in Large-eddy Simulation 被引量:2
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作者 J.Boudet J.-F.Monier F.Gao 《Journal of Thermal Science》 SCIE EI CAS CSCD 2015年第1期30-36,共7页
In aerodynamics, the laminar or turbulent regime of a boundary layer has a strong influence on friction or heat transfer. In practical applications, it is sometimes necessary to trip the transition to turbulent, and a... In aerodynamics, the laminar or turbulent regime of a boundary layer has a strong influence on friction or heat transfer. In practical applications, it is sometimes necessary to trip the transition to turbulent, and a common way is by use of a roughness element (e.g. a step) on the wall. The present paper is concerned with the numerical im- plementation of such a trip in large-eddy simulations. The study is carried out on a flat-plate boundary layer con- figuration, with Reynolds number Rex=l.3x 106. First, this work brings the opportunity to introduce a practical methodology to assess convergence in large-eddy simulations. Second, concerning the trip implementation, a volume source term is proposed and is shown to yield a smoother and faster transition than a grid step. Moreover, it is easier to implement and more adaptable. Finally, two subgrid-scale models are tested: the WALE model of Nic0ud and Ducros (Flow Turbul. Combust., vol. 62, 1999) and the shear-improved Smagorinsky model of Ldv^que et al. (J. Fluid Mech., vol. 570, 2007). Both models allow transition, but the former appears to yield a faster transition and a better prediction of friction in the turbulent regime. 展开更多
关键词 large-eddy simulation boundary layer roughness element TRANSITION TRIPPING
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Skin Friction Gage for Measurements in Hypersonic Flow
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作者 Francois Falempin Marat Goldfeld Roman Nestoulia 《Journal of Thermal Science》 SCIE EI CAS CSCD 2003年第1期44-50,共7页
A description and results of tests of a new small-scale gage for direct measurement of skin friction force are presented in the paper.The gage design provides separated measurement of longitudinal and transversal comp... A description and results of tests of a new small-scale gage for direct measurement of skin friction force are presented in the paper.The gage design provides separated measurement of longitudinal and transversal component of friction force.Application of this scheme provides high sensitivity and necessary high-frequency response of the gage.The tests of the gage were carried out in a blow down wind tunnel at Mach numbers of 2 and 4 within the range of Reynolds numbers Rex from 0.8 to 5 million and in the hot-shot wind tunnel at Mach number 6 and Reynolds numbers Rex=2.5-10 million.The measurements of skin friction were carried out on a flat plate and on a ramp beyond the shock wave.Simultaneously with the direct measurement of friction in the blow down wind tunnel,the measurements of profiles of average velocities and mass flow rate pulsations were realised.Analysis of measurement errors has shown that the friction gage permits to measure skin friction coefficient on a flat plate with mistake not more than 10%. 展开更多
关键词 skin friction gage hypersonic flow scramjet.
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